Document ID: EPA-HQ-OAR-2019-0055-2894
Agency: epa
Document Type: Rule
Title: Heavy-Duty Engine and Vehicle Standards: Control of Air Pollution from New Motor Vehicles
Posted Date: 2023-01-24T05:00Z

[Federal Register Volume 88, Number 15 (Tuesday, January 24, 2023)]
[Rules and Regulations]
[Pages 4296-4718]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-27957]

[[Page 4295]]

Vol. 88

Tuesday,

No. 15

January 24, 2023

Part II

Environmental Protection Agency

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40 CFR Parts 2, 59, 60, et al.

Control of Air Pollution From New Motor Vehicles: Heavy-Duty Engine and 
Vehicle Standards; Final Rule

  Federal Register / Vol. 88 , No. 15 / Tuesday, January 24, 2023 / 
Rules and Regulations  

[[Page 4296]]

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 2, 59, 60, 80, 85, 86, 600, 1027, 1030, 1031, 1033, 
1036, 1037, 1039, 1042, 1043, 1045, 1048, 1051, 1054, 1060, 1065, 
1066, 1068, and 1090

[EPA-HQ-OAR-2019-0055; FRL-7165-02-OAR]
RIN 2060-AU41

Control of Air Pollution From New Motor Vehicles: Heavy-Duty 
Engine and Vehicle Standards

AGENCY: Environmental Protection Agency (EPA).

ACTION: Final rule.

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SUMMARY: The Environmental Protection Agency (EPA) is finalizing a 
program to further reduce air pollution, including ozone and 
particulate matter (PM), from heavy-duty engines and vehicles across 
the United States. The final program includes new emission standards 
that are significantly more stringent and that cover a wider range of 
heavy-duty engine operating conditions compared to today's standards; 
further, the final program requires these more stringent emissions 
standards to be met for a longer period of when these engines operate 
on the road. Heavy-duty vehicles and engines are important contributors 
to concentrations of ozone and particulate matter and their resulting 
threat to public health, which includes premature death, respiratory 
illness (including childhood asthma), cardiovascular problems, and 
other adverse health impacts. The final rulemaking promulgates new 
numeric standards and changes key provisions of the existing heavy-duty 
emission control program, including the test procedures, regulatory 
useful life, emission-related warranty, and other requirements. 
Together, the provisions in the final rule will further reduce the air 
quality impacts of heavy-duty engines across a range of operating 
conditions and over a longer period of the operational life of heavy-
duty engines. The requirements in the final rule will lower emissions 
of NOX and other air pollutants (PM, hydrocarbons (HC), 
carbon monoxide (CO), and air toxics) beginning no later than model 
year 2027. We are also finalizing limited amendments to the regulations 
that implement our air pollutant emission standards for other sectors 
(e.g., light-duty vehicles, marine diesel engines, locomotives, and 
various other types of nonroad engines, vehicles, and equipment).

DATES: This final rule is effective on March 27, 2023. The 
incorporation by reference of certain material listed in this rule is 
approved by the Director of the Federal Register as of March 27, 2023.

ADDRESSES: Docket: EPA has established a docket for this action under 
Docket ID No. EPA-HQ-OAR-2019-0055. Publicly available docket materials 
are available either electronically at www.regulations.gov or in hard 
copy at Air and Radiation Docket and Information Center, EPA Docket 
Center, EPA/DC, EPA WJC West Building, 1301 Constitution Ave., NW, Room 
3334, Washington, DC. Out of an abundance of caution for members of the 
public and our staff, the EPA Docket Center and Reading Room are open 
to the public by appointment only to reduce the risk of transmitting 
COVID-19. Our Docket Center staff also continues to provide remote 
customer service via email, phone, and webform. Hand deliveries and 
couriers may be received by scheduled appointment only. For further 
information on EPA Docket Center services and the current status, 
please visit us online at www.epa.gov/dockets.

FOR FURTHER INFORMATION CONTACT: Brian Nelson, Assessment and Standards 
Division, Office of Transportation and Air Quality, Environmental 
Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 
telephone number: (734) 214-4278; email address: [email protected].

SUPPLEMENTARY INFORMATION: 

Does this action apply to me?

    This action relates to companies that manufacture, sell, or import 
into the United States new heavy-duty highway engines. Additional 
amendments apply for gasoline refueling facilities and for 
manufacturers of all sizes and types of motor vehicles, stationary 
engines, aircraft and aircraft engines, and various types of nonroad 
engines, vehicles, and equipment. Regulated categories and entities 
include the following:

------------------------------------------------------------------------
           NAICS codes \a\                        NAICS title
------------------------------------------------------------------------
326199..............................  All Other Plastics Product
                                       Manufacturing.
332431..............................  Metal Can Manufacturing.
333618..............................  Manufacturers of new marine diesel
                                       engines.
335312..............................  Motor and Generator Manufacturing.
336111..............................  Automobile Manufacturing.
336112..............................  Light Truck and Utility Vehicle
                                       Manufacturing.
336120..............................  Heavy Duty Truck Manufacturing.
336211..............................  Motor Vehicle Body Manufacturing.
336213..............................  Motor Home Manufacturing.
336411..............................  Manufacturers of new aircraft.
336412..............................  Manufacturers of new aircraft
                                       engines.
333618..............................  Other Engine Equipment
                                       Manufacturing.
336999..............................  All Other Transportation Equipment
                                       Manufacturing.
423110..............................  Automotive and Other Motor Vehicle
                                       Merchant Wholesalers.
447110..............................  Gasoline Stations with Convenience
                                       Stores.
447190..............................  Other Gasoline Stations.
454310..............................  Fuel dealers.
811111..............................  General Automotive Repair.
811112..............................  Automotive Exhaust System Repair.
811198..............................  All Other Automotive Repair and
                                       Maintenance.
------------------------------------------------------------------------
\a\ NAICS Association. NAICS & SIC Identification Tools. Available
  online: https://www.naics.com/search.

    This table is not intended to be exhaustive, but rather provides a 
guide for readers regarding entities likely to be regulated by this 
action. This table lists the types of entities that EPA is now aware 
could potentially be regulated by this action. Other types of entities 
not listed in the table could also be regulated. To determine whether 
your entity is regulated by this action, you should carefully examine 
the applicability criteria found in Sections XI and XII of this 
preamble. If you have questions regarding the applicability of this 
action to a particular entity, consult the person listed in the FOR 
FURTHER INFORMATION CONTACT section.
    Public participation: Docket: All documents in the docket are 
listed on the www.regulations.gov website. Although listed in the 
index, some information is not publicly available, e.g., CBI or other 
information whose disclosure is restricted by statute. Certain other 
material, such as copyrighted material, is not placed on the internet 
and will be publicly available only in hard copy form through the EPA 
Docket Center at the location listed in the ADDRESSES section of this 
document.

What action is the agency taking?

    The Environmental Protection Agency (EPA) is adopting a rule to 
reduce air pollution from highway heavy-duty vehicles and engines. The 
final rulemaking will promulgate new numeric standards and change key 
provisions of the existing heavy-duty emission control program, 
including the

[[Page 4297]]

test procedures, regulatory useful life, emission-related warranty, and 
other requirements. Together, the provisions in the final rule will 
further reduce the air quality impacts of heavy-duty engines across a 
range of operating conditions and over a longer period of the 
operational life of heavy-duty engines. Heavy-duty vehicles and engines 
are important contributors to concentrations of ozone and particulate 
matter and their resulting threat to public health, which includes 
premature death, respiratory illness (including childhood asthma), 
cardiovascular problems, and other adverse health impacts. This final 
rule will reduce emissions of nitrogen oxides and other pollutants.

What is the agency's authority for taking this action?

    Clean Air Act section 202(a)(1) requires that EPA set emission 
standards for air pollutants from new motor vehicles or new motor 
vehicle engines that the Administrator has found cause or contribute to 
air pollution that may endanger public health or welfare. See Sections 
I.D and XIII of this preamble for more information on the agency's 
authority for this action.

What are the incremental costs and benefits of this action?

    Our analysis of the final standards shows that annual total costs 
for the final program relative to the baseline (or no action scenario) 
range from $3.9 billion in 2027 to $4.7 billion in 2045 (2017 dollars, 
undiscounted, see Table V-16). The present value of program costs for 
the final rule, and additional details are presented in Section V. 
Section VIII presents our analysis of the human health benefits 
associated with the final standards. We estimate that in 2045, the 
final rule will result in total annual monetized ozone- and 
PM2.5-related benefits of $12 and $33 billion at a 3 percent 
discount rate, and $10 and $30 billion at a 7 percent discount rate 
(2017 dollars, discount rate applied to account for mortality cessation 
lag, see Table VIII-3).\1\ These benefits only reflect those associated 
with reductions in NOX emissions (a precursor to both ozone 
and secondarily-formed PM2.5) and directly-emitted 
PM2.5 from highway heavy-duty engines. The agency was unable 
to quantify or monetize all the benefits of the final program, 
therefore the monetized benefit values are underestimates. There are 
additional human health and environmental benefits associated with 
reductions in exposure to ambient concentrations of PM2.5, 
ozone, and NO2 that data, resource, or methodological 
limitations have prevented EPA from quantifying. There will also be 
benefits associated with reductions in air toxic pollutant emissions 
that result from the final program, but we did not attempt to monetize 
those impacts because of methodological limitations. More detailed 
information about the benefits analysis conducted for the final rule, 
including the present value of program benefits, is included in Section 
VIII and RIA Chapter 8. We compare total monetized health benefits to 
total costs associated with the final rule in Section IX. Our results 
show that annual benefits of the final rule will be larger than the 
annual costs in 2045, with annual net benefits of $6.9 and $29 billion 
assuming a 3 percent discount rate, and net benefits of $5.8 and $25 
billion assuming a 7 percent discount rate.\2\ The benefits of the 
final rule also outweigh the costs when expressed in present value 
terms and as equalized annual values (see Section IX for these values). 
See Section VIII for more details on the net benefit estimates
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    \1\ 2045 is a snapshot year chosen to approximate the annual 
health benefits that occur when the final program will be fully 
implemented and when most of the regulated fleet will have turned 
over.
    \2\ The range of benefits and net benefits reflects a 
combination of assumed PM2.5 and ozone mortality risk 
estimates and selected discount rate.
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Did EPA conduct a peer review before issuing this action?

    This regulatory action was supported by influential scientific 
information. EPA therefore conducted peer review in accordance with 
OMB's Final Information Quality Bulletin for Peer Review. Specifically, 
we conducted peer review on five analyses: (1) Analysis of Heavy-Duty 
Vehicle Sales Impacts Due to New Regulation (Sales Impacts), (2) 
Exhaust Emission Rates for Heavy-Duty Onroad Vehicles in MOVES_CTI NPRM 
(Emission Rates), (3) Population and Activity of Onroad Vehicles in 
MOVES_CTI NPRM (Population and Activity), (4) Cost teardowns of Heavy-
Duty Valvetrain (Valvetrain costs), and (5) Cost teardown of Emission 
Aftertreatment Systems (Aftertreatment Costs). All peer review was in 
the form of letter reviews conducted by a contractor. The peer review 
reports for each analysis are in the docket for this action and at 
EPA's Science Inventory (https://cfpub.epa.gov/si/).

Table of Contents

I. Executive Summary
    A. Introduction
    B. Overview of the Final Regulatory Action
    C. Impacts of the Standards
    D. EPA Statutory Authority for This Action
II. Need for Additional Emissions Control
    A. Background on Pollutants Impacted by This Proposal
    B. Health Effects Associated With Exposure to Pollutants 
Impacted by This Rule
    C. Environmental Effects Associated With Exposure to Pollutants 
Impacted by This Rule
    D. Environmental Justice
III. Test Procedures and Standards
    A. Overview
    B. Summary of Compression-Ignition Exhaust Emission Standards 
and Duty Cycle Test Procedures
    C. Summary of Compression-Ignition Off-Cycle Standards and Off-
Cycle Test Procedures
    D. Summary of Spark-Ignition HDE Exhaust Emission Standards and 
Test Procedures
    E. Summary of Spark-Ignition HDV Refueling Emission Standards 
and Test Procedures
IV. Compliance Provisions and Flexibilities
    A. Regulatory Useful Life
    B. Ensuring Long-Term In-Use Emissions Performance
    C. Onboard Diagnostics
    D. Inducements
    E. Fuel Quality
    F. Durability Testing
    G. Averaging, Banking, and Trading
V. Program Costs
    A. Technology Package Costs
    B. Operating Costs
    C. Program Costs
VI. Estimated Emissions Reductions From the Final Program
    A. Emission Inventory Methodology
    B. Estimated Emission Reductions From the Final Program
    C. Estimated Emission Reductions by Engine Operations and 
Processes
VII. Air Quality Impacts of the Final Rule
    A. Ozone
    B. Particulate Matter
    C. Nitrogen Dioxide
    D. Carbon Monoxide
    E. Air Toxics
    F. Visibility
    G. Nitrogen Deposition
    H. Demographic Analysis of Air Quality
VIII. Benefits of the Heavy-Duty Engine and Vehicle Standards
IX. Comparison of Benefits and Costs
    A. Methods
    B. Results
X. Economic Impact Analysis
    A. Impact on Vehicle Sales, Mode Shift, and Fleet Turnover
    B. Employment Impacts
XI. Other Amendments
    A. General Compliance Provisions (40 CFR Part 1068) and Other 
Cross-Sector Issues
    B. Heavy-Duty Highway Engine and Vehicle Emission Standards (40 
CFR Parts 1036 and 1037)
    C. Fuel Dispensing Rates for Heavy-Duty Vehicles (40 CFR Parts 
80 and 1090)
    D. Refueling Interface for Motor Vehicles (40 CFR Parts 80 and 
1090)
    E. Light-Duty Motor Vehicles (40 CFR Parts 85, 86, and 600)
    F. Large Nonroad Spark-Ignition Engines (40 CFR Part 1048)

[[Page 4298]]

    G. Small Nonroad Spark-Ignition Engines (40 CFR Part 1054)
    H. Recreational Vehicles and Nonroad Evaporative Emissions (40 
CFR Parts 1051 and 1060)
    I. Marine Diesel Engines (40 CFR Parts 1042 and 1043)
    J. Locomotives (40 CFR Part 1033)
    K. Stationary Compression-Ignition Engines (40 CFR Part 60, 
subpart IIII)
    L. Nonroad Compression-Ignition Engines (40 CFR Part 1039)
XII. Statutory and Executive Order Reviews
    A. Executive Order 12866: Regulatory Planning and Review and 
Executive Order 13563: Improving Regulation and Regulatory Review
    B. Paperwork Reduction Act (PRA)
    C. Regulatory Flexibility Act (RFA)
    D. Unfunded Mandates Reform Act (UMRA)
    E. Executive Order 13132: Federalism
    F. Executive Order 13175: Consultation and Coordination With 
Indian Tribal Governments
    G. Executive Order 13045: Protection of Children From 
Environmental Health and Safety Risks
    H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use
    I. National Technology Transfer and Advancement Act (NTTAA) and 
1 CFR Part 51
    J. Executive Order 12898: Federal Actions To Address 
Environmental Justice in Minority Populations and Low-Income 
Populations
    K. Congressional Review Act
    L. Judicial Review
XIII. Statutory Provisions and Legal Authority

I. Executive Summary

A. Introduction

1. Summary of the Final Criteria Pollutant Program
    In this action, the EPA is finalizing a program to further reduce 
air pollution, including pollutants that create ozone and particulate 
matter (PM), from heavy-duty engines and vehicles across the United 
States. The final program includes new, more stringent emissions 
standards that cover a wider range of heavy-duty engine operating 
conditions compared to today's standards, and it requires these more 
stringent emissions standards to be met for a longer period of time of 
when these engines operate on the road.
    This final rule is part of a comprehensive strategy, the ``Clean 
Trucks Plan,'' which lays out a series of clean air and climate 
regulations that the agency is developing to reduce pollution from 
large commercial heavy-duty trucks and buses, as well as to advance the 
transition to a zero-emissions transportation future. Consistent with 
President Biden's Executive Order (E.O.) 14037, this final rule is the 
first step in the Clean Trucks Plan.\3\ We expect the next two steps of 
the Clean Trucks Plan will take into consideration recent Congressional 
action, including the recent Inflation Reduction Act of 2022, that we 
anticipate will spur significant change in the heavy-duty sector.\4\ We 
are not taking final action at this time on the proposed targeted 
updates to the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 
program (HD GHG Phase 2); rather, we intend to consider potential 
changes to certain HD GHG Phase 2 standards as part of a subsequent 
rulemaking.
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    \3\ President Joseph Biden. Executive Order on Strengthening 
American Leadership in Clean Cars and Trucks. 86 FR 43583, August 
10, 2021.
    \4\ For example, both the 2021 Infrastructure Investment and 
Jobs Act (commonly referred to as the ``Bipartisan Infrastructure 
Law'' or BIL) and the Inflation Reduction Act of 2022 (``Inflation 
Reduction Act'' or IRA) include many incentives for the development, 
production, and sale of zero emissions vehicles (ZEVs) and charging 
infrastructure. Infrastructure Investment and Jobs Act, Public Law 
117-58, 135 Stat. 429 (2021) (``Bipartisan Infrastructure Law'' or 
``BIL''), available at https://www.congress.gov/117/plaws/publ58/PLAW-117publ58.pdf; Inflation Reduction Act of 2022, Public Law 117-
169, 136 Stat. 1818 (2022) (``Inflation Reduction Act'' or ``IRA''), 
available at https://www.congress.gov/117/bills/hr5376/BILLS-117hr5376enr.pdf.
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    Across the United States, heavy-duty engines emit oxides of 
nitrogen (NOX) and other pollutants that are significant 
contributors to concentrations of ozone and PM2.5 and their 
resulting adverse health effects, which include death, respiratory 
illness (including childhood asthma), and cardiovascular 
problems.5 6 7 Without this final rule, heavy-duty engines 
would continue to be one of the largest contributors to mobile source 
NOX emissions nationwide in the future, representing 32 
percent of the mobile source NOX emissions in calendar year 
2045.\8\ Furthermore, we estimate that without this final rule, heavy-
duty engines would represent 90 percent of the onroad NOX 
inventory in calendar year 2045.\9\ Reducing NOX emissions 
is a critical part of many areas' strategies to attain and maintain the 
National Ambient Air Quality Standards (NAAQS) for ozone and PM; many 
state and local agencies anticipate challenges in attaining the NAAQS, 
maintaining the NAAQS in the future, and/or preventing 
nonattainment.\10\ Some nonattainment areas have already been ``bumped 
up'' to higher classifications because of challenges in attaining the 
NAAQS.\11\
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    \5\ Oxides of nitrogen (NOX) refers to nitric oxide 
(NO) and nitrogen dioxide (NOX).
    \6\ Zawacki et al, 2018. Mobile source contributions to ambient 
ozone and particulate matter in 2025. Atmospheric Environment, Vol 
188, pg 129-141. Available online: https://doi.org/10.1016/j.atmosenv.2018.04.057.
    \7\ Davidson et al, 2020. The recent and future health burden of 
the U.S. mobile sector apportioned by source. Environmental Research 
Letters. Available online: https://doi.org/10.1088/1748-9326/ab83a8.
    \8\ Sectors other than onroad and nonroad were projected from 
2016v1 Emissions Modeling Platform. https://www.epa.gov/air-emissions-modeling/2016v1-platform.
    \9\ U.S. EPA (2020) Motor Vehicle Emission Simulator: MOVES3. 
https://www.epa.gov/moves.
    \10\ See Section II for additional detail.
    \11\ For example, in September 2019 several 2008 ozone 
nonattainment areas were reclassified from moderate to serious, 
including Dallas, Chicago, Connecticut, New York/New Jersey and 
Houston, and in January 2020, Denver. Also, on September 15, 2022, 
EPA finalized reclassification of 5 areas in nonattainment of the 
2008 ozone NAAQS from serious to severe and 22 areas in 
nonattainment of the 2015 ozone NAAQS from marginal to moderate. The 
2008 NAAQS for ozone is an 8-hour standard with a level of 0.075 
ppm, which the 2015 ozone NAAQS lowered to 0.070 ppm.
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    In addition, emissions from heavy-duty engines can result in higher 
pollutant levels for people living near truck freight routes. Based on 
a study EPA conducted of people living near truck routes, an estimated 
72 million people live within 200 meters of a truck freight route.\12\ 
Relative to the rest of the population, people of color and those with 
lower incomes are more likely to live near truck routes.\13\ This 
population includes children; childcare facilities and schools can also 
be in close proximity to freight routes.\14\
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    \12\ See discussion in Section II.B.7.
    \13\ See Section VII.H for additional discussion on our analysis 
of environmental justice impacts of this final rule.
    \14\ Kingsley, S., Eliot, M., Carlson, L. et al. Proximity of 
U.S. schools to major roadways: a nationwide assessment. J Expo Sci 
Environ Epidemiol 24, 253-259 (2014). https://doi.org/10.1038/jes.2014.5.
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    The final rulemaking will promulgate new numeric standards and 
change key provisions of the existing heavy-duty emission control 
program, including the test procedures, regulatory useful life, 
emission-related warranty, and other requirements. Together, the 
provisions in the final rule will further reduce the air quality 
impacts of heavy-duty engines across a range of operating conditions 
and over a longer portion of the operational life of heavy-duty 
engines.\15\ The requirements in the final

[[Page 4299]]

rule will lower emissions of NOX and other air pollutants 
(PM, hydrocarbons (HC), carbon monoxide (CO), and air toxics) beginning 
no later than model year (MY) 2027. The emission reductions from the 
final rule will increase over time as more new, cleaner vehicles enter 
the fleet.
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    \15\ Note that the terms useful life and operational life are 
different, though they are related. As required by Clean Air Act 
(CAA) section 202(a), the useful life period is when manufacturers 
are required to meet the emissions standards in the final rule; 
whereas, operational life is the term we use to describe the 
duration over which an engine is operating on roadways. We are 
finalizing useful life periods that cover a greater portion of the 
operational life. We consider operational life to be the average 
mileage at rebuild for compression-ignition engines and the average 
mileage at replacement for spark-ignition engines (see preamble 
Section IV.A for details).
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    We estimate that the final rule will reduce NOX 
emissions from heavy-duty vehicles in 2040 by more than 40 percent; by 
2045, a year by which most of the regulated fleet will have turned 
over, heavy-duty NOX emissions will be almost 50 percent 
lower than they would have been without this action. These emission 
reductions will result in widespread decreases in ambient 
concentrations of pollutants such as ozone and PM2.5. We 
estimate that in 2045, the final rule will result in total annual 
monetized ozone- and PM2.5-related benefits of $12 and $33 
billion at a 3 percent discount rate, and $10 and $30 billion at a 7 
percent discount rate. These widespread air quality improvements will 
play an important role in addressing concerns raised by state, local, 
and Tribal governments, as well as communities, about the contributions 
of heavy-duty engines to air quality challenges they face such as 
meeting their obligations to attain or continue to meet NAAQS, and to 
reduce other human health and environmental impacts of air pollution. 
This rule's emission reductions will reduce air pollution in close 
proximity to major roadways, where concentrations of many air 
pollutants are elevated and where people of color and people with low 
income are disproportionately exposed.
    In EPA's judgment, our analyses in this final rule show that the 
final standards will result in the greatest degree of emission 
reduction achievable starting in model year 2027, giving appropriate 
consideration to costs and other factors, which is consistent with 
EPA's statutory authority under Clean Air Act (CAA) section 
202(a)(3)(A).\16\
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    \16\ CAA section 202(a)(3)(A) requires standards for emissions 
of NOX, PM, HC, and CO emissions from heavy-duty vehicles 
and engines to ``reflect the greatest degree of emission reduction 
achievable through the application of technology which the 
Administrator determines will be available for the model year to 
which such standards apply, giving appropriate consideration to 
cost, energy, and safety factors associated with the application of 
such technology.'' Throughout this notice we use terms like 
``maximum feasible emissions reductions'' to refer to this statutory 
requirement to set standards that ``reflect the greatest degree of 
emission reduction achievable . . .'.
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    CAA section 202(a)(1) requires the EPA to ``by regulation prescribe 
(and from time to time revise) . . . standards applicable to the 
emission of any air pollutant from any class or classes of new motor 
vehicles or new motor vehicle engines . . . , which in his judgment 
cause, or contribute to, air pollution which may reasonably be 
anticipated to endanger public health or welfare.'' CAA section 
202(a)(3)(C) requires that NOX, PM, HC, and CO (hereafter 
referred to as ``criteria pollutants'') standards for certain heavy-
duty vehicles and engines apply for no less than 3 model years and 
apply no earlier than 4 years after promulgation.\17\
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    \17\ See Sections I.D and XIII for additional discussion on 
EPA's statutory authority for this action, including our authority 
under CAA sections 202(d) and 207.
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    Although heavy-duty engines have become much cleaner over the last 
decade, catalysts and other technologies have evolved such that harmful 
air pollutants can be reduced even further. The final standards are 
based on technology improvements that have become available over the 20 
years since the last major rule was promulgated to address emissions of 
criteria pollutants and toxic pollutants from heavy-duty engines, as 
well as projections of continued technology improvements that build on 
these existing technologies. The criteria pollutant provisions we are 
adopting in this final rule apply for all heavy-duty engine (HDE) 
classes: Spark-ignition (SI) HDE, as well as compression-ignition (CI) 
Light HDE, CI Medium HDE, and CI Heavy HDE.\18\
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    \18\ This final rule includes new criteria pollutant standards 
for engine-certified Class 2b through 8 heavy-duty engines and 
vehicles. Class 2b and 3 vehicles with a Gross Vehicle Weight Rating 
(GVWR) between 8,500 and 14,000 pounds are primarily commercial 
pickup trucks and vans and are sometimes referred to as ``medium-
duty vehicles.'' The majority of Class 2b and 3 vehicles are 
chassis-certified vehicles, and EPA intends to include them in a 
future combined light-duty and medium-duty rulemaking action, 
consistent with E.O, 14037, Section 2a. SI HDE are typically fueled 
by gasoline, whereas CI HDE are typically fueled by diesel; note 
that the Heavy HDE class, which is largely CI engines, does include 
certain SI engines that are generally natural gas-fueled engines 
intended for use in Class 8 vehicles. See 40 CFR 1036.140 for 
additional description of the primary intended service classes for 
heavy-duty engines. Heavy-duty engines and vehicles are also used in 
nonroad applications, such as construction equipment; nonroad heavy-
duty engines and vehicles are not the focus of this final rule. As 
outlined in I.B of this Executive Summary and detailed in Section 
XI, this final rule also includes limited amendments to regulations 
that implement our air pollutant emission standards for other 
industry sectors, including light-duty vehicles, light-duty trucks, 
marine diesel engines, locomotives, and various types of nonroad 
engines, vehicles, and equipment. See 40 CFR 1036.140 for a 
description of the primary intended service classes for heavy-duty 
engines.
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    As described in Section III, the final standards will reduce 
emissions during a broader range of operating conditions compared to 
the current standards, such that nearly all in-use operation will be 
covered. Available data indicate that emission levels demonstrated for 
certification are not currently achieved under the broad range of real-
world operating conditions.19 20 21 22 In fact, less than 
ten percent of the data collected during a typical test while the 
vehicle is operated on the road is subject to EPA's current on-the-road 
emission standards.\23\ These testing data further show that 
NOX emissions from heavy-duty CI engines are high during 
many periods of vehicle operation that are not subject to current on-
the-road emission standards. For example, ``low-load'' engine 
conditions occur when a vehicle operates in stop-and-go traffic or is 
idling; these low-load conditions can result in exhaust temperature 
decreases that then lead to the diesel engine's selective catalytic 
reduction (SCR)-based emission control system becoming less effective 
or ceasing to function. Test data collected as part of EPA's 
manufacturer-run in-use testing program indicate that this low-load 
operation could account for more than half of the NOX 
emissions from a vehicle during a typical workday.\24\ Similarly, 
heavy-duty SI engines also operate in conditions where their catalyst 
technology becomes less effective, resulting in higher levels of air 
pollutants; however, unlike CI engines, it is sustained medium-to-high 
load operation where emission levels are less certain. To address these 
concerns, as part of our comprehensive approach, the final standards 
include both revisions to our existing test procedures and new test 
procedures to reduce emissions

[[Page 4300]]

from heavy-duty engines under a broader range of operating conditions, 
including low-load conditions.
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    \19\ Hamady, Fakhri, Duncan, Alan. ``A Comprehensive Study of 
Manufacturers In-Use Testing Data Collected from Heavy-Duty Diesel 
Engines Using Portable Emissions Measurement System (PEMS).'' 29th 
CRC Real World Emissions Workshop, March 10-13, 2019.
    \20\ Sandhu, Gurdas, et al. ``Identifying Areas of High 
NOX Operation in Heavy-Duty Vehicles''. 28th CRC Real-
World Emissions Workshop, March 18-21, 2018.
    \21\ Sandhu, Gurdas, et al. ``In-Use Emission Rates for MY 2010+ 
Heavy-Duty Diesel Vehicles''. 27th CRC Real-World Emissions 
Workshop, March 26-29, 2017.
    \22\ As noted in Section I.B and discussed in Section III, 
testing engines and vehicles while they are operating without a 
defined duty cycle is referred to as ``off-cycle'' testing; as 
detailed in Section III, we are finalizing new off-cycle test 
procedures and standards as part of this rulemaking.
    \23\ Heavy-duty CI engines are currently subject to off-cycle 
standards that are not limited to specific test cycles; throughout 
this notice we use the terms ``on-the-road'', ``over the road'', or 
``real world'' interchangeably to refer to off-cycle standards.
    \24\ Sandhu, Gurdas, et al. ``Identifying Areas of High 
NOX Operation in Heavy-Duty Vehicles''. 28th CRC Real-
World Emissions Workshop, March 18-21, 2018.
---------------------------------------------------------------------------

    Data also show that tampering and mal-maintenance of the engine's 
emission control system after the useful life period is projected to 
result in NOX emissions that would represent a substantial 
part of the HD emissions inventory in 2045.\25\ To address this 
problem, as part of our comprehensive approach, the final rule includes 
longer regulatory useful life and emission-related warranty 
requirements to ensure the final emissions standards will be met 
through more of the operational life of heavy-duty 
vehicles.26 27 Further, the final rule includes requirements 
for manufacturers to better ensure that operators keep in-use engines 
and emission control systems working properly in the real world. We 
expect these final provisions to improve maintenance and serviceability 
will reduce incentives to tamper with the emission control systems on 
MY 2027 and later engines, which would avoid large increases in 
emissions that would impact the reductions projected from the final 
rule. For example, we estimate NOX emissions will increase 
more than 3000 percent due to malfunction of the NOX 
emissions aftertreatment on a MY 2027 and later heavy heavy-duty 
vehicle. To address this, the final rule requires manufacturers to meet 
emission standards with less frequent scheduled maintenance for 
emission-related parts and systems, and to provide more information on 
how to diagnose and repair emission control systems. In addition, the 
final rule requires manufacturers to demonstrate that they design their 
engines to limit access to electronic controls to prevent operators 
from reprogramming the engine to bypass or disable emission controls. 
The final rule also specifies a balanced approach for manufacturers to 
design their engines with features to ensure that operators perform 
ongoing maintenance to keep SCR emission control systems working 
properly, without creating a level of burden and corresponding 
frustration for operators that could increase the risk of operators 
completely disabling emission control systems. These provisions 
combined with the longer useful life and warranty periods will provide 
a comprehensive approach to ensure that the new, much more stringent 
emissions standards are met during in use operations.
---------------------------------------------------------------------------

    \25\ See Section VI for more information on projected inventory 
contributions from each operating mode or process, as well as 
discussion on the emissions impacts of tampering and mal-
maintenance.
    \26\ Emission standards set under CAA section 202(a) apply to 
vehicles and engines ``for their useful life.'' CAA section 202(d) 
directs EPA to prescribe regulations under which the useful life of 
vehicles and engines shall be determined, and for heavy-duty 
vehicles and engines establishes minimum values of 10 years or 
100,000 miles, whichever occurs first, unless EPA determines that 
greater values are appropriate. CAA section 207(a) further requires 
manufacturers to provide emission-related warranty, and EPA set the 
current emission-related warranty periods for heavy-duty engines in 
1983 (48 FR 52170, November 16, 1983). See Section I.D for more 
discussion on the statutory authority for the final rule.
    \27\ See Section IV for more discussion on the final useful life 
and warranty requirements.
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    The final standards and requirements are based on further 
consideration of the data included in the proposed rule, as well as 
additional supporting data from our own test programs, and 
consideration of the extensive public input EPA received in response to 
the proposed rule. The proposal was posted on the EPA website on March 
7, 2022, and published in the Federal Register on March 28, 2022 (87 FR 
17414, March 28, 2022). EPA held three virtual public hearings in April 
2022. We received more than 260,000 public comments.\28\ A broad range 
of stakeholders provided comments, including state and local 
governments, heavy-duty engine manufacturers, emissions control 
suppliers and others in the heavy-duty industry, environmental 
organizations, environmental justice organizations, state, local, and 
Tribal organizations, consumer groups, labor groups, private citizens, 
and others. Some of the issues raised in comments included the need for 
new, more stringent NOX standards, particularly in 
communities already overburdened by pollution; the feasibility and 
costs of more stringent NOX standards combined with much 
longer useful life periods; the longer emissions-related warranty 
periods; a single- vs. two-step program; and various details on the 
flexibilities and other program design features of the proposed 
program. We briefly discuss several of these key issues in Section I.B, 
with more detail in later sections in this preamble and in the Response 
to Comments document that is available in the public docket for this 
rule.\29\
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    \28\ Of these comments, 1,860 were unique letters, many of which 
provided data and other detailed information for EPA to consider; 
the remaining comments were mass mailers sponsored by 30 different 
organizations, nearly all of which urged EPA to take action to 
reduce emissions from trucks or to adopt more stringent limits.
    \29\ U.S. EPA, ``Control of Air Pollution from New Motor 
Vehicles: Heavy-Duty Engine and Vehicle Standards--Response to 
Comments'', Docket EPA-HQ-OAR-2019-0055.
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    This Section I provides an overview of the final program, the 
impacts of the final program, and how the final program is consistent 
with EPA's statutory requirements. The need for additional emissions 
control from heavy-duty engines is described in Section II. We describe 
the final standards and compliance flexibilities in detail in Sections 
III and IV. We discuss our analyses of estimated emission reductions, 
air quality improvements, costs, and monetized benefits of the final 
program in Sections V through X. Section XI describes limited 
amendments to the regulations that implement our air pollutant emission 
standards for other sectors (e.g., light-duty vehicles, marine diesel 
engines, locomotives, and various types of nonroad engines, vehicles, 
and equipment).
2. EPA Will Address HD GHG Emissions in a Subsequent Rulemaking
    Although we proposed targeted revisions to the MY2027 GHG Phase 2 
standards as part of the same proposal in which we laid out more 
stringent NOX standards, in this final rule we are not 
taking final action on updates to the GHG standards. Instead, we intend 
to consider potential changes to certain HD GHG Phase 2 standards as 
part of a subsequent rulemaking.

B. Overview of the Final Regulatory Action

    We are finalizing a program that will begin in MY 2027, which is 
the earliest year that these new criteria pollutant standards can begin 
to apply under CAA section 202(a)(3)(C).\30\ The final NOX 
standards are a single-step program that reflect the greatest degree of 
emission reduction achievable starting in MY2027, giving appropriate 
consideration to costs and other factors. The final rule establishes 
not only new, much more stringent NOX standards compared to 
today's standards, but also requires lower NOX emissions 
over a much wider range of testing conditions both in the laboratory 
and when engines are operating on the road. Further, the final 
standards include longer useful life periods, as well as significant 
increases in the emissions-related warranty periods. The longer useful 
life and emissions warranty periods are particularly important for 
ensuring continued emissions control when the engines are operating on 
the road. These final standards will result in significant reductions 
in emissions of NOX, PM2.5, and other air 
pollutants across the country, which we project will meaningfully 
decrease ozone

[[Page 4301]]

concentrations across the country. We expect the largest improvements 
in both ozone and PM2.5 to occur in areas with the worst 
baseline air quality. In a supplemental demographic analysis, we also 
found that larger numbers of people of color are projected to reside in 
these areas with the worst baseline air quality.
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    \30\ Section 202(a)(3)(C) requires that standards under 
202(a)(3)(A), such as the standards in this final rule, apply no 
earlier than 4 years after promulgation, and apply for no less than 
3 model years. See Section I.D for additional discussion on the 
statutory authority for this action.
---------------------------------------------------------------------------

    The final standards and requirements are based on further 
consideration of the data included in the proposed rule, as well as 
additional supporting data from our own test programs, and 
consideration of the extensive public input EPA received in response to 
the proposed rule. As required by CAA section 202(a)(3), the final new 
numeric NOX standards will result in the greatest degree of 
emission reduction achievable for a national program starting in MY 
2027 through the application of technology that the Administrator has 
determined will be available starting in MY 2027, after giving 
appropriate consideration to cost, energy, and safety factors 
associated with the application of such technology. The EPA proposal 
included two options for the NOX program. Proposed Option 1 
was the more stringent option, and it included new standards and other 
program elements starting in MY 2027, which were further strengthened 
in MY 2031. Proposed Option 2 was the less stringent option, with new 
standards and requirements implemented fully in MY 2027. The final 
numeric NOX standards and testing requirements are largely 
consistent with the proposed Option 1 in MY 2027. The final numeric 
standards and regulatory useful life values will reduce NOX 
emissions not only when trucks are new, but throughout a longer period 
of their operational life under real-world conditions. For the smaller 
engine service-class categories, we are finalizing the longest 
regulatory useful life and emissions warranty periods proposed, and for 
the largest engines we are finalizing requirements for useful life and 
emissions aftertreatment durability demonstration that are 
significantly longer than required today.
    As previously noted in this Section I, we received a large number 
and wide range of comments on the proposed rule. Several comments 
raised particularly significant issues related to some fundamental 
components of the proposed program, including the level of the numeric 
standards and feasibility of lower numeric standards combined with 
longer useful life periods. We briefly discuss these key issues in this 
Section I.B, with more detail in later sections in this preamble. The 
Response to Comments document provides our responses to the comments we 
received; it is located in the docket for this rulemaking.
1. Key Changes From the Proposal
i. Feasibility of More Stringent NOX Standards Combined With 
Much Longer Useful Life Periods
    Many stakeholders commented on the proposed numeric NOX 
standards, and the feasibility of maintaining those numeric standards 
over the proposed useful life periods. Environmental organizations and 
other commenters, including suppliers to the heavy-duty industry, 
generally urged EPA to adopt the most stringent standards proposed, or 
to finalize even more stringent standards by fully aligning with the 
California Air Resources Board (CARB) Low NOX Omnibus 
program.\31\ In contrast, most engine manufacturers, truck dealers, 
fleets, and other members of the heavy-duty industry stated that even 
the less stringent proposed numeric standards and useful life periods 
would be extremely challenging to meet, particularly for the largest 
heavy-duty engines. Some of these commenters provided data that they 
stated showed the potential for large impacts on the purchase price of 
a new truck if EPA were to finalize the most stringent proposed numeric 
standards and useful life periods for the largest heavy-duty engines.
---------------------------------------------------------------------------

    \31\ EPA is reviewing a waiver request under CAA section 209(b) 
from California for the Omnibus rule. For more information on the 
California Air Resources Board Omnibus rule see, ``Heavy-Duty Engine 
and Vehicle Omnibus Regulation and Associated Amendments,'' December 
22, 2021. https://ww2.arb.ca.gov/rulemaking/2020/hdomnibuslownox. 
Last accessed September 21, 2022. See also ``California State Motor 
Vehicle Pollution Control Standards and Nonroad Engine Pollution 
Control Standards; The ``Omnibus'' Low NOX Regulation; 
Request for Waivers of Preemption; Opportunity for Public Hearing 
and Public Comment'' at 87 FR 35765 (June 13, 2022).
---------------------------------------------------------------------------

    As summarized in I.B.2 and detailed in preamble Section III, we are 
finalizing numeric NOX standards and useful life periods 
that are largely consistent with the most stringent proposed option for 
MY 2027. For all heavy-duty engine classes, the final numeric 
NOX standards for medium- and high-load engine operations 
match the most stringent standards proposed for MY 2027; for low-load 
operations we are finalizing the most stringent standard proposed for 
any model year (see I.B.1.ii for discussion).\32\ For smaller heavy-
duty engines (i.e., light and medium heavy-duty engines CI and SI 
heavy-duty engines), the numeric standards are combined with the 
longest useful life periods we proposed. The final numeric 
NOX emissions standards and useful life periods for smaller 
heavy-duty engines are based on further consideration of data included 
in the proposal from our engine demonstration programs that show the 
final NOX emissions standards are feasible at the final 
useful life periods applicable to these smaller heavy-duty engines. Our 
assessment of the data available at the time of proposal is further 
supported by our evaluation of additional information and public 
comments stating that the proposed standards are feasible for these 
smaller engine categories. For the largest heavy-duty engines (i.e., 
heavy heavy-duty engines), the final numeric standards are combined 
with the longest useful life mileage that we proposed for MY 2027. The 
final useful life periods for the largest heavy-duty engines are 50 
percent longer than today's useful life periods, which will play an 
important role in ensuring continued emissions control while the 
engines operate on the road.
---------------------------------------------------------------------------

    \32\ As proposed, we are finalizing a new test procedure for 
heavy-duty CI engines to demonstrate emission control when the 
engine is operating under low-load and idle conditions; this new 
test procedure does not apply to heavy-duty SI engines (see Sections 
I.B.2 and III for additional discussion).
---------------------------------------------------------------------------

    After further consideration of the data included in the proposal, 
as well as information submitted by commenters and additional data we 
collected since the time of proposal, we are finalizing two updates 
from our proposed testing requirements in order to ensure the greatest 
degree of emission reduction achievable are met throughout the final 
useful life periods; these updates are tailored to the larger engine 
classes (medium and heavy heavy-duty engines), which have longer useful 
life periods and more rigorous duty-cycles compared to the smaller 
engine classes. First, we are finalizing a requirement for 
manufacturers to demonstrate before heavy heavy-duty engines are in-use 
that the emissions control technology is durable through a period of 
time longer than the final useful life mileage.\33\ For these largest 
engines with the longest useful life mileages, the extended laboratory 
durability demonstration will better ensure the final standards will be 
met throughout the regulatory useful life

[[Page 4302]]

under real-world operations where conditions are more variable. Second, 
we are finalizing an interim compliance allowance that applies when EPA 
evaluates whether the heavy or medium heavy-duty engines are meeting 
the final standards after these engines are in use in the real world. 
When combined with the final useful life values, we believe the interim 
compliance allowance will address concerns raised in comments from 
manufacturers that the more stringent proposed MY 2027 standards would 
not be feasible to meet over the very long useful life periods of heavy 
heavy-duty engines, or under the challenging duty-cycles of medium 
heavy-duty engines. This interim, in-use compliance allowance is 
generally consistent with our past practice (for example, see 66 FR 
5114, January 18, 2001); also consistent with past practice, the 
interim compliance allowance is included as an interim provision that 
we may reassess in the future through rulemaking based on the 
performance of emissions controls over the final useful life periods 
for medium and heavy heavy-duty engines. To set standards that result 
in the greatest emission reductions achievable for medium and heavy 
heavy-duty engines, we considered additional data that we and others 
collected since the time of the proposal; these data show the 
significant technical challenge of maintaining very low NOX 
emissions throughout very long useful life periods for heavy heavy-duty 
engines, and greater amounts of certain aging mechanisms over the long 
useful life periods of medium heavy-duty engines. In addition to these 
data, in setting these standards, we gave appropriate consideration to 
costs associated with the application of technology to achieve maximum 
emissions reductions in MY 2027 (i.e., cost of compliance for 
manufacturers associated with the standards) and other factors. We 
determined that for heavy heavy-duty engines the combination of: (1) 
The most stringent MY 2027 standards proposed, (2) longer useful life 
periods compared to today's useful life periods, (3) targeted, interim 
compliance allowance approach to in-use compliance testing, and (4) the 
extended durability demonstration for emissions control technologies is 
appropriate, feasible, and consistent with our authority under the CAA 
to set technology-forcing NOX pollutant standards for heavy-
duty engines for their useful life.\34\ Similarly, for medium heavy-
duty engines we determined that the combination of the first three 
elements (i.e., most stringent MY 2027 standards proposed, increase in 
useful life periods, and interim compliance allowance for in-use 
testing) is appropriate, feasible, and consistent with our CAA 
authority to set technology-forcing NOX pollutant standards 
for heavy-duty engines for their useful life.
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    \33\ Manufacturers of any size heavy-duty engine must 
demonstrate that the emission control technology is durable through 
a period equivalent to the useful life period of the engine, and may 
be subject to recall if EPA subsequently determines that properly 
maintained and used engines do not conform to our regulations over 
the useful life period (as specified in our regulations and 
consistent with CAA section 207). As outlined here, the extended 
laboratory durability demonstration in the final program will 
require manufacturers of the largest heavy-duty engines to 
demonstrate emission control durability for a longer period to 
better ensure that in-use engines will meet emission standards 
throughout the long regulatory useful life of these engines.
    \34\ CAA section 202(a)(3)(A) is a technology-forcing provision 
and reflects Congress' intent that standards be based on projections 
of future advances in pollution control capability, considering 
costs and other statutory factors. See National Petrochemical & 
Refiners Association v. EPA, 287 F.3d 1130, 1136 (D.C. Cir. 2002) 
(explaining that EPA is authorized to adopt ``technology-forcing'' 
regulations under CAA section 202(a)(3)); NRDC v. Thomas, 805 F.2d 
410, 428 n.30 (D.C. Cir. 1986) (explaining that such statutory 
language that ``seek[s] to promote technological advances while also 
accounting for cost does not detract from their categorization as 
technology-forcing standards''); see also Husqvarna AB v. EPA, 254 
F.3d 195 (D.C. Cir. 2001) (explaining that CAA sections 202 and 213 
have similar language and are technology-forcing standards). In this 
context, the term ``technology-forcing'' has a specific legal 
meaning and is used to distinguish standards that may require 
manufacturers to develop new technologies (or significantly improve 
existing technologies) from standards that can be met using existing 
off-the-shelf technology alone. Technology-forcing standards such as 
those in this final rule do not require manufacturers to use 
specific technologies.
---------------------------------------------------------------------------

ii. Test Procedures To Control Emissions Under a Broader Range of 
Engine Operations
    Many commenters supported our proposal to update our test 
procedures to more accurately account for and control emissions across 
a broader range of engine operation, including in urban driving 
conditions and other operations that could impact communities already 
overburdened with pollution. Consistent with our proposal, we are 
finalizing several provisions to reduce emissions from a broader range 
of engine operating conditions. First, we are finalizing new standards 
for our existing test procedures to reduce emissions under medium- and 
high-load operations (e.g., when trucks are traveling on the highway). 
Second, we are finalizing new standards and a corresponding new test 
procedure to measure emissions during low-load operations (i.e., the 
low-load cycle, LLC). Third, we are finalizing new standards and 
updates to an existing test procedure to measure emissions over the 
broader range of operations that occur when heavy-duty engines are 
operating on the road (i.e., off-cycle). \35\
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    \35\ Duty-cycle test procedures measure emissions while the 
engine is operating over precisely defined duty cycles in an 
emissions testing laboratory and provide very repeatable emission 
measurements. ``Off-cycle'' test procedures measure emissions while 
the engine is not operating on a specified duty cycle; this testing 
can be conducted while the engine is being driven on the road (e.g., 
on a package delivery route), or in an emission testing laboratory. 
Both duty-cycle and off-cycle testing are conducted pre-production 
(e.g., for certification) or post-production to verify that the 
engine meets applicable duty-cycle or off-cycle emission standards 
throughout useful life (see Section III for more discussion).
---------------------------------------------------------------------------

    The new, more stringent numeric standards for the existing 
laboratory-based test procedures that measure emissions during medium- 
and high-load operations will ensure significant emissions reductions 
from heavy-duty engines. Without this final rule, these medium- and 
high-load operations are projected to contribute the most to heavy-duty 
NOX emissions in 2045.
    We are finalizing as proposed a new LLC test procedure, which will 
ensure demonstration of emission control under sustained low-load 
operations. After further consideration of data included in the 
proposal, as well as additional information from the comments 
summarized in this section, we are finalizing the most stringent 
numeric LLC standard proposed for any model year. As discussed in our 
proposal, data from our CI engine demonstration program showed that the 
lowest numeric NOX standard proposed would be feasible for 
the LLC throughout a useful life period similar to the useful life 
period we are finalizing for the largest heavy-duty engines. After 
further consideration of this data, and additional support from data 
collected since the time of proposal, we are finalizing the most 
stringent standard proposed for any model year.
    We are finalizing new numeric standards and revisions to the 
proposed off-cycle test procedure. We proposed updates to the current 
off-cycle test procedure that included binning emissions measurements 
based on the type of operation the engine is performing when the 
measurement data is being collected. Specifically, we proposed that 
emissions data would be grouped into three bins, based on whether the 
engine was operating in idle (Bin 1), low-load (Bin 2), or medium-to-
high load (Bin 3). Given the different operational profiles of each of 
the three bins, we proposed a separate standard for each bin. Based on 
further consideration of data included in the proposal, as well as 
additional support from our consideration of data provided by 
commenters, we are finalizing off-cycle standards for two bins, rather 
than three bins; correspondingly, we are finalizing a two-bin approach 
for grouping emissions data collected during off-cycle test procedures. 
Our evaluation of available information shows that two bins better 
represent the

[[Page 4303]]

differences in engine operations that influence emissions (e.g., 
exhaust temperature, catalyst efficiency) and ensure sufficient data is 
collected in each bin to allow for an accurate analysis of the data to 
determine if emissions comply with the standard for each bin. Preamble 
Section 0 further discusses the final off-cycle standards with 
additional detail in preamble Section III.
iii. Lengthening Emissions-Related Warranty
    EPA received general support from many commenters for the proposal 
to lengthen the emissions-related warranty beyond existing 
requirements. Some commenters expressed support for one of the proposed 
options, and one organization suggested a warranty period even longer 
than either proposed option. Several stakeholders also commented on the 
costs of lengthened warranty periods and potential economic impacts. 
For instance, one state commenter supported EPA's cost estimates and 
agreed that the higher initial cost will be offset by lower repair 
costs; further, the commenter expects the resale value of lengthened 
warranty will be maintained for subsequent owners. In contrast, 
stakeholders in the heavy-duty engine and truck industry (e.g., engine 
and vehicle manufacturers, truck dealers, suppliers of emissions 
control technologies) commented that the proposed warranty periods 
would add costs to vehicles, and raised concerns about these cost 
impacts on first purchasers. Many commenters indicated that purchase 
price increases due to the longer warranty periods may delay emission 
reductions, stating that high costs could incentivize pre-buy and 
reduce fleet turnover from old technology.
    After further consideration of data included in the proposal, and 
consideration of additional supporting information from the comments 
summarized in this Section I.B.1.iii, we are finalizing a single-step 
increase for new, longer warranty periods to begin in MY 2027. Several 
commenters recommended we pull ahead the longest proposed warranty 
periods to start in MY 2027. We agree with that approach for the 
smaller heavy-duty engine classes, and our final warranty mileages 
match the longest proposed warranty periods for these smaller engines 
(i.e., Spark-ignition HDE, Light HDE, and Medium HDE). However, we are 
finalizing a different approach for the largest heavy-duty engines 
(i.e., Heavy HDE). We are finalizing a warranty mileage that matches 
the MY 2027 step of the most stringent proposed option to maximize the 
emission control assurance and to cover a percentage of the final 
useful life that is more consistent with the warranty periods of the 
smaller engine classes. The final emissions warranty periods are 
approximately two to four times longer than today's emissions warranty 
periods. The durations of the final emissions warranty periods balance 
two factors: First, the expected improvements in engine emission 
performance from longer emissions warranty periods due to increases in 
maintenance and lower rates of tampering with emissions controls (see 
preamble Section IV.B for more discussion); and second, the potential, 
particularly for the largest heavy-duty engines, for very large 
increases in purchase price due to much longer warranty periods to slow 
fleet turnover through increases in pre- and low-buy, and subsequently 
result in fewer emissions reductions. We are finalizing emissions 
warranty periods that in our evaluation will provide a significant 
increase in the emissions warranty coverage while avoiding large 
increases in the purchase price of a new truck.
iv. Model Year 2027 Single-Step Program
    Many stakeholders expressed support for a single-step program to 
implement new emissions standards and program requirements beginning in 
model year 2027, which is consistent with one of the proposed options. 
Stakeholders in the heavy-duty engine and truck industry, including 
suppliers of emissions controls technologies, truck dealers, and engine 
manufacturers, generally stated that a single-step program avoids 
technology disruptions and allows industry to focus on research and 
development for zero-emissions vehicle technologies for model years 
beyond 2027. Some of these commenters further noted that a two-step 
approach would result in gaps in available technology for some vehicle 
types and could exacerbate slower fleet turnover from pre- and low-buy 
associated with new standards. The trade association for truck dealers 
noted that a two-step approach would significantly compromise expected 
vehicle performance characteristics, including fuel economy. Other 
commenters also generally supported a single-step approach in order for 
the most stringent standards to begin as soon as possible, which would 
lead to larger emissions reductions earlier than a two-step approach. 
Several of these stakeholders noted the importance of early emissions 
reductions in communities already overburdened with pollution.
    The final NOX standards are a single-step program that 
reflect the greatest emission reductions achievable starting in MY 
2027, giving appropriate consideration to costs and other factors. In 
this final rule, we are focused on achieving the greatest emission 
reductions achievable in the MY 2027 timeframe, and have applied our 
judgment in determining the appropriate standards for MY 2027 under our 
CAA authority for a national program. As the heavy-duty industry 
continues to transition to zero-emission technologies, EPA could 
consider additional criteria pollutant standards for model years beyond 
2027 in future rules.
v. Averaging, Banking, and Trading of NOX Emissions
    The majority of stakeholders supported the proposed program to 
allow averaging, banking, and trading (ABT) of NOX 
emissions, although several suggested adjustments for EPA to consider 
in the final rule. Stakeholders provided additional input on several 
specific aspects of the proposed ABT program, including the proposed 
family emissions limit (FEL) caps, the proposed Early Adoption 
Incentives, and the proposed allowance for manufacturers to generate 
NOX emissions credits from Zero Emissions Vehicles (ZEVs). 
In this Section we briefly discuss stakeholder perspectives on these 
specific aspects of the proposed ABT program, as well as our approach 
for each in the final rule.
a. Family Emissions Limit Caps
    A wide range of stakeholders urged EPA to finalize a lower FEL cap 
than proposed; there was broad agreement that the FEL cap in the final 
rule should be 100 mg/hp-hr or lower, with commenters citing various 
considerations, such as the magnitude of reduction between the current 
and proposed standards, as well as the desire to prevent competitive 
disruption.
    After further consideration, including consideration of public 
comments, we are finalizing lower FEL caps than proposed. The FEL caps 
in the final rule are 65 mg/hp-hr for MY 2027 through 2030, and 50 mg/
hp-hr for MY 2031 and later. Our rationale for the final FEL caps 
includes two main factors. First, we agree with commenters that the 
difference between the current standard (approximately 200 mg/hp-hr) 
and the standards we are finalizing for MY 2027 and later suggests that 
FEL caps lower than the current standard are

[[Page 4304]]

appropriate to ensure that available emissions control technologies are 
adopted. This is consistent with our past practice when issuing rules 
for heavy-duty onroad engines or nonroad engines in which there was a 
substantial (e.g., greater than 50 percent) difference between the 
numeric levels of the existing and new standards (69 FR 38997, June 29, 
2004; 66 FR 5111, January 18, 2001). Specifically, by finalizing FEL 
caps below the current standards, we are ensuring that the vast 
majority of new engines introduced into commerce include updated 
emissions control technologies compared to the emissions control 
technologies manufacturers use to meet the current standards.\36\
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    \36\ As discussed in Section IV.G.9, we are finalizing an 
allowance for manufacturers to continue to produce a small number (5 
percent of production volume) of engines that meet the current 
standards for a few model years (i.e., through MY 2030); thus, the 
vast majority of, but not all, new engines will need to include 
updated emissions control technologies compared to those used to 
meet today's standards until MY 2031, when all engines will need 
updated emissions control technologies to comply with the final 
standards or use credits up to the FEL cap. See Section IV.G.9 for 
details on our approach and rationale for including this allowance 
in the final rule.
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    Second, finalizing FEL caps below the current standard is 
consistent with comments from manufacturers stating that a FEL cap of 
100 mg/hp-hr or between 50 and 100 mg/hp-hr would help to prevent 
competitive disruptions (i.e., require all manufacturers to make 
improvements in their emissions control technologies).
    The FEL caps for the final rule have been set at a level to ensure 
sizeable emission reductions from the current 2010 standards, while 
providing manufacturers with flexibility in meeting the final 
standards. When combined with the other restrictions in the final ABT 
program (i.e., credit life, averaging sets, expiration of existing 
credit balances), we determined the final FEL caps of 65 mg/hp-hr in 
MYs 2027 through 2030, and 50 mg/hp-hr in MY 2031 and later avoid 
potential adverse effects on the emissions reductions expected from the 
final program.
b. Encouraging Early Adoption of New Emissions Controls Technologies
    Several stakeholders provided general comments on the proposed 
Early Adoption Incentive program, which included emissions credit 
multipliers of 1.5 or 2.0 for meeting all proposed requirements prior 
to the applicable model year. Although many of the stakeholders in the 
heavy-duty engine industry generally supported incentives such as 
emissions credit multipliers to encourage early investments in 
emissions reductions technology; other industry stakeholders were 
concerned that the multipliers would incentivize some technologies 
(e.g., hybrid powertrains, natural gas engines) over others (e.g., 
battery-electric vehicles). Environmental organizations and other 
commenters were concerned that the emissions credit multipliers would 
result in an excess of credits that would undermine some of the 
benefits of the rule.
    After consideration of public comments, EPA is not finalizing the 
proposed Early Adoption Incentives program, and in turn we are not 
including emissions credit multipliers in the final program. Rather, we 
are finalizing an updated version of the proposed transitional credit 
program under the ABT program. As described in preamble Section IV.G.7, 
the transitional credit program that we are finalizing provides four 
pathways to generate straight NOX emissions credits (i.e., 
no credit multipliers) in order to encourage the early introduction 
engines with NOX-reducing technology.
c. Heavy-Duty Zero Emissions Vehicles and NOX Emissions 
Credits
    Numerous stakeholders provided feedback on EPA's proposal to allow 
manufacturers to generate NOX emissions credits from ZEVs. 
Environmental organizations and other commenters, as well as suppliers 
of heavy-duty engine and vehicle components, broadly oppose allowing 
manufacturers to generate NOX emissions credits from ZEVs. 
These stakeholders present several lines of argument, including the 
potential for: (1) Substantial impacts on the emissions reductions 
expected from the proposed rule, which could also result in 
disproportionate impacts in disadvantaged communities already 
overburdened with pollution; and (2) higher emissions from internal 
combustion engines, rather than further incentives for additional ZEVs 
(further noting that other State and Federal actions are providing more 
meaningful and less environmentally costly HD ZEV incentives). In 
contrast, heavy-duty engine and vehicle manufacturers generally support 
allowing manufacturers to generate these credits. These stakeholders 
also provided several lines of argument, including: (1) The potential 
for ZEVs to help meet emissions reductions and air quality goals; (2) 
an assertion that ZEV NOX credits are essential to the 
achievability of the standards for some manufacturers; and (3) ZEV 
NOX credits allow manufacturers to manage investments across 
different products that may ultimately result in increased ZEV 
deployment.
    After further consideration, including consideration of public 
comments, we are not finalizing the allowance for manufacturers to 
generate NOX emissions credits from heavy-duty ZEVs. Our 
decision is based on two primary considerations. First, the standards 
in the final rule are technology-forcing, yet achievable for MY 2027 
and later internal combustion engines without this flexibility. Second, 
because the final standards are not based on projected utilization of 
ZEV technology, and because we believe there will be increased 
penetration of ZEVs in the heavy-duty fleet by MY 2027 and later,\37\ 
we are concerned that allowing ZEVs to generate NOX 
emissions credits would result in fewer emissions reductions than 
intended from this rule. For example, by allowing manufacturers to 
generate ZEV NOX credits, EPA would be allowing higher 
emissions (through internal combustion engines using credits to emit up 
to the FEL cap) in MY 2027 and later, without requiring commensurate 
emissions reductions (through additional ZEVs beyond those already 
entering the market without this rule). This erosion of emissions 
benefits could have particularly adverse impacts in communities already 
overburdened by pollution. In addition, we continue to believe that 
testing requirements to ensure continued battery and fuel cell 
performance over the useful life of a ZEV may be important to ensure 
the zero-emissions tailpipe performance for which they are generating 
NOX credits; however, after further consideration, including 
consideration of public comments, we believe it is appropriate to take 
additional time to work with industry and other stakeholders on any 
test procedures and other specifications for ZEV battery and fuel cell 
performance over the useful life period of the ZEV.
---------------------------------------------------------------------------

    \37\ For example, the recently passed Inflation Reduction Act 
(IRA) has many incentives for promoting zero-emission vehicles, see 
Sections 13403 (Qualified Clean Vehicles), 13404 (Alternative Fuel 
Refueling Property Credit), 60101 (Clean Heavy-Duty Vehicles), 60102 
(Grants to Reduce Air Pollution at Ports), and 70002 (United States 
Postal Service Clean Fleets) of H. R. 5376.
---------------------------------------------------------------------------

2. Summary of the Key Provisions in the Regulatory Action
i. Controlling Criteria Pollutant Emissions Under a Broader Range of 
Operating Conditions
    The final rule provisions will reduce emissions from heavy-duty 
engines

[[Page 4305]]

under a range of operating conditions through revisions to our 
emissions standards and test procedures. These revisions will apply to 
both laboratory-based standards and test procedures for both heavy-duty 
CI and SI engines, as well as the off-cycle standards and test 
procedures for heavy-duty CI engines. These final provisions are 
outlined immediately below and detailed in Section III.
a. Final Laboratory Standards and Test Procedures
    For heavy-duty CI engines, we are finalizing new standards for 
laboratory-based tests using the current duty cycles, the transient 
Federal Test Procedure (FTP) and the steady-state Supplemental Emission 
Test (SET) procedure. These existing test procedures require CI engine 
manufacturers to demonstrate the effectiveness of emission controls 
when the engine is transitioning from low-to-high loads or operating 
under sustained high load, but do not include demonstration of emission 
control under sustained low-load operations. As proposed, we are 
finalizing a new, laboratory-based LLC test procedure for heavy-duty CI 
engines to demonstrate emission control when the engine is operating 
under low-load and idle conditions. The addition of the LLC will help 
ensure lower NOX emissions in urban areas and other 
locations where heavy-duty vehicles operate in stop-and-go traffic or 
other low-load conditions. As stated in Section I.B.1, we are 
finalizing the most stringent standard proposed for any model year for 
low-load operations based on further evaluation of data included in the 
proposal, and supported by information received during the comment 
period. We are also finalizing as proposed the option for manufacturers 
to test hybrid engines and powertrains together using the final 
powertrain test procedure.
    For heavy-duty SI engines, we are finalizing new standards for 
laboratory-based testing using the current FTP duty cycle, as well as 
updates to the current engine mapping procedure to ensure the engines 
achieve the highest torque level possible during testing. We are also 
finalizing the proposed addition of the SET duty-cycle test procedure 
to the heavy-duty SI laboratory demonstrations; it is currently only 
required for heavy-duty CI engines. Heavy-duty SI engines are 
increasingly used in larger heavy-duty vehicles, which makes it more 
likely for these engines to be used in higher-load operations covered 
by the SET.
    Our final NOX emission standards for all defined duty 
cycles for heavy-duty CI and SI engines are detailed in Table I-1. As 
shown, the final NOX standards will be implemented with a 
single step in MY 2027 and reflect the greatest emission reductions 
achievable starting in MY 2027, giving appropriate consideration to 
costs and other factors. As discussed in I.B.1.i, for the largest 
heavy-duty engines we are finalizing two updates to our testing 
requirements to ensure the greatest emissions reductions technically 
achievable are met throughout the final useful life periods of the 
largest heavy-duty engines: (1) A requirement for manufacturers to 
demonstrate before heavy heavy-duty engines are in-use that the 
emissions control technology are durable through a period of time 
longer than the final useful mileage, and (2) a compliance allowance 
that applies when EPA evaluates whether medium or heavy heavy-duty 
engines are meeting the final standards after these engines are in-use 
in the real world. We requested comment on an interim compliance 
allowance, and it is consistent with our past practice (for example, 
see 66 FR 5114, January 18, 2001); the interim compliance allowance is 
shown in the final column of Table I-1. See Section III for more 
discussion on feasibility of the final standards. Consistent with our 
existing, MY 2010 standards for criteria pollutants, the final 
standards, presented in Table 1, are numerically identical for SI and 
CI engines.\38\
---------------------------------------------------------------------------

    \38\ See Section III for our final PM, HC, and CO standards.

        Table I-1--Final NOX Emission Standards for Heavy-Duty CI and SI Engines on Specific Duty Cycles
                                     [milligrams/horsepower-hour (mg/hp-hr)]
----------------------------------------------------------------------------------------------------------------
                                                                      Current       Model years 2027 and later
                                                                 -----------------------------------------------
                                                                                  Spark ignition    Medium and
                                                                                    HDE, light    heavy HDE with
                                                                  All HD engines    HDE, medium   interim in-use
                                                                                  HDE, and heavy    compliance
                                                                                        HDE          allowance
----------------------------------------------------------------------------------------------------------------
Federal Test Procedure (transient mid/high load conditions).....             200              35              50
Supplemental Emission Test (steady-state conditions)............             200              35              50
Low Load Cycle (low-load conditions)............................             N/A              50              65
----------------------------------------------------------------------------------------------------------------

b. Final On-the-Road Standards and Test Procedures
    In addition to demonstrating emission control over defined duty 
cycles tested in a laboratory, heavy-duty CI engines must be able to 
demonstrate emission control over operations experienced while engines 
are in use on the road in the real world (i.e., ``off-cycle'' 
testing).\39\ We are finalizing with revisions the proposed updates to 
the procedure for off-cycle testing, such that data collected during a 
wider range of operating conditions will be valid, and therefore 
subject to emission standards.
---------------------------------------------------------------------------

    \39\ As discussed in Section III, ``off-cycle'' testing measures 
emissions while the engine is not operating on a specified duty 
cycle; this testing can be conducted while the engine is being 
driven on the road (e.g., on a package delivery route), or in an 
emission testing laboratory.
---------------------------------------------------------------------------

    Similar to the current approach, emission measurements collected 
during off-cycle testing will be collected on a second-by-second basis. 
As proposed, we are finalizing that the emissions data will be grouped 
into 300-second windows of operation. Each 300-second window will then 
be binned based on the type of operation that the engine performs 
during that 300-second period. Specifically, the average power of the 
engine during each 300-second window will determine whether the 
emissions during that window are binned as idle (Bin 1), or non-idle 
(Bin 2).\40\
---------------------------------------------------------------------------

    \40\ Due to the challenges of measuring engine power directly on 
in-use vehicles, we are finalizing as proposed the use of the 
CO2 emission rate (grams per second) as a surrogate for 
engine power; further, we are finalizing as proposed to normalize 
CO2 emission rates relative to the nominal maximum 
CO2 rate of the engine (e.g., when an engine with a 
maximum CO2 emission rate of 50 g/sec emits at a rate of 
10 g/sec, its normalized CO2 emission rate is 20 
percent).

---------------------------------------------------------------------------

[[Page 4306]]

    Our final, two-bin approach covers a wide range of operations that 
occur in the real world--significantly more in-use operation than 
today's requirements. Bin 1 includes extended idle and other very low-
load operations, where engine exhaust temperatures may drop below the 
optimal temperature where SCR-based aftertreatment works best. Bin 2 
includes a large fraction of urban driving conditions, during which 
engine exhaust temperatures are generally moderate, as well as higher-
power operations, such as on-highway driving, that typically results in 
higher exhaust temperatures and high catalyst efficiencies.\41\ Given 
the different operational profiles of each of these two bins, we are 
finalizing, as proposed, a separate standard for each bin. As proposed, 
the final structure follows that of our current not-to-exceed (NTE) 
off-cycle standards where testing is conducted while the engine 
operates on the road conducting its normal driving patterns, however, 
the final standards apply over a much broader range of engine 
operation.
---------------------------------------------------------------------------

    \41\ Because the final approach considers time-averaged power, 
either of the bins could include some idle operation and any of the 
bins could include some high-power operation.
---------------------------------------------------------------------------

    Table I-2 presents our final off-cycle standards for NOX 
emissions from heavy-duty CI engines. As discussed in I.B.1.i, for the 
medium and heavy heavy-duty engines we are also finalizing an interim 
compliance allowance that applies to non-idle (Bin 2) off-cycle 
standard after the engines are in-use. This interim compliance 
allowance is consistent with our past practice (for example, see 66 FR 
5114, January 18, 2001) and is shown in the final column of Table I-2. 
See Section III for details on the final off-cycle standards for other 
pollutants.

 Table I-2--Final Off-Cycle NOX Standards for Heavy-Duty CI Engines \a\
------------------------------------------------------------------------
                                            Model years 2027 and later
                                         -------------------------------
                                                          Medium HDE and
                                            Light HDE,    heavy HDE with
                                            medium HDE,       in-use
                                             heavy HDE      compliance
                                                             allowance
------------------------------------------------------------------------
Bin 1: Idle (g/hr)......................            10.0        \b\ 10.0
Bin 2: Low/medium/high load (mg/hp-hr)..              58              73
------------------------------------------------------------------------
\a\ The standards reflected in Table I-2 are applicable at 25 [deg]C and
  above; at lower temperatures the numerical off-cycle Bin 1 and Bin 2
  standards for NOX adjust as a function of ambient air temperature (see
  preamble Section III.C for details).
\b\ The interim compliance allowance we are finalizing for medium and
  heavy heavy-duty engines does not apply to the Bin 1 (Idle) off-cycle
  standard (see preamble Section III for details).

    In addition to the final standards for the defined duty cycle and 
off-cycle test procedures, the final standards include several other 
provisions for controlling emissions from specific operations in CI or 
SI engines. First, we are finalizing, as proposed, to allow CI engine 
manufacturers to voluntarily certify to idle standards using a new idle 
test procedure that is based on an existing California Air Resources 
Board (CARB) procedure.\42\
---------------------------------------------------------------------------

    \42\ 13 CCR 1956.8 (a)(6)(C)--Optional NOX idling 
emission standard.
---------------------------------------------------------------------------

    We are also finalizing two options for manufacturers to control 
engine crankcase emissions. Specifically, manufacturers will be 
required to either: (1) As proposed, close the crankcase, or (2) 
measure and account for crankcase emissions using an updated version of 
the current requirements for an open crankcase. We believe that either 
will ensure that the total emissions are accounted for during 
certification testing and throughout the engine operation during useful 
life. See Section III.B for more discussion on both the final idle and 
crankcase provisions.
    For heavy-duty SI, we are finalizing as proposed a new refueling 
emission standard for incomplete vehicles above 14,000 lb GVWR starting 
in MY 2027.\43\ The final refueling standard is based on the current 
refueling standard that applies to complete heavy-duty gasoline-fueled 
vehicles. Consistent with the current evaporative emission standards 
that apply for these same vehicles, we are finalizing a requirement 
that manufacturers can use an engineering analysis to demonstrate that 
they meet our final refueling standard. We are also adopting an 
optional alternative phase-in compliance pathway that manufacturers can 
opt into in lieu of being subject to this implementation date for all 
incomplete heavy-duty vehicles above 14,000 pounds GVWR (see Section 
III.E for details).
---------------------------------------------------------------------------

    \43\ Some vehicle manufactures sell their engines or 
``incomplete vehicles'' (i.e., chassis that include their engines, 
the frame, and a transmission) to body builders who design and 
assemble the final vehicle.
---------------------------------------------------------------------------

ii. Ensuring Standards Are Met Over a Greater Portion of an Engine's 
Operational Life
    In addition to reducing emissions under a broad range of engine 
operating conditions, the final program also includes provisions to 
ensure emissions standards are met over a greater portion of an 
engine's operational life. These final provisions include: (1) 
Lengthened regulatory useful life periods for heavy-duty engines, (2) 
revised requirement for the largest heavy-duty engines to demonstrate 
that the emissions control technology is durable through a period of 
time longer than the final useful life mileage, (3) updated methods to 
more accurately and efficiently demonstrate the durability of emissions 
controls, (4) lengthened emission warranty periods, and (5) increased 
assurance that emission controls will be maintained properly through 
more of the service life of heavy-duty engines. Each of these final 
provisions is outlined immediately below and detailed in Section IV.
a. Final Useful Life Periods
    Consistent with the proposal, the final useful life periods will 
cover a significant portion of the engine's operational life.\44\ The 
longer useful life periods, in combination with the durability 
demonstration requirements we are finalizing in this rule, are expected 
to lead manufacturers to further improve the durability of their

[[Page 4307]]

emission-related components. After additional consideration of data 
included in the proposal, as well as additional data provided in public 
comments, we are modifying our proposed useful life periods to account 
for the combined effect of useful life and the final numeric standards 
on the overall stringency and emissions reductions of the program (see 
Section IV.A for additional details).
---------------------------------------------------------------------------

    \44\ We consider operational life to be the average mileage at 
rebuild for CI engines and the average mileage at replacement for SI 
engines (see preamble Section IV.A for details).
---------------------------------------------------------------------------

    For smaller heavy-duty engines (i.e., Spark-ignition HDE, Light 
HDE, and Medium HDE) we are finalizing the longest useful life periods 
proposed (i.e., MY 2031 step of proposed option 1), to apply starting 
in MY 2027. The final useful life mileage for Heavy HDE, which has a 
distinctly longer operational life than the smaller engine classes, is 
approximately 50 percent longer than today's useful life mileage for 
these engines and matches the longest useful life we proposed for MY 
2027. Our final useful life periods for all heavy-duty engine classes 
are presented in Table I-3. We are also increasing the years-based 
useful life from the current 10 years to values that vary by engine 
class and match the respective proposed options. After considering 
comments, we are also adding hours-based useful life values to all 
engine categories based on a 20 mile per hour speed threshold and the 
corresponding final mileage values.\45\
---------------------------------------------------------------------------

    \45\ As noted in this I.B.2, we are finalizing, as proposed, 
refueling standards for certain HD SI engines that apply for a 
useful life of 15 years or 150,000 miles. See 40 CFR 1037.103(f) and 
preamble Section IV.A for more details.

                Table I-3--Current and Final Useful Life Periods for Heavy-Duty CI and SI Engines
----------------------------------------------------------------------------------------------------------------
                                                   Current                           MY 2027 and later
  Primary intended service class   -----------------------------------------------------------------------------
                                       Miles        Years        Hours        Miles        Years        Hours
----------------------------------------------------------------------------------------------------------------
Spark-ignition HDE \a\............      110,000           10  ...........      200,000           15       10,000
Light HDE \a\.....................      110,000           10  ...........      270,000           15       13,000
Medium HDE........................      185,000           10  ...........      350,000           12       17,000
Heavy HDE \b\.....................      435,000           10       22,000      650,000           11       32,000
----------------------------------------------------------------------------------------------------------------
\a\ Current useful life period for Spark-ignition HDE and Light HDE for GHG emission standards is 15 years or
  150,000 miles; we are not revising these useful life periods in this final rule. See 40 CFR 1036.108(d).
\b\ As discussed in Section I.B.2.ii.c, we are finalizing a requirement for manufacturers to demonstrate at the
  time of certification that the emissions controls on these largest heavy-duty engines are durable through the
  equivalent of 750,000 miles.

b. Extended Laboratory Demonstration of Emissions Control Durability 
for the Largest Heavy-Duty Engines
    As discussed in Section I.B.1.i, for the largest heavy-duty engines 
we are finalizing two updates to our proposed testing requirements in 
order to ensure the greatest emissions reductions technically 
achievable are met throughout the final useful life periods of these 
engines. One of the approaches (an in-use interim compliance allowance 
for medium and heavy heavy-duty engines) was noted in Section I.B.2.i; 
here we focus on the requirement for manufacturers to demonstrate 
before the largest heavy-duty engines are in use that the emissions 
control technology is durable through a period of time longer than the 
final useful mileage. Specifically, we are finalizing a requirement for 
manufacturers to demonstrate before the largest heavy-duty engines are 
in use that the emissions controls on these engines are durable (e.g., 
capable of controlling NOX emissions over the FTP duty-cycle 
at a level of 35 mg/hp-hr) through the equivalent of 750,000 miles. The 
extended durability demonstration in a laboratory environment will 
better ensure the final standards will be met throughout the longer 
final regulatory useful life mileage of 650,000 miles when these 
engines are operating in the real world where conditions are more 
variable.\46\ As discussed immediately below in Section I.B.2.ii.c, we 
are also finalizing provisions to improve the accuracy and efficiency 
of emissions control durability demonstrations for all heavy-duty 
engine classes.
---------------------------------------------------------------------------

    \46\ Once these engines are in use, EPA can require 
manufacturers to submit test data, or can conduct our own testing, 
to verify that the emissions control technologies continue to 
control emissions through the 650,000 mile useful life period (or 
the equivalent hours or years requirements as applicable).
---------------------------------------------------------------------------

c. Final Durability Demonstration
    EPA regulations require manufacturers to include durability 
demonstration data as part of an application for certification of an 
engine family. Manufacturers typically complete this demonstration by 
following regulatory procedures to calculate a deterioration factor 
(DF). The final useful life periods outlined in Table I-4 will require 
manufacturers to extend their durability demonstrations to show that 
the engines will meet applicable emission standards throughout the 
lengthened useful life.
    To address the need for accurate and efficient emission durability 
demonstration methods, EPA worked with manufacturers and CARB to 
address this concern through guidance for MY 2020 and later 
engines.\47\ Consistent with the recent guidance, we proposed three 
methods for determining DFs. We are finalizing two of the three 
proposed methods; we are not finalizing the option to perform a fuel-
based accelerated DF determination, noting that it has been shown to 
underestimate emission control system deterioration. The two methods we 
are finalizing include: (1) Allowing manufacturers to continue the 
current practice of determining DFs based on engine dynamometer-based 
aging of the complete engine and aftertreatment system out to 
regulatory useful life, and (2) a new option to bench-age the 
aftertreatment system at an accelerated rate to limit the burden of 
generating a DF over the final lengthened useful life periods. If 
manufacturers choose the second option (accelerated bench-aging of the 
aftertreatment system), then they may also choose to use an accelerated 
aging test procedure that we are codifying in this final rule; the test 
procedure is, based on a test program that we introduced in the 
proposal to evaluate a rapid-aging protocol for diesel catalysts. We 
are also finalizing with revisions two of the three proposed DF 
verification options to confirm the accuracy of the DF values submitted 
by manufacturers for certification. After further consideration of data 
included in the proposal, as well as supported by

[[Page 4308]]

information provided in public comments, we are finalizing that, upon 
EPA request, manufacturers would be required to provide confirmation of 
the DF accuracy through one of two options.
---------------------------------------------------------------------------

    \47\ U.S. EPA. ``Guidance on Deterioration Factor Validation 
Methods for Heavy-Duty Diesel Highway Engines and Nonroad Diesel 
Engines equipped with SCR.'' CD-2020-19 (HD Highway and Nonroad). 
November 17, 2020.
---------------------------------------------------------------------------

d. Final Emission-Related Warranty Periods
    We are updating and significantly strengthening the emission-
related warranty periods, for model year 2027 and later heavy-duty 
engines.\48\ We are finalizing most of the emission-related warranty 
provisions of 40 CFR 1036.120 as proposed. Following our approach for 
useful life, we are revising the proposed warranty periods for each 
primary intended service class to reflect the difference in average 
operational life of each class and in consideration of the information 
provided by commenters (see preamble Section IV and the Response to 
Comments document for details).
---------------------------------------------------------------------------

    \48\ Components installed to control only criteria pollutant 
emissions or both greenhouse gas (i.e., CO2, 
N2O, and CH4) and criteria pollutant emissions 
would be subject to the final warranty periods of 40 CFR 1036.120. 
See 40 CFR 1036.150(w).
---------------------------------------------------------------------------

    EPA's current emissions-related warranty periods for heavy-duty 
engines range from 22 percent to 54 percent of the current regulatory 
useful life. Notably, these percent values have decreased over time 
given that the warranty periods have not changed since 1983 even as the 
useful life periods were lengthened.\49\ The revised warranty periods 
are expected to result in better maintenance, including maintenance of 
emission-related components, and less tampering, which would help to 
ensure the benefits of the emission controls in-use. In addition, 
longer regulatory warranty periods may lead engine manufacturers to 
simplify repair processes and make them more aware of system defects 
that need to be tracked and reported to EPA.
---------------------------------------------------------------------------

    \49\ The useful life for heavy heavy-duty engines was increased 
from 290,000 miles to 435,000 miles for 2004 and later model years 
(62 FR 54694, October 21, 1997).
---------------------------------------------------------------------------

    Our final emission-related warranty periods for heavy-duty engines 
are presented in Table I-4. The final warranty mileages that apply 
starting in MY 2027 for Spark-ignition HDE, Light HDE, and Medium HDE 
match the longest warranty mileages proposed (i.e., MY 2031 step of 
proposed Option 1) for these primary intended service classes. For 
Heavy HDE, which has a distinctly longer operational life, the final 
warranty mileage matches the longest warranty mileage proposed to apply 
in MY 2027 (i.e., MY 2027 step of proposed Option 1), and is more than 
four times longer than today's warranty mileage for these engines. We 
are also increasing the years-based warranty from the current 5 years 
to 10 years for all engine classes. After considering comments, we are 
also adding hours-based warranty values to all primary intended service 
classes based on a 20 mile per hour speed threshold and the 
corresponding final mileage values. Consistent with current warranty 
provisions, the warranty period would be whichever warranty value 
(i.e., mileage, hours, or years) occurs first.

    Table I-4--Current and Final Emission-Related Warranty Periods for Heavy-Duty CI and SI Engines Criteria
                                               Pollutant Standards
----------------------------------------------------------------------------------------------------------------
                                                   Current                       Model year 2027 and later
  Primary intended service class   -----------------------------------------------------------------------------
                                      Mileage       Years        Hours       Mileage       Years        Hours
----------------------------------------------------------------------------------------------------------------
Spark-Ignition HDE................       50,000            5  ...........      160,000           10        8,000
Light HDE.........................       50,000            5  ...........      210,000           10       10,000
Medium HDE........................      100,000            5  ...........      280,000           10       14,000
Heavy HDE.........................      100,000            5  ...........      450,000           10       22,000
----------------------------------------------------------------------------------------------------------------

e. Provisions To Ensure Long-Term Emissions Performance
    We proposed several approaches for an enhanced, comprehensive 
strategy to increase the likelihood that emission controls will be 
maintained properly through more of the operational life of heavy-duty 
engines, including beyond their useful life periods. These approaches 
include updated maintenance provisions, revised requirements for the 
owner's manual and emissions label, codified engine derates or 
``inducements'' regulations, and updated onboard diagnostics (OBD) 
regulations.
    Our final updates to maintenance provisions include defining the 
type of maintenance manufacturers may choose to recommend to owners in 
maintenance instructions, updating minimum maintenance intervals for 
certain critical emission-related components, and outlining specific 
requirements for maintenance instructions provided in the owner's 
manual.
    We are finalizing changes to the owner's manual and emissions label 
requirements to ensure access to certain maintenance information and 
improve serviceability. We expect this additional maintenance 
information to improve factors that contribute to mal-maintenance, 
which would result in better service experiences for independent repair 
technicians, specialized repair technicians, owners who repair their 
own equipment, and possibly vehicle inspection and maintenance 
technicians. We also believe improving owner experiences with operating 
and maintaining heavy-duty engines can reduce the likelihood of 
tampering.
    In addition, we are adopting inducement regulations that are an 
update to and replace existing guidance regarding recommended methods 
for manufacturers to reduce engine performance to induce operators to 
maintain appropriate levels of high-quality diesel emission fluid (DEF) 
in their SCR-based aftertreatment systems and discourage tampering with 
such systems. See Section IV.D for details on the principles we 
followed to develop multi-step derate schedules that are tailored to 
different operating characteristics, as well as changes in the final 
rule inducement regulations from the proposal.
    We are also finalizing updated OBD regulations both to better 
address newer diagnostic methods and available technologies, and to 
streamline provisions where possible. We are incorporating by reference 
the current CARB OBD regulations, updated in 2019, as proposed.\50\ 
Specifically, manufacturers must comply with OBD requirements as 
referenced in the CARB

[[Page 4309]]

OBD regulations starting in model year 2027, with optional compliance 
based on the CARB OBD regulations for earlier model years. After 
considering comments, many of which included specific technical 
information and requests for clarification, we are finalizing certain 
provisions with revisions from proposal and postponing others for 
consideration in a future rulemaking (see Section IV.C for details).
---------------------------------------------------------------------------

    \50\ CARB's 2019 Heavy-duty OBD Final Regulation Order was 
approved and became effective October 3, 2019. Title 13, California 
Code of Regulations sections 1968.2, 1968.5, 1971.1, and 1971.5, 
available at https://ww2.arb.ca.gov/rulemaking/2018/heavy-duty-board-diagnostic-system-requirements-2018.
---------------------------------------------------------------------------

iii. Averaging, Banking, and Trading of NOX Emissions 
Credits
    In addition the key program provisions, EPA is finalizing an 
averaging, banking, and trading (ABT) program for heavy-duty engines 
that provides manufacturers with flexibility in their product planning 
while encouraging the early introduction of emissions control 
technologies and maintaining the expected emissions reductions from the 
program. Several core aspects of the final ABT program are consistent 
with the proposal, but the final ABT program also includes several 
updates after consideration of public comments. In particular, EPA 
requested comment on and agrees with commenters that a lower family 
emission limit (FEL) cap than proposed is appropriate for the final 
rule. Further, after consideration of public comments, EPA is choosing 
not to finalize at this time the proposed Early Adoption Incentives 
program, and in turn we are not including emissions credit multipliers 
in the final program. Rather, we are finalizing an updated version of 
the proposed transitional credit program under the ABT program. The 
revised transitional credit program that we are finalizing provides 
four pathways to generate NOX emissions credits in MYs 2022 
through 2026 that are valued based on the extent to which the engines 
generating credits comply with the requirements we are finalizing for 
MY 2027 and later (e.g., credits discounted at a rate of 40 percent for 
engines meeting a lower numeric standard but none of the other MY 2027 
and later requirements). Specifically, the four transitional credit 
pathways in the final rule are: (1) In MY 2026, for heavy heavy-duty or 
medium heavy-duty engine service classes, certify all engines in the 
manufacturer's respective service class to a FEL of 50 mg/hp-hr or less 
and meet all other EPA requirements for MYs 2027 and later to generate 
undiscounted credits that have additional flexibilities for use in MYs 
2027 and later (2026 Service Class Pull Ahead Credits); (2) starting in 
MY 2024, certify one or more engine family(ies) to a FEL below the 
current MY 2010 emissions standards and meet all other EPA requirements 
for MYs 2027 and later to generate undiscounted credits based on the 
longer UL periods included in the 2027 and later program (Full 
Credits); (3) starting in MY 2024, certify one or more engine 
family(ies) to a FEL below the current MY 2010 emissions standards and 
several of the key requirements for MYs 2027 and later, while meeting 
the current useful life and warranty requirements to generate 
undiscounted credits based on the shorter UL period (Partial Credits); 
(4) starting in MY 2022, certify one or more engine family(ies) to a 
FEL below the current MY 2010 emissions standards, while complying with 
all other MY2010 requirements, to generate discounted credits 
(Discounted Credits). We note that the transitional credit and main ABT 
program we are finalizing does not allow engines certified to state 
standards that are different than the Federal EPA standards to generate 
Federal EPA credits.
    In addition, we are finalizing an optional production volume 
allowance for MYs 2027 through 2029 that is consistent with our request 
for comment in the proposal but different in several key aspects, 
including a requirement for manufacturers to use NOX 
emissions credits to certify heavy heavy-duty engines compliant with MY 
2010 requirements in MYs 2027 through 2029. Finally, we have decided 
not to finalize an allowance for manufacturers to generate 
NOX emissions credits from heavy-duty ZEVs (see Section IV.G 
for details on the final ABT program).
iv. Migration From 40 CFR Part 86, Subpart A
    Heavy-duty criteria pollutant regulations were originally codified 
into 40 CFR part 86, subpart A, in the 1980s. As discussed in the 
proposal, this rulemaking provides an opportunity to clarify and 
improve the wording of our existing heavy-duty criteria pollutant 
regulations in plain language and migrate them to 40 CFR part 1036.\51\ 
Part 1036, which was created for the Phase 1 GHG program, provides a 
consistent, updated format for our heavy-duty regulations, with 
improved organization. In general, this migration is not intended to 
change the compliance program specified in part 86, except as 
specifically stated in this final rulemaking. See our summary of the 
migration in Section III.A. The final provisions of part 1036 will 
generally apply for model years 2027 and later, unless noted, and 
manufacturers will continue to use part 86 in the interim.
---------------------------------------------------------------------------

    \51\ We are also adding and amending some provisions in parts 
1065 and 1068 as part of the migration from part 86 for heavy-duty 
highway engines; these provisions in part 1065 and 1068 will apply 
to other sectors that are already subject to part 1065 and 1068. 
Additionally, some current vehicle provisions in part 1037 refer to 
part 86 and, as proposed, the final rule updates those references in 
part 1037 as needed.
---------------------------------------------------------------------------

v. Technical Amendments to Regulatory Provisions for Mobile Source 
Sectors
    EPA has promulgated emission standards for highway and nonroad 
engines, vehicles, and equipment. Section XI of this final rule 
describes several amendments to correct, clarify, and streamline a wide 
range of regulatory provisions for many of those different types of 
engines, vehicles, and equipment. Section XI.A includes technical 
amendments to compliance provisions that apply broadly across EPA's 
emission control programs to multiple industry sectors, including 
light-duty vehicles, light-duty trucks, marine diesel engines, 
locomotives, and various other types of nonroad engines, vehicles, and 
equipment. Some of those amendments are for broadly applicable testing 
and compliance provisions in 40 CFR parts 1065, 1066, and 1068. Other 
cross-sector issues involve making the same or similar changes in 
multiple standard-setting parts for individual industry sectors. The 
rest of Section XI describes amendments we are finalizing that apply 
uniquely for individual industry sectors. Except as specifically 
identified in this rulemaking, EPA did not reopen any of the underlying 
provisions across these standard setting parts.
    We are finalizing amendments in two areas of note for the general 
compliance provisions in 40 CFR part 1068. First, we are finalizing, 
with updates from proposal, a comprehensive approach for making 
confidentiality determinations related to compliance information that 
companies submit to or is collected by EPA. These provisions apply for 
highway, nonroad, and stationary engine, vehicle, and equipment 
programs, as well as aircraft and portable fuel containers.
    Second, we are finalizing, with updates from proposal, provisions 
that include clarifying text to establish what qualifies as an 
adjustable parameter and to identify the practically adjustable range 
for those adjustable parameters. The adjustable-parameter provisions in 
the final rule also include specific provisions related to electronic 
controls that aim to deter tampering.

[[Page 4310]]

C. Impacts of the Standards

1. Projected Emission Reductions and Air Quality Improvements
    Our analysis of the estimated emission reductions, air quality 
improvements, costs, and monetized benefits of the final rule is 
outlined in this section and detailed in Sections V through X. The 
final standards, which are described in detail in Sections III and IV, 
are expected to reduce emissions from highway heavy-duty engines in 
several ways. We project the final emission standards for heavy-duty CI 
engines will reduce tailpipe emissions of NOX; the 
combination of the final low-load test cycle and off-cycle test 
procedure for CI engines will help to ensure that the reductions in 
tailpipe emissions are achieved in-use, not only under high-speed, on-
highway conditions, but also under low-load and idle conditions. We 
also project reduced tailpipe emissions of NOX from the 
final emission standards for heavy-duty SI engines, as well as 
reductions of CO, PM, VOCs, and associated air toxics, particularly 
under cold-start and high-load operating conditions. The final 
emissions warranty and regulatory useful life requirements for heavy-
duty CI and SI engines will also help maintain emissions controls of 
all pollutants beyond the existing useful life periods, which will 
result in additional emissions reductions of all pollutants from both 
CI and SI engines, including primary exhaust PM2.5. The 
onboard refueling vapor recovery requirements for heavy-duty SI engines 
will reduce VOCs and associated air toxics. Table I-5 summarizes the 
projected reductions in heavy-duty emissions from the final standards 
in 2045 and shows the significant reductions in NOX 
emissions. Section VI and Regulatory Impact Analysis (RIA) Chapter 5 
provide more information on our projected emission reductions for the 
final rule.

  Table I-5--Projected Heavy-Duty Emission Reductions in 2045 From the
                             Final Standards
------------------------------------------------------------------------
                                                              Percent
                                                           reduction in
                        Pollutant                         highway heavy-
                                                          duty emissions
                                                             (percent)
------------------------------------------------------------------------
NOX.....................................................              48
Primary PM2.5...........................................               8
VOC.....................................................              23
CO......................................................              18
------------------------------------------------------------------------

    The final standards will also reduce emissions of other pollutants. 
For instance, the final rule will result in a 28 percent reduction in 
benzene from highway heavy-duty engines in 2045. Leading up to 2045, 
emission reductions are expected to increase over time as the fleet 
turns over to new, compliant engines.
    We expect this rule will decrease ambient concentrations of air 
pollutants, including significant improvements in ozone concentrations 
in 2045, as demonstrated in the air quality modeling analysis. We also 
expect reductions in ambient PM2.5, NO2 and CO 
due to this rule. The emission reductions provided by the final 
standards will be important in helping areas attain and maintain the 
NAAQS and prevent future nonattainment. This rule's emission reductions 
will also reduce air pollution in close proximity to major roadways, 
reduce nitrogen deposition and improve visibility.
    Our consideration of environmental justice literature indicates 
that people of color and people with low income are disproportionately 
exposed to elevated concentrations of many pollutants in close 
proximity to major roadways. We also used our air quality data from the 
proposal to conduct a demographic analysis of human exposure to future 
air quality in scenarios with and without the rule in place. Although 
the spatial resolution of the air quality modeling is not sufficient to 
capture very local heterogeneity of human exposures, particularly the 
pollution concentration gradients near roads, the analysis does allow 
estimates of demographic trends at a national scale. To compare 
demographic trends, we sorted 2045 baseline air quality concentrations 
from highest to lowest concentration and created two groups: Areas 
within the contiguous United States with the worst air quality and the 
rest of the country. We found that in the 2045 baseline, the number of 
people of color living within areas with the worst air quality is 
nearly double that of non-Hispanic Whites. We also found that the 
largest predicted improvements in both ozone and PM2.5 are 
estimated to occur in areas with the worst baseline air quality, where 
larger numbers of people of color are projected to reside. An expanded 
analysis of the air quality impacts experienced by specific race and 
ethnic groups found that non-Hispanic Blacks will receive the greatest 
improvement in PM2.5 and ozone concentrations as a result of 
the standards. More details on our air quality modeling and demographic 
analyses are included in Section VII and RIA Chapter 6.
2. Summary of Costs and Benefits
    Our estimates of reductions in heavy-duty engine emissions and the 
associated air quality impacts are based on manufacturers adding 
emissions-reduction technologies and making emission control components 
more durable in response to the final standards and longer regulatory 
useful life periods; our estimates of emissions reductions also account 
for improved repair of emissions controls by owners in response to the 
longer emissions-related warranty periods and other provisions in the 
final rule.
    Our program cost analysis includes both the total technology costs 
(i.e., manufacturers' costs to add or update emissions control 
technologies) and the operating costs (i.e., owners' costs to maintain 
and operate MY 2027 and later vehicles) (see Section V and RIA Chapter 
7). Our evaluation of total technology costs of the final rule includes 
direct costs (i.e., cost of materials, labor costs) and indirect 
manufacturing costs (e.g., warranty, research and development). The 
direct manufacturing costs include individual technology costs for 
emission-related engine components and for exhaust aftertreatment 
systems. Importantly, our analysis of direct manufacturing costs 
includes the costs of the existing emission control technologies, 
because we expect the emissions warranty and regulatory useful life 
provisions in the final standards to have some impact on not only the 
new technology added to comply with the standards, but also on any 
existing emission control components. The cost estimates thus account 
for existing engine hardware and aftertreatment systems for which new 
costs will be incurred due to the new warranty and useful life 
provisions, even absent any changes in the level of emission standards. 
The indirect manufacturing costs in our analysis include the additional 
costs--research and development, marketing, administrative costs, 
etc.--incurred by manufacturers in running the company.
    As part of our evaluation of operating costs, we estimate costs 
truck owners incur to repair emission control system components. Our 
repair cost estimates are based on industry data showing the amount 
spent annually by truck owners on different types of repairs, and our 
estimate of the percentage of those repairs that are related to 
emission control components. Our analysis of this data shows that 
extending the useful life and emission warranty periods will lower 
emission repair costs during several years of operation for several 
vehicle types. More discussion on our

[[Page 4311]]

emission repair costs estimates is included in Section V, with 
additional details presented in RIA Chapter 7.
    We combined our estimates of emission repair costs with other 
operating costs (i.e., urea/DEF, fuel consumption) and technology costs 
to calculate total program costs. Our analysis of the final standards 
shows that total costs for the final program relative to the baseline 
(or no action scenario) range from $3.9 billion in 2027 to $4.7 billion 
in 2045 (2017 dollars, undiscounted, see Table V-16). The present value 
of program costs for the final rule, and additional details are 
presented in Section V.
    Section VIII presents our analysis of the human health benefits 
associated with the final standards. We estimate that in 2045, the 
final rule will result in total annual monetized ozone- and 
PM2.5-related benefits of $12 and $33 billion at a 3 percent 
discount rate, and $10 and $30 billion at a 7 percent discount 
rate.\52\ These benefits only reflect those associated with reductions 
in NOX emissions (a precursor to both ozone and secondarily-
formed PM2.5) and directly-emitted PM2.5 from 
highway heavy-duty engines.
---------------------------------------------------------------------------

    \52\ 2045 is a snapshot year chosen to approximate the annual 
health benefits that occur when the final program will be fully 
implemented and when most of the regulated fleet will have turned 
over.
---------------------------------------------------------------------------

    There are additional human health and environmental benefits 
associated with reductions in exposure to ambient concentrations of 
PM2.5, ozone, and NO2 that EPA has not quantified 
due to data, resource, or methodological limitations. There will also 
be health benefits associated with reductions in air toxic pollutant 
emissions that result from the final program, but we did not attempt to 
quantify or monetize those impacts due to methodological limitations. 
Because we were unable to quantify and monetize all of the benefits 
associated with the final program, the monetized benefits presented in 
this analysis are an underestimate of the program's total benefits. 
More detailed information about the benefits analysis conducted for the 
final rule, including the present value of program benefits, is 
included in Section VIII and RIA Chapter 8.
    We compare total monetized health benefits to total costs 
associated with the final rule in Section IX. Table I-6 shows that 
annual benefits of the final rule will be larger than the annual costs 
in 2045, with annual net benefits of $6.9 and $29 billion assuming a 3 
percent discount rate, and net benefits of $5.8 and $25 billion 
assuming a 7 percent discount rate.\53\ The benefits of the final rule 
also outweigh the costs when expressed in present value terms and as 
equalized annual values (see Section IX for these values).\54\
---------------------------------------------------------------------------

    \53\ The range of benefits and net benefits reflects a 
combination of assumed PM2.5 and ozone mortality risk 
estimates and selected discount rate.
    \54\ EPA's analysis of costs and benefits does not include 
California's Omnibus rule or actions by other states to adopt it. 
EPA is reviewing a waiver request under CAA section 209(b) from 
California for the Omnibus rule; until EPA grants the waiver, the HD 
Omnibus program is not enforceable. EPA's analysis also does not 
include the recent IRA of 2022, which we anticipate will accelerate 
zero emissions technology in the heavy-duty sector.

        Table I-6--Final Costs, Benefits and Net Benefits in 2045
                            [billions, 2017$]
------------------------------------------------------------------------
                                            3% Discount     7% Discount
------------------------------------------------------------------------
Benefits................................         $12-$33         $10-$30
Costs...................................            $4.7            $4.7
Net Benefits............................        $6.9-$29        $5.8-$25
------------------------------------------------------------------------

3. Summary of Economic Impacts
    Section X examines the potential impacts of the final rule on 
heavy-duty vehicles (sales, mode shift, fleet turnover) and employment 
in the heavy-duty industry. The final rule may impact vehicle sales due 
to both changes in purchase price and longer emission warranty mileage 
requirements. The final rule may impact vehicle sales by increasing 
purchases of new vehicles before the final standards come into effect, 
in anticipation of higher prices after the standards (``pre-buy''). The 
final rule may also reduce sales after the final standards are in place 
(``low-buy''). In this final rule, we outline an approach to quantify 
potential impacts on vehicle sales due to new emission standards. Our 
illustrative analysis for this final rule, discussed in RIA Chapter 
10.1, suggest pre- and low-buy for Class 8 trucks may range from zero 
to approximately 2 percent increase in sales over a period of up to 8 
months before the 2027 standards begin (pre-buy), and a decrease in 
sales from zero to approximately 3 percent over a period of up to 12 
months after the 2027 standards begin (low-buy). We expect little mode 
shift due to the final rule because of the large difference in cost of 
moving goods via trucks versus other modes of transport (e.g., planes 
or barges).
    Employment impacts of the final rule depend on the effects of the 
rule on sales, the share of labor in the costs of the rule, and changes 
in labor intensity due to the rule. We quantify the effects of costs on 
employment, and we discuss the effects due to sales and labor intensity 
qualitatively. In response to comments, we have added a discussion in 
Chapter 10 of the RIA describing a method that could be used to 
quantitatively estimate a demand effect on employment, as well as an 
illustrative application of that method. The partial quantification of 
employment impacts due to increases in the costs of vehicles and parts, 
holding labor intensity constant, shows an increase in employment by 
1,000 to 5,300 job-years in 2027.\55\ See Section X for further detail 
on limitations and assumptions of this analysis.
---------------------------------------------------------------------------

    \55\ A job-year is, for example, one year of full-time work for 
one person, or one year of half-time work for two people.
---------------------------------------------------------------------------

D. EPA Statutory Authority for This Action

    This section briefly summarizes the statutory authority for the 
final rule. Title II of the Clean Air Act provides for comprehensive 
regulation of mobile sources, authorizing EPA to regulate emissions of 
air pollutants from all mobile source categories. Specific Title II 
authorities for this final rule include: CAA sections 202, 203, 206, 
207, 208, 213, 216, and 301 (42 U.S.C. 7521, 7522, 7525, 7541, 7542, 
7547, 7550, and 7601). We discuss some key aspects of these sections in 
relation to this final action immediately below (see also Section XIII 
of this preamble), as well as in each of the relevant sections later in 
this preamble. As noted in Section I.B.2.v, the final rule includes 
confidentiality determinations for much of the information collected by 
EPA for certification and compliance under Title II; see Section XI.A. 
for discussion of

[[Page 4312]]

relevant statutory authority for these final rule provisions.
    Statutory authority for the final NOX, PM, HC, and CO 
emission standards in this action comes from CAA section 202(a), which 
states that ``the Administrator shall by regulation prescribe (and from 
time to time revise) . . . standards applicable to the emission of any 
air pollutant from any class or classes of new . . . motor vehicle 
engines, which in his judgment cause, or contribute to, air pollution 
which may reasonably be anticipated to endanger public health or 
welfare.'' Standards under CAA section 202(a) take effect after such 
period as the Administrator finds necessary to permit the development 
and application of the requisite technology, giving appropriate 
consideration to the cost of compliance within such period.''
    Section 202(a)(3) further addresses EPA authority to establish 
standards for emissions of NOX, PM, HC, and CO from heavy-
duty engines and vehicles. Section 202(a)(3)(A) requires that such 
standards ``reflect the greatest degree of emission reduction 
achievable through the application of technology which the 
Administrator determines will be available for the model year to which 
such standards apply, giving appropriate consideration to cost, energy, 
and safety factors associated with the application of such 
technology.'' Section 202(a)(3)(B) allows EPA to take into account air 
quality information in revising such standards. Section 202(a)(3)(C) 
provides that standards shall apply for a period of no less than three 
model years beginning no earlier than the model year commencing four 
years after promulgation. CAA section 202(a)(3)(A) is a technology-
forcing provision and reflects Congress' intent that standards be based 
on projections of future advances in pollution control capability, 
considering costs and other statutory factors.56 57 CAA 
section 202(a)(3) neither requires that EPA consider all the statutory 
factors equally nor mandates a specific method of cost-analysis; rather 
EPA has discretion in determining the appropriate consideration to give 
such factors.\58\
---------------------------------------------------------------------------

    \56\ See National Petrochemical & Refiners Association v. EPA, 
287 F.3d 1130, 1136 (D.C. Cir. 2002) (explaining that EPA is 
authorized to adopt ``technology-forcing'' regulations under CAA 
section 202(a)(3)); NRDC v. Thomas, 805 F.2d 410, 428 n.30 (D.C. 
Cir. 1986) (explaining that such statutory language that ``seek[s] 
to promote technological advances while also accounting for cost 
does not detract from their categorization as technology-forcing 
standards''); see also Husqvarna AB v. EPA, 254 F.3d 195 (D.C. Cir. 
2001) (explaining that CAA sections 202 and 213 have similar 
language and are technology-forcing standards).
    \57\ In this context, the term ``technology-forcing'' has a 
specific legal meaning and is used to distinguish standards that may 
require manufacturers to develop new technologies (or significantly 
improve existing technologies) from standards that can be met using 
off-the-shelf technology alone. Technology-forcing standards such as 
those in this final rule do not require manufacturers to use 
specific technologies.
    \58\ See, e.g., Sierra Club v. EPA, 325 F.3d 374, 378 (D.C. Cir. 
2003) (explaining that similar technology-forcing language in CAA 
section 202(l)(2) ``does not resolve how the Administrator should 
weigh all [the statutory] factors in the process of finding the 
`greatest emission reduction achievable' ''); Husqvarna AB v. EPA, 
254 F.3d 195, 200 (D.C. Cir. 2001) (explaining that under CAA 
section 213's similar technology-forcing authority that ``EPA did 
not deviate from its statutory mandate or frustrate congressional 
will by placing primary significance on the `greatest degree of 
emission reduction achievable' '' or by considering cost and other 
statutory factors as important but secondary).
---------------------------------------------------------------------------

    CAA section 202(d) directs EPA to prescribe regulations under which 
the useful life of vehicles and engines are determined and establishes 
minimum values of 10 years or 100,000 miles, whichever occurs first, 
unless EPA determines that a period of greater duration or mileage is 
appropriate. EPA may apply adjustment factors to assure compliance with 
requirements in use throughout useful life (CAA section 206(a)). CAA 
section 207(a) requires manufacturers to provide emissions-related 
warranty, which EPA last updated in its regulations for heavy-duty 
engines in 1983 (see 40 CFR 86.085-2).\59\
---------------------------------------------------------------------------

    \59\ 48 FR 52170, November 16, 1983.
---------------------------------------------------------------------------

    EPA is promulgating the final emission standards pursuant to its 
authority under CAA section 202(a), including 202(a)(3)(A). Section II 
and Chapter 4 of the RIA describe EPA's analysis of information 
regarding heavy-duty engines' contribution to air pollution and how 
that pollution adversely impacts public health and welfare. Sections 
III and IV discuss our feasibility analysis of the emission standards 
and useful life periods in the final rule, with more detail in Chapter 
3 of the RIA. Our analysis shows that the final emission standards and 
useful life periods are feasible and will result in the greatest 
emission reductions achievable for the model years to which they will 
apply, pursuant to CAA section 202(a)(3), giving appropriate 
consideration to costs, lead time, and other factors. Our analysis of 
the final standards includes providing manufacturers with sufficient 
time to ensure that emission control components are durable enough for 
the longer useful life periods in the final program. In setting the 
final emission standards, EPA appropriately assessed the statutory 
factors specified in CAA section 202(a)(3)(A), including giving 
appropriate consideration to the cost associated with the application 
of technology EPA determined will be available for the model year the 
final standards apply (i.e., cost of compliance for the manufacturer 
associated with the application of such technology). EPA's assessment 
of the relevant statutory factors in CAA section 202(a)(3)(A) justify 
the final emission standards. We also evaluated additional factors, 
including factors to comply with E.O. 12866; our assessment of these 
factors lend further support to the final rule.
    As proposed, we are finalizing new emission standards along with 
new and revised test procedures for both laboratory-based duty-cycles 
and off-cycle testing. Manufacturers demonstrate compliance over 
specified duty-cycle test procedures during pre-production testing, as 
well as confirmatory testing during production, which is conducted by 
EPA or the manufacturer. Test data and other information submitted by 
the manufacturer as part of their certification application are the 
basis on which EPA issues certificates of conformity pursuant to CAA 
section 206. Under CAA section 203, sales of new vehicles are 
prohibited unless the vehicle is covered by a certificate of 
conformity. Compliance with engine emission standards is required 
throughout the regulatory useful life of the engine, not only at 
certification but throughout the regulatory useful life in-use in the 
real word. In-use engines can be tested for compliance with duty-cycle 
and off-cycle standards, with testing over corresponding specific duty-
cycle test procedures and off-cycle test procedures, either on the road 
or in the laboratory (see Section III for more discussion on for 
testing at various stages in the life of an engine).
    Also as proposed, we are finalizing lengthened regulatory useful 
life and emission warranty periods to better reflect the mileages and 
time periods over which heavy-duty engines are driven today. These and 
other provisions in the final rule are further discussed in the 
preamble sections that follow. The proposed rule (87 FR 17414, March 
28, 2022) includes additional information relevant to the development 
of this rule, including: History of Emissions Standards for Heavy-duty 
Engines and Vehicles; Petitions to EPA for Additional NOX 
control; the California Heavy-Duty Highway Low NOX Program 
Development; and the Advance Notice of Proposed Rulemaking.

[[Page 4313]]

II. Need for Additional Emissions Control

    This final rule will reduce emissions from heavy-duty engines that 
contribute to ambient levels of ozone, PM, NOX and CO, which 
are all pollutants for which EPA has established health-based NAAQS. 
These pollutants are linked to premature death, respiratory illness 
(including childhood asthma), cardiovascular problems, and other 
adverse health impacts. Many groups are at greater risk than healthy 
people from these pollutants, including people with heart or lung 
disease, outdoor workers, older adults and children. These pollutants 
also reduce visibility and negatively impact ecosystems. This final 
rule will also reduce emissions of air toxics from heavy-duty engines. 
A more detailed discussion of the health and environmental effects 
associated with the pollutants affected by this rule is included in 
Sections II.B and II.C and Chapter 4 of the RIA.
    Populations who live, work, or go to school near high-traffic 
roadways experience higher rates of numerous adverse health effects, 
compared to populations far away from major roads. We note that there 
is substantial evidence that people who live or attend school near 
major roadways are more likely to be people of color, Hispanic 
ethnicity, and/or low socioeconomic status.
    Across the United States, NOX emissions from heavy-duty 
engines are important contributors to concentrations of ozone and 
PM2.5 and their resulting threat to public 
health.60 61 The emissions modeling done for the final rule 
(see Chapter 5 of the RIA) indicates that without these standards, 
heavy-duty engines will continue to be one of the largest contributors 
to mobile source NOX emissions nationwide in the future, 
representing 32 percent of the mobile source NOX in calendar 
year 2045.\62\ Furthermore, it is estimated that heavy-duty engines 
would represent 90 percent of the onroad NOX inventory in 
calendar year 2045.\63\ The emission reductions that will occur from 
the final rule are projected to reduce air pollution that is (and is 
projected to continue to be) at levels that endanger public health and 
welfare. For the reasons discussed in this Section II, EPA concludes 
that new standards are warranted to address the emissions of these 
pollutants and their contribution to national air pollution. We note 
that in the summer of 2016 more than 20 organizations, including state 
and local air agencies from across the country, petitioned EPA to 
develop more stringent NOX emission standards for on-road 
heavy-duty engines.64 65 Among the reasons stated by the 
petitioners for such an EPA rulemaking was the need for NOX 
emission reductions to reduce adverse health and welfare impacts and to 
help areas attain the NAAQS. EPA responded to the petitions on December 
20, 2016, noting that an opportunity exists to develop a new national 
NOX reduction strategy for heavy-duty highway engines.\66\ 
We subsequently initiated this rulemaking and issued an Advanced Notice 
of Proposed Rulemaking in January 2020.\67\ This final rule culminates 
the rulemaking proceeding and is responsive to those petitions.
---------------------------------------------------------------------------

    \60\ Zawacki et al., 2018. Mobile source contributions to 
ambient ozone and particulate matter in 2025. Atmospheric 
Environment, Vol 188, pg 129-141. Available online: https://doi.org/10.1016/j.atmosenv.2018.04.057.
    \61\ Davidson et al., 2020. The recent and future health burden 
of the U.S. mobile sector apportioned by source. Environmental 
Research Letters. Available online: https://doi.org/10.1088/1748-9326/ab83a8.
    \62\ Sectors other than onroad and nonroad were projected from 
2016v1 Emissions Modeling Platform. https://www.epa.gov/air-emissions-modeling/2016v1-platform.
    \63\ U.S. EPA (2020) Motor Vehicle Emission Simulator: MOVES3. 
https://www.epa.gov/moves.
    \64\ Brakora, Jessica. ``Petitions to EPA for Revised 
NOX Standards for Heavy-Duty Engines'' Memorandum to 
Docket EPA-HQ-OAR-2019-0055. December 4, 2019.
    \65\ 87 FR 17414, March 28, 2022.
    \66\ U.S. EPA. 2016. Memorandum in Response to Petition for 
Rulemaking to Adopt Ultra-Low NOX Standards for On-
Highway Heavy-Duty Trucks and Engines. Available at https://19january2017snapshot.epa.gov/sites/production/files/2016-12/documents/nox-memorandum-nox-petition-response-2016-12-20.pdf.
    \67\ The Agency published an ANPR on January 21, 2020 to present 
EPA's early thinking on this rulemaking and solicit feedback from 
stakeholders to inform this proposal (85 FR 3306).
---------------------------------------------------------------------------

    Many state and local agencies across the country commented on the 
NPRM and have asked the EPA to reduce NOX emissions, 
specifically from heavy-duty engines, because such reductions will be a 
critical part of many areas' strategies to attain and maintain the 
ozone and PM NAAQS. These state and local agencies anticipate 
challenges in attaining the NAAQS, maintaining the NAAQS in the future, 
and/or preventing nonattainment. Some nonattainment areas have already 
been ``bumped up'' to higher classifications because of challenges in 
attaining the NAAQS; others say they are struggling to avoid 
nonattainment.\68\ Others note that the ozone and PM NAAQS are being 
reconsidered so they could be made more stringent in the 
future.69 70 Many state and local agencies commented on the 
NPRM that heavy-duty vehicles are one of their largest sources of 
NOX emissions. They commented that without action to reduce 
emissions from heavy-duty vehicles, they will have to adopt other 
potentially more burdensome and costly measures to reduce emissions 
from other sources under their state or local authority, such as local 
businesses. More information on the projected emission reductions and 
air quality impacts that will result from this rule is provided in 
Sections VI and VII.
---------------------------------------------------------------------------

    \68\ For example, in September 2019 several 2008 ozone 
nonattainment areas were reclassified from moderate to serious, 
including Dallas, Chicago, Connecticut, New York/New Jersey and 
Houston, and in January 2020, Denver. Also, on September 15, 2022, 
EPA finalized reclassification, bumping up 5 areas in nonattainment 
of the 2008 ozone NAAQS from serious to severe and 22 areas in 
nonattainment of the 2015 ozone NAAQS from marginal to moderate. The 
2008 NAAQS for ozone is an 8-hour standard with a level of 0.075 
ppm, which the 2015 ozone NAAQS lowered to 0.070 ppm.
    \69\ https://www.epa.gov/ground-level-ozone-pollution/epa-reconsider-previous-administrations-decision-retain-2015-ozone.
    \70\ https://www.epa.gov/pm-pollution/national-ambient-air-quality-standards-naaqs-pm.
---------------------------------------------------------------------------

    In their comments on the NPRM, many nonprofit groups, citizen 
groups, individuals, and state, local, and Tribal organizations 
emphasized the role that emissions from trucks have in harming 
communities and that communities living near truck routes are 
disproportionately people of color and those with lower incomes. They 
supported additional NOX reductions from heavy-duty vehicles 
to address concerns about environmental justice and ensuring that all 
communities benefit from improvements in air quality. In addition, many 
groups and commenters noted the link between emissions from heavy duty 
trucks and harmful health effects, in particular asthma in children. 
Commenters also supported additional NOX reductions from 
heavy-duty vehicles to address concerns about regional haze, and damage 
to terrestrial and aquatic ecosystems. They mentioned the impacts of 
NOX emissions on numerous locations, such as the Chesapeake 
Bay, Long Island Sound, the Rocky Mountains, Sierra Nevada Mountains, 
Appalachian Mountains, Southwestern Desert ecosystems, and other areas. 
For further detail regarding these comments and EPA's responses, see 
Section 2 of the Response to Comments document for this rulemaking.

A. Background on Pollutants Impacted by This Proposal

1. Ozone
    Ground-level ozone pollution forms in areas with high 
concentrations of ambient nitrogen oxides (NOX) and

[[Page 4314]]

volatile organic compounds (VOCs) when solar radiation is strong. Major 
U.S. sources of NOX are highway and nonroad motor vehicles, 
engines, power plants and other industrial sources, with natural 
sources, such as soil, vegetation, and lightning, serving as smaller 
sources. Vegetation is the dominant source of VOCs in the United 
States. Volatile consumer and commercial products, such as propellants 
and solvents, highway and nonroad vehicles, engines, fires, and 
industrial sources also contribute to the atmospheric burden of VOCs at 
ground-level.
    The processes underlying ozone formation, transport, and 
accumulation are complex. Ground-level ozone is produced and destroyed 
by an interwoven network of free radical reactions involving the 
hydroxyl radical (OH), NO, NO2, and complex reaction 
intermediates derived from VOCs. Many of these reactions are sensitive 
to temperature and available sunlight. High ozone events most often 
occur when ambient temperatures and sunlight intensities remain high 
for several days under stagnant conditions. Ozone and its precursors 
can also be transported hundreds of miles downwind, which can lead to 
elevated ozone levels in areas with otherwise low VOC or NOX 
emissions. As an air mass moves and is exposed to changing ambient 
concentrations of NOX and VOCs, the ozone photochemical 
regime (relative sensitivity of ozone formation to NOX and 
VOC emissions) can change.
    When ambient VOC concentrations are high, comparatively small 
amounts of NOX catalyze rapid ozone formation. Without 
available NOX, ground-level ozone production is severely 
limited, and VOC reductions would have little impact on ozone 
concentrations. Photochemistry under these conditions is said to be 
``NOX-limited.'' When NOX levels are sufficiently 
high, faster NO2 oxidation consumes more radicals, dampening 
ozone production. Under these ``VOC-limited'' conditions (also referred 
to as ``NOX-saturated'' conditions), VOC reductions are 
effective in reducing ozone, and NOX can react directly with 
ozone, resulting in suppressed ozone concentrations near NOX 
emission sources. Under these NOX-saturated conditions, 
NOX reductions can actually increase local ozone under 
certain circumstances, but overall ozone production (considering 
downwind formation) decreases. Even in VOC-limited areas, 
NOX reductions are not expected to increase ozone levels if 
the NOX reductions are sufficiently large--large enough to 
become NOX-limited.
    The primary NAAQS for ozone, established in 2015 and retained in 
2020, is an 8-hour standard with a level of 0.07 ppm.\71\ EPA announced 
that it will reconsider the decision to retain the ozone NAAQS.\72\ The 
EPA is also implementing the previous 8-hour ozone primary standard, 
set in 2008, at a level of 0.075 ppm. As of August 31, 2022, there were 
34 ozone nonattainment areas for the 2008 ozone NAAQS, composed of 141 
full or partial counties, with a population of more than 90 million, 
and 49 ozone nonattainment areas for the 2015 ozone NAAQS, composed of 
212 full or partial counties, with a population of more than 125 
million. In total, there are currently, as of August 31, 2022, 57 ozone 
nonattainment areas with a population of more than 130 million 
people.\73\
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    \71\ https://www.epa.gov/ground-level-ozone-pollution/ozone-national-ambient-air-quality-standards-naaqs.
    \72\ https://www.epa.gov/ground-level-ozone-pollution/epa-reconsider-previous-administrations-decision-retain-2015-ozone.
    \73\ The population total is calculated by summing, without 
double counting, the 2008 and 2015 ozone nonattainment populations 
contained in the Criteria Pollutant Nonattainment Summary report 
(https://www.epa.gov/green-book/green-book-data-download).
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    States with ozone nonattainment areas are required to take action 
to bring those areas into attainment. The attainment date assigned to 
an ozone nonattainment area is based on the area's classification. The 
attainment dates for areas designated nonattainment for the 2008 8-hour 
ozone NAAQS are in the 2015 to 2032 timeframe, depending on the 
severity of the problem in each area. Attainment dates for areas 
designated nonattainment for the 2015 ozone NAAQS are in the 2021 to 
2038 timeframe, again depending on the severity of the problem in each 
area.\74\ The final NOX standards will take effect starting 
in MY 2027 and will assist areas with attaining the NAAQS and may 
relieve areas with already stringent local regulations from some of the 
burden associated with adopting additional local controls.\75\ The rule 
will also provide assistance to counties with ambient concentrations 
near the level of the NAAQS who are working to ensure long-term 
attainment or maintenance of the NAAQS.
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    \74\ https://www.epa.gov/ground-level-ozone-pollution/ozone-naaqs-timelines.
    \75\ While not quantified in the air quality modeling analysis 
for this rule, elements of the Averaging, Banking, and Trading (ABT) 
program could encourage manufacturers to introduce new emission 
control technologies prior to the 2027 model year, which may help to 
accelerate some emission reductions of the final rule (See Preamble 
Section IV.G for more details on the ABT program in the final rule). 
In RIA Chapter 5.5 we also include a sensitivity analysis that shows 
allowing manufacturers to generate NOX emissions credits 
by meeting requirements of the final rule one model year before 
required would lead to meaningful, additional reductions in 
NOX emissions in the early years of the program compared 
to the emissions reductions expected from the final rule (see 
preamble Section IV.G.7 and RIA Chapter 5.5 for additional details).
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2. Particulate Matter
    Particulate matter (PM) is a complex mixture of solid particles and 
liquid droplets distributed among numerous atmospheric gases which 
interact with solid and liquid phases. Particles in the atmosphere 
range in size from less than 0.01 to more than 10 micrometers ([mu]m) 
in diameter.\76\ Atmospheric particles can be grouped into several 
classes according to their aerodynamic diameter and physical sizes. 
Generally, the three broad classes of particles include ultrafine 
particles (UFPs, generally considered as particles with a diameter less 
than or equal to 0.1 [mu]m [typically based on physical size, thermal 
diffusivity or electrical mobility]), ``fine'' particles 
(PM2.5; particles with a nominal mean aerodynamic diameter 
less than or equal to 2.5 [mu]m), and ``thoracic'' particles 
(PM10; particles with a nominal mean aerodynamic diameter 
less than or equal to 10 [mu]m). Particles that fall within the size 
range between PM2.5 and PM10, are referred to as 
``thoracic coarse particles'' (PM10-2.5, 
particles with a nominal mean aerodynamic diameter greater than 2.5 
[mu]m and less than or equal to 10 [mu]m). EPA currently has NAAQS for 
PM2.5 and PM10.\77\
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    \76\ U.S. EPA. Policy Assessment (PA) for the Review of the 
National Ambient Air Quality Standards for Particulate Matter (Final 
Report, 2020). U.S. Environmental Protection Agency, Washington, DC, 
EPA/452/R-20/002, 2020.
    \77\ Regulatory definitions of PM size fractions, and 
information on reference and equivalent methods for measuring PM in 
ambient air, are provided in 40 CFR parts 50, 53, and 58. With 
regard to NAAQS which provide protection against health and welfare 
effects, the 24-hour PM10 standard provides protection 
against effects associated with short-term exposure to thoracic 
coarse particles (i.e., PM10-2.5).
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    Most particles are found in the lower troposphere, where they can 
have residence times ranging from a few hours to weeks. Particles are 
removed from the atmosphere by wet deposition, such as when they are 
carried by rain or snow, or by dry deposition, when particles settle 
out of suspension due to gravity. Atmospheric lifetimes are generally 
longest for PM2.5, which often remains in the atmosphere for 
days to weeks before being removed by wet or dry deposition.\78\ In 
contrast,

[[Page 4315]]

atmospheric lifetimes for UFP and PM10-2.5 are 
shorter. Within hours, UFP can undergo coagulation and condensation 
that lead to formation of larger particles, or can be removed from the 
atmosphere by evaporation, deposition, or reactions with other 
atmospheric components. PM10-2.5 are also 
generally removed from the atmosphere within hours, through wet or dry 
deposition.\79\
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    \78\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019. Table 2-
1.
    \79\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019. Table 2-
1.
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    Particulate matter consists of both primary and secondary 
particles. Primary particles are emitted directly from sources, such as 
combustion-related activities (e.g., industrial activities, motor 
vehicle operation, biomass burning), while secondary particles are 
formed through atmospheric chemical reactions of gaseous precursors 
(e.g., sulfur oxides (SOX), NOX, and VOCs).
    There are two primary NAAQS for PM2.5: An annual 
standard (12.0 micrograms per cubic meter ([mu]g/m\3\)) and a 24-hour 
standard (35 [mu]g/m\3\), and there are two secondary NAAQS for 
PM2.5: An annual standard (15.0 [mu]g/m\3\) and a 24-hour 
standard (35 [mu]g/m\3\). The initial PM2.5 standards were 
set in 1997 and revisions to the standards were finalized in 2006 and 
in December 2012 and then retained in 2020. On June 10, 2021, EPA 
announced that it will reconsider the decision to retain the PM 
NAAQS.\80\
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    \80\ https://www.epa.gov/pm-pollution/national-ambient-air-quality-standards-naaqs-pm.
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    There are many areas of the country that are currently in 
nonattainment for the annual and 24-hour primary PM2.5 
NAAQS. As of August 31, 2022, more than 19 million people lived in the 
4 areas that are designated as nonattainment for the 1997 
PM2.5 NAAQS. Also, as of August 31, 2022, more than 31 
million people lived in the 14 areas that are designated as 
nonattainment for the 2006 PM2.5 NAAQS and more than 20 
million people lived in the 5 areas designated as nonattainment for the 
2012 PM2.5 NAAQS. In total, there are currently 15 
PM2.5 nonattainment areas with a population of more than 32 
million people.\81\ The final NOX standards will take effect 
in MY 2027 and will assist areas with attaining the NAAQS and may 
relieve areas with already stringent local regulations from some of the 
burden associated with adopting additional local controls.\82\ The rule 
will also assist counties with ambient concentrations near the level of 
the NAAQS who are working to ensure long-term attainment or maintenance 
of the PM2.5 NAAQS.
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    \81\ The population total is calculated by summing, without 
double counting, the 1997, 2006 and 2012 PM2.5 
nonattainment populations contained in the Criteria Pollutant 
Nonattainment Summary report (https://www.epa.gov/green-book/green-book-data-download).
    \82\ While not quantified in the air quality modeling analysis 
for this rule, elements of the Averaging, Banking, and Trading (ABT) 
program could encourage manufacturers to introduce new emission 
control technologies prior to the 2027 model year, which may help to 
accelerate some emission reductions of the final rule (See Preamble 
Section IV.G for more details on the ABT program in the final rule).
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3. Nitrogen Oxides
    Oxides of nitrogen (NOX) refers to nitric oxide (NO) and 
nitrogen dioxide (NO2). Most NO2 is formed in the 
air through the oxidation of NO emitted when fuel is burned at a high 
temperature. NO2 is a criteria pollutant, regulated for its 
adverse effects on public health and the environment, and highway 
vehicles are an important contributor to NO2 emissions. 
NOX, along with VOCs, are the two major precursors of ozone 
and NOX is also a major contributor to secondary 
PM2.5 formation. There are two primary NAAQS for 
NO2: An annual standard (53 ppb) and a 1-hour standard (100 
ppb).\83\ In 2010, EPA established requirements for monitoring 
NO2 near roadways expected to have the highest 
concentrations within large cities. Monitoring within this near-roadway 
network began in 2014, with additional sites deployed in the following 
years. At present, there are no nonattainment areas for NO2.
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    \83\ The statistical form of the 1-hour NAAQS for NO2 
is the 3-year average of the yearly distribution of 1-hour daily 
maximum concentrations.
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4. Carbon Monoxide
    Carbon monoxide (CO) is a colorless, odorless gas emitted from 
combustion processes. Nationally, particularly in urban areas, the 
majority of CO emissions to ambient air come from mobile sources.\84\ 
There are two primary NAAQS for CO: An 8-hour standard (9 ppm) and a 1-
hour standard (35 ppm). There are currently no CO nonattainment areas; 
as of September 27, 2010, all CO nonattainment areas have been 
redesignated to attainment. The past designations were based on the 
existing community-wide monitoring network. EPA made an addition to the 
ambient air monitoring requirements for CO during the 2011 NAAQS 
review. Those new requirements called for CO monitors to be operated 
near roads in Core Based Statistical Areas (CBSAs) of 1 million or more 
persons, in addition to the existing community-based network (76 FR 
54294, August 31, 2011).
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    \84\ U.S. EPA, (2010). Integrated Science Assessment for Carbon 
Monoxide (Final Report). U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-09/019F, 2010. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=218686. See Section 2.1.
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5. Diesel Exhaust
    Diesel exhaust is a complex mixture composed of particulate matter, 
carbon dioxide, oxygen, nitrogen, water vapor, carbon monoxide, 
nitrogen compounds, sulfur compounds and numerous low-molecular-weight 
hydrocarbons. A number of these gaseous hydrocarbon components are 
individually known to be toxic, including aldehydes, benzene and 1,3-
butadiene. The diesel particulate matter present in diesel exhaust 
consists mostly of fine particles (<2.5 [mu]m), of which a significant 
fraction is ultrafine particles (<0.1 [mu]m). These particles have a 
large surface area which makes them an excellent medium for adsorbing 
organics and their small size makes them highly respirable. Many of the 
organic compounds present in the gases and on the particles, such as 
polycyclic organic matter, are individually known to have mutagenic and 
carcinogenic properties.
    Diesel exhaust varies significantly in chemical composition and 
particle sizes between different engine types (heavy-duty, light-duty), 
engine operating conditions (idle, acceleration, deceleration), and 
fuel formulations (high/low sulfur fuel). Also, there are emissions 
differences between on-road and nonroad engines because the nonroad 
engines are generally of older technology. After being emitted in the 
engine exhaust, diesel exhaust undergoes dilution as well as chemical 
and physical changes in the atmosphere. The lifetime of the components 
present in diesel exhaust ranges from seconds to days.
    Because diesel particulate matter (DPM) is part of overall ambient 
PM, varies considerably in composition, and lacks distinct chemical 
markers that enable it to be easily distinguished from overall primary 
PM, we do not have direct measurements of DPM in the ambient air.\85\ 
DPM concentrations are

[[Page 4316]]

estimated using ambient air quality modeling based on DPM emission 
inventories. DPM emission inventories are computed as the exhaust PM 
emissions from mobile sources combusting diesel or residual oil fuel. 
DPM concentrations were estimated as part of the 2018 national Air 
Toxics Screening Assessment (AirToxScreen).\86\ Areas with high 
concentrations are clustered in the Northeast and Great Lake States, 
with a smaller number of higher concentration locations in Western 
states. The highest impacts occur in major urban cores, and are also 
distributed throughout the rest of the United States near high truck 
traffic, coasts with marine diesel activity, construction sites, and 
rail facilities. Approximately half of the average ambient DPM 
concentration in the United States can be attributed to heavy-duty 
diesel engines, with the remainder attributable to nonroad engines.
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    \85\ DPM in exhaust from a high-load, high-speed engine (e.g., 
heavy-duty truck engines) without aftertreatment such as a diesel 
particle filter (DPM) is mostly made of ``soot,'' consisting of 
elemental/black carbon (EC/BC), some organic material, and trace 
elements. At low loads, DPM in high-speed engine exhaust is mostly 
made of organic carbon (OC), with considerably less EC/BC. Low-speed 
diesel engines' (e.g., large marine engines) exhaust PM is comprised 
of more sulfate and less EC/BC, with OC contributing as well.
    \86\ U.S. EPA (2022) Technical Support Document EPA Air Toxics 
Screening Assessment. 2018AirToxScreen TSD. https://www.epa.gov/AirToxScreen/airtoxscreen-technical-support-document.
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6. Air Toxics
    The most recent available data indicate that millions of Americans 
live in areas where air toxics pose potential health concerns.\87\ The 
levels of air toxics to which people are exposed vary depending on 
where people live and work and the kinds of activities in which they 
engage, as discussed in detail in EPA's 2007 Mobile Source Air Toxics 
Rule.\88\ According to EPA's Air Toxics Screening Assessment 
(AirToxScreen) for 2018, mobile sources were responsible for 40 percent 
of outdoor anthropogenic toxic emissions and were the largest 
contributor to national average cancer and noncancer risk from directly 
emitted pollutants.89 90 Mobile sources are also significant 
contributors to precursor emissions which react to form air toxics.\91\ 
Formaldehyde is the largest contributor to cancer risk of all 71 
pollutants quantitatively assessed in the 2018 AirToxScreen. Mobile 
sources were responsible for 26 percent of primary anthropogenic 
emissions of this pollutant in 2018 and are significant contributors to 
formaldehyde precursor emissions. Benzene is also a large contributor 
to cancer risk, and mobile sources account for about 60 percent of 
average exposure to ambient concentrations.
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    \87\ U.S. EPA (2022) Technical Support Document EPA Air Toxics 
Screening Assessment. 2017AirToxScreen TSD. https://www.epa.gov/system/files/documents/2022-03/airtoxscreen_2017tsd.pdf.
    \88\ U.S. Environmental Protection Agency (2007). Control of 
Hazardous Air Pollutants from Mobile Sources; Final Rule. 72 FR 
8434, February 26, 2007.
    \89\ U.S. EPA. (2022) Air Toxics Screening Assessment. https://www.epa.gov/AirToxScreen/2018-airtoxscreen-assessment-results.
    \90\ AirToxScreen also includes estimates of risk attributable 
to background concentrations, which includes contributions from 
long-range transport, persistent air toxics, and natural sources; as 
well as secondary concentrations, where toxics are formed via 
secondary formation. Mobile sources substantially contribute to 
long-range transport and secondarily formed air toxics.
    \91\ Rich Cook, Sharon Phillips, Madeleine Strum, Alison Eyth & 
James Thurman (2020): Contribution of mobile sources to secondary 
formation of carbonyl compounds, Journal of the Air & Waste 
Management Association, DOI: 10.1080/10962247.2020.1813839.
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B. Health Effects Associated With Exposure to Pollutants Impacted by 
This Rule

    Heavy-duty engines emit pollutants that contribute to ambient 
concentrations of ozone, PM, NO2, CO, and air toxics. This 
section of the preamble discusses the health effects associated with 
exposure to these pollutants.
    Additionally, because children have increased vulnerability and 
susceptibility for adverse health effects related to air pollution 
exposures, EPA's findings regarding adverse effects for children 
related to exposure to pollutants that are impacted by this rule are 
noted in this section. The increased vulnerability and susceptibility 
of children to air pollution exposures may arise because infants and 
children generally breathe more relative to their size than adults do, 
and consequently may be exposed to relatively higher amounts of air 
pollution.\92\ Children also tend to breathe through their mouths more 
than adults and their nasal passages are less effective at removing 
pollutants, which leads to greater lung deposition of some pollutants, 
such as PM.93 94 Furthermore, air pollutants may pose health 
risks specific to children because children's bodies are still 
developing.\95\ For example, during periods of rapid growth such as 
fetal development, infancy, and puberty, their developing systems and 
organs may be more easily harmed.96 97 EPA's America's 
Children and the Environment is a tool which presents national trends 
on air pollutants and other contaminants and environmental health of 
children.\98\
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    \92\ EPA (2009) Metabolically-derived ventilation rates: A 
revised approach based upon oxygen consumption rates. Washington, 
DC: Office of Research and Development. EPA/600/R-06/129F. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=202543.
    \93\ U.S. EPA Integrated Science Assessment for Particulate 
Matter (Final Report, 2019). U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-19/188, 2019. Chapter 4 ``Overall 
Conclusions'' p. 4-1.
    \94\ Foos, B.; Marty, M.; Schwartz, J.; Bennet, W.; Moya, J.; 
Jarabek, A.M.; Salmon, A.G. (2008) Focusing on children's inhalation 
dosimetry and health effects for risk assessment: An introduction. J 
Toxicol Environ Health 71A: 149-165.
    \95\ Children's environmental health includes conception, 
infancy, early childhood and through adolescence until 21 years of 
age as described in the EPA Memorandum: Issuance of EPA's 2021 
Policy on Children's Health. October 5, 2021. Available at https://www.epa.gov/system/files/documents/2021-10/2021-policy-on-childrens-health.pdf.
    \96\ EPA (2006) A Framework for Assessing Health Risks of 
Environmental Exposures to Children. EPA, Washington, DC, EPA/600/R-
05/093F, 2006.
    \97\ U.S. Environmental Protection Agency. (2005). Supplemental 
guidance for assessing susceptibility from early-life exposure to 
carcinogens. Washington, DC: Risk Assessment Forum. EPA/630/R-03/
003F. https://www3.epa.gov/airtoxics/childrens_supplement_final.pdf.
    \98\ U.S. EPA. America's Children and the Environment. Available 
at: https://www.epa.gov/americaschildrenenvironment.
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    Information on environmental effects associated with exposure to 
these pollutants is included in Section II.C, and information on 
environmental justice is included in Section VII.H. Information on 
emission reductions and air quality impacts from this rule are included 
in Section VI and VII.
1. Ozone
    This section provides a summary of the health effects associated 
with exposure to ambient concentrations of ozone.\99\ The information 
in this section is based on the information and conclusions in the 
April 2020 Integrated Science Assessment for Ozone (Ozone ISA).\100\ 
The Ozone ISA concludes that human exposures to ambient concentrations 
of ozone are associated with a number of adverse health effects and 
characterizes the weight of evidence for these health effects.\101\ The 
following discussion highlights the Ozone ISA's

[[Page 4317]]

conclusions pertaining to health effects associated with both short-
term and long-term periods of exposure to ozone.
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    \99\ Human exposure to ozone varies over time due to changes in 
ambient ozone concentration and because people move between 
locations which have notably different ozone concentrations. Also, 
the amount of ozone delivered to the lung is influenced not only by 
the ambient concentrations but also by the breathing route and rate.
    \100\ U.S. EPA. Integrated Science Assessment (ISA) for Ozone 
and Related Photochemical Oxidants (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-20/012, 
2020.
    \101\ The ISA evaluates evidence and draws conclusions on the 
causal relationship between relevant pollutant exposures and health 
effects, assigning one of five ``weight of evidence'' 
determinations: causal relationship, likely to be a causal 
relationship, suggestive of a causal relationship, inadequate to 
infer a causal relationship, and not likely to be a causal 
relationship. For more information on these levels of evidence, 
please refer to Table II in the Preamble of the ISA.
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    For short-term exposure to ozone, the Ozone ISA concludes that 
respiratory effects, including lung function decrements, pulmonary 
inflammation, exacerbation of asthma, respiratory-related hospital 
admissions, and mortality, are causally associated with ozone exposure. 
It also concludes that metabolic effects, including metabolic syndrome 
(i.e., changes in insulin or glucose levels, cholesterol levels, 
obesity, and blood pressure) and complications due to diabetes are 
likely to be causally associated with short-term exposure to ozone. The 
evidence is also suggestive of a causal relationship between short-term 
exposure to ozone and cardiovascular effects, central nervous system 
effects, and total mortality.
    For long-term exposure to ozone, the Ozone ISA concludes that 
respiratory effects, including new onset asthma, pulmonary 
inflammation, and injury, are likely to be causally related with ozone 
exposure. The Ozone ISA characterizes the evidence as suggestive of a 
causal relationship for associations between long-term ozone exposure 
and cardiovascular effects, metabolic effects, reproductive and 
developmental effects, central nervous system effects, and total 
mortality. The evidence is inadequate to infer a causal relationship 
between chronic ozone exposure and increased risk of cancer.
    Finally, interindividual variation in human responses to ozone 
exposure can result in some groups being at increased risk for 
detrimental effects in response to exposure. In addition, some groups 
are at increased risk of exposure due to their activities, such as 
outdoor workers and children. The Ozone ISA identified several groups 
that are at increased risk for ozone-related health effects. These 
groups are people with asthma, children and older adults, individuals 
with reduced intake of certain nutrients (i.e., Vitamins C and E), 
outdoor workers, and individuals having certain genetic variants 
related to oxidative metabolism or inflammation. Ozone exposure during 
childhood can have lasting effects through adulthood. Such effects 
include altered function of the respiratory and immune systems. 
Children absorb higher doses (normalized to lung surface area) of 
ambient ozone, compared to adults, due to their increased time spent 
outdoors, higher ventilation rates relative to body size, and a 
tendency to breathe a greater fraction of air through the mouth. 
Children also have a higher asthma prevalence compared to adults. 
Recent epidemiologic studies provide generally consistent evidence that 
long-term ozone exposure is associated with the development of asthma 
in children. Studies comparing age groups reported higher magnitude 
associations for short-term ozone exposure and respiratory hospital 
admissions and emergency room visits among children than among adults. 
Panel studies also provide support for experimental studies with 
consistent associations between short-term ozone exposure and lung 
function and pulmonary inflammation in healthy children. Additional 
children's vulnerability and susceptibility factors are listed in 
Section XII of this preamble.
2. Particulate Matter
    Scientific evidence spanning animal toxicological, controlled human 
exposure, and epidemiologic studies shows that exposure to ambient PM 
is associated with a broad range of health effects. These health 
effects are discussed in detail in the Integrated Science Assessment 
for Particulate Matter, which was finalized in December 2019 (PM ISA). 
In addition, there is a more targeted evaluation of studies published 
since the literature cutoff date of the 2019 p.m. ISA in the Supplement 
to the Integrated Science Assessment for PM 
(Supplement).102 103 The PM ISA characterizes the causal 
nature of relationships between PM exposure and broad health categories 
(e.g., cardiovascular effects, respiratory effects, etc.) using a 
weight-of-evidence approach.\104\ Within this characterization, the PM 
ISA summarizes the health effects evidence for short-term (i.e., hours 
up to one month) and long-term (i.e., one month to years) exposures to 
PM2.5, PM10-2.5, and 
ultrafine particles, and concludes that exposures to ambient 
PM2.5 are associated with a number of adverse health 
effects. The following discussion highlights the PM ISA's conclusions, 
and summarizes additional information from the Supplement where 
appropriate, pertaining to the health effects evidence for both short- 
and long-term PM exposures. Further discussion of PM-related health 
effects can also be found in the 2022 Policy Assessment for the review 
of the PM NAAQS.\105\
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    \102\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \103\ U.S. EPA. Supplement to the 2019 Integrated Science 
Assessment for Particulate Matter (Final Report, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/635/R-22/028, 
2022.
    \104\ The causal framework draws upon the assessment and 
integration of evidence from across scientific disciplines, spanning 
atmospheric chemistry, exposure, dosimetry and health effects 
studies (i.e., epidemiologic, controlled human exposure, and animal 
toxicological studies), and assess the related uncertainties and 
limitations that ultimately influence our understanding of the 
evidence. This framework employs a five-level hierarchy that 
classifies the overall weight-of-evidence with respect to the causal 
nature of relationships between criteria pollutant exposures and 
health and welfare effects using the following categorizations: 
causal relationship; likely to be causal relationship; suggestive 
of, but not sufficient to infer, a causal relationship; inadequate 
to infer the presence or absence of a causal relationship; and not 
likely to be a causal relationship (U.S. EPA. (2019). Integrated 
Science Assessment for Particulate Matter (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-19/188, 
Section P. 3.2.3).
    \105\ U.S. EPA. Policy Assessment (PA) for the Reconsideration 
of the National Ambient Air Quality Standards for Particulate Matter 
(Final Report, 2022). U.S. Environmental Protection Agency, 
Washington, DC, EPA-452/R-22-004, 2022.
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    EPA has concluded that recent evidence in combination with evidence 
evaluated in the 2009 p.m. ISA supports a ``causal relationship'' 
between both long- and short-term exposures to PM2.5 and 
premature mortality and cardiovascular effects and a ``likely to be 
causal relationship'' between long- and short-term PM2.5 
exposures and respiratory effects.\106\ Additionally, recent 
experimental and epidemiologic studies provide evidence supporting a 
``likely to be causal relationship'' between long-term PM2.5 
exposure and nervous system effects, and long-term PM2.5 
exposure and cancer. Because of remaining uncertainties and limitations 
in the evidence base, EPA determined a ``suggestive of, but not 
sufficient to infer, a causal relationship'' for long-term 
PM2.5 exposure and reproductive and developmental effects 
(i.e., male/female reproduction and fertility; pregnancy and birth 
outcomes), long- and short-term exposures and metabolic effects, and 
short-term exposure and nervous system effects.
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    \106\ U.S. EPA. (2009). Integrated Science Assessment for 
Particulate Matter (Final Report). U.S. Environmental Protection 
Agency, Washington, DC, EPA/600/R-08/139F.
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    As discussed extensively in the 2019 p.m. ISA and the Supplement, 
recent studies continue to support a ``causal relationship'' between 
short- and long-term PM2.5 exposures and 
mortality.107 108 For short-term PM2.5 exposure, 
multi-city studies, in combination with single- and multi-city studies 
evaluated in the 2009 p.m. ISA,

[[Page 4318]]

provide evidence of consistent, positive associations across studies 
conducted in different geographic locations, populations with different 
demographic characteristics, and studies using different exposure 
assignment techniques. Additionally, the consistent and coherent 
evidence across scientific disciplines for cardiovascular morbidity, 
particularly ischemic events and heart failure, and to a lesser degree 
for respiratory morbidity, including exacerbations of chronic 
obstructive pulmonary disease (COPD) and asthma, provide biological 
plausibility for cause-specific mortality and ultimately total 
mortality. Recent epidemiologic studies evaluated in the Supplement, 
including studies that employed alternative methods for confounder 
control, provide additional support to the evidence base that 
contributed to the 2019 p.m. ISA conclusion for short-term 
PM2.5 exposure and mortality.
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    \107\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \108\ U.S. EPA. Supplement to the 2019 Integrated Science 
Assessment for Particulate Matter (Final Report, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/635/R-22/028, 
2022.
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    The 2019 p.m. ISA concluded a ``causal relationship'' between long-
term PM2.5 exposure and mortality. In addition to reanalyses 
and extensions of the American Cancer Society (ACS) and Harvard Six 
Cities (HSC) cohorts, multiple new cohort studies conducted in the 
United States and Canada consisting of people employed in a specific 
job (e.g., teacher, nurse), and that apply different exposure 
assignment techniques, provide evidence of positive associations 
between long-term PM2.5 exposure and mortality. Biological 
plausibility for mortality due to long-term PM2.5 exposure 
is provided by the coherence of effects across scientific disciplines 
for cardiovascular morbidity, particularly for coronary heart disease, 
stroke, and atherosclerosis, and for respiratory morbidity, 
particularly for the development of COPD. Additionally, recent studies 
provide evidence indicating that as long-term PM2.5 
concentrations decrease there is an increase in life expectancy. Recent 
cohort studies evaluated in the Supplement, as well as epidemiologic 
studies that conducted accountability analyses or employed alternative 
methods for confounder controls, support and extend the evidence base 
that contributed to the 2019 p.m. ISA conclusion for long-term 
PM2.5 exposure and mortality.
    A large body of studies examining both short- and long-term 
PM2.5 exposure and cardiovascular effects builds on the 
evidence base evaluated in the 2009 p.m. ISA. The strongest evidence 
for cardiovascular effects in response to short-term PM2.5 
exposures is for ischemic heart disease and heart failure. The evidence 
for short-term PM2.5 exposure and cardiovascular effects is 
coherent across scientific disciplines and supports a continuum of 
effects ranging from subtle changes in indicators of cardiovascular 
health to serious clinical events, such as increased emergency 
department visits and hospital admissions due to cardiovascular disease 
and cardiovascular mortality. For long-term PM2.5 exposure, 
there is strong and consistent epidemiologic evidence of a relationship 
with cardiovascular mortality. This evidence is supported by 
epidemiologic and animal toxicological studies demonstrating a range of 
cardiovascular effects including coronary heart disease, stroke, 
impaired heart function, and subclinical markers (e.g., coronary artery 
calcification, atherosclerotic plaque progression), which collectively 
provide coherence and biological plausibility. Recent epidemiologic 
studies evaluated in the Supplement, as well as studies that conducted 
accountability analyses or employed alternative methods for confounder 
control, support and extend the evidence base that contributed to the 
2019 p.m. ISA conclusion for both short- and long-term PM2.5 
exposure and cardiovascular effects.
    Studies evaluated in the 2019 p.m. ISA continue to provide evidence 
of a ``likely to be causal relationship'' between both short- and long-
term PM2.5 exposure and respiratory effects. Epidemiologic 
studies provide consistent evidence of a relationship between short-
term PM2.5 exposure and asthma exacerbation in children and 
COPD exacerbation in adults, as indicated by increases in emergency 
department visits and hospital admissions, which is supported by animal 
toxicological studies indicating worsening allergic airways disease and 
subclinical effects related to COPD. Epidemiologic studies also provide 
evidence of a relationship between short-term PM2.5 exposure 
and respiratory mortality. However, there is inconsistent evidence of 
respiratory effects, specifically lung function declines and pulmonary 
inflammation, in controlled human exposure studies. With respect to 
long term PM2.5 exposure, epidemiologic studies conducted in 
the United States and abroad provide evidence of a relationship with 
respiratory effects, including consistent changes in lung function and 
lung function growth rate, increased asthma incidence, asthma 
prevalence, and wheeze in children; acceleration of lung function 
decline in adults; and respiratory mortality. The epidemiologic 
evidence is supported by animal toxicological studies, which provide 
coherence and biological plausibility for a range of effects including 
impaired lung development, decrements in lung function growth, and 
asthma development.
    Since the 2009 p.m. ISA, a growing body of scientific evidence 
examined the relationship between long-term PM2.5 exposure 
and nervous system effects, resulting for the first time in a causality 
determination for this health effects category of a ``likely to be 
causal relationship.'' The strongest evidence for effects on the 
nervous system come from epidemiologic studies that consistently report 
cognitive decrements and reductions in brain volume in adults. The 
effects observed in epidemiologic studies in adults are supported by 
animal toxicological studies demonstrating effects on the brain of 
adult animals including inflammation, morphologic changes, and 
neurodegeneration of specific regions of the brain. There is more 
limited evidence for neurodevelopmental effects in children, with some 
studies reporting positive associations with autism spectrum disorder 
and others providing limited evidence of an association with cognitive 
function. While there is some evidence from animal toxicological 
studies indicating effects on the brain (i.e., inflammatory and 
morphological changes) to support a biologically plausible pathway for 
neurodevelopmental effects, epidemiologic studies are limited due to 
their lack of control for potential confounding by copollutants, the 
small number of studies conducted, and uncertainty regarding critical 
exposure windows.
    Building off the decades of research demonstrating mutagenicity, 
DNA damage, and other endpoints related to genotoxicity due to whole PM 
exposures, recent experimental and epidemiologic studies focusing 
specifically on PM2.5 provide evidence of a relationship 
between long-term PM2.5 exposure and cancer. Epidemiologic 
studies examining long-term PM2.5 exposure and lung cancer 
incidence and mortality provide evidence of generally positive 
associations in cohort studies spanning different populations, 
locations, and exposure assignment techniques. Additionally, there is 
evidence of positive associations with lung cancer incidence and 
mortality in analyses limited to never smokers. In addition, 
experimental and epidemiologic studies of genotoxicity, epigenetic 
effects, carcinogenic potential, and that PM2.5 exhibits 
several characteristics of

[[Page 4319]]

carcinogens provide biological plausibility for cancer development. 
This collective body of evidence contributed to the conclusion of a 
``likely to be causal relationship.''
    For the additional health effects categories evaluated for 
PM2.5 in the 2019 p.m. ISA, experimental and epidemiologic 
studies provide limited and/or inconsistent evidence of a relationship 
with PM2.5 exposure. As a result, the 2019 p.m. ISA 
concluded that the evidence is ``suggestive of, but not sufficient to 
infer a causal relationship'' for short-term PM2.5 exposure 
and metabolic effects and nervous system effects, and long-term 
PM2.5 exposures and metabolic effects as well as 
reproductive and developmental effects.
    In addition to evaluating the health effects attributed to short- 
and long-term exposure to PM2.5, the 2019 p.m. ISA also 
conducted an extensive evaluation as to whether specific components or 
sources of PM2.5 are more strongly related with health 
effects than PM2.5 mass. An evaluation of those studies 
resulted in the 2019 p.m. ISA concluding that ``many PM2.5 
components and sources are associated with many health effects, and the 
evidence does not indicate that any one source or component is 
consistently more strongly related to health effects than 
PM2.5 mass.'' \109\
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    \109\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
---------------------------------------------------------------------------

    For both PM10-2.5 and UFPs, for all health effects 
categories evaluated, the 2019 p.m. ISA concluded that the evidence was 
``suggestive of, but not sufficient to infer, a causal relationship'' 
or ``inadequate to determine the presence or absence of a causal 
relationship.'' For PM10-2.5, although a Federal Reference 
Method (FRM) was instituted in 2011 to measure PM10-2.5 
concentrations nationally, the causality determinations reflect that 
the same uncertainty identified in the 2009 p.m. ISA persists with 
respect to the method used to estimate PM10-2.5 
concentrations in epidemiologic studies. Specifically, across 
epidemiologic studies, different approaches are used to estimate 
PM10-2.5 concentrations (e.g., direct measurement of 
PM10-2.5, difference between PM10 and 
PM2.5 concentrations), and it remains unclear how well 
correlated PM10-2.5 concentrations are both spatially and 
temporally across the different methods used.
    For UFPs, which have often been defined as particles <0.1 [micro]m, 
the uncertainty in the evidence for the health effect categories 
evaluated across experimental and epidemiologic studies reflects the 
inconsistency in the exposure metric used (i.e., particle number 
concentration, surface area concentration, mass concentration) as well 
as the size fractions examined. In epidemiologic studies the size 
fraction examined can vary depending on the monitor used and exposure 
metric, with some studies examining number count over the entire 
particle size range, while experimental studies that use a particle 
concentrator often examine particles up to 0.3 [micro]m. Additionally, 
due to the lack of a monitoring network, there is limited information 
on the spatial and temporal variability of UFPs within the United 
States, as well as population exposures to UFPs, which adds uncertainty 
to epidemiologic study results.
    The 2019 p.m. ISA cites extensive evidence indicating that ``both 
the general population as well as specific populations and life stages 
are at risk for PM2.5-related health effects.'' \110\ For 
example, in support of its ``causal'' and ``likely to be causal'' 
determinations, the ISA cites substantial evidence for (1) PM-related 
mortality and cardiovascular effects in older adults; (2) PM-related 
cardiovascular effects in people with pre-existing cardiovascular 
disease; (3) PM-related respiratory effects in people with pre-existing 
respiratory disease, particularly asthma exacerbations in children; and 
(4) PM-related impairments in lung function growth and asthma 
development in children. The ISA additionally notes that stratified 
analyses (i.e., analyses that directly compare PM-related health 
effects across groups) provide strong evidence for racial and ethnic 
differences in PM2.5 exposures and in the risk of 
PM2.5-related health effects, specifically within Hispanic 
and non-Hispanic Black populations, with some evidence of increased 
risk for populations of low socioeconomic status. Recent studies 
evaluated in the Supplement support the conclusion of the 2019 p.m. ISA 
with respect to disparities in both PM2.5 exposure and 
health risk by race and ethnicity and provide additional support for 
disparities for populations of lower socioeconomic status.\111\ 
Additionally, evidence spanning epidemiologic studies that conducted 
stratified analyses, experimental studies focusing on animal models of 
disease or individuals with pre-existing disease, dosimetry studies, as 
well as studies focusing on differential exposure suggest that 
populations with pre-existing cardiovascular or respiratory disease, 
populations that are overweight or obese, populations that have 
particular genetic variants, and current/former smokers could be at 
increased risk for adverse PM2.5-related health effects. The 
2022 Policy Assessment for the review of the PM NAAQS also highlights 
that factors that may contribute to increased risk of PM2.5-
related health effects include lifestage (children and older adults), 
pre-existing diseases (cardiovascular disease and respiratory disease), 
race/ethnicity, and socioeconomic status.\112\
---------------------------------------------------------------------------

    \110\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \111\ U.S. EPA. Supplement to the 2019 Integrated Science 
Assessment for Particulate Matter (Final Report, 2022). U.S. 
Environmental Protection Agency, Washington, DC, EPA/635/R-22/028, 
2022.
    \112\ U.S. EPA. Policy Assessment (PA) for the Reconsideration 
of the National Ambient Air Quality Standards for Particulate Matter 
(Final Report, 2022). U.S. Environmental Protection Agency, 
Washington, DC, EPA-452/R-22-004, 2022, p. 3-53.
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3. Nitrogen Oxides
    The most recent review of the health effects of oxides of nitrogen 
completed by EPA can be found in the 2016 Integrated Science Assessment 
for Oxides of Nitrogen--Health Criteria (ISA for Oxides of 
Nitrogen).\113\ The primary source of NO2 is motor vehicle 
emissions, and ambient NO2 concentrations tend to be highly 
correlated with other traffic-related pollutants. Thus, a key issue in 
characterizing the causality of NO2-health effect 
relationships consists of evaluating the extent to which studies 
supported an effect of NO2 that is independent of other 
traffic-related pollutants. EPA concluded that the findings for asthma 
exacerbation integrated from epidemiologic and controlled human 
exposure studies provided evidence that is sufficient to infer a causal 
relationship between respiratory effects and short-term NO2 
exposure. The strongest evidence supporting an independent effect of 
NO2 exposure comes from controlled human exposure studies 
demonstrating increased airway responsiveness in individuals with 
asthma following ambient-relevant NO2 exposures. The 
coherence of this evidence with epidemiologic findings for asthma 
hospital admissions and emergency department visits as well as lung 
function decrements and increased pulmonary inflammation in children 
with asthma describe a plausible pathway by which NO2 
exposure can

[[Page 4320]]

cause an asthma exacerbation. The 2016 ISA for Oxides of Nitrogen also 
concluded that there is likely to be a causal relationship between 
long-term NO2 exposure and respiratory effects. This 
conclusion is based on new epidemiologic evidence for associations of 
NO2 with asthma development in children combined with 
biological plausibility from experimental studies.
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    \113\ U.S. EPA. Integrated Science Assessment for Oxides of 
Nitrogen--Health Criteria (2016 Final Report). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-15/068, 2016.
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    In evaluating a broader range of health effects, the 2016 ISA for 
Oxides of Nitrogen concluded that evidence is ``suggestive of, but not 
sufficient to infer, a causal relationship'' between short-term 
NO2 exposure and cardiovascular effects and mortality and 
between long-term NO2 exposure and cardiovascular effects 
and diabetes, birth outcomes, and cancer. In addition, the scientific 
evidence is inadequate (insufficient consistency of epidemiologic and 
toxicological evidence) to infer a causal relationship for long-term 
NO2 exposure with fertility, reproduction, and pregnancy, as 
well as with postnatal development. A key uncertainty in understanding 
the relationship between these non-respiratory health effects and 
short- or long-term exposure to NO2 is copollutant 
confounding, particularly by other roadway pollutants. The available 
evidence for non-respiratory health effects does not adequately address 
whether NO2 has an independent effect or whether it 
primarily represents effects related to other or a mixture of traffic-
related pollutants.
    The 2016 ISA for Oxides of Nitrogen concluded that people with 
asthma, children, and older adults are at increased risk for 
NO2-related health effects. In these groups and lifestages, 
NO2 is consistently related to larger effects on outcomes 
related to asthma exacerbation, for which there is confidence in the 
relationship with NO2 exposure.
4. Carbon Monoxide
    Information on the health effects of CO can be found in the January 
2010 Integrated Science Assessment for Carbon Monoxide (CO ISA).\114\ 
The CO ISA presents conclusions regarding the presence of causal 
relationships between CO exposure and categories of adverse health 
effects.\115\ This section provides a summary of the health effects 
associated with exposure to ambient concentrations of CO, along with 
the CO ISA conclusions.\116\
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    \114\ U.S. EPA, (2010). Integrated Science Assessment for Carbon 
Monoxide (Final Report). U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-09/019F, 2010. http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=218686.
    \115\ The ISA evaluates the health evidence associated with 
different health effects, assigning one of five ``weight of 
evidence'' determinations: causal relationship, likely to be a 
causal relationship, suggestive of a causal relationship, inadequate 
to infer a causal relationship, and not likely to be a causal 
relationship. For definitions of these levels of evidence, please 
refer to Section 1.6 of the ISA.
    \116\ Personal exposure includes contributions from many 
sources, and in many different environments. Total personal exposure 
to CO includes both ambient and non-ambient components; and both 
components may contribute to adverse health effects.
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    Controlled human exposure studies of subjects with coronary artery 
disease show a decrease in the time to onset of exercise-induced angina 
(chest pain) and electrocardiogram changes following CO exposure. In 
addition, epidemiologic studies observed associations between short-
term CO exposure and cardiovascular morbidity, particularly increased 
emergency room visits and hospital admissions for coronary heart 
disease (including ischemic heart disease, myocardial infarction, and 
angina). Some epidemiologic evidence is also available for increased 
hospital admissions and emergency room visits for congestive heart 
failure and cardiovascular disease as a whole. The CO ISA concludes 
that a causal relationship is likely to exist between short-term 
exposures to CO and cardiovascular morbidity. It also concludes that 
available data are inadequate to conclude that a causal relationship 
exists between long-term exposures to CO and cardiovascular morbidity.
    Animal studies show various neurological effects with in-utero CO 
exposure. Controlled human exposure studies report central nervous 
system and behavioral effects following low-level CO exposures, 
although the findings have not been consistent across all studies. The 
CO ISA concludes that the evidence is suggestive of a causal 
relationship with both short- and long-term exposure to CO and central 
nervous system effects.
    A number of studies cited in the CO ISA have evaluated the role of 
CO exposure in birth outcomes such as preterm birth or cardiac birth 
defects. There is limited epidemiologic evidence of a CO-induced effect 
on preterm births and birth defects, with weak evidence for a decrease 
in birth weight. Animal toxicological studies have found perinatal CO 
exposure to affect birth weight, as well as other developmental 
outcomes. The CO ISA concludes that the evidence is suggestive of a 
causal relationship between long-term exposures to CO and developmental 
effects and birth outcomes.
    Epidemiologic studies provide evidence of associations between 
short-term CO concentrations and respiratory morbidity such as changes 
in pulmonary function, respiratory symptoms, and hospital admissions. A 
limited number of epidemiologic studies considered copollutants such as 
ozone, SO2, and PM in two-pollutant models and found that CO 
risk estimates were generally robust, although this limited evidence 
makes it difficult to disentangle effects attributed to CO itself from 
those of the larger complex air pollution mixture. Controlled human 
exposure studies have not extensively evaluated the effect of CO on 
respiratory morbidity. Animal studies at levels of 50-100 ppm CO show 
preliminary evidence of altered pulmonary vascular remodeling and 
oxidative injury. The CO ISA concludes that the evidence is suggestive 
of a causal relationship between short-term CO exposure and respiratory 
morbidity, and inadequate to conclude that a causal relationship exists 
between long-term exposure and respiratory morbidity.
    Finally, the CO ISA concludes that the epidemiologic evidence is 
suggestive of a causal relationship between short-term concentrations 
of CO and mortality. Epidemiologic evidence suggests an association 
exists between short-term exposure to CO and mortality, but limited 
evidence is available to evaluate cause-specific mortality outcomes 
associated with CO exposure. In addition, the attenuation of CO risk 
estimates that was often observed in copollutant models contributes to 
the uncertainty as to whether CO is acting alone or as an indicator for 
other combustion-related pollutants. The CO ISA also concludes that 
there is not likely to be a causal relationship between relevant long-
term exposures to CO and mortality.
5. Diesel Exhaust
    In EPA's 2002 Diesel Health Assessment Document (Diesel HAD), 
exposure to diesel exhaust was classified as likely to be carcinogenic 
to humans by inhalation from environmental exposures, in accordance 
with the revised draft 1996/1999 EPA cancer 
guidelines.117 118 A number of

[[Page 4321]]

other agencies (National Institute for Occupational Safety and Health, 
the International Agency for Research on Cancer, the World Health 
Organization, California EPA, and the U.S. Department of Health and 
Human Services) made similar hazard classifications prior to 2002. EPA 
also concluded in the 2002 Diesel HAD that it was not possible to 
calculate a cancer unit risk for diesel exhaust due to limitations in 
the exposure data for the occupational groups or the absence of a dose-
response relationship.
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    \117\ U.S. EPA. (1999). Guidelines for Carcinogen Risk 
Assessment. Review Draft. NCEA-F-0644, July. Washington, DC: U.S. 
EPA. Retrieved on March 19, 2009 from http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=54932.
    \118\ U.S. EPA (2002). Health Assessment Document for Diesel 
Engine Exhaust. EPA/600/8-90/057F Office of research and 
Development, Washington, DC. Retrieved on March 17, 2009 from http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=29060. pp. 1-1 1-2.
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    In the absence of a cancer unit risk, the Diesel HAD sought to 
provide additional insight into the significance of the diesel exhaust 
cancer hazard by estimating possible ranges of risk that might be 
present in the population. An exploratory analysis was used to 
characterize a range of possible lung cancer risk. The outcome was that 
environmental risks of cancer from long-term diesel exhaust exposures 
could plausibly range from as low as 10-5 to as 
high as 10-3. Because of uncertainties, the 
analysis acknowledged that the risks could be lower than 
10-5, and a zero risk from diesel exhaust 
exposure could not be ruled out.
    Noncancer health effects of acute and chronic exposure to diesel 
exhaust emissions are also of concern to EPA. EPA derived a diesel 
exhaust reference concentration (RfC) from consideration of four well-
conducted chronic rat inhalation studies showing adverse pulmonary 
effects. The RfC is 5 [micro]g/m3 for diesel exhaust 
measured as diesel particulate matter. This RfC does not consider 
allergenic effects such as those associated with asthma or immunologic 
or the potential for cardiac effects. There was emerging evidence in 
2002, discussed in the Diesel HAD, that exposure to diesel exhaust can 
exacerbate these effects, but the exposure-response data were lacking 
at that time to derive an RfC based on these then-emerging 
considerations. The Diesel HAD states, ``With [diesel particulate 
matter] being a ubiquitous component of ambient PM, there is an 
uncertainty about the adequacy of the existing [diesel exhaust] 
noncancer database to identify all the pertinent [diesel exhaust]-
caused noncancer health hazards.'' The Diesel HAD also notes ``that 
acute exposure to [diesel exhaust] has been associated with irritation 
of the eye, nose, and throat, respiratory symptoms (cough and phlegm), 
and neurophysiological symptoms such as headache, lightheadedness, 
nausea, vomiting, and numbness or tingling of the extremities.'' The 
Diesel HAD notes that the cancer and noncancer hazard conclusions 
applied to the general use of diesel engines then on the market and as 
cleaner engines replace a substantial number of existing ones, the 
applicability of the conclusions would need to be reevaluated.
    It is important to note that the Diesel HAD also briefly summarizes 
health effects associated with ambient PM and discusses EPA's then-
annual PM2.5 NAAQS of 15 [micro]g/m3.\119\ There 
is a large and extensive body of human data showing a wide spectrum of 
adverse health effects associated with exposure to ambient PM, of which 
diesel exhaust is an important component. The PM2.5 NAAQS is 
designed to provide protection from the noncancer health effects and 
premature mortality attributed to exposure to PM2.5. The 
contribution of diesel PM to total ambient PM varies in different 
regions of the country and also, within a region, from one area to 
another. The contribution can be high in near-roadway environments, for 
example, or in other locations where diesel engine use is concentrated.
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    \119\ See Section II.A.2 for discussion of the current 
PM2.5 NAAQS standard.
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    Since 2002, several new studies have been published which continue 
to report increased lung cancer risk associated with occupational 
exposure to diesel exhaust from older engines. Of particular note since 
2011 are three new epidemiology studies that have examined lung cancer 
in occupational populations, for example, truck drivers, underground 
nonmetal miners, and other diesel motor-related occupations. These 
studies reported increased risk of lung cancer with exposure to diesel 
exhaust with evidence of positive exposure-response relationships to 
varying degrees.120 121 122 These newer studies (along with 
others that have appeared in the scientific literature) add to the 
evidence EPA evaluated in the 2002 Diesel HAD and further reinforce the 
concern that diesel exhaust exposure likely poses a lung cancer hazard. 
The findings from these newer studies do not necessarily apply to newer 
technology diesel engines (i.e., heavy-duty highway engines from 2007 
and later model years) since the newer engines have large reductions in 
the emission constituents compared to older technology diesel engines.
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    \120\ Garshick, Eric, Francine Laden, Jaime E. Hart, Mary E. 
Davis, Ellen A. Eisen, and Thomas J. Smith. 2012. Lung cancer and 
elemental carbon exposure in trucking industry workers. 
Environmental Health Perspectives 120(9): 1301-1306.
    \121\ Silverman, D.T., Samanic, C.M., Lubin, J.H., Blair, A.E., 
Stewart, P.A., Vermeulen, R., & Attfield, M.D. (2012). The diesel 
exhaust in miners study: a nested case-control study of lung cancer 
and diesel exhaust. Journal of the National Cancer Institute.
    \122\ Olsson, Ann C., et al. ``Exposure to diesel motor exhaust 
and lung cancer risk in a pooled analysis from case-control studies 
in Europe and Canada.'' American Journal of Respiratory and Critical 
Care Medicine 183.7 (2011): 941-948.
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    In light of the growing body of scientific literature evaluating 
the health effects of exposure to diesel exhaust, in June 2012 the 
World Health Organization's International Agency for Research on Cancer 
(IARC), a recognized international authority on the carcinogenic 
potential of chemicals and other agents, evaluated the full range of 
cancer-related health effects data for diesel engine exhaust. IARC 
concluded that diesel exhaust should be regarded as ``carcinogenic to 
humans.'' \123\ This designation was an update from its 1988 evaluation 
that considered the evidence to be indicative of a ``probable human 
carcinogen.''
---------------------------------------------------------------------------

    \123\ IARC [International Agency for Research on Cancer]. 
(2013). Diesel and gasoline engine exhausts and some nitroarenes. 
IARC Monographs Volume 105. [Online at http://monographs.iarc.fr/ENG/Monographs/vol105/index.php].
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6. Air Toxics
    Heavy-duty engine emissions contribute to ambient levels of air 
toxics that are known or suspected human or animal carcinogens, or that 
have noncancer health effects. These compounds include, but are not 
limited to, benzene, formaldehyde, acetaldehyde, and naphthalene. These 
compounds were identified as national or regional cancer risk drivers 
or contributors in the 2018 AirToxScreen Assessment and have 
significant inventory contributions from mobile 
sources.124 125 Chapter 4 of the RIA includes additional 
information on the health effects associated with exposure to each of 
these pollutants.
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    \124\ U.S. EPA (2022) Technical Support Document EPA Air Toxics 
Screening Assessment. 2017AirToxScreen TSD. https://www.epa.gov/system/files/documents/2022-03/airtoxscreen_2017tsd.pdf.
    \125\ U.S. EPA (2022) 2018 AirToxScreen Risk Drivers. https://www.epa.gov/AirToxScreen/airtoxscreen-risk-drivers.
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7. Exposure and Health Effects Associated With Traffic
    Locations in close proximity to major roadways generally have 
elevated concentrations of many air pollutants emitted from motor 
vehicles. Hundreds of studies have been published in peer-reviewed 
journals, concluding that concentrations of CO, CO2, NO, 
NO2, benzene, aldehydes, PM, black carbon, and many other 
compounds are elevated in ambient air within approximately

[[Page 4322]]

300-600 meters (about 1,000-2,000 feet) of major roadways. The highest 
concentrations of most pollutants emitted directly by motor vehicles 
are found at locations within 50 meters (about 165 feet) of the edge of 
a roadway's traffic lanes.
    A large-scale review of air quality measurements in the vicinity of 
major roadways between 1978 and 2008 concluded that the pollutants with 
the steepest concentration gradients in vicinities of roadways were CO, 
UFPs, metals, elemental carbon (EC), NO, NOX, and several 
VOCs.\126\ These pollutants showed a large reduction in concentrations 
within 100 meters downwind of the roadway. Pollutants that showed more 
gradual reductions with distance from roadways included benzene, 
NO2, PM2.5, and PM10. In reviewing the 
literature, Karner et al., (2010) reported that results varied based on 
the method of statistical analysis used to determine the gradient in 
pollutant concentration. More recent studies continue to show 
significant concentration gradients of traffic-related air pollution 
around major 
roads.127 128 129 130 131 132 133 134 135 136 
There is evidence that EPA's regulations for vehicles have lowered the 
near-road concentrations and gradients.\137\ Starting in 2010, EPA 
required through the NAAQS process that air quality monitors be placed 
near high-traffic roadways for determining concentrations of CO, 
NO2, and PM2.5 (in addition to those existing 
monitors located in neighborhoods and other locations farther away from 
pollution sources). The monitoring data for NO2 indicate 
that in urban areas, monitors near roadways often report the highest 
concentrations of NO2.\138\ More recent studies of traffic-
related air pollutants continue to report sharp gradients around 
roadways, particularly within several hundred meters.139 140
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    \126\ Karner, A.A.; Eisinger, D.S.; Niemeier, D.A. (2010). Near-
roadway air quality: synthesizing the findings from real-world data. 
Environ Sci Technol 44: 5334-5344.
    \127\ McDonald, B.C.; McBride, Z.C.; Martin, E.W.; Harley, R.A. 
(2014) High-resolution mapping of motor vehicle carbon dioxide 
emissions. J. Geophys. Res. Atmos.,119, 5283-5298, doi:10.1002/
2013JD021219.
    \128\ Kimbrough, S.; Baldauf, R.W.; Hagler, G.S.W.; Shores, 
R.C.; Mitchell, W.; Whitaker, D.A.; Croghan, C.W.; Vallero, D.A. 
(2013) Long-term continuous measurement of near-road air pollution 
in Las Vegas: seasonal variability in traffic emissions impact on 
air quality. Air Qual Atmos Health 6: 295-305. DOI 10.1007/s11869-
012-0171-x.
    \129\ Kimbrough, S.; Palma, T.; Baldauf, R.W. (2014) Analysis of 
mobile source air toxics (MSATs)--Near-road VOC and carbonyl 
concentrations. Journal of the Air & Waste Management Association, 
64:3, 349-359, DOI: 10.1080/10962247.2013.863814.
    \130\ Kimbrough, S.; Owen, R.C.; Snyder, M.; Richmond-Bryant, J. 
(2017) NO to NO2 Conversion Rate Analysis and 
Implications for Dispersion Model Chemistry Methods using Las Vegas, 
Nevada Near-Road Field Measurements. Atmos Environ 165: 23-24.
    \131\ Hilker, N.; Wang, J.W.; Jong, C-H.; Healy, R.M.; Sofowote, 
U.; Debosz, J.; Su, Y.; Noble, M.; Munoz, A.; Doerkson, G.; White, 
L.; Audette, C.; Herod, D.; Brook, J.R.; Evans, G.J. (2019) Traffic-
related air pollution near roadways: discerning local impacts from 
background. Atmos. Meas. Tech., 12, 5247-5261. https://doi.org/10.5194/amt-12-5247-2019.
    \132\ Grivas, G.; Stavroulas, I.; Liakakou, E.; Kaskaoutis, 
D.G.; Bougiatioti, A.; Paraskevopoulou, D.; Gerasopoulos, E.; 
Mihalopoulos, N. (2019) Measuring the spatial variability of black 
carbon in Athens during wintertime. Air Quality, Atmosphere & Health 
(2019) 12:1405-1417. https://doi.org/10.1007/s11869-019-00756-y.
    \133\ Apte, J.S.; Messier, K.P.; Gani, S.; Brauer, M.; 
Kirchstetter, T.W.; Lunden, M.M.; Marshall, J.D.; Portier, C.J.; 
Vermeulen, R.C.H.; Hamburg, S.P. (2017) High-Resolution Air 
Pollution Mapping with Google Street View Cars: Exploiting Big Data. 
Environ Sci Technol 51: 6999-7008. https://doi.org/10.1021/acs.est.7b00891.
    \134\ Dabek-Zlotorzynska, E.; Celo, V.; Ding, L.; Herod, D.; 
Jeong, C-H.; Evans, G.; Hilker, N. (2019) Characteristics and 
sources of PM2.5 and reactive gases near roadways in two 
metropolitan areas in Canada. Atmos Environ 218: 116980. https://doi.org/10.1016/j.atmosenv.2019.116980.
    \135\ Apte, J.S.; Messier, K.R.; Gani, S.; et al. (2017) High-
resolution air pollution mapping with Google Street View cars: 
exploiting big data. Environ Sci Technol 51: 6999-7018, [Online at 
https://doi.org/10.1021/acs.est.7b00891].
    \136\ Gu, P.; Li, H.Z.; Ye, Q.; et al. (2018) Intercity 
variability of particulate matter is driven by carbonaceous sources 
and correlated with land-use variables. Environ Sci Technol 52: 52: 
11545-11554. [Online at http://dx.doi.org/10.1021/acs.est.8b03833].
    \137\ Sarnat, J.A.; Russell, A.; Liang, D.; Moutinho, J.L.; 
Golan, R.; Weber, R.; Gao, D.; Sarnat, S.; Chang, H.H.; Greenwald, 
R.; Yu, T. (2018) Developing Multipollutant Exposure Indicators of 
Traffic Pollution: The Dorm Room Inhalation to Vehicle Emissions 
(DRIVE) Study. Health Effects Institute Research Report Number 196. 
[Online at: https://www.healtheffects.org/publication/developing-multipollutant-exposure-indicators-traffic-pollution-dorm-room-inhalation].
    \138\ Gantt, B; Owen, R.C.; Watkins, N. (2021) Characterizing 
nitrogen oxides and fine particulate matter near major highways in 
the United States using the National Near-road Monitoring Network. 
Environ Sci Technol 55: 2831-2838. [Online at https://doi.org/10.1021/acs.est.0c05851].
    \139\ Apte, J.S.; Messier, K.R.; Gani, S.; et al. (2017) High-
resolution air pollution mapping with Google Street View cars: 
exploiting big data. Environ Sci Technol 51: 6999-7018, [Online at 
https://doi.org/10.1021/acs.est.7b00891].
    \140\ Gu, P.; Li, H.Z.; Ye, Q.; et al. (2018) Intercity 
variability of particulate matter is driven by carbonaceous sources 
and correlated with land-use variables. Environ Sci Technol 52: 52: 
11545-11554. [Online at http://dx.doi.org/10.1021/acs.est.8b03833].
---------------------------------------------------------------------------

    For pollutants with relatively high background concentrations 
relative to near-road concentrations, detecting concentration gradients 
can be difficult. For example, many carbonyls have high background 
concentrations as a result of photochemical breakdown of precursors 
from many different organic compounds. However, several studies have 
measured carbonyls in multiple weather conditions and found higher 
concentrations of many carbonyls downwind of 
roadways.141 142 These findings suggest a substantial 
roadway source of these carbonyls.
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    \141\ Liu, W.; Zhang, J.; Kwon, J.l.; et l. (2006). 
Concentrations and source characteristics of airborne carbonyl 
compounds measured outside urban residences. J Air Waste Manage 
Assoc 56: 1196-1204.
    \142\ Cahill, T.M.; Charles, M.J.; Seaman, V.Y. (2010). 
Development and application of a sensitive method to determine 
concentrations of acrolein and other carbonyls in ambient air. 
Health Effects Institute Research Report 149. Available at https://www.healtheffects.org/system/files/Cahill149.pdf.
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    In the past 30 years, many studies have been published with results 
reporting that populations who live, work, or go to school near high-
traffic roadways experience higher rates of numerous adverse health 
effects, compared to populations far away from major roads.\143\ In 
addition, numerous studies have found adverse health effects associated 
with spending time in traffic, such as commuting or walking along high-
traffic roadways, including studies among 
children.144 145 146 147 The health outcomes with the 
strongest evidence linking them with traffic-associated air pollutants 
are respiratory effects, particularly in asthmatic children, and 
cardiovascular effects. Commenters on the NPRM stressed the importance 
of consideration of the impacts of traffic-related air pollution, 
especially NOX, on children's health.
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    \143\ In the widely-used PubMed database of health publications, 
between January 1, 1990 and December 31, 2021, 1,979 publications 
contained the keywords ``traffic, pollution, epidemiology,'' with 
approximately half the studies published after 2015.
    \144\ Laden, F.; Hart, J.E.; Smith, T.J.; Davis, M.E.; Garshick, 
E. (2007) Cause-specific mortality in the unionized U.S. trucking 
industry. Environmental Health Perspect 115:1192-1196.
    \145\ Peters, A.; von Klot, S.; Heier, M.; Trentinaglia, I.; 
H[ouml]rmann, A.; Wichmann, H.E.; L[ouml]wel, H. (2004) Exposure to 
traffic and the onset of myocardial infarction. New England J Med 
351: 1721-1730.
    \146\ Zanobetti, A.; Stone, P.H.; Spelzer, F.E.; Schwartz, J.D.; 
Coull, B.A.; Suh, H.H.; Nearling, B.D.; Mittleman, M.A.; Verrier, 
R.L.; Gold, D.R. (2009) T-wave alternans, air pollution and traffic 
in high-risk subjects. Am J Cardiol 104: 665-670.
    \147\ Adar, S.; Adamkiewicz, G.; Gold, D.R.; Schwartz, J.; 
Coull, B.A.; Suh, H. (2007) Ambient and microenvironmental particles 
and exhaled nitric oxide before and after a group bus trip. Environ 
Health Perspect 115: 507-512.
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    Numerous reviews of this body of health literature have been 
published. In a 2022 final report, an expert panel of the Health 
Effects Institute (HEI) employed a systematic review focusing on 
selected health endpoints related to exposure to traffic-related air 
pollution.\148\ The HEI panel concluded

[[Page 4323]]

that there was a high level of confidence in evidence between long-term 
exposure to traffic-related air pollution and health effects in adults, 
including all-cause, circulatory, and ischemic heart disease 
mortality.\149\ The panel also found that there is a moderate-to-high 
level of confidence in evidence of associations with asthma onset and 
acute respiratory infections in children and lung cancer and asthma 
onset in adults. This report follows on an earlier expert review 
published by HEI in 2010, where it found strongest evidence for asthma-
related traffic impacts. Other literature reviews have been published 
with conclusions generally similar to the HEI 
panels'.150 151 152 153 Additionally, in 2014, researchers 
from the U.S. Centers for Disease Control and Prevention (CDC) 
published a systematic review and meta-analysis of studies evaluating 
the risk of childhood leukemia associated with traffic exposure and 
reported positive associations between ``postnatal'' proximity to 
traffic and leukemia risks, but no such association for ``prenatal'' 
exposures.\154\ The U.S. Department of Health and Human Services' 
National Toxicology Program (NTP) published a monograph including a 
systematic review of traffic-related air pollution and its impacts on 
hypertensive disorders of pregnancy. The NTP concluded that exposure to 
traffic-related air pollution is ``presumed to be a hazard to pregnant 
women'' for developing hypertensive disorders of pregnancy.\155\
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    \148\ HEI Panel on the Health Effects of Long-Term Exposure to 
Traffic-Related Air Pollution (2022) Systematic review and meta-
analysis of selected health effects of long-term exposure to 
traffic-related air pollution. Health Effects Institute Special 
Report 23. [Online at https://www.healtheffects.org/system/files/hei-special-report-23_1.pdf.] This more recent review focused on 
health outcomes related to birth effects, respiratory effects, 
cardiometabolic effects, and mortality.
    \149\ Boogaard, H.; Patton. A.P.; Atkinson, R.W.; Brook, J.R.; 
Chang, H.H.; Crouse, D.L.; Fussell, J.C.; Hoek, G.; Hoffman, B.; 
Kappeler, R.; Kutlar Joss, M.; Ondras, M.; Sagiv, S.K.; Somoli, E.; 
Shaikh, R.; Szpiro, A.A.; Van Vliet E.D.S.; Vinneau, D.; Weuve, J.; 
Lurmann, F.W.; Forastiere, F. (2022) Long-term exposure to traffic-
related air pollution and selected health outcomes: a systematic 
review and meta-analysis. Environ Intl 164: 107262. [Online at 
https://doi.org/10.1016/j.envint.2022.107262].
    \150\ Boothe, V.L.; Shendell, D.G. (2008). Potential health 
effects associated with residential proximity to freeways and 
primary roads: review of scientific literature, 1999-2006. J Environ 
Health 70: 33-41.
    \151\ Salam, M.T.; Islam, T.; Gilliland, F.D. (2008). Recent 
evidence for adverse effects of residential proximity to traffic 
sources on asthma. Curr Opin Pulm Med 14: 3-8.
    \152\ Sun, X.; Zhang, S.; Ma, X. (2014) No association between 
traffic density and risk of childhood leukemia: a meta-analysis. 
Asia Pac J Cancer Prev 15: 5229-5232.
    \153\ Raaschou-Nielsen, O.; Reynolds, P. (2006). Air pollution 
and childhood cancer: a review of the epidemiological literature. 
Int J Cancer 118: 2920-9.
    \154\ Boothe, V.L.; Boehmer, T.K.; Wendel, A.M.; Yip, F.Y. 
(2014) Residential traffic exposure and childhood leukemia: a 
systematic review and meta-analysis. Am J Prev Med 46: 413-422.
    \155\ National Toxicology Program (2019) NTP Monograph on the 
Systematic Review of Traffic-related Air Pollution and Hypertensive 
Disorders of Pregnancy. NTP Monograph 7. https://ntp.niehs.nih.gov/ntp/ohat/trap/mgraph/trap_final_508.pdf.
---------------------------------------------------------------------------

    Health outcomes with few publications suggest the possibility of 
other effects still lacking sufficient evidence to draw definitive 
conclusions. Among these outcomes with a small number of positive 
studies are neurological impacts (e.g., autism and reduced cognitive 
function) and reproductive outcomes (e.g., preterm birth, low birth 
weight).156 157 158 159 160
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    \156\ Volk, H.E.; Hertz-Picciotto, I.; Delwiche, L.; et al. 
(2011). Residential proximity to freeways and autism in the CHARGE 
study. Environ Health Perspect 119: 873-877.
    \157\ Franco-Suglia, S.; Gryparis, A.; Wright, R.O.; et al. 
(2007). Association of black carbon with cognition among children in 
a prospective birth cohort study. Am J Epidemiol. doi: 10.1093/aje/
kwm308. [Online at http://dx.doi.org].
    \158\ Power, M.C.; Weisskopf, M.G.; Alexeef, S.E.; et al. 
(2011). Traffic-related air pollution and cognitive function in a 
cohort of older men. Environ Health Perspect 2011: 682-687.
    \159\ Wu, J.; Wilhelm, M.; Chung, J.; et al. (2011). Comparing 
exposure assessment methods for traffic-related air pollution in and 
adverse pregnancy outcome study. Environ Res 111: 685-6692.
    \160\ Stenson, C.; Wheeler, A.J.; Carver, A.; et al. (2021) The 
impact of traffic-related air pollution on child and adolescent 
academic performance: a systematic review. Environ Intl 155: 106696 
[Online at https://doi.org/10.1016/j.envint.2021.106696].
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    In addition to health outcomes, particularly cardiopulmonary 
effects, conclusions of numerous studies suggest mechanisms by which 
traffic-related air pollution affects health. For example, numerous 
studies indicate that near-roadway exposures may increase systemic 
inflammation, affecting organ systems, including blood vessels and 
lungs.161 162 163 164 Additionally, long-term exposures in 
near-road environments have been associated with inflammation-
associated conditions, such as atherosclerosis and 
asthma.165 166 167
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    \161\ Riediker, M. (2007). Cardiovascular effects of fine 
particulate matter components in highway patrol officers. Inhal 
Toxicol 19: 99-105. doi: 10.1080/08958370701495238.
    \162\ Alexeef, S.E.; Coull, B.A.; Gryparis, A.; et al. (2011). 
Medium-term exposure to traffic-related air pollution and markers of 
inflammation and endothelial function. Environ Health Perspect 119: 
481-486. doi:10.1289/ehp.1002560.
    \163\ Eckel. S.P.; Berhane, K.; Salam, M.T.; et al. (2011). 
Residential Traffic-related pollution exposure and exhaled nitric 
oxide in the Children's Health Study. Environ Health Perspect. 
doi:10.1289/ehp.1103516.
    \164\ Zhang, J.; McCreanor, J.E.; Cullinan, P.; et al. (2009). 
Health effects of real-world exposure diesel exhaust in persons with 
asthma. Res Rep Health Effects Inst 138. [Online at http://www.healtheffects.org].
    \165\ Adar, S.D.; Klein, R.; Klein, E.K.; et al. (2010). Air 
pollution and the microvasculature: a cross-sectional assessment of 
in vivo retinal images in the population-based Multi-Ethnic Study of 
Atherosclerosis. PLoS Med 7(11): E1000372. doi:10.1371/
journal.pmed.1000372. Available at http://dx.doi.org.
    \166\ Kan, H.; Heiss, G.; Rose, K.M.; et al. (2008). Prospective 
analysis of traffic exposure as a risk factor for incident coronary 
heart disease: The Atherosclerosis Risk in Communities (ARIC) study. 
Environ Health Perspect 116: 1463-1468. doi:10.1289/ehp.11290. 
Available at http://dx.doi.org.
    \167\ McConnell, R.; Islam, T.; Shankardass, K.; et al. (2010). 
Childhood incident asthma and traffic-related air pollution at home 
and school. Environ Health Perspect 1021-1026.
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    Several studies suggest that some factors may increase 
susceptibility to the effects of traffic-associated air pollution. 
Several studies have found stronger adverse health associations in 
children experiencing chronic social stress, such as in violent 
neighborhoods or in homes with low incomes or high family 
stress.168 169 170 171
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    \168\ Islam, T.; Urban, R.; Gauderman, W.J.; et al. (2011). 
Parental stress increases the detrimental effect of traffic exposure 
on children's lung function. Am J Respir Crit Care Med.
    \169\ Clougherty, J.E.; Levy, J.I.; Kubzansky, L.D.; et al. 
(2007). Synergistic effects of traffic-related air pollution and 
exposure to violence on urban asthma etiology. Environ Health 
Perspect 115: 1140-1146.
    \170\ Chen, E.; Schrier, H.M.; Strunk, R.C.; et al. (2008). 
Chronic traffic-related air pollution and stress interact to predict 
biologic and clinical outcomes in asthma. Environ Health Perspect 
116: 970-5.
    \171\ Long, D.; Lewis, D.; Langpap, C. (2021) Negative traffic 
externalities and infant health: the role of income heterogeneity 
and residential sorting. Environ and Resource Econ 80: 637-674. 
[Online at https://doi.org/10.1007/s10640-021-00601-w].
---------------------------------------------------------------------------

    The risks associated with residence, workplace, or schools near 
major roads are of potentially high public health significance due to 
the large population in such locations. The 2013 U.S. Census Bureau's 
American Housing Survey (AHS) was the last AHS that included whether 
housing units were within 300 feet of an ``airport, railroad, or 
highway with four or more lanes.'' \172\ The 2013 survey reports that 
17.3 million housing units, or 13 percent of all housing units in the 
United States, were in such areas. Assuming that populations and 
housing units are in the same locations, this corresponds to a 
population of more than 41 million U.S. residents in close proximity to 
high-traffic roadways or other transportation sources. According to the 
Central Intelligence Agency's World Factbook, based on data collected 
between 2012-2014, the United States had 6,586,610 km of roadways, 
293,564 km of railways, and 13,513 airports. As such, highways 
represent the overwhelming majority of transportation facilities 
described by this factor in the AHS.
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    \172\ The variable was known as ``ETRANS'' in the questions 
about the neighborhood.

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[[Page 4324]]

    EPA also conducted a study to estimate the number of people living 
near truck freight routes in the United States.\173\ Based on a 
population analysis using the U.S. Department of Transportation's 
(USDOT) Freight Analysis Framework 4 (FAF4) and population data from 
the 2010 decennial census, an estimated 72 million people live within 
200 meters of these freight routes.174 175 In addition, 
relative to the rest of the population, people of color and those with 
lower incomes are more likely to live near FAF4 truck routes. They are 
also more likely to live in metropolitan areas. The EPA's Exposure 
Factor Handbook also indicates that, on average, Americans spend more 
than an hour traveling each day, bringing nearly all residents into a 
high-exposure microenvironment for part of the day.\176\
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    \173\ U.S. EPA (2021). Estimation of Population Size and 
Demographic Characteristics among People Living Near Truck Routes in 
the Conterminous United States. Memorandum to the Docket.
    \174\ FAF4 is a model from the USDOT's Bureau of Transportation 
Statistics (BTS) and Federal Highway Administration (FHWA), which 
provides data associated with freight movement in the U.S. It 
includes data from the 2012 Commodity Flow Survey (CFS), the Census 
Bureau on international trade, as well as data associated with 
construction, agriculture, utilities, warehouses, and other 
industries. FAF4 estimates the modal choices for moving goods by 
trucks, trains, boats, and other types of freight modes. It includes 
traffic assignments, including truck flows on a network of truck 
routes. https://ops.fhwa.dot.gov/freight/freight_analysis/faf/.
    \175\ The same analysis estimated the population living within 
100 meters of a FAF4 truck route is 41 million.
    \176\ EPA. (2011) Exposure Factors Handbook: 2011 Edition. 
Chapter 16. Online at https://www.epa.gov/sites/production/files/2015-09/documents/efh-Chapter16.pdf.
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    As described in Section VII.H.1, we estimate that about 10 million 
students attend schools within 200 meters of major roads.\177\ Research 
into the impact of traffic-related air pollution on school performance 
is tentative. A review of this literature found some evidence that 
children exposed to higher levels of traffic-related air pollution show 
poorer academic performance than those exposed to lower levels of 
traffic-related air pollution.\178\ However, this evidence was judged 
to be weak due to limitations in the assessment methods.
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    \177\ Pedde, M.; Bailey, C. (2011) Identification of Schools 
within 200 Meters of U.S. Primary and Secondary Roads. Memorandum to 
the docket.
    \178\ Stenson, C.; Wheeler, A.J.; Carver, A.; et al. (2021) The 
impact of traffic-related air pollution on child and adolescent 
academic performance: a systematic review. Environ Intl 155: 106696. 
[Online at https://doi.org/10.1016/j.envint.2021.106696].
---------------------------------------------------------------------------

    While near-roadway studies focus on residents near roads or others 
spending considerable time near major roads, the duration of commuting 
results in another important contributor to overall exposure to 
traffic-related air pollution. Studies of health that address time 
spent in transit have found evidence of elevated risk of cardiac 
impacts.179 180 181 Studies have also found that school bus 
emissions can increase student exposures to diesel-related air 
pollutants, and that programs that reduce school bus emissions may 
improve health and reduce school absenteeism.182 183 184 185
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    \179\ Riediker, M.; Cascio, W.E.; Griggs, T.R.; et al. (2004) 
Particulate matter exposure in cars is associated with 
cardiovascular effects in healthy young men. Am J Respir Crit Care 
Med 169. [Online at https://doi.org/10.1164/rccm.200310-1463OC].
    \180\ Peters, A.; von Klot, S.; Heier, M.; et al. (2004) 
Exposure to traffic and the onset of myocardial infarction. New Engl 
J Med 1721-1730. [Online at https://doi.org/10.1056/NEJMoa040203].
    \181\ Adar, S.D.; Gold, D.R.; Coull, B.A.; (2007) Focused 
exposure to airborne traffic particles and heart rate variability in 
the elderly. Epidemiology 18: 95-103 [Online at: https://doi.org/10.1097/01.ede.0000249409.81050.46].
    \182\ Sabin, L.; Behrentz, E.; Winer, A.M.; et al. 
Characterizing the range of children's air pollutant exposure during 
school bus commutes. J Expo Anal Environ Epidemiol 15: 377-387. 
[Online at https://doi.org/10.1038/sj.jea.7500414].
    \183\ Li, C.; N, Q.; Ryan, P.H.; School bus pollution and 
changes in the air quality at schools: a case study. J Environ Monit 
11: 1037-1042. [https://doi.org/10.1039/b819458k].
    \184\ Austin, W.; Heutel, G.; Kreisman, D. (2019) School bus 
emissions, student health and academic performance. Econ Edu Rev 70: 
108-12.
    \185\ Adar, S.D.; D. Souza, J.; Sheppard, L.; Adopting clean 
fuels and technologies on school buses. Pollution and health impacts 
in children. Am J Respir Crit Care Med 191. [Online at http://doi.org/10.1164/rccm.201410-1924OC].
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C. Environmental Effects Associated With Exposure to Pollutants 
Impacted by This Rule

    This section discusses the environmental effects associated with 
pollutants affected by this rule, specifically PM, ozone, 
NOX and air toxics.
1. Visibility
    Visibility can be defined as the degree to which the atmosphere is 
transparent to visible light.\186\ Visibility impairment is caused by 
light scattering and absorption by suspended particles and gases. It is 
dominated by contributions from suspended particles except under 
pristine conditions. Visibility is important because it has direct 
significance to people's enjoyment of daily activities in all parts of 
the country. Individuals value good visibility for the well-being it 
provides them directly, where they live and work, and in places where 
they enjoy recreational opportunities. Visibility is also highly valued 
in significant natural areas, such as national parks and wilderness 
areas, and special emphasis is given to protecting visibility in these 
areas. For more information on visibility see the final 2019 p.m. 
ISA.\187\
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    \186\ National Research Council, (1993). Protecting Visibility 
in National Parks and Wilderness Areas. National Academy of Sciences 
Committee on Haze in National Parks and Wilderness Areas. National 
Academy Press, Washington, DC. This book can be viewed on the 
National Academy Press website at https://www.nap.edu/catalog/2097/protecting-visibility-in-national-parks-and-wilderness-areas.
    \187\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
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    EPA is working to address visibility impairment. Reductions in air 
pollution from implementation of various programs associated with the 
Clean Air Act Amendments of 1990 provisions have resulted in 
substantial improvements in visibility and will continue to do so in 
the future. Nationally, because trends in haze are closely associated 
with trends in particulate sulfate and nitrate due to the relationship 
between their concentration and light extinction, visibility trends 
have improved as emissions of SO2 and NOX have 
decreased over time due to air pollution regulations such as the Acid 
Rain Program.\188\ However between 1990 and 2018, in the western part 
of the country, changes in total light extinction were smaller, and the 
contribution of particulate organic matter to atmospheric light 
extinction was increasing due to increasing wildfire emissions.\189\
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    \188\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \189\ Hand, J.L.; Prenni, A.J.; Copeland, S.; Schichtel, B.A.; 
Malm, W.C. (2020). Thirty years of the Clean Air Act Amendments: 
Impacts on haze in remote regions of the United States (1990-2018). 
Atmos Environ 243: 117865.
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    In the Clean Air Act Amendments of 1977, Congress recognized 
visibility's value to society by establishing a national goal to 
protect national parks and wilderness areas from visibility impairment 
caused by manmade pollution.\190\ In 1999, EPA finalized the regional 
haze program to protect the visibility in Mandatory Class I Federal 
areas.\191\ There are 156 national parks, forests and wilderness areas 
categorized as Mandatory Class I Federal areas.\192\ These areas are 
defined in CAA section 162 as those national parks exceeding 6,000 
acres, wilderness areas, and memorial parks exceeding 5,000 acres, and 
all international parks which were in existence on August 7, 1977.
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    \190\ See CAA section 169(a).
    \191\ 64 FR 35714, July 1, 1999.
    \192\ 62 FR 38680-38681, July 18, 1997.

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[[Page 4325]]

    EPA has also concluded that PM2.5 causes adverse effects 
on visibility in other areas that are not targeted by the Regional Haze 
Rule, such as urban areas, depending on PM2.5 concentrations 
and other factors such as dry chemical composition and relative 
humidity (i.e., an indicator of the water composition of the 
particles). The secondary (welfare-based) PM NAAQS provide protection 
against visibility effects. In recent PM NAAQS reviews, EPA evaluated a 
target level of protection for visibility impairment that is expected 
to be met through attainment of the existing secondary PM standards.
2. Plant and Ecosystem Effects of Ozone
    The welfare effects of ozone include effects on ecosystems, which 
can be observed across a variety of scales, i.e., subcellular, 
cellular, leaf, whole plant, population and ecosystem. When ozone 
effects that begin at small spatial scales, such as the leaf of an 
individual plant, occur at sufficient magnitudes (or to a sufficient 
degree), they can result in effects being propagated along a continuum 
to higher and higher levels of biological organization. For example, 
effects at the individual plant level, such as altered rates of leaf 
gas exchange, growth and reproduction, can, when widespread, result in 
broad changes in ecosystems, such as productivity, carbon storage, 
water cycling, nutrient cycling, and community composition.
    Ozone can produce both acute and chronic injury in sensitive plant 
species depending on the concentration level and the duration of the 
exposure.\193\ In those sensitive species,\194\ effects from repeated 
exposure to ozone throughout the growing season of the plant can tend 
to accumulate, so even relatively low concentrations experienced for a 
longer duration have the potential to create chronic stress on 
vegetation.195 196 Ozone damage to sensitive plant species 
includes impaired photosynthesis and visible injury to leaves. The 
impairment of photosynthesis, the process by which the plant makes 
carbohydrates (its source of energy and food), can lead to reduced crop 
yields, timber production, and plant productivity and growth. Impaired 
photosynthesis can also lead to a reduction in root growth and 
carbohydrate storage below ground, resulting in other, more subtle 
plant and ecosystems impacts.\197\ These latter impacts include 
increased susceptibility of plants to insect attack, disease, harsh 
weather, interspecies competition, and overall decreased plant vigor. 
The adverse effects of ozone on areas with sensitive species could 
potentially lead to species shifts and loss from the affected 
ecosystems,\198\ resulting in a loss or reduction in associated 
ecosystem goods and services. Additionally, visible ozone injury to 
leaves can result in a loss of aesthetic value in areas of special 
scenic significance like national parks and wilderness areas and 
reduced use of sensitive ornamentals in landscaping.\199\ In addition 
to ozone effects on vegetation, newer evidence suggests that ozone 
affects interactions between plants and insects by altering chemical 
signals (e.g., floral scents) that plants use to communicate to other 
community members, such as attraction of pollinators.
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    \193\ 73 FR 16486, March 27, 2008.
    \194\ 73 FR 16491, March 27, 2008. Only a small percentage of 
all the plant species growing within the U.S. (over 43,000 species 
have been catalogued in the USDA PLANTS database) have been studied 
with respect to ozone sensitivity.
    \195\ U.S. EPA. Integrated Science Assessment (ISA) for Ozone 
and Related Photochemical Oxidants (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-20/012, 
2020.
    \196\ The concentration at which ozone levels overwhelm a 
plant's ability to detoxify or compensate for oxidant exposure 
varies. Thus, whether a plant is classified as sensitive or tolerant 
depends in part on the exposure levels being considered.
    \197\ 73 FR 16492, March 27, 2008.
    \198\ 73 FR 16493-16494, March 27, 2008. Ozone impacts could be 
occurring in areas where plant species sensitive to ozone have not 
yet been studied or identified.
    \199\ 73 FR 16490-16497, March 27, 2008.
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    The Ozone ISA presents more detailed information on how ozone 
affects vegetation and ecosystems.200 201 The Ozone ISA 
reports causal and likely causal relationships between ozone exposure 
and a number of welfare effects and characterizes the weight of 
evidence for different effects associated with ozone.\202\ The Ozone 
ISA concludes that visible foliar injury effects on vegetation, reduced 
vegetation growth, reduced plant reproduction, reduced productivity in 
terrestrial ecosystems, reduced yield and quality of agricultural 
crops, alteration of below-ground biogeochemical cycles, and altered 
terrestrial community composition are causally associated with exposure 
to ozone. It also concludes that increased tree mortality, altered 
herbivore growth and reproduction, altered plant-insect signaling, 
reduced carbon sequestration in terrestrial ecosystems, and alteration 
of terrestrial ecosystem water cycling are likely to be causally 
associated with exposure to ozone.
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    \200\ U.S. EPA. Integrated Science Assessment (ISA) for Ozone 
and Related Photochemical Oxidants (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-20/012, 
2020.
    \201\ U.S. EPA. Integrated Science Assessment (ISA) for Ozone 
and Related Photochemical Oxidants (Final Report). U.S. 
Environmental Protection Agency, Washington, DC, EPA/600/R-20/012, 
2020.
    \202\ The Ozone ISA evaluates the evidence associated with 
different ozone related health and welfare effects, assigning one of 
five ``weight of evidence'' determinations: causal relationship, 
likely to be a causal relationship, suggestive of a causal 
relationship, inadequate to infer a causal relationship, and not 
likely to be a causal relationship. For more information on these 
levels of evidence, please refer to Table II of the ISA.
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3. Atmospheric Deposition
    The Integrated Science Assessment for Oxides of Nitrogen, Oxides of 
Sulfur, and Particulate Matter--Ecological Criteria documents the 
ecological effects of the deposition of these criteria air 
pollutants.\203\ It is clear from the body of evidence that 
NOX, oxides of sulfur (SOX), and PM contribute to 
total nitrogen (N) and sulfur (S) deposition. In turn, N and S 
deposition cause either nutrient enrichment or acidification depending 
on the sensitivity of the landscape or the species in question. Both 
enrichment and acidification are characterized by an alteration of the 
biogeochemistry and the physiology of organisms, resulting in harmful 
declines in biodiversity in terrestrial, freshwater, wetland, and 
estuarine ecosystems in the United States. Decreases in biodiversity 
mean that some species become relatively less abundant and may be 
locally extirpated. In addition to the loss of unique living species, 
the decline in total biodiversity can be harmful because biodiversity 
is an important determinant of the stability of ecosystems and their 
ability to provide socially valuable ecosystem services.
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    \203\ U.S. EPA. Integrated Science Assessment (ISA) for Oxides 
of Nitrogen, Oxides of Sulfur and Particulate Matter Ecological 
Criteria (Final Report). U.S. Environmental Protection Agency, 
Washington, DC, EPA/600/R-20/278, 2020.
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    Terrestrial, wetland, freshwater, and estuarine ecosystems in the 
United States are affected by N enrichment/eutrophication caused by N 
deposition. These effects have been consistently documented across the 
United States for hundreds of species. In aquatic systems increased N 
can alter species assemblages and cause eutrophication. In terrestrial 
systems N loading can lead to loss of nitrogen-sensitive lichen 
species, decreased biodiversity of grasslands, meadows and other 
sensitive habitats, and increased potential for invasive species. For a 
broader explanation of the topics treated here, refer to the 
description in Chapter 4 of the RIA.
    The sensitivity of terrestrial and aquatic ecosystems to 
acidification from N and S deposition is predominantly governed by 
geology. Prolonged exposure to excess nitrogen and sulfur

[[Page 4326]]

deposition in sensitive areas acidifies lakes, rivers, and soils. 
Increased acidity in surface waters creates inhospitable conditions for 
biota and affects the abundance and biodiversity of fishes, 
zooplankton, and macroinvertebrates and ecosystem function. Over time, 
acidifying deposition also removes essential nutrients from forest 
soils, depleting the capacity of soils to neutralize future acid 
loadings and negatively affecting forest sustainability. Major effects 
in forests include a decline in sensitive tree species, such as red 
spruce (Picea rubens) and sugar maple (Acer saccharum).
    Building materials including metals, stones, cements, and paints 
undergo natural weathering processes from exposure to environmental 
elements (e.g., wind, moisture, temperature fluctuations, sunlight, 
etc.). Pollution can worsen and accelerate these effects. Deposition of 
PM is associated with both physical damage (materials damage effects) 
and impaired aesthetic qualities (soiling effects). Wet and dry 
deposition of PM can physically affect materials, adding to the effects 
of natural weathering processes, by potentially promoting or 
accelerating the corrosion of metals, by degrading paints, and by 
deteriorating building materials such as stone, concrete, and 
marble.\204\ The effects of PM are exacerbated by the presence of 
acidic gases and can be additive or synergistic due to the complex 
mixture of pollutants in the air and surface characteristics of the 
material. Acidic deposition has been shown to have an effect on 
materials including zinc/galvanized steel and other metal, carbonate 
stone (such as monuments and building facings), and surface coatings 
(paints).\205\ The effects on historic buildings and outdoor works of 
art are of particular concern because of the uniqueness and 
irreplaceability of many of these objects. In addition to aesthetic and 
functional effects on metals, stone, and glass, altered energy 
efficiency of photovoltaic panels by PM deposition is also becoming an 
important consideration for impacts of air pollutants on materials.
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    \204\ U.S. EPA. Integrated Science Assessment (ISA) for 
Particulate Matter (Final Report, 2019). U.S. Environmental 
Protection Agency, Washington, DC, EPA/600/R-19/188, 2019.
    \205\ Irving, P.M., e.d. 1991. Acid Deposition: State of Science 
and Technology, Volume III, Terrestrial, Materials, Health, and 
Visibility Effects, The U.S. National Acid Precipitation Assessment 
Program, Chapter 24, page 24-76.
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4. Environmental Effects of Air Toxics
    Emissions from producing, transporting, and combusting fuel 
contribute to ambient levels of pollutants that contribute to adverse 
effects on vegetation. VOCs, some of which are considered air toxics, 
have long been suspected to play a role in vegetation damage.\206\ In 
laboratory experiments, a wide range of tolerance to VOCs has been 
observed.\207\ Decreases in harvested seed pod weight have been 
reported for the more sensitive plants, and some studies have reported 
effects on seed germination, flowering, and fruit ripening. Effects of 
individual VOCs or their role in conjunction with other stressors 
(e.g., acidification, drought, temperature extremes) have not been well 
studied. In a recent study of a mixture of VOCs including ethanol and 
toluene on herbaceous plants, significant effects on seed production, 
leaf water content, and photosynthetic efficiency were reported for 
some plant species.\208\
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    \206\ U.S. EPA. (1991). Effects of organic chemicals in the 
atmosphere on terrestrial plants. EPA/600/3-91/001.
    \207\ Cape J.N., I.D. Leith, J. Binnie, J. Content, M. Donkin, 
M. Skewes, D.N. Price, A.R. Brown, A.D. Sharpe. (2003). Effects of 
VOCs on herbaceous plants in an open-top chamber experiment. 
Environ. Pollut. 124:341-343.
    \208\ Cape J.N., I.D. Leith, J. Binnie, J. Content, M. Donkin, 
M. Skewes, D.N. Price, A.R. Brown, A.D. Sharpe. (2003). Effects of 
VOCs on herbaceous plants in an open-top chamber experiment. 
Environ. Pollut. 124:341-343.
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    Research suggests an adverse impact of vehicle exhaust on plants, 
which has in some cases been attributed to aromatic compounds and in 
other cases to NOX.209 210 211 The impacts of 
VOCs on plant reproduction may have long-term implications for 
biodiversity and survival of native species near major roadways. Most 
of the studies of the impacts of VOCs on vegetation have focused on 
short-term exposure and few studies have focused on long-term effects 
of VOCs on vegetation and the potential for metabolites of these 
compounds to affect herbivores or insects.
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    \209\ Viskari E-L. (2000). Epicuticular wax of Norway spruce 
needles as indicator of traffic pollutant deposition. Water, Air, 
and Soil Pollut. 121:327-337.
    \210\ Ugrekhelidze D., F. Korte, G. Kvesitadze. (1997). Uptake 
and transformation of benzene and toluene by plant leaves. Ecotox. 
Environ. Safety 37:24-29.
    \211\ Kammerbauer H., H. Selinger, R. Rommelt, A. Ziegler-Jons, 
D. Knoppik, B. Hock. (1987). Toxic components of motor vehicle 
emissions for the spruce Picea abies. Environ. Pollut. 48:235-243.
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III. Test Procedures and Standards

    In applying heavy-duty criteria pollutant emission standards, EPA 
divides engines primarily into two types: Compression ignition (CI) 
(primarily diesel-fueled engines) and spark-ignition (SI) (primarily 
gasoline-fueled engines). The CI standards and requirements also apply 
to the largest natural gas engines. Battery-electric and fuel-cell 
vehicles are also subject to criteria pollutant standards and 
requirements. Criteria pollutant exhaust emission standards apply for 
four criteria pollutants: Oxides of nitrogen (NOX), 
particulate matter (PM), hydrocarbons (HC), and carbon monoxide 
(CO).\212\ In this Section III we describe new emission standards that 
will apply for these pollutants starting in MY 2027. We also describe 
new and updated test procedures we are finalizing in this rule.
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    \212\ Reference to hydrocarbon (HC) standards includes 
nonmethane hydrocarbon (NMHC), nonmethane-nonethane hydrocarbon 
(NMNEHC) and nonmethane hydrocarbon equivalent (NMHCE). See 40 CFR 
86.007-11.
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    Section III.A provides an overview of provisions that broadly apply 
for this final rule. Section III.B and Section III.D include the new 
laboratory-based standards and final updates to test procedures for 
heavy-duty compression-ignition and spark-ignition engines, 
respectively. Section III.C introduces the final off-cycle standards 
and test procedures that apply for compression-ignition engines and 
extend beyond the laboratory to on-the-road, real-world conditions. 
Section III.E describes the new refueling standards we are finalizing 
for certain heavy-duty spark-ignition engines. Each of these sections 
describe the final new standards and their basis, as well as describe 
the new test procedures and any updates to current test procedures, and 
describe our rationale for the final program, including feasibility 
demonstrations, available data, and comments received.

A. Overview

1. Migration and Clarifications of Regulatory Text
    As noted in Section I of this preamble, we are migrating our 
criteria pollutant regulations for model year 2027 and later heavy-duty 
highway engines from their current location in 40 CFR Part 86, subpart 
A, to 40 CFR Part 1036.\213\ Consistent with this migration, the 
compliance provisions discussed in this preamble refer to the 
regulations in their new location in part 1036. In general, this 
migration is not intended to change the compliance program specified in 
part 86, except as specifically finalized in this rulemaking. EPA 
submitted a memorandum to the docket describing how we proposed to 
migrate

[[Page 4327]]

certification and compliance provisions into 40 CFR part 1036.\214\
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    \213\ As noted in the following sections, we are proposing some 
updates to 40 CFR parts 1037, 1065, and 1068 to apply to other 
sectors in addition to heavy-duty highway engines.
    \214\ Stout, Alan; Brakora, Jessica. Memorandum to docket EPA-
HQ-OAR-2019-0055. ``Technical Issues Related to Migrating Heavy-Duty 
Highway Engine Certification Requirements from 40 CFR part 86, 
subpart A, to 40 CFR part 1036''. March 2022.
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i. Compression- and Spark-Ignition Engines Regulatory Text
    For many years, the regulations of 40 CFR part 86 have referred to 
``diesel heavy-duty engines'' and ``Otto-cycle heavy-duty engines''; 
however, as we migrate the heavy-duty provisions of 40 CFR part 86, 
subpart A, to 40 CFR part 1036 in this rule, we proposed to refer to 
these engines as ``compression-ignition'' (CI) and ``spark-ignition'' 
(SI), respectively, which are more comprehensive terms and consistent 
with existing language in 40 CFR part 1037 for heavy-duty motor vehicle 
regulations. We also proposed to update the terminology for the primary 
intended service classes in 40 CFR 1036.140 to replace Heavy heavy-duty 
engine with Heavy HDE, Medium heavy-duty engine with Medium HDE, Light 
heavy-duty engine with Light HDE, and Spark-ignition heavy-duty engine 
with Spark-ignition HDE.\215\ We received no adverse comment and are 
finalizing these terminology changes, as proposed. This final rule 
revises 40 CFR parts 1036 and 1037 to reflect this updated terminology. 
Throughout this preamble, reference to diesel and Otto-cycle engines 
and the previous service class nomenclature is generally limited to 
discussions relating to current test procedures and specific 
terminology used in 40 CFR part 86. Heavy-duty engines not meeting the 
definition of compression-ignition or spark-ignition are deemed to be 
compression-ignition engines for purposes of part 1036, per 40 CFR 
1036.1(c) and are subject to standards in 40 CFR 1036.104.
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    \215\ This new terminology for engines is also consistent with 
the ``HDV'' terminology used for vehicle classifications in 40 CFR 
1037.140.
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ii. Heavy-Duty Hybrid Regulatory Text
    Similar to our updates to more comprehensive and consistent 
terminology for CI and SI engines, as part of this rule we are also 
finalizing three main updates and clarifications to regulatory language 
for hybrid engines and hybrid powertrains. First, as proposed, we are 
finalizing an updated definition of ``engine configuration'' in 40 CFR 
1036.801; the updated definition clarifies that an engine configuration 
includes hybrid components if it is certified as a hybrid engine or 
hybrid powertrain. Second, we are finalizing, as proposed, a 
clarification in 40 CFR 1036.101(b) that regulatory references in part 
1036 to engines generally apply to hybrid engines and hybrid 
powertrains. Third, we are finalizing as proposed that manufacturers 
may optionally test the hybrid engine and powertrain together, rather 
than testing the engine alone. The option to test hybrid engine and 
powertrain together allows manufacturers to demonstrate emission 
performance of the hybrid technology that are not apparent when testing 
the engine alone. If the emissions results of testing the hybrid engine 
and powertrain together show NOX emissions lower than the 
final standards, then EPA anticipates that manufacturers may choose to 
participate in the NOX ABT program in the final rule (see 
preamble Section IV.G for details on the final ABT program).
    We requested comment on our proposed clarification in 40 CFR 
1036.101(b) that manufacturers may optionally test the hybrid engine 
and powertrain together, rather than testing the engine alone, and 
specifically, whether EPA should require all hybrid engines and 
powertrains to be certified together, rather than making it optional. 
For additional details on our proposed updates and clarifications to 
regulatory language for hybrid engines and hybrid powertrains, as well 
as our specific requests for comment on these changes, see the proposed 
rule preamble (87 FR 17457, March 28, 2022).
    Several commenters support the proposal to allow manufacturers to 
certify hybrid powertrains with a powertrain test procedure, but urge 
EPA to continue to allow manufacturers to certify hybrid systems using 
engine dynamometer testing procedures. These commenters stated that the 
powertrain dynamometer test procedures produce emission results that 
are more representative of hybrid engine or powertrain on-road 
operation than engine-only testing, however, commenters also stated the 
proposed test cycles are not reflective of real-world applications 
where hybrid technology works well and urged EPA to finalize different 
duty-cycles. In contrast, one commenter pointed to data collected from 
light-duty hybrid electric vehicles in Europe that the commenter stated 
shows hybrid-electric vehicles (HEVs) emit at higher levels than 
demonstrated in current certification test procedures; based on those 
data the commenter stated that EPA should not allow HEVs to generate 
NOX emissions credits. Separately, some commenters also 
stated that requiring powertrain testing for hybrid engines or hybrid 
powertrains certification would add regulatory costs or other 
logistical challenges.
    After considering these comments, EPA has determined that 
powertrain testing for hybrid systems should remain an option in this 
final rule. This option allows manufacturers to demonstrate emission 
performance of the hybrid technology, without requiring added test 
burden or logistical constraints. We are therefore finalizing as 
proposed the allowance for manufacturers to test the hybrid engine and 
powertrain together. If testing the hybrid engine and hybrid powertrain 
together results in NOX emissions that are below the final 
standards, then manufacturers can choose to certify to a FEL below the 
standard, and then generate NOX emissions credits as 
provided under the final ABT program (see Section IV.G). We disagree 
with one commenter who asserted that manufacturers should not be 
allowed to generate NOX emissions credits from HEVs based on 
data showing higher emissions from HEVs operating in the real-world 
compared to certification test data in Europe. Rather, we expect the 
powertrain test procedures we are finalizing will accurately reflect 
NOX emissions from HEVs due to the specifications we are 
including in the final test procedures, which differ from the 
certification test procedures to which the commenter referred.\216\ See 
preamble Section III.B.2.v for more details on the powertrain test 
procedures that we are finalizing.
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    \216\ We note that the data provided by the commenter was 
specific to light-duty vehicles and evaluated CO2 
emissions, not criteria pollutant emissions. EPA proposed and is 
finalizing changes to the light-duty test procedures for HEVs; in 
this Section III we focus on heavy-duty test procedures. See 
preamble Section XI and RTC Section 32 for details on the light-duty 
test procedures for HEVs.
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    Similarly, we disagree with those commenters urging EPA to finalize 
different duty-cycle tests to reflect hybrid real-world operations. 
While the duty-cycles suggested by commenters would represent some 
hybrid operations, they would not represent the duty-cycles of other 
hybrid vehicle types. See Section 3 of the Response to Comments 
document for additional details on our responses to comments on 
different duty-cycles for hybrid vehicles, and responses to other 
comments on hybrid engines and hybrid powertrains.
    In addition to our three main proposed updates and clarifications 
to regulatory language for hybrid engines and hybrid powertrain, we 
also proposed that manufacturers would certify a hybrid engine or 
hybrid powertrain to criteria pollutant

[[Page 4328]]

standards by declaring a primary intended service class of the engine 
configuration using the proposed, updated 40 CFR 1036.140.\217\ Our 
proposal included certifying to the same useful life requirements of 
the primary intended service class, which would provide truck owners 
and operators with similar assurance of durability regardless of the 
powertrain configuration they choose. Finally, we proposed an update to 
40 CFR 1036.230(e) such that engine configurations certified as a 
hybrid engine or hybrid powertrain may not be included in an engine 
family with conventional engines, which is consistent with the current 
provisions. We received no adverse comment and are finalizing as 
proposed these updates to 40 CFR 1036.140 and 1036.230(e).
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    \217\ The current provisions of 40 CFR 1036.140 distinguish 
classes based on engine characteristics and characteristics of the 
vehicles for which manufacturers intend to design and market their 
engines.
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iii. Heavy-Duty Zero Emissions Vehicles Regulatory Text
    As part of this final rule we are also updating and consolidating 
regulatory language for battery-electric vehicles and fuel cell 
electric vehicles (BEVs and FCEVs), collectively referred to as zero 
emissions vehicles (ZEVs). For ZEVs, we are finalizing as proposed a 
consolidation and update to our regulations as part of a migration of 
heavy-duty vehicle regulations from 40 CFR part 86 to 40 CFR part 1037. 
In the HD GHG Phase 1 rulemaking, EPA revised the heavy-duty vehicle 
and engine regulations to make them consistent with our regulatory 
approach to electric vehicles (EVs) under the light-duty vehicle 
program. Specifically, we applied standards for all regulated criteria 
pollutants and GHGs to all heavy-duty vehicle types, including 
EVs.\218\ Starting in MY 2016, criteria pollutant standards and 
requirements applicable to heavy-duty vehicles at or below 14,000 
pounds gross vehicle weight rating (GVWR) in 40 CFR part 86, subpart S, 
applied to heavy-duty EVs above 14,000 pounds GVWR through the use of 
good engineering judgment (see current 40 CFR 86.016-1(d)(4)). Under 
the current 40 CFR 86.016-1(d)(4), heavy-duty vehicles powered solely 
by electricity are deemed to have zero emissions of regulated 
pollutants; this provision also provides that heavy-duty EVs may not 
generate NOX or PM emission credits.
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    \218\ 76 FR 57106, September 15, 2011.
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    As proposed, this final rule consolidates certification 
requirements for ZEVs over 14,000 pounds GVWR in 40 CFR part 1037 such 
that manufacturers of ZEVs over 14,000 pounds GVWR will certify to 
meeting the emission standards and requirements of 40 CFR part 1037. 
There are no criterial pollutant emission standards in 40 CFR part 
1037, so we state in a new 40 CFR 1037.102, with revisions from the 
proposed rule, that heavy-duty vehicles without propulsion engines are 
subject to the same criteria pollutant emission standards that apply 
for engines under 40 CFR part 86, subpart A, and 40 CFR part 1036. We 
further specify in the final 40 CFR 1037.102 that ZEVs are deemed to 
have zero tailpipe emissions of criteria pollutants. As discussed in 
Section IV.G, we are choosing not to finalize our proposal to allow 
manufacturers to generate NOX emission credits from ZEVs if 
the vehicle met certain proposed requirements. We are accordingly 
carrying forward in the final 40 CFR 1037.102 a provisions stating that 
manufacturers may not generate emission credits from ZEVs. We are 
choosing not to finalize the proposed durability requirements for ZEVs, 
but we may choose in a future action to reexamine this issue. We are 
finalizing as proposed to continue to not allow heavy-duty ZEVs to 
generate PM emission credits since we are finalizing as proposed not to 
allow any manufacturer to generate PM emission credits for use in MY 
2027 and later under the final ABT program presented in Section IV.G.
    The provisions in existing and final 40 CFR 1037.5 defer to 40 CFR 
86.1801-12 to clarify how certification requirements apply for heavy-
duty vehicles at or below 14,000 pounds GVWR. Emission standards and 
certification requirements in 40 CFR part 86, subpart S, generally 
apply for complete heavy-duty vehicles at or below 14,000 pounds GVWR. 
We proposed to also apply emission standards and certification 
requirements under 40 CFR part 86, subpart S, for all incomplete 
vehicles at or below 14,000 pounds GVWR. We decided not to adopt this 
requirement and are instead continuing to allow manufacturers to choose 
whether to certify incomplete vehicles at or below 14,000 pounds GVWR 
to the emission standards and certification requirements in either 40 
CFR part 86, subpart S, or 40 CFR part 1037.
2. Numeric Standards and Test Procedures for Compression-Ignition and 
Spark-Ignition Engines
    As summarized in preamble Section I.B and detailed in this preamble 
Section III, we are finalizing numeric NOX standards and 
useful life periods that are largely consistent with the most stringent 
proposed option for MY 2027. The specific standards are summarized in 
Section III.B, Section 0, Section III.D, and Section III.E. As required 
by CAA section 202(a)(3), EPA is finalizing new NOX, PM, HC, 
and CO emission standards for heavy-duty engines that reflect the 
greatest degree of emission reduction achievable through the 
application of technology that we have determined would be available 
for MY 2027, and in doing so have given appropriate consideration to 
additional factors, namely lead time, cost, energy, and safety. For all 
heavy-duty engine classes, the final numeric NOX standards 
for medium- and high-load engine operations match the most stringent 
standards proposed for MY 2027; for low-load operations we are 
finalizing the most stringent standard proposed for any model year (see 
III.B.2.iii for discussion).\219\ For smaller heavy-duty engine service 
classes (i.e., light and medium heavy-duty engines CI and SI heavy-duty 
engines), the numeric standards are combined with the longest useful 
life periods we proposed. For the largest heavy-duty engines (i.e., 
heavy heavy-duty engines), the final numeric standards are combined 
with the longest useful life mileage that we proposed for MY 2027. The 
final useful life periods for the largest heavy-duty engines are 50 
percent longer than today's useful life periods, which will play an 
important role in ensuring continued emissions control while the 
engines operate on the road. The final numeric emissions standards and 
useful life periods for all heavy-duty engines are based on further 
consideration of data included in the proposal from our engine 
demonstration programs that show the final emissions standards are 
feasible at the final useful life periods applicable to these each 
heavy-duty engine service class. Our assessment of the data available 
at the time of proposal is further supported by our evaluation of 
additional information and public comments stating that the proposed 
standards are feasible. Our technical assessments are primarily based 
on results from testing several diesel engine and aftertreatment 
systems at Southwest Research Institute and at EPA's National Vehicle 
and Fuel Emissions Laboratory (NVFEL), as well as heavy-duty gasoline 
engine testing conducted at NVFEL; we also

[[Page 4329]]

considered heavy-duty engine certification data submitted to EPA by 
manufacturers, ANPR and NPRM comments, and other data submitted by 
industry stakeholders or studies conducted by EPA, as more specifically 
identified in the sections that follow.
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    \219\ As proposed, we are finalizing a new test procedure for 
heavy-duty CI engines to demonstrate emission control when the 
engine is operating under low-load and idle conditions; this new 
test procedure does not apply to heavy-duty SI engines (see Section 
III.B.2.iii for additional discussion).
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    After further consideration of the data included in the proposal, 
as well as information submitted by commenters and additional data we 
collected since the time of proposal, we are finalizing two updates 
from our proposed testing requirements in order to ensure the greatest 
emissions reductions technically achievable are met throughout the 
final useful life periods; these updates are tailored to the larger 
engine classes (medium and heavy heavy-duty engines). First, we are 
finalizing a requirement for manufacturers to demonstrate before heavy 
heavy-duty engines are in-use that the emissions control technology is 
durable through a period of time longer than the final useful life 
mileage. For these largest engines with the longest useful life 
mileages, the extended laboratory durability demonstration will better 
ensure the final standards will be met throughout the regulatory useful 
life under real-world operations where conditions are more variable. 
Second, we are finalizing an interim in-use compliance allowance that 
applies when EPA evaluates whether heavy or medium heavy-duty engines 
are meeting the final standards after these engines are in use in the 
real-world. When combined with the final useful life values, we believe 
the interim in-use compliance allowance will address concerns raised in 
comments from manufacturers that the more stringent proposed MY 2027 
standards would not be feasible to meet over the very long useful life 
periods of heavy heavy-duty engines, or under the challenging duty-
cycles of medium heavy-duty engines. This interim, in-use compliance 
allowance is generally consistent with our past practice (for example, 
see 66 FR 5114, January 18, 2001); also consistent with past practice, 
the compliance allowance is included as an interim provision that we 
may reassess in the future through rulemaking based on the performance 
of emissions controls over the final useful life periods for medium and 
heavy heavy-duty engines.\220\ To set standards that result in the 
greatest emission reductions achievable for medium and heavy heavy-duty 
engines, we considered additional data that we and others collected 
since the time of the proposal; these data show the significant 
technical challenge of maintaining very low NOX emissions 
throughout very long useful life periods for heavy heavy-duty engines, 
and greater amounts of certain aging mechanisms over the long useful 
life periods of medium heavy-duty engines. In addition to these data, 
in setting the standards we gave appropriate consideration to costs 
associated with the application of technology to achieve the greatest 
emissions reductions in MY 2027 (i.e., cost of compliance for 
manufacturers associated with the standards \221\) and other statutory 
factors, including energy and safety. We determined that for heavy 
heavy-duty engines the combination of: (1) The most stringent MY 2027 
standards proposed, (2) longer useful life periods compared to today's 
useful life periods, (3) targeted, interim compliance allowance 
approach to in-use compliance testing, and (4) the extended durability 
demonstration for emissions control technologies is appropriate, 
feasible, and consistent with our authority under the CAA to set 
technology-forcing criteria pollutant standards for heavy-duty engines 
for their useful life.\222\ Similarly, for medium heavy-duty engines we 
determined that the combination of the first three elements (i.e., most 
stringent MY 2027 standards proposed, increase in useful life periods, 
and interim compliance allowance for in-use testing) is appropriate, 
feasible, and consistent with our CAA authority to set technology-
forcing criteria pollutant standards for heavy-duty engines for their 
useful life.
---------------------------------------------------------------------------

    \220\ We plan to closely monitor the in-use emissions 
performance of model year 2027 and later engines to determine the 
long-term need for the interim compliance allowance. For example, we 
intend to analyze the data from the manufacturer run in-use testing 
program to compare how engines age in the field compared to how they 
age in the laboratory.
    \221\ More specifically, for this rule in setting the final 
standards and consistent with CAA section 202(a)(3)(A), the cost of 
compliance for manufacturers associated with the standards that EPA 
gave appropriate consideration to includes the direct manufacturing 
costs and indirect costs incurred by manufacturers associated with 
meeting the final standards over the corresponding final useful life 
values, given that this rule sets new more stringent standards 
through both the numeric level of the standard and the length of the 
useful life period.
    \222\ CAA section 202(a)(3)(A) is a technology-forcing provision 
and reflects Congress' intent that standards be based on projections 
of future advances in pollution control capability, considering 
costs and other statutory factors. See National Petrochemical & 
Refiners Association v. EPA, 287 F.3d 1130, 1136 (D.C. Cir. 2002) 
(explaining that EPA is authorized to adopt ``technology-forcing'' 
regulations under CAA section 202(a)(3)); NRDC v. Thomas, 805 F.2d 
410, 428 n.30 (D.C. Cir. 1986) (explaining that such statutory 
language that ``seek[s] to promote technological advances while also 
accounting for cost does not detract from their categorization as 
technology-forcing standards''); see also Husqvarna AB v. EPA, 254 
F.3d 195 (D.C. Cir. 2001) (explaining that CAA sections 202 and 213 
have similar language and are technology-forcing standards). In this 
context, the term ``technology-forcing'' has a specific legal 
meaning and is used to distinguish standards that may require 
manufacturers to develop new technologies (or significantly improve 
existing technologies) from standards that can be met using existing 
off-the-shelf technology alone. Technology-forcing standards such as 
those in this final rule do not require manufacturers to use 
specific technologies.
---------------------------------------------------------------------------

    In addition to the final standards for the defined duty cycle and 
off-cycle test procedures, the final standards include several other 
provisions for controlling emissions from specific operations in CI or 
SI engines. First, we are finalizing, as proposed, to allow CI engine 
manufacturers to voluntarily certify to idle standards using a new idle 
test procedure that is based on an existing California Air Resources 
Board (CARB) procedure.\223\
---------------------------------------------------------------------------

    \223\ 13 CCR 1956.8 (a)(6)(C)--Optional NOX idling 
emission standard.
---------------------------------------------------------------------------

    We are also finalizing two options for manufacturers to control 
engine crankcase emissions. Specifically, manufacturers will be 
required to either: (1) As proposed, close the crankcase, or (2) 
measure and account for crankcase emissions using an updated version of 
the current requirements for an open crankcase. We believe that either 
will ensure that the total emissions are accounted for during 
certification testing and throughout the engine operation during useful 
life. See Section III.B for more discussion on both the final idle and 
crankcase provisions.
    For heavy-duty SI, we are finalizing as proposed a new refueling 
emission standard for incomplete vehicles above 14,000 lb GVWR starting 
in MY 2027.\224\ The final refueling standard is based on the current 
refueling standard that applies to complete heavy-duty gasoline-fueled 
vehicles. Consistent with the current evaporative emission standards 
that apply for these same vehicles, we are finalizing a requirement 
that manufacturers can use an engineering analysis to demonstrate that 
they meet our final refueling standard. We are also adopting an 
optional alternative phase-in compliance pathway that manufacturers can 
opt into in lieu of being subject to this implementation date for all 
incomplete heavy-duty vehicles above 14,000 pounds GVWR (see Section 
III.E for details).
---------------------------------------------------------------------------

    \224\ Some vehicle manufactures sell their engines or 
``incomplete vehicles'' (i.e., chassis that include their engines, 
the frame, and a transmission) to body builders who design and 
assemble the final vehicle.
---------------------------------------------------------------------------

    Consistent with our proposal, we are also finalizing several 
provisions to

[[Page 4330]]

reduce emissions from a broader range of engine operating conditions. 
First, we are finalizing new standards for our existing test procedures 
to reduce emissions under medium- and high-load operations (e.g., when 
trucks are traveling on the highway). Second, we are finalizing new 
standards and a corresponding new test procedure to measure emissions 
during low-load operations (i.e., the low-load cycle, LLC). Third, we 
are finalizing new standards and updates to an existing test procedure 
to measure emissions over the broader range of operations that occur 
when heavy-duty engines are operating on the road (i.e., off-
cycle).\225\
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    \225\ Duty-cycle test procedures measure emissions while the 
engine is operating over precisely defined duty cycles in an 
emissions testing laboratory and provide very repeatable emission 
measurements. ``Off-cycle'' test procedures measure emissions while 
the engine is not operating on a specified duty cycle; this testing 
can be conducted while the engine is being driven on the road (e.g., 
on a package delivery route), or in an emission testing laboratory. 
Both duty-cycle and off-cycle testing are conducted pre-production 
(e.g., for certification) or post-production to verify that the 
engine meets applicable duty-cycle or off-cycle emission standards 
throughout useful life (see Section III for more discussion).
---------------------------------------------------------------------------

    The new, more stringent numeric standards for the existing 
laboratory-based test procedures that measure emissions during medium- 
and high-load operations will ensure significant emissions reductions 
from heavy-duty engines. Without this final rule, these medium- and 
high-load operations are projected to contribute the most to heavy-duty 
NOX emissions in 2045.
    We are finalizing as proposed a new LLC test procedure, which will 
ensure demonstration of emission control under sustained low-load 
operations. After further consideration of data included in the 
proposal, as well as additional information from the comments 
summarized in this section, we are finalizing the most stringent 
numeric standard for the LLC that we proposed for any model year. As 
discussed in our proposal, data from our CI engine demonstration 
program showed that the lowest numeric NOX standard proposed 
would be feasible for the LLC throughout a useful life period similar 
to the useful life we are finalizing for the largest heavy-duty 
engines. After further consideration of this data, and additional 
support from data collected since the time of proposal, we are 
finalizing the most stringent standard proposed for any model year.
    We are finalizing new numeric standards and revisions to the 
proposed off-cycle test procedure. We proposed updates to the current 
off-cycle test procedure that included binning emissions measurements 
based on the type of operation the engine is performing when the 
measurement data is being collected. Specifically, we proposed that 
emissions data would be grouped into three bins, based on if the engine 
was operating in idle (Bin 1), low-load (Bin 2), or medium-to-high load 
(Bin 3) operation. Given the different operational profiles of each of 
the three bins, we proposed a separate standard for each bin. Based on 
further consideration of data included in the proposal, as well as 
additional support from our consideration of data provided by 
commenters, we are finalizing off-cycle standards for two bins, rather 
than three bins; correspondingly, we are finalizing a two-bin approach 
for grouping emissions data collected during off-cycle test procedures. 
Our evaluation of available information shows that two bins better 
represent the differences in engine operations that influence emissions 
(e.g., exhaust temperature, catalyst efficiency) and ensure sufficient 
data is collected in each bin to allow for an accurate analysis of the 
data to determine if emissions comply with the standard for each bin. 
Preamble Section III.C further discusses the final off-cycle standards.
3. Implementation of the Final Program
    As discussed in this section, we have evaluated the final standards 
in terms of technological feasibility, lead time, and stability, and 
given appropriate consideration to cost, energy, and safety, consistent 
with the requirements in CAA section 202(a)(3). The final standards are 
based on data from our CI and SI engine feasibility demonstration 
programs that was included in the proposal, and further supported by 
information submitted by commenters and additional data we collected 
since the time of proposal. Our evaluation of available data shows that 
the final standards and useful life periods are feasible and will 
result in the greatest emission reductions achievable for MY 2027, 
pursuant to CAA section 202(a)(3), giving appropriate consideration to 
cost, lead time, and other factors. We note that CAA section 202(a)(3) 
neither requires that EPA consider all the statutory factors equally 
nor mandates a specific method of cost analysis; rather EPA has 
discretion in determining the appropriate consideration to give such 
factors.\226\ As discussed in the Chapter 3 of the RIA, the final 
standards are achievable without increasing the overall fuel 
consumption and CO2 emissions of the engine (1) for each of 
the duty cycles (SET, FTP, and LLC), and (2) for the fuel mapping test 
procedures defined in 40 CFR 1036.535 and 1036.540.\227\ Finally, the 
final standards will have no negative impact on safety, based on the 
existing use of these technologies in light-duty and heavy-duty engines 
on the road today (see section 3 of the Response to Comments document 
for additional discussion on our assessment that the final standards 
will have no negative impact on safety). This includes the safety of 
closed crankcase systems, which we received comment on. As discussed in 
Section 3 of the RTC, one commenter stated that requiring closed 
crankcases could increase the chance of engine run away caused by 
combustion of engine oil that could enter the intake from the closed-
crankcase system. We disagree with the commenter since closed crankcase 
systems are used on engines today with no adverse effect on safety; 
however, we are providing flexibility for manufactures to meet the 
final standards regarding crankcase emissions (see preamble Section 
III.B.2.vi for details).
---------------------------------------------------------------------------

    \226\ See, e.g., Sierra Club v. EPA, 325 F.3d 374, 378 (D.C. 
Cir. 2003) (explaining that similar technology forcing language in 
CAA section 202(l)(2) ``does not resolve how the Administrator 
should weigh all [the statutory] factors in the process of finding 
the `greatest emission reduction achievable' ''); Husqvarna AB v. 
EPA, 254 F.3d 195, 200 (D.C. Cir. 2001) (explaining that under CAA 
section 213's similar technology-forcing authority that ``EPA did 
not deviate from its statutory mandate or frustrate congressional 
will by placing primary significance on the `greatest degree of 
emission reduction achievable' '' or by considering cost and other 
statutory factors as important but secondary).
    \227\ The final ORVR requirements discussed in Section III.E 
will reduce fuel consumed from gasoline fuel engines, but these fuel 
savings will not be measured on the duty cycles since the test 
procedures for these tests measure tailpipe emissions and do not 
measure emissions from refueling. We describe our estimate of the 
fuel savings in Chapter 7 of the RIA.
---------------------------------------------------------------------------

    While we have referenced a technology pathway for complying with 
our standards (Chapter 3 of the RIA) that is consistent with CAA 
section 202(a)(3), there are other technology pathways that 
manufacturers may choose in order to comply with the performance-based 
final standards. We did not rely on alternative technology pathways in 
our assessment of the feasibility of the final standards, however, 
manufacturers may choose from any number of technology pathways to 
comply with the final standards (e.g., alternative fuels, including 
biodiesel, renewable diesel, renewable natural gas, renewable propane, 
or hydrogen in combination with relevant emissions aftertreatment 
technologies, and electrification, including plug-in hybrid electric 
vehicles, battery-electric or fuel cell

[[Page 4331]]

electric vehicles). As noted in Section I, we are finalizing a program 
that will begin in MY 2027, which is the earliest year that standards 
can begin to apply under CAA section 202(a)(3)(C).\228\ The final 
NOX standards are a single-step program that reflect the 
greatest emission reductions achievable starting in MY 2027, giving 
appropriate consideration to costs and other factors. In this final 
rule, we are focused on achieving the greatest emission reductions 
achievable in the MY 2027 timeframe, and have applied our judgment in 
determining the appropriate standards for MY 2027 under this authority 
for a national program. As the heavy-duty industry continues to 
transition to zero-emission technologies, EPA could consider additional 
criteria pollutant standards for model years beyond 2027 in future 
rules.
---------------------------------------------------------------------------

    \228\ Section 202(a)(3)(C) requires that standards under 
202(a)(3)(A) apply no earlier than 4 years after promulgation, and 
apply for no less than 3 model years.
---------------------------------------------------------------------------

    In the event that manufacturers start production of some engine 
families sooner than four years from our final rule, we are finalizing 
a provision for manufacturers to split the 2027 model year, with an 
option for manufacturers to comply with the final MY 2027 standards for 
all engines produced for that engine family in MY 2027. Specifically, 
we are finalizing as proposed that a MY 2027 engine family that starts 
production within four years of the final rule could comply with the 
final MY 2027 standards for all engines produced for that engine family 
in MY2027, or could split the engine family by production date in MY 
2027 such that engines in the family produced prior to four years after 
the date that the final rule is promulgated would continue to be 
subject to the existing standards.229 230 The split model 
year provision for MY 2027 provides assurance that all manufacturers, 
regardless of when they start production of their engine families, will 
have four years of lead time to the MY 2027 standards under this final 
rule, while also maximizing emission reductions, which is consistent 
with our CAA authority. This final rule is promulgated upon the date of 
signature, upon which date EPA also provided this signed final rule to 
manufacturers and other stakeholders by email and posted it on EPA's 
public website.\231\
---------------------------------------------------------------------------

    \229\ See 40 CFR 86.007-11.
    \230\ 40 CFR 1036.150(t).
    \231\ This final rule will also be published in the Federal 
Register, and the effective date runs from the date of publication 
as specified in the DATES section. Note, non-substantive edits from 
the Office of the Federal Register may appear in the published 
version of the final rule.
---------------------------------------------------------------------------

4. Severability
    This final rule includes new and revised requirements for numerous 
provisions under various aspects of the highway heavy-duty emission 
control program, including numeric standards, test procedures, 
regulatory useful life, emission-related warranty, and other 
requirements. Further, as explained in Sections I and XI, it modernizes 
and amends numerous other CFR parts for other standard-setting parts 
for various specific reasons. Therefore, this final rule is a 
multifaceted rule that addresses many separate things for independent 
reasons, as detailed in each respective section of this preamble. We 
intended each portion of this rule to be severable from each other, 
though we took the approach of including all the parts in one 
rulemaking rather than promulgating multiple rules to modernize each 
part of the program.
    For example, the following portions of this rulemaking are mutually 
severable from each other, as numbered: (1) The emission standards in 
section III; (2) warranty in Section IV.B.1; (3) OBD requirements in 
Section IV.C; (4) inducements requirements in Section IV.D; (5) ABT 
program in Section IV.G; (6) the migration and clarification of 
regulatory text in Section III.A; and (7) other regulatory amendments 
discussed in Section XI. Each emission standard in Section III is also 
severable from each other emission standard, including for each duty-
cycle, off-cycle, and refueling standard; each pollutant; and each 
primary intended service class. For example, the NOX 
standard for the FTP duty-cycle for Heavy HDE is severable from all 
other emission standards. Each of the migration and clarification 
regulatory amendments in Section III.A is also severable from all the 
other regulatory amendments in that Section, and each of the regulatory 
amendments in Section XI is also severable from all the other 
regulatory amendments in that Section. If any of the above portions is 
set aside by a reviewing court, then we intend the remainder of this 
action to remain effective, and the remaining portions will be able to 
function absent any of the identified portions that have been set 
aside. Moreover, this list is not intended to be exhaustive, and should 
not be viewed as an intention by EPA to consider other parts of the 
rule not explicitly listed here as not severable from other parts of 
the rule.

B. Summary of Compression-Ignition Exhaust Emission Standards and Duty 
Cycle Test Procedures

    EPA is finalizing new NOX, PM, HC, and CO emission 
standards for heavy-duty compression-ignition engines that will be 
certified under 40 CFR part 1036.232 233 We are finalizing 
new emission standards for our existing laboratory test cycles (i.e., 
SET and FTP) and finalizing new NOX, PM, HC and CO emission 
standards based on a new LLC, as described in this section.\234\ The 
standards for NOX, PM, and HC are in units of milligrams/
horsepower-hour instead of the grams/horsepower-hour used for existing 
standards because using units of milligrams better reflects the 
precision of the new standards, rather than adding multiple zeros after 
the decimal place. Making this change will require updates to how 
manufacturers report data to the EPA in the certification application, 
but it does not require changes to the test procedures that define how 
to determine emission values.
---------------------------------------------------------------------------

    \232\ See 40 CFR 1036.104.
    \233\ See 40 CFR 1036.605 and Section XI.B of this preamble for 
a discussion of engines installed in specialty vehicles.
    \234\ See 40 CFR 1036.104.
---------------------------------------------------------------------------

    The final duty cycle emission standards in 40 CFR 1037.104 apply 
starting in model year 2027. This final rule includes new standards 
over the SET and FTP duty cycles currently used for certification, as 
well as new standards over a new LLC duty cycle to ensure manufacturers 
of compression-ignition engines are designing their engines to address 
emissions in during lower load operation that is not covered by the SET 
and FTP. The new standards are shown in Table III-1.

            Table III-1--Final Duty Cycle Emission Standards for Light HDE, Medium HDE, and Heavy HDE
----------------------------------------------------------------------------------------------------------------
                                                                     Model year 2027 and later
                                                 ---------------------------------------------------------------
                   Duty cycle                     NOX \a\ mg/hp-
                                                        hr          HC mg/hp-hr     PM mg/hp-hr     CO g/hp-hr
----------------------------------------------------------------------------------------------------------------
SET and FTP.....................................              35              60               5             6.0

[[Page 4332]]

 
LLC.............................................              50             140               5             6.0
----------------------------------------------------------------------------------------------------------------
\a\ An interim NOX compliance allowance of 15 mg/hp-hr applies for any in-use testing of Medium HDE and Heavy
  HDE. Manufacturers will add the compliance allowance to the NOX standard that applies for each duty cycle and
  for off-cycle Bin 2, for both in-use field testing and laboratory testing as described in 40 CFR part 1036,
  subpart E. Note, the NOX compliance allowance doesn't apply to confirmatory testing described in 40 CFR
  1036.235(c) or selective enforcement audits described in 40 CFR part 1068.

    This Section III.B describes the duty cycle emission standards and 
test procedures we are finalizing for compression-ignition engines. We 
describe compression-ignition engine technology packages that 
demonstrate the feasibility of achieving these standards in Section 
III.B.3.ii. The proposed rule provided an extensive discussion of the 
rationale and information supporting the proposed duty cycle standards 
(87 FR 17460, March 28, 2022). Chapters 1, 2, and 3 of the RIA include 
additional information related to the range of technologies to control 
criteria emissions, background on applicable test procedures, and the 
full feasibility analysis for compression-ignition engines. See also 
section 3 of the Response to Comments for a detailed discussion of the 
comments and how they have informed this final rule.
    As part of this rulemaking, we are finalizing an increase in the 
useful life for each engine class as described in Section IV.A. The 
emission standards outlined in this section will apply for the longer 
useful life periods and manufacturers will be responsible for 
demonstrating that their engines will meet these standards as part of 
the revisions to durability requirements described in Section IV.F. In 
Section IV.G, we discuss the updates to the ABT program, including 
updates to account for the three laboratory cycles (SET, FTP, and LLC) 
with unique standards.
1. Background on Existing Duty Cycle Test Procedures and Standards
    We begin by providing background information on the existing duty 
cycle test procedures and standards as relevant to this final rule, 
including the SET and FTP standards and test procedures, powertrain and 
hybrid powertrain test procedures, test procedure adjustments to 
account for production and measurement variability, and crankcase 
emissions. Current criteria pollutant standards must be met by 
compression-ignition engines over both the SET and FTP duty cycles. The 
FTP duty cycles, which date back to the 1970s, are composites of a 
cold-start and a hot-start transient duty cycle designed to represent 
urban driving. There are separate FTP duty cycles for both SI and CI 
engines. The cold-start emissions are weighted by one-seventh and the 
hot-start emissions are weighted by six-sevenths.\235\ The SET is a 
more recent duty cycle for diesel engines that is a continuous cycle 
with ramped transitions between the thirteen steady-state modes.\236\ 
The SET does not include engine starting and is intended to represent 
fully warmed-up operating modes not emphasized in the FTP, such as more 
sustained high speeds and loads.
---------------------------------------------------------------------------

    \235\ See 40 CFR 86.007-11 and 40 CFR 86.008-10.
    \236\ See 40 CFR 86.1362.
---------------------------------------------------------------------------

    Emission standards for criteria pollutants are currently set to the 
same numeric value for SET and FTP test cycles, as shown in Table III-
2. Manufacturers of compression-ignition engines have the option under 
the existing regulations to participate in our ABT program for 
NOX and PM, as discussed in the background of Section 
IV.G.\237\ These pollutants are subject to FEL caps under the existing 
regulations of 0.50 g/hp-hr for NOX and 0.02 g/hp-hr for 
PM.\238\
---------------------------------------------------------------------------

    \237\ See 40 CFR 86.007-15.
    \238\ See 40 CFR 86.007-11.

          Table III-2--Existing Part 86 Diesel-Cycle Engine Standards Over the SET and FTP Duty Cycles
----------------------------------------------------------------------------------------------------------------
                                                                   PM \b\ (g/hp-
                        NOX \a\ (g/hp-hr)                               hr)        HC (g/hp-hr)    CO (g/hp-hr)
----------------------------------------------------------------------------------------------------------------
0.20............................................................            0.01            0.14            15.5
----------------------------------------------------------------------------------------------------------------
\a\ Engine families participating in the existing ABT program are subject to a FEL cap of 0.50 g/hp-hr for NOX.
\b\ Engine families participating in the existing ABT program are subject to a FEL cap of 0.02 g/hp-hr for PM.

    EPA developed powertrain and hybrid powertrain test procedures for 
the HD GHG Phase 2 Heavy-Duty Greenhouse Gas rulemaking (81 FR 73478, 
October 25, 2016) with updates in the HD Technical Amendments final 
rule (86 FR 34321, June 29, 2021).\239\ The powertrain and hybrid 
powertrain tests allow manufacturers to directly measure the 
effectiveness of the engine, the transmission, the axle and the 
integration of these components as an input to the Greenhouse gas 
Emission Model (GEM) for compliance with the greenhouse gas standards. 
As part of the technical amendments, EPA updated the powertrain test 
procedure to allow use of test cycles beyond the current GEM vehicle 
drive cycles, to include the SET and FTP engine-based test cycles and 
to facilitate hybrid powertrain testing (40 CFR 1036.510, 1036.512, and 
1037.550).
---------------------------------------------------------------------------

    \239\ See 40 CFR 1037.550.
---------------------------------------------------------------------------

    These heavy-duty diesel-cycle engine standards are applicable for a 
useful life period based on the primary intended service class of the 
engine.\240\ For certification, manufacturers must demonstrate that 
their engines will meet these standards throughout the useful life by 
performing a durability test and applying a deterioration factor (DF) 
to their certification value.\241\ Additionally, manufacturers must 
adjust emission rates for engines with exhaust aftertreatment to 
account for infrequent

[[Page 4333]]

regeneration events accordingly.\242\ To account for variability in 
these measurements, as well as production variability, manufacturers 
typically add margin between the DF plus infrequent regeneration 
adjustment factor (IRAF) adjusted test result and the FEL. A summary of 
the margins manufacturers have added for MY 2019 and newer engines is 
summarized in Chapter 3.1.2 of the RIA.
---------------------------------------------------------------------------

    \240\ 40 CFR 86.004-2.
    \241\ See 40 CFR 86.004-26(c) and (d) and 86.004-28(c) and (d).
    \242\ See 40 CFR 1036.501(d).
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    Current regulations restrict the discharge of crankcase emissions 
directly into the ambient air. Blowby gases from gasoline engine 
crankcases have been controlled for many years by sealing the crankcase 
and routing the gases into the intake air through a positive crankcase 
ventilation (PCV) valve. However, in the past there have been concerns 
about applying a similar technology for diesel engines. For example, 
high PM emissions venting into the intake system could foul 
turbocharger compressors. As a result of this concern, diesel-fueled 
and other compression-ignition engines equipped with turbochargers (or 
other equipment) were not required to have sealed crankcases (see 40 
CFR 86.007-11(c)). For these engines, manufacturers are allowed to vent 
the crankcase emissions to ambient air as long as they are measured and 
added to the exhaust emissions during all emission testing to ensure 
compliance with the emission standards. Because all new highway heavy-
duty diesel engines on the market today are equipped with 
turbochargers, they are not required to have closed crankcases under 
the current regulations. Chapter 1.1.4 of the RIA describes EPA's 
recent test program to evaluate the emissions from open crankcase 
systems on two modern heavy-duty diesel engines. Results suggest HC and 
CO emitted from the crankcase can be a notable fraction of overall 
tailpipe emissions. By closing the crankcase, those emissions would be 
rerouted to the engine or aftertreatment system to ensure emission 
control.
2. Test Procedures and Standards
    As described in Section III.B.3.ii, we have determined that the 
technology packages evaluated for this final action can achieve the new 
duty-cycle standards. We are finalizing a single set of standards that 
take effect starting in MY 2027, including not only new numerical 
standards for new and existing duty-cycles but also other new numerical 
standards for revised off-cycles test procedures and compliance 
provisions, longer useful life periods, and other requirements.
    The final standards were derived to achieve the maximum feasible 
emissions reductions from heavy-duty diesel engines for MY 2027, 
considering lead time, stability, cost, energy, and safety. To 
accomplish this, we evaluated what operation made up the greatest part 
of the inventory, as discussed in Section VI.B, and what technologies 
can be used to reduce emissions in these areas. As discussed in Section 
I, we project that emissions from operation at low power, medium-to-
high power, and mileages beyond the current regulatory useful life of 
the engine will account for the majority of heavy-duty highway 
emissions in 2045. To achieve reductions in these three areas, we 
identified options for cycle-specific standards to ensure that the 
maximum achievable reductions are seen across the operating range of 
the engine. As described in Section IV, we are finalizing an increase 
in the regulatory useful life periods for each heavy-duty engine class 
to ensure these new standards are met for a greater portion of the 
engine's operational life. Also as described in Section IV, we are 
separately lengthening the warranty periods for each heavy-duty engine 
class, which is expected to help to maintain the benefits of the 
emission controls for a greater portion of the engine's operational 
life.
    To achieve the goal of reducing emissions across the operating 
range of the engine, we are finalizing standards for three duty cycles 
(SET, FTP, and LLC). In finalizing these standards, we assessed the 
performance of the best available aftertreatment systems under various 
operating conditions. For example, we observed that these systems are 
more effective at reducing NOX emissions at the higher 
exhaust temperatures that occur at high engine power than they are at 
reducing NOX emissions at low exhaust temperatures that 
occur at low engine power. To achieve the maximum NOX 
reductions from the engine at maximum power, the aftertreatment system 
was designed to ensure that the downstream selective catalytic 
reduction (SCR) catalyst was properly sized, diesel exhaust fluid (DEF) 
was fully mixed with the exhaust gas ahead of the SCR catalyst and the 
diesel oxidation catalyst (DOC) was designed to provide a molar ratio 
of NO to NO2 of near one. The final standards for the FTP 
and LLC are 80 to 90 percent, or more, lower as compared to current 
standards, which will contribute to reductions in emissions under low 
power operation and under cold-start conditions. The standards are 
achievable by utilizing cylinder deactivation (CDA), dual-SCR 
aftertreatment configuration, closed crankcase, and heated diesel 
exhaust fluid (DEF) dosing. To reduce emissions under medium to high 
power, the final standards for the SET are greater than 80 percent 
lower as compared to current standards. The SET standards are 
achievable by utilizing improvements to the SCR formulation, SCR 
catalyst sizing, and improved mixing of DEF with the exhaust. Further 
information about these technologies can be found in Chapters 1 and 3 
of the RIA.
    The final PM standards are set at a level that requires heavy-duty 
engines to maintain the emissions performance of current diesel 
engines. The final standards for HC and CO are set at levels that are 
equivalent to the maximum emissions reductions achievable by spark-
ignition engines over the FTP, with the general intent of making the 
final standards fuel neutral.243 244 Compared to current 
standards, the final standards for the SET and FTP duty cycles are 50 
percent lower for PM, 57 percent lower for HC, and 61 percent lower for 
CO. Each of these standards are discussed in more detail in the 
following sections.
---------------------------------------------------------------------------

    \243\ See Section III.D for a discussion of these standards as 
they relate to Spark-ignition HDE.
    \244\ See 65 FR 6728 (February 10, 2000) and 79 FR 23454 (April 
28, 2014) for more discussion on the principle of fuel neutrality 
applied in recent rulemakings for light-duty vehicle criteria 
pollutant standards.
---------------------------------------------------------------------------

    For Heavy HDE, we are finalizing NOX standards to a 
useful life of 650,000 miles with a durability demonstration out to 
750,000 miles, as discussed later in Section III.B.2. We recognize the 
greater demonstration burden of a useful life of 650,000 miles for 
these engines, and after careful analysis are updating our DF 
demonstration provisions to include two options for an accelerated 
aging demonstration. However, we also are taking into account that 
extending a durability demonstration, given that it is conducted in the 
controlled laboratory environment, will better ensure the final 
standards will be met throughout the longer final regulatory useful 
life mileage of 650,000 miles when these engines are operating in the 
real-world where conditions are more variable. We are thus requiring 
the durability demonstration to show that the emission control system 
hardware is designed to comply with the NOX standards out to 
750,000 miles. As discussed further in Section III.B, the aging 
demonstration out to 750,000 miles in a controlled laboratory 
environment ensures that manufacturers are designing Heavy HDE to meet 
the

[[Page 4334]]

final standards out to the regulatory useful life of 650,000 miles once 
the engine is in the real-world, while reducing the risk of greater 
real world uncertainties impacting emissions at the longest useful life 
mileages in the proposed rule. This approach both sets standards that 
result in the maximum emission reductions achievable in MY 2027 while 
addressing the technical issues raised by manufacturers regarding 
various uncertainties in variability and the degradation of system 
performance over time due to contamination of the aftertreatment from, 
for example, fuel contamination (the latter of which is out of the 
manufacturer's control).
    As discussed in Section III.B.3, we have assessed the feasibility 
of the standards for compression-ignition engines by testing a Heavy 
HDE equipped with cylinder CDA technology, closed crankcase, and dual-
SCR aftertreatment configuration with heated DEF dosing. The 
demonstration work consisted of two phases. The first phase of the 
demonstration was led by CARB and is referred to as CARB Stage 3. In 
this demonstration the aftertreatment was chemically- and 
hydrothermally-aged to the equivalent of 435,000 miles. During this 
aging the emissions performance of the engine was assessed after the 
aftertreatment was degreened \245\, at the equivalent of 145,000 miles, 
290,000 miles and 435,000 miles. The second phase of the demonstration 
was led by EPA and is referred to as the EPA Stage 3 engine. In this 
phase, improvements were made to the aftertreatment by replacing the 
zone-coated catalyzed soot filter with a separate DOC and diesel 
particulate filter (DPF) that were chemically- and hydrothermally-aged 
to the equivalent of 800,000 miles and improving the mixing of the DEF 
with exhaust prior to the downstream SCR catalyst. The EPA Stage 3 
engine was tested at an age equivalent to 435,000, 600,000, and 800,000 
miles. We also tested two additional aftertreatment systems, referred 
to as ``System A'' and ``System B,'' which are each also a dual-SCR 
aftertreatment configuration with heated DEF dosing. However, they each 
have unique catalyst washcoat formulation and the ``System A'' 
aftertreatment has greater SCR catalyst volume. The details of these 
aftertreatment systems, along with the test results, can be found in 
RIA Chapter 3.
---------------------------------------------------------------------------

    \245\ Degreening is a process by which the catalyst is broken in 
and is critical in order to obtain a stable catalyst prior to 
assessing the catalyst's performance characteristics.
---------------------------------------------------------------------------

i. FTP
    We are finalizing new emission standards for testing over the FTP 
duty cycle, as shown in Table III-3.\246\ These brake-specific FTP 
standards apply across the Heavy HDE, Medium HDE, and Light HDE primary 
intended service classes over the useful life periods shown in Table 
III-4.\247\ The numeric levels of the NOX FTP standards at 
the time of certification are consistent with the most stringent 
proposed for MY 2027; as summarized in Section III.A.2 and detailed in 
this Section III.B we are also finalizing an interim, in-use compliance 
allowance for Medium and Heavy HDEs. The numeric level of the PM and CO 
FTP standards are the same as proposed, and the numeric level of the HC 
FTP standard is consistent with the proposed Option 1 standard starting 
in MY 2027. These standards have been shown to be feasible for 
compression-ignition engines based on testing of the CARB Stage 3 and 
EPA Stage 3 engine with a chemically- and hydrothermally-aged 
aftertreatment system.\248\ The EPA Stage 3 engine, was aged to and 
tested at the equivalent of 800,000 miles.\249\ EPA's System A 
demonstration engine, was aged to and tested at the equivalent of 
650,000 miles.\250\ The System B demonstration engine was not aged and 
was only tested after it was degreened. A summary of the data used for 
EPA's feasibility analysis can be found in Section III.B.3. See Section 
III.B.3 for details on how we addressed compliance margin when setting 
the standards, including discussion of the interim in-use testing 
allowance for Medium and Heavy HDE for determining the interim in-use 
testing standards for these primary intended service classes.
---------------------------------------------------------------------------

    \246\ See 40 CFR 1036.510 for the FTP duty-cycle test procedure.
    \247\ The same FTP duty-cycle standards apply for Spark-ignition 
HDE as discussed in Section III.D.
    \248\ See Section III.B.2 for a description of the engine.
    \249\ For the EPA Stage 3 engine, the data at the equivalent of 
435,000 and 600,000 miles were included in the preamble of the NPRM 
and the data at the equivalent of 800,000 miles was added to the 
docket on May 5th, 2022.
    \250\ Due to the timing of when the data from the System A 
system were available, the data were added to the public docket 
prior to the signing of the final rule.

            Table III-3--Final Compression-Ignition Engine Standards Over the SET and FTP Duty Cycles
----------------------------------------------------------------------------------------------------------------
                                                  NOX (mg/hp-hr)
                   Model year                                      HC (mg/hp-hr)   PM (mg/hp-hr)   CO (g/hp-hr)
----------------------------------------------------------------------------------------------------------------
2027 and later..................................          \a\ 35              60               5             6.0
----------------------------------------------------------------------------------------------------------------
\a\ An interim NOX compliance allowance of 15 mg/hp-hr applies for any in-use testing of Medium HDE and Heavy
  HDE. Manufacturers will add the compliance allowance to the NOX standard that applies for each duty cycle and
  for off-cycle Bin 2, for both in-use field testing and laboratory testing as described in 40 CFR part 1036,
  subpart E. Note, the NOX compliance allowance doesn't apply to confirmatory testing described in 40 CFR
  1036.235(c) or selective enforcement audits described in 40 CFR part 1068.

      Table III-4--Useful Life Periods for Heavy-Duty Compression-Ignition Primary Intended Service Classes
----------------------------------------------------------------------------------------------------------------
                                            Current (Pre-MY 2027)                 Final MY 2027 and later
  Primary intended service class   -----------------------------------------------------------------------------
                                       Miles        Years        Hours        Miles        Years        Hours
----------------------------------------------------------------------------------------------------------------
Light HDE \a\.....................      110,000           10  ...........      270,000           15       13,000
Medium HDE........................      185,000           10  ...........      350,000           12       17,000
Heavy HDE.........................      435,000           10       22,000      650,000           11       32,000
----------------------------------------------------------------------------------------------------------------
\a\ Current useful life period for Light HDE for GHG emission standards is 15 years or 150,000 miles; we are not
  revising GHG useful life periods in this final rule. See 40 CFR 1036.108(d).

[[Page 4335]]

    As further discussed in Section III.B.3, taking into account 
measurement variability of the PM measurement test procedure and the 
low numeric level of the new PM standards, we believe PM emissions from 
current diesel engines are at the lowest feasible level for standards 
starting in MY 2027. As summarized in Section III.B.3.ii.b, 
manufacturers are submitting certification data to the agency for 
current production engines well below the existing PM standards over 
the FTP duty cycle. Setting the new PM FTP standards lower than the 
existing FTP PM standards, at 5 mg/hp-hr (0.005 g/hp-hr), ensures that 
future engines will maintain the low level of PM emissions of the 
current engines and not increase PM emissions. We received comment 
stating that a 5 mg/hp-hr standard did not provide enough margin for 
some engine designs and that a 7.5 mg/hp-hr would be a more appropriate 
standard to maintain current PM emissions levels while providing enough 
margin to account for the measurement variability of the PM measurement 
test procedure. The reason submitted in comment to justify the 7.5 mg/
hp-hr standard was that data from the Stage 3 testing at Southwest 
Research Institute (SwRI) shows that in some conditions PM values 
exceed the 5 mg/hp-hr emission standard. EPA took a further look at 
this data and determined that the higher PM emission data points occur 
immediately following DPF ash cleaning, and that the PM level returns 
to a level well below the 5 mg/hp-hr standards shortly after return to 
service once a soot cake layer reestablishes itself in the DPF. EPA 
concluded from this assessment that these very short-term elevations in 
PM that occur after required maintenance of the DPF should not be the 
basis for the stringency of the PM standards and that the standards are 
feasible.
    As noted earlier in this section, we are finalizing HC and CO FTP 
standards based on the feasibility demonstration for SI engines. As 
summarized in Section III.B.3.ii.b, manufacturers are submitting data 
to the agency that show emissions performance for current production CI 
engines that are well below the current standards. Keeping FTP 
standards at the same value for all fuels is consistent with the 
agency's approach to previous criteria pollutant standards. See Section 
III.D for more information on how the numeric values of the HC and CO 
standards were determined.
    In the NPRM, we did not propose any changes to the weighting 
factors for the FTP cycle for heavy-duty engines. The current FTP 
weighting of cold-start and hot-start emissions was promulgated in 1980 
(45 FR 4136, January 21, 1980). It reflects the overall ratio of cold 
and hot operation for heavy-duty engines generally and does not 
distinguish by engine size or intended use. We received comment to 
change the weighting factors to reduce the effect of the cold start 
portion of the FTP on the composite FTP emission results or to add 300 
seconds of idle before the first acceleration in the cold start FTP to 
reduce the emissions impact of the cold start on the first 
acceleration. Duty-cycles are an approximation of the expected real-
world operation of the engine and no duty cycle captures all aspects of 
the real-world operation. Changing the cold/hot weighting factors would 
not fully capture all aspects of what really occurs in-use, and there 
is precedent in experience and historical approach with the current \1/
7\ cold and \6/7\ hot weighting factors. Adding 300 seconds of idle to 
the beginning of the FTP would simply reduce the stringency of the 
standard by reducing the impact of cold start emissions, as the 300 
seconds of idle would allow the aftertreatment to light off prior to 
the first major acceleration in the FTP. Although the case can be made 
that many vehicles idle for some amount of time after start up, any 
attempt to add idle time before the first acceleration is simply an 
approximation and this ``one size fits all'' approach doesn't afford an 
improvement over the current FTP duty-cycle, nor does it allow 
determination of cold start emissions where the vehicle is underway 
shortly after start up. After considering these comments we are also 
not including any changes to the weighting factors for the FTP duty-
cycle in this final rule.
    For Heavy HDE, we are finalizing test procedures for the 
determination of deterioration factors in 40 CFR 1036.245 that require 
these engines to be aged to an equivalent of 750,000 miles, which is 15 
percent longer than the regulatory useful life of those engines. As 
explained earlier in this section, we are finalizing this requirement 
for Heavy HDE to ensure the final NOX standard will be met 
through the lengthy regulatory useful life of 650,000 miles. See 
preamble Section IV.A for details on how we set the regulatory useful 
life for Heavy HDE.
ii. SET
    We are finalizing new emissions standards for testing over the SET 
duty-cycle as shown in Table III-3. These brake-specific SET standards 
apply across the Heavy HDE, Medium HDE, and Light HDE primary intended 
service classes, as well as the SI HDE primary intended service class 
as discussed in Section III.D, over the same useful life periods shown 
in Table III-4. The numeric levels of the NOX SET standards 
at the time of certification are consistent with the most stringent 
standard proposed for MY 2027.\251\ The numeric level of the CO SET 
standard is consistent with the most stringent standard proposed for MY 
2027 for all CI engine classes.\252\ The numeric level of the PM SET 
standard is the same as proposed, and the numeric level of the HC SET 
standard is consistent with the proposed Option 1 standard starting in 
MY 2027. Consistent with our current standards, we are finalizing the 
same numeric values for the standards over the SET and FTP duty cycles 
for the CI engine classes. As with the FTP cycle, the standards have 
been shown to be feasible for compression-ignition engines based on 
testing of the CARB Stage 3 and EPA Stage 3 engines with a chemically- 
and hydrothermally-aged aftertreatment system. The EPA Stage 3 engine 
was aged to and tested at the equivalent of 800,000 miles.\253\ EPA's 
Team A demonstration engine was aged to and tested at the equivalent of 
650,000 miles.\254\ See Section III.B.3 for details on how we addressed 
compliance margin when setting the standards, including discussion of 
the interim in-use testing allowance for Medium and Heavy HDEs for 
determining the interim in-use testing standards for these primary 
intended service classes. A summary of the data used for EPA's 
feasibility analysis can be found in Section III.B.3.
---------------------------------------------------------------------------

    \251\ As discussed in Section III.B.3, we are finalizing an 
interim, in-use compliance allowance that applies when Medium and 
Heavy HDE are tested in-use.
    \252\ As explained in Section III.D.1.ii, the final Spark-
ignition HDE CO standard for the SET duty-cycle is 14.4 g/hp-hr.
    \253\ For the EPA Stage 3 engine, the data at the equivalent of 
435,000 and 600,000 miles were included in the preamble of the NPRM 
and the data at the equivalent of 800,000 miles was added to the 
docket on May 5th, 2022.
    \254\ Due to the timing of when the data from the System A 
system were available, the data were added to the public docket 
prior to the signing of the final rule.
---------------------------------------------------------------------------

    As with the PM standards for the FTP (see Section III.B.2.i), and 
as further discussed in Section III.B.3, taking into account 
measurement variability of the PM measurement test procedure and the 
low numeric level of the new PM standards, we believe PM emissions from 
current diesel engines are at the lowest feasible level for standards 
starting in MY 2027. Thus, the PM standard for the SET duty-cycle is 
intended to ensure that there is not an increase in PM emissions from 
future engines. We are finalizing new PM SET

[[Page 4336]]

standards of 5 mg/hp-hr for the same reasons outlined for the FTP in 
Section III.B.2.i. Also similar to the FTP (see Section III.B.2.i), we 
are finalizing HC and CO SET standards based on the feasibility 
demonstration for SI engines (see Section III.D).
    We have also observed an industry trend toward engine down-
speeding--that is, designing engines to do more of their work at lower 
engine speeds where frictional losses are lower. To better reflect this 
trend in our duty cycle testing, in the HD GHG Phase 2 final rule we 
promulgated new SET weighting factors for measuring CO2 
emissions (81 FR 73550, October 25, 2016). Since we believe these new 
weighting factors better reflect in-use operation of current and future 
heavy-duty engines, we are finalizing application of these new 
weighting factors to criteria pollutant measurement, as show in Table 
III-5, for NOX and other criteria pollutants as well. To 
assess the impact of the new test cycle on criteria pollutant 
emissions, we analyzed data from the EPA Stage 3 engine that was tested 
on both versions of the SET. The data summarized in Section 
III.B.3.ii.a show that the NOX emissions from the EPA Stage 
3 engine at an equivalent of 435,000 miles are slightly lower using the 
SET weighting factors in 40 CFR 1036.510 versus the current SET 
procedure in 40 CFR 86.1362. The lower emissions using the SET cycle 
weighting factors in 40 CFR 1036.510 are reflected in the stringency of 
the final SET standards.

               Table III-5--Weighting Factors for the SET
------------------------------------------------------------------------
                                                             Weighting
                      Speed/% load                          factor (%)
------------------------------------------------------------------------
Idle....................................................              12
A, 100..................................................               9
B, 50...................................................              10
B, 75...................................................              10
A, 50...................................................              12
A, 75...................................................              12
A, 25...................................................              12
B, 100..................................................               9
B, 25...................................................               9
C, 100..................................................               2
C, 25...................................................               1
C, 75...................................................               1
C, 50...................................................               1
                                                         ---------------
    Total...............................................             100
Idle Speed..............................................              12
Total A Speed...........................................              45
Total B Speed...........................................              38
Total C Speed...........................................               5
------------------------------------------------------------------------

iii. LLC
    EPA is finalizing the addition of new standards for testing over 
the new low-load duty-cycle, that will require CI engine manufacturers 
to demonstrate that the emission control system maintains functionality 
during low-load operation where the catalyst temperatures have 
historically been found to be below the catalyst's operational 
temperature (see Chapter 2.2.2 of the RIA). We believe the addition of 
this LLC will complement the expanded operational coverage of our new 
off-cycle testing requirements (see Section III.C).
    During ``Stage 2'' of the CARB Low NOX Demonstration 
program, SwRI and NREL developed several candidate cycles with average 
power and duration characteristics intended to test current diesel 
engine emission controls under three low-load operating conditions: 
Transition from high- to low-load, sustained low-load, and transition 
from low- to high-load.\255\ In September 2019, CARB selected the 92-
minute ``LLC Candidate #7'' as the low load cycle they adopted for 
their Low NOX Demonstration program and subsequent Omnibus 
regulation.256 257
---------------------------------------------------------------------------

    \255\ California Air Resources Board. ``Heavy-Duty Low 
NOx Program Public Workshop: Low Load Cycle 
Development''. Sacramento, CA. January 23, 2019. Available online: 
https://ww3.arb.ca.gov/msprog/hdlownox/files/workgroup_20190123/02-llc_ws01232019-1.pdf.
    \256\ California Air Resources Board. Heavy-Duty Omnibus 
Regulation. Available online: https://ww2.arb.ca.gov/rulemaking/2020/hdomnibuslownox.
    \257\ California Air Resources Board. ``Heavy-Duty Low 
NOx Program: Low Load Cycle'' Public Workshop. Diamond 
Bar, CA. September 26, 2019. Available online: https://ww3.arb.ca.gov/msprog/hdlownox/files/workgroup_20190926/staff/03_llc.pdf.
---------------------------------------------------------------------------

    We are adopting CARB's Omnibus LLC as a new duty-cycle, the LLC. 
This cycle is described in Chapter 2 of the RIA for this rulemaking and 
the test procedures are specified in 40 CFR 1036.514. The LLC includes 
applying the accessory loads defined in the HD GHG Phase 2 rule, that 
were based on data submitted to EPA as part of the development of the 
HD GHG Phase 2. These accessory loads are 1.5, 2.5 and 3.5 kW for Light 
HDE, Medium HDE, and Heavy HDE engines, respectively. As detailed 
further in section 3 of the Response to Comments, we received comments 
that EPA should revise the accessory loads. One commenter provided 
specific recommendations for engines installed in tractors but in all 
cases commenters didn't provide data to support their comments; after 
consideration of these comments and further consideration of the basis 
of the proposal, we are finalizing the accessory loads for the LLC as 
proposed. To allow vehicle level technologies to be recognized on this 
cycle, we are including a powertrain test procedure option for the LLC. 
More information on the powertrain test procedure can be found in 
Section III.B.2.v. IRAF determination for the LLC follows the test 
procedures defined in 40 CFR 1036.580, which are the same test 
procedures used for the SET and FTP. The IRAF test procedures that 
apply to the SET and FTP in 40 CFR 1065.680 are appropriate for the LLC 
as the procedures in 40 CFR 1065.680 were developed to work with any 
engine-based duty-cycle. We are finalizing as proposed that, while the 
IRAF procedures in 40 CFR 1036.580 and 1065.680 require that 
manufacturers determine an IRAF for the SET, FTP, and LLC duty cycles, 
manufacturers may omit the adjustment factor for a given duty cycle if 
they determine that infrequent regeneration does not occur over the 
types of engine operation contained in the duty cycle as described in 
40 CFR 1036.580(c).
    The final emission standards for the LLC are presented in Table 
III-6, over the useful life periods shown in Table III-4. The numeric 
levels of the NOX LLC standards at the time of certification 
are the most stringent proposed for any model year.\258\ The numeric 
level of the PM and CO LLC standards are the same as proposed, and the 
numeric level of the HC LLC standard is consistent with the proposed 
Option 1 standard starting in MY 2027. As with the FTP cycle, these 
standards have been shown to be feasible for compression-ignition 
engines based on testing of the EPA Stage 3 demonstration engine with 
chemically- and hydrothermally-aged aftertreatment system, and for the 
LLC the data shows that the standards are feasible for all engine 
service classes with available margins between the data and the 
standards. The summary of this data along with how we addressed 
compliance margin can be found in Section III.B.3, including discussion 
of the interim in-use compliance allowance for Medium and Heavy HDEs 
for determining the interim in-use

[[Page 4337]]

standards for these primary intended service classes.
---------------------------------------------------------------------------

    \258\ As summarized in Section III.A.2 and detailed in this 
Section III.B we are also finalizing an interim, in-use compliance 
allowance for medium and heavy heavy-duty engines.

                   Table III-6--Compression-Ignition Engine Standards Over the LLC Duty Cycle
----------------------------------------------------------------------------------------------------------------
                                                  NOX (mg/hp-hr)
                   Model year                                      PM (mg/hp-hr)   HC (mg/hp-hr)   CO (g/hp-hr)
----------------------------------------------------------------------------------------------------------------
2027 and later..................................          \a\ 50               5             140             6.0
----------------------------------------------------------------------------------------------------------------
\a\ An interim NOX compliance allowance of 15 mg/hp-hr applies for any in-use testing of Medium HDE and Heavy
  HDE. Manufacturers will add the compliance allowance to the NOX standard that applies for each duty cycle and
  for off-cycle Bin 2, for both in-use field testing and laboratory testing as described in 40 CFR part 1036,
  subpart E. Note, the NOX compliance allowance doesn't apply to confirmatory testing described in 40 CFR
  1036.235(c) or selective enforcement audits described in 40 CFR part 1068.

    We are finalizing an LLC PM standard of 5 mg/hp-hr for the same 
reasons outlined for the FTP in Section III.B.2.i. We are finalizing HC 
and CO standards based on data from the CARB and EPA Stage 3 engine 
discussed in Section III.B.3. We are finalizing the same numeric 
standard for CO on the LLC as we have for the SET and FTP cycles 
because the demonstration data from the EPA Stage 3 engine shows that 
CO emissions on the LLC are similar to CO emissions from the SET and 
FTP. We are finalizing HC standards that are different than the 
standards of the SET and FTP cycles, to reflect our assessment of the 
performance of the EPA Stage 3 engine on the LLC. The data discussed in 
Section III.B.3 of this preamble shows that the PM, HC, and CO 
standards are feasible for both current and future new engines.
iv. Idle
    CARB currently has an optional idle test procedure and accompanying 
standard of 30 g/hr of NOX for diesel engines to be ``Clean 
Idle Certified.''.\259\ In the CARB Omnibus rule, the CARB lowered the 
optional NOX standard to 10 g/hr for MY 2024 to MY 2026 
engines and 5 g/hr for MY 2027 and beyond. In the NPRM, we proposed 
optional NOX idle standards with a corresponding idle test 
procedure, with potentially different numeric levels of the 
NOX idle standards for MY 2023, MY 2024 to MY 2026 engines, 
and for MY 2027 and beyond, that would allow compression ignition 
engine manufacturers to voluntarily choose to certify (i.e., it would 
be optional for a manufacturer to include the idle standard in an EPA 
certification but once included the idle standard would become 
mandatory and full compliance would be required). We proposed to 
require that the brake-specific HC, CO, and PM emissions during the 
Clean Idle test may not exceed measured emission rates from the idle 
mode in the SET or the idle segments of the FTP, in addition to meeting 
the applicable idle NOX standard. We requested comment on 
whether EPA should make the idle standards mandatory instead of 
voluntary for MY 2027 and beyond, as well as whether EPA should set 
clean idle standards for HC, CO, and PM emissions (in g/hr) rather than 
capping the idle emissions for those pollutants based on the measured 
emission levels during the idle mode in the SET or the idle segments of 
the FTP. We also requested comment on the need for EPA to define a 
label that would be put on the vehicles that are certified to the 
optional idle standard.
---------------------------------------------------------------------------

    \259\ 13 CCR 1956.8(a)(6)(C)--Optional NOX idling 
emission standard.
---------------------------------------------------------------------------

    We received comments on the EPA's proposal to adopt California's 
Clean Idle NOX standard as a voluntary emission standard for 
Federal certification.\260\ All commenters provided general support for 
EPA's proposal to set idle standards for heavy duty engines, with some 
qualifications. Some commentors supported making idle standards 
mandatory, while others commented that the idle standards should be 
optional. With regard to the level of the idle standard, there was 
support from many commenters that the standards should be set at the 
Proposed Option 1 levels or lower, while several manufactures stated 
that 10 g/hr for certification and 15 g/hr in-use would be the lowest 
feasible standards for NOX. One manufacturer commented that 
EPA must set standards that do not increase CO2 emissions. 
EPA has considered these comments, along with the available data 
including the data from the EPA Stage 3 engine,\261\ and we are 
finalizing optional idle standards in 40 CFR 1036.104(b) and a new idle 
test procedure in 40 CFR 1036.525. The standards are based on CARB's 
test procedure with revisions to not require the measurement of PM, HC 
and CO,\262\ to allow compression-ignition engine manufacturers to 
voluntarily certify to an idle NOX standard of 30.0 g/hr for 
MY 2024 to MY 2026, which is consistent with proposed Option 1 for MY 
2023. For MY 2027 and beyond, the final NOX idle standard is 
10.0 g/hr, which is the same as proposed Option 2 for those MYs. 
Manufacturers certifying to the optional idle standard must comply with 
the standard and related requirements as if they were mandatory.
---------------------------------------------------------------------------

    \260\ See RTC section 3.
    \261\ See RIA Chapter 3 for a summary of the data collected with 
the EPA Stage 3 engine run on the Clean Idle test in three 
configurations. These data show that the MY 2027 and beyond, final 
NOX idle standard of 10 g/hr is feasible through useful 
life with margin, and show that an additional 5 g/hr in-use margin 
is not justified.
    \262\ 86.1360-2007.B.4, California Exhaust Emission Standards 
and Test Procedures for 2004 and Subsequent Model Heavy-Duty Diesel 
Engines and Vehicles, April 18, 2019.
---------------------------------------------------------------------------

    We received comments stating that the proposed PM, HC, and CO 
standards are unworkable since the standards are set at the level the 
engine emits at during idle over the engine SET and FTP duty cycles and 
that variability in the emissions between the different tests could 
cause the engine to fail the idle PM, HC, and CO standards. EPA 
recognized this issue in the proposal and requested comment on if EPA 
should instead set PM, HC, and CO standards that are fixed and not 
based on the emissions from the engine during the SET and FTP. EPA has 
considered these comments and we are not finalizing the proposed 
requirement to measure brake-specific HC, CO, and PM emissions during 
the Clean Idle test for comparison to emission rates from the idle 
modes in the SET or the idle segments of the FTP.\263\ The measurement 
of these additional pollutants would create unnecessary test burden for 
the manufacturers at this time, especially with respect to measuring PM 
during idle segments of the SET or FTP as it would require running 
duplicate tests or adding a PM sampler. Further, setting the PM, HC and 
CO standards right at the idle emissions level of the engine on the SET 
and FTP could cause false failures due to test-to-test variability from 
either the SET or FTP, or the Clean Idle test itself.

[[Page 4338]]

Idle operation is included as part of off-cycle testing and the SET, 
FTP, and LLC duty cycles; standards for off-cycle and duty-cycle 
testing ensure that emissions of HC, CO, and PM are well controlled as 
aftertreatment temperatures are not as critical to controlling these 
pollutants over extended idle periods as they are for NOX. 
We are therefore not requiring the measurement of these other 
pollutants to meet EPA voluntary clean idle standards.
---------------------------------------------------------------------------

    \263\ See 40 CFR 1036.104(b).
---------------------------------------------------------------------------

    We are finalizing a provision in new 40 CFR 1036.136 requiring 
engine manufacturers that certify to the Federal Clean Idle 
NOX standard to create stickers to identify their engines as 
meeting the Federal Clean Idle NOX standard. The regulatory 
provisions require that the stickers meet the same basic requirements 
that apply for stickers showing that engines meet CARB's Clean Idle 
NOX standard. For example, stickers must be durable and 
readable throughout each vehicle's operating life, and the preferred 
placement for Clean Idle stickers is on the driver's side of the hood. 
Engine manufacturers must provide exactly the right number of these 
stickers to vehicle manufacturers so they can apply the stickers to 
vehicles with the engines that the engine manufacturer has certified to 
meet the Federal Clean Idle NOX standard. If engine 
manufacturers install engines in their own vehicles, they must apply 
the stickers themselves to the appropriate vehicles. Engine 
manufacturers must keep the following records for at least five years: 
(1) Written documentation of the vehicle manufacturer's request for a 
certain number of stickers, and (2) tracking information for stickers 
the engine manufacturer sends and the date they sent them. 40 CFR 
1036.136 also clarifies that the provisions in 40 CFR 1068.101 apply 
for the Clean Idle sticker in the same way that those provisions apply 
for emission control information labels. For example, manufacturing, 
selling, and applying false labels are all prohibited actions subject 
to civil penalties.
v. Powertrain
    EPA recently finalized a separate rulemaking that included an 
option for manufacturers to certify a hybrid powertrain to the SET and 
FTP greenhouse gas engine standards by using a powertrain test 
procedure (86 FR 34321, June 29, 2021).\264\ In this rulemaking, we are 
similarly finalizing as proposed that manufacturers may certify hybrid 
powertrains to criteria pollutant emissions standards by using the 
powertrain test procedure. In this section we describe how 
manufacturers would apply the powertrain test procedure to certify 
hybrid powertrains.
---------------------------------------------------------------------------

    \264\ The powertrain test procedure was established in the GHG 
Phase 1 rulemaking but the recent rulemaking included adjustments to 
apply the test procedure to the engine test cycles.
---------------------------------------------------------------------------

a. Development of Powertrain Test Procedures
    Powertrain testing allows manufacturers to demonstrate emission 
benefits that cannot be captured by testing an engine alone on a 
dynamometer. For hybrid engines and powertrains, powertrain testing 
captures when the engine operates less or at lower power levels due to 
the use of the hybrid powertrain function. However, powertrain testing 
requires the translation of an engine test procedure to a powertrain 
test procedure. Chapter 2 of the RIA describes how we translated the 
SET, FTP, and LLC engine test cycles to the powertrain test 
cycles.\265\ The two primary goals of this process were to make sure 
that the powertrain version of each test cycle was equivalent to each 
respective engine test cycle in terms of positive power demand versus 
time and that the powertrain test cycle had appropriate levels of 
negative power demand. To achieve this goal, over 40 engine torque 
curves were used to create the powertrain test cycles.
---------------------------------------------------------------------------

    \265\ As discussed in Section III.B.1, as part of the technical 
amendments rulemaking, EPA finalized that manufacturers may use the 
powertrain test procedure for GHG emission standards on the FTP and 
SET engine-based test cycles. In this rulemaking we are extending 
this to allow the powertrain test procedure to be used for criteria 
emission standards on these test cycles and the LLC. As discussed in 
Section 2.ii, we are setting new weighting factors for the engine-
based SET procedure for criteria pollutant emissions, which are 
reflected in the SET powertrain test cycle.
---------------------------------------------------------------------------

b. Testing Hybrid Engines and Hybrid Powertrains
    As noted in the introduction of this Section III, we are finalizing 
clarifications in 40 CFR 1036.101 that manufacturers may optionally 
test the hybrid engine and hybrid powertrain to demonstrate compliance. 
We are finalizing as proposed with one clarification that the 
powertrain test procedures specified in 40 CFR 1036.510 and 1036.512, 
which were previously developed for demonstrating compliance with GHG 
emission standards on the SET and FTP test cycles, are applicable for 
demonstrating compliance with criteria pollutant standards on the SET 
and FTP test cycles. The clarification in 40 CFR 1036.510 provides 
direction that the idle points in the SET should be run as neutral or 
parked idle. In addition, for GHG emission standards we are finalizing 
updates to 40 CFR 1036.510 and 1036.512 to further clarify how to carry 
out the test procedure for plug-in hybrids. We have done additional 
work for this rulemaking to translate the LLC to a powertrain test 
procedure, and we are finalizing that manufacturers can similarly 
certify hybrid engines and hybrid powertrains to criteria pollutant 
emission standards on the LLC using the test procedures defined in 40 
CFR 1036.514.
    We are allowing manufacturers to use the powertrain test procedures 
to certify hybrid engine and powertrain configurations to all MY 2023 
and later criteria pollutant engine standards. Manufacturers can choose 
to use either the SET duty-cycle in 40 CFR 86.1362 or the SET in 40 CFR 
1036.510 in model years prior to 2027, and may use only the SET in 40 
CFR 1036.510 for model year 2027 and beyond.\266\ \267\
---------------------------------------------------------------------------

    \266\ We are allowing either the SET duty-cycle in 40 CFR 
86.1362 or 40 CFR 1036.505 because the duty cycles are similar and, 
as shown in Chapter 3.1.2 of the RIA, the criteria pollutant 
emissions level of current production engines is similar between the 
two cycles.
    \267\ Prior to MY 2027, only manufacturers choosing to 
participate in the 2026 Service Class Pull Ahead Credits, Full 
Credits, or Partial Credits pathways under the Transitional Credits 
Program need to conduct LLC powertrain testing (see Section IV.G for 
details on).
---------------------------------------------------------------------------

    We are allowing the use of these procedures starting in MY 2023 for 
plug-in hybrids and, consistent with the requirements for light-duty 
plug-in hybrids, we are finalizing that the applicable criteria 
pollutant standards must be met under the worst-case conditions, which 
is achieved by testing and evaluating emission under both charge-
depleting and charge-sustaining operation. This is to ensure that under 
all drive cycles the powertrain meets the criteria pollutant standards 
and is not based on an assumed amount of zero emissions range. We 
received comment stating that the charge-depleting and charge-
sustaining operation should be weighted together for criteria 
pollutants as well as GHG pollutants, but consistent with the light-
duty test procedure we want to ensure that criteria pollutant emissions 
are controlled under all conditions, which would include under 
conditions where the vehicle is not charged and is only operated in 
charge sustaining-operation.
    We are finalizing changes to the test procedures defined in 40 CFR 
1036.510 and 1036.512 to clarify how to weight together the charge-
depleting and charge-sustaining greenhouse gas emissions for 
determining the greenhouse gas emissions of plug-in

[[Page 4339]]

hybrids for the SET and FTP duty cycles. This weighting is done using 
an application specific utility factor curve that is approved by EPA. 
We are also finalizing a provision to not apply the cold and hot 
weighting factors for the determination of the FTP composite emission 
result for greenhouse gas pollutants because the charge-depleting and 
sustaining test procedures finalized in 40 CFR 1036.512 include both 
cold and hot start emissions by running repeat FTP cycles back-to-back. 
By running back-to-back FTPs, the finalized test procedure captures 
both cold and hot emissions and their relative contribution to daily 
greenhouse gas emissions per unit work, removing the need for weighting 
the cold and hot emissions.
    We are finalizing the application of the powertrain test procedure 
only for hybrid powertrains, to avoid having two different testing 
pathways (engine only and powertrain) for non-hybrid engines for the 
same standards. That said, we recognize there may be other technologies 
where the emissions performance is not reflected on the engine test 
procedures, so in such cases manufacturers may seek approval from EPA 
to use the powertrain test procedure for non-hybrid engines and 
powertrains consistent with 40 CFR 1065.10(c)(1).
    Finally, for all pollutants, we requested comment on if we should 
remove 40 CFR 1037.551 or limit the use of it to only selective 
enforcement audits (SEAs). 40 CFR 1037.551 was added as part of the HD 
GHG Phase 2 rulemaking to provide flexibility for an SEA or a 
confirmatory test, by allowing just the engine of the powertrain to be 
tested. Allowing just the engine to be tested over the engine speed and 
torque cycle that was recorded during the powertrain test enables the 
testing to be conducted in more widely available engine dynamometer 
test cells, but this flexibility could increase the variability of the 
test results. We didn't receive any comments on this topic and, for the 
reason just stated, we are limiting the use of 40 CFR 1037.551 to SEA 
testing.
vi. Crankcase Emissions
    During combustion, gases can leak past the piston rings sealing the 
cylinder and into the crankcase. These gases are called blowby gases 
and generally include unburned fuel and other combustion products. 
Blowby gases that escape from the crankcase are considered crankcase 
emissions (see 40 CFR 86.402-78). Current regulations restrict the 
discharge of crankcase emissions directly into the ambient air. Blowby 
gases from gasoline engine crankcases have been controlled for many 
years by sealing the crankcase and routing the gases into the intake 
air through a PCV valve. However, in the past there have been concerns 
about applying a similar technology for diesel engines. For example, 
high PM emissions venting into the intake system could foul 
turbocharger compressors. As a result of this concern, diesel-fueled 
and other compression-ignition engines equipped with turbochargers (or 
other equipment) were not required to have sealed crankcases (see 40 
CFR 86.007-11(c)). For these engines, manufacturers were allowed to 
vent the crankcase emissions to ambient air as long as they are 
measured and added to the exhaust emissions during all emission testing 
to ensure compliance with the emission standards.
    Because all new highway heavy-duty diesel engines on the market 
today are equipped with turbochargers, they are not required to have 
closed crankcases under the current regulations. We estimate 
approximately one-third of current highway heavy-duty diesel engines 
have closed crankcases, indicating that some heavy-duty engine 
manufacturers have developed systems for controlling crankcase 
emissions that do not negatively impact the turbocharger. EPA proposed 
provisions in 40 CFR 1036.115(a) to require a closed crankcase 
ventilation system for all highway compression-ignition engines to 
prevent crankcase emissions from being emitted directly to the 
atmosphere starting for MY 2027 engines.\268\ Comments were received 
regarding concerns closing the crankcase that included coking, degraded 
performance and turbo efficiencies leading to increased CO2 
emissions, secondary damage to components, and increased engine-out PM 
(see section 3 of the Response to Comments document for further 
details). After considering these comments, we are finalizing a 
requirement for manufacturers to use one of two options for controlling 
crankcase emissions, either: (1) As proposed, closing the crankcase, or 
(2) an updated version of the current requirements for an open 
crankcase that includes additional requirements for measuring and 
accounting for crankcase emissions. We believe that either approach is 
appropriate, so long as the total emissions are accounted for during 
certification and in-use testing through useful life (including full 
accounting for crankcase emission deterioration).
---------------------------------------------------------------------------

    \268\ We proposed to move the current crankcase emissions 
provisions to a new paragraph (u) in the interim provisions of 40 
CFR 1036.150, which would apply through model year 2026.
---------------------------------------------------------------------------

a. Closed Crankcase Option
    As EPA explained at proposal, the environmental advantages to 
closing the crankcase are twofold. While the exception in the current 
regulations for certain compression-ignition engines requires 
manufacturers to quantify their engines' crankcase emissions during 
certification, they report non-methane hydrocarbons in lieu of total 
hydrocarbons. As a result, methane emissions from the crankcase are not 
quantified. Methane emissions from diesel-fueled engines are generally 
low; however, they are a concern for compression-ignition-certified 
natural gas-fueled heavy-duty engines because the blowby gases from 
these engines have a higher potential to include significant methane 
emissions. We note that in the HD GHG Phase 2 rule we set methane 
standards which required natural gas engines to close the crankcase in 
order to comply with the methane standard. EPA proposed to require that 
all natural gas-fueled engines have closed crankcases in the HD GHG 
Phase 2 rulemaking, but opted to wait to finalize any updates to 
regulations in a future rulemaking, where we could then propose to 
apply these requirements to natural gas-fueled engines and to the 
diesel fueled engines that many of the natural gas-fueled engines are 
based off of (81 FR 73571, October 25, 2016).
    In addition to our concern of unquantified methane emissions, we 
believe another benefit to closed crankcases would be reduced engine 
wear due to improved engine component durability. We know that the 
performance of piston seals reduces as the engine ages, which would 
allow more blowby gases and could increase crankcase emissions. While 
crankcase emissions are currently included in the durability tests that 
estimate an engine's deterioration at useful life, those tests were not 
designed to capture the deterioration of the crankcase. These 
unquantified age impacts continue throughout the operational life of 
the engine. Closing crankcases could be a means to ensure those 
emissions are addressed long-term to the same extent as other exhaust 
emissions.
    After considering all of the manufacturer concerns, we still 
believe, noting that one-third of current highway heavy-duty diesel 
engines have closed crankcases, that improvements in the design of 
engine hardware would allow manufacturers to close the crankcase, with 
the potential for increased maintenance intervals on some

[[Page 4340]]

components. For these reasons, EPA is finalizing provisions in 40 CFR 
1036.115(a) to require a closed crankcase ventilation system as one of 
two options for all highway compression-ignition engines to control 
crankcase emissions for MY 2027 and later engines.
b. Open Crankcase Option
    Given consideration of the concerns from commenters regarding 
engine hardware durability associated with closing the crankcase, we 
have decided to finalize an option that allows the crankcase to remain 
open. This option requires manufacturers of compression ignition 
engines that choose to leave the crankcase open to account for any 
increase in the contribution of crankcase emissions (due to reduction 
in performance of piston seals, etc.) to the total emissions from the 
engine throughout the engine's useful life. Manufacturers that choose 
to perform engine dynamometer-based testing out to useful life will 
provide a deterioration factor that includes deteriorated crankcase 
emissions because the engine components will be aged out to the 
engine's useful life. Manufacturers that choose to use the accelerated 
aging option in 40 CFR 1036.245(b), where the majority of the emission 
control system aging is done, must use good engineering judgment to 
determine the impact of engine deterioration on crankcase emissions and 
adjust the tailpipe emissions at useful life to reflect this 
deterioration. For example, manufacturers may determine deteriorated 
crankcase emissions from the assessment of field-aged engines.
    Manufacturers who choose this option must also account for 
crankcase criteria pollutant emissions during any manufacturer run in-
use testing to determine the overall compliance of the engine as 
described in 40 CFR 1036.415(d)(2). The crankcase emissions must be 
measured separately from the tailpipe emissions or be routed into the 
exhaust system, downstream from the last catalyst in the aftertreatment 
system, to ensure that there is proper mixing of the two streams prior 
to the sample point. In lieu of these two options, manufacturers may 
use the contribution of crankcase emissions over the FTP duty-cycle at 
useful life from the deterioration factor determination testing in 40 
CFR 1036.245, as described in 40 CFR 1036.115(a) and add them to the 
binned emission results determined in 40 CFR 1036.530.
    Chapter 1.1.4 of the RIA describes EPA's recent test program to 
evaluate the emissions from open crankcase systems on two modern heavy-
duty diesel engines. Results suggest HC and CO emitted from the 
crankcase can be a notable fraction of overall tailpipe emissions. By 
closing the crankcase, those emissions would be rerouted to the engine 
or aftertreatment system to ensure control of the crankcase emissions. 
If a manufacturer chooses the option to keep the crankcase open, 
overall emission control will still be achieved, but the manufacturer 
will have to design and optimize the emission control system for lower 
tailpipe emissions to offset the emissions from the crankcase as the 
total emissions are accounted for both in-use and at useful life.
3. Feasibility of the Diesel (Compression-Ignition) Engine Standards
i. Summary of Technologies Considered
    Our finalized standards for compression-ignition engines are based 
on the performance of technology packages described in Chapters 1 and 3 
of the RIA for this rulemaking. Specifically, we are evaluating the 
performance of next-generation catalyst formulations in a dual SCR 
catalyst configuration with a smaller SCR catalyst as the first 
substrate in the aftertreatment system for improved low-temperature 
performance, and a larger SCR catalyst downstream of the diesel 
particulate filter to improve NOX conversion efficiency 
during high power operation and to allow for passive regeneration of 
the particulate filter.\269\ Additionally, the technology package 
includes CDA that reduces the number of active cylinders, resulting in 
increased exhaust temperatures for improved catalyst performance under 
light-load conditions and can be used to reduce fuel consumption and 
CO2 emissions. The technology package also includes the use 
of a heated DEF injector for the upfront SCR catalyst; the heated DEF 
injector allows DEF injection at temperatures as low as approximately 
140[deg]C. The heated DEF injector also improves the mixing of DEF and 
exhaust gas within a shorter distance than with unheated DEF injectors, 
which enables the aftertreatment system to be packaged in a smaller 
space. Finally, the technology package includes hardware needed to 
close the crankcase of diesel engines.
---------------------------------------------------------------------------

    \269\ As described in Chapter 3 of the RIA, we are evaluating 3 
different aftertreatment systems that contain different catalyst 
formulation.
---------------------------------------------------------------------------

ii. Summary of Feasibility Analysis
a. Projected Technology Package Effectiveness and Cost
    Based upon data from EPA's and CARB's Stage 3 Heavy-duty Low 
NOX Research Programs (see Chapter 3.1.1.1 and Chapter 
3.1.3.1 of the RIA), an 80 percent reduction in the Heavy HDE 
NOX standard as compared to the current NOX 
standard is technologically feasible when using CDA or other 
valvetrain-related air control strategies in combination with dual SCR 
systems, and closed crankcase. As noted in the proposal, EPA continued 
to evaluate aftertreatment system durability via accelerated aging of 
advanced emissions control systems as part of EPA's diesel engine 
demonstration program that is described in Chapter 3 of the RIA. In 
assessing the technical feasibility of each of our final standards, we 
have taken into consideration the emissions of the EPA Stage 3 engine 
and other available data, the additional emissions from infrequent 
regenerations, the final longer useful life, test procedure 
variability, emissions performance of other child engines in an engine 
family, production and engine variability, fuel and DEF quality, 
sulfur, soot and ash levels on the aftertreatment, aftertreatment aging 
due to severe-service operation, aftertreatment packaging and lead time 
for manufacturers.
    Manufacturers are required to design engines that meet the duty 
cycle and off-cycle standards throughout the engines' useful life. In 
recognition that emissions performance will degrade over time, 
manufacturers generally design their engines to perform significantly 
better than the standards when first sold to ensure that the emissions 
are below the standard throughout useful life even as the emissions 
controls deteriorate. As discussed in this section and in Chapter 3 of 
the RIA and shown in Table III-12 and Table III-13, some manufactures 
have submitted certification data with zero emissions (with rounding), 
which results in a margin at 100 percent of the FEL, while other 
manufacturers have margin that is less than 25 percent of the FEL.
    To assess the feasibility of the final MY 2027 standards for Light, 
Medium, and Heavy HDE at the corresponding final useful lives, EPA took 
into consideration and evaluated the data from the EPA Stage 3 engine 
as well as other available data and comments received on the proposed 
standards. See section 3 of the Response to Comment document for 
further information on the comments received and EPA's detailed 
response.

[[Page 4341]]

    As discussed in Section III.B.2, the EPA Stage 3 engine includes 
improvements beyond the CARB Stage 3 engine, namely replacing the zone-
coated catalyzed soot filter with a separate DOC and DPF and improving 
the mixing of the DEF with exhaust for the downstream SCR catalyst. 
These improvements lowered the emissions on the SET, FTP, and LLC below 
what was measured with the CARB Stage 3 engine. The emissions for the 
EPA Stage 3 engine on the SET, FTP, and LLC aged to an equivalent of 
435,000, 600,000 and 800,000 miles are shown in Table III-7, Table III-
8, and Table III-9. To account for the IRAF for both particulate matter 
and sulfur on the aftertreatment system, we assessed and determined it 
was appropriate to rely on an analysis by SwRI that is summarized in 
Chapter 3 of the RIA. In this analysis SwRI determined that IRAF 
NOX emissions were at 2 mg/hp-hr for both the SET and FTP 
cycles and 5 mg/hp-hr for the LLC. To account for the crankcase 
emissions, we assessed and determined it was appropriate to rely on an 
analysis by SwRI that is summarized in Chapter 3 of the RIA. In this 
analysis, SwRI determined that the NOX emissions from the 
crankcase were at 6 mg/hp-hr for the LLC, FTP, and SET cycles.
    To determine whether or how to account for the effects of test 
procedure variability, emissions performance of other ratings in an 
engine family, production and engine variability, fuel and DEF quality, 
sulfur, soot and ash levels on the aftertreatment, aftertreatment aging 
due to severe-service operation, and aftertreatment packaging--and 
given the low level of the standards under consideration--EPA further 
assessed two potential approaches after taking into consideration 
comments received. The first approach considered was assigning standard 
deviation and offsets to each of these effects and then combining them 
using a mathematical method similar to what one commenter presented in 
their comments to the NPRM.\270\ The second approach considered was 
defining the margin as a percentage of the standards, similar to 
assertions by two commenters. We considered both of these approaches, 
the comments and supporting information submitted, historical 
approaches by EPA to compliance margin in previous heavy-duty criteria 
pollutant standards rules, and the data collected from the EPA Stage 3 
engine and other available data, to determine the numeric level of each 
standard over the corresponding useful life that is technically 
feasible.
---------------------------------------------------------------------------

    \270\ See RIA Chapter 3 for the details on this analysis.
---------------------------------------------------------------------------

    For the first approach, we determined that a minimum of 15 mg/hp-hr 
of margin between an emission standard and the NOX emissions 
of the EPA Stage 3 engine for each of the duty cycles was 
appropriate.\271\ For the second approach, we first assessed the 
average emissions rates from the EPA Stage 3 engine at the respective 
aged miles. For Light HDEs, we looked at the data at the equivalent of 
435,000 miles. For the Medium and Heavy HDEs standards the interpolated 
emissions performance at 650,000 miles was determined from the tests at 
the equivalent of 600,000 and 800,000 miles, which is shown in Table 
III-10.\272\ Second, the average emissions values were then adjusted to 
account for the IRAF and crankcase emissions from the EPA Stage 3 
engine. Third, we divided the adjusted emissions values by 0.55 to 
calculate an emission standard that would provide 45 percent margin to 
the standard. We determined it would be appropriate to apply a 45 
percent margin in this case after evaluating the margin in engines that 
meet the current standards as outlined in RIA chapter 3 and in CARB's 
comment to the NPRM and considering the level of the standards in this 
final rule. Our determination is based on our analysis that the 
certification data from engines meeting today's standards shows that 
more than 80 percent of engine families are certified with less than 45 
percent compliance margin. For Light HDEs, we took the resulting values 
from the third step of our approach and rounded them. EPA then also 
checked that each of these values for each of the duty cycles 
(resulting from the second approach) provided a minimum of 15 mg/hp-hr 
of margin between those values and the NOX emissions of the 
EPA Stage 3 engine (consistent with the first approach). For Light 
HDEs, we determined those resulting values were appropriate final 
numeric emission standards (as specified in Preamble Section III.B.2). 
The last step of checking that the Light HDE standards provide a 
minimum of 15 mg/hp-hr of NOX margin was to ensure that the 
margin determined from the percent of the standard (the second approach 
to margin) also provided the margin that we determined under the first 
approach to margin. For Light HDEs, given the level of the final 
standards and the length of the final useful life mileages, we 
determined that this approach to margin was appropriate for both 
certification and in-use testing of engines.
---------------------------------------------------------------------------

    \271\ See RIA Chapter 3 for the details on how the margin of 15 
mg/hp-hr was defined.
    \272\ See RIA Chapter 3.1.1.2 for additional information on why 
each aging test point was used for each primary intended service 
class. We note that we received data claimed as confidential 
business information from a manufacturer on August 2, 2022, and 
considered that data as part of this assessment to use the EPA Stage 
3 data at the equivalent of 650,000 miles for setting the Medium HDE 
standards. The data were added to the docket prior to the signing of 
the final rule. See also U.S. EPA. Stakeholder Meeting Log. 
December, 2022.
---------------------------------------------------------------------------

    Given the very long useful life mileages for Heavy HDE and greater 
amounts of certain aging mechanisms over the long useful life periods 
of Medium HDE, we determined that a different application of 
considering these two approaches to margin was appropriate. The in-use 
standards of Medium and Heavy HDEs were determined using the second 
approach for determining margin. The certification standards where then 
determined by subtracting the margin from the first approach (15 mg/hp-
hr) from the in-use standards.
    Separating the standards from the level that applies for in-use 
testing was appropriate because we recognize that laboratory aging of 
the engine doesn't fully capture all the sources of deterioration of 
the aftertreatment that can occur once the engine enters the real-world 
and those uncertainties would be most difficult for these engine 
classes at the level of the final standards and the final useful life 
mileages. Some of these effects are SCR sulfation, fuel quality, DEF 
quality, sensor variability, and field aging from severe duty cycles. 
Thus, the last step in determining the standards for Medium and Heavy 
HDE was to subtract the 15 mg/hp-hr from the rounded value that 
provided 45 percent margin to the Stage 3 data. We determined each of 
the resulting final duty cycle NOX standards for Medium and 
Heavy HDE that must be demonstrated at the time of certification out to 
350,000 and 750,000 miles, respectively, are feasible with enough 
margin to account for test procedure variability. We determined this by 
comparing the EPA Stage 3 emissions results at 800,000 miles (Table 
III-9) after adjusting for IRAF and crankcase emissions to each of the 
NOX standards in Section III.B.2. The EPA Stage 3 
NOX emissions results at 800,000 miles adjusted for IRAF and 
crankcase emissions are 26 mg/hp-hr for the SET, 33 mg/hp-hr for the 
FTP, and 33 mg/hp-hr for the LLC. For any in-use testing of Medium and 
Heavy HDEs, a 15 mg/hp-hr compliance allowance is added to the 
applicable standard, in consideration of the other sources of 
variability and deterioration of the aftertreatment that can occur once 
the engine enters the real world.

[[Page 4342]]

    As explained in the proposal, our technology cost analysis included 
an increased SCR catalyst volume from what was used on the EPA and CARB 
Stage 3 engines. By increasing the SCR catalyst volume, the 
NOX reduction performance of the aftertreatment system 
should deteriorate slower than what was demonstrated with the EPA Stage 
3 engine. The increase in total SCR catalyst volume relative to the EPA 
and CARB Stage 3 SCR was approximately 23.8 percent. We believe this 
further supports our conclusion that the final standards are achievable 
in MY 2027, including for the final useful life of 650,000 miles for 
Heavy HDEs. In addition to NOX, the final HC and CO 
standards are feasible for CI engines on all three cycles. This is 
shown in Table III-10, where the demonstrated HC and CO emission 
results are below the final standards discussed in Section III.B.2. The 
final standard for PM of 5 mg/hp-hr for the SET, FTP, and LLC continue 
to be feasible with the additional technology and control strategies 
needed to meet the final NOX standards, as seen by the PM 
emissions results in Table III-10. As discussed in Section III.B.2, 
taking into account measurement variability of the PM measurement test 
procedure, we believe PM emissions from current diesel engines are at 
the lowest feasible level for standards starting in MY 2027.

             Table III-7--Stage 3 Engine Emissions at 435,000 Mile Equivalent Test Point Without Adjustments for IRAF or Crankcase Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                            NOX (mg/hp-hr)                        NMHC (nonmethane                         CO2 (g/hp-hr)   N2O (g/hp-hr)
                Duty cycle                                   PM (mg/hp-hr)     hydrocarbon) (mg/hp-hr)     CO (g/hp-hr)
--------------------------------------------------------------------------------------------------------------------------------------------------------
SET \a\...................................              17               1                             1           0.030             455           0.024
FTP.......................................              20               2                            12           0.141             514           0.076
LLC.......................................              29               3                            35           0.245             617           0.132
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Using the weighting factors in our finalized test procedures (40 CFR 1036.510).

   Table III-8--Stage 3 Engine Emissions at 600,000 Mile Equivalent Test Point Without Adjustments for IRAF or
                                               Crankcase Emissions
----------------------------------------------------------------------------------------------------------------
                                                 NOX (mg/
                  Duty cycle                      hp-hr)   PM (mg/hp- NMHC (mg/  CO (g/hp-  CO2 (g/hp- N2O (g/hp-
                                                              hr)       hp-hr)      hr)        hr)        hr)
----------------------------------------------------------------------------------------------------------------
SET \a\.......................................         24          1          1      0.015        460      0.030
FTP...........................................         27          1          9      0.144        519      0.058
LLC...........................................         33          4         16      0.153        623      0.064
----------------------------------------------------------------------------------------------------------------
\a\ Using the weighting factors in our finalized test procedures (40 CFR 1036.510).

   Table III-9--Stage 3 Engine Emissions at 800,000 Mile Equivalent Test Point Without Adjustments for IRAF or
                                               Crankcase Emissions
----------------------------------------------------------------------------------------------------------------
                                                 NOX (mg/
                  Duty cycle                      hp-hr)   PM (mg/hp- NMHC (mg/  CO (g/hp-  CO2 (g/hp- N2O (g/hp-
                                                              hr)       hp-hr)      hr)        hr)        hr)
----------------------------------------------------------------------------------------------------------------
SET \a\.......................................         30          2          1      0.023        458      0.028
FTP...........................................         37          1         14      0.149        520      0.092
LLC...........................................         34          1         40      0.205        629      0.125
----------------------------------------------------------------------------------------------------------------
\a\ Using the weighting factors in our finalized test procedures (40 CFR 1036.510).

 Table III-10--Stage 3 Engine Emissions at Interpolated at 650,000 Mile Equivalent Without Adjustments for IRAF
                                             or Crankcase Emissions
----------------------------------------------------------------------------------------------------------------
                                                 NOX (mg/
                  Duty cycle                      hp-hr)   PM (mg/hp- NMHC (mg/  CO (g/hp-  CO2 (g/hp- N2O (g/hp-
                                                              hr)       hp-hr)      hr)        hr)        hr)
----------------------------------------------------------------------------------------------------------------
SET \a\.......................................         26          1          1      0.017        460      0.030
FTP...........................................         30          1         10      0.145        519      0.067
LLC...........................................         33          3         22      0.166        625      0.079
----------------------------------------------------------------------------------------------------------------
\a\ Using the weighting factors in our finalized test procedures (40 CFR 1036.510).

    In addition to evaluating the feasibility of the new criteria 
pollutant standards, we also evaluated how CO2 was impacted 
on the CARB Stage 3 engine (which is the same engine that was used for 
EPA's Stage 3 engine with modifications to the aftertreatment system 
and engine calibration to lower NOX emissions). We did this 
by evaluating how CO2 emissions changed from the base engine 
over the SET, FTP, and LLC, as well as the fuel mapping test procedures 
defined in 40 CFR 1036.535 and 1036.540. For all three cycles the CARB 
Stage 3 engine emitted CO2 with no measurable difference 
compared to the base 2017 Cummins X15 engine. Specifically, we compared 
the CARB Stage 3 engine including the 0-hour (degreened) aftertreatment 
with the 2017 Cummins X15 engine including degreened aftertreatment and 
found the percent reduction in CO2 was

[[Page 4343]]

0 percent for the SET, 1 percent for the FTP, and 1 percent for the 
LLC.\273\
---------------------------------------------------------------------------

    \273\ See Chapter 3 of the RIA for the CO2 emissions 
of the 2017 Cummins X15 engine and the CARB Stage 3 engine.
---------------------------------------------------------------------------

    We note that while the data from the EPA Stage 3 engine (the same 
engine as the CARB Stage 3 engine but after SwRI made changes to the 
thermal management strategies) at the equivalent age of 435,000 miles 
showed an increase in CO2 emissions for the SET, FTP, and 
LLC of 0.6, 0.7 and 1.3 percent respectively, which resulted in the 
CO2 emissions for the EPA Stage 3 engine being higher than 
the 2017 Cummins X15 engine, this is not directly comparable because 
the baseline 2017 Cummins X15 aftertreatment had not been aged to an 
equivalent of 435,000 miles.\274\ As discussed in Chapter 3 of the RIA, 
aging the EPA Stage 3 engine included exposing the aftertreatment to 
ash, that increased the back pressure on the engine, which contributed 
to the increase in CO2 emissions from the EPA Stage 3 
engine. We would expect the same increase in backpressure and in 
CO2 emissions from the 2017 Cummins X15 engine if the 
aftertreatment of the 2017 Cummins X15 engine was aged to an equivalent 
of 435,000 miles.
---------------------------------------------------------------------------

    \274\ As part of the agency's diesel demonstration program, we 
didn't age the aftertreatment of the base 2017 Cummins X15 engine 
since the focus of this program was to demonstrate emissions 
performance of future technologies and due to resource constraints. 
Thus, there isn't data directly comparable to the baseline engine at 
each aging step.
---------------------------------------------------------------------------

    To evaluate how the technology on the CARB Stage 3 engine compares 
to the 2017 Cummins X15 engine with respect to the HD GHG Phase 2 
vehicle CO2 standards, both engines were tested on the fuel 
mapping test procedures defined in 40 CFR 1036.535 and 1036.540. These 
test procedures define how to collect the fuel consumption data from 
the engine for use in GEM. For these tests the CARB Stage 3 engine was 
tested with the development aged aftertreatment.\275\ The fuel maps 
from these tests were run in GEM and the results from this analysis 
showed that the EPA and CARB Stage 3 engine emitted CO2 at 
the same rate as the 2017 Cummins X15 engine. The details of this 
analysis are described in Chapter 3.1 of the RIA.
---------------------------------------------------------------------------

    \275\ The CARB Stage 3 0-hour (degreened) aftertreatment could 
not be used for these tests, because it had already been aged past 
the 0-hour point when these tests were conducted.
---------------------------------------------------------------------------

    The technologies included in the EPA Stage 3 engine were selected 
to both demonstrate the lowest criteria pollutant emissions and have a 
negligible effect on GHG emissions. Manufactures may choose to use 
other technologies to meet the final standards, but manufacturers will 
still also need to comply with the GHG standards that apply under HD 
GHG Phase 2. We have, therefore, not projected an increase in GHG 
emissions resulting from compliance with the final standards.
---------------------------------------------------------------------------

    \276\ See RIA Chapter 3 for the details of the cost for the 
aftertreatment and CDA, which are the drivers for why the 
incremental direct manufacturing cost is lowest for Medium HDE.
    \277\ See Table III-3 for the final useful life values and 
Section IV.B.1 for the final emissions warranty periods.
---------------------------------------------------------------------------

    Table III-11 summarizes the incremental direct manufacturing costs 
for the final standards, from the baseline costs shown in Table III-15. 
These values include aftertreatment system, closed crankcase, and CDA 
costs. As discussed in Chapter 7 of the RIA, the direct manufacturing 
costs include the technology costs plus some costs to improve the 
durability of the technology through regulatory useful life. The 
details of this analysis can be found in Chapters 3 and 7 of the 
RIA.\276\ The cost of the final standards and useful life periods are 
further accounted for in the indirect costs as discussed in Chapter 7 
of the RIA.\277\

 Table III-11--Incremental Direct Manufacturing Cost of Final Standards
      for the Aftertreatment, Closed Crankcase, and CDA Technology
                                [2017 $]
------------------------------------------------------------------------
                                           Medium
               Light HDE                    HDE     Heavy HDE  Urban bus
------------------------------------------------------------------------
$1,957.................................     $1,817     $2,316     $1,850
------------------------------------------------------------------------

b. Baseline Emissions and Cost
    The basis for our baseline technology assessment is the data 
provided by manufacturers in the heavy-duty in-use testing program. 
This data encompasses in-use operation from nearly 300 Light HDE, 
Medium HDE, and Heavy HDE vehicles. Chapter 5 of the RIA describes how 
the data was used to update the MOVES model emissions rates for HD 
diesel engines. Chapter 3 of the RIA summarizes the in-use emissions 
performance of these engines.
    We also evaluated the certification data submitted to the agency. 
The data includes test results adjusted for IRAF and FEL that includes 
adjustments for deterioration and margin. The certification data, 
summarized in Table III-12 and Table III-13, shows that manufacturers 
vary in their approach to how much margin is built into the FEL. Some 
manufactures have submitted certification data with zero emissions 
(with rounding), which results in a margin at 100 percent of the FEL, 
while other manufacturers have margin that is less than 25 percent of 
the FEL.

                            Table III-12--Summary of Certification Data for FTP Cycle
----------------------------------------------------------------------------------------------------------------
                                                           NOX (g/hp- PM (g/hp-   NMHC (g/  CO (g/hp-  N2O (g/hp-
                                                              hr)        hr)       hp-hr)      hr)        hr)
----------------------------------------------------------------------------------------------------------------
Average..................................................       0.13       0.00       0.01       0.18       0.07
Minimum..................................................       0.05       0.00       0.00       0.00       0.04
Maximum..................................................       0.18       0.00       0.04       1.10       0.11
----------------------------------------------------------------------------------------------------------------

                            Table III-13--Summary of Certification Data for SET Cycle
----------------------------------------------------------------------------------------------------------------
                                                           NOX (g/hp- PM (g/hp-   NMHC (g/  CO (g/hp-  N2O (g/hp-
                                                              hr)        hr)       hp-hr)      hr)        hr)
----------------------------------------------------------------------------------------------------------------
Average..................................................       0.11       0.00       0.01       0.00       0.06
Minimum..................................................       0.00       0.00       0.00       0.00       0.00
Maximum..................................................       0.18       0.00       0.04       0.20       0.11
----------------------------------------------------------------------------------------------------------------

[[Page 4344]]

    In addition to analyzing the on-cycle certification data submitted 
by manufacturers, we tested three modern HD diesel engines on an engine 
dynamometer and analyzed the data. These engines were a 2018 Cummins 
B6.7, 2018 Detroit DD15 and 2018 Navistar A26. These engines were 
tested on cycles that range in power demand from the creep mode of the 
Heavy Heavy-Duty Diesel Truck (HHDDT) schedule to the HD SET cycle 
defined in 40 CFR 1036.510. Table III-14 summarizes the range of 
results from these engines on the SET, FTP, and LLC. As described in 
Chapter 3 of the RIA, the emissions of current production heavy-duty 
engines vary from engine to engine but the largest difference in NOX 
between engines is seen on the LLC.

                   Table III-14--Range of NOX Emissions From MY2018 Heavy-Duty Diesel Engines
----------------------------------------------------------------------------------------------------------------
                                                   SET in 40 CFR   SET in 40 CFR
                  NOX (g/hp-hr)                       86.1333        1036.510      FTP composite        LLC
----------------------------------------------------------------------------------------------------------------
Minimum.........................................            0.01            0.01            0.10            0.35
Maximum.........................................            0.12            0.05            0.15            0.81
Average.........................................            0.06            0.03            0.13            0.59
----------------------------------------------------------------------------------------------------------------

    Table III-15 summarizes the baseline sales-weighted total 
aftertreatment cost of Light HDEs, Medium HDEs, Heavy HDEs and urban 
bus engines. The details of this analysis can be found in Chapters 3 
and 7 of the RIA.

                         Table III-15--Baseline Direct Manufacturing Aftertreatment Cost
                                                    [2017 $]
----------------------------------------------------------------------------------------------------------------
                          Light HDE                               Medium HDE       Heavy HDE        Urban bus
----------------------------------------------------------------------------------------------------------------
$2,585.......................................................          $2,536           $3,761           $2,613
----------------------------------------------------------------------------------------------------------------

C. Summary of Compression-Ignition Off-Cycle Standards and Off-Cycle 
Test Procedures

    In this Section 0, we describe the final off-cycle standards and 
test procedures that will apply for model year 2027 and later heavy-
duty compression-ignition engines. The final off-cycle standards and 
test procedures cover the range of operation included in the duty cycle 
test procedures and operation that is outside of the duty cycle test 
procedures for each regulated pollutant (NOX, HC, CO, and 
PM). As described in Section III.C.1, our current not-to-exceed (NTE) 
test procedures were not designed to capture and control low-load 
operation. In contrast to the current NTE approach that evaluates 
engine operation within the NTE zone and excludes operation out of the 
NTE zone, we are finalizing a moving average window (MAW) approach that 
divides engine operation into two categories (or ``bins'') based on the 
time-weighted average engine power of each MAW of engine data. See 
Section III.C.2 for a discussion of the derivation of the final off-
cycle standards for each bin. For bin 1, the NOX emission 
standard is 10.0 g/hr. The final off-cycle standards for bin 2 are 
shown in Table III-16.

             Table III-16--Final Off-Cycle Bin 2 Standards for Light HDE, Medium HDE, and Heavy HDE
----------------------------------------------------------------------------------------------------------------
                        NOX (mg/hp-hr)                          HC (mg/hp-hr)    PM (mg/hp-hr)     CO (g/hp-hr)
----------------------------------------------------------------------------------------------------------------
58 \a\.......................................................             120              7.5                9
----------------------------------------------------------------------------------------------------------------
\a\ An interim NOX compliance allowance of 15 mg/hp-hr applies for any in-use testing of Medium HDE and Heavy
  HDE. Manufacturers will add the compliance allowance to the NOX standard that applies for each duty cycle and
  for off-cycle testing, with both field testing and laboratory testing.

    The proposed rule provided an extensive discussion of the rationale 
and information supporting the proposed off-cycle standards (87 FR 
17472, March 28, 2022). Chapters 2 and 3 of the RIA include additional 
information including background on applicable test procedures and the 
full feasibility analysis for compression-ignition engines. See also 
section 11.3 of the Response to Comments for a detailed discussion of 
the comments and how they have informed this final rule.

1. Existing NTE Standards and Need for Changes to Off-Cycle Test 
Procedures

    Heavy-duty CI engines are currently subject to Not-To-Exceed (NTE) 
standards that are not limited to specific test cycles, which means 
they can be evaluated not only in the laboratory but also in-use. NTE 
standards and test procedures are generally referred to as ``off-
cycle'' standards and test procedures. These off-cycle emission 
standards are 1.5 (1.25 for CO) times the laboratory certification 
standard for NOX, HC, PM and CO and can be found in 40 CFR 
86.007-11.\278\ NTE standards have been successful in broadening the 
types of operation for which manufacturers design their emission 
controls to remain effective, including steady cruise operation. 
However, there remains a significant proportion of vehicle operation 
not covered by NTE standards.
---------------------------------------------------------------------------

    \278\ As noted in Section IV.G, manufacturers choosing to 
participate in the existing or final averaging, banking, and trading 
program agree to meet the family emissions limit (FEL) declared 
whenever the engine is tested over the applicable duty- or off-cycle 
test procedure. The FELs serves as the emission standard for 
compliance testing instead of the standards specified in 40 CFR 
86.007-11 or 40 CFR 1036.104(a); thus, the existing off-cycle 
standards are 1.5 (1.25 for CO) times the FEL for manufacturers who 
choose to participate in ABT.

---------------------------------------------------------------------------

[[Page 4345]]

    Compliance with an NTE standard is based on emission test data 
(whether collected in a laboratory or in use) analyzed pursuant to 40 
CFR 86.1370 to identify NTE events, which are intervals of at least 30 
seconds when engine speeds and loads remain in the NTE control area or 
``NTE zone''. The NTE zone excludes engine operation that falls below 
certain torque, power, and speed values.\279\ The NTE procedure also 
excludes engine operation that occurs in certain ambient conditions 
(i.e., high altitudes, high intake manifold humidity), or when 
aftertreatment temperatures are below 250 [deg]C. Collected data is 
considered a valid NTE event if it occurs within the NTE zone, lasts at 
least 30 seconds, and does not occur during any of the exclusion 
conditions (ambient conditions or aftertreatment temperature).
---------------------------------------------------------------------------

    \279\ Specifically, engine operations are excluded if they fall 
below 30 percent of maximum torque, 30 percent of maximum power, or 
15 percent of the European Stationary Cycle speed.
---------------------------------------------------------------------------

    The purpose of the NTE test procedure is to measure emissions 
during engine operation conditions that could reasonably be expected to 
occur during normal vehicle use; however, only data in a valid NTE 
event is then compared to the NTE emission standard. Our analysis of 
existing heavy-duty in-use vehicle test data indicates that less than 
ten percent of a typical time-based dataset are part of valid NTE 
events, and hence subject to the NTE standards; the remaining test data 
are excluded from consideration. We also found that emissions are high 
during many of the excluded periods of operation, such as when the 
aftertreatment temperature drops below the 250 [deg]C exclusion 
criterion. Our review of in-use data indicates that extended time at 
low load and idle operation results in low aftertreatment temperatures, 
which in turn lead to diesel engine SCR-based emission control systems 
not functioning over a significant fraction of real-world 
operation.\280\ \281\ \282\ Test data collected as part of EPA's 
manufacturer-run in-use testing program indicate that low-load 
operation could account for greater than 50 percent of the 
NOX emissions from a vehicle over a given workday.\283\
---------------------------------------------------------------------------

    \280\ Hamady, Fakhri, Duncan, Alan. ``A Comprehensive Study of 
Manufacturers In-Use Testing Data Collected from Heavy-Duty Diesel 
Engines Using Portable Emissions Measurement System (PEMS)''. 29th 
CRC Real World Emissions Workshop, March 10-13, 2019.
    \281\ Sandhu, Gurdas, et al. ``Identifying Areas of High 
NOX Operation in Heavy-Duty Vehicles''. 28th CRC Real-
World Emissions Workshop, March 18-21, 2018.
    \282\ Sandhu, Gurdas, et al. ``In-Use Emission Rates for MY 
2010+ Heavy-Duty Diesel Vehicles''. 27th CRC Real-World Emissions 
Workshop, March 26-29, 2017.
    \283\ Sandhu, Gurdas, et al. ``Identifying Areas of High 
NOX Operation in Heavy-Duty Vehicles''. 28th CRC Real-
World Emissions Workshop, March 18-21, 2018.
---------------------------------------------------------------------------

    For example, 96 percent of tests in response to 2014, 2015, and 
2016 EPA in-use testing orders passed with NOX emissions for 
valid NTE events well below the 0.3 g/hp-hr NOX NTE 
standard. When we used the same data to calculate NOX 
emissions over all operation measured, not limited to valid NTE events, 
the NOX emissions were more than double those within the 
valid NTE events (0.5 g/hp-hr).\284\ The results were even higher when 
we analyzed the data to consider only NOX emissions that 
occur during low load events.
---------------------------------------------------------------------------

    \284\ Hamady, Fakhri, Duncan, Alan. ``A Comprehensive Study of 
Manufacturers In-Use Testing Data Collected from Heavy-Duty Diesel 
Engines Using Portable Emissions Measurement System (PEMS)''. 29th 
CRC Real World Emissions Workshop, March 10-13, 2019.
---------------------------------------------------------------------------

    EPA and others have compared the performance of US-certified 
engines and those certified to European Union emission standards and 
concluded that the European engines' NOX emissions are lower 
in low-load conditions, but comparable to US-certified engines subject 
to MY 2010 standards under city and highway operation.\285\ This 
suggests that manufacturers are responding to the European 
certification standards by designing their emission controls to perform 
well under low-load operations, as well as highway operations.
---------------------------------------------------------------------------

    \285\ Rodriguez, F.; Posada, F. ``Future Heavy-Duty Emission 
Standards An Opportunity for International Harmonization''. The 
International Council on Clean Transportation. November 2019. 
Available online: https://theicct.org/sites/default/files/publications/Future%20_HDV_standards_opportunity_20191125.pdf.
---------------------------------------------------------------------------

    The European Union ``Euro VI'' emission standards for heavy-duty 
engines require manufacturers to check for ``in-service conformity'' by 
operating their engines over a mix of urban, rural, and motorway 
driving on prescribed routes using portable emission measurement system 
(PEMS) equipment to measure emissions.\286\ \287\ Compliance is 
determined using a work-based windows approach where emissions data are 
evaluated over segments or ``windows.'' A window consists of 
consecutive 1 Hz data points that are summed until the engine performs 
an amount of work equivalent to the European transient engine test 
cycle (World Harmonized Transient Cycle).
---------------------------------------------------------------------------

    \286\ COMMISSION REGULATION (EU) No 582/2011, May 25, 2011. 
Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:02011R0582-20180118&from=EN.
    \287\ COMMISSION REGULATION (EU) 2018/932, June 29, 2018. 
Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32018R0932&from=EN.
---------------------------------------------------------------------------

    EPA is finalizing new off-cycle test procedures similar to the 
European Euro VI in-service conformity program, with key distinctions 
that build upon the Euro VI approach, as discussed in the following 
section. This new approach will require manufacturers to account for a 
relatively larger proportion of engine operation and thereby further 
ensure that real-world emissions meet the off-cycle standards.
2. Off-Cycle Standards and Test Procedures
    We are replacing the NTE test procedures and standards (for 
NOX, PM, HC and CO) for model year 2027 and later engines. 
Under the final new off-cycle standards and test procedures, engine 
operation and emissions test data must be assessed in test intervals 
that consist of 300-second moving average windows (MAWs) of continuous 
engine operation. Our evaluation accounts for our current understanding 
that shorter windows are more sensitive to measurement variability and 
longer windows make it difficult to distinguish between duty cycles. In 
contrast to the current NTE approach that divides engine operation into 
two categories (in the NTE zone and out of the NTE zone), this approach 
will divide engine operation into two categories (or ``bins'') based on 
the time-weighted average engine power of each MAW of engine data, with 
some limited exclusions from the two bins, as described in more detail 
in the following discussion.
    In the NPRM, we requested comment on the proposed off-cycle 
standards and test procedures, including the 300 second length of the 
window. We first note that commenters broadly agree that the current 
NTE methodology should be revised, and that a MAW structure is 
preferable for off-cycle standards. Some commenters were concerned that 
individual seconds of data would be ``smeared,'' with the same 1-Hz 
data appearing in both bins as the 300 second windows are placed in the 
appropriate bin. We are finalizing the window length that we proposed, 
as the 300 second length provides an adequate averaging time to smooth 
any anomalous emission events and we anticipate that the final bin 
structure described in Section III.C.2.i. should also help address 
these concerns. See Response to Comments Section 11.1 through 11.3 for 
further details on these comments and EPA's response to these comments.
    Although this program has similarities to the European Euro VI 
approach, we are not limiting our off-

[[Page 4346]]

cycle standards and test procedures to operation on prescribed routes. 
Our current NTE program is not limited to prescribed routes, and we 
would consider it an unnecessary step backward to change that aspect of 
the procedure.
    In Section IV.G, we discuss the final rule updates to the ABT 
program to account for these new off-cycle standards.
i. Moving Average Window Operation Bins
    The final bin structure includes two bins of operation that 
represent two different domains of emission performance. Bin 1 
represents extended idle operation and other very low load operation 
where engine exhaust temperatures may drop below the optimal 
temperature for aftertreatment function. Bin 2 represents higher power 
operation including much of the operation currently covered by the NTE. 
Operation in bin 2 naturally involves higher exhaust temperatures and 
catalyst efficiencies. Because this approach divides 300 second windows 
into bins based on time-averaged engine power of the window, any of the 
bins could include some idle or high-power operation. Like the duty 
cycle standards, we believe more than a single standard is needed to 
apply to the entire range of operation that heavy-duty engines 
experience. A numerical standard that is technologically feasible under 
worst case conditions such as idle would necessarily be much higher 
than the levels that are achievable when the aftertreatment is 
functioning optimally. Section III.C.2.iii includes the final numeric 
off-cycle standards.
    Given the challenges of measuring engine power directly in-use, we 
are using the CO2 emission rate (grams per second) as a 
surrogate for engine power in defining the bins for an engine. We are 
further normalizing CO2 emission rates relative to the 
nominal maximum CO2 rate of the engine. So, if an engine 
with a maximum CO2 emission rate of 50 g/sec was found to be 
emitting CO2 at a rate of 10 g/sec, its normalized 
CO2 emission rate would be 20 percent. The maximum 
CO2 rate is defined as the engine's rated maximum power 
multiplied by the engine's CO2 family certification level 
(FCL) for the FTP certification cycle.
    In the proposal, we requested comment on whether the maximum 
CO2 mass emission rate should instead be determined from the 
steady-state fuel mapping procedure in 40 CFR 1036.535 or the torque 
mapping procedure defined in 40 CFR 1065.510. After considering 
comments, EPA is finalizing the use of the CO2 emission rate 
as a surrogate for engine power with the proposed approach to 
determining the maximum CO2 mass emission rate. We have two 
main reasons for finalizing the determination of maximum CO2 
mass emission rate as proposed. First, the FTP FCL and maximum engine 
power are already reported to the EPA, so no new requirements are 
needed under the finalized approach. Second, our assessment of the 
finalized approach has shown that this approach for the determination 
of maximum CO2 mass emission rate matches well with the 
other options we requested comment on. EPA believes that using the 
CO2 emission rate will automatically account for additional 
fuel usage not directly used for driveshaft torque and minimizes 
concerns about the accuracy and data alignment in the use of broadcast 
torque. EPA acknowledges that there is some small variation in 
efficiency, and thus CO2 emissions rates, among engines. 
However, the test procedure accounts for improvements to the engine 
efficiency by using the FTP FCL to convert CO2 specific 
NOX to work specific NOX. This is because the FTP 
FCL captures the efficiency of the engine over a wide range of 
operation, from cold start, idle and steady-state higher power 
operation. Furthermore, the FTP FCL can also capture the CO2 
improvements from hybrid technology when the powertrain test option 
described in preamble Section III.B.2.v is utilized.
    The bins are defined as follows:
     Bin 1: 300 second windows with normalized average 
CO2 rate <=6 percent.
     Bin 2: 300 second windows with normalized average 
CO2 rate >6 percent.
    The bin cut point of six percent is near the average power of the 
low-load cycle. In the NPRM, we proposed a three-bin structure and 
requested comment on the proposed number of bins and the value of the 
cut point(s). After considering comments, EPA agrees with commenters to 
the extent the commenters recommend combining the proposed bins 2 and 3 
into a single ``non-idle'' bin 2. Results from the EPA Stage 3 real 
world testing indicate that emissions in bins 2 and 3 (expressed as 
emissions/normalized CO2) are substantially similar, 
minimizing the advantage of separating these modes of operation. See 
Response to Comments Section 11.1 for further details on these comments 
and EPA's response to these comments.
    To ensure that there is adequate data in each of the bins to 
compare to the off-cycle standards, the final requirements specify that 
there must be a minimum of 2,400 moving average windows in bin 1 and 
10,000 moving average windows in bin 2. In the NPRM, we proposed a 
minimum of 2,400 windows for all bins and requested comment on the 
appropriate minimum number of windows required to sufficiently reduce 
variability in the results while not requiring an unnecessary number of 
shift days to be tested to meet the requirement. EPA received comments 
both supporting the proposed 2,400 window minimum and supporting an 
increase to 10,000 windows total for the non-idle bins (now a single 
bin 2 in this final rule). After considering comments, we believe 
requiring a minimum of 10,000 windows in final bin 2 to define a valid 
test is appropriate. Analysis of data from the EPA Stage 3 off-cycle 
test data has shown that emissions are stable after 6,000 windows of 
data at moderate temperatures but NOX emissions under low 
ambient temperatures need closer to 10,000 windows to be stable. EPA 
believes the larger number of required windows will better characterize 
the emissions performance of the engine.
    If during the first shift day any of the bins do not include at 
least the minimum number of windows, then the engine will need to be 
tested for additional day(s) until the minimum requirement is met. 
Additionally, the engine can be idled at the end of the shift day to 
meet the minimum window count requirement for the idle bin. This is to 
ensure that even for duty cycles that do not include significant idle 
operation the minimum window count requirement for the idle bin can be 
met without testing additional days.
    We received comments on the timing and duration of the optional 
end-of-day idle. After considering comments, the final requirements 
specify that the ability to add idle time is restricted to the end of 
the shift day, and manufacturers may extend this end-of-day idle period 
to be as long as they choose. Additional idle in the middle of the 
shift day is contrary to the intent of real-world testing, and the end 
of the shift day is the only realistic time to add windows. Since idle 
times of varying lengths are encountered in real-world operation, we do 
not think that requiring a specific length of idle time would 
necessarily make the resulting data set more representative.
    As described further in section III.C.2.ii, after consideration of 
comment, EPA is including requirements in 40 CFR 1036.420 that specify 
that during the end-of-day idle period, when testing vehicles with 
automated engine shutdown features, manufacturers will be required to 
override the automated shutdown feature where possible. This will 
ensure

[[Page 4347]]

that the test data will contain at least 2,400 windows in the idle bin, 
which otherwise would be unobtainable. For automated shutdown features 
that cannot be overridden, the manufacturer may populate the bin with 
zero emission values for idle until exactly 2,400 windows are achieved.
ii. Off-Cycle Test Procedures
    The final off-cycle test procedures include measuring off-cycle 
emissions using the existing test procedures that specify measurement 
equipment and the process of measuring emissions during testing in 40 
CFR part 1065. Part 1036, subpart E contains the process for recruiting 
test vehicles, how to test over the shift day, how to evaluate the 
data, what constitutes a valid test, and how to determine if an engine 
family passes. Measurements may use either the general laboratory test 
procedures or the field-testing procedures in 40 CFR part 1065, subpart 
J. However, we are finalizing special calculations for bin 2 in 40 CFR 
1036.530 that will supersede the brake-specific emission calculations 
in 40 CFR part 1065. The test procedures require second-by-second 
measurement of the following parameters:

 Molar concentration of CO2 (ppm)
 Molar concentration of NOX (ppm)
 Molar concentration of HC (ppm)
 Molar concentration of CO (ppm)
 Concentration of PM (g/m\3\)
 Exhaust flow rate (m\3\/s)

    Mass emissions of CO2 and each regulated pollutant are 
separately determined for each 300-second window and are binned based 
on the normalized CO2 rate for each window.
    Additionally, EPA agrees with commenters that the maximum allowable 
engine coolant temperature at the start of the day should be raised to 
40 degrees Celsius and we are finalizing this change in 40 CFR 
1036.530. In the NPRM, we proposed 30 [deg]C which is 86 [deg]F. It is 
possible that ambient temperatures in some regions of the United States 
won't drop below this overnight. We are therefore finalizing 40 [deg]C 
which is 104 [deg]F as this should ensure that high overnight ambient 
temperatures do not prevent a manufacturer from testing a vehicle.
    The standards described in Section III.C.2.iii are expressed in 
units of g/hr for bin 1 and mg/hp-hr for bin 2. However, unlike most of 
our exhaust standards, the hp-hr values for the off-cycle standards do 
not refer to actual brake work. Rather, they refer to nominal 
equivalent work calculated proportional to the CO2 emission 
rate. Thus, in 40 CFR 1036.530 the NOX emissions (``e'') in 
g/hp-hr are calculated as:
[GRAPHIC] [TIFF OMITTED] TR24JA23.000

    The final requirements include a limited number of exclusions (six 
total) in 40 CFR 1036.530(c)(3) that exclude some data from being 
subject to the off-cycle standards. The first exclusion in 40 CFR 
1036.530(c)(3)(i) is for data collected during periodic PEMS zero and 
span drift checks or calibrations, where the emission analyzers and/or 
flow meter are not available to measure emissions during that time and 
these checks/calibrations are needed to ensure the robustness of the 
data.
    The second exclusion in 40 CFR 1036.530(c)(3)(ii) is for data 
collected anytime the engine is off during the course of the shift day, 
with modifications from proposal that (1) this exclusion does not 
include engine off due to automated stop-start, and (2) specific 
requirements for vehicles with stop-start technology. In the NPRM, we 
proposed excluding data for vehicles with stop-start technology when 
the engine was off and requested comment on the appropriateness of this 
exclusion. We received comment suggesting provisions for vehicles 
equipped with automated stop-start technology. After considering 
comments, EPA has included in the final rule requirements applicable 
when testing vehicles with automatic engine shutdown (AES) and/or stop-
start technology. Under the final requirements, the manufacturer shall 
disable AES and/or stop-start if it is not tamper resistant as 
described in 40 CFR 1036.415(g), 1036.420(c), and 1036.530(c)(3). If 
stop-start is tamper resistant, the 1-Hz emission rate for all GHG and 
criteria pollutants shall be set to zero when AES and/or stop-start is 
active and the engine is off, and these data are included in the normal 
windowing process (i.e., the engine-off data are not treated as 
exclusions). If at the end of the shift day there are not 2,400 windows 
in bin 1 for a vehicle with AES and/or stop-start technology, the 
manufacturer must populate the bin with additional windows with the 
emission rate for each GHG and criteria pollutant set to zero to 
achieve exactly 2,400 idle bin windows. This process accounts for 
manufacturers who implement a start/stop mode that cannot be overridden 
and applies the windowing and binning process in a way that is similar 
to the process applied to a conventionally idling vehicle.
    The third exclusion in 40 CFR 1036.530(c)(3)(iii) is for data 
collected during infrequent regeneration events. The data collected for 
the test order may not collect enough operation to properly weight the 
emissions rates during an infrequent regeneration event with emissions 
that occur without an infrequent regeneration event.
    The fourth exclusion in 40 CFR 1036.530(c)(3)(iv) is for data 
collected when ambient temperatures are below 5 [deg]C (this aspect 
includes some modifications from proposal), or when ambient 
temperatures are above the altitude-based value determined using 
Equation 40 CFR 1036.530-1. The colder temperatures can significantly 
inhibit the engine's ability to maintain aftertreatment temperature 
above the minimum operating temperature of the SCR catalyst while the 
higher temperature conditions at altitude can limit the mass airflow 
through the engine, which can adversely affect the engine's ability to 
reduce engine out NOX through the use of exhaust gas 
recirculation (EGR). In addition to affecting EGR, the air-fuel ratio 
of the engine can decrease under high load, which can increase exhaust 
temperatures above the conditions where the SCR catalyst is most 
efficient at reducing NOX. However, we also do not want to 
select temperature limits that overly exclude operation, such as 
setting a cold temperature limit so high that it excludes important 
initial cold start operation from all tests, or a number of return to 
service events. These are important operational regimes, and the MAW 
protocol is intended to capture emissions over the entire operation of 
the vehicle. The final rule strikes an appropriate balance between 
these considerations.
    In the NPRM, we proposed excluding data when ambient temperatures 
were below -7 [deg]C and requested comment on the appropriateness of 
this exclusion. Several comments disagreed with the proposed low 
temperature exclusion level and recommended a higher

[[Page 4348]]

temperature of 20 [deg]C as well as additional exemptions for coolant 
and oil temperatures, and recommended low temperature exclusion 
temperatures that ranged from 20 to 70 [deg]C. After considering 
comments, we adjusted the final ambient temperature exclusion to 5 
[deg]C. We have additionally incorporated a temperature-based 
adjustment to the final numerical NOX standards, as 
described in Section III.C.iii. However, we have not incorporated 
exclusions based on coolant and oil temperatures. These changes are 
supported by data recently generated from testing at SwRI with the EPA 
Stage 3 engine at low temperatures over the CARB Southern Route Cycle 
and Low Load Cycle. This testing consisted of operation of the engine 
over the duty-cycle with the test cell ambient temperature set at 5 
[deg]C with air flow moving over the aftertreatment system to simulate 
the airflow over the aftertreatment during over the road operation. The 
results indicated that there were cold ambient air temperature effects 
on aftertreatment temperature that reduced NOX reduction 
efficiency, which supports that the temperature should be increased. 
With these changes, our analysis, as described in section III.C, shows 
that the off-cycle standards are achievable for MY 2027 and later 
engines down to 5 [deg]C, taking into account the temperature-based 
adjustment to the final numerical standards. We have concerns about 
whether the off-cycle standards could be met below 5 [deg]C after 
taking a closer look at all data regarding real world effects and based 
on this we are exempting data from operation below 5 [deg]C from being 
subject to the standards.
    The fifth exclusion in 40 CFR 1036.530(c)(3)(v) is for data 
collected where the altitude is greater than 5,500 feet above sea level 
for the same reasons as for the high temperatures at altitude 
exclusion.
    The sixth exclusion in 40 CFR 1036.530(c)(3)(vi) is for data 
collected when any approved Auxiliary Emission Control Device (AECD) 
for emergency vehicles are active because the engines are allowed to 
exceed the emission standards while these AECDs are active.
    To reduce the influence of environmental conditions on the accuracy 
and precision of the PEMS for off-cycle in-use testing, we are adding 
additional changes to those proposed in requirements in 40 CFR 
1065.910(b). These requirements are to minimize the influence of 
temperature, electromagnetic frequency, shock, and vibration on the 
emissions measurement. If the design of the PEMS or the installation of 
the PEMS does not minimize the influence of these environmental 
conditions, the final requirements specify that the PEMS must be 
installed in an environmental chamber during the off-cycle test to 
minimize these effects.
iii. Off-Cycle Standards
    For NOX, we are finalizing separate standards for 
distinct modes of operation. To ensure that the duty-cycle 
NOX standards and the off-cycle NOX standards are 
set at the same relative stringency level, the bin 1 standard is 
proportional to the Voluntary Idle standard discussed in Section 
III.B.2.iv, and the bin 2 standard is proportional to a weighted 
combination of the LLC standard discussed in Section III.B.2.iii and 
the SET standard discussed in Section III.B.2.ii. For bin 1, the 
NOX emission standard for all CI primary intended service 
classes is 10.0 g/hr starting in model year 2027. For PM, HC and CO we 
are not setting standards for bin 1 because the emissions from these 
pollutants are very small under idle conditions and idle operation is 
extensively covered by the SET, FTP, and LLC duty cycles discussed in 
Section III.B.2. The combined NOX bin 2 standard is weighted 
at 25 percent of the LLC standard and 75 percent of the SET standard, 
reflecting the nominal flow difference between the two cycles. For HC, 
the bin 2 standard is also set at values proportional to a 25 percent/
75 percent weighted combination of the LLC standard and the SET 
standard.\288\ For PM and CO, the SET, FTP, and LLC standards are the 
same numeric value, so bin 2 is proportional to that numeric standard. 
The numerical values of the off-cycle standards for bin 2 are shown in 
Table III-17.
---------------------------------------------------------------------------

    \288\ See Preamble Section III.B.2 for the HC standards for the 
SET and LLC.
---------------------------------------------------------------------------

    The final numerical off-cycle bin 1 NOX standard reflect 
a conformity factor of 1.0 times the Clean Idle standard discussed in 
Section III.B.2.iv. The final numerical off-cycle bin 2 standards for 
all pollutants reflect a conformity factor of 1.5 times the duty-cycle 
standards set for the LLC and SET cycles discussed in Section 
III.B.2.ii and Section III.B.2.iii. Additionally, as discussed in 
Section III.B.2, the in-use NOX off-cycle standard for 
Medium and Heavy HDE reflects an additional 15 mg/hp-hr NOX 
allowance above the bin 2 standard. Similar to the duty cycle 
standards, the off-cycle standards were set at a level that resulted in 
at least 40 percent compliance margin for the EPA Stage 3 engine. We 
requested and received comments on the appropriate scaling factors or 
other approaches to setting off-cycle standards. After consideration of 
the comments, we believe the final numerical standards are feasible and 
appropriate for certification and in-use testing. We note that the 
final standards are similar, but not identical to, the options proposed 
in the NPRM. As with the duty cycle standards discussed in Preamble 
Section III.B, the data from the EPA Stage 3 engine supported the most 
stringent numeric standards we proposed under low-load operation and 
the most stringent numeric standards we proposed for MY 2027 under high 
load operation. More discussion of the feasibility of these standards 
can be found in the following discussion and in Section III.C.3 and 
Response to Comments Section 11.3.1.

                                     Table III-17--Off-Cycle Bin 2 Standards
----------------------------------------------------------------------------------------------------------------
                       NOX  (mg/hp-hr)                          HC (mg/hp-hr)    PM (mg/hp-hr)     CO (g/hp-hr)
----------------------------------------------------------------------------------------------------------------
58 \a\.......................................................             120              7.5                9
----------------------------------------------------------------------------------------------------------------
\a\ An interim NOX compliance allowance of 15 mg/hp-hr applies for any in-use testing of Medium HDE and Heavy
  HDE. Manufacturers will add the compliance allowance to the NOX standard that applies for each duty cycle and
  for off-cycle Bin 2, for both in-use field testing and laboratory testing as described in 40 CFR 1036, subpart
  E. Note, the NOX compliance allowance doesn't apply to confirmatory testing described in 40 CFR 1036.235(c) or
  selective enforcement audits described in 40 CFR part 1068.

    In the proposal, we requested comment on the in-use test conditions 
over which engines should be required to comply with the standard, 
asking commentors to take into consideration any tradeoffs that broader 
or narrower

[[Page 4349]]

conditions might have on the stringency of the standard we set. After 
considering comments on low ambient air temperature and the available 
data from the low-temperature Stage 3 testing at SwRI described in 
section III.C.2.ii, we are also incorporating an adjustment to the 
numerical off-cycle bin 1 and bin 2 standards for NOX as a 
function of ambient air temperature below 25 [deg]C. The results 
demonstrated higher NOX emissions at low temperatures, 
indicating that standards should be numerically higher to account for 
real-world temperature effects on the aftertreatment system. To 
determine the magnitude of this adjustment, we calculated the increase 
in the Stage 3 engine NOX emissions over the CARB Southern 
Route Cycle at low temperature over the NOX emissions at 25 
[deg]C. These values were linearly extrapolated to determine the 
projected increase at 5 [deg]C versus 25 [deg]C. Table III-18 presents 
the numerical value of each off-cycle bin 1 and bin 2 NOX 
standard at both 25 [deg]C and 5 [deg]C.
    Under the final requirements in 40 CFR 1036.104, the ambient 
temperature adjustment is applied based on the average 1-Hz ambient air 
temperature during the shift day for all data not excluded under 40 CFR 
1036.530(c), calculated as the time-averaged temperature of all 
included data points. If this average temperature is 25 [deg]C or 
above, no adjustment to the standard is made. If the average 
temperature is below 25 [deg]C, the applicable NOX standard 
is calculated using the equations in Table 3 to paragraph (a)(3) of 40 
CFR 1036.104 Table III-18 for the appropriate service class and bin.

                      Table III-18--Temperature Adjustments to the Off-Cycle NOX Standards
----------------------------------------------------------------------------------------------------------------
                                                                         NOX        NOX
                                                                       standard   standard
           Service class                Applicability         Bin       at 25       at 5       Applicable unit
                                                                        [deg]C     [deg]C
----------------------------------------------------------------------------------------------------------------
All...............................  All..................          1         10     \a\ 15  g/hr.
Light HDE.........................  Certification & In-            2         58    \a\ 102  mg/hp-hr.
                                     use.
Medium and Heavy HDE..............  Certification........          2         58    \a\ 102  mg/hp-hr.
Medium and Heavy HDE..............  In-Use...............          2     \a\ 73    \a\ 117  mg/hp-hr.
----------------------------------------------------------------------------------------------------------------
\a\ The Bin 1 and Bin 2 ambient temperature adjustment and the NOX compliance allowance for in-use testing do
  not scale with the FELFTPNOx.

3. Feasibility of the Diesel (Compression-Ignition) Off-Cycle Standards
i. Technologies
    As a starting point for our determination of the appropriate 
numeric levels of the off-cycle emission standards, we considered 
whether manufacturers could meet the duty-cycle standard corresponding 
to the type of engine operation included in a given bin,\289\ as 
follows:
---------------------------------------------------------------------------

    \289\ See preamble Section III.B.3 for details on EPA's 
assessment of the feasibility of the duty-cycle standards.
---------------------------------------------------------------------------

     Bin 1 operation is generally similar to operation at idle 
and the lower speed portions of the LLC.
     Bin 2 operation is generally similar to operation over the 
LLC, the FTP and much of the SET.
    An important question is whether the off-cycle standards would 
require technology beyond what we are projecting would be necessary to 
meet the duty-cycle standards. As described in this section, we do not 
expect the off-cycle standards to require different technologies.
    This is not to say that we expect manufacturers to be able to meet 
these standards with no additional work. Rather, we project that the 
off-cycle standards can be met primarily through additional effort to 
calibrate the duty-cycle technologies to function properly over the 
broader range of in-use conditions. We also recognize that 
manufacturers can choose to include additional technology, if it 
provided a less expensive or otherwise preferred option.
    When we evaluated the technologies discussed in Section III.B.3.i 
with emissions controls that were designed to cover a broad range of 
operation, it was clear that we should set the off-cycle standards to 
higher numerical values than the duty-cycle standards to take into 
account the broader operations covered by the off-cycle test 
procedures. Section III.C.3.ii explains how the technology and controls 
performed when testing with the off-cycle test procedures over a broad 
range of operation. The data presented in Section III.C.3.ii shows that 
even though there are similarities in the operation between the duty 
cycles (SET, FTP, and LLC) and the off-cycle bins 1 and 2, the broader 
range of operation covered by the off-cycle test procedure results in a 
broader range of emissions performance, which justifies setting the 
numeric off-cycle standards higher than the corresponding duty cycle 
standards for equivalent stringency. In addition to this, the off-cycle 
test procedures and standards cover a broader range of ambient 
temperature and pressure, which can also increase the emissions from 
the engine as discussed in Section III.C.2.ii.
ii. Summary of Feasibility Analysis
    To identify appropriate numerical levels for the off-cycle 
standards, we evaluated the performance of the EPA Stage 3 engine in 
the laboratory on five different cycles that were created from field 
data of HD engines that cover a range of off-cycle operation. These 
cycles are the CARB Southern Route Cycle, Grocery Delivery Truck Cycle, 
Drayage Truck Cycle, Euro-VI ISC Cycle (EU ISC) and the Advanced 
Collaborative Emissions Study (ACES) cycle. The CARB Southern Route 
Cycle is predominantly highway operation with elevation changes 
resulting in extended motoring sections followed by high power 
operation. The Grocery Delivery Truck Cycle represents goods delivery 
from regional warehouses to downtown and suburban supermarkets and 
extended engine-off events characteristic of unloading events at 
supermarkets. Drayage Truck Cycle includes near dock and local 
operation of drayage trucks, with extended idle and creep operation. 
Euro-VI ISC Cycle is modeled after Euro VI ISC route requirements with 
a mix of 30 percent urban, 25 percent rural and 45 percent highway 
operation. ACES Cycle is a 5-mode cycle developed as part of ACES 
program. Chapter 3 of the RIA includes figures that show the engine 
speed, engine torque and vehicle speed of the cycles.
    The engine was initially calibrated to minimize NOX 
emissions for the dynamometer duty cycles (SET, FTP, and LLC). It was 
then further calibrated to achieve more optimal performance over off-
cycle operation. The test results shown in Table III-19 provide a 
reasonable basis for evaluating the feasibility of controlling off-
cycle emissions to a useful life of 435,000 miles and 800,000 miles. 
Additionally,

[[Page 4350]]

the engine tested did not include the SCR catalyst volume that is 
included in our cost analysis and that we determined should enable 
lower bin 2 NOX emissions, further supporting that the final 
standards are feasible. Additionally, the 800,000 mile aged 
aftertreatment was tested over the CARB Southern Route Cycle with an 
ambient temperature between 2 [deg]C and 9 [deg]C (6.8 [deg]C average), 
the average of which is slightly above the 5 [deg]C minimum ambient 
temperature that the final requirements specify as the level below 
which test data are excluded.\290\ The summary of the results is in 
Chapter 3 of the RIA. For Light HDE standards, we looked at the data at 
the equivalent of 435,000 miles.\291\ For the Medium and Heavy HDE 
standards we looked at the data at the equivalent of 800,000 
miles.\292\
---------------------------------------------------------------------------

    \290\ The low ambient temperature exclusion was raised from the 
proposed level of -7 [deg]C to 5 [deg]C, since engines can continue 
to use EGR to reduce NOX without the use of an EGR cooler 
bypass at and above 5 [deg]C. See RIA Chapter 3.1.1.2.2 for a 
summary of data from the EPA Stage 3 engine with three different 
idle calibrations.
    \291\ See Section III.B.3.ii for an explanation on why we 
determined data at the equivalent of 435,000 miles was appropriate 
for determining the feasibility of the Light HDE standards.
    \292\ Similar to our reasoning in Section III.B.3.ii for using 
the interpolated data at the equivalent of 650,000 miles to 
determine the feasibility of the duty cycle standards for Medium and 
Heavy HDE, we determined the data at the equivalent of 800,000 was 
appropriate for determining the feasibility of the Medium and Heavy 
HDE off-cycle standards. The one difference is that emission data 
was not collected at the equivalent of 600,000 miles. Therefore, we 
used the data at the equivalent of 800,000 miles (rather than 
assuming the emissions performance changed linearly and 
interpolating the emissions from the data at the equivalent of 
435,000 and 800,000 miles) to determine the emissions performance at 
the equivalent of 650,000 miles. We think it's appropriate to use 
the data at the equivalent of 800,000 miles (rather than the 
interpolated data at the equivalent of 650,000 miles) to account for 
uncertainties in real world performance, particularly given the 
significant increases in useful life, decreases in the numeric 
levels of the standards, and the advanced nature of the 
technologies.

                         Table III-19--EPA Stage 3 NOX Emissions Off-Cycle Operation Without Adjustments for Crankcase Emissions
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                           CARB southern  Grocery deliv.
   Equivalent miles, ambient T ([deg]C)                Bin No.              route cycle        cycle           ACES           EU ISC          Drayage
--------------------------------------------------------------------------------------------------------------------------------------------------------
435,000, 25 [deg]C........................  1 (g/hr)....................             0.7             1.0             0.9             0.4             0.3
                                            2 (mg/hp-hr)................              32              21              20              31              19
800,000, 25 [deg]C........................  1 (g/hr)....................             0.7             3.3             1.5             0.4             1.1
                                            2 (mg/hp-hr)................              47              32              34              32              28
                                                                                         ---------------------------------------------------------------
800,000, 2 to 9 [deg]C....................  1 (g/hr)....................             1.4                            Not tested
                                                                                         ---------------------------------------------------------------
                                            2 (mg/hp-hr)................              87                            Not tested
--------------------------------------------------------------------------------------------------------------------------------------------------------

a. Bin 1 Evaluation
    Bin 1 includes the idle operation and some of the lower speed 
operation that occurs during the FTP and LLC. However, it also includes 
other types of low-load operation observed with in-use vehicles, such 
as operation involving longer idle times than occur in the LLC. To 
ensure that the bin 1 standard is feasible, we set the idle bin 
standard at the level projected to be achievable engine-out with 
exhaust temperatures below the aftertreatment light-off temperature. As 
can be seen from the results in Table III-19, the EPA Stage 3 engine 
performed well below the bin 1 NOX standards. The summary of 
the results is located in Chapter 3 of the RIA.
    For bin 1 we are finalizing NOX standard at a level 
above what we have demonstrated because there are conditions in the 
real world that may prevent the emissions control technology from being 
as effective as demonstrated with the EPA Stage 3 engine. For example, 
under extended idle operation the EGR rate may need to be reduced to 
maintain engine durability. Under extended idle operation with cold 
ambient temperatures, the aftertreatment system can lose NOX 
reduction efficiency which can also increase NOX emissions. 
Taking this under consideration, as well as other factors, we believe 
that the final bin 1 NOX standard in Table III-17 is the 
lowest achievable standard in MY 2027.
b. Bin 2 Evaluations
    As can be seen see from the results in Table III-19, the 
NOX emissions from the Stage 3 engine in bin 2 were below 
the final off-cycle standards for each of the off-cycle duty-cycles. 
The HC and CO emissions measured for each of these off-cycle duty 
cycles were well below the final off-cycle standards for bin 2. PM 
emissions were not measured during the off-cycle tests, but based on 
the effectiveness of DPFs over all engine operation as seen with the 
SET, FTP, and LLC, our assessment is that the final PM standards in Bin 
2 are feasible. The summary of the results is located in Chapter 3 of 
the RIA.
    For bin 2, all the 25 [deg]C off-cycle duty cycles at a full useful 
life of 800,000 miles had emission results below the NOX 
certification standard of 58 mg/hp-hr shown in Table III-19. 
Additionally, the CARB Southern Route Cycle run at ambient temperatures 
under 10 [deg]C had emission results below the Heavy HDE NOX 
in-use off-cycle standard of 106 mg/hp-hr which is the standard at 10 
[deg]C as determined from Equation 40 CFR 1036.104-2. While this cycle 
was run at temperatures above the minimum ambient temperature exclusion 
limit of 5 [deg]C that we are finalizing, we expect actual HDIUT 
testing to be less severe than the demonstration. Nonetheless, since 
the results of the low ambient temperature testing demonstrated higher 
NOX emissions at low temperatures, as shown in Table III-19, 
we have finalized standards that are numerically higher at lower 
temperatures to account for real-world temperature effects on the 
aftertreatment system.
    In the NPRM, we requested comment on the numerical values of the 
off-cycle standards, as well as the overall structure of the off-cycle 
program. We received comments recommending both lower and higher 
numerical standards than were proposed. After considering comments, we 
believe the off-cycle standards that we are finalizing are appropriate 
and feasible values. See Response to Comments Section 11.3.1 for 
further details on these comments and EPA's response to these comments.
4. Compliance and Flexibilities for Off-Cycle Standards
    Given the similarities of the off-cycle standards and test 
procedures to the current NTE requirements that we are

[[Page 4351]]

replacing starting in MY 2027, we evaluated the appropriateness of 
applying the current NTE compliance provisions to the off-cycle 
standards we are finalizing and determined which final compliance 
requirements and flexibilities are applicable to the new final off-
cycle standards, as discussed immediately below.
i. Relation of Off-Cycle Standards To Defeat Devices
    CAA section 203 prohibits bypassing or rendering inoperative a 
certified engine's emission controls. When the engine is designed or 
modified to do this, the engine is said to have a defeat device. With 
today's engines, the greatest risks with respect to defeat devices 
involve manipulation of the engine's electronic controls. EPA refers to 
an element of design that manipulates emission controls as an Auxiliary 
Emission Control Device (AECD).\293\ Unless explicitly permitted by 
EPA, AECDs that reduce the effectiveness of emission control systems 
under conditions which may reasonably be expected to be encountered in 
normal vehicle operation and use are prohibited as defeat devices under 
current 40 CFR 86.004-2.
---------------------------------------------------------------------------

    \293\ 40 CFR 86.082-2 defines Auxiliary Emission Control Device 
(AECD) to mean ``any element of design which senses temperature, 
vehicle speed, engine RPM, transmission gear, manifold vacuum, or 
any other parameter for the purpose of activating, modulating, 
delaying, or deactivating the operation of any part of the emission 
control system.''
---------------------------------------------------------------------------

    For certification, EPA requires manufacturers to identify and 
describe all AECDs.\294\ For any AECD that reduces the effectiveness of 
the emission control system under conditions which may reasonably be 
expected to be encountered in normal vehicle operation and use, 
manufacturers must provide a detailed justification.\295\ We are 
migrating the definition of defeat device from 40 CFR 86.004-2 to 40 
CFR 1036.115(h) and clarifying that an AECD is not a defeat device if 
such conditions are substantially included in the applicable procedure 
for duty-cycle testing as described in 40 CFR 1036, subpart F. Such 
AECDs are not treated as defeat devices because the manufacturer shows 
that their engines are able to meet standards during duty-cycle testing 
while the AECD is active. The AECD might reduce the effectiveness of 
emission controls, but not so much that the engine fails to meet the 
standards that apply.
---------------------------------------------------------------------------

    \294\ See 40 CFR 86.094-21(b)(1)(i)(A).
    \295\ See definition of ``defeat device'' in 40 CFR 86.004-2.
---------------------------------------------------------------------------

    We do not extend this same treatment to off-cycle testing, for two 
related reasons. First, we can have no assurance that the AECD is 
adequately exercised during any off-cycle operation to support the 
conclusion that the engine will consistently meet emission standards 
over all off-cycle operation. Second, off-cycle testing may involve 
operation over an infinite combination of engine speeds and loads, so 
excluding AECDs from consideration as defeat devices during off-cycle 
testing would make it practically impossible to conclude that an engine 
has a defeat device.
    If an engine meets duty-cycle standards and the engine has no 
defeat devices, we should be able to expect engines to achieve a 
comparable level of emission control for engine operation that is 
different than what is represented by the certification duty cycles. 
The off-cycle standards and measurement procedures allow for a modest 
increase in emissions for operation that is different than the duty 
cycle, but manufacturers may not change emission controls to increase 
emissions to the off-cycle standard if those controls were needed to 
meet the duty-cycle standards. The finalized off-cycle standards are 
set at a level that is feasible under all operating conditions, so we 
expect that under much of the engine operation the emissions are well 
below the final off-cycle standards.
ii. Heavy-Duty In-Use Testing Program
    Under the current manufacturer-run heavy-duty in-use testing 
(HDIUT) program, EPA annually selects engine families to evaluate 
whether engines are meeting current emissions standards. Once we submit 
a test order to the manufacturer to initiate testing, it must contact 
customers to recruit vehicles that use an engine from the selected 
engine family. The manufacturer generally selects five unique vehicles 
that have a good maintenance history, no malfunction indicators on, and 
are within the engine's regulatory useful life for the requested engine 
family. The tests require use of portable emissions measurement systems 
(PEMS) that meet the requirements of 40 CFR part 1065, subpart J. 
Manufacturers collect data from the selected vehicles over the course 
of a day while they are used for their normal work and operated by a 
regular driver, and then submit the data to EPA. Compliance is 
currently evaluated with respect to the NTE standards.
    With some modifications from proposal, we are continuing the HDIUT 
program, with compliance with respect to the new off-cycle standards 
and test procedures added to the program beginning with MY 2027 
engines. As proposed, we are not carrying forward the Phase 2 HDIUT 
requirements in 40 CFR 86.1915 once the NTE phases out after MY 2026. 
Under the current NTE based off-cycle test program, if a manufacturer 
is required to test ten engines under Phase 1 testing and less than 
eight fully comply with the vehicle pass criteria in 40 CFR 86.1912, we 
could require the manufacturer to initiate Phase 2 HDIUT testing which 
would require manufacturers to test an additional 10 engines. After 
consideration of comments, we are generally finalizing our overall long 
term HDIUT program's engine testing steps and pass/fail criteria as 
proposed; however, EPA believes that an interim approach in the initial 
two years of the program is appropriate, as manufacturers transition to 
the final standards, test procedures, and requirements, while still 
providing overall compliance assurance during that transition. More 
specifically, we are finalizing that compliance with the off-cycle 
standards would be determined by testing a maximum of fifteen engines 
for MYs 2027 and MY 2028 under the interim provisions, and ten engines 
for MYs 2029 and later. As noted in the proposal, the testing of a 
maximum of ten engines was the original limit under Phase 1 HDIUT 
testing in 40 CFR 86.1915. Similar to the current Phase 1 HDIUT 
requirements in 40 CFR 86.1912, the finalized 40 CFR 1036.425 and 
finalized interim provision in 40 CFR 1036.150(z) require initially 
testing five engines. Various outcomes are possible based on the 
observed number of vehicle passes or failures from manufacturer-run in-
use testing, as well as other supplemental information. Under the 
interim provisions for MYs 2027 and 2028, if four of the first test 
vehicles meet the off-cycle standards, testing stops, and no other 
action is required of the manufacturer for that diesel engine family. 
For MYs 2029 and later, if five of the first test vehicles meet the 
off-cycle standards, testing stops, and no other action is required of 
the manufacturer for that diesel engine family. For MYs 2027 and 2028, 
if two of those engines do not comply fully with the off-cycle bin 
standards, the manufacturer would then test five additional engines for 
a total of ten. For MYs 2029 and later, if one of those engines does 
not comply fully with the off-cycle bin standards, the manufacturer 
would then test a sixth engine. For MYs 2027 and 2028, if eight of the 
ten engines tested pass, testing stops, and no other action is required 
of the manufacturer for that diesel engine family under the program for 
that model

[[Page 4352]]

year. For MYs 2029 and later, if five of the six engines tested pass, 
testing stops, and no other action is required of the manufacturer for 
that diesel engine family under the program for that model year. For 
MYs 2027 and 2028, if three or more of the first ten engines tested do 
not pass, the manufacturer may test up to five additional engines until 
a maximum of fifteen engines have been tested. For MYs 2029 and later, 
when two or more of the first six engines tested do not pass, the 
manufacturer must test four additional engines until a total of ten 
engines have been tested. If the arithmetic mean of the emissions from 
the ten, or up to fifteen under the interim provisions, engine tests 
determined in Sec.  1036.530(g), or Sec.  1036.150(z) under the interim 
provisions, is at or below the off-cycle standard for each pollutant, 
the engine family passes and no other action is required of the 
manufacturer for that diesel engine family. If the arithmetic mean of 
the emissions from the ten, or up to fifteen under the interim 
provisions, engines for either of the two bins for any of the 
pollutants is above the respective off-cycle bin standard, the engine 
family fails and the manufacturer must join EPA in follow-up 
discussions to determine whether any further testing, investigations, 
data submissions, or other actions may be warranted. Under the final 
requirements, the manufacturer may accept a fail result for the engine 
family and discontinue testing at any point in the sequence of testing 
the specified number of engines.
    We received comment on the elimination of Phase 2 testing. See 
Response to Comment Section 11.5.1 for further information on these 
comments and EPA's response to these comments. As noted in the 
preceding paragraphs, we are finalizing elimination of Phase 2 testing. 
However, we also are clarifying what happens when an engine family 
fails under the final program. In such a case, three outcomes are 
possible. First, we may ultimately decide not to take further action if 
no nonconformity is indicated after a thorough evaluation of the causes 
or conditions that caused vehicles in the engine family to fail the 
off-cycle standards, and a review of any other supplemental information 
obtained separately by EPA or submitted by the manufacturer shows that 
no significant nonconformity exists. Testing would then stop, and no 
other action would be required of the manufacturer for that diesel 
engine family under the program for that year. Second, we may seek some 
form of remedial action from the manufacturer based on our evaluation 
of the test results and review of other supplemental information. 
Third, and finally, in situations where a significant nonconformity is 
observed during testing, we may order a recall action for the diesel 
engine family in question if the manufacturer does not voluntarily 
initiate an acceptable remedial action.
    In the NPRM, we proposed allowing manufacturers to test a minimum 
of 2 engines using PEMS, in response to a test order program, provided 
they measure, and report in-use data collected from the engine's on-
board NOX measurement system. EPA received comments 
expressing concerns on the feasibility of this alternate in-use testing 
option. Given meaningful uncertainties in whether technological 
advancement of measurement capabilities of these sensors will occur by 
MY 2027, at this time, EPA is not including the proposed option in 40 
CFR 1036.405(g) and not finalizing this alternative test program option 
in this action. The final in-use option for manufacturers to show 
compliance with the off-cycle standard will require the use of 
currently available PEMS to measure criteria pollutant emissions, with 
the sampling and measurement of emission concentrations in a manner 
similar to the current NTE in-use test program as described in 40 CFR 
part 1036, subpart E, and Section III.C of this preamble. See Response 
to Comment Section 11.5.3 for further information on these comments and 
EPA's response to these comments.
    In the NPRM, we proposed to not carry forward the provision in 40 
CFR 86.1908(a)(6) that considers an engine misfueled if operated on a 
biodiesel fuel blend that is either not listed as allowed or otherwise 
indicated to be an unacceptable fuel in the vehicle's owner or operator 
manual. We also proposed in 40 CFR 1036.415(c)(1) to allow vehicles to 
be tested for compliance with the new off-cycle standards on any 
commercially available biodiesel fuel blend that meets the 
specifications for ASTM D975 or ASTM D7467.
    We received comments on these proposed requirements. After 
considering the comments, we have altered provisions in the final rule 
from what was proposed. EPA agrees with the commenters' recommendation 
to restrict in-use off-cycle standards testing on vehicles that have 
been fueled with biodiesel to those that are either expressly allowed 
in the vehicle's owner or operator manual or not otherwise indicated as 
an unacceptable fuel in the vehicle's owner or operator manual or in 
the engine manufacturer's published fuel recommendations. EPA believes, 
as explained in section IV.H of this preamble, that data show biodiesel 
is compliant with ASTM D975, D7467 and D6751, that the occurrence of 
metal contamination in the fuel pool is extremely low, and that the 
metal content of biodiesel is low. However, EPA understands that 
manufacturers have little control over the quality of fuel that their 
engines will encounter over years of in-use operation.\296\ To address 
uncertainties, EPA is modifying the proposed approach to in-use off-
cycle standards testing and will allow manufacturers to continue to 
exempt engines from in-use off-cycle standards testing if the engine is 
being operated on biofuel that exceeds the manufacturers maximum 
allowable biodiesel percentage usable in their engines, as specified in 
the engine owner's manual. See 40 CFR 1036.415(c)(1).
---------------------------------------------------------------------------

    \296\ At this time, as explained in the proposed rule, EPA did 
not propose and is not taking final action to regulate biodiesel 
blend metal content because the available data does not indicate 
that there is widespread off-specification biodiesel blend stock or 
biodiesel blends in the marketplace. EPA also notes that the request 
to set a maximum nationwide biodiesel percentage of 20 percent is 
outside the scope of this final rule.
---------------------------------------------------------------------------

    EPA requested comment on a process for a manufacturer to receive 
EPA approval to exempt test results from in-use off-cycle standards 
testing from being considered for potential recall if an engine 
manufacturer can show that the vehicle was historically fueled with 
biodiesel blends whose B100 blendstock did not meet the ASTM D6751-20a 
limit for Na, K, Ca, and/or Mg metal (metals which are a byproduct of 
biodiesel production) or contaminated petroleum based fuels (i.e. if 
the manufacturer can show that the vehicle was misfueled), and the 
manufacturer can show that misfueling lead to degradation of the 
emission control system performance. 40 CFR 1068.505 describes how 
recall requirements apply for engines that have been properly 
maintained and used. Given the risk of metal contamination from 
biofuels and in some rare cases petroleum derived fuels, EPA will be 
willing to engage with any information manufacturers can share to 
demonstrate that the fueling history caused an engine to be 
noncompliant based on improper maintenance or use. It is envisioned 
that this engagement would include submission by the manufacturer of a 
comparison of the degraded emission control system to a representative 
compliant system of similar miles with respect to content of the 
contaminant, including an analysis of the level of the poisoning agents 
on the catalysts in the engine's aftertreatment system. This

[[Page 4353]]

process addresses concerns expressed by a commentor who stated that it 
would be difficult if not impossible for a manufacturer to provide 
``proof of source'' of the fuel contamination that led to the 
degradation in catalyst performance. This clarifies that the 
manufacturer must only determine the amount of poisoning agent present 
versus a baseline aftertreatment system.
    In the NPRM, we requested comment on the need to measure PM 
emissions during in-use off-cycle testing of engines that comply with 
MY 2027 or later standards if they are equipped with a DPF. PEMS 
measurement is more complicated and time-consuming for PM measurements 
than for gaseous pollutants such as NOX and eliminating it 
for some or all of in-use off-cycle standards testing would provide 
significant cost savings. We received comments both in support of and 
in opposition to continuing to require measurement of PM during in-use 
off-cycle standards testing. After considering these comments, EPA 
believes that historic test results from the manufacturer run in-use 
test program indicate that there is not a PM compliance problem for 
properly maintained engines. Additionally, we believe that removing the 
requirement for in-use off-cycle PM standards testing will not lead 
manufacturers to stop using wall flow DPF technology to meet the PM 
standards. Therefore, EPA is not including the proposed requirement for 
manufacturers to measure PM in the final 40 CFR 1036.415(d)(1) but is 
modifying that requirement from proposal to include a final provision 
in this paragraph that EPA may request PM measurement and that 
manufacturers must provide that measurement if EPA requests it. 
Generally, EPA expects that test orders issued by EPA under 40 CFR 
1036.405 will not include a requirement to measure PM.
    Furthermore, EPA received comments on the subject of the need to 
measure NMHC emissions during in-use off-cycle testing of engines that 
comply with MY 2027 or later standards. After considering comments, EPA 
believes that historic test results from the manufacturer run in-use 
test program indicate that there is not an NMHC compliance problem for 
properly maintained engines. EPA is not including the proposed 
requirement for manufacturers to measure NMHC in the final 40 CFR 
1036.415(d)(1) but is modifying that requirement from proposal to 
include a provision in this paragraph that EPA may request NMHC 
measurement and that manufacturers must provide that measurement if EPA 
requests it. Generally, EPA expects that test orders issued by EPA 
under 40 CFR 1036.405 will not include a requirement to measure NMHC. 
See Response to Comment Section 11.5.5 for further information on these 
comments and EPA's response to comments on the subject of in-use off-
cycle standards PM and NMHC testing.
iii. PEMS Accuracy Margin
    EPA worked with engine manufacturers on a joint test program to 
establish measurement allowance values to account for the measurement 
uncertainty associated with in-use testing in the 2007-time frame for 
gaseous emissions and the 2010-time frame for PM emissions to support 
NTE in-use testing.\297\ \298\ \299\ PEMS measurement allowance values 
in 40 CFR 86.1912 are 0.01 g/hp-hr for HC, 0.25 g/hp-hr for CO, 0.15 g/
hp-hr for NOX, and 0.006 g/hp-hr for PM. We are maintaining 
the same values for HC, CO, and PM in this rulemaking. For 
NOX we are finalizing an off-cycle NOX accuracy 
margin (formerly known as measurement allowance) that is 5 percent of 
the off-cycle standard for a given bin. This final accuracy margin is 
supported by PEMS accuracy margin work at SwRI. The SwRI PEMS accuracy 
margin testing was done on the Stage 3 engine, which was tested over 
five field cycles with three different commercially available PEMS. 
EPA's conclusion after assessing the results of that study, was that 
accuracy margins set at 0.4 g/hr for bin 1 and 5 mg/hp-hr for bin 2 
were appropriate.
---------------------------------------------------------------------------

    \297\ Feist, M.D.; Sharp, C.A; Mason, R.L.; and Buckingham, J.P. 
Determination of PEMS Measurement Allowances for Gaseous Emissions 
Regulated Under the Heavy-Duty Diesel Engine In-Use Testing Program. 
SwRI 12024, April 2007.
    \298\ Feist, M.D.; Mason, R.L.; and Buckingham, J.P. Additional 
Analyses of the Monte Carlo Model Developed for the Determination of 
PEMS Measurement Allowances for Gaseous Emissions Regulated Under 
the Heavy-Duty Diesel Engine In-Use Testing Program. SwRI[supreg] 
12859. July 2007.
    \299\ Khalek, I.A.; Bougher, T.L.; Mason, R.L.; and Buckingham, 
J.P. PM-PEMS Measurement Allowance Determination. SwRI Project 
03.14936.12. June 2010.
---------------------------------------------------------------------------

    The accuracy margins we are finalizing differ from the 10 percent 
of the standard margin proposed in the NPRM, which was based on an 
earlier study by JRC. This SwRI PEMS accuracy margin study was on-going 
at the time the NPRM was published, and the results were only available 
post-NPRM publication.\300\ However, the NPRM did note that we would 
consider the results of the SwRI PEMS study when they became available, 
and that the final off-cycle bin NOX standards could be 
higher or lower than what we proposed. EPA requested and received 
comments on the value of the PEMS accuracy margin for NOX; 
some commenters encouraged EPA to account for the SwRI PEMS accuracy 
work that was carried out on the Stage 3 engine. We initially planned 
to consider the results of this work and this was further supported 
through recommendations by some commentors; thus, we believe that 
incorporating the results of the latest study to determine an off-cycle 
NOX accuracy margin is appropriate. The SwRI PEMS study is 
further discussed in RIA Chapter 2. The study consisted of testing the 
Stage 3 engine with three commercially available PEMS units over 19 
different tests. These tests were 6 to 9 hours long, covering a wide 
range of field operation. In addition, the Stage 3 engine was tested in 
three different configurations to cover the range of emissions levels 
expected from an engine both meeting and failing the final standards. 
We believe, based on this robust data set that was evaluating using the 
finalized test procedures, the SwRI study provides a more accurate 
assessment of PEMS measurement uncertainty from field testing of heavy-
duty engines than what was determined from the JRC study that we relied 
on in the proposal for the proposed 10 percent margin. See Response to 
Comment Section 11.6 for further information on these comments and 
EPA's response to these comments.
---------------------------------------------------------------------------

    \300\ The data and the results from the study were added to the 
public docket prior to the signing of the final rule.
---------------------------------------------------------------------------

    It should be noted that our off-cycle test procedures already 
include a linear zero and span drift correction over at least the shift 
day, and we are finalizing requirements for at least hourly zero drift 
checks over the course of the shift day on purified air. We believe 
that the addition of these checks and the additional improvements we 
implemented helped facilitate a measurement error that is lower than 
the analytically derived JRC value of 10 percent.\301\
---------------------------------------------------------------------------

    \301\ Giechaskiel B., Valverde V., Clairotte M. 2020 Assessment 
of Portable Emissions Measurement Systems (PEMS) Measurement 
Uncertainty. JRC124017, EUR 30591 EN. https://publications.europa.eu/en/publications.
---------------------------------------------------------------------------

    We are updating 40 CFR 1065.935 to require hourly zeroing of the 
PEMS analyzers using purified air for all analyzers. We are also 
updating the drift limits for NOX analyzers to improve data 
quality. Specifically, for NOX analyzers, we are requiring 
an hourly or more frequent zero verification limit of 2.5 ppm, a zero-
drift limit over the entire shift day of 10 ppm, and a span drift limit 
between the beginning and end of the shift day or more frequent span 
verification(s) of 4 percent of the

[[Page 4354]]

measured span value. In the NPRM, we requested comment on the test 
procedure updates in 40 CFR 1065.935 and any changes that would reduce 
the PEMS measurement uncertainty. We received no comments on this topic 
other than a few minor edits and are finalizing these updates with 
minor edits for clarification.
iv. Demonstrating Off-Cycle Standards for Certification
    Consistent with current certification requirements in 40 CFR 
86.007-21(p)(1), we are finalizing a new paragraph in 40 CFR 
1036.205(p) that requires manufacturers to provide a statement in their 
application for certification that their engine complies with the off-
cycle standards, along with testing or other information to support 
that conclusion. We are finalizing this provision as proposed.

D. Summary of Spark-Ignition HDE Exhaust Emission Standards and Test 
Procedures

    This section summarizes the exhaust emission standards, test 
procedures, and other requirements and flexibilities we are finalizing 
for certain spark-ignition (SI) heavy-duty engines. The exhaust 
emission provisions in this section apply for SI engines installed in 
vehicles above 14,000 lb GVWR and incomplete vehicles at or below 
14,000 lb GVWR, but do not include engines voluntarily certified to or 
installed in vehicles subject to 40 CFR part 86, subpart S.
    As described in this Section III.D, Spark-ignition HDE 
certification will continue to be based on emission performance in lab-
based engine dynamometer testing, which will include a new SET duty 
cycle to address high load operation. High load temperature protection 
and idle emission control requirements are also added to supplement our 
current FTP and new SET duty cycles. We are also lengthening the useful 
life and emissions-related warranty periods for all heavy-duty engines, 
including Spark-ignition HDE, as detailed in Sections IV.A and IV.B.1 
of this preamble.
    The final exhaust emission standards in 40 CFR 1037.104 apply 
starting in MY 2027. This final rule includes new standards over the 
FTP duty cycle currently used for certification, as well as new 
standards over the SET duty cycle to ensure manufacturers of Spark-
ignition HDE are designing their engines to address emissions in during 
operation that is not covered by the FTP. The new standards are shown 
in Table III-20.

                                                            Table III-20--Final Duty Cycle Emission Standards for Spark-Ignition HDE
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                  Model year 2026 and earlier \a\                                    Model year 2027 and later
                                                                 -------------------------------------------------------------------------------------------------------------------------------
                           Duty cycle                              NOX  (mg/hp-                                                    NOX  (mg/hp-
                                                                        hr)        HC (mg/hp-hr)   PM (mg/hp-hr)   CO (g/hp-hr)         hr)        HC (mg/hp-hr)   PM (mg/hp-hr)   CO (g/hp-hr)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
SET.............................................................  ..............  ..............  ..............  ..............              35              60               5            14.4
FTP.............................................................             200             140              10            14.4              35              60               5             6.0
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Current emission standards for NOX, HC, and PM were converted from g/hp-hr to mg/hp-hr to compare with the final standards.

    Our proposal included two options of fuel-neutral standards that 
applied the same numerical standards across all primary intended 
service classes. The proposed NOX and PM standards for the 
SET and FTP duty cycles were based on the emission performance of 
technologies evaluated in our HD CI engine technology demonstration 
program.\302\ We based the proposed SET and FTP standards for HC and CO 
on HD SI engine performance.
---------------------------------------------------------------------------

    \302\ Our assessment of the projected technology package for 
compression-ignition engines is based on both CARB's and EPA's 
technology demonstration programs. See Section III.B for a 
description of those technologies and test programs.
---------------------------------------------------------------------------

    Three organizations specifically expressed support for adopting the 
standards of proposed Option 1 for Spark-ignition HDE. The final 
standards are based largely on the emission levels of proposed Option 
1, with some revisions to account for a single-step program, starting 
in MY 2027. Some organizations commented that the proposed SI standards 
were challenging enough to need the flexibility of ABT for HC and CO. 
Consistent with the proposal for this rule, we are finalizing an ABT 
program for NOX credits only and are discontinuing the 
current options for manufacturers to generate HC and PM credits. We did 
not request comment on and are not finalizing an option for 
manufacturers to generate credits for CO. See Section IV.G of this 
preamble and section 12 of the Response to Comments document for more 
information on the final ABT program.
    We are remaining generally consistent with a fuel neutral approach 
in the final SET and FTP standards, with the exception of CO for Spark-
ignition HDE over the new SET duty cycle. We expand on our rationale 
for this deviation from fuel neutrality in Section III.D.1 where we 
also describe our rationale for the final program, including a summary 
of the feasibility demonstration, available data, and comments 
received.
    After considering comments, we are revising three other proposed 
provisions for Spark-ignition HDE as described in Section . Two new 
requirements in 40 CFR 1036.115(j) focus on ensuring catalyst 
efficiency at low loads and proper thermal management at high loads. We 
are finalizing, with additional clarification, a new OBD flexibility 
for ``sister vehicles''. We did not propose and are not finalizing 
separate off-cycle standards, manufacturer-run in-use testing 
requirements, or a low-load duty cycle for Spark-ignition HDE at this 
time.\303\
---------------------------------------------------------------------------

    \303\ See section 3 of the Response to Comments document for 
more information.
---------------------------------------------------------------------------

    The proposed rule provided an extensive discussion of the rationale 
and information supporting the proposed standards (87 FR 17479, March 
28, 2022). The RIA includes additional information related to the range 
of technologies to control criteria emissions, background on applicable 
test procedures, and the full feasibility analysis for Spark-ignition 
HDE. See also section 3 of the Response to Comments for a detailed 
discussion of the comments and how they have informed this final rule.
1. Basis of the Final Exhaust Emission Standards and Test Procedures
    EPA conducted a program with SwRI to better understand the 
emissions performance limitations of current heavy-duty SI engines as 
well as investigate the feasibility of advanced three-way catalyst 
aftertreatment and technologies and strategies to meet our proposed 
exhaust emission standards.\304\ Our demonstration included the use of 
advanced catalyst

[[Page 4355]]

technologies artificially aged to the equivalent of 250,000 miles and 
engine downspeeding. Our feasibility analyses for the exhaust emission 
standards are based on the SwRI demonstration program. Feasibility of 
the FTP standards is further supported by compliance data submitted by 
manufacturers for the 2019 model year. We also support the feasibility 
of the SET standards using engine fuel mapping data from a test program 
performed by the agency as part of the HD GHG Phase 2 rulemaking. See 
Chapter 3.2 of the RIA for more details related to the SwRI 
demonstration program and the two supporting datasets.
---------------------------------------------------------------------------

    \304\ Ross, M. (2022). Heavy-Duty Gasoline Engine Low 
NOX Demonstration. Southwest Research Institute. Final 
Report EPA Contract 68HERC20D0014.
---------------------------------------------------------------------------

    Results from our SI HDE technology demonstration program (see Table 
III-21 and Table III-22) show that the NOX standards based 
on our CI engine feasibility analysis are also feasible for SI HDEs 
over the SET and FTP duty cycles. The NOX standard was 
achieved in this test program by implementing an advanced catalyst with 
minor catalyst system design changes, and NOX levels were 
further improved with engine down-speeding. The emission control 
strategies that we evaluated did not specifically target PM emissions, 
but we note that PM emissions remained low in our demonstration. We 
project SI HDE manufacturers will maintain near-zero PM levels with 
limited effort. The following sections discuss the feasibility of the 
HC and CO standards over each of the duty cycles and the basis for our 
final numeric standards' levels.
i. Federal Test Procedure and Standards for Spark-Ignition HDE
    After considering comments, we are finalizing FTP standards that 
differ from our proposed options for Spark-ignition HDE. We are 
finalizing standards of 35 mg/hp-hr NOX, 5 mg/hp-hr PM, 60 
mg/hp-hr HC, and 6.0 g/hp-hr CO over the FTP duty cycle in a single 
step for MY 2027 and later engines. The NOX and HC standards 
match the MY 2027 step of proposed Option 1; the PM and CO standards 
match the MY 2031 step of Option 1. All of these standards were 
demonstrated to be technologically feasible in EPA's SI engine test 
program.
    As shown in Table III-21, use of advanced catalysts provided 
NOX emission levels over the FTP duty cycle well below 
today's standards and below the certification levels of some of the 
best performing engines certified in recent years.\305\ Engine down-
speeding further decreased CO emissions while maintaining 
NOX, NMHC, and PM control. Engine down-speeding also 
resulted in a small improvement in fuel consumption over the FTP duty 
cycle, with fuel consumption being reduced from 0.46 to 0.45 lb/hp-hr. 
See Chapter 3.2.3 of the RIA for an expanded description of the test 
program and results.
---------------------------------------------------------------------------

    \305\ As presented in Chapter 3.2 of the RIA, MY 2019 gasoline-
fueled HD SI engine certification results included NOX 
levels ranging from 40 to 240 mg/hp-hr at a useful life of 110,000 
miles. MY 2019-2021 alternative-fueled (CNG, LPG) HD SI engine 
certification results included NOx levels ranging from 6 to 70 mg/
hp-hr at the same useful life.

    Table III-21--Exhaust Emission Results From FTP Duty Cycle Testing in the HD SI Technology Demonstration
----------------------------------------------------------------------------------------------------------------
                                                   NOX  (mg/hp-
                                                        hr)        PM (mg/hp-hr)   HC (mg/hp-hr)   CO (g/hp-hr)
----------------------------------------------------------------------------------------------------------------
Current Standards MY 2026 and earlier...........             200              10             140            14.4
Final Standards MY 2027 and later...............              35               5              60               6
Test Program Base Engine with Advanced Catalyst               19             4.8              32             4.9
 \a\............................................
Test Program Down-sped Engine with Advanced                   18             4.5              35            0.25
 Catalyst \b\...................................
----------------------------------------------------------------------------------------------------------------
\a\ Base engine's manufacturer-stated maximum test speed is 4715 RPM; advanced catalyst aged to 250,000 miles.
\b\ Down-sped engine's maximum test speed lowered to 4000 RPM; advanced catalyst aged to 250,000 miles.

    All SI HDEs currently on the market use a three-way catalyst (TWC) 
to simultaneously control NOX, HC, and CO emissions.\306\ We 
project most manufacturers will continue to use TWC technology and will 
also adopt advanced catalyst washcoat technologies and refine their 
existing catalyst thermal protection (fuel enrichment) strategies to 
prevent damage to engine and catalyst components over the longer useful 
life period we have finalized. We expect manufacturers, who design and 
have full access to the engine controls, could achieve similar emission 
performance as we demonstrated by adopting other, more targeted 
approaches, including a combination of calibration changes, optimized 
catalyst location, and fuel control strategies that EPA was unable to 
evaluate in our demonstration program due to limited access to 
proprietary engine controls.
---------------------------------------------------------------------------

    \306\ See Chapter 1.2 of the RIA for a detailed description of 
the TWC technology and other strategies HD SI manufacturers use to 
control criteria emissions.
---------------------------------------------------------------------------

    In the proposal we described how the FTP duty cycle did not 
sufficiently incentivize SI HDE manufacturers to address fuel 
enrichment and the associated CO emissions that are common under higher 
load operations in the real-world. In response to our proposed rule, 
one manufacturer shared technical information with us regarding an SI 
engine architecture under development that is expected to reduce or 
eliminate enrichment and the associated CO emissions.\307\ The company 
indicated that the low CO emissions may come at the expense of HC 
emission reduction in certain operation represented by the FTP duty 
cycle, and reiterated their request for an 80 mg/hp-hr HC standard, as 
was stated in their written comments. We are not finalizing an HC 
standard of 80 mg/hp-hr as requested in comment. For the FTP duty 
cycle, the EPA test program achieved HC levels more than half of the 
requested level without compromising NOX or CO emission 
control (see Table III-21), which clearly demonstrates feasibility.
---------------------------------------------------------------------------

    \307\ U.S. EPA. Stakeholder Meeting Log. December 2022.
---------------------------------------------------------------------------

    While we demonstrated emission levels below the final standards of 
60 mg HC/hp-hr and 35 mg NOX/hp-hr over the FTP duty cycle 
in our SI HDE testing program, we expect manufacturers to apply a 
compliance margin to their certification test results to account for 
uncertainties, such as production variation. Additionally, we believe 
manufacturers would have required additional lead time to implement the 
demonstrated emission levels broadly across all heavy-duty SI engine 
platforms for the final useful life periods. Since we are finalizing a 
single-step program starting in MY 2027, as discussed in Section 
III.A.3 of this preamble, we continue to consider 60 mg HC/hp-hr and 35 
mg NOX/hp-hr the appropriate level of the standards for

[[Page 4356]]

that model year, as proposed in the MY 2027 step of proposed Option 1.
ii. Supplemental Emission Test and Standards for Spark-Ignition HDE
    The existing SET duty cycle, currently only applicable to CI 
engines, is a ramped modal cycle covering 13 steady-state torque and 
engine speed points that is intended to exercise the engine over 
sustained higher load and higher speed operation. Historically, in 
light of the limited range of applications and sales volumes of SI 
heavy-duty engines, especially compared to CI engines, we believed the 
FTP duty cycle was sufficient to represent the high-load and high-speed 
operation of SI engine-powered heavy-duty vehicles. As the market for 
SI engines increases for use in larger vehicle classes, these engines 
are more likely to operate under extended high-load conditions. To 
address these market shifts, we proposed to apply the SET duty cycle 
and new SET standards to Spark-ignition HDE, starting in model year 
2027. This new cycle would ensure that emission controls are properly 
functioning in the high load and speed conditions covered by the SET.
    We are finalizing the addition of the SET duty cycle for the Spark-
ignition HDE primary intended service class, as proposed.\308\ We 
requested comment on revisions we should consider for the CI-based SET 
procedure to adapt it for SI engines. We received no comments on 
changes to the procedure itself and the SET standards for Spark-
ignition HDE are based on the same SET procedure as we are finalizing 
for heavy-duty CI engines. After considering comments, we are 
finalizing SET standards that differ from our proposed options for 
Spark-ignition HDE.
---------------------------------------------------------------------------

    \308\ See our updates to the SET test procedure in 40 CFR 
1036.505.
---------------------------------------------------------------------------

    The EPA HD SI technology demonstration program evaluated emission 
performance over the SET duty cycle. As shown in Table III-22, the 
NOX and NMHC emissions over the SET duty cycle were 
substantially lower than the emissions from the FTP duty cycle (see 
Table III-21). Lower levels of NMHC were demonstrated, but at the 
expense of increased CO emissions in those higher load operating 
conditions. Engine down-speeding improved CO emissions significantly, 
while NOX, NMHC, and PM remained low.\309\ The considerably 
lower NOX and HC in our SET duty cycle demonstration results 
leave enough room for manufacturers to calibrate the tradeoff in TWC 
emission control of NOX, HC, and CO to continue to fine-tune 
CO. See Chapter 3.2 of the RIA for an expanded description of the test 
program and results.
---------------------------------------------------------------------------

    \309\ Engine down-speeding also resulted in a small improvement 
in brake specific fuel consumption over the SET duty cycle reducing 
from 0.46 to 0.44 lb/hp-hr.

    Table III-22--Exhaust Emission Results From SET Duty Cycle Testing in the HD SI Technology Demonstration
----------------------------------------------------------------------------------------------------------------
                                                   NOX  (mg/hp-
                                                        hr)        PM (mg/hp-hr)   HC (mg/hp-hr)   CO (g/hp-hr)
----------------------------------------------------------------------------------------------------------------
Final Standards MY 2027 and later...............              35               5              60            14.4
Test Program Base Engine with Advanced Catalyst                8           \c\ 7               6            36.7
 \a\............................................
Test Program Down-sped Engine with Advanced                    5               3               1            7.21
 Catalyst \b\...................................
----------------------------------------------------------------------------------------------------------------
\a\ Base engine's manufacturer-stated maximum test speed is 4715 RPM; advanced catalyst aged to 250,000 miles.
\b\ Down-sped engine's maximum test speed lowered to 4000 RPM; advanced catalyst aged to 250,000 miles.
\c\ As noted in Chapter 3.2 of the RIA, the higher PM value was due to material separating from the catalyst mat
  during the test and is not indicative of the engine's ability to control engine-generated PM emissions at the
  higher load conditions of the SET.

    Similar to our discussion related to the FTP standards, we expect 
manufacturers, who design and have full access to the engine controls, 
could achieve emission levels comparable to or lower than our 
feasibility demonstration over the SET duty cycle by adopting other 
approaches, including a combination of calibration changes, optimized 
catalyst location, and fuel control strategies that EPA was unable to 
evaluate due to limited access to proprietary engine controls. In fact, 
we are aware of advanced engine architectures that can reduce or 
eliminate enrichment, and the associated CO emissions, by maintaining 
closed loop operation.\310\
---------------------------------------------------------------------------

    \310\ See Chapter 1 of the RIA for a description of fuel 
enrichment, when engine operation deviates from closed loop, and its 
potential impact on emissions.
---------------------------------------------------------------------------

    We proposed Spark-ignition HDE standards for HC and CO emissions on 
the SET cycle that were numerically equivalent to the respective 
proposed FTP standards. Our intent was to ensure that SI engine 
manufacturers utilize emission control hardware and calibration 
strategies to control emissions during high load operation to levels 
similar to the FTP duty cycle.\311\ We retain this approach for HC, 
but, after considering comments, the final CO standard is revised from 
that proposed. One commenter indicated that manufacturers would need CO 
credits to achieve the proposed standards. Another commenter suggested 
that EPA underestimated the modifications manufacturers would need to 
make to fully transition away from the fuel enrichment strategies they 
currently use to protect their engines. The same commenter requested 
that EPA delay the SET to start in model year 2031 or temporarily 
exclude the highest load points over the test to provide additional 
lead time for manufacturers.
---------------------------------------------------------------------------

    \311\ Test results presented in Chapter 3.2 of the RIA indicate 
that these standards are achievable when the engine controls limit 
fuel enrichment and maintain closed loop control of the fuel-air 
ratio.
---------------------------------------------------------------------------

    We are not finalizing an option for manufacturers to generate CO 
credits. We believe a delayed implementation of SET, as requested, 
would further delay manufacturers' motivation to focus on high load 
operation to reduce enrichment and the associated emissions reductions 
that would result. Additionally, our objective for adding new standards 
over the SET duty cycle is to capture the prolonged, high-load 
operation not currently represented in the FTP duty cycle, and the 
commenter's recommendation to exclude the points of highest load would 
be counter to that objective.
    We agree with commenters that the new SET duty cycle and standards 
will be a challenge for heavy-duty SI manufacturers but maintain that 
setting a feasible technology-forcing CO standard is consistent with 
our authority under the CAA. After further considering the comments and 
assessing CO data from the EPA heavy-duty SI test program, the final 
new CO standard we

[[Page 4357]]

are adopting is less stringent than proposed to provide manufacturers 
additional margin for ensuring compliance with that pollutant's 
standard over the new test procedure for Spark-ignition HDE. Given this 
final standard, we determined that neither ABT or more lead time are 
appropriate or required. The Spark-ignition HDE standard for CO 
emissions on the SET duty-cycle established in this final rule is 
numerically equivalent to the current FTP standard of 14.4 g/hp-hr.
2. Other Provisions for Spark-Ignition HDE
    This Section III.D.2 describes other provisions we proposed and are 
finalizing with revisions from proposal in this rule. The following 
three provisions address information manufacturers will share with EPA 
as part of their certification and we are adding clarification where 
needed after considering comments. See also section 3 of the Response 
to Comments for a detailed discussion of the comments summarized in 
this section and how they have informed the updates we are finalizing 
for these three provisions.
Idle Control for Spark-Ignition HDE
    We proposed to add a new paragraph at 40 CFR 1036.115(j)(1) to 
require manufacturers to show how they maintain a catalyst bed 
temperature of 350 [deg]C in their application for certification or get 
approval for an alternative strategy that maintains low emissions 
during idle. As described in Chapter 3.2 of the RIA, prolonged idling 
events may allow the catalyst to cool and reduce its efficiency, 
resulting in emission increases until the catalyst temperatures 
increase. Our recent HD SI test program showed idle events that extend 
beyond four minutes allow the catalyst to cool below the light-off 
temperature of 350 [deg]C. The current heavy-duty SET and FTP duty 
cycles do not include sufficiently long idle periods to represent these 
real-world conditions where the exhaust system cools below the 
catalyst's light-off temperature.
    We continue to believe that a 350 [deg]C lower bound for catalysts 
will sufficiently ensure emission control is maintained during idle 
without additional manufacturer testing. We are finalizing the 350 
[deg]C target and the option for manufacturers to request approval for 
a different strategy, as proposed. We are revising the final 
requirement from our proposal to also allow manufacturers to request 
approval of a temperature lower than 350 [deg]C, after considering 
comments that requested that we replace the 350 [deg]C temperature with 
the more generic ``light-off temperature'' to account for catalysts 
with other formulations or locations relative to the engine.
i. Thermal Protection Temperature Modeling Validation
    The existing regulations require manufacturers to report any 
catalyst protection strategy that reduces the effectiveness of emission 
controls as an AECD in their application for certification.\312\ The 
engine controls used to implement these strategies often rely on a 
modeling algorithm to predict high exhaust temperatures and to disable 
the catalyst, which can change the emission control strategy and 
directly impact real world emissions. The accuracy of these models used 
by manufacturers is critical in both ensuring the durability of the 
emission control equipment and preventing excessive emissions that 
could result from unnecessary or premature activation of thermal 
protection strategies.
---------------------------------------------------------------------------

    \312\ See 40 CFR 86.094-21(b)(1)(i) and our migration of those 
provisions to final 40 CFR 1036.205(b).
---------------------------------------------------------------------------

    To ensure that a manufacturer's model accurately estimates the 
temperatures at which thermal protection modes are engaged, we proposed 
a validation process during certification in a new paragraph 40 CFR 
1036.115(j)(2) to demonstrate the model performance.
    Several commenters opposed the proposed requirement that 
manufacturers demonstrate a 5 [deg]C accuracy between modelled and 
actual exhaust and emission component temperatures and expressed 
concern with the ability to prove correlation at this level and lack of 
details on the procedure for measuring the temperatures. Our final, 
revised approach still ensures EPA has the information needed to 
appropriately assess a manufacturer's AECD strategy, without a specific 
accuracy requirement.
    Our final 40 CFR 1036.115(j)(2) clarifies that the new validation 
process is a requirement in addition to the requirements for any SI 
engine applications for certification that include an AECD for thermal 
protection.\313\ Instead of the proposed 5 [deg]C accuracy requirement, 
a manufacturer will describe why they rely on any AECDs, instead of 
other engine designs, for thermal protection of catalyst or other 
emission-related components. They will also describe the accuracy of 
any modeled or measured temperatures used to activate the AECD. Instead 
of requiring manufacturers to submit second-by-second data upfront in 
the application for certification to demonstrate a specific accuracy 
requirement is met, the final requirement gives EPA discretion to 
request the information at certification. We note that our final 
revised requirements apply the same validation process for modeled and 
measured temperatures that activate an AECD and that this requirement 
would not apply if manufacturers certify their engines without an AECD 
for enrichment as thermal protection.
---------------------------------------------------------------------------

    \313\ These requirements are in place today under existing 40 
CFR 86.094-21(b)(1)(i), which have been migrated to 40 CFR 
1036.205(b) in this final rule.
---------------------------------------------------------------------------

ii. OBD Flexibilities
    In recognition that there can be some significant overlap in the 
technologies and emission control systems adopted for products in the 
chassis-certified and engine-certified markets, we proposed an OBD 
flexibility to limit the data requirements for engine-certified 
products that use the same engines and generally share similar emission 
controls (i.e., are ``sister vehicles'') with chassis-certified 
products. Specifically, in a new 40 CFR 1036.110(a)(2), we proposed to 
allow vehicle manufacturers the option to request approval to certify 
the OBD of their SI, engine-certified products using data from similar 
chassis-certified Class 2b and Class 3 vehicles that meet the 
provisions of 40 CFR 86.1806-17.
    Two organizations commented in support of the proposed OBD 
flexibility and with one suggesting some revisions to the proposed 
regulatory language. The commenter suggested that the expression `share 
essential design characteristics' was too vague, and requested EPA 
provide more specific information on what EPA will use to make their 
determination. We disagree that more specific information is needed. We 
are relying on the manufacturers to identify the design characteristics 
and justify their request as part of the certification process. We are 
adjusting the final regulatory text to clarify how the vehicles above 
and below 14,000 lbs GVWR must use the same engine and share similar 
emission controls, but are otherwise finalizing this OBD flexibility as 
proposed.

E. Summary of Spark-Ignition HDV Refueling Emission Standards and Test 
Procedures

    All sizes of complete and incomplete heavy-duty vehicles have been 
subject to evaporative emission standards for many years. Similarly, 
all sizes of complete heavy-duty vehicles are subject to refueling 
standards. We most

[[Page 4358]]

recently applied the refueling standards to complete heavy-duty 
vehicles above 14,000 pounds GVWR starting with model year 2022 (81 FR 
74048, Oct. 25, 2016).
    We proposed to amend 40 CFR 1037.103 to apply the same refueling 
standard of 0.20 grams hydrocarbon per gallon of dispensed fuel to 
incomplete heavy-duty vehicles above 14,000 pounds GVWR starting with 
model year 2027 over a useful life of 150,000 miles or 15 years 
(whichever comes first). We further proposed to apply the same testing 
and certification procedures that currently apply for complete heavy-
duty vehicles. We are adopting this standard and testing and 
certification procedures as proposed, with some changes to the proposed 
rule as noted in this section. As noted in 40 CFR 1037.103(a)(2), the 
standards apply for vehicles that run on gasoline, other volatile 
liquid fuels, and gaseous fuels.
    The proposed rule provided an extensive discussion of the history 
of evaporative and refueling standards for heavy-duty vehicles, along 
with rationale and information supporting the proposed standards (87 FR 
17489, March 28, 2022). The RIA includes additional information related 
to control technology, feasibility, and test procedures. See also 
section 3 of the Response to Comments for a detailed discussion of the 
comments and the changes we made to the proposed rule.
    Some commenters advocated for applying the refueling standards also 
to incomplete heavy-duty vehicles at or below 14,000 pounds GVWR. 
Specifically, some manufacturers commented that they would need a 
phase-in schedule that allowed more lead time beyond the proposed MY 
2027 start of the refueling standards for incomplete vehicles above 
14,000 pounds GVWR, and that EPA should consider a longer phase-in that 
also included refueling standards for incomplete vehicles at or below 
14,000 pounds GVWR. In EPA's judgment, the design challenge for meeting 
the new refueling standards will mainly involve larger evaporative 
canisters, resizing purge valves, and recalibrating for higher flow of 
vapors from the evaporative canister into the engine's intake. Four 
years of lead time is adequate for designing, certifying, and 
implementing these design solutions. We are therefore finalizing the 
proposed start of refueling standards in MY 2027 for all incomplete 
heavy-duty vehicles above 14,000 pounds GVWR.
    At the same time, as manufacturers suggested, expanding the scope 
of certification over a longer time frame may be advantageous for 
implementing design changes across their product line in addition to 
the environmental gain from applying refueling controls to a greater 
number of vehicles. We did not propose refueling standards for vehicles 
at or below 14,000 pounds GVWR and we therefore do not adopt such 
standards in this final rule. However, the manufacturers' suggestion to 
consider a package of changes to both expand the scope of the standards 
and increase the lead time for meeting standards has led us to adopt an 
optional alternative phase-in. Under the alternative phase-in 
compliance pathway, instead of certifying all vehicles above 14,000 
pounds GVWR to the refueling standard in MY 2027, manufacturers can opt 
into the alternate phase-in that applies for all incomplete heavy-duty 
vehicles, regardless of GVWR. The alternative phase-in starts at 40 
percent of production in MYs 2026 and 2027, followed by 80 percent of 
production in MYs 2028 and 2029, ramping up to 100 percent of 
production in MY 2030. Phase-in calculations are based on projected 
nationwide production volume of all incomplete heavy-duty vehicles 
subject to refueling emission standards under 40 CFR 86.1813-17. 
Specifying the phase-in schedule in two-year increments allows 
manufacturers greater flexibility for integrating emission controls 
across their product line.
    Manufacturers may choose either schedule of standards; however, 
they must satisfy at least one of the two. That is, if manufacturers do 
not certify all their incomplete heavy-duty vehicles above 14,000 
pounds GVWR to the refueling standards in MY 2027, the alternate phase-
in schedule described in 40 CFR 86.1813-17(b) becomes mandatory to 
avoid noncompliance. Conversely, if manufacturers do not meet the 
alternative phase-in requirement for MY 2026, they must certify all 
their incomplete heavy-duty vehicles above 14,000 pounds GVWR to the 
refueling standard in MY 2027 to avoid noncompliance. See the final 40 
CFR 86.1813-17(b) for the detailed specifications for the alternative 
phase-in schedule.
    We received several comments suggesting that we adjust various 
aspects of the testing and certification procedures for heavy-duty 
vehicles meeting the evaporative and refueling standards. Consideration 
of these comments led us to include some changes from proposal for the 
final rule. First, we are revising 40 CFR 1037.103 to add a reference 
to the provisions from 40 CFR part 86, subpart S, that are related to 
the refueling standards. This is intended to make clear that the 
overall certification protocol from 40 CFR part 86, subpart S, applies 
for heavy-duty vehicles above 14,000 pounds GVWR (see also existing 40 
CFR 1037.201(h)). This applies, for example, for durability procedures, 
useful life, and information requirements for certifying vehicles. 
Along those lines, we are adding provisions to 40 CFR 86.1821-01 to 
clarify how manufacturers need to separately certify vehicles above 
14,000 pounds GVWR by dividing them into different families even if 
they have the same design characteristics as smaller vehicles. This is 
consistent with the way we have been certifying vehicles to evaporative 
and refueling standards.
    Second, we are modifying the test procedures for vehicles with fuel 
tank capacity above 50 gallons. These vehicles have very large 
quantities of vapor generation and correspondingly large evaporative 
and refueling canisters. The evaporative test procedures call for 
manufacturers to design their vehicles to purge a canister over about 
11 miles of driving (a single FTP duty cycle) before the diurnal test, 
which requires the vehicle to control the vapors generated over two 
simulated hot summer days of parking. We share manufacturers' concern 
that the operating characteristics of these engines and vehicles do not 
support achieving that level of emission control. We are therefore 
revising the two-day diurnal test procedure at 40 CFR 86.137-94(b)(24) 
and the Bleed Emission Test Procedure at 40 CFR 86.1813-17(a)(2)(iii) 
to include a second FTP duty cycle with an additional 11 miles of 
driving before starting the diurnal measurement procedure.
    Third, manufacturers pointed out that the existing test procedures 
don't adequately describe how to perform a refueling emission 
measurement with vehicles that have two fuel tanks with separate filler 
necks. We are amending the final rule to include a provision to direct 
manufacturers to use good engineering judgment for testing vehicles in 
a dual-tank configuration. It should be straightforward to do the 
testing with successive refills for the two tanks and combining the 
measured values into a single result. Rather than specifying detailed 
adjustments to the procedure, allowing manufacturers the discretion to 
perform that testing and computation consistent with good engineering 
judgment will be enough to ensure a proper outcome.
    Table III-23 summarizes the cost estimations for the different 
technological approaches to controlling refueling emissions that EPA 
evaluated. See Chapter 3.2.3.2 of the RIA for the

[[Page 4359]]

details. In calculating the overall cost, we used $25 (2019 dollars), 
the average of both approaches, to represent the cost for manufacturers 
to adopt the additional canister capacity and hardware to meet our new 
refueling emission standards for incomplete vehicles above 14,000 lb 
GVWR. See also Section V of this preamble for a summary of our overall 
program cost and Chapter 7 of the RIA for more details on our overall 
program cost.

          Table III-23--Summary of Projected Per-Vehicle Costs To Meet the Refueling Emission Standards
----------------------------------------------------------------------------------------------------------------
                                                            Liquid seal                   Mechanical seal
                                                 ---------------------------------------------------------------
                                                                   Dual existing                   Dual existing
                                                   New canister    canisters in    New canister    canisters in
                                                                      series                          series
----------------------------------------------------------------------------------------------------------------
Additional Canister Costs.......................             $20             $15              $8              $8
----------------------------------------------------------------------------------------------------------------
Additional Tooling \a\..........................               0.50
                                                               0.50
----------------------------------------------------------------------------------------------------------------
Flow Control Valves.............................               6.50
                                                               6.50
----------------------------------------------------------------------------------------------------------------
Seal............................................               0               0                10
----------------------------------------------------------------------------------------------------------------
    Total.......................................              27              22                25
----------------------------------------------------------------------------------------------------------------
a Assumes the retooling costs are spread over a five-year period.

    Incomplete vehicles above 14,000 lb GVWR with dual fuel tanks may 
require some unique accommodations to adopt onboard refueling vapor 
recovery (ORVR) systems. A chassis configuration with dual fuel tanks 
would need separate canisters and separate filler pipes and seals for 
each fuel tank. Depending on the design, a dual fuel tank chassis 
configuration may require a separate purge valve for each fuel tank. We 
assume manufacturers will install one additional purge valve for dual 
fuel tank applications that also incorporate independent canisters for 
the second fuel tank/canister configuration, and that manufacturers 
adopting a mechanical seal in their filler pipe will install an anti-
spitback valve for each filler pipe. See Chapter 1.2.4.5 of the RIA for 
a summary of the design considerations for these fuel tank 
configurations. We did not include an estimate of the impact of dual 
fuel tank vehicles in our cost analysis of the new refueling emission 
standards, as the population of these vehicles is very low and we 
expect minimal increase in the total average costs.

IV. Compliance Provisions and Flexibilities

    EPA certification is a fundamental requirement of the Clean Air Act 
for manufacturers of heavy-duty highway engines. EPA has employed 
significant discretion over the past several decades in designing and 
updating many aspects of our heavy-duty engine and vehicle 
certification and compliance programs. In the following sections, we 
discuss several revised provisions that we believe will increase the 
effectiveness of our regulations.
    As noted in Section I, we are migrating our criteria pollutant 
regulations for model years 2027 and later heavy-duty highway engines 
from their current location in 40 CFR part 86, subpart A, to 40 CFR 
part 1036.\314\ Consistent with this migration, the compliance 
provisions discussed in this section refer to the final regulations in 
their new location in part 1036. In general, this migration is not 
intended to change the compliance program specified in part 86, except 
as specifically finalized in this rulemaking. See Section III.A.1.
---------------------------------------------------------------------------

    \314\ As noted in the following sections, we are finalizing some 
updates to 40 CFR parts 1037, 1065, and 1068 to apply to other 
sectors in addition to heavy-duty highway engines.
---------------------------------------------------------------------------

A. Regulatory Useful Life

    Useful life represents the period over which emission standards 
apply for certified engines, and, practically, any difference between 
the regulatory useful life and the generally longer operational life of 
in-use engines represents miles and years of operation without an 
assurance that emission standards will continue to be met. In addition 
to promulgating new emission standards and promulgating new and 
updating existing test procedures described in Section III, we are 
updating regulatory useful life periods to further assure emission 
performance of heavy-duty highway engines. In this section, we present 
the updated regulatory useful life periods we are finalizing in this 
rule. In Section IV.A.1, we present our revised useful life periods 
that will apply for the new exhaust emission standards for criteria 
pollutants, OBD, and requirements related to crankcase emissions. In 
Section IV.A.2, we present the useful life periods that will apply for 
the new refueling emission standards for certain Spark-ignition HDE. As 
described in Section G.10 of this preamble, we are not finalizing the 
proposed allowance for manufacturers to generate NOX 
emissions credits from heavy-duty zero emissions vehicles (ZEVs) or the 
associated useful life requirements.
1. Regulatory Useful Life Periods by Primary Intended Service Class
    In this final rule, we are increasing the regulatory useful life 
mileage values for new heavy-duty engines to better reflect real-world 
usage, extend the emissions durability requirement for heavy-duty 
engines, and improve long-term emission performance. In this Section 
IV.1, we describe the regulatory useful life periods we are finalizing 
for the four primary intended service classes for heavy-duty highway 
engines.\315\ Our longer useful life periods vary by engine class to 
reflect the different lengths of their estimated operational lives. As 
described in the proposal for this rule, we continue to consider 
operational life to be the average mileage at rebuild for CI engines 
and the average mileage at replacement for SI engines.\316\
---------------------------------------------------------------------------

    \315\ The useful life periods we are finalizing in this rule 
apply for criteria pollutant standards; we did not propose and are 
not finalizing changes to the useful life periods that apply for GHG 
standards.
    \316\ See Chapter 2.4 of the RIA for a summary of the history of 
our regulatory useful life provisions and our estimate of the 
operational life for each heavy-duty engine class.
---------------------------------------------------------------------------

    In determining the appropriate longer useful life values to set in 
the final rule, we retain our proposed objective to set useful life 
periods that cover a significant portion of the engine's operational 
life. However, as explained in the proposal, we also maintain that

[[Page 4360]]

the emission standards presented in Section III must be considered 
together with their associated useful life periods. After further 
consideration of the basis for the proposal, comments received, 
supporting data available since the proposal, and the numeric level of 
the final standards, we are selecting final useful life values within 
the range of options proposed that cover a significant portion of the 
engine's operational life and take into account the combined effect of 
useful life and the final numeric standards on the overall stringency 
and emissions reductions of the program. As described in the final RIA, 
we concluded two engine test programs for this rule that demonstrated 
technologies that are capable of meeting lower emission levels at much 
longer mileages than current useful life periods. We evaluated a heavy-
duty diesel engine to a catalyst-aged equivalent of 800,000 miles for 
the compression-ignition demonstration program, and a heavy-duty 
gasoline engine to a catalyst-aged equivalent of 250,000 miles for the 
spark-ignition demonstration program. As described in Section III of 
this preamble, the results of those demonstration programs informed the 
appropriate standard levels for the useful life periods we are 
finalizing for each engine class. Our final useful life values were 
also informed by comments, including additional information on 
uncertainties and potential corresponding costs. We summarize key 
comments in Section IV.1.ii, and provide complete responses to useful 
life comments in section 3.8 of the Response to Comments document.
    Our final useful life periods for Spark-ignition HDE, Light HDE, 
Medium HDE, and Heavy HDE classes are presented in Table IV-1 and 
specified in a new 40 CFR 1036.104(e).\317\ The final useful life 
values that apply for Spark-ignition HDE, Light HDE, and Medium HDE 
starting in MY 2027 match the most stringent option we proposed, that 
is, MY 2031 step of proposed Option 1. The final useful life values for 
Heavy HDE, which has a distinctly longer operational life than the 
smaller engine classes, match the longest useful life mileage we 
proposed for model year 2027 (i.e., the Heavy HDE mileage of proposed 
Option 2). We are also increasing the years-based useful life from the 
current 10 years to values that vary by engine class and match the 
proposed value in the respective proposed option. After considering 
comments, we are also adding hours-based useful life values to all 
primary intended service classes based on a 20 mile per hour speed 
threshold and the corresponding final mileage values.
---------------------------------------------------------------------------

    \317\ We are migrating the current alternate standards for 
engines used in certain specialty vehicles from 40 CFR 86.007-11 and 
86.008-10 into 40 CFR 1036.605 without modification. See Section 
XI.B of this preamble for a discussion of these standards.

                                         Table IV-1--Final Useful Life Periods by Primary Intended Service Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Current                                    MY 2027 and later
             Primary intended service class              -----------------------------------------------------------------------------------------------
                                                               Miles           Years           Hours           Miles           Years           Hours
--------------------------------------------------------------------------------------------------------------------------------------------------------
Spark-ignition HDE \a\..................................         110,000              10  ..............         200,000              15          10,000
Light HDE \a\...........................................         110,000              10  ..............         270,000              15          13,000
Medium HDE..............................................         185,000              10  ..............         350,000              12          17,000
Heavy HDE...............................................         435,000              10          22,000         650,000              11          32,000
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Current useful life period for Spark-ignition HDE and Light HDE for GHG emission standards is 15 years or 150,000 miles; we are not revising these
  useful life periods in this final rule. See 40 CFR 1036.108(d).

    For hybrid engines and powertrains, we are finalizing the proposal 
that manufacturers certifying hybrid engines and powertrains would 
declare the primary intended service class of their engine family using 
40 CFR 1036.140. Once a primary intended service class is declared, the 
engine configuration would be subject to the corresponding emission 
standards and useful life values from 40 CFR 1036.104.
i. Summary of the Useful Life Proposal
    For CI engines, the proposed Option 1 useful life periods included 
two steps in MYs 2027 and 2031 that aligned with the final useful life 
periods of CARB's HD Omnibus regulation, and the proposed MY 2031 
periods covered close to 80 percent of the expected operational life of 
CI engines based on mileage at out-of-frame rebuild. The useful life 
mileages of proposed Option 2, which was a single-step option starting 
in MY 2027, generally corresponded to the average mileages at which CI 
engines undergo the first in-frame rebuild. The rebuild data indicated 
that CI engines can last well beyond the in-frame rebuild mileages. We 
noted in the proposal that it was unlikely that we would finalize a 
single step program with useful life mileages shorter than proposed 
Option 2; instead, we signaled that we would likely adjust the numeric 
value of the standards to address any feasibility concerns.
    For Spark-ignition HDE, the useful life mileage in proposed Option 
1 was about 90 percent of the operational life of SI engines based on 
mileage at replacement. The useful life of proposed Option 2 aligned 
with the current SI engine useful life mileage that applies for GHG 
standards. In the proposal, we noted that proposed Option 2 also 
represented the lowest useful life mileage we would consider finalizing 
for Spark-ignition HDE.
    In proposed Option 1, we increased the years-based useful life 
values for all engine classes to account for engines that accumulate 
fewer miles annually. We also proposed to update the hours-based useful 
life criteria for the Heavy HDE class to account for engines that 
operated frequently, but accumulated relatively few miles due to lower 
vehicle speeds. We calculated the proposed hours values by applying the 
same 20 mile per hour conversion factor to the proposed mileages as was 
applied when calculating the useful life hours that currently apply for 
Heavy HDE.\318\ The proposed hours specification was limited to the 
Heavy HDE class to be consistent with current regulations, but we 
requested comment on adding hours-based useful life values to apply for 
the other service classes.
---------------------------------------------------------------------------

    \318\ U.S. EPA, ``Summary and Analysis of Comments: Control of 
Emissions of Air Pollution from Highway Heavy-Duty Engines'', EPA-
420-R-97-102, September 1997, pp 43-47.
---------------------------------------------------------------------------

ii. Basis for the Final Useful Life Periods
    In this Section IV.1.ii, we provide the rationale for our final 
useful life periods, including summaries and responses to certain 
comments that informed our final program. The complete set of useful 
life comments

[[Page 4361]]

and our responses are in section 3.8 of the Response to Comments 
document. As explained in the NPRM, CAA section 202(d) provides that 
the minimum useful life for heavy-duty vehicles and engines is a period 
of 10 years or 100,000 miles, whichever occurs first, and further 
authorizes EPA to adopt longer useful life periods that we determine to 
be appropriate.
    Many commenters expressed general support for our proposal to 
lengthen useful life periods in this rulemaking. Several commenters 
expressed specific support for the useful life periods of proposed 
Option 1 or proposed Option 2. Other commenters recommended EPA revise 
the proposal to either lengthen or shorten the useful life periods to 
values outside of the range of our proposed options.
    We are lengthening the current useful life mileages to capture the 
greatest amount of the operational life for each engine class that we 
have determined is appropriate at this time. We disagree with 
commenters recommending that we finalize useful life periods below the 
mileages of proposed Option 2. As noted in our proposal, proposed 
Option 2 represented the lower bound of useful life mileages we would 
consider finalizing for all engine classes. Furthermore, as described 
in Section III of this preamble and Chapter 3 of the RIA for this final 
rule, both of EPA's engine test programs successfully demonstrated that 
CI and SI engine technologies can achieve low emission levels at 
mileages (800,000 miles and 250,000 miles, respectively) well beyond 
Option 2. Even after taking into consideration uncertainties of the 
impacts of variability and real world operation on emission levels at 
the longest mileages, the test programs' data supports that mileages at 
least as long as Option 2 are appropriate, and the final standards are 
feasible at those mileages. We also disagree with commenters suggesting 
we finalize mileages longer than proposed Option 1. We did not propose 
and for the reasons just explained about impacts on emission level at 
the longest mileages do not believe it is appropriate at this time to 
require useful life periods beyond proposed Option 1.
    Organizations submitting adverse comments on useful life focused 
mostly on the useful life mileages proposed for the Heavy HDE service 
class. Technology suppliers and engine manufacturers expressed concern 
with the lack of data from engines at mileages well beyond the current 
useful life. Suppliers commented that it could be costly and 
challenging to design components without more information on component 
durability, failure modes, and use patterns at high mileages. Engine 
manufacturers claimed that some uncertainties relating to real world 
use would limit the feasibility of the proposed Option 1 useful life 
periods, including: The range of applications in which these engines 
are used, variable operator behavior (including 2nd and 3rd owners), 
and the use of new technology that is currently unproven in the field. 
In Sections III and IV.F of this preamble, we describe other areas 
where useful life plays a role and manufacturers expressed concern over 
uncertainties, including certification, DF testing, engine rating 
differences, lab-to-lab variability, production variability, and in-use 
engine variability. Due to these combined uncertainties, manufacturers 
stated that they expect to be conservative in their design and 
maintenance strategies, and some may opt to schedule aftertreatment 
replacement as a means to ensure compliance with new NOX 
emission standards, particularly for proposed Option 1 numeric 
standards and useful life values. Comments did not indicate a concern 
that manufacturers may schedule aftertreatment replacement for the 
smaller engine classes at the proposed Option 1 useful life periods.
    We agree that there are uncertainties associated with implementing 
new technology to meet new emission standards, and recognize that the 
uncertainties are highest for Heavy HDE that are expected to have the 
longest operational life and useful life periods. We acknowledge that 
higher useful life mileage is one factor that may contribute to a risk 
that manufacturers would schedule aftertreatment replacement to ensure 
compliance for the heaviest engine class. Specific to Heavy HDE, the 
final useful life mileage of 650,000 miles matches the longest useful 
life mileage we proposed for model year 2027 and we expect 
manufacturers have experience with their engines at this mileage 
through their extended warranty offerings, thus reducing uncertainties 
of real world operation compared to the longest useful life mileage we 
proposed (i.e., 800,000 miles).\319\ For Heavy HDE, the final numeric 
emission standards and useful life periods matching proposed Option 2, 
combined with other test procedure revisions to provide clarity and 
address variability, will require less conservative compliance 
strategies than proposed Option 1 and will not require manufacturers to 
plan for the replacement of the entire catalyst system. See Section III 
for further discussion on the basis and feasibility of the final 
emission standards.
---------------------------------------------------------------------------

    \319\ Brakora, Jessica. Memorandum to docket EPA-HQ-OAR-2019-
0055. ``Example Extended Warranty Packages for Heavy-duty Engines''. 
September 29, 2022.
---------------------------------------------------------------------------

    Many commenters supported proposed Option 1, including useful life 
periods out to 800,000 miles for the Heavy HDE class. Several 
commenters pointed to EPA's engine testing results on an engine aged to 
the equivalent of 800,000 miles as adequately demonstrating feasibility 
of an 800,000-mile useful life for Heavy HDE. We agree that CI engines 
are capable of meeting low emission levels at very high mileages in a 
controlled laboratory environment, but manufacturer liability for 
maintaining certified emission levels over the regulatory useful life 
period is not restricted to laboratory tests. Manufacturers expressed 
specific concern about the uncertainties outside the controlled 
laboratory environment after an engine enters commerce. In Sections III 
and IV.F of this preamble we summarize comments relating to how useful 
life factors into certification, DF testing, and in-use testing. In 
Section III.B, we describe a certification requirement we are 
finalizing for manufacturers to demonstrate the emission controls on 
Heavy HDE are durable through the equivalent of 750,000 miles; this 
durability demonstration will extend beyond the 650,000 mile useful 
life period for these engines. We expect this extended laboratory-based 
demonstration, in a controlled environment, will translate to greater 
assurance that an engine will maintain its certified emission levels in 
real world operation where conditions are more variable throughout the 
regulatory useful life. This greater assurance would be achieved while 
minimizing the compliance uncertainties identified by manufacturers in 
comments for the highest proposed useful life mileages.
    We believe manufacturers can adequately ensure the durability of 
their smaller engines over useful life periods that match proposed 
Option 1 both for meeting emission standards in the laboratory at 
certification and in the laboratory and applicable in-use testing after 
operation in the real world. The final durability demonstration 
requirements for Spark-ignition HDE, Light HDE, and Medium HDE match 
the final useful life periods for those smaller engines classes.
    As shown in Table IV-1, we are also finalizing useful life periods 
in years and hours for all primary intended service classes. We are 
updating the years values from the current 10 years to 15 years for 
Spark-ignition HDE and

[[Page 4362]]

Light HDE, 12 years for Medium HDE, and 11 years for Heavy HDE. The 
final years values match the years values we proposed and vary by 
engine class corresponding to the proposed mileage option we are 
finalizing. We are also adding hours as a useful life criteria for all 
engine classes. We received no adverse comments for hours-based useful 
life periods and are finalizing hours values by applying a 20-mph 
conversion factor, as proposed, to calculate hours values from the 
final mileage values.
    We have finalized a combination of emissions standards and useful 
life values that our analysis and supporting data demonstrate are 
feasible for all heavy-duty engine classes. We are lengthening the 
existing useful life mileages to capture the greatest amount of the 
operational life for each engine class that we have determined is 
appropriate at this time, while considering the impact of useful life 
length on the stringency of the standards and other requirements of 
this final rule. Preamble Section III describes how our analysis and 
the EPA engine test programs demonstrated feasibility of the standards 
at these useful life values, including data on emission levels at the 
equivalent useful life mileages.
2. Useful Life for Incomplete Vehicle Refueling Emission Standards
    As described in Section III.E., we are finalizing a refueling 
emission standard for incomplete vehicles above 14,000 lb GVWR. 
Manufacturers would meet the refueling emission standard by installing 
onboard refueling vapor recovery (ORVR) systems on these incomplete 
vehicles. Since ORVR systems are based on the same carbon canister 
technology that manufacturers currently use to control evaporative 
emissions on these incomplete vehicles, we proposed to align the useful 
life periods for the two systems. In 40 CFR 1037.103(f), we are 
finalizing a useful life of 15 years or 150,000 miles, whichever comes 
first, for refueling standards for incomplete vehicles above 14,000 lb 
GVWR, as proposed.
    Evaporative emission control systems are currently part of the fuel 
system of incomplete vehicles, and manufacturers are meeting applicable 
standards and useful life requirements for evaporative systems today. 
ORVR is a mature technology that has been installed on complete 
vehicles for many years, and incomplete vehicle manufacturers have 
experience with ORVR systems through their complete vehicle 
applications. Considering the manufacturers' experience with 
evaporative emission standards for incomplete vehicles, and their 
familiarity with ORVR systems, we continue to believe it would be 
feasible for manufacturers to apply the same evaporative emission 
standard useful life periods to refueling standards. We received no 
adverse comments relating to the proposed 15 years/150,000 miles useful 
life for refueling standards, and several manufacturers commented in 
support of our proposed periods.

B. Ensuring Long-Term In-Use Emissions Performance

    In the proposal, we introduced several ideas for an enhanced, 
comprehensive strategy to ensure in-use emissions performance over more 
of an engine's operational life. In this section, we discuss the final 
provisions to lengthen emission-related warranty periods, update 
maintenance requirements, and improve serviceability in this rule. 
Taken together, these updates are intended to increase the likelihood 
that engine emission controls will be maintained properly through more 
of the service life of heavy-duty engines and vehicles, including 
beyond useful life.
1. Emission-Related Warranty
    The emission-related warranty period is the period over which CAA 
section 207 requires an engine manufacturer to warrant to a purchaser 
that the engine is designed, built, and equipped so as to conform with 
applicable regulations under CAA section 202 and is free from defects 
in materials or workmanship which would cause the engine not to conform 
with applicable regulations for the warranty period. If an emission-
related component fails during the regulatory emission warranty period, 
the manufacturer is required to pay for the cost of repair or 
replacement. A manufacturer's general emissions warranty 
responsibilities are currently set out in 40 CFR 1068.115. Note that 
while an emission warranty provides protection to the owner against 
emission-related repair costs during the warranty period, the owner is 
responsible for properly maintaining the engine (40 CFR 1068.110(e)), 
and the manufacturer may deny warranty claims for failures that have 
been caused by the owner's or operator's improper maintenance or use 
(40 CFR 1068.115(a)).
    In this section, we present the updated emission-related warranty 
periods we are finalizing for heavy-duty highway engines and vehicles 
included in this rule. As described in Section G.10 of this preamble, 
we are not finalizing the proposed allowance for manufacturers to 
generate NOX emissions credits from heavy-duty zero 
emissions vehicles (ZEVs) or the associated warranty requirements.
i. Final Warranty Periods by Primary Intended Service Class
    We are updating and significantly strengthening our emission-
related warranty periods for model year 2027 and later heavy-duty 
engines.\320\ We are finalizing most of the emission-related warranty 
provisions of 40 CFR 1036.120 as proposed. Following our approach for 
useful life, we are revising the proposed warranty periods for each 
primary intended service class to reflect the difference in average 
operational life of each class and after considering additional 
information provided by commenters. See section 4 of the Response to 
Comments document for our detailed responses, including descriptions of 
revisions to the proposed regulatory text in response to commenter 
requests for clarification.
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    \320\ Emission-related components for only criteria pollutant 
emissions or both greenhouse gas (i.e., CO2, N2O, and CH4) and 
criteria pollutant emissions would be subject to the final warranty 
periods of 40 CFR 1036.120. See 40 CFR 1036.150(w).
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    EPA's current emissions-related warranty periods for heavy-duty 
engines range from 22 percent to 54 percent of the current regulatory 
useful life; the warranty periods have not changed since 1983 even as 
the useful life periods were lengthened.\321\ The revised warranty 
periods are expected to result in better engine maintenance and less 
tampering, which would help to maintain the benefits of the emission 
controls. In addition, longer regulatory warranty periods may lead 
engine manufacturers to simplify repair processes and make them more 
aware of system defects that need to be tracked and reported to EPA.
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    \321\ The useful life for heavy heavy-duty engines was increased 
from 290,000 miles to 435,000 miles for 2004 and later model years 
(62 FR 54694, October 21, 1997).
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    Our final emission-related warranty periods for heavy-duty engines 
are presented in Table IV-2 and specified in a new 40 CFR 
1036.120.322 323 The final warranty mileages that apply 
starting in MY 2027 for Spark-ignition HDE, Light HDE, and Medium HDE 
match the longest warranty mileages proposed (i.e., MY 2031 step of 
proposed Option 1) for these primary intended service

[[Page 4363]]

classes. For Heavy HDE, the final warranty mileage matches the longest 
warranty mileage proposed for MY 2027 (i.e., MY 2027 step of proposed 
Option 1). We are also increasing the years-based warranty from the 
current 5 years to 10 years for all engine classes. After considering 
comments, we are also adding hours-based warranty values to all primary 
intended service classes based on a 20 mile per hour speed threshold 
and the corresponding final mileage values. Consistent with current 
warranty provisions, the warranty period would be whichever warranty 
value (i.e., mileage, hours, or years) occurs first. We summarize key 
comments in Section IV.B.1.i.a, and provide complete responses to 
warranty comments in section 4 of the Response to Comments document.
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    \322\ All engines covered by a primary intended service class 
would be subject to the corresponding warranty period, regardless of 
fuel used.
    \323\ We are migrating the current alternate standards for 
engines used in certain specialty vehicles from 40 CFR 86.007-11 and 
86.008-10 into 40 CFR 1036.605 without modifying those alternate 
standards, as proposed. See Section XI.B of this preamble for a 
discussion of these standards.

                                  Table IV-2--Final Emission-Related Warranty Periods by Primary Intended Service Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                              Current                                Model year 2027 and later
             Primary intended service class              -----------------------------------------------------------------------------------------------
                                                              Mileage          Years           Hours          Mileage          Years           Hours
--------------------------------------------------------------------------------------------------------------------------------------------------------
Spark-Ignition HDE......................................          50,000               5  ..............         160,000              10           8,000
Light HDE...............................................          50,000               5  ..............         210,000              10          10,000
Medium HDE..............................................         100,000               5  ..............         280,000              10          14,000
Heavy HDE...............................................         100,000               5  ..............         450,000              10          22,000
--------------------------------------------------------------------------------------------------------------------------------------------------------

    We note that we are finalizing as proposed that when a 
manufacturer's certified configuration includes hybrid system 
components (e.g., batteries, electric motors, and inverters), those 
components are considered emission-related components, which would be 
covered under the warranty requirements in new 40 CFR 1036.120.\324\ 
Similar to the approach for useful life in Section IV.A, a manufacturer 
certifying a hybrid engine or hybrid powertrain would declare a primary 
intended service class for the engine family and apply the 
corresponding warranty periods in 40 CFR 1036.120 when certifying the 
engine configuration.\325\ This approach to clarify that hybrid 
components are part of the broader engine configuration provides 
vehicle owners and operators with consistent warranty coverage based on 
the intended vehicle application.
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    \324\ See our new definition of ``emission-related component'' 
in 40 CFR 1036.801. Defects or failures of hybrid system components 
can result in the engine operating more, and thus increase 
emissions.
    \325\ As described in 40 CFR 1036.140, the primary intended 
service classes are partially based on the GVWR of the vehicle in 
which the configuration is intended to be used. See also the update 
to definition of ``engine configuration'' in 40 CFR 1036.801 to 
clarify that an engine configuration would include hybrid components 
if it is certified as a hybrid engine or hybrid powertrain.
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    We estimated the emissions impacts of the final warranty periods in 
our inventory analysis, which is summarized in Section VI and discussed 
in detail in Chapter 5 of our RIA. In Section V, we estimate costs 
associated with the final warranty periods, including indirect costs 
for manufacturers and operating costs for owners and operators.
a. Summary of the Emission-Related Warranty Proposal
    In the proposal, we included several justifications for lengthened 
warranty periods that continue to apply for the final provisions. 
First, we expected longer emission-related warranty periods would lead 
owners to continue maintain their engines and vehicles over a longer 
period of time and ensure longer-term benefits of emission 
controls.\326\ Since emission-related repairs would be covered by 
manufacturers for a longer period of time, an owner would be more 
likely to have systems repaired and less likely to tamper to avoid the 
cost of a repair.\327\
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    \326\ See Chapter 5 of the RIA for a discussion of mal-
maintenance and tampering effects in our emission inventory 
estimates.
    \327\ Existing warranty provisions specify that owners are 
responsible for properly maintaining their engines (40 CFR 
1068.110(e)) and manufacturers may deny warranty claims for failures 
that have been caused by the owner's or operator's improper 
maintenance or use (40 CFR 1068.115(a)). See Section IV.B.2 for a 
description of updates to the allowable maintenance provisions.
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    Second, emission-related repair processes may get more attention 
from manufacturers if they are responsible for repairs over a longer 
period of time. The current, relatively short warranty periods provide 
little incentive for manufacturers to evaluate the complexity of their 
repair processes, since the owner pays for the repairs after the 
warranty period ends. As manufacturers try to remain competitive, 
longer emission warranty periods may lead manufacturers to simplify 
repair processes and provide better training to technicians in an 
effort to reduce their warranty repair costs. Simplifying repair 
processes could include modifying emission control components in terms 
of how systems are serviced and how components are replaced (e.g., 
modular sub-assemblies that could be replaced individually, resulting 
in a quicker, less expensive repair). Improved technician training may 
also reduce warranty repair costs by improving identification and 
diagnosing component failures more quickly and accurately, thus 
reducing downtime for owners and avoiding repeated failures, 
misdiagnoses of failures, and higher costs from repeat repair events at 
service facilities.
    Finally, longer regulatory emission warranty periods would increase 
the period over which the engine manufacturer would be made aware of 
emission-related defects. Manufacturers are currently required to track 
and report defects to the Agency under the defect reporting provisions 
of 40 CFR part 1068. Under 40 CFR 1068.501(b), manufacturers 
investigate possible defects whenever a warranty claim is submitted for 
a component. Therefore, manufacturers can easily monitor defect 
information from dealers and repair shops who are performing those 
warranty repair services, but after the warranty period ends, the 
manufacturer would not necessarily know about these events, since 
repair facilities are less likely to be in contact with the 
manufacturers and they are less likely to use OEM parts. A longer 
warranty period would allow manufacturers to have access to better 
defect information over a period of time more consistent with engine 
useful life.
    In the proposal, we also highlighted that a longer warranty period 
would encourage owners of vehicles powered by SI engines (as for CI 
engines) to follow manufacturer-prescribed maintenance procedures for a 
longer period of time, as failure to do so would void the warranty. We 
noted that the impact of a longer emissions warranty period may be 
slightly different for SI engines from a tampering perspective. Spark-
ignition engine systems rely on mature technologies, including 
evaporative emission systems and three-way catalyst-based emission 
controls, that have been consistently reliable for light-duty and 
heavy-duty vehicle

[[Page 4364]]

owners.\328\ SI engine owners may not currently be motivated to tamper 
with their catalyst systems to avoid repairs, but they may purchase 
defeat devices intended to disable emission controls to boost the 
performance of their engines. We expected SI engine owners may be less 
inclined to install such defeat devices during a longer warranty 
period.
---------------------------------------------------------------------------

    \328\ The last U.S. EPA enforcement action against a 
manufacturer for three-way catalysts was settled with 
DaimlerChrylser Corporation Settlement on December 21, 2005. 
Available online: https://www.epa.gov/enforcement/daimlerchrysler-corporation-settlement.
---------------------------------------------------------------------------

    We proposed two options that generally represented the range of 
revised emission warranty periods we considered adopting in the final 
rule. Proposed Option 1 included warranty periods that aligned with the 
MY 2027 and MY 2031 periods of the CARB HD Omnibus program and were 
close to 80 percent of useful life. At the time of the proposal, we 
assumed most manufacturers would continue to certify 50-state compliant 
engines in MY 2027 and later, and it would simplify the certification 
process if there would be consistency between CARB and Federal 
requirements. The warranty periods of proposed Option 2 were proposed 
to apply in a single step beginning in model year 2027 and to match 
CARB's Step 1 warranty periods for engines sold in California.\329\ The 
proposed Option 2 mileages covered 40 to 55 percent of the proposed 
Option 1 MY 2031 useful life mileages and represented an appropriate 
lower end of the range of the revised regulatory emission warranty 
periods we considered.
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    \329\ Since the CARB Step 1 warranty program did not include 
updates to warranty for SI engines, the proposed Option 2 warranty 
mileage for that the Spark-ignition HDE class matched the current 
useful life for those engines, consistent with the approach for 
Light HDE proposed Option 2 warranty.
---------------------------------------------------------------------------

    While we noted that a majority of engines would reach the warranty 
mileage in a reasonable amount of time, some applications may have very 
low annual mileage due to infrequent use or low speed operation and may 
not reach the warranty mileage for many years. To ensure manufacturers 
are not indefinitely responsible for components covered under emissions 
warranty in these situations, we proposed to revise the years-based 
warranty periods and proposed hours-based warranty periods for all 
engine classes in proposed Option 1.
    For the years-based period, which would likely be reached first by 
engines with lower annual mileage due to infrequent use, we proposed to 
increase the current period from 5 years to 7 years for MY 2027 through 
2030, and to 10 years starting with MY 2031. We also proposed to add an 
hours-based warranty period to cover engines that operate at low speed 
and/or are frequently in idle mode.\330\ In contrast to infrequent use, 
low speed and frequent idle operation can strain emission control 
components. We proposed an hours-based warranty period to allow 
manufacturers to factor gradually-accumulated work into their warranty 
obligations.
---------------------------------------------------------------------------

    \330\ We proposed warranty hours for all primary intended 
service classes based on a 20 mile per hour average vehicle speed 
threshold to convert from the proposed mileage values.
---------------------------------------------------------------------------

b. Basis for the Final Emission-Related Warranty Periods
    As detailed in section 4 of the Response to Comments document for 
this rule, commenter support for lengthening emission-related warranty 
periods varied. Many commenters expressed general support for our 
proposal to lengthen warranty periods in this rulemaking. Several 
commenters expressed specific support for the warranty periods of 
proposed Option 1 or proposed Option 2. Other commenters recommended 
EPA revise the proposal to either lengthen or shorten the warranty 
periods to values outside of the range of our proposed options.
    Our final warranty periods continue to be influenced by the 
potential beneficial outcomes of lengthening emission-related warranty 
periods that we discussed in the proposal. Specifically, we continue to 
believe lengthened warranty periods will effectively assure owners 
properly maintain and repair their emission controls over a longer 
period, reduce the likelihood of tampering, provide additional 
information on failure modes, and create a greater incentive for 
manufacturers to simplify repair processes to reduce costs. Several 
commenters agreed with our list of potential outcomes, with some noting 
that any associated emissions benefits would be accelerated by pulling 
ahead the warranty periods of the MY 2031 step of proposed Option 1 to 
begin in MY 2027.
    Organizations submitting adverse comments on lengthening warranty 
periods focused mostly the warranty mileages proposed for the Heavy HDE 
service class. Technology suppliers and engine manufacturers expressed 
concern with the lack of data from engines at high mileages, including 
uncertainties related to frequency and cause of failures, varying 
vehicle applications, and operational changes as the engine ages. We 
considered commenters' concerns regarding how uncertainties for the 
highest mileages of proposed Option 1 could cause manufacturers to 
respond by conservatively estimating their warranty cost. We continue 
to expect, as noted in the proposal, that manufacturers are likely to 
recoup the costs of warranty by increasing the purchase price of their 
products. We agree with comments indicating that increases in purchase 
price can increase the risk of pre-buy or low-buy, especially for the 
heaviest engine class, Heavy HDE.
    As described in this section, the final warranty periods are within 
the range of periods over which we expect manufacturers have access to 
failure data, which should limit the need for manufacturers to 
conservatively estimate warranty costs. We summarize our updated cost 
and economic impact analyses, which reflect the final warranty periods, 
in Sections V and X of this preamble, respectively. For more 
information, see our complete assessments of costs in Chapter 7 and 
economic impacts in Chapter 10 of the Regulatory Impact Analysis for 
this final rule.
    We retain our proposed objectives to lengthen warranty periods to 
cover a larger portion of the operational lives and to be more 
consistent with the final useful life periods. Similar to our approach 
for the useful life mileages in this final rule (see Section IV.A of 
this preamble), we believe it is appropriate to pull ahead the longest 
proposed MY 2031 warranty periods to apply in MY 2027 for the smaller 
engine classes. For Spark-ignition HDE, Light HDE, and Medium HDE, the 
final warranty mileages are 160,000 miles, 210,000 miles, and 280,000 
miles, respectively, which cover about 80 percent of the corresponding 
final useful life mileages. In response to commenters concerned with 
data limitations, we expect any component failure and wear data 
available from engines in the largest engine class would be applicable 
to the smaller engine classes. As such, manufacturers and suppliers 
have access to failure and wear data at the mileages we are finalizing 
for the smaller engine classes through their current R&D and in-use 
programs evaluating components for larger engines that currently have a 
435,000 mile useful life.
    We are not applying the same pull-ahead approach for the Heavy HDE 
warranty mileage. We do not believe it is appropriate at this time to 
finalize a 600,000-mile warranty for the Heavy HDE class that would 
uniquely cover greater than 90 percent of the 650,000-

[[Page 4365]]

mile final useful life, especially considering the comments pointing to 
uncertainties, lack of data, and potential high costs specific to Heavy 
HDE. We are also not applying the approach of adopting the warranty 
mileage of proposed Option 2, as was done for Heavy HDE useful life, as 
we do not believe the proposed Option 2 warranty of 350,000 miles would 
provide emission control assurance over a sufficient portion of the 
useful life. Instead, we are finalizing a warranty mileage that matches 
the longest mileage proposed for MY 2027 (450,000 miles), covering a 
percentage of the final useful life that is more consistent with the 
warranty periods of the smaller engine classes. The final warranty 
mileage for Heavy HDE is only 15,000 miles longer than the current 
useful life for this engine class. As noted for the warranties of the 
smaller engine classes, we expect manufacturers and suppliers have 
access to failure data nearing 450,000 miles through their R&D programs 
evaluating Heavy HDE over their current useful life. We expect 
manufacturers also have experience with their engines at this mileage 
through their extended warranty offerings; thus, they already possess 
real world operational data in addition to their internal 
evaluations.\331\
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    \331\ Brakora, Jessica. Memorandum to docket EPA-HQ-OAR-2019-
0055. ``Example Extended Warranty Packages for Heavy-duty Engines''. 
September 29, 2022.
---------------------------------------------------------------------------

    Several organizations commented on the proposed years or hours 
criteria for warranty. One supplier noted that analyses focused on 
tractors and their relatively high mileages may not accurately predict 
the use of vocational vehicles that are more limited by hours of 
operation. The same supplier suggested EPA should further differentiate 
warranties by vehicles classes and vocations. Another organization 
cautioned against warranty periods that are one-size-fits-all. Two 
organizations supported applying an hours-based warranty period for all 
engine classes to cover lower-speed applications and the 20-mph 
conversion factor that we proposed.
    We agree that vocational vehicles have distinct use patterns; 
however, we did not propose and are not finalizing warranty periods at 
the vehicle level to distinguish between vehicle types in this rule. We 
are finalizing three warranty thresholds for each heavy-duty engine 
class: A mileage threshold that is likely to reached first by vehicles 
driving many miles annually, a years threshold that is likely to be 
reached first by vehicles that drive infrequently or seasonally, and an 
hours threshold that is likely to be reached first by vehicles that 
drive frequently at lower speeds or with significant idling. We believe 
adding an hours threshold in the final rule to the mileage- and years-
based warranty periods for all engine classes will lead to more 
equitable warranty obligations across the range of possible vehicle 
applications for which a heavy-duty engine may be used.
ii. Warranty for Incomplete Vehicle Refueling Emission Controls
    As noted in Section III.E, we are finalizing refueling emission 
standards for Spark-ignition HDE that are certified as incomplete 
vehicles above 14,000 lb GVWR.\332\ Our refueling standards are 
equivalent to the refueling standards that are in effect for light- and 
heavy-duty complete Spark-ignition HDVs. We project manufacturers would 
meet the new refueling standards by adapting the existing onboard 
refueling vapor recovery (ORVR) systems from systems designed for 
complete vehicles. The new ORVR systems will likely supplement existing 
evaporative emission control systems installed on these vehicles.
---------------------------------------------------------------------------

    \332\ See the final updates to 40 CFR 1037.103.
---------------------------------------------------------------------------

    We are finalizing warranty periods for the ORVR systems of 
incomplete vehicles above 14,000 lb GVWR that align with the current 
warranty periods for the evaporative systems on those vehicles. 
Specifically, warranty periods for refueling emission controls would be 
5 years or 50,000 miles on incomplete Light HDV, and 5 years or 100,000 
miles on incomplete Medium HDV and Heavy HDV, as proposed. See our 
final updates to 40 CFR 1037.120. Our approach to apply the existing 
warranty periods for evaporative emission control systems to the ORVR 
systems is similar to our approach to the final regulatory useful life 
periods associated with our final refueling standards discussed in 
Section IV.A. We received no adverse comments on our proposed warranty 
periods for refueling emission controls.
2. Maintenance
    In this section, we describe the migrated and updated maintenance 
provisions we are finalizing for heavy-duty highway engines. Section 
IV.F of this preamble summarizes the current durability demonstration 
requirements and our final updates.
    Our final maintenance provisions, in a new section 40 CFR 1036.125, 
combine and amend the existing criteria pollutant maintenance 
provisions from 40 CFR 86.004-25 and 86.010-38. Similar to other part 
1036 sections we are adding in this rule, the structure of the new 40 
CFR 1036.125 is consistent with the maintenance sections in the 
standard-setting parts of other sectors (e.g., nonroad compression-
ignition engines in 40 CFR 1039.125). In 40 CFR 1036.205(i), we are 
codifying the current manufacturer practice of including maintenance 
instructions in their application for certification such that approval 
of those instructions would be part of a manufacturer's certification 
process.\333\ We are also finalizing a new paragraph 40 CFR 1036.125(h) 
outlining several owner's manual requirements, including migrated and 
updated provisions from 40 CFR 86.010-38(a).
---------------------------------------------------------------------------

    \333\ The current submission of maintenance instructions 
provisions in 40 CFR 86.079-39 are migrated into the requirements 
for an application for certification provisions in 40 CFR 1036.205.
---------------------------------------------------------------------------

    This section summarizes the final provisions that clarify the types 
of maintenance, update the options for demonstrating critical emission-
related maintenance will occur and the minimum scheduled maintenance 
intervals for certain components, and specify the requirements for 
maintenance instructions. The proposed rule provided an extensive 
discussion of the rationale and information supporting the proposed 
maintenance provisions (87 FR 17520, March 28, 2022). See also section 
6 of the Response to Comments for a detailed discussion of the comments 
and how they may have informed changes we are making to the proposal in 
this final rule.
i. Types of Maintenance
    The new 40 CFR 1036.125 clarifies that maintenance includes any 
inspection, adjustment, cleaning, repair, or replacement of components 
and, consistent with 40 CFR 86.004-25(a)(2), broadly classifies 
maintenance as emission-related or non-emission-related and scheduled 
or unscheduled.\334\ As proposed, we are finalizing five types of 
maintenance that manufacturers may choose to schedule: Critical 
emission-related maintenance, recommended additional maintenance, 
special maintenance, noncritical emission-related maintenance, and non-
emission-related maintenance. As we explained in the proposal, 
identifying and defining these maintenance categories in final 40 CFR 
1036.125 distinguishes between the types of maintenance manufacturers 
may choose to recommend to owners in

[[Page 4366]]

maintenance instructions, identifies the requirements that apply to 
maintenance performed during certification durability demonstrations, 
and clarifies the relationship between the different types of 
maintenance, emissions warranty requirements, and in-use testing 
requirements. The final provisions thus also specify the conditions for 
scheduling each of these five maintenance categories.
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    \334\ We include repairs as a part of maintenance because proper 
maintenance would require owners to repair failed or malfunctioning 
components. We note that repairs are considered unscheduled 
maintenance that would not be performed during durability testing 
and may be covered under warranty.
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    We summarize several revisions to the proposed critical emission-
related maintenance provisions in Section 0 with additional details in 
section 6 of the Response to Comments document. As proposed, the four 
other types of maintenance will require varying levels of EPA approval. 
In 40 CFR 1036.125(b), we propose to define recommended additional 
maintenance as maintenance that manufacturers recommend owners perform 
for critical emission-related components in addition to what is 
approved for those components under 40 CFR 1036.125(a). We are 
finalizing this provision as proposed except for a clarification in 
wording to connect additional recommended maintenance and critical 
emission-related maintenance more clearly. Under the final provisions, 
a manufacturer may recommend that owners replace a critical emission-
related component at a shorter interval than the manufacturer received 
approval to schedule for critical emission-related maintenance; 
however, the manufacturer will have to clearly distinguish their 
recommended intervals from the critical emission-related scheduled 
maintenance in their maintenance instructions. As described in this 
Section III.B.2 and the proposal, recommended additional maintenance is 
not performed in the durability demonstration and cannot be used to 
deny a warranty claim, so manufacturers will not be limited by the 
minimum maintenance intervals or need the same approval from EPA by 
demonstrating the maintenance would occur.
    In 40 CFR 1036.125(c), we proposed that special maintenance would 
be more frequent maintenance approved at shorter intervals to address 
special situations, such as atypical engine operation. We received one 
comment requesting we clarify special maintenance in proposed 40 CFR 
1036.125(c) and we are finalizing this provision as proposed except 
that we are including an example of biodiesel use in the final 
paragraph (c). Under the final provisions, manufacturers will clearly 
state that the maintenance is associated with a special situation in 
the maintenance instructions provided to EPA and owners.
    In 40 CFR 1036.125(d), as proposed, we are finalizing that 
noncritical emission-related maintenance includes inspections and 
maintenance that is performed on emission-related components but is 
considered ``noncritical'' because emission control will be unaffected 
(consistent with existing 40 CFR 86.010-38(d)). Under this final 
provision, manufacturers may recommend noncritical emission-related 
inspections and maintenance in their maintenance instructions if they 
clearly state that it is not required to maintain the emissions 
warranty.
    In 40 CFR 1036.125(e), we are updating the paragraph heading from 
nonemission-related maintenance to maintenance that is not emission-
related to be consistent with other sectors. The final provision, as 
proposed, describes the maintenance as unrelated to emission controls 
(e.g., oil changes) and states that manufacturers' maintenance 
instructions can include any amount of maintenance unrelated to 
emission controls that is needed for proper functioning of the engine.
Critical Emission-Related Components
    Consistent with the existing and proposed maintenance provisions, 
the final provisions continue to distinguish certain components as 
critical emission-related components. The proposal did not migrate the 
specific list of components defined as ``critical emission-related 
components'' from 40 CFR 86.004-25(b)(6)(i); instead, we proposed and 
are finalizing that manufacturers identify their specific critical 
components by obtaining EPA's approval for critical emission-related 
maintenance using 40 CFR 1036.125(a). Separately, we also proposed a 
new definition for critical emission-related components in 40 CFR 
1068.30 and are finalizing with revision. The final definition is 
consistent with paragraph 40 CFR 86.004-25(b)(6)(i)(I) and the current 
paragraph IV of 40 CFR part 1068, appendix A, as proposed.\335\ We are 
removing the proposed reference to 40 CFR 1068, appendix A, in the 
final definition, since appendix A specifies emission-related 
components more generally. To avoid having similar text in two 
locations, we are also replacing the current text of paragraph IV of 40 
CFR 1068, appendix A, with a reference to the new part 1068 definition 
of critical emission-related components.
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    \335\ Paragraph (b)(6)(i)(I) concludes the list of critical 
emission-related components in 40 CFR 86.004-25 with a general 
description stating: ``Any other component whose primary purpose is 
to reduce emissions or whose failure would commonly increase 
emissions of any regulated pollutant without significantly degrading 
engine performance.'' The existing paragraph (IV) of 40 CFR 1068, 
appendix A similarly states: ``Emission-related components also 
include any other part whose primary purpose is to reduce emissions 
or whose failure would commonly increase emissions without 
significantly degrading engine/equipment performance.''
---------------------------------------------------------------------------

ii. Critical Emission-Related Maintenance
    A primary focus of the final maintenance provisions is critical 
emission-related maintenance. Critical emission-related maintenance 
includes any adjustment, cleaning, repair, or replacement of emission-
related components that manufacturers identify as having a critical 
role in the emission control of their engines. The final 40 CFR 
1036.125(a), consistent with current maintenance provisions in 40 CFR 
part 86 and the proposal, will continue to allow manufacturers to seek 
advance approval from EPA for new emission-related maintenance they 
wish to include in maintenance instructions and perform during 
durability demonstration. The final 40 CFR 1036.125(a) retains the same 
proposed structure that includes a maintenance demonstration and 
minimum maintenance intervals, and a pathway for new technology that 
may be applied in engines after model year 2020.
    We are finalizing with revision the maintenance demonstration 
proposed in 40 CFR 1036.125(a)(1). The final provision includes the 
five proposed options for manufacturers to demonstrate the maintenance 
is reasonably likely to be performed in-use, with several clarifying 
edits detailed in the Response to Comments document .\336\ As further 
discussed in Section IV.D, we are finalizing the separate statement in 
40 CFR 1036.125(a)(1) that points to the final inducement provisions, 
noting that we will accept DEF replenishment as reasonably likely to 
occur if an engine meets the specifications in proposed 40 CFR 
1036.111; we are not setting a minimum maintenance interval for DEF 
replenishment. Also, as noted in the proposal and reiterated here, the 
first maintenance demonstration option, described in 40 CFR 
1036.125(a)(1)(i), is intended to cover emission control technologies 
that have an inherent performance degradation that coincides with 
emission increases, such as back pressure resulting from a clogged DPF.
---------------------------------------------------------------------------

    \336\ The five maintenance demonstration options are consistent 
with current maintenance demonstration requirements in 40 CFR 
86.004-25 and 86.094-25.
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    Consistent with the current and proposed maintenance provisions, we 
are specifying minimum maintenance

[[Page 4367]]

intervals for certain emission-related components, such that 
manufacturers may not schedule more frequent maintenance than we allow. 
In 40 CFR 1036.125(a)(2), we are updating the list of components with 
minimum maintenance intervals to more accurately reflect components in 
use today and extending the replacement intervals such that they 
reflect replacement intervals currently scheduled for those components. 
See the NPRM preamble for a discussion of our justification for 
terminology changes we are applying in the final rule, and the list of 
components that we are not migrating from 40 CFR part 86 because they 
are obsolete or covered by other parts.
    Consistent with current maintenance provisions, we proposed to 
disallow replacement of catalyst beds and particulate filter elements 
within the regulatory useful life of the engine.\337\ We are removing 
reference to catalyst beds and particular filter elements in the 
introductory text of paragraph (a)(2) and instead are adding them, with 
updated terminology, as a separate line in the list of components in 
Table 1 of 40 CFR 1036.125(a)(2) with minimum maintenance intervals 
matching the final useful life values of this rule.\338\ Including 
catalyst substrates and particulate filter substrates directly in the 
table of minimum maintenance intervals more clearly connects the 
intervals to the useful life values. In response to manufacturer 
comments requesting clarification, we are also adding a reference to 40 
CFR 1036.125(g) in paragraph (a)(2) to clarify that manufacturers are 
not restricted from scheduling maintenance more frequent than the 
minimum intervals, including replacement of catalyst substrates and 
particulate filter substrates, if they pay for it.
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    \337\ Existing 40 CFR 86.004-25(b)(4)(iii) states that only 
adjustment and cleaning are allowed for catalyst beds and 
particulate filter elements and that replacement is not allowed 
during the useful life. Existing 40 CFR 86.004 25(i) clarifies that 
these components could be replaced or repaired if manufacturers 
demonstrate the maintenance will occur and the manufacturer pays for 
it.
    \338\ In the final provision, we replaced ``catalyst bed'' with 
``catalyst substrate'' and ``particulate filter element'' with 
``particulate filter substrate''.
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    We are finalizing as proposed the addition of minimum intervals for 
replacing hybrid system components in engine configurations certified 
as hybrid engines or hybrid powertrains, which would include the 
rechargeable energy storage system (RESS). Our final minimum intervals 
for hybrid system components equal the current useful life for the 
primary intended service classes of the engines that these electric 
power systems are intended to supplement or replace.\339\
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    \339\ We note that Table IV-3 and the corresponding Table 1 of 
40 CFR 1036.125(a)(2) include a reference to ``hybrid system 
components'', which we inadvertently omitted from the tables in the 
proposed rule.
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    Table IV-3 summarizes the minimum replacement intervals we are 
finalizing in a new table in 40 CFR 1036.125(a)(2). As explained in the 
proposal, we believe it is appropriate to account for replacement 
intervals that manufacturers have already identified and demonstrated 
will occur for these components and the final replacement intervals 
generally match the shortest mileage interval (i.e., most frequent 
maintenance) of the published values, with some adjustments after 
considering comments. Commenters noted that some sensors are not 
integrated with a listed system and requested EPA retain a discrete set 
of minimum intervals for sensors, actuators, and related ECMs. We agree 
and are specifying minimum intervals that match the current intervals 
for sensors, actuators, and related control modules that are not 
integrated into other systems. We are retaining the proposed text to 
indicate that intervals specified for a given system would apply for 
all to actuators, sensors, tubing, valves, and wiring associated with 
that component associated with that system. We are also revising the 
minimum intervals for ignition wires from the proposed 100,000 miles to 
50,000 miles to match the current intervals and adding an interval for 
ignition coils at the same 50,000 miles after considering comments. See 
section 6 of the Response to Comments document for other comments we 
considered when developing the final maintenance provisions.
    We proposed to retain the maintenance intervals specified in 40 CFR 
86.004-25 for adjusting or cleaning components as part of critical 
emission-related maintenance. We are finalizing the proposed 
maintenance intervals for adjusting and cleaning with one correction. 
Commenters noted that the proposal omitted an initial minimum interval 
for adjusting or cleaning EGR system components. Consistent with 40 CFR 
86.004-25(b), we are correcting the proposed intervals for several 
components (catalyst system components, EGR system components (other 
than filters or coolers), particulate filtration system components, and 
turbochargers) from 150,000 miles or 4,500 hours to include an initial 
interval of 100,000 miles or 3,000 hours, with subsequent intervals of 
150,000 miles or 4,500 hours. We did not reproduce the new Table 2 from 
40 CFR 1036.125(a)(2) showing the minimum intervals for adjusting or 
cleaning components in this preamble.

 Table IV-3--Minimum Scheduled Maintenance Intervals in Miles (or Hours) for Replacing Critical Emission-Related
                                          Components in 40 CR 1036.125
----------------------------------------------------------------------------------------------------------------
                                           Spark-ignition
               Components                        HDE            Light HDE        Medium HDE         Heavy HDE
----------------------------------------------------------------------------------------------------------------
Spark plugs.............................      25,000 (750)  ................  ................  ................
DEF filters.............................  ................   100,000 (3,000)   100,000 (3,000)   100,000 (3,000)
Crankcase ventilation valves and filters    60,000 (1,800)    60,000 (1,800)    60,000 (1,800)    60,000 (1,800)
 .......................................
Ignition wires and coils................    50,000 (1,500)  ................  ................  ................
Oxygen sensors..........................    80,000 (2,400)  ................  ................  ................
Air injection system components.........   110,000 (3,300)  ................  ................  ................
Sensors, actuators, and related control    100,000 (3,000)   100,000 (3,000)   150,000 (4,500)   150,000 (4,500)
 modules that are not integrated into
 other systems..........................
Particulate filtration systems (other      100,000 (3,000)   100,000 (3,000)   250,000 (7,500)   250,000 (7,500)
 than filter substrates)................
Catalyst systems (other than catalyst      110,000 (3,300)   110,000 (3,300)   185,000 (5,550)  435,000 (13,050)
 substrates), fuel injectors, electronic
 control modules, hybrid system
 components, turbochargers, and EGR
 system components (including filters
 and coolers)...........................
Catalyst substrates and particulate       200,000 (10,000)  270,000 (13,000)  350,000 (17,000)  650,000 (32,000)
 filter substrates......................
----------------------------------------------------------------------------------------------------------------

[[Page 4368]]

    We received no adverse comments on the proposed approach to 
calculate the corresponding hours values for each minimum maintenance 
interval. Consistent with our current maintenance provisions and the 
proposal, we are finalizing minimum hours values based on the final 
mileage and a 33 miles per hour vehicle speed (e.g., 150,000 miles 
would equate to 4,500 hours).\340\ Consistent with the current 
maintenance intervals specified in part 86 and the proposal, we are not 
including year-based minimum intervals; OEMs can use good engineering 
judgment if they choose to include a scheduled maintenance interval 
based on years in their owner's manuals.
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    \340\ The minimum hours-based intervals for catalyst substrates 
and particulate filter substrates match the useful life hours that 
apply for each primary intended service class to ensure these 
components are not replaced within the regulatory useful life of the 
engine, consistent with existing maintenance provisions. The useful 
life hours are calculated using a 22 miles per hour conversion 
factor as described in Section IV.A of this preamble.
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    For new technology, not used on engines before model year 2020, we 
are providing a process for manufacturers to seek approval for new 
scheduled maintenance, consistent with the current maintenance 
provisions. We received no adverse comment on the proposal to migrate 
40 CFR 86.094-25(b)(7)(ii), which specifies a process for approval of 
new critical emission-related maintenance associated with new 
technology, and 40 CFR 86.094-25(b)(7)(iii), which allows manufacturers 
to ask for a hearing if they object to our decision.\341\ We are 
finalizing a new 40 CFR 1036.125(a)(3), as proposed.
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    \341\ Hearing procedures are specified in 40 CFR 1036.820 and 40 
CFR part 1068, subpart G.
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iii. Source of Parts and Repairs
    Consistent with CAA section 207 \342\ and our existing regulations 
for heavy duty vehicles under part 1037, we proposed a new paragraph 40 
CFR 1036.125(f) to clarify that manufacturers' written instructions for 
proper maintenance and use, discussed further in Section IV.B.2.vi, 
generally cannot limit the source of parts and service owners use for 
maintenance unless the component or service is provided without charge 
under the purchase agreement, with two specified exceptions.\343\ We 
are moving, with revisions, the content of the proposed paragraph (f) 
to 40 CFR 1036.125(h)(2). See section 6 of the Response to Comments. 
Consistent with the proposal, we are finalizing that manufacturers 
cannot specify a particular brand, trade, or corporate name for 
components or service and cannot deny a warranty claim due to 
``improper maintenance'' based on owners choosing not to use a 
franchised dealer or service facility or a specific brand of part 
unless the component or service is provided without charge under the 
purchase agreement. Consistent with current maintenance provisions and 
CAA section 207(c)(3)(B), a second exception is that manufacturers can 
specify a particular service facility and brand of parts only if the 
manufacturer convinces EPA during the approval process that the engine 
will only work properly with the identified service or component. We 
are not finalizing at this time the proposed 40 CFR 1036.125(f) 
requirement regarding specific statements on the first page of written 
maintenance instructions; after consideration of comments, we agree 
with commenters that the final regulatory text accomplishes the intent 
of our proposal without the additional proposed first sentence.
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    \342\ See, e.g., CAA section 207(c)(3)(B) and (g).
    \343\ This provision has been adopted in the standard-setting 
parts of several other sectors (see 1037.125(f)).
---------------------------------------------------------------------------

iv. Payment for Scheduled Maintenance
    We proposed 40 CFR 1036.125(g) to allow manufacturers to schedule 
maintenance not otherwise allowed by 40 CFR 1036.125(a)(2) if they pay 
for it. The proposed paragraph (g) also included four criteria to 
identify components for which we would require manufacturers to pay for 
any scheduled maintenance within the regulatory useful life. The four 
criteria, which are based on current provisions that apply for nonroad 
compression-ignition engines, would require manufacturers to pay for 
components that were not in general use on similar engines before 1980, 
whose primary purpose is to reduce emissions, where the cost of the 
scheduled maintenance is more than 2 percent of the price of the 
engine, and where failure to perform the scheduled maintenance would 
not significantly degrade engine performance.\344\ We continue to 
believe that components meeting the four criteria are less likely to be 
maintained without the incentive of manufacturers paying for it and we 
are finalizing 40 CFR 1036.125(g) as proposed.
---------------------------------------------------------------------------

    \344\ See 40 CFR 1039.125(g).
---------------------------------------------------------------------------

    As noted in Section IV.B.2.ii, manufacturers cannot schedule 
replacement of catalyst substrates or particulate filter substrates 
within the regulatory useful life of the engine unless they pay for it. 
As explained in the proposed rule, in addition to catalyst substrates 
and particulate filter substrates, we expect that replacement of EGR 
valves, EGR coolers, and RESS of certain hybrid systems also meet the 
40 CFR 1036.125(g) criteria and manufacturers will only be able to 
schedule replacement of these components if the manufacturer pays for 
it.
    In the proposal, we requested comment on restricting the 
replacement of turbochargers irrespective of the four criteria of 
proposed 40 CFR 1036.125(g). One commenter suggested that EPA should 
follow the CARB approach that requires manufacturers to pay for 
scheduled maintenance of turbochargers within the regulatory useful 
life. The comment indicated the cost of repairs and ``significant 
impact'' of a failed turbocharger on emissions justify requiring that 
manufacturers pay for replacement. We disagree and are not finalizing a 
separate requirement for turbochargers. Turbochargers are not added to 
engines specifically to control emissions and we expect the performance 
degredation associated with a failing turbocharger is likely to 
motivate owners to fix the problem. We continue to believe the four 
criteria in 40 CFR 1036.125(g) are an appropriate means of 
distinguishing components for which manufacturers should pay in order 
to ensure the components are maintained.
v. Maintenance Instructions
    As proposed, our final 40 CFR 1036.125 preserves the requirement 
that the manufacturer provide written instructions for properly 
maintaining and using the engine and emission control system, 
consistent with CAA section 207(c)(3)(A).\345\ The new 40 CFR 
1036.125(h) describes the information that we are requiring 
manufacturers to include in an owner's manual, consistent with CAA 
sections 202 and 207. The new 40 CFR 1036.125(h)(1) generally migrates 
the existing maintenance instruction provisions specified in 40 CFR 
86.010-38(a). As described in Section IV.B.2.iii, final 40 CFR 
1036.125(h)(2) includes revised content from proposed 40 CFR 
1036.125(f). The final paragraph (h)(2) is also revised from the 
proposed regulatory text to clarify that EPA did not intend the 
proposed paragraph as a requirement for owners to maintain

[[Page 4369]]

records in order to make a warranty claim. While 40 CFR 1036.120(d) 
allows manufacturers to deny warranty claims for improper maintenance 
and use, owners have expressed concern that it is unclear what 
recordkeeping is needed to document proper maintenance and use, and 
both the proposed and final 40 CFR 1036.125(h)(2) are intended to 
ensure manufacturers are communicating their expectations to owners.
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    \345\ CAA section 207(c)(3)(A) states that the manufacturer 
shall furnish with each new motor vehicle or motor vehicle engine 
written instructions for the proper maintenance and use of the 
vehicle or engine by the ultimate purchaser and that such 
instructions shall correspond to regulations which the Administrator 
shall promulgate.
---------------------------------------------------------------------------

    Consistent with the current 40 CFR 86.010-38(a)(2), our final 40 
CFR 1036.125(h)(2) also requires manufacturers to describe in the 
owner's manual if manufacturers expect owners to maintain any 
documentation to show the engine and emission control system have been 
properly maintained and, if so, to specify what documentation. 
Manufacturers should be able to identify their expectations for 
documenting routine maintenance and repairs related to warranty claims. 
For instance, if a manufacturer requires a maintenance log as part of 
their process for reviewing warranty claims and determining whether the 
engine was properly maintained, we expect the owner's manual would 
provide an example log with a clear statement that warranty claims 
require an up-to-date maintenance record. We note that 40 CFR 1036.125 
specifies minimum maintenance intervals for critical emission-related 
maintenance, and limits manufacturers from invalidating warranty if 
certain other types of allowable maintenance are not performed (i.e., 
recommended additional maintenance and noncritical emission-related 
maintenance). Any required maintenance tasks and intervals must be 
consistent with the requirements and limitations in 40 CFR 1036.125. As 
explained at proposal, we may review a manufacturer's information 
describing the parameters and documentation for demonstrating proper 
maintenance before granting certification for an engine family.
    The maintenance instructions requirements we are finalizing for the 
remainder of 40 CFR 1036.125(h) are covered in the serviceability 
discussion in Section IV.B.3 and inducements discussion in Section IV.C 
of this preamble. As noted in Section IV.B.3, our serviceability 
provisions supplement the service information provisions specified in 
40 CFR 86.010-38(j).\346\
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    \346\ We are not migrating the service information provisions 
into 40 CFR part 1036 in this rule.
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vi. Performing Scheduled Maintenance on Test Engines
    We are finalizing our proposed update to 40 CFR 1065.410(c) to 
clarify that inspections performed during testing include electronic 
monitoring of engine parameters. While we intended the proposed update 
to include prognostic systems, the proposed text referred only to 
electronic tools, and we are revising from the proposed text in the 
final provision to include ``or internal engine systems'' to clarify. 
Manufacturers that include prognostic systems as part of their engine 
packages to identify or predict malfunctioning components may use those 
systems during durability testing and would describe any maintenance 
performed as a result of those systems, consistent with 40 CFR 
1065.410(d), in their application for certification. We note that, to 
apply these electronic monitoring systems in testing, the inspection 
tool (e.g., prognostic system) must be readable without specialized 
equipment so it is available to all customers or accessible at 
dealerships and other service outlets consistent with CAA sections 
202(m) and 206.
3. Serviceability
    This Section IV.B.3 describes the provisions we are finalizing to 
improve serviceability, reduce mal-maintenance, and ensure owners are 
able to maintain emission control performance throughout the entire in-
use life of heavy-duty engines. See section IV.B.2 of this preamble for 
a discussion of manufacturers' obligations to provide maintenance 
instructions to operators. Also see the preamble of the proposed rule 
for further discussion of why EPA proposed these serviceability and 
maintenance information provisions.\347\ The final serviceability and 
maintenance information provisions were informed by comments, and we 
summarize key comments in this section.\348\ We provide complete 
responses to the serviceability-related comments in section 5 of the 
Response to Comments.
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    \347\ See section IV.B.3. of the proposed preamble (87 FR 17517, 
March 28, 2022).
    \348\ While we requested comment on several potential approaches 
to improve serviceability of electric vehicles in the proposal (87 
FR 17517, March 28, 2022), EPA is not taking final action on any 
requirements related to this request at this time; we may consider 
the comments provided on improved serviceability of electric 
vehicles in future rulemakings relevant to electric vehicles. See 
section 5.3 of the Response to Comments document for details on 
comments received.
---------------------------------------------------------------------------

i. Background
    Without proper maintenance, the emission controls on heavy-duty 
engines may not function as intended, which can result in increased 
emissions. Mal-maintenance, which includes delayed or improper repairs 
and delayed or unperformed maintenance, can be intentional (e.g., 
deferring repairs due to costs) or unintentional (e.g., not being able 
to diagnose the actual problem and make the proper repair).
    In the NPRM, EPA discussed stakeholder concerns with the 
reliability of MY 2010 and later heavy-duty engines, and significant 
frustration expressed by owners concerning their experiences with 
emission control systems on such engines. EPA explained that 
stakeholders have communicated to EPA that, although significant 
improvements have been made to emission control systems since they were 
first introduced into the market, reliability and serviceability 
continue to cause them concern. EPA received comments on the NPRM 
further highlighting problems from fleets, owners, and operators. 
Commenters noted issues with a range of emission-related components, 
including: Sensors (DPF and SCR-related), DEF dosers, hoses, filters, 
EGR valves, EGR coolers and EGR actuators, SCR catalysts, DOC, turbos, 
wiring, decomposition tubes, cylinder heads, and DPFs. Specifically, 
for example, comments included described experiences with 
aftertreatment wiring harness failures, DEF nozzles plugging or over-
injecting, NOX sensor failures, defective DEF pumps and 
level sensors, systems being less reliable in rain and cold weather, 
more frequent required cleaning of DPFs than anticipated, and problems 
related to DEF build-up. See section 5 of the Response to Comment for 
further information and the detailed comments.
    In addition to existing labeling, diagnostic, and service 
information requirements, EPA proposed to require important maintenance 
information be made available in the owner's manual as a way to improve 
factors that may contribute to mal-maintenance. The proposed 
serviceability provisions were expected to result in better service 
experiences for independent repair technicians, specialized repair 
technicians, owners who repair their own equipment, and possibly 
vehicle inspection and maintenance technicians. Furthermore, the 
proposed provisions were intended to improve owner experiences 
operating and maintaining heavy-duty engines and provide greater 
assurance of long-term in-use emission reductions by reducing the 
likelihood of occurrences of tampering.
    Given the importance and complexity of emission control systems and 
the

[[Page 4370]]

impact to drivers for failing to maintain such systems (e.g., 
inducements), EPA believes it is critical to include additional 
information about emission control systems in the owner's manual. We 
proposed to require manufacturers to provide more information 
concerning the emission control system in the owner's manual to include 
descriptions of how the emissions systems operate, troubleshooting 
information, and diagrams. EPA has imposed similar requirements in the 
past, such as when EPA required vacuum hose diagrams be included on the 
emission label to improve serviceability and help inspection and 
maintenance facilities identify concerns with that system.\349\
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    \349\ See 53 FR 7675, March 9, 1988, and 55 FR 7177, February 
29. 1990 for more information.
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ii. Final Maintenance Information Requirements for Improved 
Serviceability
    EPA received both supportive and adverse comments from a number of 
stakeholders on the serviceability proposals (see section 5 of the 
Response to Comments). For example, comments from service providers and 
manufacturers largely objected to the proposed serviceability 
requirements, while owners and operators supported the proposed 
requirements. EPA is finalizing requirements for improved 
serviceability so that owners and operators can more easily understand 
advanced emission control system operation and identify issues in such 
systems as they arise during operation. To the extent EPA can ensure 
this information is harmonized among manufacturers, we believe this 
will improve the experiences of owners, operators, parts counter 
specialists, and repair technicians, and reduce frustration that could 
otherwise create an incentive to tamper.
    CAA section 207(c)(3)(A) requires manufacturers to provide 
instructions for the proper maintenance and use of a vehicle or engine 
by the ultimate purchaser and requires such instructions to correspond 
to EPA regulations. The final rule includes maintenance provisions 
migrated and updated from 40 CFR part 86, subpart A, to a new 40 CFR 
1036.125, that specify the maintenance instructions manufacturers must 
provide in an owner's manual to ensure that owners can properly 
maintain their vehicles (see Section IV.B.2). Additionally, as a part 
of the new 40 CFR 1036.125(h), we are finalizing specific maintenance 
information manufacturers must provide in the owner's manual to improve 
serviceability:
     EPA is finalizing with revision the proposed requirement 
for manufacturers to provide a description of how the owner can use the 
OBD system to troubleshoot problems and access emission-related 
diagnostic information and codes stored in onboard monitoring systems. 
The revision replaces the proposed requirement that the owner's manual 
include general information on how to read and understand OBD codes 
with a more specific set of required information. The final requirement 
specifies that, at a minimum, manufacturers provide a description of 
how to use the OBD system to troubleshoot and access information and 
codes, including (1) identification of the OBD communication protocol 
used, (2) location and type of OBD connector, (3) a brief description 
of what OBD is (including type of information stored, what a 
malfunction indicator light (MIL) is, explanation that some MILs may 
self-extinguish), and (4) a note that certain engine and emission data 
is publicly available using any scan tool, as required by EPA. As we 
describe further in section IV.C.1.iii, we are not taking final action 
on the proposed health monitors. Therefore, we are also not requiring 
manufacturers to provide information about the role of the health 
monitor to help owners service their engines before components fail in 
the description of the OBD system.
     EPA is finalizing as proposed, with a few clarifications 
in wording, a requirement for manufacturers to identify critical 
emission systems and components, describe how they work, and provide a 
general description of how the emission control systems operate.
     EPA is finalizing as proposed the requirement for 
manufacturers to include one or more diagrams of the engine and its 
emission-related components, with two exceptions: (1) We are not 
finalizing the proposed requirements to include the identity, location, 
and arrangement of wiring in the diagram, and we are not requiring 
information related to the expected pressures at the particulate filter 
and exhaust temperatures throughout the aftertreatment system. The 
final requirement specifies the following information is required, as 
proposed:
    [cir] The flow path for intake air and exhaust gas.
    [cir] The flow path of evaporative and refueling emissions for 
spark-ignition engines, and DEF for compression-ignition engines, as 
applicable.
    [cir] The flow path of engine coolant if it is part of the emission 
control system described in the application for certification.
    [cir] The identity, location, and arrangement of relevant emission 
sensors, DEF heater and other DEF delivery components, and other 
critical emission-related components.
    [cir] Terminology to identify components must be consistent with 
codes the manufacturer uses for the OBD system.
     EPA is revising the proposed requirement relating to 
exploded-view drawings and basic assembly requirements in the owner's 
manual. The final provision replaces a general reference to 
aftertreatment devices with a specific list of components that should 
be included in one or more diagrams in the owner's manual, including: 
EGR Valve, EGR actuator, EGR cooler, all emission sensors (e.g., 
NOX, soot sensors, etc.), temperature and pressure sensors 
(EGR, DPF, DOC, and SCR-related, including DEF-related temperature and 
pressure sensors), fuel (DPF-related) and DEF dosing units and 
components (e.g., pumps, filters, metering units, nozzles, valves, 
injectors), DEF quality sensors, DPF filter, DOC, SCR catalyst, 
aftertreatment-related control modules, any other DEF delivery-related 
components (e.g., lines and freeze protection components), and 
aftertreatment-related wiring harnesses if replaceable separately. The 
revision also notes that the information could be provided in multiple 
diagrams. We are also revising the proposed requirement to include part 
numbers for all components in the drawings and instead are only 
requiring part numbers for sensors and filters related to SCR or DPF 
systems. We are not finalizing at this time the broader requirement 
that this information include enough detail to allow a mechanic to 
replace any of these components. Finally, once published for a given 
model year, manufacturers will not be required to revise their owner's 
manual with updated part numbers if a part is updated in that model 
year. We recognize that manufacturers are able to use outdated part 
numbers to find updated parts.
     EPA is finalizing as proposed the requirement for 
manufacturers to provide a statement instructing owners or service 
technicians where and how to find emission recall and technical repair 
information available without charge from the National Highway Traffic 
Safety Administration.\350\
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    \350\ NHTSA provides this information at https://www.nhtsa.gov/recalls. For example, manufacturers should specify if the 
information would be listed under ``Vehicle'' or ``Equipment.''
---------------------------------------------------------------------------

     EPA is finalizing with some modifications from the 
proposal the requirement for manufacturers to

[[Page 4371]]

include a troubleshooting guide to address SCR inducement-related and 
DPF regeneration-related warning signals. For the SCR system this 
requirement includes:
    [cir] The inducement derate schedule (including indication that DEF 
quantity-related inducements will be triggered prior to the DEF tank 
being completely empty).
    [cir] The meaning of any trouble lights that indicate specific 
problems (e.g., DEF level).
    [cir] A description of the three types of SCR-related derates (DEF 
quantity, DEF quality and tampering) and a notice that further 
information on the cause of (e.g., trouble codes) is available using 
the OBD system.
     For the DPF system the troubleshooting guide requirement 
includes:
    [cir] Information on the occurrence of DPF-related derates.
    [cir] EPA is finalizing in 40 CFR 1036.110(c) that certain 
information must be displayed on-demand for operators. Specifically, 
EPA is finalizing the requirement that for SCR-related inducements, 
information such as the derate and associated fault code must be 
displayed on-demand for operators (see section IV.D.3 for further 
information). EPA is also finalizing requirements that the number of 
DPF regenerations, DEF consumption rate, and the type of derate (e.g., 
DPF- or SCR-related) and associated fault code for other types of 
emission-related derates be displayed on-demand for operators (see 
section IV.C.1.iii for further information).
    EPA proposed that manufacturers include a Quick Response (QR) code 
on the emission label that would direct repair technicians, owners, and 
inspection and maintenance facilities to a website providing critical 
emission systems information at no cost. We are not taking final action 
at this time on the proposed requirement to include QR codes on the 
emission control information label. After considering manufacturers' 
comments, we intend to engage in further outreach and analysis before 
adopting electronic labeling requirements, such as QR codes. In this 
rule, we are instead finalizing that the owner's manual must include a 
URL directing owners to a web location for the manufacturer's service 
information required in 40 CFR 86.010-38(j). We recognize the potential 
for electronic labels with QR codes or similar technology to provide 
useful information for operators, inspectors, and others. Manufacturers 
from multiple industry sectors are actively pursuing alternative 
electronic labeling. In the absence of new requirements for electronic 
labeling, manufacturers must continue to meet requirements for applying 
physical labels to their engines. Manufacturers may include on the 
vehicle or engine any QR codes or other electronic labeling information 
that goes beyond what is required for the physical emission control 
information label. EPA is also not taking final action at this time on 
the proposed requirement to include a basic wiring diagram for 
aftertreatment-related components in the owner's manual. Finally, EPA 
is not taking final action at this time on requirements related to DPF 
cleaning; instead, EPA intends to continue to follow the work CARB has 
undertaken in this area and may consider taking action in a future 
rule.
iii. Other Emission Controls Education Options
    In addition to our proposed provisions to provide more easily 
accessible service information for operators, we sought comment on 
whether educational programs and voluntary incentives could lead to 
better maintenance and real-world emission benefits. We received 
comments in response to the NPRM supportive of improving such 
educational opportunities to promote an understanding of how advanced 
emission control technologies function and the importance of emissions 
controls as they relate to the broader economy and the environment (see 
section 5.4 of the Response to Comment for further details). EPA is not 
finalizing any requirements related to this request for comment at this 
time but will look for future opportunities to improve the availability 
of information on emission control systems.

C. Onboard Diagnostics

    As used here, the terms ``onboard diagnostics'' and ``OBD'' refer 
to systems of electronic controllers and sensors required by regulation 
to detect malfunctions of engines and emission controls. EPA's OBD 
regulations for heavy-duty engines are contained in 40 CFR 86.010-18, 
which were initially promulgated on February 24, 2009 (74 FR 8310). 
Those requirements were harmonized with CARB's OBD program then in 
place. Consistent with our authority under CAA section 202(m), EPA is 
finalizing an update to our OBD regulations in 40 CFR 1036.110 to align 
with existing CARB OBD requirements as appropriate, better address 
newer diagnostic methods and available technologies, and to streamline 
provisions.
1. Incorporation of California OBD Regulations by Reference
    CARB OBD regulations for heavy-duty engines are codified in title 
13, California Code of Regulations, sections 1968.2, 1968.5, 1971.1, 
and 1971.5. EPA is finalizing our proposal to incorporate by reference 
in 40 CFR 1036.810 the OBD requirements CARB adopted October 3, 
2019.351 352 In response to the NPRM, EPA received a number 
of comments supportive of EPA's adoption of the revised CARB OBD 
program, including the 2019 rule amendments. As discussed in this 
section and reflected in final 40 CFR 1036.110(b), our final rule will 
harmonize with the majority of CARB's existing OBD regulations, as 
appropriate and consistent with the CAA, and make these final 
requirements mandatory beginning in MY 2027 and optional in earlier 
model years. These new requirements better address newer diagnostic 
methods and available technologies and have the additional benefit of 
being familiar to industry. For example, the new tracking requirements 
contained in CARB's updated OBD program, known as the Real Emissions 
Assessment Logging (``REAL'') program, track real-world emissions 
systems performance of heavy-duty engines. The REAL tracking 
requirements include the collection of onboard data using existing OBD 
sensors and other vehicle performance parameters, which will better 
allow the assessment of real world, in-use emission performance.
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    \351\ This CARB rulemaking became effective the same day and 
began to phase in under CARB's regulations with MY 2022. The CARB 
regulations we are adopting are available at: https://ww2.arb.ca.gov/resources/documents/heavy-duty-obd-regulations-and-rulemaking.
    \352\ The legal effect of incorporation by reference is that the 
material is treated as if it were published in the Federal Register 
and CFR. This material, like any other properly issued rule, has the 
force and effect of law. Congress authorized incorporation by 
reference in the Freedom of Information Act to reduce the volume of 
material published in the Federal Register and CFR. (See 5 U.S.C. 
552(a) and 1 CFR part 51). See https://www.archives.gov/federal-register/cfr/ibr-locations.html for additional information.
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    EPA's final OBD requirements are closely aligned with CARB's 
existing requirements with a few exceptions, as further described in 
Section IV.C.1.i. We are finalizing exclusions to certain provisions 
that are not appropriate for a Federal program and including additional 
elements to improve on the usefulness of OBD systems for operators.

[[Page 4372]]

i. CARB OBD Provisions Revised or Not Included in the Finalized Federal 
Program
    CARB's 2019 OBD program includes some provisions that may not be 
appropriate for the Federal regulations.\353\ In a new 40 CFR 
1036.110(b), we are finalizing the following clarifications and changes 
to the 2019 CARB regulations that we are otherwise incorporating by 
reference:
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    \353\ EPA is reviewing a waiver request under CAA section 209(b) 
from California for the Omnibus rule; note, we are making no 
determination in this action about the appropriateness of these 
provisions for CARB's regulation.
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    1. Modifying the threshold requirements contained in the 2019 CARB 
OBD standards we are adopting (as discussed in Section IV.C.1.ii),
    2. Providing flexibilities to delay compliance up to three model 
years for small manufacturers who have not previously certified an 
engine in California,
    3. Allowing good engineering judgment to correlate the CARB OBD 
standards with EPA OBD standards,
    4. Clarifying that engines must comply with OBD requirements 
throughout EPA's useful life as specified in 40 CFR 1036.104, which may 
differ from CARB's required useful life for some model years,
    5. Clarifying that the purpose and applicability statements in 13 
CCR 1971.1(a) and (b) do not apply,
    6. Not requiring the manufacturer self-testing and reporting 
requirements in 13 CCR 1971.1(l)(4) ``Verification of In-Use 
Compliance'' and 1971.5(c) ``Manufacturer Self-Testing'' (note, in the 
proposal we inadvertently cited incorrect CARB provisions for the 
intended referenced requirements),
    7. Retaining our existing deficiency policy (which we are also 
migrating into 40 CFR 1036.110(d)), adjusting our deficiency timing 
language to match CARB's, and specifying that the deficiency provisions 
in 13 CCR 1971.1(k) do not apply,
    8. Requiring additional freeze frame data requirements (as further 
explained in Section IV.C.1.iii),
    9. Requiring additional data stream parameters for compression- and 
spark-ignition engines (as further explained in Section IV.C.1.iii), 
and
    10. Providing flexibilities to reduce redundant demonstration 
testing requirements for engines certified to CARB OBD requirements.
    With regard to the second through the fifth items, EPA is 
finalizing these requirements as proposed for the reasons stated in the 
proposal. For the sixth item, EPA is finalizing this requirement for 
the reasons stated in the proposal and as proposed with the exception 
of a correction to the CARB reference we cited.
    EPA received supportive comment from manufacturers on our proposal 
to migrate our existing deficiency requirements, and adverse comment 
from manufacturers and CARB requesting that EPA harmonize with CARB's 
retroactive deficiency provisions. CARB's deficiency requirements are 
described in 13 CCR 1971.1(k) and include descriptions of requirements 
such as how deficiencies are granted, fines charged for deficiencies, 
allowable timelines, and the application of retroactive deficiencies. 
We are finalizing as proposed to migrate our existing approach to 
deficiency provisions in 40 CFR 86.010-18(n) into 40 CFR 
1036.110(d).\354\ See section 7.1 of the Response to Comments for 
further details on comments received and EPA's responses.
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    \354\ See 74 FR 8310, 8349 (February 24, 2009).
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    EPA also received comment concerned with EPA's regulatory language 
describing the allowable timeframe for deficiencies. Commenters said 
EPA's proposed deficiency timeline is shorter than CARB's and that EPA 
should harmonize with CARB and provide manufacturers with 3 years to 
make hardware-related changes. EPA is finalizing a change to 40 CFR 
1036.110(d)(3) to ensure our language is consistent with CARB's 
deficiency timeline in 13 CCR 1971.1(k)(4).
    EPA received supportive and adverse comment on the proposal to 
require additional freeze frame data requirements, including that the 
reference in our regulations was overly broad and possibly in error. 
EPA is finalizing these requirements with revisions to those proposed 
in 40 CFR 1036.110(b)(8) to be more targeted. It is critical for there 
to be sufficient emissions-related parameters captured in freeze frame 
data to enable proper repairs.
    EPA received supportive and adverse comment on the proposal to 
require additional data stream parameter requirements, including 
comment that our regulations needed to be more specific. EPA is 
finalizing these requirements with revisions to those proposed in 40 
CFR 1036.110(b)(9) to properly capture the additional elements we 
intended to add to the freeze frame and to ensure these additional 
parameters are interpreted properly as an expansion of the existing 
data stream requirements in 13 CCR 1971.1(h)(4.2). Access to important 
emissions-related data parameters is critical for prompt and proper 
repairs.
    EPA is finalizing flexibilities to reduce redundant demonstration 
testing requirements for engines certified to CARB OBD requirements, 
see section IV.C.1.iv. of this preamble for further discussion on what 
we are finalizing.
    It is important to emphasize that by not incorporating certain 
existing CARB OBD requirements (e.g., the ``Manufacturer Self-Testing'' 
requirements) into our regulations, we are not waiving our authority to 
require such testing on a case-by-case basis. CAA section 208 gives EPA 
broad authority to require manufacturers to perform testing not 
specified in the regulations in such circumstances. Thus, should we 
determine in the future that such testing is needed, we would retain 
the authority to require it pursuant to CAA section 208.
ii. OBD Threshold Requirements
a. Malfunction Criteria Thresholds
    Existing OBD requirements specify how OBD systems must monitor 
certain components and indicate a malfunction prior to when emissions 
would exceed emission standards by a certain amount, known as an 
emission threshold. Emission thresholds for these components under the 
existing requirements in the 2019 CARB OBD update that we are 
incorporating by reference are generally either an additive or 
multiplicative value above the applicable exhaust emission standard. 
EPA proposed to modify the threshold requirements in the 2019 CARB OBD 
update to be consistent with the provisions finalized by CARB in their 
Omnibus rule in December of 2021 and not tighten threshold requirements 
while finalizing lower emission standards.\355\ \356\ This meant, for 
example, that for monitors required to detect a malfunction before 
NOX emissions exceed 1.75 times the applicable existing 
NOX standard, the manufacturer would continue to use the 
same numeric threshold (e.g., 0.35 g/bhp-hr NOX) for the new 
emission standards finalized in this rule.
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    \355\ California Air Resources Board. Staff Report: Addendum to 
the Final Statement of Reasons for Rulemaking--Public Hearing to 
Consider the Proposed Heavy-Duty Engine and Vehicle Omnibus 
Regulation and Associated Amendments. December 20, 2021. https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2020/hdomnibuslownox/fsoraddendum.pdf.
    \356\ EPA is reviewing a waiver request under CAA section 209(b) 
from California for the Omnibus rule; note, we are making no 
determination in this action about the appropriateness of these 
provisions for CARB's regulation.
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    EPA received comments from manufacturers and operators in support

[[Page 4373]]

of finalizing the threshold provisions as proposed, and a comment from 
CARB stating that three engine families have recently been certified to 
lower FELs indicating EPA should finalize lower thresholds. We note 
that CARB stated that two of these engine families were certified with 
deficiencies, and thus these engines did not fully meet all specific 
OBD requirements (see section 7.1 of the Response to Comment for 
further detail about these comments and EPA's responses). EPA is 
finalizing with minor revision future numerical values for OBD 
NOX and PM thresholds that align with the numerical value 
that results under today's NOX and PM emissions 
requirements.
    We are finalizing as proposed a NOX threshold of 0.40 g/
hp-hr and a PM threshold of 0.03 g/hp-hr for compression-ignition 
engines for operation on the FTP and SET duty cycles. We are finalizing 
as proposed a PM threshold of 0.015 g/hp-hr for spark-ignition engines 
for operation on the FTP and SET duty cycles. For spark-ignition 
engines, we proposed NOX thresholds of 0.30 and 0.35 g/hp-hr 
for monitors detecting a malfunction before NOX emissions 
exceed 1.5 and 1.75 times the applicable standard, respectively. We are 
finalizing these numeric threshold values without reference to what 
percent exceedance is relevant and instead are clarifying that the 
0.35g/hp-hr standard applies for catalyst monitors and that 0.30g/hp-hr 
applies for all other monitors, to ensure the proper numeric thresholds 
can be applied to engines certified under 13 CCR 1968.2 and 1971.1.. 
EPA intends to continue to evaluate the capability of HD OBD monitors 
to accommodate lower thresholds to correspond to the lower emission 
levels for the final emission standards and may consider updating 
threshold requirements in the future as more in-use data becomes 
available.
    We also inadvertently omitted from the proposed 40 CFR 1036.110(b) 
the specific threshold criteria for SI and CI engine HC and CO 
emissions that coincided with our overall expressed intent to harmonize 
with the threshold requirements included in CARB's Omnibus rule and not 
tighten OBD emission thresholds.\357\ Consistent with this intent, we 
are finalizing a provision in 40 CFR 1036.110(b)(5) that instructs 
manufacturers to use numeric values that correspond to existing HC and 
CO standards (0.14 g/hp-hr for HC, 15.5 g/hp-hr for CO from 
compression-ignition engines, and 14.4 g/hp/hr for spark-ignition 
engines) to determine the required thresholds. Applying this 
methodology will result in calculations that produce thresholds 
equivalent to existing thresholds. Including this clarification avoids 
unintentionally lowering such thresholds.
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    \357\ While CARB standards refer to nonmethane hydrocarbon 
standards as ``NMHC'' EPA's regulation refers to ``HC'' generically 
for such standards, but we define HC in 40 CFR 1036.104 to be NMHC 
for gasoline- and diesel-fueled engines.
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b. Test-Out Criteria
    CARB OBD requirements include ``test-out'' provisions in 13 CCR 
1968.2 and 1971.1 which allow manufacturers to be exempt from 
monitoring certain components if failure of these components meets 
specified criteria.\358\ EPA is adopting these test-out provisions 
through the incorporation by reference of CARB's updated 2019 OBD 
requirements. Similar to the revisions we proposed and are finalizing 
for malfunction criteria, EPA's assessment is that for compression 
ignition engines test-out criteria should also not be tightened at this 
time. However, we inadvertently omitted from the proposed 40 CFR 
1036.110(b) the specific adjustments to test-out criteria for 
compression-ignition engines included in CARB's Omnibus rule that are 
necessary to result in such criteria not being tightened. Consistent 
with our overall expressed intent to (1) not tighten OBD requirements, 
and (2) modify the 2019 CARB requirements we are adopting by 
harmonizing with the numeric values included in CARB's Omnibus rule, we 
are finalizing a revision from the proposal to include test-out 
criteria calculation instructions into our regulations.
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    \358\ ``Test-out'' provisions may be identified in CARB OBD 
regulations specifically as ``test-out'' requirements or through 
language describing that certain components or systems are ``exempt 
from monitoring'' if manufacturers can demonstrate certain 
conditions are met.
---------------------------------------------------------------------------

    Specifically, we are finalizing a provision that manufacturers 
seeking to use the test-out criteria to exempt engines from certain 
monitoring in the incorporated by reference 2019 CARB regulations 13 
CCR 1968.2 and 1971.1 must calculate the criteria based on specified 
values provided in 40 CFR 1036.110(b)(5). For example, 13 CCR 
1971.1(e)(3.2.6) specifies that one of the requirements for an EGR 
catalyst to be exempt from monitoring is if no malfunction of the EGR 
catalyst can cause emissions to increase by 15 percent or more of the 
applicable standard as measured from the appropriate test cycle. The 
requirement we are finalizing in 40 CFR 1036.110(b)(5) instructs 
manufacturers to use specific values for that ``applicable standard'' 
to calculate the required test-out criteria. For example, for the EGR 
catalyst test-out provision, this would result in a NOX 
test-out criterion of 0.03 g/hp-hr (0.2 g/hp-hr  0.15). 
Including this provision is consistent with the intent of our proposal 
and avoids unintentionally lowering such test-out criteria that would 
render such test-out criteria generally inconsistent with the other 
provisions we are finalizing in 40 CFR 1036.110(b)(5), and enables 
manufacturers to continue using these provisions.
c. Applicable Thresholds for Engines Certified to 40 CFR Part 1036 Used 
in Heavy-Duty Vehicles Less Than 14,000 Pounds GVWR
    We are finalizing as proposed that engines installed in vehicles at 
or below 14,000 lbs GVWR are subject to OBD requirements under the 
light-duty program in 40 CFR 86.1806-17. Commenters pointed out that 
the proposed rule did not specify alternative thresholds for engines 
certified to 40 CFR part 1036 on an engine dynamometer that are subject 
to OBD requirements under 40 CFR 86.1806-17. Without such a provision, 
manufacturers would be subject to the existing thresholds in 40 CFR 
86.1806-17 that are based on standards set for light-duty chassis-
certified vehicles. Consistent with our statements in the NPRM that our 
proposal intended to harmonize with the threshold requirements included 
in CARB's Omnibus policy and not lower emission threshold levels in our 
proposed OBD regulations, we are clarifying in 40 CFR 86.1806-17(b)(9) 
that the thresholds we are finalizing in 40 CFR 1036.110(b)(5) apply 
equally for engines certified under 40 CFR part 1036 that are used in 
vehicles at or below 14,000 lbs GVWR.
iii. Additional OBD Provisions in the Proposed Federal Program
    In the NPRM, EPA proposed to include additional requirements to 
ensure that OBD can be used to properly diagnose and maintain emission 
control systems to avoid increased real-world emissions. This was also 
a part of our effort to update EPA's OBD program and respond to 
numerous concerns raised in the ANPR about the difficulty of diagnosing 
and maintaining proper functionality of advanced emission control 
technologies and the important role accessible and robust diagnostics 
play in this process. At this time, after consideration of comments, we 
are finalizing a limited set of these proposed provisions (see section 
7 of the Response to Comments documents for further detail on comments 
and

[[Page 4374]]

EPA's responses). Where OBD requirements between EPA and CARB may 
differ, EPA is finalizing as proposed provisions allowing us to accept 
CARB OBD approval as long as a manufacturer can demonstrate that the 
CARB program meets the intent of EPA OBD requirements and submits 
documentation as specified in 40 CFR 1036.110(b).
    In this section we describe the final additional EPA certification 
requirements in 40 CFR 1036.110 for OBD systems, which, consistent with 
CAA section 202(m),\359\ are intended to provide more information and 
value to the operator and play an important role in ensuring expected 
in-use emission reductions are achieved long-term. With respect to our 
proposed provisions to require additional information from OBD systems 
be made publicly available, we received supportive comments from 
operators and adverse comments from manufacturers. After considering 
these comments, we are revising our final provision from those 
proposed, as summarized here and provide in more detail in section 7 of 
the Response to Comments document. We are not taking final action at 
this time on the proposed requirement to include health monitors. In 
addition to driver information requirements we are adopting to increase 
the availability of serviceability and inducement-related information 
(see section IV.B.3 and IV.D.3 respectively of this preamble), we are 
also finalizing in 40 CFR 1036.110(c) that the following information 
must be made available in the cab on-demand in lieu of the proposed 
health monitors:
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    \359\ For example, CAA section 202(m)(5) specifies that by 
regulation EPA shall require (subject to an exception where 
information is entitled to protection as trade secrets) 
manufacturers to provide promptly to any person engaged in the 
repairing or servicing of heavy-duty engines with any and all 
information needed to make use of the emission control diagnostics 
system required under CAA section 202 and such other information 
including instructions for making emission related diagnosis and 
repairs.
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     The total number of diesel particulate filter regeneration 
events that have taken place since installing the current particulate 
filter.
     Historical and current rate of DEF consumption (e.g., 
gallons of DEF consumed per mile or gallons of DEF consumed per gallon 
of diesel fuel consumed.) This information is designed such that 
operators can reset it as needed to capture specific data for 
comparison purposes.
     For AECD conditions (outside of inducements) related to 
SCR or DPF systems that derate the engine (e.g., either a speed or 
torque reduction), the fault code for the detected problem, a 
description of the fault code, and the current restriction.
    For all other health monitor provisions proposed in 40 CFR 
1036.110(c)(3), we are not taking final action on those proposed 
provisions at this time.
    In addition to incorporating an improved list of publicly available 
data parameters by harmonizing with updated CARB OBD requirements, in 
40 CFR 1036.110(b)(9) EPA is finalizing as proposed for the reasons 
explained further in the proposal to add signals to the list, including 
to specifically require that all parameters related to fault conditions 
that trigger vehicle inducement also be made readily available using 
generic scan tools. EPA expects that each of these additional 
requirements will be addressed even where manufacturers relied in part 
on a CARB OBD approval to satisfy Federal requirements in order to 
demonstrate under 40 CFR 1036.110(b) that the engine meets the intent 
of 40 CFR 1036.110. The purpose of including additional parameters is 
to make it easier to identify malfunctions of critical aftertreatment 
related components, especially where failure of such components would 
trigger an inducement. We are revising the proposed new parameters for 
HD SI engines in 40 CFR 1036.110(b)(10) after considering comments. See 
section 3 of the Response to Comments.
    We are also finalizing a general requirement in 40 CFR 
1036.110(b)(9)(vi) to make all parameters available that are used as 
the basis for the decision to put a vehicle into an SCR- or DPF-related 
derate. For example, if the failure of an open-circuit check for a DEF 
quality sensor leads to an engine inducement, the owner/operator would 
be able to identify this fault condition using a generic scan tool. We 
are finalizing a requirement that manufacturers make additional 
parameters available for all engines so equipped,\360\ including:
---------------------------------------------------------------------------

    \360\ Memorandum to Docket EPA-HQ-OAR-2019-0055: ``Example 
Additional OBD Parameters''. Neil Miller, Amy Kopin. November 21, 
2022.
---------------------------------------------------------------------------

      For Compression Ignition engines:

[cir] Inlet DOC and Outlet DOC pressure and temperature
[cir] DPF Filter Soot Load (for all installed DPFs)
[cir] DPF Filter Ash Load (for all installed DPFs)
[cir] Engine Exhaust Gas Recirculation Differential Pressure
[cir] DEF quality-related signals
[cir] Parking Brake, Neutral Switch, Brake Switch, and Clutch Switch 
Status
[cir] Aftertreatment Dosing Quantity Commanded and Actual
[cir] Wastegate Control Solenoid Output
[cir] Wastegate Position Commanded and Actual
[cir] DEF Tank Temperature
[cir] DEF Doser Control Status
[cir] DEF System Pressure
[cir] DEF Pump Commanded Percentage
[cir] DEF Coolant Control Valve Control Position Commanded and Actual
[cir] DEF Line Heater Control Outputs
[cir] Speed and output shaft torque consistent with 40 CFR 1036.115(d)

     For Spark Ignition Engines:

[cir] Air/Fuel Enrichment Enable flags: Throttle based, Load based, 
Catalyst protection based
[cir] Percent of time not in stoichiometric operation (including per 
trip and since new)

    One of the more useful features in the CARB OBD program for 
diagnosing and repairing emissions components is the requirement for 
``freeze frame'' data to be stored by the system. To comply with this 
requirement, manufacturers must capture and store certain data 
parameters (e.g., vehicle operating conditions such as the 
NOX sensor output reading) within 10 seconds of the system 
detecting a malfunction. The purpose of storing this data is in part to 
record the likely area of malfunction. EPA is finalizing a requirement 
in 40 CFR 1036.110(b)(8) to require that manufacturers capture the 
following elements as freeze frame data: Those data parameters 
specified in 1971.1(h)(4.2.3)(E), 1971.1(h)(4.2.3)(F), and 
1971.1(h)(4.2.3)(G). We are also specifying that these additional 
parameters would be added according to the specifications in 13 CCR 
1971.1(h)(4.3). EPA believes this is essential information to make 
available to operators for proper maintenance.
iv. Demonstration Testing Requirements
    Existing requirements of 40 CFR 86.010-18(l) and 13 CCR 1971.1(l) 
specify the number of test engines for which a manufacturer must submit 
monitoring system demonstration emissions data. Specifically, a 
manufacturer certifying one to five engine families in a given model 
year must provide emissions test data for a single test engine from one 
engine rating, a manufacturer certifying six to ten engine families in 
a given model year must provide emissions test data for a single test 
engine from two different engine ratings, and a manufacturer certifying 
eleven or more engine families in a given model year must provide 
emissions test data for a single test engine from three different 
engine ratings.
    EPA received supportive and adverse comment on a proposed 
flexibility to

[[Page 4375]]

reduce redundant demonstration testing requirements for certain engines 
where an OBD system designed to comply with California OBD requirements 
is being used in both a CARB proposed family and a proposed EPA-only 
family and the two families are also identical in all aspects material 
to expected emission characteristics. EPA issued guidance last year on 
this issue.\361\ We are finalizing as proposed to codify this guidance 
as a provision, subject to certain information submission requirements 
for EPA to evaluate if this provision's requirements have been met, for 
model years 2027 and later engines in 40 CFR 1036.110(b)(11). 
Manufacturers may also use the flexibility in earlier model years. More 
specifically, we are finalizing the provision as proposed to count two 
equivalent engines families as one for the purposes of determining OBD 
demonstration testing requirements, where equivalent means they are 
identical in all aspects material to emission characteristics, as such, 
testing is not necessary to ensure a robust OBD program. 40 CFR 
1036.110(b)(11) requires manufacturers to submit additional information 
as needed to demonstrate that the engines meet the requirements of 40 
CFR 1036.110 that are not covered by the California Executive order, as 
well as results from any testing performed for certifying engine 
families (including equivalent engine families) with the California Air 
Resources Board and any additional information we request as needed to 
evaluate whether the requirements of this provision are met.
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    \361\ EPA Guidance Document CD-2021-04 (HD Highway), April 26, 
2021, ``Information on OBD Monitoring System Demonstration for Pairs 
of EPA and CARB Families Identical in All Aspects Other Than 
Warranty.'' Available here:  https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=52574&flag=1.
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    We took comment on and are finalizing language that this 
flexibility will apply for cases where equivalent engine families also 
have different inducement strategies. We are aware that the auxiliary 
emission control devices (AECDs) needed to implement the engine 
derating associated with inducements do not affect engine calibrations 
in a way that would prevent OBD systems from detecting when emissions 
exceed specified levels. Rather, those AECDs simply limit the range of 
engine operation that is available to the driver. Thus, testing of 
different inducement strategies in these AECDs would also not be 
necessary to ensure a robust OBD program and we would consider such 
differences between engines to not be material to emission 
characteristics relevant to these OBD testing requirements. Any 
difference in impacts between the engines would be a consequence of the 
driver's response to the inducement itself, which could also occur even 
with the same inducement strategy, rather than a difference in the 
functioning of the OBD systems in the engines. In that way, inducements 
are analogous to warranty for purposes of counting engine families for 
OBD testing requirements. See section 8 of the Response to Comments for 
details on the comments received and EPA's responses.
v. Use of CARB OBD Approval for EPA OBD Certification
    Existing EPA OBD regulations allow manufacturers seeking an EPA 
certificate of conformity to comply with the Federal OBD requirements 
by demonstrating to EPA how the OBD system they have designed to comply 
with California OBD requirements also meets the intent behind Federal 
OBD requirements, as long as the manufacturer complies with certain 
certification documentation requirements. EPA has implemented these 
requirements by allowing a manufacturer to submit an OBD approval 
letter from CARB for the equivalent engine family where a manufacturer 
can demonstrate that the CARB OBD program has met the intent of the EPA 
OBD program. In other words, EPA has interpreted these requirements to 
allow OBD approval from CARB to be submitted to EPA for approval. We 
are finalizing as proposed to migrate the language from 40 CFR 86.010-
18(a)(5) to 40 CFR 1036.110(b) to allow manufacturers to continue to 
use a CARB OBD approval letter to demonstrate compliance with Federal 
OBD regulations for an equivalent engine family where manufacturers can 
demonstrate that the CARB OBD program has met the intent of the EPA OBD 
program.
    To demonstrate that your engine meets the intent of EPA OBD 
requirements, we are finalizing as proposed that the OBD system must 
address all the provisions described in 40 CFR 1036.110(b) and (c) and 
adding clarification in 40 CFR 1036.110(b) that manufacturers must 
submit information demonstrating that all EPA requirements are met. In 
the case where a manufacturer chooses not to include information 
showing compliance with additional EPA OBD requirements in their CARB 
certification package (e.g., not including the additional EPA data 
parameters in their CARB certification documentation), EPA expects 
manufacturers to provide separate documentation along with the CARB OBD 
approval letter to show they have met all EPA OBD requirements. This 
process also applies in potential future cases where CARB has further 
modified their OBD requirements such that they are different from but 
meet the intent of existing EPA OBD requirements. EPA expects 
manufacturers to submit documentation as is currently required by 40 
CFR 86.010-18(m)(3), detailing how the system meets the intent of EPA 
OBD requirements and information on any system deficiencies. As a part 
of this update to EPA OBD regulations, we are clarifying as proposed in 
40 CFR 1036.110(b)(11)(iii) that we can request that manufacturers send 
us information needed for us to evaluate how they meet the intent of 
our OBD program using this pathway. This would often mean sending EPA a 
copy of documents submitted to CARB during the certification process.
vi. Use of the SAE J1979-2 Communications Protocol
    In a February 2020 workshop, CARB indicated their intent to propose 
allowing the use of Unified Diagnostic Services (``UDS'') through the 
SAE J1979-2 communications protocol for heavy-duty OBD with an optional 
implementation as early as MY 2023.\362 363\ The CARB OBD update that 
includes this UDS proposal has not yet been finalized, but was 
submitted to California's Office of Administrative Law for approval in 
July of 2022.\364\ CARB stated that engine manufacturers are concerned 
about the limited number of remaining undefined 2-byte diagnostic 
trouble codes (``DTC'') and the need for additional DTCs for hybrid 
vehicles. SAE J1979-2 provides 3-byte DTCs, significantly increasing 
the number of DTCs that can be defined. In addition, this change would 
provide additional features for data access that improve the usefulness 
of generic scan tools to repair vehicles.
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    \362\ SAE J1979-2 was issued on April 22, 2021 and is available 
here: https://www.sae.org/standards/content/j1979-2_202104/.
    \363\ CARB Workshop for 2020 OBD Regulations Update, February 
27, 2020. Available here: https://ww3.arb.ca.gov/msprog/obdprog/obd_feb2020wspresentation.pdf.
    \364\ CARB Proposed Revisions to the On-Board Diagnostic System 
Requirements and Associated Enforcement Provisions for Passenger 
Cars, Light-Duty Trucks, Medium-Duty Vehicles and Engines, and 
Heavy-Duty Engines, available: https://ww2.arb.ca.gov/rulemaking/2021/obd2021.
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    This update has not been finalized by CARB in time for us to 
include it in this final rule. In consideration of manufacturers who 
want to certify their engine families in the future for

[[Page 4376]]

nationwide use, and after consideration of expected environmental 
benefits associated with the use of this updated protocol, we are 
finalizing as proposed a process for reviewing and approving 
manufacturers' requests to comply using the alternative communications 
protocol.
    While EPA believes our existing requirements in 40 CFR 86.010-
18(a)(5) allow us to accept OBD systems using SAE J1979-2 that have 
been approved by CARB, there may be OEMs that want to obtain an EPA-
only certificate (i.e., does not include certification to California 
standards) for engines that do not have CARB OBD approval for MYs prior 
to MY 2027 (i.e., prior to when the 40 CFR part 1036 OBD provisions of 
this final rule become mandatory). EPA is finalizing as proposed to 
allow the use of SAE J1979-2 for manufacturers seeking EPA OBD 
approval. We are adopting this as an interim provision in 40 CFR 
1036.150(v) to address the immediate concern for model year 2026 and 
earlier engines. Once EPA's updated OBD requirements are in effect for 
MY 2027, we expect to be able to allow the use of SAE J1979-2 based on 
the final language in 40 CFR 1036.110(b); however, we do not specify an 
end date for the provision in 40 CFR 1036.150(v) to make sure there is 
a smooth transition toward using SAE J1979-2 for model years 2027 and 
later. This provides manufacturers the option to upgrade their OBD 
protocol to significantly increase the amount of OBD data available to 
owners and repair facilities.
    CAA section 202(m)(4)(C) requires that the output of the data from 
the emission control diagnostic system through such connectors shall be 
usable without the need for any unique decoding information or device, 
and it is not expected that the use of SAE J1979-2 would conflict with 
this requirement. Further, CAA section 202(m)(5) requires manufacturers 
to provide promptly to any person engaged in the repairing or servicing 
of motor vehicles or motor vehicle engines, and the Administrator for 
use by any such persons, with any and all information needed to make 
use of the emission control diagnostics system prescribed under this 
subsection and such other information including instructions for making 
emission related diagnosis and repairs. Manufacturers that voluntarily 
use J1979-2 as early as MY 2022 under interim provision 40 CFR 
1036.150(v) would need to provide access to systems using this 
alternative protocol at that time and meet all the relevant 
requirements in 40 CFR 86.010-18 and 1036.110. EPA did not receive 
adverse comment on the availability of tools that can read the new 
protocol from manufacturers or tool providers. CARB commented that 
staff anticipates tool vendors will be able to fully support the SAE 
J1979-2 protocol at a fair and reasonable price for the vehicle repair 
industry and consumers.
2. Cost Impacts
    Heavy-duty engine manufacturers currently certify their engines to 
meet CARB's OBD regulations before obtaining EPA certification for a 
50-state OBD approval. We anticipate most manufacturers will continue 
to certify with CARB and that they will certify to CARB's 2019 updated 
OBD regulations well in advance of the EPA program taking effect; 
therefore, we anticipate the incorporation by reference of CARB's 2019 
OBD requirements will not result in any additional costs. EPA does not 
believe the additional OBD requirements described here will result in 
any significant costs, as there are no requirements for: New monitors, 
new data parameters, new hardware, or new testing included in this 
rule. However, EPA has accounted for possible additional costs that may 
result from the final expanded list of public OBD parameters in the 
``Research and Development Costs'' of our cost analysis in Section V. 
EPA recognizes that there could be cost savings associated with reduced 
OBD testing requirements under final 40 CFR 1036.110(c)(11). For 
example, cost savings could come from the provision to not count engine 
families certified separately by EPA and CARB, but otherwise identical 
in all aspects material to expected emission characteristics, as 
different families when determining OBD demonstration testing (see 
section IV.C.1.iv of this document for further discussion on this 
provision). This potential reduction in demonstration testing burden 
could reduce costs such as labor and test cell time. However, 
manufacturers may choose not to certify engine families in this manner 
which would not translate to cost savings. Therefore, given the 
uncertainty in the potential for savings, we did not quantify the costs 
savings associated with this final provision.
D. Inducements
    Manufacturers have deployed urea-based SCR systems to meet the 
existing heavy-duty engine emission standards. EPA anticipates that 
manufacturers will continue to use this technology to meet the new 
NOX standards finalized in this rule. SCR is very different 
from other emission control technologies in that it requires operators 
to maintain an adequate supply of diesel exhaust fluid (DEF), which is 
generally a water-based solution with 32.5 percent urea. Operating an 
SCR-equipped engine without DEF or certain components like an SCR 
catalyst could cause NOX emissions to increase to levels 
comparable to having no NOX controls at all.
    The proposed rule described two key aspects of how our regulations 
currently require manufacturers to ensure engines will operate with an 
adequate supply of high-quality DEF, which we proposed to update and 
further codify. First, manufacturers currently must demonstrate 
compliance with our critical emissions-related schedule maintenance 
requirements, including 40 CFR 86.004-25(b). EPA has approved DEF 
refills as part of manufacturers' scheduled maintenance. EPA's approval 
is conditioned on manufacturers demonstrating that operators are 
reasonably likely to perform such maintenance. Manufacturers have 
consistently made this demonstration by designing their engines to go 
into a disabled mode that decreases a vehicle's maximum speed if the 
engine detects that operators are failing to provide an adequate supply 
of DEF. More specifically, manufacturers have generally complied by 
programming engines to restrict peak vehicle speeds after detecting 
that such maintenance has not been performed or detecting that 
tampering with the SCR system may have occurred. We refer to this 
strategy of derating engine power and vehicle speed as an 
``inducement.''
    Second, EPA's current regulations in 40 CFR 86.094-22(e) require 
that manufacturers comply with emission standards over the full 
adjustable range of ``adjustable parameters,'' and that, in determining 
the parameters subject to adjustment, EPA considers the likelihood that 
settings other than the manufacturer's recommended setting will occur 
in-use, including the effect of settings other than the manufacturer's 
recommended settings on engine performance. We have historically 
considered DEF level and quality as parameters that can be physically 
adjusted and may significantly affect emissions. EPA generally has 
approved manufacturers strategies consistent with guidance that 
described recommendations on ways manufacturers could meet adjustable 
parameter requirements when using SCR systems.\365\ This guidance 
states that manufacturers should demonstrate that operators are being 
made aware that DEF needs to be replaced through warnings and vehicle 
performance

[[Page 4377]]

deterioration that should not create undue safety concerns but be 
onerous enough to discourage drivers from operating without DEF (i.e., 
through inducement). See the proposed rule preamble for further 
background and discussion of the basis of EPA's proposed inducement 
regulations.
---------------------------------------------------------------------------

    \365\ See CISD-09-04 REVISED.
---------------------------------------------------------------------------

    With some modification from the proposal, EPA is adopting final 
inducement regulations in this final rule. The regulatory provisions 
also include changes compared to existing inducement guidance after 
consideration of manufacturer designs and operator experiences with SCR 
over the last several years. The inducement requirements included in 
this final rule supersede the existing guidance and are mandatory 
beginning in MY 2027 and voluntary prior to that and are intended to-
     Ensure that all critical emission-related scheduled 
maintenance has a reasonable likelihood of being performed while also 
deterring tampering of the SCR system.
     Set an appropriate inducement speed derating schedule that 
reflects experience gained over the past decade with SCR systems.
     Recognize the diversity of the real-world fleet with 
derate schedules that are tailored to a vehicle's operating 
characteristics.
     Improve the type and amount of information operators 
receive from the vehicle to both understand inducement actions and to 
help avoid or quickly remedy a problem that is causing an inducement.
     Allow operators to perform an inducement reset by using a 
generic scan tool or allowing for the engine to self-heal during normal 
driving.
     Address operator frustration with false inducements and 
low inducement speed restrictions that occur quickly, in part due to 
concern that such frustration may potentially lead to in-use tampering 
of the SCR system.
    This final rule includes several changes from the proposed rule 
after consideration of numerous comments. See section 8 of the Response 
to Comments for the detailed comments and EPA's response to those 
comments, including further discussion of the changes in the final rule 
compared to the proposed rule. As an overview, EPA is adopting as a 
maintenance requirement, as proposed, in 40 CFR 1036.125(a)(1) that 
manufacturers must meet the specifications in new 40 CFR 1036.111, 
which contains requirements for inducements related to SCR, to 
demonstrate that timely replenishment with high-quality DEF is 
reasonably likely to occur on in-use engines and that adjustable 
parameter requirements will be met. Specifically, EPA is finalizing as 
proposed to specify in 40 CFR 1036.115(f) that DEF supply and DEF 
quality are adjustable parameters. Regarding DEF supply, we are 
finalizing as proposed that the physically adjustable range includes 
any amount of DEF that the engine's diagnostic system does not 
recognize as a fault condition under new 40 CFR 1036.111. We are 
adopting a requirement under new 40 CFR 1036.115(i) for manufacturers 
to size DEF tanks corresponding to refueling events, which is 
consistent with the regulation we are replacing under 40 CFR 86.004-
25(b)(4)(v). Under the final requirements, manufacturers can no longer 
use the alternative option in 40 CFR 86.004-25(b)(6)(ii)(F) to 
demonstrate high-quality DEF replenishment is reasonably likely to be 
performed in use. As described in the proposed rule, EPA plans to 
continue to rely on the existing guidance in CD-13-13 that describes 
how manufacturers of heavy-duty highway engines determine the 
practically adjustable range for DEF quality. We inadvertently proposed 
to require that manufacturers use the physically adjustable range for 
DEF quality as the basis for defining a fault condition for inducements 
under 40 CFR 1036.111. Since we intended for the existing guidance to 
addresses issues related to the physically adjustable range for DEF 
quality, we are not finalizing the proposed provision in 40 CFR 
1036.115(f)(2) for DEF quality. EPA intends further consider the 
relationship between inducements and the practically adjustable range 
for DEF quality and may consider updating this guidance in the future.
    EPA is adopting requirements that inducements be triggered for 
three types of fault conditions: (1) DEF supply is low, (2) DEF quality 
does not meet manufacturer specifications, or (3) tampering with the 
SCR system. EPA is not taking final action at this time on the proposed 
requirement for manufacturers to include a NOX override to 
prevent false inducements. After consideration of public comments, the 
final inducement provisions at 40 CFR 1036.111 include updates from the 
proposed inducement schedules; more specifically, EPA is adopting 
separate inducement schedules for low-, medium-, and high-speed 
vehicles. EPA is also finalizing requirements for manufacturers to 
improve information provided to operators regarding inducements. The 
final rule also includes a requirement for manufacturers to design 
their engines to remove inducements after proper repairs are made, 
through self-healing or with the use of a generic scan tool to ensure 
that operators have performed the proper maintenance.
    These requirements apply starting in MY 2027, though manufacturers 
may optionally comply with these 40 CFR part 1036 requirements in lieu 
of provisions that apply under 40 CFR part 86 early. The following 
sections describe the inducement requirements for the final rule in 
greater detail.
1. Inducement Triggers
    Three types of fault conditions trigger inducements under 40 CFR 
1036.111. The first triggering condition is DEF quantity. Specifically, 
we require that SCR-equipped engines trigger an inducement when the 
amount of DEF in the tank has been reduced to a level corresponding to 
three remaining hours of engine operation. This triggering condition 
ensures that operators will be compelled to perform the necessary 
maintenance before the DEF supply runs out, which would cause emissions 
to increase significantly.
    The second triggering condition is DEF quality failing to meet 
manufacturer concentration specifications. This triggering condition 
ensures high quality DEF is used.
    Third, EPA is requiring inducements to ensure that SCR systems are 
designed to be tamper-resistant. We are requiring that manufacturers 
design their engines to monitor for and trigger an inducement for open-
circuit fault conditions for the following components: (1) DEF tank 
level sensor, (2) DEF pump, (3) DEF quality sensor, (4) SCR wiring 
harness, (5) NOX sensors, (6) DEF dosing valve, (7) DEF tank 
heater, (8) DEF tank temperature sensor, and (9) aftertreatment control 
module (ACM). EPA is also requiring that manufacturers monitor for and 
trigger an inducement if the OBD system has any signal indicating that 
a catalyst is missing (see OBD requirements for this monitor in 13 CCR 
1971.1(i)(3.1.6)). This list is the same as the list from the proposed 
rule, with two exceptions after consideration of comments. First, we 
are adding the DEF tank temperature sensor in the final rule. This 
additional sensor is on par with the DEF tank heater for ensuring that 
SCR systems are capable of monitoring for freezing conditions. Second, 
in consideration of comment, we are removing blocked DEF lines or 
dosing valves as a triggering condition because such a condition could 
be caused by crystallized DEF rather than any operator action and thus 
is not directly related to protecting against tampering with the SCR-
system. We believe this standardized list of required

[[Page 4378]]

tampering inducement triggers will be important for owners, operators, 
and fleets in repairing their vehicles by avoiding excessive cost and 
time to determine the reason for inducement.
2. Derate Schedule
    We are finalizing a different set of schedules than we proposed. 
First, we are adding a new category for medium-speed vehicles. Second, 
we are adjusting the low-speed category to have a lower final speed 
compared to the proposal and a lower average operating speed to 
identify this category. Third, we increased the average operating speed 
that qualifies a vehicle to be in the high-speed category. We are 
adopting derate schedules for low-, medium- and high-speed vehicles as 
shown in Table IV-13. Similar to the proposal, we differentiate these 
three vehicle categories based on a vehicle's calculated average speed 
for the preceding 30 hours of non-idle operation. Low-speed vehicles 
are those with an average operating speed below 15 mph. Medium-speed 
vehicles are those with average operating speeds at or above 15 and 
below 25 mph. High-speed vehicles are those with average operating 
speeds at or above 25 mph. Excluding idle from the calculation of 
vehicle speed allows us to more effectively evaluate each vehicle's 
speed profile; in contrast, time spent at idle would not help to give 
an indication of a vehicle's operating characteristics for purposes of 
selecting the appropriate derate schedule. EPA chose these final speeds 
after consideration of stakeholder comments (see section 8.3 of the 
Response to Comments for further information on comments received) and 
an updated analysis of real-world vehicle speed activity data from the 
FleetDNA database maintained by the National Renewable Energy 
Laboratory (NREL).366 367 Our analyses provided us with 
insight into the optimum way to characterize vehicles in a way to 
ensure these categories received appropriate inducements that would be 
neither ineffective nor overly restrictive.
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    \366\ EPA's original analysis of NREL data can be found here: 
Miller, Neil; Kopin, Amy. Memorandum to docket EPA-HQ-OAR-2019-0055-
0981. ``Review and analysis of vehicle speed activity data from the 
FleetDNA database.'' October 1, 2021.
    \367\ EPA's updated analysis of NREL data can be found here: 
Miller, Neil; Kopin, Amy. Memorandum to docket EPA-HQ-OAR-2019-0055. 
``Updated review and analysis of vehicle speed activity data from 
the FleetDNA database.'' October 13, 2022.

                                                            Table IV-13--Inducement Schedules
--------------------------------------------------------------------------------------------------------------------------------------------------------
                           High-speed vehicles                                     Medium-speed vehicles                    Low-speed vehicles
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                      Maximum speed (mi/   Hours of non-idle  Maximum speed (mi/   Hours of non-idle  Maximum speed (mi/
         Hours of non-idle engine operation                   hr)          engine operation           hr)          engine operation           hr)
--------------------------------------------------------------------------------------------------------------------------------------------------------
0...................................................                  65                   0                  55                   0                  45
6...................................................                  60                   6                  50                   5                  40
12..................................................                  55                  12                  45                  10                  35
60..................................................                  50                  45                  40                  30                  25
86..................................................                  45                  70                  35  ..................  ..................
119.................................................                  40                  90                  25  ..................  ..................
144.................................................                  35  ..................  ..................  ..................  ..................
164.................................................                  25  ..................  ..................  ..................  ..................
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The derate schedule for each vehicle category is set up with 
progressively increasing severity to induce the owner or operator to 
efficiently address conditions that trigger inducements. Table IV-13 
shows the derate schedules in cumulative hours. The initial inducement 
applies immediately when the OBD system detects any of the triggering 
fault conditions identified in section IV.D.1. The inducement schedule 
then steps down over time to result in the final inducement speed 
corresponding to each vehicle category. The inducement schedule 
includes a gradual transition (1mph every 5 minutes) at the beginning 
of each step of derate and prior to any repeat inducement occurring 
after a failed repair to avoid abrupt changes, as the step down in 
derate speeds in the schedules will be implemented while the vehicle is 
in motion. Inducements are intended to deteriorate vehicle performance 
to a point unacceptable for typical driving in a manner that is safe 
but onerous enough to discourage vehicles from being operated (i.e., 
impact the ability to perform work), such that operators will be 
compelled to replenish the DEF tank with high-quality DEF and not 
tamper with the SCR system's ability to detect whether there is 
adequate high-quality DEF. To this end, as explained in the proposal, 
our analyses of vehicle operational data from NREL show that even 
vehicles whose operation is focused on local or intracity travel depend 
on frequently operating at highway speeds to complete commercial 
work.\368\ Vehicles in an inducement under the schedules we are 
finalizing would not be able to maintain commercial functions. Our 
analysis of the NREL data also show that even medium- and low-speed 
vehicles travel at speeds up to 70 mph and indicate that it is likely 
regular highway travel is critical for low-speed vehicles to complete 
their work; for example, refuse trucks need to drop off collected waste 
at a landfill or transfer station before returning to neighborhoods.
---------------------------------------------------------------------------

    \368\ EPA's updated analysis of NREL data can be found here: 
Miller, Neil; Kopin, Amy. Memorandum to docket EPA-HQ-OAR-2019-0055. 
``Updated review and analysis of vehicle speed activity data from 
the FleetDNA database.'' October 13, 2022.
---------------------------------------------------------------------------

    Motorcoach operators submitted comments describing a greater 
sensitivity to any speed derate because of a much greater 
responsibility for carrying people safely to their intended 
destinations over longer distances, including their role in emergency 
response and national defense operations. After consideration of these 
comments, we are allowing manufacturers to design and produce engines 
that will be installed in motorcoaches with an alternative derate 
schedule that starts with a 65 mi/hr derate when a fault condition is 
first detected, steps down to 50 mi/hr after 80 hours, and concludes 
with a final derate speed of 25 mi/hr after 180 hours of non-idle 
operation. EPA is defining motorcoaches in 40 CFR 1036.801 to include 
buses that are designed to travel long distances with row seating for 
at least 30 passengers. This is intended to include charter services 
available to the general public.
    Comments on the proposed inducement policy ranged from

[[Page 4379]]

objecting to any speed restrictions to advocating that we adopt a 5 mph 
final derate speed. Some commenters supported the proposed rule, and 
some commenters asserted that decreasing final derate speeds would 
provide for greater assurance that operators would perform the 
necessary maintenance. There was a similar range of comments regarding 
the time specified for escalating the speed restrictions, with some 
commenters agreeing with the proposed schedule, and other commenters 
suggesting substantially more or less time.
    We made several changes from proposal after consideration of 
comments, including three main changes. First, as noted in the 
preceding paragraphs, the final rule includes a medium-speed vehicle 
category. This allows us to adjust the qualifying criterion for high-
speed vehicles to finalize a derate schedule similar to that proposed 
for vehicles that are clearly operating mostly on interstate highways 
over long distances. Similarly, the added vehicle category allows us to 
adjust the qualifying criterion for low-speed vehicles and adopt an 
appropriately more restrictive final derate schedule for those vehicles 
that are operating at lower speeds in local service.
    Second, we developed unique schedules for escalating the speed 
restrictions for medium-speed and low-speed vehicles; this change was 
based on the expectation that vehicles with lower average speeds spend 
less time operating at highway speeds characteristic of inter-city 
driving and will therefore not need to travel substantial distances to 
return home for scheduling repair.
    Third, we added derate speeds that go beyond the first four stages 
of derating that we proposed for high-speed vehicles, essentially 
reducing the final inducement speeds for all vehicles to be the same as 
low-speed vehicles. In other words, as shown in Table IV-13, both high- 
and medium-speed vehicles eventually derate to the same speeds as low-
speed vehicles, after additional transition time after the derate 
begins. For example, the final derate schedule for high-speed vehicles 
goes through the proposed four derate stages for high-speed vehicles. 
At the fifth derate stage the vehicle begins to be treated like a 
medium-speed vehicle, starting at the third derate stage for medium-
speed vehicles and progressing through the fifth derate stage for 
medium-speed vehicles. At the fifth derate stage the vehicle begins to 
be treated like a low-speed vehicle, similarly starting at the third 
derate stage for low-speed vehicles. A similar step-down approach 
applies for medium-speed vehicles, transitioning down to the derate 
stages for low-speed vehicles. This progression is intended to address 
the concern that vehicle owners might reassign vehicles in their fleet 
to lower-speed service, or sell vehicles to someone who would use the 
vehicle for different purposes that don't depend on higher-speed 
operations. Our assessment is that the NREL data show that no matter 
what category vehicles are, they do not travel exclusively at or below 
25 mph, indicating that vehicles derated to 25 mph cannot be operated 
commercially.
    For the simplest type of maintenance, DEF refills, we fully expect 
that the initial stage of derated vehicle speed will be sufficient to 
compel vehicle operators to meet their maintenance obligations. We 
expect operators will add DEF routinely to avoid inducements; however, 
inducements begin three hours prior to the DEF tank being empty to 
better ensure operation with an empty DEF tank is avoided.
    We expect that the derate schedules in this final rule will be 
fully effective in compelling operators to perform needed maintenance. 
This effectiveness will be comparable to the current approach under 
existing guidance, but will reduce operating costs to operators. We 
believe this measured approach will also result in lower tampering 
rates involving time.
3. Driver Information
    In addition to the driver information requirements we are adopting 
to improve serviceability and OBD (see section IV.B.3 and IV.C.1.iii 
respectively of this preamble for more details on these provisions), we 
are also adopting improved driver information requirements for 
inducements. Specifically, we are adopting as proposed the requirement 
for manufacturers to increase the amount of information provided to the 
driver about inducements, including: (1) The condition causing the 
derate (i.e., DEF quality, DEF quantity or tampering), (2) the fault 
code and description of the code associated with the inducement, (3) 
the current derate speed restriction, (4) hours until the next derate 
speed decrease, and (5) what the next derate speed will be. It is 
critical that operators have clear and ready access to information 
regarding inducements to reduce concerns over progressive engine 
derates (which can lead to motivations to tamper) as well as to allow 
operators to make timely informed decisions, especially since 
inducements are used by manufacturers to demonstrate that critical 
emissions-related maintenance is reasonably likely to occur in-use. We 
note that we are finalizing this requirement at 40 CFR 1036.110(c), in 
a different regulatory section than proposed; however, the substance of 
the requirement is the same as at proposal.
    EPA is requiring that all inducement-related diagnostic data 
parameters be made available with generic scan tools to help operators 
promptly respond when the engine detects fault condition requiring 
repair or other maintenance (see section IV.C.1.iii. for further 
information).
4. Clearing an Inducement Condition
    Following restorative maintenance, EPA is requiring that the engine 
would allow the vehicle to self-heal if it confirms that the fault 
condition is resolved. The engine would then remove the inducement, 
which would allow the vehicle to resume unrestricted engine operation. 
EPA is also requiring that generic scan tools be able to remove an 
inducement condition after a successful repair. After clearing 
inducement-related fault codes, all fault codes are subject to 
immediate reevaluation that would lead to resuming the derate schedule 
where it was at the time the codes were cleared if the fault persists. 
Therefore, there is no need to limit the number of times a scan tool 
can clear codes. Use of a generic scan tool to clear inducements would 
allow owners who repair vehicles outside of commercial facilities to 
complete the repair without delay (e.g., flushing and refilling a DEF 
tank where contaminated DEF was discovered). However, if the same fault 
condition repeats within 40 hours of engine operation (e.g., in 
response to a DEF quantity fault an owner adds a small but insufficient 
quantity of DEF), this will be considered a repeat faut. In response to 
a repeat fault, the system will immediately resume the derate at the 
same point in the derate schedule when the original fault was 
deactivated. This is less time than the 80 hours EPA proposed in the 
NPRM, but it is consistent with existing EPA guidance. After 
consideration of comments, we believe that the shorter interval is long 
enough to give a reliable confirmation that a repair has properly 
addressed the fault condition, and are concerned that 80 hours would 
risk treating an unrelated occurrence of a fault condition as if it 
were a continuation of the same fault.
    EPA is not finalizing the proposed provision that an inducement 
schedule is applied and tracked independently for each fault if 
multiple fault conditions are detected due to the software complexity 
for the

[[Page 4380]]

manufacturer in applying and tracking the occurrence of multiple derate 
schedules. Section 4 of the Response to Comments for further discussion 
of EPA's thinking to assist manufacturers regarding consideration for 
programming diagnostic systems to handle overlapping fault conditions.
5. Further Considerations
    EPA is not taking final action at this time on the proposed 
NOX override provision, which was proposed to prevent speed 
derates for fault conditions that are caused by component failures if 
the catalyst is nevertheless functioning normally. We received comments 
describing concerns with our proposed methodology, including the 
reliability of NOX sensors and use of OBD REAL 
NOX data, and concerns that reliance in this way on the 
NOX sensor could result in easier tampering. We are 
continuing to consider these issues and comments. We may consider such 
a provision in an appropriate future action. Our final inducement 
regulations will reduce the risk of false inducements and provide 
increased certainty during repairs by limiting inducements to well-
defined fault conditions that focus appropriately on DEF supply, DEF 
quality, and tampering (open-circuit faults associated with missing 
aftertreatment hardware).
    We have also learned from the last several years that it is 
important to monitor in-use experiences to evaluate whether the 
inducement provisions are striking the intended balance of ensuring an 
adequate supply of high-quality DEF in a way that is allowing for safe 
and timely resolution, even for cases involving difficult 
circumstances. For example, we might hypothetically learn from in-use 
experiences that component malfunctions, part shortages, or other 
circumstances are leaving operators in a place where inducements 
prevent them from operating and they are unable to perform maintenance 
that is needed to resolve the fault condition. Conversely, we might 
hypothetically learn that operators are routinely driving vehicles with 
active derates. Information from those in-use experiences may be 
helpful for future assessments of whether we should pursue adjustments 
to the derate schedules or other inducement provisions we are adopting 
in this final rule.
6. In-Use Retrofits To Update Existing Inducement Algorithms
    In the NPRM, we sought comment on whether it would be appropriate 
to allow engine manufacturers to modify earlier model year engines to 
align with the new regulatory specifications. We did not propose 
changes to existing regulations to address this concern. Specifically, 
we sought comment on whether and how manufacturers might use field-fix 
practices under EPA's field fix guidance to modify in-use engines with 
algorithms that incorporate some or all the inducement provisions in 
the final rule. We received numerous comments on the need to modify 
existing inducement speeds and schedules from operator groups and at 
least one manufacturer.\369\ We received comment on the use of field-
fixes for this purpose from CARB, stating that CARB staff does not 
support the SCR inducement strategy proposed by EPA and does not 
support allowing field fixes for in-use vehicles or to amend the 
certification application of current model year engines for the NPRM 
inducement strategy. CARB staff also commented that they would support 
allowing field fixes for in-use vehicles or amending current 
certification applications only if EPA adopts an inducement strategy 
identical or similar to the one CARB proposed in their comments on the 
proposed rule.\370\ For example, CARB suggested an inducement strategy 
with a 5 mph inducement after 10 hours, following an engine restart.
---------------------------------------------------------------------------

    \369\ See, for example, comments from the National Association 
of Small Trucking Companies, EPA-HQ-OAR-2019-0055-1130.
    \370\ See comments from California Air Resources Board, EPA-HQ-
OAR-2019-0055-1186.
---------------------------------------------------------------------------

    EPA believes field fixes with updated inducement algorithms may 
fall within EPA's field fix guidance for engines that have EPA-only 
certification (i.e., does not include certification to California 
standards), but has concerns about such field fixes falling within the 
scope of the guidance for engines also certified by CARB if CARB 
considers such changes to be tampering with respect to requirements 
that apply in California. EPA intends to also consider alternative 
field fix inducement approaches that manufacturers choose to develop 
and propose to CARB and EPA, for engines certified by both EPA and 
CARB, such as approaches that provide a more balanced inducement 
strategy than that used in current certifications while still being 
effective.

E. Fuel Quality

    EPA has long recognized the importance of fuel quality on motor 
vehicle emissions and has regulated fuel quality to enable compliance 
with emission standards. In 1993, EPA limited diesel sulfur content to 
a maximum of 500 ppm and put into place a minimum cetane index of 40. 
Starting in 2006 with the establishment of more stringent heavy-duty 
highway PM, NOX and hydrocarbon emission standards, EPA 
phased-in a 15-ppm maximum diesel fuel sulfur standard to enable heavy-
duty diesel engine compliance with the more stringent emission 
standards.\371\
---------------------------------------------------------------------------

    \371\ 66 FR 5002 January 18, 2001.
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    EPA continues to recognize the importance of fuel quality on heavy-
duty vehicle emissions and is not currently aware of any additional 
diesel fuel quality requirements necessary for controlling criteria 
pollutant emissions from these vehicles.
1. Biodiesel Fuel Quality
    As discussed in Chapter 2.3.2 of the RIA, metals (e.g., Na, K, Ca, 
Mg) can enter the biodiesel production stream and can adversely affect 
emission control system performance if not sufficiently removed during 
production. Our review of data collected by NREL, EPA, and CARB 
indicates that biodiesel is compliant with the ASTM D6751-18 limits for 
Na, K, Ca, and Mg. As we explained in the proposed rule, the available 
data does not indicate that there is widespread off specification 
biodiesel blend stock or biodiesel blends in the marketplace. We did 
not propose and are not including at this time in this final rule 
requirements for biodiesel blend metal content.
    While occasionally there are biodiesel blends with elevated levels 
of these metals, they are the exception. Data in the literature 
indicates that Na, K, Ca, and Mg levels in these fuels are less than 
100 ppb on average. Data further suggests that the low levels measured 
in today's fuels are not enough to adversely affect emission control 
system performance when the engine manufacturer properly sizes the 
catalyst to account for low-level exposure.
    Given the low levels measured in today's fuels, however, we are 
aware that ASTM is currently evaluating a possible revision to the 
measurement method for Na, K, Ca, and Mg in D6751-20a from EN14538 to a 
method that has lower detection limits (e.g., ASTM D7111-16, or a 
method based on the ICP-MS method used in the 2016 NREL study). We 
anticipate that ASTM will likely specify Na, K, Ca, and Mg limits in a 
future update to ASTM 7467-19 for B6 to B20 blends that is an 
extrapolation of the B100 limits (see RIA Chapter 2.3.2 for additional 
discussion of ASTM test methods, as well as available data on levels of 
metal in biodiesel and potential impacts on emission control systems).

[[Page 4381]]

2. Compliance Issues Related to Biodiesel Fuel Quality
    Given the concerns we raised in the ANPR and NPRM regarding the 
possibility of catalyst poisoning from metals contained in biodiesel 
blends and specifically heavy-duty vehicles fueled on biodiesel blends, 
and after consideration of comments on the NPRM, EPA is finalizing a 
process where we will consider the possibility that an engine was not 
properly maintained under the provisions of 40 CFR part 1068, subpart 
F, if an engine manufacturer demonstrates that the vehicle was 
misfueled in a way that exposed the engine and its aftertreatment 
components to metal contaminants and that misfueling degraded the 
emission control system performance. This allows a manufacturer to 
receive EPA approval to exempt test results from being considered for 
potential recall. For example, a manufacturer might request EPA 
approval through this process for a vehicle that was historically 
fueled on biodiesel blends whose B100 blend stock did not meet the ASTM 
D6751-20a limit for Na, K, Ca, and/or Mg (metals which are a byproduct 
of current biodiesel production methods). This process requires the 
engine manufacturer to provide proof of historic misfueling with off-
specification fuels; more specifically, to qualify for the test result 
exemption(s), a manufacturer must provide documentation that compares 
the degraded system to a representative compliant system of similar 
miles with respect to the content and amount of the contaminant. We are 
also finalizing a change from the proposal in the fuel requirements 
relevant to conducting in-use testing and to recruitment of vehicles 
for in-use testing. The new provision in 40 CFR 1036.415(c)(1) states 
that the person conducting the in-use testing may use any commercially 
available biodiesel fuel blend that meets the specifications for ASTM 
D975 or ASTM D7467 that is either expressly allowed or not otherwise 
indicated as an unacceptable fuel in the vehicle's owner or operator 
manual or in the engine manufacturer's published fuel recommendations. 
As specified in final 40 CFR 1036.410, if the engine manufacturer finds 
that the engine was fueled with fuel not meeting the specifications in 
40 CFR 1036.415(c)(1), they may disqualify the vehicle from in-use 
testing and replace it with another one.

F. Durability Testing

    In this section, we describe the final deterioration factor (DF) 
provisions for heavy-duty highway engines, including migration and 
updates from their current location in 40 CFR 86.004-26(c) and (d) and 
86.004-28(c) and (d) to 40 CFR 1036.245 and 1036.246. EPA regulations 
require that a heavy-duty engine manufacturer's application for 
certification include a demonstration that the engines will meet 
applicable emission standards throughout their regulatory useful life. 
This is often called the durability demonstration. Manufacturers 
typically complete this demonstration by following regulatory 
procedures to calculate a DF. Deterioration factors are additive or 
multiplicative adjustments applied to the results from manufacturer 
testing to quantify the emissions deterioration over useful life.\372\
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    \372\ See 40 CFR 1036.240(c) and the definition of 
``deterioration factor'' in 40 CFR 1036.801, which, as proposed, are 
migrated and updated from 40 CFR 86.004-26 and 86.004-28 in this 
final rule.
---------------------------------------------------------------------------

    Currently, a DF is determined directly by aging an engine and 
exhaust aftertreatment system to useful life on an engine dynamometer. 
This time-consuming service accumulation process requires manufacturers 
to commit to product configurations well ahead of their pre-production 
certification testing to complete the durability testing so EPA can 
review the test results before issuing the certificate of conformity. 
Some manufacturers run multiple, staggered durability tests in parallel 
in case a component failure occurs that may require a complete restart 
of the aging process.\373\
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    \373\ See 40 CFR 1065.415.
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    As explained in the NPRM, EPA recognizes that durability testing 
over a regulatory useful life is a significant undertaking, which can 
involve more than a full year of continuous engine operation for Heavy 
HDE to test to the equivalent of the current useful life of 435,000 
miles. Manufacturers have been approved, on a case-by-case basis, to 
age their systems to between 35 and 50 percent of the current full 
useful life on an engine dynamometer, and then extrapolate the test 
results to full useful life.\374\ This extrapolation reduces the time 
to complete the aging process, but data from a test program shared with 
EPA show that while engine out emissions for SCR-equipped engines were 
predictable and consistent, actual tailpipe emission levels were higher 
by the end of useful life when compared to emission levels extrapolated 
to useful life from service accumulation of 75 or lower percent useful 
life.375 376 In response to the new data indicating DFs 
generated by manufacturers using service accumulation less than useful 
life may not be fully representative of useful life deterioration, EPA 
initially worked with manufacturers and CARB to address this concern 
through guidance for MY 2020 and later engines.
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    \374\ See 40 CFR 86.004-26.
    \375\ U.S. EPA. ``Guidance on Deterioration Factor Validation 
Methods for Heavy-Duty Diesel Highway Engines and Nonroad Diesel 
Engines equipped with SCR.'' CD-2020-19 (HD Highway and Nonroad). 
November 17, 2020.
    \376\ Truck and Engine Manufacturers Association. ``EMA DF Test 
Program.'' August 1, 2017.
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    While the current DF guidance is specific to SCR-equipped engines, 
in this final rule we are updating our DF provisions to apply certain 
aspects of the current DF guidance to all engine families starting in 
model year 2027.\377\ We also are finalizing as proposed that 
manufacturers may optionally use these provisions to determine their 
deterioration factors for earlier model years. As noted in the 
following section, as proposed, we are continuing the option for Spark-
ignition HDE manufacturers to request approval of an accelerated aging 
DF determination, as is allowed in our current regulations (see 40 CFR 
86.004-26(c)(2)), and our final provision extends this option to all 
primary intended service classes. We are not finalizing any changes to 
the existing compliance demonstration provision in 40 CFR 1037.103(c) 
for evaporative and refueling emission standards. As introduced in 
Section III.E, in this rule we are also promulgating refueling emission 
standards for incomplete vehicles above 14,000 lb GVWR. As proposed, we 
are finalizing that incomplete vehicle manufacturers certifying to the 
refueling emission standards for the first time have the option to use 
engineering analyses to demonstrate durability using the same 
procedures that apply for the evaporative systems on their vehicles 
today.
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    \377\ As noted in Section III.A, the final update to the 
definition of ``engine configuration'' in 40 CFR 1036.801, as 
proposed, clarifies that hybrid engines and powertrains are part of 
a certified configuration and subject to all of the criteria 
pollutant emission standards and other requirements; thus the DF 
provisions for heavy-duty engines discussed in this subsection will 
apply to configurations that include hybrid components.
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    In Section IV.F.1, we are finalizing two methods for determining 
DFs in a new 40 CFR 1036.245 with some modifications from those 
proposed, including a new option to bench-age the aftertreatment system 
to limit the burden of generating a DF over the lengthened useful life 
periods in Section IV.A.3. We are also codifying two DF verification 
options available to

[[Page 4382]]

manufacturers in the recent DF guidance, with some modifications from 
our proposed DF verification requirements. As described in Section 
IV.F.2, under the final 40 CFR 1036.245 and 40 CFR 1036.246, the final 
provisions include two options for DF verification to confirm the 
accuracy of the DF values submitted by manufacturers for certification, 
and will be required upon request from EPA. In Section IV.F.3, we 
introduce a test program to evaluate a rapid-aging protocol for diesel 
catalysts, the results of which we used to develop a rapid-aging test 
procedure for CI engine manufacturers to be able to use in their 
durability demonstration under 40 CFR 1036.245(c)(6). We are finalizing 
this procedure in 40 CFR part 1065, subpart L, as new sections 40 CFR 
1065.1131 through 40 CFR 1065.1145.
    At this time we are not finalizing any additional testing 
requirements for manufacturers to demonstrate durability of other key 
components included in a hybrid configuration (e.g., battery durability 
testing). We will consider additional requirements in a future rule as 
we pursue other durability-related provisions for EVs, PHEVs, etc.
    As described in Section XI.A.8, we are also finalizing as proposed 
that manufacturers of nonroad engines may use the procedures described 
in this section to establish deterioration factors based on bench-aged 
aftertreatment, along with any EPA-requested in-use verification 
testing.
1. Options for Determining Deterioration Factor
    Accurate methods to demonstrate emission durability are key to 
ensuring certified emission levels represent real world emissions, and 
the efficiency of those methods is especially important in light of the 
lengthening of useful life periods in this final rule. To address these 
needs, we are migrating our existing regulatory option from part 86 to 
part 1036 and including a new option for heavy-duty highway engine 
manufacturers to determine DFs for certification. We note that 
manufacturers apply these deterioration factors to determine whether 
their engines meet the duty cycle standards.
    Consistent with existing regulations, final 40 CFR 1036.245 allows 
manufacturers to continue the current practice of determining DFs based 
on engine dynamometer-based aging of the complete engine and 
aftertreatment system out to regulatory useful life. In addition, under 
the new DF determination option, which includes some modifications from 
that proposed and which are described in this section, manufacturers 
perform dynamometer testing of an engine and aftertreatment system to a 
minimum required mileage that is less than regulatory useful life. 
Manufacturers then bench age the aftertreatment system to regulatory 
useful life and combine the aftertreatment system with an engine that 
represents the engine family. Manufacturers run the combined engine and 
bench-aged aftertreatment for at least 100 hours before collecting 
emission data for determination of the deterioration factor. Under this 
option, the manufacturer can use the accelerated bench-aging of diesel 
aftertreatment procedure described in Section IV.F.3 that is codified 
in the new sections 40 CFR 1065.1131 through 40 CFR 1065.1145 or 
propose an equivalent bench-aging procedure and obtain prior approval 
from the Agency. For example, a manufacturer might propose a different, 
established bench-aging procedure for other engines or vehicles (e.g., 
procedures that apply for light-duty vehicles under 40 CFR part 86, 
subpart S).
    We requested comment on whether the new bench-aged aftertreatment 
option accurately evaluates the durability of the emission-related 
components in a certified configuration, including the allowance for 
manufacturers to define and seek approval for a less-than-useful life 
mileage for the dynamometer portion of the bench-aging option. This 
request for comment specifically included whether or not there is a 
need to define a minimum number of engine hours of dynamometer testing 
beyond what is required to stabilize the engine before bench-aging the 
aftertreatment, noting that EPA's bench-aging proposal focused on 
deterioration of emission control components.\378\ We requested comment 
on including a more comprehensive durability demonstration of the whole 
engine, such as the recent diesel test procedures from CARB's Omnibus 
regulation that includes dynamometer-based service accumulation of 
2,100 hours or more based on engine class and other factors.\379\ We 
also requested comment on whether EPA should prescribe a standardized 
aging cycle for the dynamometer portion, as was done by CARB in the 
Omnibus rule with their Service Accumulation Cycles 1 and 2.\380\ We 
also requested cost and time data corresponding to the current DF 
procedures, and projections of cost and time for the proposed new DF 
options at the proposed new useful life mileages.
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    \378\ We are updating, as proposed, the definition of ``low-
hour'' in 40 CFR 1036.801 to include 300 hours of operation for 
engines with NOX aftertreatment to be considered 
stabilized.
    \379\ California Air Resources Board, '' Appendix B-1 Proposed 
30-Day Modifications to the Diesel Test Procedures'', May 5, 2021, 
Available online: https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2020/hdomnibuslownox/30dayappb1.pdf, page 54.
    \380\ California Air Resources Board, ``Staff Report: Initial 
Statement of Reasons for Proposed Rulemaking, Public Hearing to 
Consider the Proposed Heavy-duty Engine and Vehicle Omnibus 
Regulation and Associated Amendments,'' June 23, 2020. Available 
online: https://ww3.arb.ca.gov/regact/2020/hdomnibuslownox/isor.pdf, 
page III-80.
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    Some commentors supported the removal of the fuel-based accelerated 
DF determination method, noting that it has been shown to underestimate 
emission control system deterioration. Other commentors requested that 
EPA retain the option, noting that it has been historically allowed. 
Fuel-based accelerated aging accelerates the service accumulation using 
higher-load operation based on equivalent total fuel flow on a 
dynamometer. The engine is only operated out to around 35 percent of UL 
based on operating hours, however the high-load operation is intended 
to result in an equivalent aging out to full UL. EPA has assessed data 
from the EMA DF test program and determined that the data indicated 
that the aging mechanism of accelerating the aging at higher load 
differs from the actual in-use deterioration 
mechanism.381 382 We are not including this option in the 
final provisions for determining DF based on our assessment of the 
available data and have removed the option in final 40 CFR 1036.245.
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    \381\ U.S. EPA. ``Guidance on Deterioration Factor Validation 
Methods for Heavy-Duty Diesel Highway Engines and Nonroad Diesel 
Engines equipped with SCR.'' CD-2020-19 (HD Highway and Nonroad). 
November 17, 2020.
    \382\ Truck and Engine Manufacturers Association. ``EMA DF Test 
Program.'' August 1, 2017.
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    We also received general support of the use of accelerated aging 
cycles to manage the total cost and duration of the DF test, in 
addition to some commenters stating that the CARB DF determination 
procedure in the CARB Omnibus regulation is superior to the accelerated 
aging procedure EPA proposed in 40 CFR 1036.245(b)(2). The required 
hours of engine dynamometer aging in the CARB Omnibus procedure 
(roughly out to 20 percent of UL for a HHD engine) provide limited 
assurance on the performance of engine components out to UL, and thus 
primarily provide a short-term quality assurance durability program for 
engine hardware. While the purpose of EPA's DF determination procedure 
is to

[[Page 4383]]

determine emission performance degradation over the useful life of the 
engine, we acknowledge that there is value in performing some engine 
dynamometer aging. We are finalizing an option to use accelerated 
reactor bench-aging of the emission control system that is ten times a 
dynamometer or field test (1,000 hours of accelerated aging would be 
equivalent to 10,000 hours of standard aging), requiring a minimum 
number of testing hours on an engine dynamometer, with the allowance 
for the manufacturer to add additional hours of engine dynamometer-
aging at their discretion. The minimum required hours are by primary 
intended service class and follow: 300 hours for SI, 1,250 hours for 
Light HDE, and 1,500 hours for Medium HDE and Heavy HDE. This option 
allows the DF determination to be completed within a maximum of 180 
days for a Heavy HDE. We recognize that a different approach, that uses 
the same aging duty-cycle for all manufacturers, would provide more 
consistency across engine manufacturers. However, no data was provided 
by commentors showing that the Service Accumulation Cycles 1 and 2 in 
the CARB Omnibus rule are any more effective at determining 
deterioration than cycles developed by the manufacturer and submitted 
to EPA for approval. EPA is also concerned regarding the amount of idle 
contained in each of the CARB Omnibus rule cycles. We realize that this 
idle operation was included to target the degradation mechanism that 
plagued the SAPO-34 SCR formulations used by manufacturers in the 
2010s, however the catalyst developers are aware of this issue now and 
have developed formulations that are free from this degradation 
mechanism. The two most predominant degradation mechanisms are time at 
high temperature and sulfur exposure, including the effects of catalyst 
desulfation, and as such EPA favors duty-cycles with more aggressive 
aftertreatment temperature profiles. We understand that catalyst 
manufacturers now bench test the catalyst formulations under the 
conditions that led to the SAPO-34 degradation to ensure that this 
degradation mechanism is not present in newly developed SCR 
formulations. After taking all of the comments received into 
consideration, EPA has added two specified duty-cycle options in 40 CFR 
1036.245(c) for DF determination, that are identical to CARB's Service 
Accumulation Cycles 1 and 2. Cycle 1 consists of a combination of FTP, 
RMC, LLC and extended idle, while Cycle 2 consists of a combination of 
HDTT, 55-cruise, 65-cruise, LLC, and extended idle. In the case of the 
second option, the manufacturer is required to use good engineering 
judgment to choose the vehicle subcategory and vehicle configuration 
that yields the highest load factor using the GEM model. EPA is also 
providing an option for manufacturers to use their own duty cycles for 
DF determination subject to EPA approval and we expect a manufacturer 
to include light-load operation if it is deemed to contribute to 
degradation of the aftertreatment performance. We also note that we are 
finalizing requirements to stop, cooldown, and restart the engine 
during service accumulation when using the options that correspond to 
CARB Service Accumulation Cycles 1 and 2 for harmonization purposes, 
however we note that manufacturers may make a request to EPA to remove 
this requirement on a case-by-case basis.
    We are finalizing critical emission-related maintenance as 
described in 40 CFR 1036.125(a)(2) and 1036.245(c) in this final rule. 
Under this final rule, manufacturers may make requests to EPA for 
approval for additional emission-related maintenance actions beyond 
what is listed in 40 CFR 1036.125(a)(2), as described in 40 CFR 
1036.125(a)(1) and as allowed during deterioration testing under 40 CFR 
1036.245(c).
2. Options for Verifying Deterioration Factors
    We are finalizing, with some modifications from proposal, a new 40 
CFR 1036.246 where, at EPA's request, the manufacturers would be 
required to verify an engine family's deterioration factor for each 
duty cycle up to 85 percent of useful life. Because the manufacturer 
must comply with emission standards out to useful life, we retain the 
authority to verify DF. We proposed requiring upfront verification for 
all engine families, but have decided to make this required only in the 
event that EPA requests verification. We intend to make such a request 
primarily when EPA becomes aware of information suggesting that there 
is an issue with the DF generated by the manufacturer. EPA anticipates 
that a DF verification request may be appropriate due to consideration 
of, for example: (1) Information indicating that a substantial number 
of in-use engines tested under subpart E of this part failed to meet 
emission standards, (2) information from any other test program or any 
other technical information indicating that engines will not meet 
emission standards throughout the useful life, (3) a filed defect 
report relating to the engine family, (4) a change in the technical 
specifications for any critical emission-related components, and (5) 
the addition of a new or modified engine configuration such that the 
test data from the original emission-data engine do not clearly 
continue to serve as worst-case testing for certification. We are 
finalizing as proposed that manufacturers may request use of an 
approved DF on future model year engines for that engine family, using 
the final updates to carryover engine data provisions in 40 CFR 
1036.235(d), with the final provision clarifying that we may request DF 
verification for the production year of that new model year as 
specified in the new 40 CFR 1036.246. As also further discussed in the 
following paragraphs, we are not finalizing at this time certain DF 
verification provisions that we had proposed regarding timing of when 
EPA may request DF verification and certain provisions for the first 
model year after a failed result. Our revisions from proposal 
appropriately provide flexibility for EPA to gather information based 
on DF concerns. The final provisions specify that we will discuss with 
the manufacturer the selection criteria for vehicles with respect to 
the target vehicle mileage(s) and production model year(s) that we want 
the manufacturer to test. We are finalizing that we will not require 
the manufacturer to select vehicles whose mileage or age exceeds 10 
years or 85 percent of useful life.
    We originally included three testing options in our proposed DF 
verification provisions. We are finalizing two of these options and we 
are not including the option to verify DF by measuring NOX 
emissions using the vehicle's on-board NOX measurement 
system at this time. For the two options we are finalizing, 
manufacturers select in-use engines meeting the criteria in 40 CFR 
1036.246(a), including the appropriate mileage specified by EPA 
corresponding to the production year of the engine family.
    Under the first verification option in 40 CFR 1036.246(b)(1), 
manufacturers test at least two in-use engines over all duty cycles 
with brake-specific emission standards in 40 CFR 1036.104(a) by 
removing each engine from the vehicle to install it on an engine 
dynamometer and measure emissions. Manufacturers determine compliance 
with the emission standards after applying infrequent regeneration 
adjustment factors to their measured results, just as they did when 
they originally certified the engine family. We are also finalizing a 
requirement under this option to allow EPA to request that 
manufacturers

[[Page 4384]]

perform a new determination of infrequent regeneration adjustment 
factors to apply to the emissions from the engine dynamometer-based 
testing. Consistent with the proposal, the engine family passes the DF 
verification if 70 percent or more of the engines tested meet the duty-
cycle emission standards in 40 CFR 1036.104(a), including any 
associated compliance allowance, for each pollutant over all duty 
cycles. If a manufacturer chooses to test two engines under this 
option, both engines have to meet the standards. Under this option, the 
aftertreatment system, including all the associated wiring, sensors, 
and related hardware or software is installed on the test engine. We 
are finalizing an allowance in 40 CFR 1036.246(a) for the manufacturer 
to use hardware or software in testing that differs from those used for 
engine family and power rating with EPA approval.
    Under the second verification option in 40 CFR 1036.246(b)(2), as 
proposed, manufacturers test at least five in-use engines, to account 
for the increased variability of vehicle-level measurement, while 
installed in the vehicle using a PEMS. Manufacturers bin and report the 
emissions following the in-use testing provisions in 40 CFR part 1036, 
subpart E. Compliance is determined by comparing emission results to 
the off-cycle emission standards in 40 CFR 1036.104(a) with any 
associated compliance allowance, mean ambient temperature adjustment, 
and, accuracy margin for each pollutant for each bin after adjusting 
for infrequent regeneration.\383\ As proposed, the engine family passes 
the DF verification if 70 percent or more of the engines tested meet 
the off-cycle standards for each pollutant for each bin. In the event 
that EPA requested DF verification and a DF verification fails under 
the PEMS option, consistent with the proposal the manufacturer can 
reverse a fail determination for the PEMS-based testing and verify the 
DF using the engine dynamometer testing option in 40 CFR 
1036.246(b)(1).
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    \383\ For Spark-ignition HDE, we are not finalizing off-cycle 
standards; however, for the in-use DF verification options, a 
manufacturer compares the engine's emission results to the duty 
cycle standards applying a 1.5 multiplier for model years 2027 and 
later.
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    EPA is not including the third option we proposed, to verify DF 
using the vehicle's on-board NOX measurement system (i.e., a 
NOX sensor), in the final provisions, as we have concerns 
that the technology has not matured enough to make this method viable 
for DF verification at this time. We did not receive any comments that 
supported the availability of technology to enable accurate on-board 
NOX measurement at a level needed to show compliance with 
the standard. EPA acknowledges the challenges associated with the 
development of a functional onboard NOX measurement method, 
including data acquisition and telematic system capabilities, and may 
reconsider this option in the future if the technology evolves.
    As noted in the preceding paragraphs, we are not taking final 
action at this time on the proposed 40 CFR 1036.246(h) provision that 
proposed a process for the first MY after a DF verification resulted in 
failure. Instead, we are adopting a process for DF verification 
failures similar to the existing process used for manufacturer run in-
use testing failures under 40 CFR part 1036, subpart E, such that a 
failure may result in an expanded discovery process that could 
eventually lead to recall under our existing provisions in 40 CFR part 
1068, subpart F. EPA is making this change from proposal because this 
approach provides consistency with and builds upon existing processes.
    The final 40 CFR 1036.246(a) specifies how to select and prepare 
engines for testing. Manufacturers may exclude selected engines from 
testing if they have not been properly maintained or used and the 
engine tested must be in a certified configuration, including its 
original aftertreatment components. Manufacturers may test engines that 
have undergone critical emission-related maintenance as allowed in 40 
CFR 1065.410(d), but may not test an engine if its critical emission-
related components had any other major repair.
3. Accelerated Deterioration Factor Determination
    As discussed in Section IV.F.1, we are finalizing a deterioration 
factor procedure where manufacturers use engine dynamometer testing for 
the required minimum number of hours given in Table 1 to Paragraph 
(c)(2) of 40 CFR 1036.245 in combination with an accelerated 
aftertreatment catalyst aging protocol in their demonstration of heavy-
duty diesel engine aftertreatment durability through useful life. EPA 
has approved accelerated aging protocols for spark-ignition engine 
manufacturers to apply in their durability demonstrations for many 
years. Historically, while CI engine manufacturers have the ability to 
request EPA approval of an accelerated aging procedure, CI engine 
manufacturers have largely opted to seek EPA approval to use a service 
accumulation fuel based accelerated test with reduce mileage and 
extrapolate to determine their DF.
    Other regulatory agencies have promulgated accelerated aging 
protocols,384 385 and we have evaluated how these or similar 
protocols apply to our heavy-duty highway engine compliance program. 
EPA has validated and is finalizing an accelerated aging procedure in 
40 CFR part 1065, subpart L, as new sections 40 CFR 1065.1131 through 
40 CFR 1065.1145 that CI engine manufacturers can choose to use in lieu 
of developing their own protocol as described in 40 CFR 1036.245. The 
test program that validated the diesel aftertreatment rapid-aging 
protocol (DARAP) was built on existing accelerated aging protocols 
designed for light-duty gasoline vehicles (64 FR 23906, May 4, 1999) 
and heavy-duty engines.\386\
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    \384\ California Air Resources Board. California Evaluation 
Procedure For New Aftermarket Diesel Particulate Filters Intended As 
Modified Parts For 2007 Through 2009 Model Year On-Road Heavy-Duty 
Diesel Engines, March 1, 2017. Available online: https://ww3.arb.ca.gov/regact/2016/aftermarket2016/amprcert.pdf.
    \385\ European Commission. Amending Regulation (EU) No 583/2011, 
20 September 2016. Available online: https://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32016R1718&from=HU.
    \386\ Eakle, S and Bartley, G (2014), ``The DAAAC Protocol for 
Diesel Aftertreatment System Accelerated Aging''.
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i. Diesel Aftertreatment Rapid Aging Protocol
    The objective of the DARAP validation program was to artificially 
recreate the three primary catalytic deterioration processes observed 
in field-aged aftertreatment components: Thermal aging based on time at 
high temperature, chemical aging that accounts for poisoning due to 
fuel and oil contamination, and deposits. The validation program had 
access to three baseline engines that were field-aged to the model year 
2026 and earlier useful life of 435,000 miles. Engines and their 
corresponding aftertreatment systems were aged using the current, 
engine dynamometer-based durability test procedure for comparison of 
the results to the accelerated aging procedure. We performed 
accelerated aging of the catalyst-based aftertreatment systems using 
two different methods with one utilizing a burner \387\ and the other 
using an engine as the source of aftertreatment aging conditions. The 
validation test plan compared emissions at the following approximate 
intervals: 0 percent, 25 percent, 50 percent, 75 percent, and 100 
percent of the model year 2026 and earlier useful life of 435,000 
miles. At proposal, we included

[[Page 4385]]

additional details of our DARAP test program in a memo to the 
docket.\388\
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    \387\ A burner is a computer controlled multi-fuel reactor 
designed to simulate engine aging conditions.
    \388\ Memorandum to Docket EPA-HQ-OAR-2019-0055: ``Diesel 
Aftertreatment Rapid Aging Program''. George Mitchell. May 5, 2021.
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    The DARAP validation program has completed testing of two rapidly 
aged aftertreatment systems, engine and burner, and two engines, a 
single FUL aged engine and a 300-hour aged engine. Our memo to the 
docket includes a summary of the validation results from this program. 
The results show that both accelerated aging pathways, burner and 
engine, produced rapidly aged aftertreatment system results that were 
not statistically significant when compared to the 9,800-hour 
dynamometer aged reference system. We are currently completing 
postmortem testing to evaluate the deposition of chemical poisoning on 
the surface of the substrates to see how this compares to the 
dynamometer aged reference system. The complete results from our 
validation program are contained in a final report in the docket.\389\
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    \389\ Sharp, C. (2022). Demonstration of Low NOX 
Technologies and Assessment of Low NOX Measurements in 
Support of EPA's 2027 Heavy Duty Rulemaking. Southwest Research 
Institute. Final Report EPA Contract 68HERC20D0014.
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ii. Diesel Aftertreatment Accelerated Aging Test Procedure
    The final provisions include an option for manufacturers to use the 
method from the DARAP test program for DF determination and streamline 
approval under 40 CFR 1036.245(c). This accelerated aging method we are 
finalizing in 40 CFR part 1065, subpart L, as new sections 40 CFR 
1065.1131 through 40 CFR 1065.1145 is a protocol for translating field 
data that represents a given application (e.g., engine family) into an 
accelerated aging cycle for that given application, as well as methods 
for carrying out reactor or engine accelerated aging using that cycle. 
While this testing can be carried out on an engine as well as reactor 
bench, the engine option should not be confused with standard engine 
dynamometer aging out to useful life or the historic fuel-based engine 
dynamometer accelerated aging typically done out to 35 percent of 
useful life approach that EPA will no longer allow under this final 
rule. The engine option in this procedure uses the engine (1) as a 
source of accelerated sulfur from the combusted fuel, (2) as a source 
for exhaust gas, and (3) to generate heat. The catalyst poisoning 
agents (oil and sulfur) as well as the temperature exposure are the 
same between the two methods and the DARAP test program data 
corroborates this. This protocol is intended to be representative of 
field aging, includes exposure to elements of both thermal and chemical 
aging, and is designed to achieve an acceleration of aging that is ten 
times a dynamometer or field test (1,000 hours of accelerated aging 
would be equivalent to 10,000 hours of standard aging).
    The initial step in the method requires the gathering and analysis 
of input field data that represent a greater than average exposure to 
potential field aging factors. The field aging factors consist of 
thermal, oil, and sulfur exposure. The thermal exposure is based on the 
average exhaust temperature; however, if the engine family incorporates 
a periodic infrequent regeneration event that involves exposure to 
higher temperatures than are observed during normal (non-regeneration) 
operation, then this temperature is used. Oil exposure is based on 
field and laboratory measurements to determine an average rate of oil 
consumption in grams per hour that reaches the exhaust. Sulfur exposure 
is based on the sum of fuel- and oil-related sulfur consumption rates 
for the engine family. The procedure provides details on how to gather 
data from field vehicles to support the generation and analysis of the 
field data.
    Next, the method requires determination of key components for 
aging. Most diesel aftertreatment systems contain multiple catalysts, 
each with their own aging characteristics. This accelerated aging 
procedure ages the system, not component-by-component. Therefore, it is 
necessary to determine which catalyst components are the key components 
that will be used for deriving and scaling the aging cycle. This 
includes identification of the primary and secondary catalysts in the 
aftertreatment system, where the primary is the catalyst that is 
directly responsible for most of the NOX reduction, such as 
a urea SCR catalyst in a compression-ignition aftertreatment system. 
The secondary is the catalyst that is intended to either alter exhaust 
characteristics or generate elevated temperature upstream of the 
primary catalyst, such as a DOC placed upstream of an SCR catalyst, 
with or without a DPF in between.
    The next step in the process is to determine the thermal 
deactivation rate constant(s) for each key component. This is used for 
the thermal heat load calculation in the accelerated aging protocol. 
The calculations for thermal degradation are based on the use of an 
Arrhenius rate law function to model cumulative thermal degradation due 
to heat exposure. The process of determining the thermal deactivation 
rate constant begins with determining what catalyst characteristic will 
be tracked as the basis for measuring thermal deactivation. Generally, 
ammonia storage is the key aging metric for zeolite-based SCR 
catalysts, NOX reduction efficiency at low temperature for 
vanadium-based SCR catalysts, conversion rate of NO to NO2 
for DOCs with a downstream SCR catalyst, and HC reduction efficiency 
(as measured using ethylene) at 200 [deg]C for DOCs where the 
aftertreatment system does not contain an SCR catalyst for 
NOX reduction. Thermal degradation experiments are then 
carried out over at least three different temperatures that accelerate 
thermal deactivation such that measurable changes in the aging metric 
can be observed at multiple time points over the course of no more than 
50 hours. During these experiments it is important to void temperatures 
that are too high to prevent rapid catalyst failure by a mechanism that 
does not represent normal aging.
    Generation of the accelerated aging cycle for a given application 
involves analysis of the field data to determine a set of aging modes 
that will represent that field operation. There are two methods of 
cycle generation in 40 CFR 1065.1139, each of which is described 
separately. Method 1 involves the direct application of field data and 
is used when the recorded data includes sufficient exhaust flow and 
temperature data to allow for determination of aging conditions 
directly from the field data set. Method 2 is meant to be used when 
insufficient flow and temperature data is available from the field 
data. In Method 2, the field data is used to weight a set of modes 
derived from the laboratory certification cycles for a given 
application. These weighted modes are then combined with laboratory 
recorded flow and temperatures on the certification cycles to derive 
aging modes. There are two different cases to consider for aging cycle 
generation, depending on whether or not a given aftertreatment system 
incorporates the use of a periodic regeneration event. For the purposes 
of cycle generation, a regeneration is any event where the operating 
temperature of some part of the aftertreatment system is raised beyond 
levels that are observed during normal (non-regeneration) operation. 
The analysis of regeneration data is considered separately from normal 
operating data.
    The process of cycle generation begins with the determination of 
the number of bench aging hours. The input into this calculation is the 
number of real or field

[[Page 4386]]

hours that represent the useful life for the target application. The 
target for the accelerated aging protocol is a 10-time acceleration of 
the aging process, therefore the total number of aging hours is set at 
service accumulation hours minus required engine dynamometer aging 
hours divided by 10. The hours will then be among different operating 
modes that will be arranged to result in repetitive temperature cycling 
over that period. For systems that incorporate periodic regeneration, 
the total duration will be split between regeneration and normal (non-
regeneration) operation. The analysis of the operation data develops a 
reduced set of aging modes that represent normal operation using either 
Method 1 or Method 2. Method 1 is a direct clustering method and 
involves three steps: Clustering analysis, mode consolidation, and 
cycle building.\390\ This method is used when sufficient exhaust flow 
and temperature data are available directly from the field data. Method 
2 is a cluster-based weighting of certification cycle modes when there 
is insufficient exhaust flow and temperature data from the field at the 
time the cycle is being developed. The initial candidate mode 
conditions are temperature and flow rate combinations that are the 
centroids from the analysis of each cluster.
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    \390\ https://documentation.sas.com/doc/en/emref/14.3/
n1dm4owbc3ka5jn11yjkod7ov1va.htm#:~:text=The%20cubic%20clustering%20c
riterion%20(CCC,evaluated%20by%20Monte%20Carlo%20methods.
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    The target for accelerated aging cycle operation is to run all the 
regenerations that would be expected over the course of useful life and 
the procedure provides a process for determining a representative 
regeneration profile that will be used during aging. Heat load 
calculation and cycle tuning are performed after the preliminary cycles 
have been developed for both normal and regeneration operation. The 
target cumulative deactivation is determined from the input field data, 
and then a similar calculation is performed for the preliminary aging 
cycle. If the cumulative deactivation for the preliminary cycle does 
not match cumulative deactivation from the field data, then the cycle 
is tuned over a series of steps described in 40 CFR 1065.1139 until the 
target is matched.
    The final assembly of the candidate accelerated aging cycle 
involves the assembly of the target modes into a schedule of modes laid 
out on a time basis that can be repeated until the target number of 
aging hours has been reached. For cycles that incorporate periodic 
regeneration modes, the regeneration frequency and duration, including 
any regeneration extension added to reach thermal targets, will be used 
to determine the length of the overall cycle. The number of these 
cycles that is run is equal to the total number of regenerations over 
full useful life. The duration of each cycle is total number of 
accelerated aging hours divided by the total number of regenerations. 
For multiple components with differing regeneration schedules, this 
calculation is performed using the component with the fewest total 
number of regenerations. The regeneration events for the more 
frequently regenerating components should be spaced evenly throughout 
each cycle to achieve the appropriate regeneration frequency and 
duration.
    The regeneration duration (including extension) is then subtracted 
from the base cycle duration to calculate the duration of normal (non-
regeneration) operation in seconds. This time is split among the normal 
(non-regeneration) modes in proportion to the overall target aging time 
in each mode. These modes are then split and arranged to achieve the 
maximum thermal cycling between high and low temperatures. No mode may 
have a duration shorter than 900 seconds, not including transition 
time. Mode transitions must be at least 60 seconds long and must be no 
longer than 300 seconds. The transition period is considered complete 
when you are within 5 [deg]C of the target temperature for the primary 
key component. For modes longer than 1800 seconds, you may count the 
transition time as time in mode. For modes shorter than 1800 seconds, 
under the procedure you must not count the transition time as time in 
mode. Modes are arranged in alternating order starting with the lowest 
temperature mode and proceeding to the highest temperature mode, 
followed by the next lowest temperature mode, and so forth.
    The final cycle is expressed as a schedule of target temperature, 
exhaust flow rate, and NOX. For a burner-based platform with 
independent control of these parameters, this cycle can be used 
directly. For an engine-based platform, it is necessary to develop a 
schedule of speed and load targets that will produce the target exhaust 
conditions based on the capabilities of the engine platform.
    The accelerated oil consumption target is calculated at 10 times 
the field average oil consumption that was determined from the field 
data and/or laboratory measurements. Under the procedure, this oil 
consumption rate must be achieved on average over the aging cycle, and 
it must at least be performed during all non-regeneration modes. Under 
the procedure, the lubricating oil chosen must meet the normal in-use 
specifications and it cannot be altered. The oil is introduced by two 
pathways, a bulk pathway and a volatile pathway. The bulk pathway 
involves introduction of oil in a manner that represents oil passing 
the piston rings, and the volatile pathway involves adding small amount 
of lubricating oil to the fuel. Under the procedure, the oil introduced 
by the volatile pathway must be between 10 percent and 30 percent of 
the total accelerated oil consumption.
    Sulfur exposure related to oil is already taken care of via 
acceleration of the oil consumption itself. The target cumulative fuel 
sulfur exposure is calculated using the field recorded average fuel 
rate data and total field hours assuming a 10-ppm fuel sulfur level 
(which was determined as the 90th percentile of available fuel survey 
data).
    For an engine-based accelerated aging platform where the engine is 
used as the exhaust gas source, accelerated fuel sulfur is introduced 
by increasing the fuel sulfur level. The cycle average fuel rate over 
the final aging cycle is determined once that target modes have been 
converted into an engine speed and load schedule. The target aging fuel 
sulfur level that results in reaching the target cumulative fuel sulfur 
exposure is determined from the field data using the aging cycle 
average fuel rate and the total number of accelerated aging hours.
    For a burner-based platform, accelerated fuel sulfur is introduced 
directly as gaseous SO2. Under the procedure, the 
SO2 must be introduced in a manner that does not impede any 
burner combustion, and only in a location that represents the exhaust 
conditions entering the aftertreatment system. Under the procedure, the 
mass rate of sulfur that must be introduced on a cycle average basis to 
reach the target cumulative fuel sulfur exposure from the field data is 
determined after the final aging cycle has been generated.
    The accelerated aging protocol is run on a bench aging platform 
that includes features necessary to successfully achieve accelerated 
aging of thermal and chemical aging factors. This aging bench can be 
built around either an engine or a burner as the core heat generating 
element. The requirements for both kinds of bench aging platform are 
described in the following paragraphs.
    The engine-based accelerated aging platform is built around the use 
of a diesel engine for generation of heat and flow. The engine used 
does not need to be the same engine as the application that is being 
aged. Any diesel engine can be used, and the engine may be

[[Page 4387]]

modified as needed to support meeting the aging procedure requirements. 
You may use the same bench aging engine for deterioration factor 
determination from multiple engine families. The engine must be capable 
of reaching the combination of temperature, flow, NOX, and 
oil consumption targets required. Using an engine platform larger than 
the target application for a given aftertreatment system can provide 
more flexibility to achieve the target conditions and oil consumption 
rates.
    To increase the range of flexibility of the bench aging engine 
platform, the test cell setup should include additional elements to 
allow more independent control of exhaust temperature and flow than 
would be available from the engine alone. For example, exhaust heat 
exchangers and/or the use of cooled and uncooled exhaust pipe can be 
useful to provide needed flexibility. When using heat exchangers under 
this procedure, you must ensure that you avoid condensation in any part 
of the exhaust system prior to the aftertreatment. You can also control 
engine parameters and the calibration on the engine to achieve 
additional flexibility needed to reach the target exhaust conditions.
    Under this procedure, oil consumption must be increased from normal 
levels to reach the target of 10 times oil consumption. As noted 
earlier, oil must be introduced through a combination of a bulk 
pathway, which represents the majority of oil consumption past the 
piston rings, and a volatile pathway, which is achieved by adding small 
amounts of lube oil to the fuel. The total oil exposure via the 
volatile pathway must be between 10 percent and 30 percent of the total 
accelerated oil consumption. Under this procedure, the remainder of the 
oil consumption must be introduced via the bulk pathway. The volatile 
portion of the oil consumption should be introduced and monitored 
continuously via a mass flow meter or controller.
    Under this procedure, the engine will need to be modified to 
increase oil consumption via the bulk pathway. This increase is 
generally achieved through a combination of engine modifications and 
the selection of aging speed/load combinations that will result in 
increased oil consumption rates. To achieve this, you may modify the 
engine in a fashion that will increase oil consumption in a manner such 
that the oil consumption is still generally representative of oil 
passing the piston rings into the cylinder. Inversion of the top 
compression rings as a method which has been used to increase oil 
consumption successfully for the DAAAC aging program at SwRI. A 
secondary method that has been used in combination with the primary 
method involves the modification of the oil control rings in one or 
more cylinders to create small notches or gaps (usually no more than 
two per cylinder) in the top portion of the oil control rings that 
contact the cylinder liner (care must be taken to avoid compromising 
the structural integrity of the ring itself).
    Under this procedure, oil consumption for the engine-based platform 
must be tracked at least periodically via a drain and weigh process, to 
ensure that the proper amount of oil consumption has been achieved. It 
is recommended that the test stand include a constant volume oil system 
with a sufficiently large oil reservoir to avoid oil ``top-offs'' 
between oil change intervals. Under this procedure, periodic oil 
changes will be necessary on any engine platform, and it is recommended 
that the engine be run for at least 72 hours following an oil change 
with engine exhaust not flowing through the aftertreatment system to 
stabilize oil consumption behavior before resuming aging. A secondary 
method for tracking oil consumption is to use clean DPF weights to 
track ash loading, and compare this mass of ash to the amount predicted 
using the measured oil consumption mass and the oil ash concentration. 
The mass of ash found by DPF weight should fall within a range of 55 
percent to 70 percent of the of mass predicted from oil consumption 
measurements.
    The engine should also include a means of introducing supplemental 
fuel to the exhaust to support regeneration if regeneration events are 
part of the aging. This can be done either via post-injection from the 
engine or using in-exhaust injection. The method and location of 
supplemental fuel introduction should be representative of the approach 
used on the target application, but manufacturers may adjust this 
methodology as needed on the engine-based aging platform to achieve the 
target regeneration temperature conditions.
    The burner-based aging platform is built around a fuel-fired burner 
as the primary heat generation mechanism. For the accelerated aging 
application under this procedure, the burner must utilize diesel fuel 
and it must produce a lean exhaust gas mixture. Under this procedure, 
the burner must have the ability to control temperature, exhaust flow 
rate, NOX, oxygen, and water to produce a representative 
exhaust mixture that meets the accelerated aging cycle targets for the 
aftertreatment system to be aged. Under this procedure, the burner must 
include a means to monitor these constituents in real time, except in 
the case of water where the system's water metering may be verified via 
measurements made prior to the start of aging (such as with an FTIR) 
and should be checked periodically by the same method. Under this 
procedure, the accelerated aging cycle for burner-based aging must also 
include representative mode targets for oxygen and water, because these 
will not necessarily be met by the burner itself through combustion. As 
a result, for this procedure the burner will need features to allow the 
addition of water and the displacement of oxygen to reach 
representative target levels of both. During non-regeneration modes, it 
is recommended that the burner be operated in a manner to generate a 
small amount of soot to facilitate proper ash distribution in the DPF 
system.
    The burner-based platform requires methods for oil introduction for 
both the bulk pathway and the volatile pathway. For the bulk pathway, 
manufacturers may implement a method that introduces lubricating oil in 
a region of the burner that does not result in complete combustion of 
the oil, but at the same time is hot enough to oxidize oil and oil 
additives in a manner similar to what occurs when oil enters the 
cylinder of an engine past the piston rings. Care must be taken to 
ensure the oil is properly atomized and mixed into the post-combustion 
burner gases before they have cooled to normal exhaust temperatures, to 
insure proper digestion and oxidation of the oil constituents. The 
volatile pathway oil is mixed into the burner fuel supply and combusted 
in the burner. As noted earlier, under this procedure total oil 
exposure via the volatile pathway must be between 10 percent and 30 
percent of the total accelerated oil consumption. The consumption of 
oil in both pathways should be monitored continuously via mass flow 
meters or controllers. A secondary method of tracking oil consumption 
is to use clean DPF weights to track ash loading and compare this mass 
of ash to the amount predicted using the measured oil consumption mass 
and the oil ash concentration. The mass of ash found by DPF weight 
should fall within a range of 55 percent to 70 percent of the of mass 
predicted from oil consumption measurements. This will also ensure that 
injected oil mass is actually done in a representative manner so that 
it reaches the aftertreatment system.
    Under this procedure, the burner-based platform will also need a 
method to introduce and mix gaseous SO2 to achieve the 
accelerated sulfur targets. Under this procedure, the consumption

[[Page 4388]]

of SO2 must be monitored continuously via a mass flow meter 
or controller. SO2 does not need to be injected during 
regeneration modes.
    The burner-based platform should also include a means of 
introducing supplemental fuel to the exhaust to support regeneration if 
regeneration events are part of the aging. We recommend that the method 
and location of supplemental fuel introduction be representative of the 
approach used on the target application, but manufacturers may adjust 
this methodology as needed on the bench engine platform to achieve the 
target regeneration temperature conditions. For example, to simulate 
post-injected fuel we recommend to introduce the supplemental fuel into 
the post-combustion burner gases to achieve partial oxidation that will 
produce more light and partially oxidized hydrocarbons similar to post-
injection.
    There are specific requirements for the implementation, running, 
and validation of an accelerated aging cycle developed using the 
processes described in this section. Some of these requirements are 
common to both engine-based and burner-based platforms, but others are 
specific to one platform type or the other.
    We recommended carrying out one or more practice aging cycles to 
help tune the cycle and aging platform to meet the cycle requirements. 
These runs can be considered part of the de-greening of test parts, or 
these can be conducted on a separate aftertreatment.
    The final target cycle is used to calculate a cumulative target 
deactivation for key aftertreatment components. Manufacturers must also 
generate a cumulative deactivation target line describing the linear 
relationship between aging hours and cumulative deactivation. The 
temperature of all key components is monitored during the actual aging 
test and the actual cumulative deactivation based on actual recorded 
temperatures is calculated. The cumulative deactivation must be 
maintained to within 3 percent of the target line over the course of 
the aging run and if you are exceeding these limits, you must adjust 
the aging stand parameters to ensure that you remain within these 
limits. Under this procedure, you must stay within these limits for all 
primary key components. It should be noted that any adjustments made 
may require adjustment of the heat rejection through the system if you 
are seeing different behavior than the target cycle suggests based on 
the field data. If you are unable to meet this requirement for any 
tracked secondary system (for example for a DOC where the SCR is the 
primary component), you may instead track the aging metric directly and 
show that you are within 3 percent of the target aging metric. Note 
that this is more likely to occur when there is a large difference 
between the thermal reactivity coefficients of different components.
    Calculate a target line for oil accumulation and sulfur 
accumulation showing a linear relationship between aging hours and the 
cumulative oil exposure on a mass basis. Under this procedure, you must 
stay within 10 percent of this target line for oil 
accumulation, and within 5 percent of this target line for 
sulfur accumulation. In the case of engine-based bulk oil accumulation 
you will only be able to track this based on periodic drain and weigh 
measurements. For all other chemical aging components, track exposure 
based on the continuous data from the mass flow meters for these 
chemical components. If your system includes a DPF, it is recommend 
that you implement the secondary tracking of oil consumption using DPF 
ash loading measurements as describe earlier.
    For the engine-based platform, it will be necessary under this 
procedure to develop a schedule of engine operating modes that achieve 
the combined temperature, flow, and oil consumption targets. You may 
deviate from target NOX levels as needed to achieve these 
other targets, but we recommend that you maintain a NOX 
level representative of the target application or higher on a cycle 
average basis. Note that the need to operate at modes that can reach 
the target oil consumption will leverage the flexibility of the engine 
stand, and you may need to iterate on the accelerated oil consumption 
modifications to achieve a final target configuration. You may need to 
adjust the cycle or modify the oil consumption acceleration to stay 
within the 10 percent target. In the even that you find 
that actual fuel consumption varies from original assumptions, you may 
need to adjust the doped fuel sulfur level periodically to maintain the 
sulfur exposure within the 5 percent limit.
    If the application uses DEF, it must be introduced to the exhaust 
stream in a manner that represents the target application. You may use 
hardware that is not identical to the production hardware but ensure 
that hardware produces representative performance. Similarly, you may 
use hardware that is not identical to production hardware for fuel 
introduction into the exhaust as long you ensure that the performance 
is representative.
    Under this procedure, for the burner-based platform, you will be 
able to directly implement the temperature, flow, NOX, 
sulfur, and oil consumption targets. You will also need to implement 
water and O2 targets to reach levels representative of 
diesel exhaust. We recommend that you monitor and adjust oil and sulfur 
dosing on a continuous basis to stay within targets. You must verify 
the performance of the oil exposure system via the secondary tracking 
of oil exposure via DPF ash loading and weighing measurements. This 
will ensure that your oil introduction system is functioning correctly. 
If you use a reductant, such as DEF, for NOX reduction, use 
good engineering judgement to introduce DEF in a manner that represents 
the target application. You may use hardware that is not identical to 
the production hardware but ensure that the hardware produces 
representative performance. Similarly, you may use hardware that is not 
identical to production hardware for fuel introduction into the exhaust 
as long you ensure that the performance is representative.
    The implementation and carrying out of these procedures will enable 
acceleration of the deterioration factor determination testing, and 
generally allow the determination of the deterioration factor out to 
useful life, over 90 days of testing.

G. Averaging, Banking, and Trading

    EPA is finalizing an averaging, banking, and trading (ABT) program 
for heavy-duty engines that provides manufacturers with flexibility in 
their product planning while encouraging the early introduction of 
emissions control technologies and maintaining the expected emissions 
reductions from the program. Several core aspects of the ABT program we 
are finalizing are consistent with the proposed ABT program, but the 
final ABT program includes several updates after consideration of 
public comments. In particular, EPA requested comment on and agrees 
with commenters that a lower family emission limit (FEL) cap than 
proposed is appropriate for the final rule. Further, after 
consideration of public comments, EPA is not finalizing at this time 
the proposed Early Adoption Incentives program, and in turn we are not 
including emissions credit multipliers in the final program. Rather, we 
are finalizing an updated version of the proposed transitional credit 
program under the ABT program. As described in preamble Section IV.G.7, 
the revised transitional credit program that we are finalizing provides 
four pathways to generate straight NOX

[[Page 4389]]

emissions credits (i.e., no credit multipliers) that are valued based 
on the extent to which the engines generating credits comply with the 
requirements we are finalizing for MY 2027 and later (e.g., credits 
discounted at a rate of 40 percent for engines meeting a lower numeric 
standard but none of the other MY 2027 and later requirements) (see 
section 12 of the Response to Comments document and preamble Section 
IV.G.7 for more details). In addition, we are finalizing a production 
volume allowance for MYs 2027 through 2029 that is consistent with the 
proposal but different in several key aspects, including that 
manufacturers will be required to use NOX emissions credits 
to certify heavy heavy-duty engines compliant with MY 2010 requirements 
in MYs 2027 through 2029 (see Section IV.G.9 for details). Finally, we 
are not finalizing the proposed allowance for manufacturers to generate 
NOX emissions credits from heavy-duty zero emissions 
vehicles (ZEVs) (see Section IV.G.10).
    Consistent with the proposed ABT program, the final ABT program 
will maintain several aspects of the ABT program currently specified in 
40 CFR 86.007-15, including:
     Allowing ABT of NOX credits with no expiration 
of the ABT program,
     calculating NOX credits based on a single 
NOX FEL for an engine family,
     specifying FELs to the same number of decimal places as 
the applicable standards, and
     calculating credits based on the work and miles of the FTP 
cycle.
    In this Section we briefly describe the proposed ABT program, the 
comments received on the proposed ABT program, and EPA's response to 
those comments. Subsequent subsections provide additional details on 
the restrictions we are finalizing for using emission credits in model 
years 2027 and later, such as averaging sets (Section IV.G.2), FEL caps 
(Section IV.G.4), and limited credit life (Section IV.G.4). See the 
proposed rule preamble (87 FR 17550, March 28, 2022) for additional 
discussion on the proposed ABT program and the history of ABT for 
heavy-duty engines.
    The proposed ABT program allowed averaging, banking, and trading of 
NOX credits generated against applicable heavy-duty engine 
NOX standards, while discontinuing a credit program for HC 
and PM. We also proposed new provisions to clarify how FELs apply for 
additional duty cycles. The proposed program included restrictions to 
limit the production of new engines with higher emissions than the 
standards; these restrictions included FEL caps, credit life for 
credits generated for use in MYs 2027 and later, and the expiration of 
currently banked credits. These provisions were included in proposed 40 
CFR part 1036, subpart H. and 40 CFR 1036.104(c). In addition, we 
proposed interim provisions in 40 CFR 1036.150(a)(1) describing how 
manufacturers could generate credits in MY 2024 through 2026 to apply 
in MYs 2027 and later. We requested comment on several aspects of the 
proposed ABT program that we are updating in the final rule, including 
the transitional credit program and level of the FEL cap, which 
restrict the use of credits in MY 2027 and later.
    Many commenters provided perspectives on the proposed ABT program. 
The majority of commenters supported the proposed ABT program, although 
several suggested adjustments for EPA to consider in the final rule. In 
contrast, a number of commenters opposed the proposed ABT program and 
argued that EPA should eliminate the NOX ABT program in the 
final rule. Perspectives from commenters supporting and opposing the 
proposed ABT program are briefly summarized in this section with 
additional details in section 12 of the Response to Comments document.
    Commenters supporting the ABT program stated that it provides an 
important flexibility to manufacturers for product planning during a 
transition to more stringent standards. They further stated that a 
NOX ABT program would allow manufacturers to continue 
offering a complete portfolio of products, while still providing real 
NOX emissions reductions. In contrast, commenters opposing 
the ABT program argued EPA should eliminate the NOX ABT 
program in order to maximize NOX emissions reductions 
nationwide, particularly in environmental justice communities and other 
areas impacted by freight industry. These commenters stated that the 
NOX standards are feasible without the use of credits, and 
that eliminating the credit flexibilities of an ABT program would be 
most consistent with EPA's legal obligations under the CAA.
    EPA agrees with those commenters who support a well-designed ABT 
program as a way to help us meet our emission reduction goals at a 
faster pace while providing flexibilities to manufacturers to meet new, 
more stringent emission standards. For example, averaging, banking, and 
trading can result in emissions reductions by encouraging the 
development and use of new and improved emission control technology, 
which results in lower emissions. The introduction of new emission 
control technologies can occur either in model years prior to the 
introduction of new standards, or during periods when there is no 
change in emissions standards but manufacturers still find it useful to 
generate credits for their overall product planning. In either case, 
allowing banking and trading can result in emissions reductions earlier 
in time, which leads to greater public health benefits sooner than 
would otherwise occur; benefits realized sooner in time are generally 
worth more to society than those deferred to a later time.\391\ These 
public health benefits are further ensured through the use of 
restrictions on how and when credits may be used (e.g., averaging sets, 
credit life), which are discussed further in this Section IV.G. For 
manufacturers, averaging, banking, and trading provides additional 
flexibility in their product planning by providing additional lead time 
before all of their engine families must comply with all the new 
requirements without the use of credits. For periods when no changes in 
emission standards are involved, banking can provide manufacturers 
additional flexibility, provide assurance against any unforeseen 
emissions-related problems that may arise, and in general provide a 
means to encourage the development and introduction of new engine 
technology (see 55 FR 30585, July 26, 1990, for additional discussion 
on potential benefits of an ABT program).
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    \391\ Consistent with economic theory, we assume that people 
generally prefer present to future consumption. We refer to this as 
the time value of money, which means money received in the future is 
not worth as much as an equal amount received today. This time 
preference also applies to emissions reductions that result in the 
health benefits that accrue from regulation. People have been 
observed to prefer health gains that occur immediately to identical 
health gains that occur in the future. Health benefits realized in 
the near term are therefore worth more to society than those 
deferred to a later time.
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    While EPA also agrees with those commenters stating that the 
standards in the final rule are feasible without the use of credits, as 
described in Section III of this preamble, given the technology-forcing 
nature of the final standards we disagree that providing an optional 
compliance pathway through the final rule's ABT program is inconsistent 
with requirements under CAA section 202(a)(3)(A).\392\ The final ABT 
program appropriately balances flexibilities for manufacturers to 
generate NOX

[[Page 4390]]

emissions credits with updated final restrictions (e.g., credit life, 
averaging sets, and family emissions limit (FEL) caps) that in our 
judgement both ensure that available emissions control technologies are 
adopted and maintain the emissions reductions expected from the final 
standards.\393\ An ABT program is also an important foundation for 
targeted incentives to encourage manufacturers to adopt advanced 
technology before required compliance dates, which we discuss further 
in preamble Section IV.G.7 and Section 12 of the Response to Comments 
document.
---------------------------------------------------------------------------

    \392\ See NRDC v. Thomas, 805 F. 2d 410, 425 (D.C. Cir. 1986), 
which upheld emissions averaging after concluding that ``EPA's 
argument that averaging will allow manufacturers more flexibility in 
cost allocation while ensuring that a manufacturer's overall fleet 
still meets the emissions reduction standards makes sense''.
    \393\ As discussed in Section IV.G.9, we are finalizing an 
allowance for manufacturers to continue to produce a small number (5 
percent of production volume) of engines that meet the current 
standards for a few model years (i.e., through MY 2030). See Section 
IV.G.9 for details on our approach and rationale for including this 
allowance in the final rule.
---------------------------------------------------------------------------

    One commenter opposing EPA's proposed NOX emissions ABT 
program provided analyses for EPA to consider in developing the final 
rule. EPA has evaluated the three approaches to generating credits in 
the commenter's analysis: (1) Engines certified below today's standards 
which qualify for the proposed transitional credit program, (2) engines 
certified to the CARB Omnibus standards which would quality for the 
proposed transitional program or on average achieve a standard below 
Federal requirements, and (3) ZEVs. For the first category (the 
transitional credit program), we considered several factors when 
designing the final transitional credit program that are more fully 
described in preamble Section IV.G.7; briefly, the transitional credit 
program we are finalizing will discount the credits manufacturers 
generated from engines certified to levels below today's standards 
unless manufacturers can meet all of the requirements in the final MY 
2027 and later standards. This includes meeting standards such as the 
final low load cycle (LLC), which requires demonstration of emissions 
control in additional engine operations (i.e., low load) compared to 
today's test cycles. For the second category in the commenter's 
analysis (engines certified to Omnibus standards), we recognize that 
our proposed rule preamble may have been unclear regarding how the 
existing regulations in part 86 and part 1036 apply for purposes of 
participation in the Federal ABT program to engines that are certified 
to state standards that are different than the Federal standards. We 
proposed to migrate without substantive modification the definition of 
``U.S.-directed production'' in 40 CFR 86.004-2 to 40 CFR part 1036.801 
for criteria pollutant engine requirements, to match the existing 
definition for GHG engine requirements, which excludes engines 
certified to state emission standards that are different than the 
Federal standards.\394\ The relevant existing NOX ABT credit 
program requirements, and the relevant program requirements we are 
finalizing as proposed, specify that compliance through ABT does not 
allow credit calculations to include engines excluded from the 
definition of U.S.-directed production volume.\395\ For the third 
category in the commenter's analysis (ZEVs), as discussed in preamble 
Section IV.G.10 and section 12 of the Response to Comments document, we 
are not finalizing the proposed allowance for manufacturers to generate 
NOX credits from ZEVs. For these reasons, EPA believes the 
final ABT program will at a minimum maintain the emissions reductions 
projected from the final rule, and in fact could result in greater 
public health benefits by resulting in emissions reductions earlier in 
time than they would occur without banking or trading. Further, if 
manufacturers generate NOX emissions credits that they do 
not subsequently use (e.g., due to transitioning product lines to 
ZEVs), then the early emissions reductions from generating these 
credits will result in more emission reductions than our current 
estimates reflect. In addition, the final ABT program provides an 
important flexibility for manufacturers, which we expect will help to 
ensure a smooth transition to the new standards and avoid delayed 
emissions reductions due to slower fleet turnover than may occur 
without the flexibility of the final ABT program.
---------------------------------------------------------------------------

    \394\ See Section XI.B.4 for additional information.
    \395\ See final part 1036, subpart H. Existing 40 CFR 
1036.705(c) states the following, which we are finalizing as 
proposed as also applicable to NOX ABT: ``As described in 
Sec.  1036.730, compliance with the requirements of this subpart is 
determined at the end of the model year based on actual U.S.-
directed production volumes. Keep appropriate records to document 
these production volumes. Do not include any of the following 
engines to calculate emission credits: . . . (4) Any other engines 
if we indicate elsewhere in this part 1036 that they are not to be 
included in the calculations of this subpart.'' See also existing 40 
CFR 86.007-15 (regarding U.S.-directed production engines for the 
purpose of using or generating credits during a phase-in of new 
standards) and 66 FR 5114, January 18, 2001.
---------------------------------------------------------------------------

    In the subsections that follow we briefly summarize and provide 
responses to comments on several more specific topics, including: ABT 
for pollutants other than NOX (IV.G.1), Applying the ABT 
provisions to multiple NOX duty-cycle standards (IV.G.2), 
Averaging Sets (IV.G.3), FEL caps (IV.G.4), Credit Life (IV.G.5), 
Existing credits (IV.G.6), Transitional Credits (IV.G.7), the proposed 
Early Adoption Incentives (IV.G.8), and a Production Volume Allowance 
under ABT (IV.G.9). The final ABT program is specified in 40 CFR part 
1036, subpart H.\396\ Consistent with the proposal, we are also 
finalizing a new paragraph at 40 CFR 1036.104(c) to specify how the ABT 
provisions will apply for MY 2027 and later heavy-duty engines subject 
to the final criteria pollutant standards in 40 CFR 1036.104(a). The 
Transitional Credit program in the final rule is described in the 
interim provision in 40 CFR 1036.150(a)(1), which we are finalizing 
with revisions from the proposal.
---------------------------------------------------------------------------

    \396\ As proposed, the final rule does not include substantive 
revisions to the existing GHG provisions in 40 CFR 1036, subpart H; 
as proposed, the final revisions clarify whether paragraphs apply 
for criteria pollutant standards or GHG standards.
---------------------------------------------------------------------------

1. ABT for Pollutants Other Than NOX
    After consideration of public comments, EPA is choosing to finalize 
as proposed an ABT program that will not allow averaging, banking, or 
trading for HC (including NOX+NMHC) or PM for MY 2027 and 
later engines. This includes not allowing HC and PM emissions credits 
from prior model years to be used for MY 2027 and later engines. For 
engines certified to MY 2027 or later standards, manufacturers must 
demonstrate in their application for certification that they meet the 
final PM, HC, and CO emission standards in 40 CFR 1036.104(a) without 
using emission credits.
    Several commenters supported EPA's proposal to discontinue ABT for 
HC and PM. These commenters stated that current heavy-duty engine 
technologies can easily meet the proposed HC and PM standards, and 
therefore an ABT program for these pollutants is not necessary. Some 
commenters urged EPA to provide ABT programs for HC and CO based on the 
stringency of the standards for these pollutants, particularly for 
Spark-ignition HDE. Another commenter did not indicate support or 
opposition to an HC ABT flexibility in general, but stated that EPA 
should not base the final HC standard on the use of HC emissions 
credits since doing so could lead to competitive disruptions between SI 
engine manufacturers. One commenter also urged EPA to consider ABT 
programs for regulated pollutant emissions other than NOX, 
including HC, PM, CO, and N2O.
    As discussed in preamble Section III, EPA demonstrated that the 
final standards for NOX, HC, CO, and PM area feasible for 
all engine classes, and we

[[Page 4391]]

set the numeric values without assuming manufacturers would require the 
use of credits to comply. We proposed to retain and revise the 
NOX ABT program and we are updating from our proposal in 
this final rule as described in the following sections.
    For PM, manufacturers are submitting certification data to the 
agency for current production engines well below the final PM standard 
over the FTP duty cycle; the final standard ensures that future engines 
will maintain the low level of PM emissions of the current engines. 
Manufacturers are not using PM credits to certify today and we received 
no new data showing manufacturers would generate or use PM credits 
starting in MY 2027; therefore, we are finalizing as proposed.
    We disagree with commenters indicating that credits will be needed 
for Spark-ignition HDE to meet the final HC and CO standards. Our SI 
engine demonstration program data show feasibility of the final 
standards (see preamble Section III.D for details). Furthermore, as 
described in Section IV.G.3, we are retaining the current ABT 
provisions that restrict credit use to within averaging sets and we 
expect SI engine manufacturers, who have few heavy-duty engine 
families, will have limited ability to generate and use credits. See 
preamble Section III.D for a discussion of the final numeric levels of 
the Spark-ignition HDE standards and adjustments we made to the 
proposed HC and CO stringencies after further consideration.
    We did not propose or request comment on expanding the heavy-duty 
engine ABT program to include other regulated pollutant emissions, such 
as N2O, and thus are not including additional pollutants in 
the final ABT program.
2. Multiple Standards and Duty Cycles for NOX ABT
    Under the current and final ABT provisions, FELs serve as the 
emission standards for the engine family for compliance testing 
purposes.\397\ We are finalizing as proposed new provisions to ensure 
the NOX emission performance over the FTP is proportionally 
reflected in the range of cycles included in the final rule for heavy-
duty engines.\398\ Specifically, manufacturers will declare a FEL to 
apply for the FTP standards and then they will calculate a 
NOX FEL for the other applicable cycles by applying an 
adjustment factor based on their declared FELFTP. As 
proposed, the adjustment factor in the final rule is a ratio of the 
declared NOX FELFTP to the FTP NOX 
standard to scale the NOX FEL of the other duty cycle or 
off-cycle standards.\399\ For example, if a manufacturer declares an 
FELFTP of 25 mg NOX/hp-hr in MY 2027 for a Medium 
HDE, where the final NOX standard is 35 mg/hp-hr, a ratio of 
25/35 or 0.71 will be applied to calculate a FEL to replace each 
NOX standard that applies for these engines in the proposed 
40 CFR 1036.104(a). Specifically, for this example, a Medium HDE 
manufacturer would replace the full useful life standards for SET, LLC, 
and the three off-cycle bins with values that are 0.71 of the final 
standards. For an SI engine manufacturer that declares an 
FELFTP of 15 mg NOX/hp-hr compared to the final 
MY 2027 standard of 35 mg/hp-hr, a ratio of 15/35 or 0.43 would be 
applied to the SET duty cycle standard to calculate an 
FELSET. Note that an FELFTP can also be higher 
than the NOX standard in an ABT program if it is offset by 
lower-emitting engines in an engine family that generates equivalent or 
more credits in the averaging set (see 40 CFR 1036.710). For a FEL 
higher than the NOX standard, the adjustment factor will 
proportionally increase the emission levels allowed when manufacturers 
demonstrate compliance over the other applicable cycles. Manufacturers 
are required to set the FEL for credit generation such that the engine 
family's measured emissions are at or below the respective FEL of all 
the duty-cycle and off-cycle standards. For instance, if a CI engine 
manufacturer demonstrates NOX emissions on the FTP that is 
25 percent lower than the standard but can only achieve 10 percent 
lower NOX emissions for the low load cycle, the declared FEL 
could be no less than 10 percent below the FTP standard, to ensure the 
proportional FELLLC would be met.
---------------------------------------------------------------------------

    \397\ The FELs serves as the emission standard for compliance 
testing instead of the standards specified in 40 CFR 1036.104(a); 
the manufacturer agrees to meet the FELs declared whenever the 
engine is tested over the applicable duty- or off-cycle test 
procedures.
    \398\ See the proposed rule preamble (87 FR 17550, March 28, 
2022) for discussion on the relationship between the current FTP 
standards and other duty- or off-cycle standards.
    \399\ As proposed, we will require manufacturers to declare the 
NOX FEL for the FTP duty cycle in their application for 
certification. Manufacturers and EPA will calculate FELs for the 
other applicable cycles using the procedures specified in 40 CFR 
1036.104(c)(3) to evaluate compliance with the other cycles; 
manufacturers will not be required to report the calculated FELs for 
the other applicable cycles. As noted previously, manufacturers will 
demonstrate they meet the standards for PM, CO, and HC and will not 
calculate or report FELs for those pollutants.
---------------------------------------------------------------------------

    In the final program, manufacturers will include test results in 
the certification application to demonstrate their engines meet the 
declared FEL values for all applicable duty cycles (see 40 CFR 
1036.240(a), finalized as proposed). For off-cycle standards, we are 
also finalizing as proposed the requirement for manufacturers to 
demonstrate that all the CI engines in the engine family comply with 
the final off-cycle emission standards (or the corresponding FELs for 
the off-cycle bins) for all normal operation and use by describing in 
sufficient detail any relevant testing, engineering analysis, or other 
information (see 40 CFR 1036.205(p)). These same bin standards (or 
FELs) apply for the in-use testing provisions finalized in 40 CFR part 
1036, subpart E, and for the PEM-based DF verification in the finalized 
40 CFR 1036.246(b)(2), if applicable.\400\ In addition, as discussed in 
Section III, we are finalizing a compliance margin for Heavy HDE to 
account for additional variability that can occur in-use over the 
useful life of HHDEs; the same 15 mg/hp-hr in-use compliance margin for 
HHDEs will be added to declared FELs when verifying in-use compliance 
for each of the duty-cycles (i.e., compliance with duty-cycle standards 
once the engine has entered commerce) (see 40 CFR 1036.104(a)). 
Similarly, the same in-use compliance margin will be applied when 
verifying in-use compliance over off-cycle standards (see preamble 
Section III.C for discussion).
---------------------------------------------------------------------------

    \400\ We did not propose and are not finalizing off-cycle 
standards for SI engines; if EPA requests SI engine manufacturers to 
perform PEMS-based DF verification as set forth in the final 40 CFR 
1036.246(b)(2), then the SI engine manufacturer would use their FEL 
to calculate the effective in-use standard for those procedures.
---------------------------------------------------------------------------

    Once FEL values are established, credits are calculated based on 
the FTP duty cycle. We did not propose substantive revisions to the 
equation that applies for calculating emission credits in 40 CFR 
1036.705, but we are finalizing, as proposed, to update the variable 
names and descriptions to apply for both GHG and criteria pollutant 
calculations.\401\ In Equation IV-1, we reproduce the equation of 40 
CFR 1036.705 to emphasize how the FTP duty cycle applies for 
NOX credits. Credits are calculated as megagrams (i.e., 
metric tons) based on the emission rate over the FTP cycle. The 
emission credit calculation represents the emission impact that would 
occur if an engine operated over the FTP cycle for its full useful 
life. The difference between the FTP standard and the FEL is multiplied 
by a conversion factor that represents the average work performed

[[Page 4392]]

over the FTP duty cycle to get the per-engine emission rate over the 
cycle. This value is then multiplied by the production volume of 
engines in the engine family and the applicable useful life mileage. 
Credits are calculated at the end of the model year using actual U.S. 
production volumes for the engine family. The credit calculations are 
submitted to EPA as part of a manufacturer's ABT report (see 40 CFR 
1036.730).
---------------------------------------------------------------------------

    \401\ The emission credits equations in the final 40 CFR 
1036.705 and the current 40 CFR 86.007-15(c)(1)(i) are functionally 
the same.
[GRAPHIC] [TIFF OMITTED] TR24JA23.001

---------------------------------------------------------------------------
Where:

StdFTP = the FTP duty cycle NOX emission 
standard, in mg/hp-hr, that applies for engines not participating in 
the ABT program
FEL = the engine family's FEL for NOX, in mg/hp-hr.
WorkFTP = the total integrated horsepower-hour over the 
FTP duty cycle.
MilesFTP = the miles of the FTP duty cycle. For Spark-
ignition HDE, use 6.3 miles. For Light HDE, Medium HDE, and Heavy 
HDE, use 6.5 miles.
Volume = the number of engine eligible to participate in the ABT 
program within the given engine family during the model year, as 
described in 40 CFR 1036.705(c).
UL = the useful life for the standard that applies for a given 
engine family, in miles.

    We did not receive specific comments on the proposed approach to 
calculate a NOX FEL for the other applicable cycles by 
applying an adjustment factor based on the declared FELFTP. 
As such, we are finalizing the approach as proposed.
3. Averaging Sets
    After consideration of public comments, we are finalizing, as 
proposed, to allow averaging, banking, and trading only within 
specified ``averaging sets'' for heavy-duty engine emission standards. 
Specifically, the final rule will use engine averaging sets that 
correspond to the four primary intended service classes,\402\ namely:
---------------------------------------------------------------------------

    \402\ Primary intended service class is defined in 40 CFR 
1036.140, which is referenced in the current 40 CFR 86.004-2.

 Spark-ignition HDE
 Light HDE
 Medium HDE
 Heavy HDE

    Some commenters urged EPA to allow manufacturers to move credits 
between the current averaging sets (e.g., credits generated by medium 
heavy-duty engines could be used by heavy heavy-duty engines), while 
other commenters recommended that EPA finalize the proposal to maintain 
restrictions that do not allow movement of credits between the current 
averaging sets. Those supporting movement of credits between averaging 
sets stated that doing so would reduce the likelihood that a 
manufacturer would develop two engines to address regulatory 
requirements when they could invest in only one engine if they were 
able to move credits between averaging sets; commenters also stated 
that restrictions on ABT decrease a manufacturer's ability to respond 
to changes in emissions standards. Those supporting the current 
restrictions that do not allow movement of credits between averaging 
sets stated that maintaining the averaging sets was important to avoid 
competitive disruptions between manufacturers.
    EPA agrees that maintaining the current averaging sets is important 
to avoid competitive disruptions between manufacturers; this is 
consistent with our current and historical approach to avoid creating 
unfair competitive advantages or environmental risks due to credit 
inconsistency.\403\ As described throughout this Section IV.G, we 
believe that the final ABT program, including this limitation, 
appropriately balances providing manufacturers with flexibility in 
their product planning, while maintaining the expected emissions 
reductions from the program. As we describe further in Section IV.G.7, 
we provide one exception to this limitation for one of the Transitional 
Credit pathways for reasons special to that program.\404\
---------------------------------------------------------------------------

    \403\ 55 FR 30585, July 26, 1990, 66 FR 5002 January 18, 2001 
and 81 FR 73478 October 25, 2016.
    \404\ As discussed in Section IV.G.7, one of the transitional 
credit pathways we are finalizing allows limited movement of 
discounted credits between a subset of averaging sets. The 
combination of discounting credits moved between averaging sets 
combined with the additional limitations included in this 
transitional pathway are intended to address the potential for 
competitive disadvantages or environmental risks from allowing 
credit movement between averaging sets.
---------------------------------------------------------------------------

4. FEL Caps
    As proposed, the final ABT program includes Family Emissions Limit 
(FEL) caps; however, after further consideration, including 
consideration of public comments, we are choosing to finalize lower FEL 
caps than proposed. The FEL caps in the final rule are 65 mg/hp-hr for 
MY 2027 through 2030, and 50 mg/hp-hr for MY 2031 and later (see 40 CFR 
1036.104(c)(2)). In this section, IV.G.4, we briefly summarize our 
proposed FEL caps, stakeholder comments on the proposed FEL caps, and 
then discuss EPA's responses to comments along with our rationale for 
the FEL caps in the final rule.
    We proposed maximum NOX FELFTP values of 150 
mg/hp-hr under both proposed Option 1 (for model year 2027 through 
2030), and proposed Option 2 (for model year 2027 and later). This 
value is consistent with the average NOX emission levels 
achieved by recently certified CI engines (see Chapter 3.1.2 of the 
RIA). We believed a cap based on the average NOX emission 
levels of recent engines would be more appropriate than a cap at the 
current standard of 0.2 g/hp-hr (200 mg/hp-hr), particularly when 
considering the potential for manufacturers to apply NOX 
credits generated from electric vehicles for the first time.\405\ For 
MY 2031 and later under Option 1, we proposed a consistent 30 mg/hp-hr 
allowance for each primary intended service class added to each full 
useful life standard.
---------------------------------------------------------------------------

    \405\ Note that the current g/hp-hr emission standards are 
rounded to two decimal places, which allow emission levels to be 
rounded down by as much as 5 mg/hp-hr (i.e., with rounding the 
current standard is 205 mg/hp-hr).
---------------------------------------------------------------------------

    We requested comment on our proposed FEL caps, including our 
approach to base the cap for MY 2027 through 2030 under Option 1, or MY 
2027 and later under Option 2, on the recent average NOX 
emission levels. We also requested comment on whether the 
NOX FELFTP cap in MY 2027 should be set at a 
different value, ranging from the current Federal NOX 
standard of approximately 200 mg/hp-hr to the 50 mg/hp-hr standard in 
CARB's HD Omnibus rule starting in MY 2024.406 407

[[Page 4393]]

We further requested comment on the proposal to set MY 2031 
NOX FEL caps at 30 mg/hp-hr above the full useful life 
standards under proposed Option 1. Finally, we requested comment on 
whether different FEL caps should be considered if we finalize 
standards other than those proposed (i.e., within the range between the 
standards of proposed Options 1 and 2) (See 87 FR 17550, March 28, 
2022, for additional discussion on our proposed FEL caps and historical 
perspective on FEL caps).
---------------------------------------------------------------------------

    \406\ California Air Resources Board, ``California Exhaust 
Emission Standards and Test Procedures for 2004 and Subsequent Model 
Heavy-Duty Diesel Engines and Vehicles,'' August 27, 2020. https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2020/hdomnibuslownox/frob-1.pdf, page 19. Last accessed September 8, 
2022.
    \407\ EPA is reviewing a waiver request under CAA section 209(b) 
from California for the Omnibus rule.
---------------------------------------------------------------------------

    Several commenters provided perspectives on the proposed FEL caps. 
All commenters urged EPA to finalize a lower FEL cap than proposed; 
there was broad agreement that the FEL cap in the final rule should be 
100 mg/hp-hr or lower.
    One commenter stated that a FEL cap at the level of the current 
standard would not meet the CAA 202(a)(3)(A) requirement to set 
``standards which reflect the greatest degree of emission reduction 
achievable through the application of technology which the 
Administrator determines will be available for the model year to which 
such standards apply''. Similarly, many commenters stated that EPA 
should finalize FEL caps that match the CARB Omnibus FEL caps (i.e., 
100 mg-hp-hr in 2024-2026 for all engine classes; 50 mg/hp-hr in 2027 
and later for LHDEs and MHDE and 65 mg/hp-hr in 2027-2030 and 70 mg/hp-
hr in 2031 and later for HHDEs). These commenters argue that aligning 
the FEL caps in the EPA final rule with those in the CARB Omnibus would 
reflect the technologies available in 2027 and later, and better align 
with the CAA 202(a)(3)(A) requirement for standards that reflect the 
greatest degree of emission reduction achievable. Commenters provide 
several lines of support that the CARB Omnibus FEL caps should provide 
the technical maximum for the EPA FEL caps. Namely, commenters stated 
that manufacturers will have been producing products to meet CARB 
Omnibus standard of 50 mg/hp-hr starting in 2024. They further state 
that two diesel engine families have been certified with CA for MY2022 
at a FEL of 160 mg/hp-hr, which is only slightly higher than the FEL 
EPA proposed under option 1 for MY 2027 and would continue under the 
proposed FEL cap until MY2030. Finally, a commenter pointed to SwRI 
data showing that 50 mg/hp-hr can be achieved with what the commenter 
considers to be ``minor changes to engine configuration.''
    Commenters further argue that EPA should not base the FEL cap in 
the final rule on the average performance of recently certified engines 
since these engines were designed to comply with the current standards, 
which were set over 20 years ago, and do not utilize the emissions 
controls technologies that would be available in 2027. Commenters 
stated that EPA did not consider the extent to which the proposed FEL 
cap could adversely affect the emissions reductions expected from the 
rule. Commenters note that although EPA has previously set the FEL cap 
at the level of the previous standard, the current FEL cap was set 
lower than the previous standard due to the 90 percent reduction 
between the previous standard and the current standard. Commenters 
argue that EPA should similarly set the FEL cap below the current 
standard given the same magnitude in reduction between the current and 
proposed standards, and the greater level of certainty in the 
technologies available to meet the standards in this rule compared to 
previous rules.
    Other commenters stated that a FEL cap of 100 mg/hp-hr, or between 
50 and 100 mg/hp-hr, would help to prevent competitive disruptions. 
Additional details on comments received on the proposed FEL caps are 
available in section 12.2 of the Response to Comments document.
    Our analysis and rationale for finalizing FEL caps of 65 mg/hp-hr 
in MY 2027 through 2030, and 50 mg/hp-hr in MY 2031and later includes 
several factors. First, we agree with commenters that the difference 
between the current (0.2 g/hp-hr) standard and the standards we are 
finalizing for MY 2027 and later suggests that FEL caps lower than the 
current standard are appropriate to ensure that available emissions 
control technologies are adopted. This is consistent with our past 
practice when issuing rules for heavy-duty onroad engines or nonroad 
engines in which there was a substantial (i.e., greater than 50 
percent) difference between the numeric levels of the existing and new 
standards (69 FR 38997, June 29, 2004; 66 FR 5111, January 18, 2001). 
Specifically, by finalizing FEL caps below the current standards, we 
are ensuring that the vast majority of new engines introduced into 
commerce include updated emissions control technologies compared to the 
emissions control technologies manufacturers use to meet the current 
standards.\408\
---------------------------------------------------------------------------

    \408\ As discussed in Section IV.G.9, we are finalizing an 
allowance for manufacturers to continue to produce a small number (5 
percent of production volume) of engines that meet the current 
standards for a few model years (i.e., through MY 2029); thus, the 
vast majority of, but not all, new engines will need to include 
updated emissions control technologies compared to those used to 
meet today's standards until MY 2031, when all engines will need 
updated emissions control technologies to comply with the final 
standards. See Section IV.G.9 for details on our approach and 
rationale for including this allowance in the final rule.
---------------------------------------------------------------------------

    Second, finalizing FEL caps below the current standard is 
consistent with comments from manufacturers stating that a FEL cap of 
100 mg/hp-hr or between 50 and 100 mg/hp-hr would help to prevent 
competitive disruptions (i.e., require all manufactures to make 
improvements in their emissions control technologies).
    The specific numeric levels of the final FEL caps were also 
selected to balance several factors. These factors include providing 
sufficient assurance that low-emissions technologies will be introduced 
in a timely manner, which is consistent with our past practice (69 FR 
38997, June 29, 2004), and providing manufacturers with flexibility in 
their product planning or assurance against unforeseen emissions-
related problems that may arise. In the early years of the program 
(i.e., MY2027 through 2030), we are finalizing a FEL cap of 65 mg/hp-hr 
to place more emphasis on providing manufacturers flexibility and 
assurance against unforeseen emissions control issues in order to 
ensure a smooth transition to the new standards and avoid market 
disruptions. A smooth transition in the early years of the program will 
help ensure the public health benefits of the final program by avoiding 
delayed emissions reductions due to slower fleet turnover than may 
occur without the flexibility of the final ABT. Thus, the final FEL cap 
in MY 2027 through 2030 can help to ensure the expected emissions 
reductions by providing manufacturers with flexibility to meet the 
final standards through the use of credits up to the FEL cap. In the 
later years of the program (i.e., MY 2031 and later), we are finalizing 
a FEL cap of 50 mg/hp-hr to place more emphasis on ensuring continued 
improvements in the emissions control technologies installed on new 
engines.
    We disagree with certain commenters stating that a certain numeric 
level of the FEL cap does or does not align with the CAA requirement to 
set ``standards which reflect the greatest degree of emission reduction 
achievable through the application of technology which the 
Administrator determines will be available for the model year to which 
such standards apply''; rather, given the technology-forcing nature of 
the final standards, an optional compliance

[[Page 4394]]

pathway, including the FEL caps and other elements of the ABT program, 
through the final rule is consistent with requirements under CAA 
section 202(a)(3)(A).\409\ Nevertheless, as described in this Section 
IV.G.4, we are finalizing lower FEL caps than proposed as part of a 
carefully balanced final ABT program that provides flexibilities for 
manufacturers to generate NOX emissions credits while 
assuring that available emissions control technologies are adopted and 
the emissions reductions expected from the final program are realized.
---------------------------------------------------------------------------

    \409\ See NRDC v. Thomas, 805 F. 2d 410, 425 (D.C. Cir. 1986) 
(upholding averaging as a reasonable and permissible means of 
implementing a statutory provision requiring technology-forcing 
standards).
---------------------------------------------------------------------------

    Finally, we disagree with commenters stating a FEL cap can 
adversely affect the emissions reductions expected from the final rule. 
Inherent in the ABT program is the requirement for manufacturers 
producing engines above the emissions standard to also produce engines 
below the standard or to purchase credits from another manufacturer who 
has produced lower emitting engines. As such, while the FEL cap 
constrains the extent to which engines can emit above the level of the 
standard, it does not reduce the expected emissions reductions because 
higher emitting engines must be balanced by lower emitting engines. 
Without credit multipliers, an ABT program, and the associated FEL cap, 
may impact when emissions reductions occur due to manufacturers 
choosing to certify some engines to a more stringent standard and then 
later use credits generated from those engines, but it does not impact 
the absolute value of the emissions reductions. Rather, to the extent 
that credits are banked, there would be greater emissions reductions 
earlier in the program, which leads to greater public health benefits 
sooner than would otherwise occur; as discussed earlier in this Section 
IV.G, benefits realized in the near term are worth more to society than 
those deferred to a later time.
    The FEL caps for the final rule have been set at a level to ensure 
sizeable emission reductions from the existing 2010 standards, while 
providing manufacturers with flexibility to meet the final standards. 
When combined with the other restrictions in the final ABT program 
(e.g., credit life, averaging sets, expiration of existing credit 
balances), we believe the final FEL caps of 65 mg/hp-hr in MY 2027 
through 2030, and 50 mg/hp-hr in MY 2031 and later avoid potential 
adverse effects on the emissions reductions expected from the final 
program.
5. Credit Life for MY 2027 and Later Credits
    As proposed, we are finalizing a five-year credit life for 
NOX emissions credits generated and used in MY 2027 and 
later, which is consistent with the existing credit life for 
CO2. In this section, IV.G.5, we briefly summarize our 
proposed credit life, stakeholder comments on the proposed credit life, 
and then discuss EPA's responses to comments along with our rationale 
for credit life in the final rule. Section IV.G.7 discusses credit life 
of credits generated in MYs 2022 through 2026 for use in 2027.
    We proposed to update the existing credit life provisions in 40 CFR 
1036.740(d) to apply for both CO2 and NOX 
credits. The proposal updated the current unlimited credit life for 
NOX credits such that NOX emission credits 
generated for use in MY 2027 and later could be used for five model 
years after the year in which they are generated.\410\ For example, 
under the proposal credits generated in model year 2027 could be used 
to demonstrate compliance with emission standards through model year 
2032. We also requested comment on our proposed five-year credit life.
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    \410\ As discussed in Section IV.G.10, we are not finalizing the 
proposed allowance for manufacturers to generate credits from BEVs 
or FCEVs, and thus the credit life provisions in 40 CFR 1036.740(d) 
do not apply to BEVs or FCEVs.
---------------------------------------------------------------------------

    Several commenters provided perspectives on the proposal to revise 
the credit life of NOX emissions credits from unlimited to 
five years. Commenters took several different positions, including 
supporting the proposed five-year credit life, arguing that three 
years, not five, is the more appropriate credit life period, and 
arguing that credit life should be unlimited. Additional details and a 
summary of comments received on the proposed credit life are available 
in section 12 of the Response to Comments document.
    The commenter supporting the proposed five-year credit life, rather 
than an unlimited credit life, states that they conducted an analysis 
that showed manufacturers had accrued credits from 2007-2009 MYs, which 
could have been used to certify engines up to the FEL cap in the 
Omnibus 2024-2026 program and would have delayed emissions reductions 
in those years. They further state that unlimited credit life would 
allow manufacturers to produce higher emitting engines against more 
stringent standards for many years (e.g., in MY2030).
    The commenter arguing that three (not five) years is an appropriate 
credit life to average out year-to-year variability stated that three 
years aligns with the CAA requirement for three years of stability 
between changes in standards, and it represents the pace of improvement 
that manufacturers include in their product planning. The commenter 
argues that three years would be more protective under the CAA and is 
the duration that EPA previously used for NOX and PM 
emissions credits. Finally, the commenter states that EPA has not 
justified its choice of five years.
    Commenters who urged EPA to finalize an unlimited credit life for 
NOX emissions credits did not provide data or rationale to 
support their assertion.
    After further consideration, including consideration of public 
comments, EPA is finalizing as proposed a five-year credit life for 
credits generated and used in MY 2027 and later. The credit life in the 
final rule is based on consideration of several factors. First, 
consistent with our proposal, we continue to believe a limited credit 
life, rather than an unlimited credit life suggested by some 
commenters, is necessary to prevent large numbers of credits 
accumulating early in the program from interfering with the incentive 
to develop and transition to other more advanced emissions control 
technologies later in the program. Further, as discussed in Section 
IV.G.7, we believe the transitional credit program in the final rule 
addresses key aspects of manufacturers' requests for longer credit 
life. Second, as explained in the proposal, we believe a five-year 
credit life adequately covers a transition period for manufacturers in 
the early years of the program, while continuing to encourage 
technology development in later years.
    We disagree with one commenter who stated that a three-year credit 
life is more appropriate than a five-year credit life. Rather, we 
believe five years appropriately balances providing flexibility in 
manufacturers product planning with ensuring available emissions 
control technologies are adopted. Further, as discussed in Section 
IV.G.4, inherent in an ABT program is the requirement for manufacturers 
producing engines above the emissions standard to also produce engines 
below the standard or to purchase credits from another manufacturer who 
has produced lower emitting engines. As such, while the five-year 
credit life in the final rule constrains the time period over which 
manufacturers can use credits, it does not impact the overall emissions

[[Page 4395]]

reductions from the final rule. In addition, to the extent that credits 
are banked for five-years, the emissions reductions from those credits 
occur five-years earlier, and as discussed earlier in this Section 
IV.G, benefits realized in the near term are worth more to society than 
those deferred to a later time. Finally, a five-year credit life is 
consistent with our approach in the existing light-duty criteria and 
GHG programs, as well as our heavy-duty GHG program (see 40 CFR 
86.1861-17, 86.1865-12, and 1037.740(c)).
    As discussed in Section IV.G.7, we are finalizing a shorter credit 
life for credits generated in 2022 through 2026 with engines certified 
to a FEL below the current MY 2010 emissions standards, while complying 
with all other MY 2010 requirements, since these credits are generated 
from engines that do not meet the MY 2027 and later requirements. We 
are also finalizing longer credit life values for engines meeting all, 
or some of the key, MY 2027 and later requirements to further 
incentivize emissions reductions before the new standards begin (see 
IV.G.7 for details).
6. Existing Credit Balances
    After further consideration, including information received in 
public comments, the final rule will allow manufacturers to generate 
credits in MYs 2022 and later for use in MYs 2027 and later, as 
described further in the following Section IV.G.7. Consistent with the 
proposal, in the final program, manufacturers will not be allowed to 
use credits generated prior to model year 2022 when certifying to model 
year 2027 and later requirements.
    We proposed that while emission credits generated prior to MY 2027 
could continue to be used to meet the existing emission standards 
through MY 2026 under 40 CFR part 86, subpart A, those banked credits 
could not be used to meet the proposed MYs 2027 and later standards 
(except as specified in 1036.150(a)(3) for transitional and early 
credits in 1036.150(a)(1) and (2)). Our rationale included that the 
currently banked NOX emissions credits are not equivalent to 
credits that would be generated under the new program (e.g., credits 
were generated without demonstrating emissions control under all test 
conditions of the new program), and that EPA did not rely on the use of 
existing credit balances to demonstrate feasibility of the proposed 
standards.
    Some commenters urged EPA to allow the use of existing credits, or 
credits generated after the release of the CTI ANPR, to be used in MYs 
2027 and later. Commenters stated that EPA has not demonstrated the 
standards are feasible without the use of credits, and that the credits 
were from engines with improved emissions that provide real-world 
NOX benefits, even if they are not certified to all of the 
test conditions of the proposed program. They further stated that not 
allowing the use of existing credits in 2027 and later could discourage 
manufacturers from proactively improving emissions performance. In 
contrast, other commenters support the proposal to discontinue the use 
of old credits (e.g., those generated before 2010) since allowing the 
use of these credits would delay emissions reductions and prevent a 
timely transition to new standards.
    EPA did not rely on the use of existing or prior to MY 2027 credit 
balances to demonstrate feasibility of the proposed standards (see 
Section III) and continues to believe that credits from older model 
years should not be used to meet the final MY 2027 and later standards. 
Credits from older model years (i.e., MY 2009 or prior) were generated 
as manufacturers transitioned to the current standards, and thus would 
not require manufacturers to introduce new emissions control 
technologies to generate credits leading up to MY 2027. However, EPA 
agrees with some commenters that credits generated in model years 
leading up to MY 2027 are from engines with improved emissions controls 
and provide some real-world NOX benefits, even if they are 
not certified to all of the test conditions of the model year 2027 and 
later program. Therefore, the transitional credit program we are 
finalizing allows manufacturers to generate credits starting in model 
year 2022 for use in MYs 2027 and later; however, credits generated 
from engines in MYs 2022-2026 that do not meet all of the MY 2027 and 
later requirements are discounted to account for the differences in 
emissions controls between those engines and engines meeting all 2027 
and later requirements (see Section IV.G.7 and Section 12 of the RTC 
for details). For credits generated in model years prior to MY 2022, we 
are finalizing that such emission credits could continue to be used to 
meet the existing emission standards through MY 2026 under 40 CFR part 
86, subpart A.
    We selected model year 2022 for two reasons. First, allowing MY 
2022 and later credits inherently precludes emissions credits from the 
oldest model years (i.e., MY 2009 or prior). These oldest years are 
when the vast majority of existing credit balances were accumulated, to 
create flexibility in transitioning to the MY 2007-2010 standards.\411\ 
The oldest model year credits were not generated with current emissions 
control technologies and are therefore quite distinct from credits 
generated under the final standards. Second, regarding both the oldest 
MY credits and those few generated in more recent years, allowing only 
MY 2022 and later credits incentivizes manufacturers to maximize their 
development and introduction of the best available emissions control 
technologies ahead of when they are required to do so in MY2027. As 
discussed in IV.G.7, this not only provides a stepping-stone to the 
broader introduction of this technology soon thereafter, but also 
encourages the early production of cleaner vehicles, which enhances the 
early benefits of our program. If we were to allow manufacturers to use 
emissions credits from older model years then there would be no 
incentive to apply new emissions control technologies in the years 
leading up to MY 2027. Further, we recognize that some manufacturers 
have begun to modernize some of their emissions controls in 
anticipation of needing to comply with the CARB Omnibus standards that 
begin in 2024,\412\ or potential future Federal standards under this 
final rule, and agree with commenters that it's appropriate to 
recognize the effort to proactively improve emissions performance.\413\ 
Thus, allowing credits generated in MY 2022 and later both recognizes 
improvements in emissions controls beyond what is needed to meet the 
current standards, and ensures that only credits generated in the model 
years leading up to 2027 can be used to meet the standards finalized in 
this rule.
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    \411\ EPA compliance data shows that prior to MY 2022, the 
majority of heavy-duty on-highway engine manufacturers were not 
generating NOX emissions credits in recent model years 
(i.e., since model year 2009).
    \412\ EPA is reviewing a waiver request under CAA section 209(b) 
from California for the Omnibus rule.
    \413\ As discussed in this Section IV.G, the final ABT program 
does not allow manufacturers to generate emissions credits from 
engines certified to state emission standards that are different 
than the federal standards; however, as discussed in IV.G.7, 
manufacturers could generate emissions credits if they produce 
larger volumes of engines to sell outside of those states that have 
adopted emission standards that are different than the federal 
standards.
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7. Transitional Credits Generated in MYs 2022 Through 2026
    We are finalizing a transitional credit program that includes 
several pathways for manufacturers to generate transitional credits in 
MYs 2022 through 2026 that they can then use in MYs 2027 and later. The 
transitional credit pathways differ in several ways from

[[Page 4396]]

what we proposed based on further consideration, including the 
consideration of public comments. In this section, IV.G.7, we briefly 
summarize our proposed transitional credit program, stakeholder 
comments on the proposed transitional credit program, and then discuss 
EPA's responses to comments along with our rationale for the 
transitional credit pathways in the final rule.
    Under the proposed transitional credit program, manufacturers would 
generate transitional credits in model years 2024 through 2026. As 
proposed, manufacturers would have calculated transitional credits 
based on the current NOX emissions standards and useful life 
periods; however, manufacturers would have been required to certify to 
the other model year 2027 and later requirements, including the LLC and 
off-cycle test procedures. We proposed the same five-year credit life 
for transitional credits as other credits in the proposed general ABT 
program (see 87 FR 17553-17554 March 28, 2022, for additional details 
of the proposed transitional credits).
    We requested comment on our proposed approach to offer transitional 
NOX emission credits that incentivize manufacturers to adopt 
the proposed test procedures earlier than required in MY 2027. We also 
requested comment on whether CI engines should be required to meet the 
proposed off-cycle standards to qualify for the transitional credits, 
and were specifically interested in comments on other approaches to 
calculating transitional credits before MY 2027 that would account for 
the differences in our current and proposed compliance programs. In 
addition, we requested comment on our proposed five-year credit life 
for transitional NOX emission credits. Finally, we also 
requested comment related to our proposed Early Adoption Incentives on 
whether EPA should adopt an incentive that reflects the MY 2024 Omnibus 
requirements being a step more stringent than our current standards, 
but less comprehensive than the proposed MY 2027 requirements.
    Several commenters provided perspectives on the proposed 
transitional credit program under the ABT program. Most commenters 
either opposed allowing manufacturers to generate NOX 
emissions credits, or suggested additional requirements for generating 
credits that could be used in MYs 2027 and later. One commenter stated 
that due to lead time and resource constraints, manufacturers would not 
be able to participate in the proposed transitional credit program. 
Another commenter supported the proposed transitional credit program. 
One commenter also stated that incentives for compliant vehicles, not 
just ZEVs, purchased prior to the MY 2027 will bring tremendous health 
benefits to at-risk communities and the nation. Similarly, one 
commenter encouraged EPA to further incentivize emissions reductions 
prior to the start of the new standards by providing additional 
flexibilities to use credits in MY 2027 and later if manufacturers were 
able to certify prior to MY 2027 a large volume of engines (i.e., an 
entire engine service class) to almost all MY2027 and later 
requirements.
    Commenters who opposed allowing manufacturers to generate 
NOX emissions credits prior to MY2027 were concerned that 
the difference between Federal and state (i.e., CARB Omnibus) standards 
would result in ``windfall of credits'' that would allow a large 
fraction of engines to emit at the FEL cap into MY2030 and later. One 
commenter stated that EPA has not adequately assessed the potential 
erosion of emissions reductions from credits generated by engines 
certifying to the CARB Omnibus standards. Another commenter stated that 
manufacturers are already certifying to levels below the current MY2010 
standards, and they believe that certifying to the new test procedures 
will take little effort for manufacturers. The commenter stated that 
there is no need to incentivize manufacturers to adopt proposed test 
procedures ahead of MY2027 because they will already be doing so under 
the Omnibus program. They argued that rather than requiring new 
testing, EPA should encourage new technology adoption. Commenters 
opposing the transitional credit program stated that EPA should 
eliminate the transitional credit program, or if EPA choses to finalize 
the transitional credit program, then EPA should adjust the final 
standards to account for the transitional credit program impacts, or 
revise the transitional credit program (e.g., shorten credit life to 
three years, establish a separate bank for credits generated by engines 
in states adopting the Omnibus standards). Two commenters stated that 
EPA should require engines generating credits prior to 2027 to meet all 
of the requirements of 2027 and beyond; they highlighted the importance 
of the 2027 and later low-load cycle and off-cycle standards to ensure 
real-world reductions on the road, and stated that there should be 
consistency in the way credits are generated and the way they are used. 
Similarly, these commenters oppose credits for legacy engines or legacy 
technologies (i.e., engines or technologies used to meet the current 
emissions standards).
    The commenter who stated that manufacturers would be unable to 
generate credits under the proposed transitional credit due to lead 
time and resource constraints argued that manufacturers would be unable 
to adjust their engine development plans to meet the new LLC and off-
cycle test standards in MY 2024. They further stated that in many cases 
deterioration factor (DF) testing has already started for MY 2024 
engines. The commenter also argued that they view the ABT program as 
part of the emissions standards, and the proposed transitional credit 
program provided less than the four-year lead time that the CAA 
requires when setting heavy-duty criteria pollutant emissions 
standards. In addition, the commenter stated that the proposed 
transitional credit program would disincentivize manufacturers to make 
real-world NOX emissions reductions ahead of when new 
standards are in place because they would not be able to design and 
validate their engines to meet the requirements to generate credits.
    Finally, a commenter suggested EPA further encourage additional 
emissions reductions prior to the start of new standards by providing 
greater flexibility to use credits in MYs 2027 and later.\414\ 
Specifically, this commenter suggested that EPA provide a longer credit 
life (e.g., ten years compared to the five years proposed for the ABT 
program) and also allow the movement of credits between averaging sets. 
The commenter stated that in order to generate credits with these 
additional flexibilities manufacturers would need to certify an entire 
engine service class (e.g., all heavy heavy-duty engines a manufacturer 
produced) in a given model year to a FEL of 50 mg/hp-hr or less, and 
meet all other MY 2027 and later requirements. They further stated that 
it may not be appropriate for natural gas engines to generate credits 
with these additional flexibilities since natural gas engines can meet 
a 50 mg/hp-hr FEL today. Finally, the commenter stated that engines 
using these credits in MYs 2027 and later should be required to certify 
to a FEL of 50 mg/hp-hr or less. Additional details on comments 
regarding the proposed transitional credit program are included in 
section 12 of the Response to Comments document.
---------------------------------------------------------------------------

    \414\ U.S. EPA. Stakeholder Meeting Log. December 2022.
---------------------------------------------------------------------------

    After considering comments on the proposed transitional credit 
program, we are choosing to finalize a revised

[[Page 4397]]

version of the proposed transitional credit program. Similar to the 
proposed rule, we are finalizing an optional transitional credit 
program to help us meet our emission reduction goals at a faster pace, 
while also providing flexibilities to manufacturers to meet new, more 
stringent emission standards. Building on the ABT program as whole, the 
transitional credit program in the final rule can benefit the 
environment and public health in two ways. First, early introduction of 
new emission control technologies can accelerate the entrance of lower-
emitting engines and vehicles into the heavy-duty vehicle fleet, 
thereby reducing NOX emissions from the heavy-duty sector 
and lowering its contributions to ozone and PM formation before new 
standards are in place. Second, the earlier improvements in ambient air 
quality will result in public health benefits sooner than they would 
otherwise occur; these benefits are worth more to society than those 
deferred to a later time, and could be particularly impactful for 
communities already overburdened with pollution. As discussed in 
Section II, many state and local agencies have asked the EPA to further 
reduce NOX emissions, specifically from heavy-duty engines, 
because such reductions will be a critical part of many areas' 
strategies to attain and maintain the ozone and PM2.5 NAAQS. 
Several of these areas are working to attain or maintain NAAQS in 
timeframes leading up to and immediately following the required 
compliance dates of the final standards, which underscores the 
importance of the early introduction of lower-emitting vehicles.
    The transitional credit program is voluntary and as such no 
manufacturer is required to participate in the transitional credit 
program. The transitional credit program in the final rule will provide 
four pathways for manufacturers to generate credits in MYs 2022 through 
2026 for use in MYs 2027 and later: (1) In MY 2026, certify all engines 
in the manufacturer's heavy heavy-duty service class to a FEL of 50 mg/
hp-hr or less and meet all other EPA requirements for MYs 2027 and 
later to generate undiscounted credits that have additional 
flexibilities for use in MYs 2027 and later (2026 Service Class Pull 
Ahead Credits); (2) starting in MY 2024, certify one or more engine 
family(ies) to a FEL below the current MY2010 emissions standards and 
meet all other EPA requirements for MYs 2027 and later to generate 
undiscounted credits based on the longer UL periods included in the 
2027 and later program (Full Credits); (3) starting in MY 2024, certify 
one or more engine family(ies) to a FEL below the current MY2010 
emissions standards and meet several of the key requirements for MYs 
2027 and later, while meeting the current useful life and warranty 
requirements to generate undiscounted credits based on the shorter UL 
period (Partial Credits); (4) starting in MY 2022, certify one or more 
engine family(ies) to a FEL below the current MY2010 emissions 
standards, while complying with all other MY2010 requirements, to 
generate discounted credits (Discounted Credits).
    All credits generated in the first pathway have an eight-year 
credit life and can therefore be used through MY 2034. All credits 
generated under the second or third pathways will expire by MY2033; all 
credits generated in the fourth pathway will expire by MY 2030. We 
further describe each pathway and our rationale for each pathway in 
this section (see the final interim provisions in 40 CFR 1036.150(a) 
for additional details).\415\ In Section IV.G.8 we discuss our decision 
to finalize the transitional credit pathways in lieu of the proposed 
Early Adoption Incentives program (section 12 of the Response to 
Comments document includes additional details on the comments received 
on the proposed Early Adoption Incentives program).
---------------------------------------------------------------------------

    \415\ We are finalizing as proposed a requirement that, to 
generate transitional NOX emission credits, manufacturers 
must meet the applicable PM, HC, and CO emission standards without 
generating or using emission credits. For the first and second 
pathways, applicable PM, HC, and CO emission standards are in 40 CFR 
1036.104. For the third and fourth pathways (Partial and Discounted 
Credits), applicable PM, HC, and CO emission standards are in 40 CFR 
86.007-11 or 86.008-10.
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    In developing the final transitional credit program and each 
individual pathway, we considered several factors. For instance, for 
the transitional credit program as a whole, one commenter stated that 
there should be consistency in the way the credits are generated and 
the way they are used; several commenters urged EPA to only provide 
transitional credits to engines meeting all the 2027 and later 
requirements. The transitional credit program acknowledges these 
commenters' input by only providing full credit value to engines 
meeting all the 2027 and later requirements [i.e., 2026 Service Class 
Pull Ahead Credits and Full Credits pathways], while providing a lesser 
value for credits generated from engines that do not meet all of the 
2027 and later requirements but still demonstrate improved emissions 
performance compared to the current standards.
    We now turn to discussing in detail each pathway, and the factors 
we considered in developing each pathway. The first pathway 
acknowledges the significant emissions reductions that would occur if 
manufacturers were to certify an entire service class of heavy heavy-
duty engines to a much lower numeric standard than the current 
standards and meet all other MY 2027 requirements prior to the start of 
the new standards. Specifically, compared to the emissions reductions 
expected from the final rule, our assessment shows significant, 
additional reductions in the early years of the program from certifying 
the entire heavy heavy-duty engine fleet to a FEL of 50 mg/hp-hr or 
less and meeting all other MY2027 requirements in MY 2026, one model 
year prior to the start of the new standards.\416\ As discussed 
throughout this Section IV.G, emissions reductions, and the resulting 
public health benefits, that are realized earlier in time are worth 
more to society than those deferred to a later time. Based on the 
potential for additional, early emissions reductions, we are finalizing 
the 2026 Service Class Pull Ahead Credits pathway with two additional 
flexibilities for manufacturers to use the credits in MYs 2027 and 
later. First, 2026 Service Class Pull Ahead Credits have an eight-year 
credit life (i.e., expire in MY 2034), which is longer than credits 
generated in the other transitional credit pathways, or under the main 
ABT program. Second, we are allowing 2026 Service Class Pull Ahead 
Credits to move from a heavy heavy-duty to a medium heavy-duty 
averaging set; however, credits moved between averaging sets will be 
discounted at 10 percent. We note that a recent assessment by an 
independent NGO shows that allowing credits to move between service 
classes could reduce the overall monetized health benefits of a program 
similar to the one in this final rule; however, the 10 percent discount 
rate that we are apply would more than offset the potential for reduced 
emissions reductions. Moreover, as noted in this section, the early 
emissions reductions from this transitional credit program would 
provide important positive benefits, particularly in communities

[[Page 4398]]

overburdened with pollution.\417\ Further, we are balancing these 
additional flexibilities with restrictions on which engines can 
participate in the 2026 Service Class Pull Ahead Credits pathway. 
Specifically, only heavy heavy-duty engines may generate 2026 Service 
Class Pull Ahead Credits; we expect a much lower level of investment 
would be required for natural gas-fueled engines, light heavy-duty 
engines, and SI engines to meet the 2026 Service Class Pull Ahead 
Credits requirements compared to the investment needed for heavy- 
heavy-duty engines. We expect that the combination of discounting 
credits moved across averaging sets and only allowing the heavy heavy-
duty engine service class to participate in the 2026 Service Class Pull 
Ahead Credits pathway will appropriately balance the potential for 
meaningful emissions reductions in the early years of the program with 
the potential for adverse competitive disadvantages or environmental 
risks from either unequal investments to generate credits or producing 
large volumes of credits from engines that could easily meet the 
requirements of the 2026 Service Class Pull Ahead Credits pathway. 
Finally, engines certified using 2026 Service Class Pull Ahead Credits 
in 2027 through 2034 will need to meet a FEL of 50 mg/hp-hr or less; 
this requirement helps to ensure that these credits are used only to 
certify engines that are at least as low emitting as the engines that 
generated the credits.
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    \416\ See RIA Chapter 5.5.5 for additional details on our 
assessment of emissions reductions projected to occur from 
certifying engines to a FEL of 50 mg/hp-hr and meeting all other 
2027 requirements in MY 2026. Note that for the purposes of bounding 
the potential emissions impacts, we assumed all heavy heavy-duty 
engines would participate in the 2026 Service Class Pull Ahead 
Credits pathway, and that those credits would be used by both medium 
and heavy heavy-duty engines in MY 2027 and later, until 
manufacturers used all of the credits.
    \417\ See U.S. EPA. Stakeholder Meeting Log. December 2022 for 
details of the assessment by the independent NGO (ICCT).
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    The second pathway (Full Credits) acknowledges the emissions 
reductions that could be achieved prior to the start of new standards 
if manufacturers certify to a FEL lower than today's standard and meet 
all other MY 2027 and later requirements, although without doing so for 
an entire engine service class. This pathway is similar to our proposed 
transitional credit program and is consistent with input from 
commenters who highlighted the importance of meeting MY 2027 and later 
requirements such as the low-load cycle and off-cycle standards to 
ensure real-world reductions on the road. As proposed, all heavy-duty 
engine service classes, including heavy-duty natural gas engines in the 
respective service classes, can participate in this pathway.
    The third pathway (Partial Credits) incentivizes manufacturers to 
produce engines that meet several of the key final requirements for MY 
2027 and later, including the LLC and off-cycle standards for 
NOX, while meeting the existing useful life and warranty 
periods.\418\ This pathway allows manufacturers to adopt new emissions 
control technologies without demonstrating durability over the longer 
useful life periods required in MY 2027 and later, or certifying to the 
longer warranty periods in the final rule. We expect that some 
manufacturers may already be planning to produce such engines in order 
to comply with 2024 California Omnibus program; however, this 
transitional pathway would incentivize manufacturers to produce greater 
volumes of these engines than they would otherwise do to comply in 
states adopting the Omnibus standards. Some commenters were concerned 
that the proposed transitional credit program would result in 
``windfall credits'' due to manufacturers generating credits from 
engines produced to comply with more stringent state standards. As 
discussed in IV.G, the final program will not allow manufacturers to 
generate credits from engines certified to meet state standards that 
are different from the Federal standards.\419\ The Partial Credits 
pathway thus avoids ``windfall credits'' because manufacturers are not 
allowed to generate credits from engines produced to meet the more 
stringent 2024 Omnibus requirements, but rather are incentivized to 
produce cleaner engines that would benefit areas of the country where 
such engines may not otherwise be made available (i.e., outside of 
states adopting the Omnibus program).\420\ Further, because engines 
participating in this pathway will be certified to shorter useful life 
periods, they will generate fewer credits than engines participating in 
the third and fourth pathways (Full Credits and 2026 Service Class Pull 
Ahead Credits).
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    \418\ Engines earning Partial Credits must comply with 
NOX standards over the Low Load Cycle and the off-cycle 
standards. The family emission limits for the Low Load Cycle and 
off-cycle standards are calculated relative to the family emission 
limit the manufacturer declares for FTP testing, as described in 40 
CFR 1036.104(c). If we direct a manufacturer to do in-use testing 
for an engine family earning Partial Credits, we may direct the 
manufacturer to follow either the in-use testing program specified 
in 40 CFR part 1036 for NOX, or the in-use testing 
program in 40 CFR part 86 for all criteria pollutants. Except for 
the NOX standards for the Low Load Cycle and for off-
cycle testing, engines generating Partial Credits would be subject 
to all the certification and testing requirements from 40 CFR part 
86.
    \419\ See final part 1036, subpart H, and 40 CFR 1036.801 (which 
EPA did not propose any revisions to in the proposed migration from 
part 86, subpart A, to part 1036). See also the substantively 
similar definition of U.S.-directed production in current 40 CFR 
86.004-2. Under 40 CFR 1036.705(c), which we are also finalizing as 
proposed as applicable for NOX ABT, compliance through 
ABT does not allow credit calculations to include engines excluded 
from the definition of U.S.-directed production volume: ``As 
described in Sec.  1036.730, compliance with the requirements of 
this subpart is determined at the end of the model year based on 
actual U.S.-directed production volumes. Keep appropriate records to 
document these production volumes. Do not include any of the 
following engines to calculate emission credits: . . . (4) Any other 
engines if we indicate elsewhere in this part 1036 that they are not 
to be included in the calculations of this subpart.''
    \420\ EPA is reviewing a waiver request under CAA section 209(b) 
from California for the Omnibus rule.
---------------------------------------------------------------------------

    The first, second, and third pathways all include meeting the LLC 
requirements for MY 2027 and later. One commenter suggested meeting the 
LLC would require manufacturers to simply meet a lower numeric standard 
than the current standard; however, EPA disagrees. Certifying to the 
LLC will require more than simply meeting a lower numeric standard 
since the LLC is a new test cycle that requires demonstration of 
emissions control in additional engine operations (i.e., low load) 
compared to today's test cycles (see preamble Section III and section 3 
of the Response to Comments document and for more discussion on the 
LLC).
    Finally, the fourth pathway (Discounted Credits) allows 
manufacturers to generate credits for use in MY 2027 and later with 
engines that are not designed to meet the LLC and off-cycle standards 
and so could provide additional compliance flexibility for meeting the 
final standards; however, since the engines are not meeting the full 
requirements of the MY 2027 and later program the credits are 
discounted and will expire before credits generated in the other 
transitional credit pathways. This Discounted Credits pathway includes 
consideration of input from one commenter who stated that it would be 
infeasible for manufacturers to comply with the new LLC and off-cycle 
test procedures in MY 2024 in order to generate credits under the 
proposed credit program; they further argued that for manufacturers 
relying on credits to comply with the final standards, the proposed 
transitional credit program would not provide the lead time required by 
the CAA. As described in Section III of this preamble, the new 
standards in the final rule are feasible without the ABT program and 
without the use of transitional credits; participation in ABT is 
voluntary and is intended to provide additional flexibility to 
manufacturers through an optional compliance pathway. While 
manufacturers have the option of generating NOX emissions 
credits under the transitional credit program in the final rule, they 
are not required to do so. The four-year lead time requirement under 
CAA 202(a)(3) does not apply to these ABT provisions.

[[Page 4399]]

    Nevertheless, the final rule allows credits generated under this 
Discounted Credits pathway to incentivize improvements in emissions 
controls, even if the engines are not certified to the full MY2027 and 
later requirements. Credits will be discounted by 40 percent to account 
for differences in NOX emissions during low-load and off-
cycle operations between current engines and engines certifying to the 
model year 2027 and later requirements. While we expect that 
manufacturers certifying to a FEL below the current 200 mg/hp-hr 
standard will reflect improvement in emissions control over the FTP and 
SET duty-cycles, the discount applied to the credits accounts for the 
fact that these engines are not required to maintain the same level of 
emissions control over all operations of the off-cycle standards, or 
during the low-load operations of the LLC. For example, a manufacturer 
certifying a HHDE engine family to a FEL of 150 mg/hp-hr and all other 
MY 2010 requirements with a U.S.-directed production volume of 50,000 
engines in 2024 would generate approximately 5,000 credits (see 
Equation IV-1), which they would then multiply by 0.6 to result in a 
final credit value of 3,000 credits. See the final, revised from 
proposal, interim provision in 40 CFR 1036.150(a)(1) for additional 
details on the calculation of discounted credits.
    Credits generated under this Discounted Credits pathway could be 
used in MY 2027 through MY 2029. The combination of the discount and 
limited number of model years in which manufacturers are allowed to use 
these credits is consistent with our past practice and helps to 
addresses some commenters' concerns about allowing legacy engines to 
generate credits, or credits generated under the transitional credit 
program eroding emissions reductions expected from the rule (55 FR 
30584-30585, July 26,1990). There are two primary ways that the 
Discounted Credits pathway results in positive public health impacts. 
First, an immediate added benefit to the environment is the discounting 
of credits, which ensures that there will be a reduction of the overall 
emission level. The 40 percent discount provides a significant public 
health benefit, while not being so substantial that it would discourage 
the voluntary initiatives and innovation the transitional ABT program 
is designed to elicit. Second, consistent with the benefits of the 
overall transitional credit program, when the ``time value'' of 
benefits (i.e., their present value) is taken into account, benefits 
realized in the near term are worth more to society than those deferred 
to a later time. The earlier expiration date of credits in the 
Discounted Pathway reflects that these credits are intended to help 
manufacturers transition in the early years of the program, but we 
don't think they are appropriate for use in later years of the program. 
The earlier expiration of credits is also consistent with comments that 
we should finalize a 3-year credit life for transitional credits (i.e., 
credits can be used for 3-years once the new standards begin).
    As discussed earlier in this Section IV.G.7, credits generated 
under the first pathway (2026 Service Class Pull Ahead Credits) can be 
used for eight years, through MY 2034; we selected this expiration date 
to balance incentivizing manufacturers to participate in the 2026 
Credits pathway and thereby realize the potential for additional, early 
emissions reductions, with continuing to encourage the introduction of 
improved emissions controls, particularly as the heavy-duty fleet 
continues to transition into zero emissions technologies.\421\ As 
stated in the preceding paragraphs, all credits generated in the second 
and third pathways can be used through MY 2032. Our rationale for this 
expiration date is two-fold. First, providing a six-year credit life 
from when the new standards begin provides a longer credit life than 
provided in the final ABT program for credits generated in MY 2027 and 
later; similar to the first pathway, this longer credit life 
incentivizes manufacturers to produce engines that emit lower levels of 
NOX earlier than required. Second, the six-year credit life 
balances additional flexibility for manufacturers to transition over 
all of their product lines with the environmental and human health 
benefits of early emissions reductions. This transitional period 
acknowledges that resource constraints may make it challenging to 
convert over all product lines immediately when new standards begin, 
but maintains emission reductions projected from program by requiring 
the use of credits to certify engines that emit above the level of the 
new standard. While some commenters stated that manufacturers will have 
been complying with the CARB Omnibus program starting in 2024, we 
acknowledge that complying with the 2027 and later Federal standards 
will require another step in technology and thus think it is 
appropriate to provide additional flexibility for manufacturers to 
transition to the new standards through the use of emissions credits in 
the ABT program.
---------------------------------------------------------------------------

    \421\ As discussed in RIA 5.5.5, our evaluation shows that 
manufacturers would use all 2026 Service Class Pull Ahead Credits in 
about an eight-year period, which further supports the eight-year 
credit life of the 2026 Service Class Pull Ahead Credits pathway.
---------------------------------------------------------------------------

    This section describes how to generate credits for MY 2026 and 
earlier engines that are certified to standards under 40 CFR part 86, 
subpart A. As noted in Section III.A.3, we are allowing manufacturers 
to continue to certify engines to the existing standards for the first 
part of model year 2027. While those engines continue to be subject to 
standards under 40 CFR part 86, subpart A, we are not allowing those 
engines to generate credits that carry forward for certifying engines 
under 40 CFR part 1036.\422\ Manufacturers may only generate 
NOX emissions credits under transitional credit pathways for 
MY 2024-2026 engines since one purpose of transitional credits is to 
incentivize emission reductions in the model years leading up to MY 
2027. To the extent manufacturers choose to split MY 2027, the engines 
produced in the first part of the split MY are produced very close in 
time to when the new standards will apply, and thus we expect that 
rather than incentivizing earlier emission reductions, providing an 
allowance to generate NOX emission credits would incentivize 
production at higher volumes during the first part of the split MY than 
would otherwise occur (i.e., incentivizing more of the MY 2027 
production before the final standards apply). The higher production 
volume of engines in the first part of the split MY could thereby 
result in additional NOX emission credits without additional 
emission reductions that would otherwise occur. See preamble Section 
III.A.3 for details on the split model year provision in this final 
rule.
---------------------------------------------------------------------------

    \422\ MY 2027 engines produced prior to four years after the 
date that the final rule is promulgated and certified to the 
existing 40 CFR part 86 standards cannot participate in the part 
1036 ABT program; however, MY 2027 engines certified to 40 CFR part 
1036 standards and requirements may participate in the ABT program 
specified in 40 CFR part 1036, subpart H.
---------------------------------------------------------------------------

8. Early Adoption Incentives
    EPA is choosing not to finalize the Early Adoption Incentives 
program as proposed. This includes a decision not to include emissions 
credit multipliers in the final ABT program. Rather, we are finalizing 
a revised version of the transitional credit program under the ABT 
program as described above in Section IV.G.7. In this Section IV.G.8 we 
briefly describe the proposed Early Adoption Incentives program, 
stakeholder comments on the proposed Early Adoption Incentives program, 
and then discuss EPA's responses to comments along with our rationale 
for

[[Page 4400]]

choosing not to finalize the Early Adoption Incentives program.
    We proposed an early adoption incentive program that would allow 
manufacturers who demonstrated early compliance with all of the final 
MY 2027 standards (or MY 2031 standards under proposed Option 1) to 
include Early Adoption Multiplier values of 1.5 or 2.0 when calculating 
NOX emissions credits. In the proposed Early Adoption 
Incentives program, manufacturers could generate credits in MYs 2024 
through 2026 and use those credits in MYs 2027 and later.
    We requested comment on all aspects of our proposed early adoption 
incentive program. We were aware that some aspects of the proposed 
requirements could be challenging to meet ahead of the required 
compliance dates, and thus requested comment on any needed 
flexibilities that we should include in the early adoption incentive 
program in the final rule. See 87 FR 17555, March 28, 2022, for 
additional discussion on the proposed Early Adoption Incentives 
program, including specifics of our requests for comment.
    Several commenters provided general comments on the proposed Early 
Adoption Incentive program. Although many of the commenters generally 
supported incentives such as emissions credit multipliers to encourage 
early investments in emissions reductions technology, several were 
concerned that the emissions credit multipliers would result in an 
excess of credits that would undermine some of the benefits of the 
rule; other commenters were concerned that the multipliers would 
incentivize some technologies (e.g., hybrid powertrains, natural gas 
engines) over others (e.g., battery-electric vehicles).
    As described in preamble Section IV.G.7, the revised transitional 
credit program that we are finalizing provides discounted credits for 
engines that do not comply with all of the MY 2027 and later 
requirements. In addition, after consideration of comments responding 
to our request for comment about incentivizing early reductions through 
our proposed transitional and Early Adoption Incentive program, the 
final transitional credit program includes an additional pathway that 
incentivizes manufacturers to produce engines that meet several of the 
key final requirements for MY 2027 and later, including the LLC and 
off-cycle standards for NOX, while meeting the current 
useful life and warranty periods. We expect that this transitional 
credit pathway will incentivize manufacturers to produce greater 
volumes of the same or similar engines that they plan to produce to 
comply with the MY 2024 Omnibus requirements. By choosing not to 
finalize the Early Adoption Incentives program and instead finalizing a 
modified version of the Transitional Credit program, we are avoiding 
the potential concern some commenters raised that the credit 
multipliers would result in a higher volume or magnitude of higher-
emitting MY 2027 and later engines compared to a program without 
emission credit multipliers. We believe the Transitional Credit program 
we are finalizing will better balance incentivizing emissions reduction 
technologies prior to MY 2027 against avoiding an excess of emissions 
credits that leads to much greater volumes or magnitudes of higher-
emitting engines in MYs 2027 and later. Moreover, by not finalizing the 
Early Adoption Incentive program we are avoiding any concerns that the 
emissions credit multipliers would incentivize some technologies over 
others (see section 12.5 of the Response to Comments and preamble 
Section IV.G.10 for additional discussion on battery-electric and fuel 
cell electric vehicles in the final rule; see section 3 of the Response 
to Comments for discussion on additional technology pathways).
9. Production Volume Allowance
    After further consideration, including consideration of public 
comments, EPA is finalizing an interim production volume allowance for 
MYs 2027 through 2029 in 40 CFR 1036.150(k) that is consistent with our 
request for comment in the proposal, but different in several key 
aspects. In particular, the production volume allowance we are 
finalizing allows manufacturers to use NOX emissions credits 
to certify a limited volume of heavy heavy-duty engines compliant with 
pre-MY 2027 requirements in MYs 2027 through 2029.\423\ In addition, 
since we are requiring the use of credits to certify MY 2010 compliant 
heavy heavy-duty engines in the early years of the final program, and 
to aid in implementation, we are choosing to not limit the applications 
that are eligible for this production volume allowance. Finally, the 
production volume allowance in the final rule will be five percent of 
the average U.S.-directed production volumes of Heavy HDE over three 
model years, see 40 CFR 1036.801, and thus excludes engines certified 
to different emission standards in CA or other states adopting the 
Omnibus program. In this section, IV.G.9, we summarize our request for 
comment on a production volume allowance, related stakeholder comments, 
and EPA's responses to comments along with our rationale for the 
production volume allowance in the final rule.
---------------------------------------------------------------------------

    \423\ Engines certified under this production volume allowance 
would meet the current, pre-MY 2027 engine provisions of 40 CFR part 
86, subpart A.
---------------------------------------------------------------------------

    In the proposal we stated that we were considering a flexibility to 
allow engine manufacturers, for model years 2027 through 2029 only, to 
certify up to five percent of their total production volume of heavy-
duty highway CI engines in a given model year to the current, pre-MY 
2027 engine provisions of 40 CFR part 86, subpart A. We stated the 
allowance would be limited to Medium HDE or Heavy HDE engine families 
that manufacturers show would be used in low volume, specialty 
vocational vehicles. We noted that such an allowance from the MY 2027 
criteria pollutant standards may be necessary to provide engine and 
vehicle manufacturers additional lead time and flexibility to redesign 
some low sales volume products to accommodate the technologies needed 
to meet the proposed more stringent engine emission standards.
    We requested comment on the potential option of a three-year 
allowance from the proposed MY 2027 criteria pollutant standards for 
engines installed in specialty vocational vehicles, including whether 
and why the flexibility would be warranted and whether 5 percent of a 
manufacturers engine production volume is an appropriate value for such 
an interim provision. In addition, we requested comment on whether the 
flexibility should be limited to specific vocational vehicle regulatory 
subcategories and the engines used in them.
    Several commenters provided perspectives on our request for comment 
on providing an additional flexibility that would allow manufacturers 
to certify up to five percent of their total production volume of 2027 
through 2029 MY medium and heavy HDEs to the current Federal engine 
provisions. Many environmental and state organizations opposed the 
potential production volume allowance, while most manufacturers and one 
supplier generally supported the potential allowance although they 
suggested changes to the parameters included in the proposal.
    Commenters opposing the production volume allowance had two primary 
concerns. First, they stated that the production volume flexibility is 
not needed because there is enough lead time between now and MY 2027 to 
develop the technologies and overcome any packaging challenges. One 
commenter further noted that the CARB

[[Page 4401]]

Omnibus standards would already be in effect in 15 percent of the 
market. Second, commenters argued that the production volume allowance 
would result in high NOX emissions and adverse health 
effects, particularly in high-risk areas, which would undermine the 
effectiveness of the rule to reduce emissions and protect public 
health. One commenter noted that HHDEs last for many years before being 
scrapped and that the production volume allowance, combined with other 
flexibilities in the proposal, could result in significant emissions 
impacts for many years to follow, which would create extreme difficulty 
for California and other impacted states to achieve air quality goals. 
Another commenter estimated that in MY 2027 through 2029, the 
production volume allowance would result in 20,000 vehicles emitting 
nearly 6 times more NOX on the FTP cycle than proposed 
Option 1, and that these vehicles could represent 20-25 percent of the 
total NOX emissions from MY 2027 through 2029 vehicles. 
Still another commenter stated that the production volume allowance 
would result in up to a 45 percent increase in NOX emissions 
inventory for each applicable model year's production from a 
manufacturer with products in a single useful life and power rating 
category; the commenter noted that the emissions inventory impact could 
be even greater if a manufacturer used the five percent allowance for 
engines with longer useful life periods and higher power ratings. One 
commenter opposing the production volume allowance stated that EPA 
should not exempt any engines from complying with the adopted new 
emission standards for any amount of time. Other commenters opposing 
the production volume allowance stated that if EPA chose to finalize a 
production allowance then emissions from those engines should be offset 
with ABT emission credits to protect vulnerable impacted communities. 
Finally, one commenter opposing the production volume allowance state 
that if EPA chose to finalize the production allowance then the Agency 
should provide strong technical justification for each engine category 
subject to the provision.
    Commenters generally supporting the production volume allowance 
suggested several ways to further limit the flexibility, or suggested 
additional flexibilities based on the CARB Omnibus program. For 
instance, several engine manufacturers and their trade association 
suggested limiting the provision to include only engines with low 
annual miles traveled to minimize the emissions inventory impacts. 
These commenters suggested limiting the allowance to engines with 
greater than or equal to 525 hp or 510 hp in specific vehicle 
applications, namely: Heavy-haul tractors and custom chassis motor 
homes, concrete mixers, and emergency vehicles. Two engine 
manufacturers further suggested the production volume allowance include 
vehicles where aftertreatment is mounted off the frame rails, or that 
EPA review and approve applications demonstrating severe packaging 
constraints for low volume, highly specialized vocational applications. 
Another engine manufacturer argued that manufacturers need to be able 
to carry over some existing engines into MY 2027 and later for a few 
years in order to adequately manage investments and prioritize ultra-
low NOX and ZEV technology adoption in the applications that 
make the most sense. They further stated that EPA should consider 
alternate credit program options that can be used to truly manage 
investment and to prioritize appropriate applications by allowing 
manufacturers to leverage credits to stage development programs. One 
engine manufacturer and one supplier suggested EPA consider programs 
similar to the CARB Omnibus' separate certification paths for `legacy 
engines,' emergency vehicles, and low-volume high horsepower engines. 
Additional details on comments received on the request for comment on a 
potential production volume allowance are available in section 12.7 of 
the Response to Comments.
    After considering comments on the proposed production volume 
allowance, we are finalizing an allowance in MY 2027 through 2029 for 
manufacturers to certify up to five percent of their Heavy HDE U.S.-
directed production volume averaged over three model years (MY 2023 
through 2025) as compliant with the standards and other requirements of 
MY 2026 (i.e., the current, pre-MY 2027 engine provisions of 40 CFR 
part 86, subpart A). As explained earlier in this Section IV.G, U.S.-
directed production volume excludes engines certified to different 
state emission standards (e.g., would exclude engines certified to CARB 
Omnibus standards if EPA grants the pending waiver request), and thus 
would be a smaller total volume than all Heavy HDE engine production in 
a given model year.424 425 By finalizing a production volume 
allowance based on the average U.S.-directed production volume over 
three model years (MY 2023 through 2025), rather than an allowance that 
varies by production volume in each of the model years included in the 
allowance period (MY 2027 through 2029), we are providing greater 
certainty to manufacturers and other stakeholders regarding the number 
of engines that could be produced under this allowance. Further, we 
avoid the potential for economic conditions in any one year to unduly 
influence the volume of engines that could be certified under this 
allowance. Based on EPA certification data, we estimate that five 
percent MY 2021 Heavy HDE would result in approximately 12,000 engines 
per year permitted under this allowance.\426\
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    \424\ See final part 1036, subpart H, and 40 CFR 1036.801.
    \425\ EPA is reviewing a waiver request under CAA section 209(b) 
from California for the Omnibus rule.
    \426\ We note that there would be fewer engines eligible for 
this allowance in the event we approve the pending waiver request 
since our existing regulations provide that the production volume 
allowance would exclude engines certified to state emission 
standards that are different than the federal standards.
---------------------------------------------------------------------------

    We are limiting the final production volume allowance to Heavy HDE, 
rather than Heavy HDE and Medium HDE as proposed, because comments from 
manufacturers generally pointed to Heavy HDE applications or otherwise 
suggested limiting the allowance to larger engines (e.g., greater than 
510 hp). After considering comments on the vehicle categories to 
include in the production volume allowance, we are choosing not to 
specify the vehicle categories for engines certified under this 
production volume. Our rationale includes three main factors. First, we 
are requiring manufacturers to use credits to certify engines under the 
production volume allowance, which will inherently result in the 
production of lower-emitting engines to generate the necessary credits. 
We believe requiring emission credits to certify engines under the 
production volume allowance better protects the expected emission 
reductions from the final rule than limiting the production allowance 
to specific vehicle categories. Our approach is consistent with some 
commenters' recommendation to finalize a program that required the use 
of emission credits to protect vulnerable impacted communities by 
ensuring that lower-emitting engines are produced earlier to generate 
the credits necessary to produce engines certified under this 
allowance. Second, a variety of vehicle categories were identified in 
comments as vehicle categories for which manufacturers may need 
additional lead time and flexibility to redesign to accommodate the 
technologies needed to meet the final emission standards. We expect 
that the specific vehicle

[[Page 4402]]

category(ies) for which additional lead time and flexibility is of 
interest will vary by manufacturer, and thus are choosing not to 
specify vehicle categories to avoid competitive disruptions. Finally, 
we are choosing not to limit the production volume allowance to 
specific vehicle categories to simplify and streamline implementation; 
the specific vehicle in which an engine will be installed is not always 
known when an engine is produced, which would make implementing 
restrictions on engines installed in specific vehicle categories 
challenging for both EPA and manufacturers.
    We continue to believe it is important to ensure that technology 
turns over in a timely manner and that manufacturers do not continue 
producing large numbers of higher-emitting pre-MY 2027 compliant 
engines once the MY 2027 standards are in place. The combination of a 
limited production volume (i.e., five percent of the average U.S.-
directed production volume over three model years, (MY 2023 through 
2025, in MYs 2027 through 2029) and a requirement to use credits will 
prevent the production of large numbers of these higher emitting 
engines, while providing additional flexibility for manufacturers to 
redesign engine product lines to accommodate the technologies needed to 
meet the final emission standards.
    For engines certified under the production volume allowance, 
manufacturers would need to meet the standards and related requirements 
that apply for model year 2026 engines under 40 CFR part 86, subpart A. 
Engine families must be certified as separate engine families that 
qualify for carryover certification, which means that the engine family 
would still be properly represented by test data submitted in an 
earlier model year.
    Manufacturers would need to declare a NOX family 
emission limit (FEL) that is at or below the standard specified in 40 
CFR 86.007-11 and calculate negative credits by comparing the declared 
NOX FEL to the FTP emission standard for model year 2027 
engines. In addition, manufacturers would calculate negative credits 
using a value for useful life of 650,000 miles to align with the credit 
calculation for engines that will be generating credits under 40 CFR 
part 1036 starting in model year 2027 (see Equation IV-I for credit 
calculation). The inclusion of useful life and work produced over the 
FTP in the calculation of credits addresses some commenters' concern 
regarding the production of engines with higher power ratings and 
longer useful life periods under the production volume allowance. 
Manufacturers would need to demonstrate compliance with credit 
accounting based on the same ABT reporting requirements that apply for 
certified engines under 40 CFR part 1036.
    See 40 CFR 1036.150(k) for additional details on the limited 
production volume allowance in the final rule.
10. Zero Emission Vehicle NOX Emission Credits
    After further consideration, including consideration of public 
comments, EPA is not finalizing the proposed allowance for 
manufacturers to generate NOX emissions credits from heavy-
duty zero emissions vehicles (ZEVs). Rather, the current 40 CFR 86.016-
1(d)(4), which specifies that heavy-duty ZEVs may not generate 
NOX or PM emission credits, will continue to apply through 
MY 2026, after which 40 CFR 1037.1 will apply. The final 40 CFR 1037.1 
migrates without revisions the text of 40 CFR 86.016-1(d)(4), rather 
than the revisions we proposed to allow manufacturers to generate 
NOX emissions credits from ZEVs.427 428 In this 
Section IV.G.10, we briefly describe the proposal to allow 
manufacturers to generate NOX emissions credits from ZEVs; 
the comments received on the proposal to allow ZEV NOX 
credits; and EPA's response to those comments, which includes our 
rationale for the approach to ZEV NOX credits in the final 
rule.
---------------------------------------------------------------------------

    \427\ At the time of proposal, we referred to battery-electric 
vehicles (BEVs) and fuel cell electric vehicles (FCEVs); in this 
final rule we generally use the term zero emissions vehicles (ZEVs) 
to collectively refer to both BEVs and FCEVs.
    \428\ As proposed, we are consolidating certification 
requirements for BEVs and FCEVs over 14,000 pounds GVWR in 40 CFR 
part 1037 such that manufacturers of BEVs and FCEVs over 14,000 
pounds GVWR would certify to meeting the emission standards and 
requirements of part 1037, as provided in the current 40 CFR 1037.1. 
The final 1037.1 migrates without revisions the text of 40 CFR 
86.016-1(d)(4), rather than the revisions we proposed to allow 
manufacturers to generate NOX emissions credits from BEVs 
and FCEVs. See preamble Section III for additional details on the 
migration of 40 CFR 86.016-1(d)(4) to 40 CFR 1037.1.
---------------------------------------------------------------------------

    We proposed that if manufacturers met certain requirements, then 
they could generate NOX emissions credits from battery-
electric vehicles, BEVs, and fuel cell electric vehicles, FCEVs; we 
refer to BEVs and FCEVs collectively as zero emissions vehicles, 
ZEVs.\429\ Under the proposal, manufacturers would calculate the value 
of NOX emission credits generated from ZEVs using the same 
equation provided for engine emission credits (see Equation IV-1 in 
final preamble Section IV.G.2). To generate the inputs to the equation, 
we proposed that manufacturers would submit test data at the time of 
certification, which is consistent with requirements for CI and SI 
engine manufacturers to generate NOX emissions credits. We 
proposed that vehicle manufacturers, rather than powertrain 
manufacturers, would generate vehicle credits for ZEVs since vehicle 
manufacturers already certify ZEVs to GHG standards under 40 CFR part 
1037. To ensure that ZEV NOX credits were calculated 
accurately, and reflected the environmental and public health benefits 
of vehicles with zero tailpipe emissions over their full useful life, 
we proposed that in MY 2024 and beyond, ZEVs used to generate 
NOX emission credits would need to meet certain battery and 
fuel cell performance requirements over the useful life period (i.e., 
durability requirements).
---------------------------------------------------------------------------

    \429\ We also proposed to allow manufacturers to optionally test 
the hybrid engine and powertrain together, rather than testing the 
engine alone, to demonstrate the NOX emission performance 
of hybrid electric vehicle (HEV) technologies; if the emissions 
results of testing the hybrid engine and powertrain together showed 
NOX emissions lower than the final standards, then 
manufacturers could choose to participate in the NOX ABT 
program; see preamble Section III.A for details on HEVs in the final 
rule.
---------------------------------------------------------------------------

    We requested comment on the general proposed approach of allowing 
ZEVs to generate NOX credits, which could then be used in 
the heavy-duty engine ABT program. We also requested comment on several 
specific aspects of our proposal. See 87 FR 17558, March 28, 2022, for 
additional discussion on the proposal to allow manufacturers to 
generate NOX emissions credits from ZEVs if those vehicles 
met the specified requirements.
    Numerous commenters provided feedback on EPA's proposal to allow 
manufacturers to generate NOX emissions credits from ZEVs. 
The majority of commenters oppose allowing manufacturers to generate 
NOX emissions credits from ZEVs. Several additional 
commenters oppose ZEV NOX emissions credits unless there 
were restrictions on the credits (e.g., shorter credit life, sunsetting 
credit generation in 2026). Other commenters support allowing 
manufacturers to generate NOX emissions credits from 
electric vehicles. Arguments from each of these commenter groups are 
summarized immediately below.
    Commenters opposing NOX emissions credits for ZEVs 
present several lines of argument, including the potential for: (1) 
Substantial impacts on the emissions reductions expected from the 
proposed rule, which could also result in disproportionate impacts in 
disadvantaged communities already

[[Page 4403]]

overburdened with pollution; (2) a lack of improvements in conventional 
engine technologies; and (3) ZEV NOX credits to result 
higher emissions from internal combustion engines, rather than further 
incentivizing additional ZEVs (further noting that other State and 
Federal actions are providing more meaningful and less environmentally 
costly HD ZEV incentives). Stakeholders opposing NOX 
emissions credits from ZEVs were generally environmental or state 
organizations, or suppliers of heavy-duty engine and vehicle 
components.
    In contrast, several commenters support allowing manufacturers to 
generate these credits. Many of these commenters are heavy-duty engine 
and vehicle manufacturers. Commenters supporting an allowance to 
generate NOX emissions credits from ZEVs also provided 
several lines of argument, including the potential for: (1) ZEVs to 
help meet emissions reductions and air quality goals; (2) ZEV 
NOX credits to be essential to the achievability of the 
standards for some manufacturers; and (3) ZEV NOX credits to 
allow manufacturers to manage investments across different products and 
ultimately result in increased ZEV deployment. Each of these topic 
areas is discussed further in section 12.5 of the Response to Comments 
document.
    Three considerations resulted in our decision not to finalize at 
this time the allowance for manufacturers to generate NOX 
emissions credits from heavy-duty ZEVs. First, the standards in the 
final rule are technology-forcing, yet achievable for MY2027 and later 
internal combustion engines without this flexibility. Second, since the 
final standards are not based on projected utilization of ZEV 
technology, and given that we believe there will be increased 
penetration of ZEVs in the HD fleet by MY2027 and later, we are 
concerned that allowing NOX emissions credits would result 
in fewer emissions reductions than intended from this rule.\430\ For 
example, by allowing manufacturers to generate ZEV NOX 
credits, EPA would be allowing higher emissions (through engines using 
credits to emit up to the FEL cap) in MY 2027 and later, without 
requiring commensurate emissions reductions (through additional ZEVs 
beyond those already entering the market without this rule), which 
could be particularly impactful in communities already overburdened by 
pollution. Third, we continue to believe that testing requirements to 
ensure continued battery and fuel cell performance over the useful life 
of a ZEV may be important to ensure the zero-emissions tailpipe 
performance for which they are generating NOX credits; 
however, after further consideration, including consideration of public 
comments, we believe it is appropriate to take additional time to work 
with industry and other stakeholders on any test procedures and other 
specifications for ZEV battery and fuel cell performance over the 
useful life period of the ZEV (see section 12.6 of the Response to 
Comments document for additional detail on comments and EPA responses 
to comments on the proposed ZEV testing and useful life and warranty 
requirements).
---------------------------------------------------------------------------

    \430\ For example, the recently passed Inflation Reduction Act 
(IRA) has many incentives for promoting zero-emission vehicles, see 
Sections 13403 (Qualified Clean Vehicles), 13404 (Alternative Fuel 
Refueling Property Credit), 60101 (Clean Heavy-Duty Vehicles), 60102 
(Grants to Reduce Air Pollution at Ports), and 70002 (United States 
Postal Service Clean Fleets) of H.R. 5376.
---------------------------------------------------------------------------

    In section 12.6 of the Response to Comments document, we further 
discuss each of these considerations in our decision not to finalize 
the allowance for manufacturers to generate NOX emissions 
credits from ZEVs. Additional detail on comments received and EPA 
responses to comments, including comments on more specific aspects of 
comments on the proposed allowance for ZEV NOX emissions 
credits, such as testing, useful life, and warranty requirements for 
ZEVs, are also available in section 12.6 of the Response to Comments 
document. Our responses to comments on the proposed vehicle 
certification for ZEVs are summarized in preamble Section III, with 
additional detail in section 12.6.3 of the Response to Comments 
document.

V. Program Costs

    In Chapter 3 of the RIA, we differentiate between direct, indirect, 
and operating costs when estimating the costs of the rule. ``Direct'' 
costs represent the direct manufacturing costs of the technologies we 
expect to be used to comply with the final standards over the final 
useful lives; these costs accrue to the manufacturer. In this section 
we use those costs to estimate the year-over-year manufacturing costs 
going forward from the first year of implementation. ``Indirect'' 
costs, i.e., research and development (R&D), administrative costs, 
marketing, and other costs of running a company, are associated with 
the application of the expected technologies and also accrue to the 
manufacturer. Like direct costs, indirect costs are expected to 
increase under the final standards, in part due to the useful life 
provisions. Indirect costs are also expected to increase under the 
final program due to the warranty provisions. We term the sum of these 
direct and indirect costs ``technology costs'' or ``technology package 
costs.'' They represent the costs incurred by manufacturers--i.e., 
regulated entities--to comply with the final program.\431\ 
``Operating'' costs represent the costs of using the technology in the 
field. Operating costs include, for example, changes in diesel exhaust 
fluid (DEF) consumption or fuel consumption. These costs accrue to the 
owner/operator of MY 2027 and later heavy-duty vehicles.\432\ We 
present total costs associated with the final program in Section V.C. 
All costs are presented in 2017 dollars consistent with the proposed 
cost analysis, unless noted otherwise.
---------------------------------------------------------------------------

    \431\ More precisely, these technology costs represent costs 
that manufacturers are expected to attempt to recapture via new 
vehicle sales. As such, profits are included in the indirect cost 
calculation. Clearly, profits are not a ``cost'' of compliance--EPA 
is not imposing new regulations to force manufacturers to make a 
profit. However, profits are necessary for manufacturers in the 
heavy-duty industry, a competitive for-profit industry, to sustain 
their operations. As such, manufacturers are expected to make a 
profit on the compliant vehicles they sell, and we include those 
profits in estimating technology costs.
    \432\ Importantly, the final standards, useful lives, and 
warranty periods apply only to new, MY 2027 and later heavy-duty 
vehicles. The legacy fleet is not subject to the new requirements 
and, therefore, users of prior model year vehicles will not incur 
the operating costs we estimate.
---------------------------------------------------------------------------

    We requested comment on all aspects of the cost analysis. In 
particular, we requested comment on our estimation of warranty and 
research and development costs via use of scalars applied to indirect 
cost contributors (see Section V.A.2) and our estimates of emission 
repair cost impacts (see Section V.B.3). We also requested that 
comments include supporting data and/or alternative approaches that we 
could have considered when developing estimates for the final 
rulemaking.
    In response to our requests, we received many helpful comments, 
although lack of data in conjunction with some comments made it 
challenging to evaluate the changes suggested by the commenter. After 
careful consideration of the comments we received, we have made several 
changes to the final cost analysis relative to the proposal. Those 
changes are summarized in Table V-1. Note that, throughout this 
discussion of costs, we use the term regulatory class which defines 
vehicles with similar emission standards (see Chapter 5.2.2 of the 
RIA); we use the term regulatory class for consistency with our MOVES 
model and its classification system so that our costs align with our 
inventory estimates

[[Page 4404]]

and the associated benefits discussed in Sections VI, VII and VIII.

                          Table V-1--Major Changes to the Cost Analysis Since Proposal
----------------------------------------------------------------------------------------------------------------
             Area of change                      Proposed analysis                     Final analysis
----------------------------------------------------------------------------------------------------------------
Warranty costs.........................  Warranty contributions to         Warranty costs are calculated using a
                                          indirect costs were scaled        starting point of $1,000 (2018
                                          using the ratio of proposed       dollars, $976 in 2017 dollars) per
                                          provisions (miles/age) to the     year of warranty coverage for a
                                          baseline provisions.              vehicle equipped with a heavy HDE;
                                                                            warranty costs for other regulatory
                                                                            classes were scaled by the ratio of
                                                                            the direct manufacturing costs (DMC)
                                                                            for the regulatory class to the DMC
                                                                            of the heavy HDE regulatory class.
Warranty costs.........................  Baseline warranty costs were      Baseline warranty costs are estimated
                                          estimated for the regulated       assuming that a percentage of
                                          warranty period only (i.e., the   vehicles are purchased with extended
                                          analysis assumed that no          warranties.
                                          vehicles were purchased with
                                          extended warranties).
Emission repair costs..................  Repair costs used a cost per      Repair costs use a 2021 study by the
                                          mile curve derived from a Fleet   American Transportation Research
                                          Advantage Whitepaper with         Institute (ATRI) in place of the
                                          direct manufacturing cost (DMC)   Fleet Advantage Whitepaper.
                                          ratio scalars applied to
                                          determine cost per mile values
                                          for different regulatory
                                          classes.
Fuel prices............................  Used AEO2018 fuel prices in 2017  Uses AEO2019 fuel prices for
                                          dollars.                          consistency with the final rule
                                                                            version of the MOVES model while
                                                                            continuing with 2017 dollars.
Technology piece costs.................  Exhaust aftertreatment system     EAS costs have been updated and are
                                          (EAS) costs were based on an      based on FEV teardowns as described
                                          ICCT methodology with updates     in RIA Chapter 3.
                                          by EPA.
----------------------------------------------------------------------------------------------------------------

A. Technology Package Costs

    Commenters' primary comment with respect to our proposed technology 
package costs dealt with the need to replace the emission control 
system due to the combination of the low NOX standards with 
the long warranty and useful life provisions under proposed Option 1. 
Another comment with respect to our proposed technology package costs 
dealt with the estimated warranty costs, including both the methodology 
used and the magnitude of the cost estimated by EPA. As explained in 
Sections III and IV, the final program neither imposes numeric 
NOX standards as stringent as, nor does the final rule for 
heavy HDE contain warranty and useful life provisions as long as, 
proposed Option 1. We address these comments in more detail in section 
18 of the RTC. EPA considers the concerns raised in first of these 
comments to be obviated by the final emission standards and regulatory 
useful life values, in light of which we foresee no need for a routine 
replacement of the entire emission control system to maintain in-use 
compliance as suggested by some commenters. Regarding the second, as 
discussed in more detail in Section V.A.2 and section 18 of the RTC, 
EPA has updated the warranty cost methodology, including based on 
information submitted by commenters, and this has resulted in different 
costs associated with warranty.
    Individual technology piece costs are presented in Chapter 3 of the 
RIA. The direct manufacturing costs (DMC) presented in RIA Chapter 3 
use a different dollar basis than the cost analysis, and as such, the 
DMC values presented here have been adjusted to 2017 dollars. Following 
the first year of implementation, the costs also account for a learning 
effect to represent the cost reductions expected to occur via the 
``learning by doing'' phenomenon.\433\ This provides a year-over-year 
cost for each technology package--where a technology package consists 
of the entire emission-control system--as it is applied to new engine 
sales. We then apply industry standard ``retail price equivalent'' 
(RPE) markup factors, with adjustments discussed in the rest of this 
section, to estimate indirect costs associated with each technology 
package. Both the learning effects applied to direct costs and the 
application of markup factors to estimate indirect costs are consistent 
with the cost estimation approaches used in EPA's past transportation-
related regulatory programs. The sum of the direct and indirect costs 
represents our estimate of technology costs per vehicle on a year-over-
year basis. These technology costs multiplied by estimated sales then 
represent the total technology costs associated with the final program.
---------------------------------------------------------------------------

    \433\ The ``learning by doing'' phenomenon is the process by 
which the cost to manufacture a good decreases as more of that good 
is produced, as producers of the good learn from their experience.
---------------------------------------------------------------------------

    This cost calculation approach presumes that the expected 
technologies will be purchased by original equipment manufacturers 
(OEMs) from their suppliers. So, while the DMC estimates include the 
indirect costs and profits incurred by the supplier, the indirect cost 
markups we apply cover the indirect costs incurred by OEMs to 
incorporate the new technologies into their vehicles and to cover 
profit margins typical of the heavy-duty truck industry. We discuss the 
indirect costs in more detail in Section V.A.2.
1. Direct Manufacturing Costs
    To produce a unit of output, manufacturers incur direct and 
indirect costs. Direct costs include cost of materials and labor costs 
to manufacture that unit. Indirect costs are discussed in the following 
section. The direct manufacturing costs presented here include 
individual technology costs for emission-related engine components and 
exhaust aftertreatment systems (EAS).
    Notably, for this analysis we include not only the marginal 
increased costs associated with the standards, but also the emission 
control system costs for the baseline, or no action, case.\434\ 
Throughout this discussion, we refer to baseline case costs, or 
baseline costs, which reflect our cost estimate of emission-related 
engine systems and the exhaust aftertreatment system absent impacts of 
this final rule. This inclusion of baseline system costs contrasts with 
EPA's approach in recent greenhouse gas rules or the light-duty Tier 3 
criteria pollutant rule where we estimated costs relative to a baseline 
case, which obviated the need to estimate baseline costs. We have 
included baseline costs in this analysis because the new emissions 
warranty and regulatory useful life provisions are expected to have 
some impact on not only the new technology added to comply with the 
final standards, but also on emission control technologies already 
developed and in use. The new warranty and useful life provisions will 
increase costs not only for the new technology added in response to the 
new standards, but also for the technology already in place

[[Page 4405]]

(to which the new technology is added) because the new warranty and 
useful life provisions will apply to the entire emission-control 
system, not just the new technology added in response to the new 
standards. The baseline direct manufacturing costs detailed in this 
section are intended to reflect that portion of baseline case engine 
hardware and aftertreatment systems for which new indirect costs will 
be incurred due to the new warranty and useful life provisions, even 
apart from changes in the level of emission standards.
---------------------------------------------------------------------------

    \434\ For this cost analysis, the baseline, or no action, case 
consists of MY 2019 engines and emission control systems. See also 
Section VI for more information about the emission inventory 
baseline and how that baseline is characterized.
---------------------------------------------------------------------------

    As done in the NPRM, we have estimated the baseline engine costs 
based on studies done by the International Council on Clean 
Transportation (ICCT), as discussed in more detail in Chapter 7 of the 
RIA. As discussed there, the baseline engine costs consist of 
turbocharging, fuel system, exhaust gas recirculation, etc. These costs 
represent those for technologies that will be subject to new, longer 
warranty and useful life provisions under this final rule. For costs 
associated with the action case, we have used FEV-conducted teardown-
based costs as presented in Chapter 3 of the RIA for newly added 
cylinder deactivation systems,\435\ and for the exhaust aftertreatment 
system (EAS) costs.\436\ The direct manufacturing costs for the 
baseline engine+aftertreatment and for the final program are shown for 
diesel engines in Table V-2, gasoline engines in Table V-3 and CNG 
engines in Table V-4. Costs are shown for regulatory classes included 
in the cost analysis and follow the categorization approach used in our 
MOVES model. Please refer to Chapter 6 of the RIA for a description of 
the regulatory classes and why the tables that follow include or do not 
include each regulatory class. In short, where MOVES has regulatory 
class populations and associated emission inventories, our cost 
analysis estimates costs. Note also that, throughout this section, we 
use several acronyms, including heavy-duty engine (HDE), exhaust gas 
recirculation (EGR), exhaust aftertreatment system (EAS), and 
compressed natural gas (CNG).
---------------------------------------------------------------------------

    \435\ Mamidanna, S. 2021. Heavy-Duty Engine Valvetrain 
Technology Cost Assessment. U.S. EPA Contract with FEV North 
America, Inc., Contract No. 68HERC19D0008, Task Order No. 
68HERH20F0041.Submitted to the Docket with the proposal.
    \436\ Mamidanna, S. 2021. Heavy-Duty Vehicles Aftertreatment 
Systems Cost Assessment. Submitted to the Docket with the proposal.

   Table V-2--Diesel Technology and Package Direct Manufacturing Costs per Engine by Regulatory Class for the
                                Baseline and Final Program, MY2027, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                                                                Final program
            MOVES regulatory class                        Technology              Baseline    (MY2027 increment
                                                                                                 to baseline)
----------------------------------------------------------------------------------------------------------------
Light HDE....................................  Package........................        3,699                1,957
                                               Engine hardware................        1,097                    0
                                               Closed crankcase...............           18                   37
                                               Cylinder deactivation..........            0                  196
                                               EAS............................        2,585                1,724
Medium HDE...................................  Package........................        3,808                1,817
                                               Engine hardware................        1,254                    0
                                               Closed crankcase...............           18                   37
                                               Cylinder deactivation..........            0                  147
                                               EAS............................        2,536                1,634
Heavy HDE....................................  Package........................        5,816                2,316
                                               Engine hardware................        2,037                    0
                                               Closed crankcase...............           18                   37
                                               Cylinder deactivation..........            0                  206
                                               EAS............................        3,761                2,074
Urban bus....................................  Package........................        3,884                1,850
                                               Engine hardware................        1,254                    0
                                               Closed crankcase...............           18                   37
                                               Cylinder deactivation..........            0                  147
                                               EAS............................        2,613                1,666
----------------------------------------------------------------------------------------------------------------

  Table V-3--Gasoline Technology and Package Direct Manufacturing Costs per Engine by Regulatory Class for the
                                Baseline and Final Program, MY2027, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                                                                Final program
            MOVES regulatory class                        Technology              Baseline    (MY2027 increment
                                                                                                 to baseline)
----------------------------------------------------------------------------------------------------------------
Light HDE....................................  Package........................        2,681                  688
                                               Engine hardware................          522                    0
                                               Aftertreatment.................        2,158                  664
                                               ORVR...........................            0                   24
Medium HDE...................................  Package........................        2,681                  688
                                               Engine hardware................          522                    0
                                               Aftertreatment.................        2,158                  664
                                               ORVR...........................            0                   24
Heavy HDE....................................  Package........................        2,681                  688
                                               Engine hardware................          522                    0
                                               Aftertreatment.................        2,158                  664
                                               ORVR...........................            0                   24
----------------------------------------------------------------------------------------------------------------

[[Page 4406]]

    Table V-4--CNG Technology and Package Direct Manufacturing Costs per Engine by Regulatory Class, for the
                                Baseline and Final Program, MY2027, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                                                               Final standards
            MOVES regulatory class                        Technology              Baseline    (MY2027 increment
                                                                                                 to baseline)
----------------------------------------------------------------------------------------------------------------
Heavy HDE....................................  Package........................        8,585                   25
                                               Engine hardware................          896                    0
                                               Aftertreatment.................        7,689                   25
Urban bus....................................  Package........................        6,438                   19
                                               Engine hardware................          672                    0
                                               Aftertreatment.................        5,766                   19
----------------------------------------------------------------------------------------------------------------

    The direct costs are then adjusted to account for learning effects 
going forward from the first year of implementation. We describe in 
detail in Chapter 7 of the RIA the approach used to apply learning 
effects in this analysis. Learning effects were applied on a technology 
package cost basis, and MOVES-projected sales volumes were used to 
determine first-year sales and cumulative sales. The resultant direct 
manufacturing costs and how those costs decrease over time are 
presented in Section V.A.3.
2. Indirect Costs
    The indirect costs presented here are all the costs estimated to be 
incurred by manufacturers of new heavy-duty engines and vehicles 
associated with producing the unit of output that are not direct costs. 
For example, they may be related to production (such as research and 
development (R&D)), corporate operations (such as salaries, pensions, 
and health care costs for corporate staff), or selling (such as 
transportation, dealer support, and marketing). Indirect costs are 
generally recovered by allocating a share of the indirect costs to each 
unit of good sold. Although direct costs can be allocated to each unit 
of good sold, it is more challenging to account for indirect costs 
allocated to a unit of goods sold. To ensure that regulatory analyses 
capture the changes in indirect costs, markup factors (which relate 
total indirect costs to total direct costs) have been developed and 
used by EPA and other stakeholders. These factors are often referred to 
as retail price equivalent (RPE) multipliers. RPE multipliers provide, 
at an aggregate level, the relative shares of revenues, where:

Revenue = Direct Costs + Indirect Costs
Revenue/Direct Costs = 1 + Indirect Costs/Direct Costs = Retail Price 
Equivalent (RPE)

    Resulting in:

Indirect Costs = Direct Costs x (RPE-1)

    If the relationship between revenues and direct costs (i.e., RPE) 
can be shown to equal an average value over time, then an estimate of 
direct costs can be multiplied by that average value to estimate 
revenues, or total costs. Further, that difference between estimated 
revenues, or total costs, and estimated direct costs can be taken as 
the indirect costs. EPA has frequently used these multipliers \437\ to 
predict the resultant impact on costs associated with manufacturers' 
responses to regulatory requirements and we are using that approach in 
this analysis to account for most of the indirect cost contributions. 
The exception is the warranty cost as described in this section.
---------------------------------------------------------------------------

    \437\ See 75 FR 25324, 76 FR 57106, 77 FR 62624, 79 FR 23414, 81 
FR 73478, 86 FR 74434.
---------------------------------------------------------------------------

    The cost analysis estimates indirect costs by applying the RPE 
markup factor used in past rulemakings (such as those setting 
greenhouse gas standards for heavy-duty trucks).\438\ The markup 
factors are based on financial filings with the Securities and Exchange 
Commission for several engine and engine/truck manufacturers in the 
heavy-duty industry.\439\ The RPE factors for the HD truck industry are 
shown in Table V-5. Also shown in Table V-5 are the RPE factors for 
light-duty vehicle manufacturers.\440\
---------------------------------------------------------------------------

    \438\ 76 FR 57106; 81 FR 73478.
    \439\ Heavy Duty Truck Retail Price Equivalent and Indirect Cost 
Multipliers, Draft Report, July 2010.
    \440\ Rogozhin, A., et al., Using indirect cost multipliers to 
estimate the total cost of adding new technology in the automobile 
industry. International Journal of Production Economics (2009), 
doi:10.1016/j.ijpe.2009.11.031.

 Table V-5--Retail Price Equivalent Factors in the Heavy-Duty and Light-
                             Duty Industries
------------------------------------------------------------------------
                                             HD truck       LD vehicle
            Cost contributor                 industry        industry
------------------------------------------------------------------------
Direct manufacturing cost...............            1.00            1.00
Warranty................................            0.03            0.03
R&D.....................................            0.05            0.05
Other (admin, retirement, health, etc.).            0.29            0.36
Profit (cost of capital)................            0.05            0.06
RPE.....................................            1.42            1.50
------------------------------------------------------------------------

    For this analysis, EPA based indirect cost estimates for diesel and 
CNG regulatory classes on the HD Truck Industry RPE values shown in 
Table V-5.\441\ For gasoline regulatory classes, we used the LD Vehicle 
Industry values shown in Table V-5 since they more closely represent 
the cost structure of manufacturers in that industry--Ford, General 
Motors, and Stellantis.
---------------------------------------------------------------------------

    \441\ Note that the report used the term ``HD Truck'' while EPA 
generally uses the term ``HD vehicle;'' they are equivalent when 
referring to this report.
---------------------------------------------------------------------------

    Of the cost contributors listed in Table V-5, Warranty and R&D are 
the elements of indirect costs that the final rule requirements are 
expected to impact. As discussed in Section IV of this preamble, EPA is 
lengthening the required warranty period, which we expect to increase 
the contribution of warranty costs to indirect costs. EPA is also 
tightening the numeric standards and extending the regulatory useful 
life,

[[Page 4407]]

which we expect to result in increased R&D expenses as compliant 
systems are developed. All other indirect cost elements--those 
encapsulated by the ``Other'' category, including General and 
Administrative Costs, Retirement Costs, Healthcare Costs, and other 
overhead costs--as well as Profits, are expected to scale according to 
their historical levels of contribution.
    As mentioned, Warranty and R&D are the elements of indirect costs 
that are expected to be impacted. Warranty expenses are the costs that 
a business expects to or has already incurred for the repair or 
replacement of goods that it has sold. The total amount of warranty 
expense is limited by the warranty period that a business typically 
allows. After the warranty period for a product has expired, a business 
no longer incurs a warranty liability; thus, a longer warranty period 
results in a longer period of liability for a product. At the time of 
sale, a warranty liability account is adjusted to reflect the expected 
costs of any potential future warranty claims. If and when warranty 
claims are made by customers, the warranty liability account is debited 
and a warranty claims account is credited to cover warranty claim 
expenses.\442\
---------------------------------------------------------------------------

    \442\ Warranty expense is recognized in the same period as the 
sales for the products that were sold, if it is probable that an 
expense will be incurred and the company can estimate the amount of 
the expense. For more discussion of this topic, see the supporting 
material in this docket, AccountingTools.com, December 24, 2020, 
accessed January 28, 2021.
---------------------------------------------------------------------------

    In the proposed analysis, to address the expected increased 
indirect cost contributions associated with warranty (increased funding 
of the warranty liability account) due to the proposed longer warranty 
requirements, we applied scaling factors commensurate with the changes 
in proposed Option 1 or Option 2 to the number of miles included in the 
warranty period (i.e., VMT-based scaling factors). Industry commenters 
took exception to this approach, arguing that it resulted in 
underestimated costs associated with warranty. To support their 
comments, one commenter submitted data that showed costs associated 
with actual warranty claims for roughly 250,000 heavy heavy-duty 
vehicles. The following figure includes the chart from their comments, 
which are also in the public docket for this rule.
[GRAPHIC] [TIFF OMITTED] TR24JA23.002

Figure V-1 Warranty Costs Submitted as Part of the Comments From An 
Industry Association; See EPA-HQ-OAR-2019-0055-1203-A1, Page 151

    EPA considers this comment and supporting information to be 
persuasive, not only because it represents data, but also because it 
represents data from three manufacturers and over 250,000 vehicles; 
thus, we switched from a VMT-based scaling approach to a years-based 
approach to better take into account this information. However, the 
data are for heavy HDE, so it is not possible to determine an 
appropriate cost per year for light or medium HDE from the data 
directly. Also, the data represent actual warranty claims without any 
mention of the warranty claims rate (i.e., the share of engines sold 
that are making the warranty claims represented in the data). This 
latter issue makes it difficult to determine the costs that might be 
imposed on all new engines sold to cover the future warranty claims for 
the relatively smaller fraction of engines that incur warranty repair. 
In other words, if all heavy HDE purchases are helping to fund a 
warranty liability account, it is unclear if the $1,000 per year per 
engine is the right amount or if $1,000 per year is needed on only that 
percent of engines that will incur warranty repair. In the end, 
warranty costs imposed on new engine sales should be largely recouped 
by purchasers of those engines in the form of reduced emission repair 
expenses. EPA believes it is unlikely that a manufacturer would use 
their warranty program as a profit generator under the $1,000 per 
engine approach, especially in a market as competitive as the HD engine 
and vehicle industry. The possibility exists that the costs associated 
with the longer warranty

[[Page 4408]]

coverage required by this rule will (1) converge towards those of the 
better performing OEMs; and (2) drop over time via something analogous 
to the learning by doing phenomenon described earlier. If true, we have 
probably overestimated the costs estimated here as attributable to this 
rule.
    Thus, after careful consideration of these comments regarding 
warranty, and the engineering judgement of EPA subject matter experts, 
we revised our approach to estimating warranty costs, and for the final 
rule we have estimated warranty costs assuming a cost of $1,000 (2018 
dollars or $977 in 2017 dollars) per estimated number of years of 
warranty coverage for a heavy heavy-duty diesel engine or heavy-duty 
vehicle equipped with such an engine. For other regulatory (engine) 
classes, we have scaled that value by the ratio of their estimated 
baseline emission-control system direct cost to the estimated emission-
control system direct cost of the baseline heavy heavy-duty diesel 
engine. We use the baseline heavy heavy-duty diesel engine direct cost 
here because it should be consistent with the data behind the $1,000 
per year value. The resulting emission-related warranty costs per year 
for a MY 2027 HD engine are as shown in Table V-6.

                                       Table V-6--Warranty Costs per Year
                                               [2017 Dollars] \a\
----------------------------------------------------------------------------------------------------------------
         MOVES regulatory class                   Scaling approach            Diesel      Gasoline       CNG
----------------------------------------------------------------------------------------------------------------
Light HDE...............................  Base Light HDE DMC/Base Diesel           621          450  ...........
                                           Heavy HDE DMC.
Medium HDE..............................  Base Medium HDE DMC/Base Diesel          639          449  ...........
                                           Heavy HDE DMC.
Heavy HDE...............................  Base Heavy HDE DMC/Base Diesel           977          448        1,442
                                           Heavy HDE DMC.
Urban bus...............................  Base Urban bus DMC/Base Diesel           652  ...........        1,081
                                           Heavy HDE DMC.
----------------------------------------------------------------------------------------------------------------
\a\ The Base Diesel HDE DMC would be the $5,816 value shown in Table V-2.

    As noted, we have used the estimated number of years of warranty 
coverage, not the regulated number of years. In other words, a long-
haul tractor accumulating over 100,000 miles per year will reach any 
regulated warranty mileage prior to a refuse truck accumulating under 
40,000 miles per year, assuming both are in the same regulatory class 
and, therefore, have the same warranty provisions. In all cases, we 
estimate the number of years of warranty coverage by determining the 
minimum number of years to reach either the number of years, the number 
of miles, or the number of hours of operation covered by the EPA 
emissions-related warranty. We provide more detail on this in Chapter 7 
of the final RIA.
    Lastly, with respect to warranty, we have estimated that many of 
the regulated products are sold today with a warranty period longer 
than the EPA required emissions-related warranty period. In the 
proposal, we calculated baseline warranty costs only for the required 
warranty periods. In the final analysis, we calculate baseline warranty 
costs based on the warranty periods for which engines are actually 
sold. For diesel and CNG heavy HDE, we assume all are sold with 
warranties covering 250,000 miles, and for diesel and CNG medium HDE, 
we assume half are sold with warranties covering 150,000 miles. For all 
other engines and associated fuel types, we have not estimated any use 
of extended warranties in the baseline.
    We use these annual warranty costs for both the baseline and the 
final standards despite the addition of new technology associated with 
this final rule. We believe this is reasonable for two reasons: (1) The 
source data included several years of data during which there must have 
been new technology introductions, yet annual costs appear to have 
remained generally steady; and, (2) the R&D we expect to be done, 
discussed next, is expected to improve overall durability, which should 
serve to help maintain historical annual costs.
    For R&D, we have maintained the approach used in the proposal, 
although it is applied using the final useful life provisions. For 
example, for R&D on a Class 8 truck, the final standards would extend 
regulatory useful life from 10 years, 22,000 hours, or 435,000 miles, 
to 11 years, 32,000 hours, or 650,000 miles. We have applied a scaling 
factor of 1.49 (650/435) to the 0.05 R&D contribution factor for MYs 
2027 and later. We apply this same methodology to estimating R&D for 
other vehicle categories. We estimate that once the development efforts 
into longer useful life are complete, increased expenditures will 
return to their normal levels of contribution. Therefore, we have 
implemented R&D scalars for three years (2027 through 2029). In MY 2030 
and later, the R&D scaling factors are no longer applied.
    The VMT-based scaling factors applied to R&D cost contributors used 
in our cost analysis of final standards are shown in Table V-7 for 
diesel and CNG regulatory classes and in Table V-8 for gasoline 
regulatory classes.

Table V-7--Scaling Factors Applied to RPE Contribution Factors To Reflect Changes in Their Contributions, Diesel
                                            & CNG Regulatory Classes
----------------------------------------------------------------------------------------------------------------
                                                                                             R&D scalars
                    Scenario                           MOVES regulatory class       ----------------------------
                                                                                       MY2027-2029     MY2030+
----------------------------------------------------------------------------------------------------------------
Baseline.......................................  Light HDE.........................            1.00         1.00
                                                 Medium HDE........................            1.00         1.00
                                                 Heavy HDE.........................            1.00         1.00
                                                 Urban Bus.........................            1.00         1.00
Final Program..................................  Light HDE.........................            2.45         1.00
                                                 Medium HDE........................            1.89         1.00
                                                 Heavy HDE.........................            1.49         1.00
                                                 Urban Bus.........................            1.49         1.00
----------------------------------------------------------------------------------------------------------------

[[Page 4409]]

    Table V-8--Scaling Factors Applied to RPE Contribution Factors To Reflect Changes in Their Contributions,
                                           Gasoline Regulatory Classes
----------------------------------------------------------------------------------------------------------------
                                                                                             R&D scalars
                    Scenario                           MOVES regulatory class       ----------------------------
                                                                                       MY2027-2029     MY2030+
----------------------------------------------------------------------------------------------------------------
Baseline.......................................  Light HDE.........................            1.00         1.00
                                                 Medium HDE........................            1.00         1.00
                                                 Heavy HDE.........................            1.00         1.00
Final Program..................................  Light HDE.........................            1.82         1.00
                                                 Medium HDE........................            1.82         1.00
                                                 Heavy HDE.........................            1.82         1.00
----------------------------------------------------------------------------------------------------------------

    Lastly, as mentioned in Section V.A.1, the markups for estimating 
indirect costs are applied to our estimates of the absolute direct 
manufacturing costs for emission-control technology shown in Table V-2, 
Table V-3 and Table V-4, not just the incremental costs associated with 
the final program (i.e., the Baseline + Final costs). Table V-9 
provides an illustrative example using a baseline technology cost of 
$5000, a final incremental cost of $1000, and an indirect cost R&D 
contribution of 0.05 with a simple scalar of 1.5 associated with a 
longer useful life period. In this case, the costs could be calculated 
according to two approaches, as shown in Table V-9. By including the 
baseline costs, we are estimating new R&D costs in the final standards, 
as illustrated by the example where including baseline costs results in 
R&D costs of $450 while excluding baseline costs results in R&D costs 
of $75.

    Table V-9--Simplified Hypothetical Example of Indirect R&D Costs
    Calculated on An Incremental vs. Absolute Technology Package Cost
    [Values are not from the analysis and are for presentation only]
------------------------------------------------------------------------
                                Using incremental
                                   costs only       Using absolute costs
------------------------------------------------------------------------
Baseline direct               $5,000..............  $5,000.
 manufacturing cost (DMC).
Direct Manufacturing Cost     $1,000..............  $5,000 + $1,000 =
 (DMC).                                              $6,000.
Indirect R&D Costs..........  $1,000 x 0.05 x 1.5   $6,000 x 0.05 x 1.5
                               = $75.                = $450.
Incremental DMC + R&D.......  $1,000 + $75 =        $6,000 + $450-$5,000
                               $1,075.               = $1,450.
------------------------------------------------------------------------

3. Technology Costs per Vehicle
    The following tables present the technology costs estimated for the 
final program on a per-vehicle basis for MY 2027. Reflected in these 
tables are learning effects on direct manufacturing costs and scaling 
effects associated with final program requirements. The sum is also 
shown and reflects the direct plus indirect cost per vehicle in the 
specific model year. Note that the indirect costs shown include 
warranty, R&D, ``other,'' and profit, the latter two which scale with 
direct costs via the indirect cost contribution factor. While direct 
costs do not change across the different vehicle types (i.e., long-haul 
versus short-haul combination), the indirect costs do vary because 
differing miles driven and operating hours between types of vehicles 
result in different warranty and useful life estimates in actual use. 
These differences impact the estimated warranty and R&D costs.
    We show costs per vehicle here, but it is important to note that 
these are costs and not prices. We are not estimating how manufacturers 
might price their products. Manufacturers may pass costs along to 
purchasers via price increases in a manner consistent with what we show 
here. However, manufacturers may also price certain products higher 
than what we show while pricing others lower--the higher-priced 
products thereby subsidizing the lower-priced products. This is true in 
any market, not just the heavy-duty highway industry. This may be 
especially true with respect to the indirect costs we have estimated 
because, for example, R&D done to improve emission durability can 
readily transfer across different engines whereas hardware added to an 
engine is uniquely tied to that engine.
    Importantly, we present costs here for MY2027 vehicles, but these 
costs continue for every model year going forward from there. 
Consistent with the learning impacts described in section V.A.2, the 
costs per vehicle decrease slightly over time, but only the increased 
R&D costs are expected to decrease significantly. Increased R&D is 
estimated to occur for three years following and including MY2027 
(i.e., MY2027-29), after which time its contribution to indirect costs 
returns to lower values as shown in Table V.4.

Table V-10--MY2027 Diesel Light HDE Technology Costs per Vehicle Associated With the Final Program, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                            Direct costs    Indirect costs    Costs per vehicle
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           3,699             2,332                6,031
Other Buses..............................................           3,699             2,263                5,962
School Buses.............................................           3,699             3,829                7,528
Short-Haul Single Unit Trucks............................           3,699             2,851                6,550
Transit Buses............................................           3,699             2,263                5,962
----------------------------------------------------------------------------------------------------------------

[[Page 4410]]

 
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           5,656             6,353               12,009
Other Buses..............................................           5,656             6,064               11,720
School Buses.............................................           5,656             8,830               14,485
Short-Haul Single Unit Trucks............................           5,656             8,530               14,186
Transit Buses............................................           5,656             6,064               11,720
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           1,957             4,021                5,978
Other Buses..............................................           1,957             3,800                5,757
School Buses.............................................           1,957             5,001                6,957
Short-Haul Single Unit Trucks............................           1,957             5,680                7,636
Transit Buses............................................           1,957             3,800                5,757
----------------------------------------------------------------------------------------------------------------

    Table V-11--MY2027 Diesel Medium HDE Technology Costs per Vehicle Associated With the Final Program, 2017
                                                     Dollars
----------------------------------------------------------------------------------------------------------------
                                                            Direct costs    Indirect costs    Costs per vehicle
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           3,808             3,774                7,582
Motor Homes..............................................           3,808             4,682                8,490
Other Buses..............................................           3,808             3,597                7,404
Refuse Trucks............................................           3,808             4,217                8,025
School Buses.............................................           3,808             4,682                8,490
Short-Haul Combination Trucks............................           3,808             2,595                6,402
Short-Haul Single Unit Trucks............................           3,808             4,682                8,490
Transit Buses............................................           3,808             3,597                7,404
----------------------------------------------------------------------------------------------------------------
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           5,625             7,572               13,197
Motor Homes..............................................           5,625             8,839               14,464
Other Buses..............................................           5,625             7,175               12,799
Refuse Trucks............................................           5,625             8,564               14,189
School Buses.............................................           5,625             8,839               14,464
Short-Haul Combination Trucks............................           5,625             4,930               10,555
Short-Haul Single Unit Trucks............................           5,625             8,839               14,464
Transit Buses............................................           5,625             7,175               12,799
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           1,817             3,798                5,615
Motor Homes..............................................           1,817             4,157                5,974
Other Buses..............................................           1,817             3,578                5,395
Refuse Trucks............................................           1,817             4,347                6,164
School Buses.............................................           1,817             4,157                5,974
Short-Haul Combination Trucks............................           1,817             2,335                4,153
Short-Haul Single Unit Trucks............................           1,817             4,157                5,974
Transit Buses............................................           1,817             3,578                5,395
----------------------------------------------------------------------------------------------------------------

Table V-12--MY2027 Diesel Heavy HDE Technology Costs per Vehicle Associated With the Final Program, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                            Direct costs    Indirect costs    Costs per vehicle
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks.............................           5,816             4,025                9,841
Long-Haul Single Unit Trucks.............................           5,816             7,151               12,967
Motor Homes..............................................           5,816             7,151               12,967
Other Buses..............................................           5,816             7,151               12,967
Refuse Trucks............................................           5,816             7,151               12,967
School Buses.............................................           5,816             7,151               12,967
Short-Haul Combination Trucks............................           5,816             5,658               11,473

[[Page 4411]]

 
Short-Haul Single Unit Trucks............................           5,816             7,151               12,967
----------------------------------------------------------------------------------------------------------------
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks.............................           8,132             6,535               14,667
Long-Haul Single Unit Trucks.............................           8,132            13,139               21,271
Motor Homes..............................................           8,132            13,139               21,271
Other Buses..............................................           8,132            13,139               21,271
Refuse Trucks............................................           8,132            13,139               21,271
School Buses.............................................           8,132            13,139               21,271
Short-Haul Combination Trucks............................           8,132             9,474               17,606
Short-Haul Single Unit Trucks............................           8,132            13,139               21,271
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks.............................           2,316             2,510                4,827
Long-Haul Single Unit Trucks.............................           2,316             5,988                8,304
Motor Homes..............................................           2,316             5,988                8,304
Other Buses..............................................           2,316             5,988                8,304
Refuse Trucks............................................           2,316             5,988                8,304
School Buses.............................................           2,316             5,988                8,304
Short-Haul Combination Trucks............................           2,316             3,816                6,132
Short-Haul Single Unit Trucks............................           2,316             5,988                8,304
----------------------------------------------------------------------------------------------------------------

Table V-13--MY2027 Diesel Urban Bus Technology Costs per Vehicle Associated With the Final Program, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                            Direct costs    Indirect costs    Costs per vehicle
----------------------------------------------------------------------------------------------------------------
FRM Baseline.............................................           3,884             3,238                7,122
FRM Baseline + Final Program.............................           5,734             8,901               14,635
Increased Cost of the Final Program......................           1,850             5,663                7,512
----------------------------------------------------------------------------------------------------------------

  Table V-14--MY2027 Gasoline HDE Technology Costs per Vehicle Associated With the Final Program, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                            Direct costs    Indirect costs    Costs per vehicle
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           2,681             1,905                4,585
Motor Homes..............................................           2,681             3,511                6,192
Other Buses..............................................           2,681             1,855                4,535
School Buses.............................................           2,681             2,989                5,670
Short-Haul Single Unit Trucks............................           2,681             2,280                4,961
Transit Buses............................................           2,681             1,855                4,535
----------------------------------------------------------------------------------------------------------------
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           3,369             3,784                7,153
Motor Homes..............................................           3,369             6,223                9,592
Other Buses..............................................           3,369             3,624                6,993
School Buses.............................................           3,369             6,223                9,592
Short-Haul Single Unit Trucks............................           3,369             4,986                8,355
Transit Buses............................................           3,369             3,624                6,993
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................             688             1,880                2,568
Motor Homes..............................................             688             2,712                3,401
Other Buses..............................................             688             1,770                2,458
School Buses.............................................             688             3,234                3,923
Short-Haul Single Unit Trucks............................             688             2,706                3,394
Transit Buses............................................             688             1,770                2,458
----------------------------------------------------------------------------------------------------------------

[[Page 4412]]

  Table V-15--MY2027 CNG Heavy HDE Technology Costs per Vehicle Associated With the Final Program, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                            Direct costs    Indirect costs    Costs per vehicle
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           8,585            10,556               19,141
Other Buses..............................................           8,585            10,556               19,141
Refuse Trucks............................................           8,585            10,556               19,141
School Buses.............................................           8,585            10,556               19,141
Short-Haul Combination Trucks............................           8,585             8,351               16,936
Short-Haul Single Unit Trucks............................           8,585            10,556               19,141
----------------------------------------------------------------------------------------------------------------
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................           8,610            17,988               26,598
Other Buses..............................................           8,610            17,988               26,598
Refuse Trucks............................................           8,610            17,988               26,598
School Buses.............................................           8,610            17,988               26,598
Short-Haul Combination Trucks............................           8,610            12,577               21,187
Short-Haul Single Unit Trucks............................           8,610            17,988               26,598
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks.............................              25             7,431                7,457
Other Buses..............................................              25             7,431                7,457
Refuse Trucks............................................              25             7,431                7,457
School Buses.............................................              25             7,431                7,457
Short-Haul Combination Trucks............................              25             4,225                4,251
Short-Haul Single Unit Trucks............................              25             7,431                7,457
----------------------------------------------------------------------------------------------------------------

  Table V-16--MY2027 CNG Urban Bus Technology Costs per Vehicle Associated With the Final Program, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                            Direct costs    Indirect costs    Costs per vehicle
----------------------------------------------------------------------------------------------------------------
FRM Baseline.............................................           6,438             5,367               11,806
FRM Baseline + Final Program.............................           6,457            13,490               19,948
Increased Cost of the Final Program......................              19             8,123                8,142
----------------------------------------------------------------------------------------------------------------

B. Operating Costs

    We have estimated three impacts on operating costs expected to be 
incurred by users of new MY 2027 and later heavy-duty vehicles: 
Increased diesel exhaust fluid (DEF) consumption by diesel vehicles due 
to increased DEF dose rates to enable compliance with more stringent 
NOX standards; decreased fuel costs for gasoline vehicles 
due to new onboard refueling vapor recovery systems that allow burning 
(in engine) of otherwise evaporated hydrocarbon emissions; emission 
repair impacts brought about by longer warranty and useful life 
provisions; and the potential higher emission-related repair costs for 
vehicles equipped with the new technology. For the repair impacts, we 
expect that the longer duration warranty period will result in lower 
owner/operator-incurred repair costs due to fewer repairs being paid 
for by owners/operators since more costs will be borne by the 
manufacturer, and that the longer duration useful life periods will 
result in increased emission control system durability. We have 
estimated the net effect on repair costs and describe our approach, 
along with increased DEF consumption and reduced gasoline consumption, 
in this section. Additional details on our methodology and estimates of 
operating costs are included in RIA Chapter 7.2.
1. Costs Associated With Increased Diesel Exhaust Fluid (DEF) 
Consumption in Diesel Engines
    Consistent with the approach used to estimate technology costs, we 
have estimated both baseline case DEF consumption and DEF consumption 
under the final program. For the baseline case, we estimated DEF 
consumption using the relationship between DEF dose rate and the 
reduction in NOX over the SCR catalyst. The relationship 
between DEF dose rate and NOX reduction across the SCR 
catalyst is based on methodology presented in the Technical Support 
Document to the 2012 Nonconformance Penalty rule (the NCP Technical 
Support Document, or NCP TSD).\443\ The relationship of DEF dose rate 
to NOX reduction used in that methodology considered FTP 
emissions and, as such, the DEF dose rate increased as FTP tailpipe 
emissions decreased. The DEF dose rate used in this analysis is 5.18 
percent of fuel consumed.
---------------------------------------------------------------------------

    \443\ Nonconformance Penalties for On-highway Heavy-duty Diesel 
Engines: Technical Support Document; EPA-420-R-12-014, August 2012.
---------------------------------------------------------------------------

    To estimate DEF consumption impacts under the final program, which 
involves not only the new FTP emission standards but also the new SET 
and LLC standards along with new off-cycle standards, we developed a 
new approach to estimate DEF consumption for the proposal, which we 
also applied in this final rule. For this analysis, we scaled DEF 
consumption with the NOX reductions achieved under the final 
emission standards. This was done by considering the molar mass of 
NOX, the molar mass of urea, the mass concentration of urea 
in DEF, along with the density of DEF, to estimate the

[[Page 4413]]

theoretical gallons of DEF consumed per ton of NOX reduced. 
We estimated theoretical DEF consumption per ton of NOX 
reduced at 442 gallons/ton, which we then adjusted based on testing to 
527 gallons/ton, the value used in this analysis. We describe this in 
more detail in Section 7.2.1 of the RIA.
    These two DEF consumption metrics--dose rate per gallon for an 
engine meeting the baseline emission standards and any additional DEF 
consumption per ton of NOX reduced to achieve the final 
emission standards over the final useful lives--were used to estimate 
total DEF consumption. These DEF consumption rates were then multiplied 
by DEF price per gallon, adjusted to 2017 dollars from the DEF prices 
presented in the NCP TSD, to arrive at the impacts on DEF costs for 
diesel engines. These are shown for MY2027 diesel vehicles in Table V-
17. Because these are operating costs which occur over time, we present 
them at both 3 and 7 percent discount rates.

                       Table V-17--MY2027 Lifetime DEF Costs per Diesel Vehicle Associated With Final NOX Standards, 2017 Dollars
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         3% Discount rate                                7% Discount rate
                                                         -----------------------------------------------------------------------------------------------
                                                           Light HDE  Medium HDE   Heavy HDE   Urban bus   Light HDE  Medium HDE   Heavy HDE   Urban bus
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      FRM Baseline
--------------------------------------------------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks............................  ..........  ..........      34,009  ..........  ..........  ..........      25,768  ..........
Long-Haul Single Unit Trucks............................       3,759       5,686       6,823  ..........       2,937       4,443       5,331  ..........
Motor Homes.............................................  ..........       1,489       1,764  ..........  ..........       1,068       1,265  ..........
Other Buses.............................................       9,118      11,285      11,688  ..........       6,695       8,286       8,582  ..........
Refuse Trucks...........................................  ..........       8,435       8,787  ..........  ..........       6,317       6,581  ..........
School Buses............................................       2,331       3,030       3,187  ..........       1,712       2,225       2,340  ..........
Short-Haul Combination Trucks...........................  ..........      16,323      17,154  ..........  ..........      12,735      13,384  ..........
Short-Haul Single Unit Trucks...........................       2,733       4,144       4,975  ..........       2,100       3,184       3,823  ..........
Transit Buses...........................................       9,192      11,254  ..........      11,742       6,750       8,263  ..........       8,622
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              FRM Baseline + Final Program
--------------------------------------------------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks............................  ..........  ..........      37,621  ..........  ..........  ..........      28,580  ..........
Long-Haul Single Unit Trucks............................       4,011       6,215       7,916  ..........       3,136       4,865       6,200  ..........
Motor Homes.............................................  ..........       1,617       2,016  ..........  ..........       1,162       1,450  ..........
Other Buses.............................................       9,805      12,277      13,594  ..........       7,209       9,040      10,011  ..........
Refuse Trucks...........................................  ..........       9,182      10,246  ..........  ..........       6,895       7,696  ..........
School Buses............................................       2,501       3,293       3,671  ..........       1,839       2,424       2,702  ..........
Short-Haul Combination Trucks...........................  ..........      17,575      19,378  ..........  ..........      13,727      15,154  ..........
Short-Haul Single Unit Trucks...........................       2,949       4,573       5,864  ..........       2,268       3,522       4,517  ..........
Transit Buses...........................................       9,867      12,149  ..........      13,410       7,253       8,945  ..........       9,863
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Increased Cost of the Final Program
--------------------------------------------------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks............................  ..........  ..........       3,612  ..........  ..........  ..........       2,812  ..........
Long-Haul Single Unit Trucks............................         252         529       1,094  ..........         199         422         869  ..........
Motor Homes.............................................  ..........         128         253  ..........  ..........          94         185  ..........
Other Buses.............................................         687         992       1,906  ..........         514         754       1,428  ..........
Refuse Trucks...........................................  ..........         747       1,459  ..........  ..........         579       1,115  ..........
School Buses............................................         170         263         484  ..........         127         199         362  ..........
Short-Haul Combination Trucks...........................  ..........       1,251       2,224  ..........  ..........         992       1,771  ..........
Short-Haul Single Unit Trucks...........................         216         429         889  ..........         168         337         694  ..........
Transit Buses...........................................         675         896  ..........       1,669         504         681  ..........       1,241
--------------------------------------------------------------------------------------------------------------------------------------------------------

2. Costs Associated With Changes in Fuel Consumption on Gasoline 
Engines
    We have estimated a decrease in fuel costs, i.e., fuel savings, 
associated with the final ORVR requirements on gasoline engines. Due to 
the ORVR systems, evaporative emissions that would otherwise be emitted 
into the atmosphere will be trapped and subsequently burned in the 
engine. We describe the approach taken to estimate these impacts in 
Chapter 7.2.2 of the RIA. These newly captured evaporative emissions 
are converted to gallons and then multiplied by AEO 2019 reference case 
gasoline prices (converted to 2017 dollars) to arrive at the monetized 
impacts. These impacts are shown in Table V-18. In the aggregate, we 
estimate that the ORVR requirements in the final program will result in 
an annual reduction of approximately 0.3 million (calendar year 2027) 
to 4.9 million (calendar year 2045) gallons of gasoline, representing 
roughly 0.1 percent of gasoline consumption from impacted vehicles.

[[Page 4414]]

   Table V-18--MY2027 Lifetime Fuel Costs per Gasoline Vehicle Associated With ORVR Requirements, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                   3% Discount rate                    7% Discount rate
                                         -----------------------------------------------------------------------
                                           Light HDE  Medium HDE   Heavy HDE   Light HDE  Medium HDE   Heavy HDE
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks............     120,876     150,530     192,727      94,841     118,108     151,216
Motor Homes.............................      30,329      38,339      48,887      21,905      27,691      35,309
Other Buses.............................     273,223  ..........  ..........     201,982  ..........  ..........
School Buses............................      69,242  ..........  ..........      51,188  ..........  ..........
Short-Haul Single Unit Trucks...........      86,494     109,427     139,754      66,791      84,501     107,918
Transit Buses...........................     269,797  ..........  ..........     199,449  ..........  ..........
----------------------------------------------------------------------------------------------------------------
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks............     120,744     150,349     192,470      94,739     117,969     151,019
Motor Homes.............................      30,271      38,260      48,781      21,864      27,635      35,233
Other Buses.............................     272,656  ..........  ..........     201,570  ..........  ..........
School Buses............................      69,110  ..........  ..........      51,092  ..........  ..........
Short-Haul Single Unit Trucks...........      86,397     109,292     139,566      66,717      84,399     107,777
Transit Buses...........................     269,245  ..........  ..........     199,047  ..........  ..........
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks............        -132        -181        -257        -102        -139        -197
Motor Homes.............................         -58         -79        -106         -41         -56         -75
Other Buses.............................        -567  ..........  ..........        -412  ..........  ..........
School Buses............................        -132  ..........  ..........         -96  ..........  ..........
Short-Haul Single Unit Trucks...........         -97        -135        -187         -74        -102        -141
Transit Buses...........................        -552  ..........  ..........        -402  ..........  ..........
----------------------------------------------------------------------------------------------------------------

3. Emission-Related Repair Cost Impacts Associated With the Final 
Program
    The final extended warranty and useful life requirements will have 
an impact on emission-related repair costs incurred by truck owners. 
Researchers have noted the relationships among quality, reliability, 
and warranty for a variety of goods.\444\ Wu,\445\ for instance, 
examines how analyzing warranty data can provide ``early warnings'' on 
product problems that can then be used for design modifications. 
Guajardo et al. describe one of the motives for warranties to be 
``incentives for the seller to improve product quality''; specifically 
for light-duty vehicles, they find that buyers consider warranties to 
substitute for product quality, and to complement service quality.\446\ 
Murthy and Jack, for new products, and Saidi-Mehrabad et al. for 
second-hand products, consider the role of warranties in improving a 
buyer's confidence in quality of the good.447 448
---------------------------------------------------------------------------

    \444\ Thomas, M., and S. Rao (1999). ``Warranty Economic 
Decision Models: A Summary and Some Suggested Directions for Future 
Research.'' Operations Research 47(6):807-820.
    \445\ Wu, S (2012). Warranty Data Analysis: A Review. Quality 
and Reliability Engineering International 28: 795-805.
    \446\ Guajardo, J., M Cohen, and S. Netessine (2016). ``Service 
Competition and Product Quality in the U.S. Automobile Industry.'' 
Management Science 62(7):1860-1877. The other rationales are 
protection for consumers against failures, provision of product 
quality information to consumers, and a means to distinguish 
consumers according to their risk preferences.
    \447\ Murthy, D., and N. Jack (2009). ``Warranty and 
Maintenance,'' Chapter 18 in Handbook of Maintenance Management and 
Engineering, Mohamed Ben-Daya et al., editors. London: Springer.
    \448\ Saidi-Mehrabad, M., R. Noorossana, and M. Shafiee (2010). 
``Modeling and analysis of effective ways for improving the 
reliability of second-hand products sold with warranty.'' 
International Journal of Advanced Manufacturing Technology 46: 253-
265.
---------------------------------------------------------------------------

    On the one hand, we expect owner-incurred emission repair costs to 
decrease due to the final program because the longer emission warranty 
requirements will result in more repair costs covered by the OEMs. 
Further, we expect improved serviceability in an effort by OEMs to 
decrease the repair costs that they will incur. We also expect that the 
longer useful life periods in the final standards will result in more 
durable parts to ensure regulatory compliance over the longer 
timeframe. On the other hand, we also expect that the more costly 
emission control systems required by the final program may result in 
higher repair costs which might increase owner-incurred costs outside 
the warranty and/or useful life periods.
    As discussed in Section V.A.2, we have estimated increased OEM 
costs associated with increased warranty liability (i.e., longer 
warranty periods), and for more durable parts resulting from the longer 
useful life periods. These costs are accounted for via increased 
warranty costs and increased research and development (R&D) costs. We 
also included additional aftertreatment costs in the direct 
manufacturing costs to address the increased useful life requirements 
(e.g., larger catalyst volume; see Chapters 2 and 3 of the RIA for 
detailed discussions). We estimate that the new useful life and 
warranty provisions will help to reduce emission repair costs during 
the emission warranty and regulatory useful life periods, and possibly 
beyond.
    In the proposal, to estimate impacts on emission repair costs, we 
began with an emission repair cost curve derived from an industry white 
paper.\449\ Some commenters took exception to the approach we took, 
preferring instead that we use what they consider to be a more 
established repair and maintenance cost estimate from the American 
Transportation Research

[[Page 4415]]

Institute.\450\ After careful consideration of the ATRI data, we 
derived a cost per mile value for repair and maintenance based on the 
10 years of data gathered and presented. We chose to use the ATRI data 
in place of the data used in the proposal because it constituted 10 
years of data from an annually prepared study compared to the one year 
of data behind the study used in the proposal.
---------------------------------------------------------------------------

    \449\ See ``Mitigating Rising Maintenance & Repair Costs for 
Class-8 Truck Fleets, Effective Data & Strategies to Leverage Newer 
Trucks to Reduce M&R Costs,'' Fleet Advantage Whitepaper Series, 
2018.
    \450\ ``An Analysis of the Operational Costs of Trucking: 2021 
Update,'' American Transportation Research Institute, November 2021.
---------------------------------------------------------------------------

    Because the ATRI data represent heavy HD combination vehicles it 
was necessary for us to scale the ATRI values for applicability to HD 
vehicles with different sized engines having different emission-control 
system costs. We have done this in the same way as was discussed 
earlier for scaling of warranty cost (see Table V-6). Given that future 
engines and vehicles will be equipped with new, more costly technology, 
it is possible that the repair costs for vehicles under the final 
program will be higher than the repair costs in the baseline. We have 
included such an increase for the period beyond useful life. This is 
perhaps conservative because it seems reasonable to assume that the R&D 
used to improve durability during the useful life period would also 
improve durability beyond it. Nonetheless, we also think it is 
reasonable to include an increase in repair costs, relative to the 
baseline case, because the period beyond useful life is of marginally 
less concern to manufacturers.\451\ Lastly, since our warranty and 
useful life provisions pertain to emissions-related systems and their 
repair, we adjusted the ATRI values by 10.8 percent to arrive at an 
emission-related repair cost. The 10.8 percent value was similarly used 
in the proposal and was derived by EPA using data in the Fleet 
Advantage Whitepaper. Table V-19 shows how we have scaled the repair 
and maintenance costs derived from the ATRI study.
---------------------------------------------------------------------------

    \451\ This is not meant to suggest that manufacturers no longer 
care about their products beyond their regulatory useful life, but 
rather to reflect the expectation that regulatory pressures--i.e., 
regulatory compliance during the useful life--tend to focus 
manufacturer resources.
---------------------------------------------------------------------------

    Importantly, during the warranty period, there are no emission-
related repair costs incurred by owner/operators since those will be 
covered under warranty.

                      Table V-19--Scaling Approach Used in Estimating Baseline Emission-Related Repair Costs per Mile, 2017 Cents *
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                  Repair & maintenance         Emission-related repair
                                                                                             ------------------------------      (10.8% of repair &
           MOVES  regulatory class                           Scaling approach                                                       maintenance)
                                                                                               Diesel   Gasoline     CNG   -----------------------------
                                                                                                                             Diesel   Gasoline     CNG
--------------------------------------------------------------------------------------------------------------------------------------------------------
Light HDE...................................  Base Light HDE DMC/Base Diesel Heavy HDE DMC..      10.1      7.28  ........      1.09      0.79  ........
Medium HDE..................................  Base Medium HDE DMC/Base Diesel Heavy HDE DMC.      10.3      7.28  ........      1.12      0.79  ........
Heavy HDE...................................  Base Heavy HDE DMC/Base Diesel Heavy HDE DMC..      15.8      7.28      23.2      1.71      0.79      2.52
Urban bus...................................  Base Urban bus DMC/Base Diesel Heavy HDE DMC..      9.80  ........      16.2      1.06  ........      1.75
--------------------------------------------------------------------------------------------------------------------------------------------------------
* The Base Diesel Heavy HDE DMC would be the $5,816 value shown in Table V-2; shown is scaling of baseline emission-repair costs per mile although we
  also scaled emission-repair cost per hour and applied those values for most vocational vehicles; this is detailed in Chapter 7.2.3 of the final RIA.

    We present more details in Chapter 7 of the RIA behind the 
emission-repair cost values we are using, the scaling used and the 10.8 
percent emission-related repair adjustment factor and how it was 
derived. As done for warranty costs, we have used estimated ages for 
when warranty and useful life are reached, using the required miles, 
ages and hours along with the estimated miles driven and hours of 
operation for each specific type of vehicle. This means that warranty 
and useful life ages are reached in different years for different 
vehicles, even if they belong to the same service class and have the 
same regulatory warranty and useful life periods. For example, we 
expect warranty and useful life ages to be attained at different points 
in time by a long-haul combination truck driving over 100,000 miles per 
year or over 2,000 hours per year and a refuse truck driven around 
40,000 miles per year or operating less than 1,000 hours per year. The 
resultant MY2027 lifetime emission-related repair costs are shown in 
Table V-20 for diesel HD vehicles, in Table V-21 for gasoline HD 
vehicles, and in Table V-22 for CNG HD vehicles. Since these costs 
occur over time, we present them using both a 3 percent and a 7 percent 
discount rate. Note that these costs assume that all emission-related 
repair costs are paid by manufacturers during the warranty period, and 
beyond the warranty period the emission-related repair costs are 
incurred by owners/operators.

                               Table V-20--MY2027 Lifetime Emission-Related Repair Costs per Diesel Vehicle, 2017 Dollars
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         3% Discount rate                                7% Discount rate
                                                         -----------------------------------------------------------------------------------------------
                                                           Light HDE  Medium HDE   Heavy HDE   Urban bus   Light HDE  Medium HDE   Heavy HDE   Urban bus
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                      FRM Baseline
--------------------------------------------------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks............................  ..........  ..........      22,041  ..........  ..........  ..........      16,138  ..........
Long-Haul Single Unit Trucks............................       3,208       2,493       3,060  ..........       2,440       1,790       2,109  ..........
Motor Homes.............................................  ..........         613         936  ..........  ..........         394         602  ..........
Other Buses.............................................       4,292       3,668       4,719  ..........       3,083       2,499       3,074  ..........
Refuse Trucks...........................................  ..........       2,222       3,110  ..........  ..........       1,506       2,065  ..........
School Buses............................................       1,148       1,050       1,604  ..........         771         684       1,045  ..........
Short-Haul Combination Trucks...........................  ..........       6,635       8,088  ..........  ..........       5,003       5,823  ..........
Short-Haul Single Unit Trucks...........................       1,799       1,292       1,973  ..........       1,318         876       1,338  ..........

[[Page 4416]]

 
Transit Buses...........................................       4,242       3,625  ..........       3,941       3,047       2,469  ..........       2,732
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                              FRM Baseline + Final Program
--------------------------------------------------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks............................  ..........  ..........      25,070  ..........  ..........  ..........      17,497  ..........
Long-Haul Single Unit Trucks............................       2,284       1,531       1,524  ..........       1,509         956         906  ..........
Motor Homes.............................................  ..........         480         728  ..........  ..........         272         415  ..........
Other Buses.............................................       4,090       3,261       3,454  ..........       2,598       1,978       1,979  ..........
Refuse Trucks...........................................  ..........       1,408       2,038  ..........  ..........         819       1,180  ..........
School Buses............................................         667         772       1,174  ..........         378         439         673  ..........
Short-Haul Combination Trucks...........................  ..........       7,029       6,436  ..........  ..........       4,960       4,225  ..........
Short-Haul Single Unit Trucks...........................         764         721       1,115  ..........         451         421         655  ..........
Transit Buses...........................................       4,042       3,224  ..........       2,394       2,567       1,955  ..........       1,370
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                           Increased Cost of the Final Program
--------------------------------------------------------------------------------------------------------------------------------------------------------
Long-Haul Combination Trucks............................  ..........  ..........       3,028  ..........  ..........  ..........       1,359  ..........
Long-Haul Single Unit Trucks............................        -924        -962      -1,536  ..........        -931        -834      -1,203  ..........
Motor Homes.............................................  ..........        -132        -207  ..........  ..........        -122        -187  ..........
Other Buses.............................................        -203        -406      -1,265  ..........        -486        -520      -1,095  ..........
Refuse Trucks...........................................  ..........        -814      -1,072  ..........  ..........        -687        -885  ..........
School Buses............................................        -481        -278        -430  ..........        -393        -245        -372  ..........
Short-Haul Combination Trucks...........................  ..........         394      -1,651  ..........  ..........         -43      -1,598  ..........
Short-Haul Single Unit Trucks...........................      -1,035        -570        -857  ..........        -867        -455        -684  ..........
Transit Buses...........................................        -200        -402  ..........      -1,547        -480        -514  ..........      -1,362
--------------------------------------------------------------------------------------------------------------------------------------------------------

          Table V-21--MY2027 Lifetime Emission-Related Repair Costs per Gasoline Vehicle, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                   3% Discount rate                    7% Discount rate
                                         -----------------------------------------------------------------------
                                           Light HDE  Medium HDE   Heavy HDE   Light HDE  Medium HDE   Heavy HDE
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks............       2,324       2,324       2,324       1,768       1,768       1,768
Motor Homes.............................         431         431         431         278         278         278
Other Buses.............................       3,111  ..........  ..........       2,234  ..........  ..........
School Buses............................         832  ..........  ..........         559  ..........  ..........
Short-Haul Single Unit Trucks...........       1,304       1,304       1,304         955         955         955
Transit Buses...........................       3,074  ..........  ..........       2,208  ..........  ..........
----------------------------------------------------------------------------------------------------------------
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks............       1,831       1,831       1,831       1,271       1,271       1,271
Motor Homes.............................         275         275         275         156         156         156
Other Buses.............................       2,898  ..........  ..........       1,917  ..........  ..........
School Buses............................         442  ..........  ..........         252  ..........  ..........
Short-Haul Single Unit Trucks...........         764         764         764         483         483         483
Transit Buses...........................       2,865  ..........  ..........       1,895  ..........  ..........
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks............        -493        -493        -493        -497        -497        -497
Motor Homes.............................        -156        -156        -156        -122        -122        -122
Other Buses.............................        -212  ..........  ..........        -317  ..........  ..........
School Buses............................        -390  ..........  ..........        -306  ..........  ..........
Short-Haul Single Unit Trucks...........        -540        -540        -540        -471        -471        -471
Transit Buses...........................        -210  ..........  ..........        -313  ..........  ..........
----------------------------------------------------------------------------------------------------------------

[[Page 4417]]

             Table V-22--MY2027 Lifetime Emission-Related Repair Costs per CNG Vehicle, 2017 Dollars
----------------------------------------------------------------------------------------------------------------
                                                                     3% Discount rate        7% Discount rate
                                                                 -----------------------------------------------
                                                                   Heavy HDE   Urban bus   Heavy HDE   Urban bus
----------------------------------------------------------------------------------------------------------------
                                                  FRM Baseline
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks....................................       4,517  ..........       3,113  ..........
Other Buses.....................................................       6,966  ..........       4,537  ..........
Refuse Trucks...................................................       4,590  ..........       3,048  ..........
School Buses....................................................       2,368  ..........       1,542  ..........
Short-Haul Combination Trucks...................................      11,938  ..........       8,595  ..........
Short-Haul Single Unit Trucks...................................       2,912  ..........       1,975  ..........
Transit Buses...................................................  ..........       6,532  ..........       4,529
----------------------------------------------------------------------------------------------------------------
                                          FRM Baseline + Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks....................................       1,720  ..........       1,029  ..........
Other Buses.....................................................       3,807  ..........       2,194  ..........
Refuse Trucks...................................................       2,260  ..........       1,317  ..........
School Buses....................................................       1,294  ..........         746  ..........
Short-Haul Combination Trucks...................................       7,723  ..........       5,143  ..........
Short-Haul Single Unit Trucks...................................       1,248  ..........         737  ..........
Transit Buses...................................................  ..........       2,822  ..........       1,626
----------------------------------------------------------------------------------------------------------------
                                       Increased Cost of the Final Program
----------------------------------------------------------------------------------------------------------------
Long-Haul Single Unit Trucks....................................      -2,797  ..........      -2,084  ..........
Other Buses.....................................................      -3,158  ..........      -2,344  ..........
Refuse Trucks...................................................      -2,330  ..........      -1,732  ..........
School Buses....................................................      -1,074  ..........        -797  ..........
Short-Haul Combination Trucks...................................      -4,215  ..........      -3,452  ..........
Short-Haul Single Unit Trucks...................................      -1,664  ..........      -1,238  ..........
Transit Buses...................................................  ..........      -3,710  ..........      -2,903
----------------------------------------------------------------------------------------------------------------

C. Program Costs

    Using the cost elements outlined in Sections V.A and V.B, we have 
estimated the costs associated with the final program. Costs are 
presented in more detail in Chapter 7 of the RIA. As noted earlier, 
costs are presented in 2017 dollars in undiscounted annual values along 
with present values (PV) and equivalent annualized values (EAV) at both 
3 and 7 percent discount rates with values discounted to the 2027 
calendar year.

Table V-23--Total Technology & Operating Cost Impacts of the Final Program Relative to the Baseline Case, All Regulatory Classes and All Fuels, Billions
                                                                   of 2017 Dollars \a\
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                       Direct   Indirect               Other                Total    Emission                          Total
            Calendar year               tech    warranty   Indirect   indirect   Indirect    tech     repair     Urea    Fuel cost   operating   Program
                                        cost      cost     R&D cost     cost      profit     cost      cost      cost                  cost       cost
--------------------------------------------------------------------------------------------------------------------------------------------------------
2027................................      1.1        2.1       0.21       0.34      0.058      3.8       0.00     0.06     -0.0004       0.057       3.9
2028................................      1.1        2.1       0.20       0.32      0.055      3.7      -0.05     0.12     -0.0008        0.07       3.8
2029................................      1.0        2.1       0.19       0.31      0.053      3.7      -0.30     0.18     -0.0013       -0.12       3.6
2030................................      1.0        2.1      0.051       0.30      0.052      3.5      -0.43     0.25     -0.0017       -0.19       3.4
2031................................      1.0        2.2      0.050       0.30      0.051      3.6      -0.50     0.33     -0.0022       -0.17       3.4
2032................................     0.99        2.2      0.049       0.29      0.050      3.6      -0.57     0.41     -0.0027       -0.16       3.4
2033................................     0.98        2.2      0.049       0.29      0.050      3.6      -0.61     0.47     -0.0034       -0.14       3.5
2034................................     0.98        2.3      0.049       0.29      0.049      3.6      -0.64     0.53     -0.0041       -0.11       3.5
2035................................     0.96        2.3      0.048       0.28      0.049      3.7      -0.66     0.58     -0.0048       -0.08       3.6
2036................................     0.95        2.3      0.048       0.28      0.048      3.7      -0.66     0.63     -0.0054       -0.04       3.6
2037................................     0.95        2.4      0.048       0.28      0.048      3.7      -0.60     0.68     -0.0060        0.07       3.8
2038................................     0.95        2.4      0.048       0.28      0.048      3.7      -0.54     0.72     -0.0066        0.17       3.9
2039................................     0.95        2.5      0.047       0.28      0.048      3.8      -0.49     0.76     -0.0072        0.27       4.0
2040................................     0.95        2.5      0.047       0.28      0.048      3.8      -0.45     0.80     -0.0078        0.34       4.2
2041................................     0.95        2.5      0.047       0.28      0.048      3.9      -0.41     0.84     -0.0083        0.41       4.3
2042................................     0.95        2.6      0.047       0.28      0.048      3.9      -0.39     0.87     -0.0088        0.47       4.4
2043................................     0.95        2.6      0.047       0.28      0.048      3.9      -0.37     0.91     -0.0093        0.53       4.5
2044................................     0.95        2.7      0.048       0.28      0.048      4.0      -0.35     0.94     -0.0097        0.57       4.6
2045................................     0.95        2.7      0.048       0.28      0.048      4.1      -0.34     0.97      -0.010        0.62       4.7
PV, 3%..............................       14         33        1.1        4.2       0.72       53       -6.2      7.7      -0.069         1.4        55
PV, 7%..............................       10         24       0.90        3.0       0.52       38       -4.3      4.9      -0.043        0.60        39
EAV, 3%.............................      1.0        2.3      0.078       0.29      0.050      3.7      -0.43     0.54     -0.0048       0.099       3.8

[[Page 4418]]

 
EAV, 7%.............................      1.0        2.3      0.087       0.29      0.051      3.7      -0.42     0.48     -0.0042       0.058       3.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ Values show 2 significant digits; negative cost values denote savings; calendar year values are undiscounted, present values are discounted to 2027;
  Program Cost is the sum of Total Tech Cost and Total Operating Cost. Note also that the Information Collection Request costs addressed in Section XII
  would fall within the ``Other'' indirect costs shown here.

VI. Estimated Emissions Reductions From the Final Program

    The final program, which is described in detail in Sections III and 
IV, is expected to reduce emissions from highway heavy-duty engines in 
several ways. We project the final emission standards for heavy-duty CI 
engines will reduce tailpipe emissions of NOX; the 
combination of the final low-load test cycle and off-cycle test 
procedure for CI engines will help to ensure that the reductions in 
tailpipe emissions are achieved in-use, not only under high-speed, on-
highway conditions, but also under low-load and idle conditions. We 
also project reduced tailpipe emissions of NOX, CO, PM, 
VOCs, and associated air toxics from the final emission standards for 
heavy-duty SI engines, particularly under cold-start and high-load 
operating conditions. The longer emission warranty and regulatory 
useful life requirements for heavy-duty CI and SI engines in the final 
rule will help maintain the expected emission reductions for all 
pollutants, including primary exhaust PM2.5, throughout the 
useful life of the engine. The onboard refueling vapor recovery 
requirements for heavy-duty SI engines in the final rule will reduce 
VOCs and associated air toxics. See RIA Chapter 5.3 for details on 
projected emission reductions of each pollutant.
    Section VI.A provides an overview of the methods used to estimate 
emission reductions from our final program. All the projected emission 
reductions from the final program are outlined in Section VI.B, with 
more details provided in the RIA Chapter 5. Section VI.C presents 
projected emission reductions from the final program by engine 
operations and processes (e.g., medium-to-high load or low-load engine 
operations).

A. Emission Inventory Methodology

    To estimate the emission reductions from the final program, we used 
the current public version of EPA's Motor Vehicle Emission Simulator 
(MOVES) model, MOVES3. MOVES3 includes all the model updates previously 
made for the version of the MOVES model used for the NPRM analysis 
(``MOVES CTI NPRM''), as well as other more recent updates. Detailed 
descriptions of the underlying data and analyses that informed the 
model updates are discussed in Chapter 5.2 of the RIA and documented in 
peer-reviewed technical reports referenced in the RIA. Inputs developed 
to model the national emission inventories for the final program are 
also discussed in Chapter 5.2.2 of the RIA.

B. Estimated Emission Reductions From the Final Program

    As discussed in Sections III and IV, the final program includes 
new, more stringent numeric emission standards, as well as longer 
regulatory useful life and emissions warranty periods compared to 
today's standards. Our estimates of the emission impacts of the final 
program in calendar years 2030, 2040, and 2045 are presented in Table 
VI-1. As shown in Table VI-1, we estimate that the final program will 
reduce NOX emissions from highway heavy-duty vehicles by 48 
percent nationwide in 2045. We also estimate an eight percent reduction 
in primary exhaust PM2.5 from highway heavy-duty vehicles. 
VOC emissions from heavy-duty vehicles will be 23 percent lower. 
Emissions of CO from heavy-duty vehicles are estimated to decrease by 
18 percent. Reductions in heavy-duty vehicle emissions of other 
pollutants, including air toxics, range from an estimated reduction of 
about 28 percent for benzene to about seven percent change in 
acetaldehyde. RIA Chapter 5.5.2 includes additional details on the 
emission reductions by vehicle fuel type; Chapter 5.5.4 provides our 
estimates of criteria pollutant emissions reductions for calendar years 
2027 through 2045.
    As the final program is implemented, emission reductions are 
expected to increase over time as the fleet turns over to new, 
compliant engines. We estimate no change in CO2 emissions 
from the final program, based on data in our feasibility and cost 
analyses of the final program (see Section III for more 
discussion).\452\
---------------------------------------------------------------------------

    \452\ This estimate includes the assumption that vehicle sales 
will not change in response to the final rule. See Section X for 
further discussion on vehicle sales impacts of this final rule.

  Table VI-1--Annual Emission Reductions From Heavy-Duty Vehicles in Calendar Years (CY) 2030, 2040, and 2045--
           Emissions With Final Program in Place Relative to the Heavy-Duty Vehicle Emissions Baseline
----------------------------------------------------------------------------------------------------------------
                                             CY2030                    CY2040                    CY2045
                                   -----------------------------------------------------------------------------
             Pollutant                US short                  US short                  US short
                                        tons     % reduction      tons     % reduction      tons     % reduction
----------------------------------------------------------------------------------------------------------------
NOX...............................      139,677           14      398,864           44      453,239           48
VOC...............................        5,018            5       17,139           20       20,758           23
Primary Exhaust PM2.5.............          115            1          491            7          566            8
CO................................       43,978            3      208,935           16      260,750           18
Acetaldehyde......................           36            2          124            6          145            7
Benzene...........................           40            4          177           23          221           28
Formaldehyde......................           29            1          112            7          134            8

[[Page 4419]]

 
Naphthalene.......................            2            1            7           13            9           16
----------------------------------------------------------------------------------------------------------------

C. Estimated Emission Reductions by Engine Operations and Processes

    Looking more closely at the NOX emission inventory from 
highway heavy-duty vehicles, our analysis shows that the final 
standards will reduce emissions across several engine operations and 
processes, with the greatest reductions attributable to medium-to-high 
load engine operations, low-load engine operations, and age effects 
(Table VI-2). Emission reductions attributable to medium-to-high load 
engine operations are based on changes in the new numeric emissions 
standards compared to existing standards and corresponding test 
procedures, as described in preamble Section III. Emission reductions 
attributable to the age effects category are based on longer useful 
life and warranty periods in the final rule, which are described in 
preamble Section IV.
    Table 5-13 in Chapter 5.2.2 of the RIA shows that tampering and 
mal-maintenance significantly increases emissions from current heavy 
heavy-duty engines (e.g., we estimate a 500 percent increase in 
NOX emissions for heavy heavy-duty vehicles due to 
NOX aftertreatment malfunction). Absent the final rule, 
these substantial increases in emissions from tampering and mal-
maintenance could potentially have large impact on the HD 
NOX inventory. However, the longer regulatory useful life 
and emission-related warranty requirements in the final rule will 
ensure that more stringent standards are met for a longer period of 
time while the engines are in use. Specifically, we estimate 18 percent 
fewer NOX emissions in 2045 due to the longer useful life 
and warranty periods reducing the likelihood of tampering and mal-
maintenance after the current useful life periods of heavy-duty CI 
engines.453 454 We note that these estimates of emissions 
impacts from tampering and mal-maintenance of heavy-duty engines 
reflect currently available data and may not fully reflect the extent 
of emissions impacts from tampering or mal-maintenance; thus, 
additional data on the emissions impacts of heavy-duty tampering and 
mal-maintenance may show that there would be additional emissions 
reductions from the final rule.
---------------------------------------------------------------------------

    \453\ See Chapter 5.2.2 of the RIA for a discussion of how we 
calculate the emission rates due to the final useful life and 
warranty periods for Light, Medium, and Heavy heavy-duty engines.
    \454\ Although we anticipate emission benefits from the 
lengthened warranty and useful life periods from gasoline and NG-
fueled vehicles, they were not included in the analysis done for the 
final rule (see RIA Chapter 5.2 for details).
---------------------------------------------------------------------------

    Further, due to insufficient data, we are currently unable to 
quantify the impacts of other provisions to improve maintenance and 
serviceability of emission controls systems (e.g., updated maintenance 
intervals, requiring manufacturers to provide more information on how 
to diagnose and repair emission control systems, as described in 
preamble Section IV). We expect the final provisions to improve 
maintenance and serviceability will reduce incentives to tamper with 
the emission control systems on MY 2027 and later engines, which would 
avoid large increases in emissions that would impact the reductions 
projected from the final rule. For example, we estimate a greater than 
3000 percent increase in NOX emissions for heavy heavy-duty 
vehicles due to malfunction of the NOX emissions 
aftertreatment on a MY 2027 and later heavy heavy-duty vehicle. As 
such, the maintenance and serviceability provisions combined with the 
longer useful life and warranty periods will provide a comprehensive 
approach to ensure that the new, much more stringent emissions 
standards are met during in use operations.
    Table VI-2 compares NOX emissions in 2045 from different 
engine operations and processes with and without the final standards. A 
graphical comparison of NOX emissions by process is included 
in RIA Chapter 5.5.3.

                       Table VI-2--Heavy-Duty NOX Emission Reductions by Process in CY2045
                                                    [US tons]
----------------------------------------------------------------------------------------------------------------
                                        Emission inventory                     Percent       Emission inventory
     Engine operation or process       contribution without      Tons      reduction from     contribution with
                                         final program (%)     reduced        baseline        final program (%)
----------------------------------------------------------------------------------------------------------------
Medium- to High-Load.................                    36      217,708                64                    24
Low-Load.............................                    30      177,967                63                    21
Aging................................                    22       35,750                18                    34
Extended Idle & APU..................                     2       11,692                63                     1
Starts...............................                     5       10,122                23                     7
Historical Fleet (MY 2010 to 2026)...                     6            0                 0                    12
----------------------------------------------------------------------------------------------------------------

VII. Air Quality Impacts of the Final Rule

    As discussed in Section VI, we project the standards in the final 
rule will result in meaningful reductions in emissions of 
NOX, VOC, CO and PM2.5. When feasible, we conduct 
full-scale photochemical air quality modeling to accurately project 
levels of criteria and air toxic pollutants, because the atmospheric 
chemistry related to ambient concentrations of PM2.5, ozone,

[[Page 4420]]

and air toxics is very complex. Air quality modeling was performed for 
the proposed rule and demonstrated improvements in concentrations of 
air pollutants. Given the similar structure of the proposed and final 
programs, the geographic distribution of emissions reductions and 
modeled improvements in air quality are consistent and demonstrate that 
the final rule will lead to substantial improvements in air 
quality.\455\
---------------------------------------------------------------------------

    \455\ Additional detail on the air quality modeling inventory 
used in the proposed rule, along with the final rule emission 
reductions, can be found in Chapter 5 of the RIA.
---------------------------------------------------------------------------

    Specifically, we expect this rule will decrease ambient 
concentrations of air pollutants, including significant improvements in 
ozone concentrations in 2045 as demonstrated in the air quality 
modeling analysis. We also expect reductions in ambient 
PM2.5, NO2 and CO due to this rule. Although the 
spatial resolution of the air quality modeling is not sufficient to 
quantify it, this rule's emission reductions will also reduce air 
pollution in close proximity to major roadways, where concentrations of 
many air pollutants are elevated and where people of color and people 
with low income are disproportionately exposed.
    The emission reductions provided by the final standards will be 
important in helping areas attain the NAAQS and prevent future 
nonattainment. In addition, the final standards are expected to result 
in improvements in nitrogen deposition and visibility. Additional 
information and maps showing expected changes in ambient concentrations 
of air pollutants in 2045 are included in the proposal, Chapter 6 of 
the RIA and in the Air Quality Modeling Technical Support Document from 
the proposed rule.456 457
---------------------------------------------------------------------------

    \456\ USEPA (2021) Technical Support Document: Air Quality 
Modeling for the HD 2027 Proposal. EPA-HQ-OAR-2019-0055. October 
2021.
    \457\ Section VII of the proposed rule preamble, 87 FR 17414 
(March 28, 2022).
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    The proposed rule air quality modeling analysis consisted of a base 
case, reference scenario, and control scenario. The ``base'' case 
represents 2016 air quality. The ``reference'' scenario represents 
projected 2045 air quality without the proposed rule and the 
``control'' scenario represents projected 2045 emissions with the 
proposed rule. Air quality modeling was done for the future year 2045 
when the program will be fully implemented and when most of the 
regulated fleet will have turned over.

A. Ozone

    The scenario modeled for the proposed rule reduced 8-hour ozone 
design values significantly in 2045. Ozone design values decreased by 
more than 2 ppb in over 150 counties, and over 200 additional modeled 
counties are projected to have decreases in ozone design values of 
between 1 and 2 ppb in 2045. Our modeling projections indicate that 
some counties will have design values above the level of the 2015 NAAQS 
in 2045, and the rule will help those counties, as well as other 
counties, in reducing ozone concentrations. Table VII-1 shows the 
average projected change in 2045 8-hour ozone design values due to the 
modeled scenario. Counties within 10 percent of the level of the NAAQS 
are intended to reflect counties that, although not violating the 
standard, would also be affected by changes in ambient levels of ozone 
as they work to ensure long-term attainment or maintenance of the ozone 
NAAQS. The projected changes in design values, summarized in Table VII-
1, indicate in different ways the overall improvement in ozone air 
quality due to emission reductions from the modeled scenario.

           Table VII-1--Average Change in Projected 8-Hour Ozone Design Values in 2045 Due to the Rule
----------------------------------------------------------------------------------------------------------------
                                                                                                  Population-
                                                 Number of        2045        Average change    weighted average
        Projected design value category           counties   Population \a\   in 2045 design    change in design
                                                                                value (ppb)       value (ppb)
----------------------------------------------------------------------------------------------------------------
all modeled counties..........................          457     246,949,949             -1.87              -2.23
counties with 2016 base year design values              118     125,319,158             -2.12              -2.43
 above the level of the 2015 8-hour ozone
 standard.....................................
counties with 2016 base year design values              245      93,417,097             -1.83              -2.10
 within 10% of the 2015 8-hour ozone standard.
counties with 2045 reference design values               15      37,758,488             -2.26              -3.03
 above the level of the 2015 8-hour ozone
 standard.....................................
counties with 2045 reference design values               56      39,302,665             -1.78              -2.02
 within 10% of the 2015 8-hour ozone standard.
counties with 2045 control design values above           10      27,930,138             -2.36              -3.34
 the level of the 2015 8-hour ozone standard..
counties with 2045 control design values                 42      31,395,617             -1.69              -1.77
 within 10% of the 2015 8-hour ozone standard.
----------------------------------------------------------------------------------------------------------------
\a\ Population numbers based on Woods & Poole data. Woods & Poole Economics, Inc. (2015). Complete Demographic
  Database. Washington, DC. http://www.woodsandpoole.com/index.php.

B. Particulate Matter

    The scenario modeled for the proposed rule reduced 24-hour and 
annual PM2.5 design values in 2045. Annual PM2.5 
design values in the majority of modeled counties decreased by between 
0.01 and 0.05 [mu]g/m\3\ and by greater than 0.05 [mu]g/m\3\ in over 75 
additional counties. 24-hour PM2.5 design values decreased 
by between 0.15 and 0.5 [mu]g/m\3\ in over 150 counties and by greater 
than 0.5 [mu]g/m\3\ in 5 additional counties. Our modeling projections 
indicate that some counties will have design values above the level of 
the 2012 PM2.5 NAAQS in 2045 and the rule will help those 
counties, as well as other counties, in reducing PM2.5 
concentrations. Table VII-2 and Table VII-3 present the average 
projected changes in 2045 annual and 24-hour PM2.5 design 
values. Counties within 10 percent of the level of the NAAQS are 
intended to reflect counties that, although not violating the 
standards, would also be affected by changes in ambient levels of 
PM2.5 as they work to ensure long-term attainment or 
maintenance of the annual and/or 24-hour PM2.5 NAAQS. The 
projected changes in PM2.5 design values, summarized in 
Table VII-2 and Table VII-3, indicate in different ways the overall 
improvement in PM2.5 air quality due to the emission 
reductions resulting from the modeled scenario. We expect this rule's 
reductions in directly emitted PM2.5 will also contribute to 
reductions in PM2.5 concentrations near roadways, although 
our air quality modeling is not of sufficient resolution to capture 
that impact.

[[Page 4421]]

           Table VII-2--Average Change in Projected Annual PM2.5 Design Values in 2045 Due to the Rule
----------------------------------------------------------------------------------------------------------------
                                                                                                  Population-
                                                 Number of        2045        Average change    weighted average
        Projected design value category           counties   Population \a\   in 2045 design    change in design
                                                                               value (ug/m3)     value (ug/m3)
----------------------------------------------------------------------------------------------------------------
all modeled counties..........................          568     273,604,437             -0.04              -0.04
counties with 2016 base year design values               17      26,726,354             -0.09              -0.05
 above the level of the 2012 annual PM2.5
 standard.....................................
counties with 2016 base year design values                5       4,009,527             -0.06              -0.06
 within 10% of the 2012 annual PM2.5 standard.
counties with 2045 reference design values               12      25,015,974             -0.10              -0.05
 above the level of the 2012 annual PM2.5
 standard.....................................
counties with 2045 reference design values                6       1,721,445             -0.06              -0.06
 within 10% of the 2012 annual PM2.5 standard.
counties with 2045 control design values above           10      23,320,070             -0.10              -0.05
 the level of the 2012 annual PM2.5 standard..
counties with 2045 control design values                  8       3,417,349             -0.08              -0.09
 within 10% of the 2012 annual PM2.5 standard.
----------------------------------------------------------------------------------------------------------------
\a\ Population numbers based on Woods & Poole data. Woods & Poole Economics, Inc. (2015). Complete Demographic
  Database. Washington, DC. http://www.woodsandpoole.com/index.php.

          Table VII-3--Average Change in Projected 24-Hour PM2.5 Design Values in 2045 Due to the Rule
----------------------------------------------------------------------------------------------------------------
                                                                                                  Population-
                                                 Number of        2045        Average change    weighted average
        Projected design value category           counties   Population \a\   in 2045 design    change in design
                                                                               value (ug/m3)     value (ug/m3)
----------------------------------------------------------------------------------------------------------------
all modeled counties..........................          568     272,852,777             -0.12              -0.17
counties with 2016 base year design values               33      28,394,253             -0.40              -0.67
 above the level of the 2006 daily PM2.5
 standard.....................................
counties with 2016 base year design values               15      13,937,416             -0.18              -0.27
 within 10% of the 2006 daily PM2.5 standard..
counties with 2045 reference design values               29      14,447,443             -0.38              -0.55
 above the level of the 2006 daily PM2.5
 standard.....................................
counties with 2045 reference design values               12      22,900,297             -0.30              -0.59
 within 10% of the 2006 daily PM2.5 standard..
counties with 2045 control design values above           29      14,447,443             -0.38              -0.55
 the level of the 2006 daily PM2.5 standard...
counties with 2045 control design values                 10      19,766,216             -0.26              -0.60
 within 10% of the 2006 daily PM2.5 standard..
----------------------------------------------------------------------------------------------------------------
\a\ Population numbers based on Woods & Poole data. Woods & Poole Economics, Inc. (2015). Complete Demographic
  Database. Washington, DC. http://www.woodsandpoole.com/index.php.

C. Nitrogen Dioxide

    The scenario modeled for the proposed rule decreased annual 
NO2 concentrations in most urban areas and along major 
roadways by more than 0.3 ppb and decreased annual NO2 
concentrations by between 0.01 and 0.1 ppb across much of the rest of 
the country in 2045. The emissions reductions in the modeled scenario 
will also likely decrease 1-hour NO2 concentrations and help 
any potential nonattainment areas attain and maintenance areas maintain 
the NO2 standard.\458\ We expect this rule will also 
contribute to reductions in NO2 concentrations near 
roadways, although our air quality modeling is not of sufficient 
resolution to capture that impact. Section 6.4.4 of the RIA contains 
more detail on the impacts of the rule on NO2 
concentrations.
---------------------------------------------------------------------------

    \458\ As noted in Section II, there are currently no 
nonattainment areas for the NO2 NAAQS.
---------------------------------------------------------------------------

D. Carbon Monoxide

    The scenario modeled for the proposed rule decreased annual CO 
concentrations by more than 0.5 ppb in many urban areas and decreased 
annual CO concentrations by between 0.02 and 0.5 ppb across much of the 
rest of the country in 2045. The emissions reductions in the modeled 
scenario will also likely decrease 1-hour and 8-hour CO concentrations 
and help any potential nonattainment areas attain and maintenance areas 
maintain the CO standard.\459\ Section 6.4.5 of the RIA contains more 
detail on the impacts of the rule on CO concentrations.
---------------------------------------------------------------------------

    \459\ As noted in Section II, there are currently no 
nonattainment areas for the CO NAAQS.
---------------------------------------------------------------------------

E. Air Toxics

    In general, the scenario modeled for the proposed rule had 
relatively little impact on national average ambient concentrations of 
the modeled air toxics in 2045. The modeled scenario had smaller 
impacts on air toxic pollutants dominated by primary emissions (or a 
decay product of a directly emitted pollutant), and relatively larger 
impacts on air toxics that primarily result from photochemical 
transformation, in this case due to the projected large reductions in 
NOX emissions. Specifically, in 2045, our modeling projects 
that ambient benzene and naphthalene concentrations will decrease by 
less than 0.001 ug/m3 across the country. Acetaldehyde 
concentrations will increase slightly across most of the country, while 
formaldehyde will generally have small decreases in most areas and some 
small increases in urban areas. Section 6.4.6 of the RIA contains more 
detail on the impacts of the modeled scenario on air toxics 
concentrations.

F. Visibility

    Air quality modeling was used to project visibility conditions in 
145 Mandatory Class I Federal areas across the United States. The 
results show that the modeled scenario improved visibility in these 
areas.\460\ The average visibility at all modeled Mandatory Class I 
Federal areas on the 20 percent most impaired days is projected to 
improve by 0.04 deciviews, or 0.37 percent, in 2045 due to the rule. 
Section 6.4.7 of the RIA contains more detail on the visibility portion 
of the air quality modeling.
---------------------------------------------------------------------------

    \460\ The level of visibility impairment in an area is based on 
the light-extinction coefficient and a unitless visibility index, 
called a ``deciview'', which is used in the valuation of visibility. 
The deciview metric provides a scale for perceived visual changes 
over the entire range of conditions, from clear to hazy. Under many 
scenic conditions, the average person can generally perceive a 
change of one deciview. The higher the deciview value, the worse the 
visibility. Thus, an improvement in visibility is a decrease in 
deciview value.
---------------------------------------------------------------------------

G. Nitrogen Deposition

    The scenario modeled for the proposed rule projected substantial 
decreases in nitrogen deposition in 2045. The modeled scenario resulted 
in annual decreases of greater than 4 percent in some areas and greater 
than

[[Page 4422]]

1 percent over much of the rest of the country. For maps of deposition 
impacts, and additional information on these impacts, see Section 6.4.8 
of the RIA.

H. Environmental Justice

    EPA's 2016 ``Technical Guidance for Assessing Environmental Justice 
in Regulatory Analysis'' provides recommendations on conducting the 
highest quality analysis feasible, recognizing that data limitations, 
time and resource constraints, and analytic challenges will vary by 
media and regulatory context.\461\ When assessing the potential for 
disproportionately high and adverse health or environmental impacts of 
regulatory actions on people of color, low-income populations, Tribes, 
and/or indigenous peoples, the EPA strives to answer three broad 
questions: (1) Is there evidence of potential environmental justice 
(EJ) concerns in the baseline (the state of the world absent the 
regulatory action)? Assessing the baseline will allow the EPA to 
determine whether pre-existing disparities are associated with the 
pollutant(s) under consideration (e.g., if the effects of the 
pollutant(s) are more concentrated in some population groups). (2) Is 
there evidence of potential EJ concerns for the regulatory option(s) 
under consideration? Specifically, how are the pollutant(s) and its 
effects distributed for the regulatory options under consideration? 
And, (3) do the regulatory option(s) under consideration exacerbate or 
mitigate EJ concerns relative to the baseline? It is not always 
possible to quantitatively assess these questions.
---------------------------------------------------------------------------

    \461\ ``Technical Guidance for Assessing Environmental Justice 
in Regulatory Analysis.'' Epa.gov, Environmental Protection Agency, 
https://www.epa.gov/sites/production/files/2016-06/documents/ejtg_5_6_16_v5.1.pdf. (June 2016).
---------------------------------------------------------------------------

    EPA's 2016 Technical Guidance does not prescribe or recommend a 
specific approach or methodology for conducting an environmental 
justice analysis, though a key consideration is consistency with the 
assumptions underlying other parts of the regulatory analysis when 
evaluating the baseline and regulatory options. Where applicable and 
practicable, the Agency endeavors to conduct such an analysis.\462\ EPA 
is committed to conducting environmental justice analysis for 
rulemakings based on a framework similar to what is outlined in EPA's 
Technical Guidance, in addition to investigating ways to further weave 
environmental justice into the fabric of the rulemaking process.
---------------------------------------------------------------------------

    \462\ As described in this section, EPA evaluated environmental 
justice for this rule as recommended by the EPA 2016 Technical 
Guidance. However, it is EPA's assessment of the relevant statutory 
factors in CAA section 202(a)(3)(A) that justify the final emission 
standards. See section I.D. for further discussion of the statutory 
authority for this rule.
---------------------------------------------------------------------------

    There is evidence that communities with EJ concerns are 
disproportionately impacted by the emissions sources controlled in this 
final rule.\463\ Numerous studies have found that environmental hazards 
such as air pollution are more prevalent in areas where people of color 
and low-income populations represent a higher fraction of the 
population compared with the general population.464 465 466 
Consistent with this evidence, a recent study found that most 
anthropogenic sources of PM2.5, including industrial sources 
and light- and heavy-duty vehicle sources, disproportionately affect 
people of color.\467\ In addition, compared to non-Hispanic Whites, 
some other racial groups experience greater levels of health problems 
during some life stages. For example, in 2018-2020, about 12 percent of 
non-Hispanic Black; 9 percent of non-Hispanic American Indian/Alaska 
Native; and 7 percent of Hispanic children were estimated to currently 
have asthma, compared with 6 percent of non-Hispanic White 
children.\468\ Nationally, on average, non-Hispanic Black and Non-
Hispanic American Indian or Alaska Native people also have lower than 
average life expectancy based on 2019 data, the latest year for which 
CDC estimates are available.\469\
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    \463\ Mohai, P.; Pellow, D.; Roberts Timmons, J. (2009) 
Environmental justice. Annual Reviews 34: 405-430. https://doi.org/10.1146/annurev-environ-082508-094348.
    \464\ Rowangould, G.M. (2013) A census of the near-roadway 
population: public health and environmental justice considerations. 
Trans Res D 25: 59-67. http://dx.doi.org/10.1016/j.trd.2013.08.003.
    \465\ Marshall, J.D., Swor, K.R.; Nguyen, N.P. (2014) 
Prioritizing environmental justice and equality: diesel emissions in 
Southern California. Environ Sci Technol 48: 4063-4068. https://doi.org/10.1021/es405167f.
    \466\ Marshall, J.D. (2008) Environmental inequality: air 
pollution exposures in California's South Coast Air Basin. Atmos 
Environ 21: 5499-5503. https://doi.org/10.1016/j.atmosenv.2008.02.005.
    \467\ C.W. Tessum, D.A. Paolella, S.E. Chambliss, J.S. Apte, 
J.D. Hill, J.D. Marshall, PM2.5 polluters 
disproportionately and systemically affect people of color in the 
United States. Sci. Adv. 7, eabf4491 (2021).
    \468\ http://www.cdc.gov/asthma/most_recent_data.htm.
    \469\ Arias, E. Xu, J. (2022) United States Life Tables, 2019. 
National Vital Statistics Report, Volume 70, Number 19. [Online at 
https://www.cdc.gov/nchs/data/nvsr/nvsr70/nvsr70-19.pdf].
---------------------------------------------------------------------------

    In addition, as discussed in Section II.B.7 of this document, 
concentrations of many air pollutants are elevated near high-traffic 
roadways, and populations who live, work, or go to school near high-
traffic roadways experience higher rates of numerous adverse health 
effects, compared to populations far away from major roads.
    EPA's analysis of environmental justice includes an examination of 
the populations living in close proximity to truck routes and to major 
roads more generally. This analysis, described in Section VII.H.1 of 
this document, finds that there is substantial evidence that people who 
live or attend school near major roadways are more likely to be people 
of color, Hispanic ethnicity, and/or low socioeconomic status. This 
final rule will reduce emissions that contribute to NO2 and 
other near-roadway pollution, improving air quality for the 72 million 
people who live near major truck routes and are already overburdened by 
air pollution from diesel emissions.
    Heavy-duty vehicles also contribute to regional concentrations of 
ozone and PM2.5. As described in Section VII.H.2 of this 
document, EPA used the air quality modeling data described in this 
Section VII to conduct a demographic analysis of human exposure to 
future air quality in scenarios with and without the rule in place. 
Although the spatial resolution of the air quality modeling is not 
sufficient to capture very local heterogeneity of human exposures, 
particularly the pollution concentration gradients near roads, the 
analysis does allow estimates of demographic trends at a national 
scale. The analysis indicates that the largest predicted improvements 
in both ozone and PM2.5 are estimated to occur in areas with 
the worst baseline air quality, and that a larger number of people of 
color are projected to reside in these areas.
1. Demographic Analysis of the Near-Road Population
    We conducted an analysis of the populations living in close 
proximity to truck freight routes as identified in USDOT's FAF4.\470\ 
FAF4 is a model from the USDOT's Bureau of Transportation Statistics 
(BTS) and Federal Highway Administration (FHWA), which provides data 
associated with freight movement in the United States.\471\ Relative to 
the rest of

[[Page 4423]]

the population, people living near FAF4 truck routes are more likely to 
be people of color and have lower incomes than the general population. 
People living near FAF4 truck routes are also more likely to live in 
metropolitan areas. Even controlling for region of the country, county 
characteristics, population density, and household structure, race, 
ethnicity, and income are significant determinants of whether someone 
lives near a FAF4 truck route. We note that we did not analyze the 
population living near warehousing, distribution centers, 
transshipment, ot intermodal freight facilities.
---------------------------------------------------------------------------

    \470\ U.S. EPA (2021). Estimation of Population Size and 
Demographic Characteristics among People Living Near Truck Routes in 
the Conterminous United States. Memorandum to the Docket.
    \471\ FAF4 includes data from the 2012 Commodity Flow Survey 
(CFS), the Census Bureau on international trade, as well as data 
associated with construction, agriculture, utilities, warehouses, 
and other industries. FAF4 estimates the modal choices for moving 
goods by trucks, trains, boats, and other types of freight modes. It 
includes traffic assignments, including truck flows on a network of 
truck routes. https://ops.fhwa.dot.gov/freight/freight_analysis/faf/
.
---------------------------------------------------------------------------

    We additionally analyzed national databases that allowed us to 
evaluate whether homes and schools were located near a major road and 
whether disparities in exposure may be occurring in these environments. 
Until 2009, the U.S. Census Bureau's American Housing Survey (AHS) 
included descriptive statistics of over 70,000 housing units across the 
nation and asked about transportation infrastructure near respondents' 
homes every two years.472 473 We also analyzed the U.S. 
Department of Education's Common Core of Data (CCD), which includes 
enrollment and location information for schools across the United 
States.\474\
---------------------------------------------------------------------------

    \472\ U.S. Department of Housing and Urban Development, & U.S. 
Census Bureau. (n.d.). Age of other residential buildings within 300 
feet. In American Housing Survey for the United States: 2009 (pp. A-
1). Retrieved from https://www.census.gov/programs-surveys/ahs/data/2009/ahs-2009-summary-tables0/h150-09.html.
    \473\ The 2013 AHS again included the ``etrans'' question about 
highways, airports, and railroads within half a block of the housing 
unit but has not maintained the question since then.
    \474\ http://nces.ed.gov/ccd/.
---------------------------------------------------------------------------

    In analyzing the 2009 AHS, we focused on whether a housing unit was 
located within 300 feet of a ``4-or-more lane highway, railroad, or 
airport'' (this distance was used in the AHS analysis).\475\ We 
analyzed whether there were differences between households in such 
locations compared with those in locations farther from these 
transportation facilities.\476\ We included other variables, such as 
land use category, region of country, and housing type. We found that 
homes with a non-White householder were 22-34 percent more likely to be 
located within 300 feet of these large transportation facilities than 
homes with White householders. Homes with a Hispanic householder were 
17-33 percent more likely to be located within 300 feet of these large 
transportation facilities than homes with non-Hispanic householders. 
Households near large transportation facilities were, on average, lower 
in income and educational attainment and more likely to be a rental 
property and located in an urban area compared with households more 
distant from transportation facilities.
---------------------------------------------------------------------------

    \475\ This variable primarily represents roadway proximity. 
According to the Central Intelligence Agency's World Factbook, in 
2010, the United States had 6,506,204 km of roadways, 224,792 km of 
railways, and 15,079 airports. Highways thus represent the 
overwhelming majority of transportation facilities described by this 
factor in the AHS.
    \476\ Bailey, C. (2011) Demographic and Social Patterns in 
Housing Units Near Large Highways and other Transportation Sources. 
Memorandum to docket.
---------------------------------------------------------------------------

    In examining schools near major roadways, we used the CCD from the 
U.S. Department of Education, which includes information on all public 
elementary and secondary schools and school districts nationwide.\477\ 
To determine school proximities to major roadways, we used a geographic 
information system (GIS) to map each school and roadways based on the 
U.S. Census's TIGER roadway file.\478\ We estimated that about 10 
million students attend schools within 200 meters of major roads, about 
20 percent of the total number of public school students in the United 
States.\479\ About 800,000 students attend public schools within 200 
meters of primary roads, or about 2 percent of the total. We found that 
students of color were overrepresented at schools within 200 meters of 
primary roadways, and schools within 200 meters of primary roadways had 
a disproportionate population of students eligible for free or reduced-
price lunches.\480\ Black students represent 22 percent of students at 
schools located within 200 meters of a primary road, compared to 17 
percent of students in all U.S. schools. Hispanic students represent 30 
percent of students at schools located within 200 meters of a primary 
road, compared to 22 percent of students in all U.S. schools.
---------------------------------------------------------------------------

    \477\ http://nces.ed.gov/ccd/.
    \478\ Pedde, M.; Bailey, C. (2011) Identification of Schools 
within 200 Meters of U.S. Primary and Secondary Roads. Memorandum to 
the docket.
    \479\ Here, ``major roads'' refer to those TIGER classifies as 
either ``Primary'' or ``Secondary.'' The Census Bureau describes 
primary roads as ``generally divided limited-access highways within 
the Federal interstate system or under state management.'' Secondary 
roads are ``main arteries, usually in the U.S. highway, state 
highway, or county highway system.''
    \480\ For this analysis we analyzed a 200-meter distance based 
on the understanding that roadways generally influence air quality 
within a few hundred meters from the vicinity of heavily traveled 
roadways or along corridors with significant trucking traffic. See 
U.S. EPA, 2014. Near Roadway Air Pollution and Health: Frequently 
Asked Questions. EPA-420-F-14-044.
---------------------------------------------------------------------------

    We also reviewed existing scholarly literature examining the 
potential for disproportionate exposure among people of color and 
people with low socioeconomic status (SES). Numerous studies evaluating 
the demographics and socioeconomic status of populations or schools 
near roadways have found that they include a greater percentage of 
residents of color, as well as lower SES populations (as indicated by 
variables such as median household income). Locations in these studies 
include Los Angeles, CA; Seattle, WA; Wayne County, MI; Orange County, 
FL; the State of California generally; and 
nationally.481 482 483 484 485 486 487 Such disparities may 
be due to multiple factors.488 489 490 491 492
---------------------------------------------------------------------------

    \481\ Marshall, J.D. (2008) Environmental inequality: air 
pollution exposures in California's South Coast Air Basin.
    \482\ Su, J.G.; Larson, T.; Gould, T.; Cohen, M.; Buzzelli, M. 
(2010) Transboundary air pollution and environmental justice: 
Vancouver and Seattle compared. GeoJournal 57: 595-608. doi:10.1007/
s10708-009-9269-6.
    \483\ Chakraborty, J.; Zandbergen, P.A. (2007) Children at risk: 
measuring racial/ethnic disparities in potential exposure to air 
pollution at school and home. J Epidemiol Community Health 61: 1074-
1079. doi:10.1136/jech.2006.054130.
    \484\ Green, R.S.; Smorodinsky, S.; Kim, J.J.; McLaughlin, R.; 
Ostro, B. (20042004) Proximity of California public schools to busy 
roads. Environ Health Perspect 112: 61-66. doi:10.1289/ehp.6566.
    \485\ Wu, Y.; Batterman, S.A. (2006) Proximity of schools in 
Detroit, Michigan to automobile and truck traffic. J Exposure Sci & 
Environ Epidemiol. doi:10.1038/sj.jes.7500484.
    \486\ Su, J.G.; Jerrett, M.; de Nazelle, A.; Wolch, J. (2011) 
Does exposure to air pollution in urban parks have socioeconomic, 
racial, or ethnic gradients? Environ Res 111: 319-328.
    \487\ Jones, M.R.; Diez-Roux, A.; Hajat, A.; et al. (2014) Race/
ethnicity, residential segregation, and exposure to ambient air 
pollution: The Multi-Ethnic Study of Atherosclerosis (MESA). Am J 
Public Health 104: 2130-2137. [Online at: https://doi.org/10.2105/AJPH.2014.302135].
    \488\ Depro, B.; Timmins, C. (2008) Mobility and environmental 
equity: do housing choices determine exposure to air pollution? Duke 
University Working Paper.
    \489\ Rothstein, R. The Color of Law: A Forgotten History of How 
Our Government Segregated America. New York: Liveright, 2018.
    \490\ Lane, H.J.; Morello-Frosch, R.; Marshall, J.D.; Apte, J.S. 
(2022) Historical redlining is associated with present-day air 
pollution disparities in US Cities. Environ Sci & Technol Letters 9: 
345-350. DOI: [Online at: https://doi.org/10.1021/acs.estlett.1c01012].
    \491\ Ware, L. (2021) Plessy's legacy: the government's role in 
the development and perpetuation of segregated neighborhoods. RSF: 
The Russel Sage Foundation Journal of the Social Sciences, 7:92-109. 
DOI: DOI: 10.7758/RSF.2021.7.1.06.
    \492\ Archer, D.N. (2020) ``White Men's Roads through Black 
Men's Homes'': advancing racial equity through highway 
reconstruction. Vanderbilt Law Rev 73: 1259.
---------------------------------------------------------------------------

    People with low SES often live in neighborhoods with multiple 
stressors

[[Page 4424]]

and health risk factors, including reduced health insurance coverage 
rates, higher smoking and drug use rates, limited access to fresh food, 
visible neighborhood violence, and elevated rates of obesity and some 
diseases such as asthma, diabetes, and ischemic heart disease. Although 
questions remain, several studies find stronger associations between 
air pollution and health in locations with such chronic neighborhood 
stress, suggesting that populations in these areas may be more 
susceptible to the effects of air pollution.493 494 495 496
---------------------------------------------------------------------------

    \493\ Clougherty, J.E.; Kubzansky, L.D. (2009) A framework for 
examining social stress and susceptibility to air pollution in 
respiratory health. Environ Health Perspect 117: 1351-1358. 
Doi:10.1289/ehp.0900612.
    \494\ Clougherty, J.E.; Levy, J.I.; Kubzansky, L.D.; Ryan, P.B.; 
Franco Suglia, S.; Jacobson Canner, M.; Wright, R.J. (2007) 
Synergistic effects of traffic-related air pollution and exposure to 
violence on urban asthma etiology. Environ Health Perspect 115: 
1140-1146. doi:10.1289/ehp.9863.
    \495\ Finkelstein, M.M.; Jerrett, M.; DeLuca, P.; Finkelstein, 
N.; Verma, D.K.; Chapman, K.; Sears, M.R. (2003) Relation between 
income, air pollution and mortality: a cohort study. Canadian Med 
Assn J 169: 397-402.
    \496\ Shankardass, K.; McConnell, R.; Jerrett, M.; Milam, J.; 
Richardson, J.; Berhane, K. (2009) Parental stress increases the 
effect of traffic-related air pollution on childhood asthma 
incidence. Proc Natl Acad Sci 106: 12406-12411. doi:10.1073/
pnas.0812910106.
---------------------------------------------------------------------------

    Several publications report nationwide analyses that compare the 
demographic patterns of people who do or do not live near major 
roadways.497 498 499 500 501 502 Three of these studies 
found that people living near major roadways are more likely to be 
people of color or low in SES.503 504 505 They also found 
that the outcomes of their analyses varied between regions within the 
United States. However, only one such study looked at whether such 
conclusions were confounded by living in a location with higher 
population density and how demographics differ between locations 
nationwide.\506\ In general, it found that higher density areas have 
higher proportions of low-income residents and people of color. In 
other publications based on a city, county, or state, the results are 
similar.507 508
---------------------------------------------------------------------------

    \497\ Rowangould, G.M. (2013) A census of the U.S. near-roadway 
population: public health and environmental justice considerations. 
Transportation Research Part D; 59-67.
    \498\ Tian, N.; Xue, J.; Barzyk. T.M. (2013) Evaluating 
socioeconomic and racial differences in traffic-related metrics in 
the United States using a GIS approach. J Exposure Sci Environ 
Epidemiol 23: 215-222.
    \499\ CDC (2013) Residential proximity to major highways--United 
States, 2010. Morbidity and Mortality Weekly Report 62(3): 46-50.
    \500\ Clark, L.P.; Millet, D.B., Marshall, J.D. (2017) Changes 
in transportation-related air pollution exposures by race-ethnicity 
and socioeconomic status: outdoor nitrogen dioxide in the United 
States in 2000 and 2010. Environ Health Perspect https://doi.org/10.1289/EHP959.
    \501\ Mikati, I.; Benson, A.F.; Luben, T.J.; Sacks, J.D.; 
Richmond-Bryant, J. (2018) Disparities in distribution of 
particulate matter emission sources by race and poverty status. Am J 
Pub Health https://ajph.aphapublications.org/doi/abs/10.2105/AJPH.2017.304297?journalCode=ajph.
    \502\ Alotaibi, R.; Bechle, M.; Marshall, J.D.; Ramani, T.; 
Zietsman, J.; Nieuwenhuijsen, M.J.; Khreis, H. (2019) Traffic 
related air pollution and the burden of childhood asthma in the 
continuous United States in 2000 and 2010. Environ International 
127: 858-867. https://www.sciencedirect.com/science/article/pii/S0160412018325388.
    \503\ Tian, N.; Xue, J.; Barzyk. T.M. (2013) Evaluating 
socioeconomic and racial differences in traffic-related metrics in 
the United States using a GIS approach. J Exposure Sci Environ 
Epidemiol 23: 215-222.
    \504\ Rowangould, G.M. (2013) A census of the U.S. near-roadway 
population: public health and environmental justice considerations. 
Transportation Research Part D; 59-67.
    \505\ CDC (2013) Residential proximity to major highways--United 
States, 2010. Morbidity and Mortality Weekly Report 62(3): 46-50.
    \506\ Rowangould, G.M. (2013) A census of the U.S. near-roadway 
population: public health and environmental justice considerations. 
Transportation Research Part D; 59-67.
    \507\ Pratt, G.C.; Vadali, M.L.; Kvale, D.L.; Ellickson, K.M. 
(2015) Traffic, air pollution, minority, and socio-economic status: 
addressing inequities in exposure and risk. Int J Environ Res Public 
Health 12: 5355-5372. http://dx.doi.org/10.3390/ijerph120505355.
    \508\ Sohrabi, S.; Zietsman, J.; Khreis, H. (2020) Burden of 
disease assessment of ambient air pollution and premature mortality 
in urban areas: the role of socioeconomic status and transportation. 
Int J Env Res Public Health doi:10.3390/ijerph17041166.
---------------------------------------------------------------------------

    Two recent studies provide strong evidence that reducing emissions 
from heavy-duty vehicles is extremely likely to reduce the disparity in 
exposures to traffic-related air pollutants, both using NO2 
observations from the recently launched TROPospheric Ozone Monitoring 
Instrument (TROPOMI) satellite sensor as a measure of air quality, 
which provides the highest-resolution observations heretofore 
unavailable from any satellite.\509\
---------------------------------------------------------------------------

    \509\ TROPospheric Ozone Monitoring Instrument (TROPOMI) is part 
of the Copernicus Sentinel-5 Precursor satellite.
---------------------------------------------------------------------------

    One study evaluated satellite NO2 concentrations during 
the COVID-19 lockdowns in 2020 and compared them to NO2 
concentrations from the same dates in 2019.\510\ That study found that 
average NO2 concentrations were highest in areas with the 
lowest percentage of White populations, and that the areas with the 
greatest percentages of non-White or Hispanic populations experienced 
the greatest declines in NO2 concentrations during the 
lockdown. These NO2 reductions were associated with the 
density of highways in the local area.
---------------------------------------------------------------------------

    \510\ Kerr, G.H.; Goldberg, D.L.; Anenberg, S.C. (2021) COVID-19 
pandemic reveals persistent disparities in nitrogen dioxide 
pollution. PNAS 118. [Online at https://doi.org/10.1073/pnas.2022409118].
---------------------------------------------------------------------------

    In the second study, satellite NO2 measured from 2018-
2020 was averaged by racial groups and income levels in 52 large U.S. 
cities.\511\ Using census tract-level NO2, the study 
reported average population-weighted NO2 levels to be 28 
percent higher for low-income non-White people compared with high-
income White people. The study also used weekday-weekend differences 
and bottom-up emission estimates to estimate that diesel traffic is the 
dominant source of NO2 disparities in the studied cities. 
Overall, there is substantial evidence that people who live or attend 
school near major roadways are more likely to be of a non-White race, 
Hispanic, and/or have a low SES. Although proximity to an emissions 
source is an indicator of potential exposure, it is important to note 
that the impacts of emissions from tailpipe sources are not limited to 
communities in close proximity to these sources. For example, the 
effects of potential decreases in emissions from sources affected by 
this final rule might also be felt many miles away, including in 
communities with EJ concerns. The spatial extent of these impacts 
depends on a range of interacting and complex factors including the 
amount of pollutant emitted, atmospheric lifetime of the pollutant, 
terrain, atmospheric chemistry and meteorology. However, recent studies 
using satellite-based NO2 measurements provide evidence that 
reducing emission from heavy-duty vehicles is likely to reduce 
disparities in exposure to traffic-related pollution.
---------------------------------------------------------------------------

    \511\ Demetillo, M.A.; Harkins, C.; McDonald, B.C.; et al. 
(2021) Space-based observational constraints on NO2 air 
pollution inequality from diesel traffic in major US cities. Geophys 
Res Lett 48, e2021GL094333. [Online at https://doi.org/10.1029/2021GL094333].
---------------------------------------------------------------------------

2. Demographic Analysis of Ozone and PM2.5 Impacts
    When feasible, EPA's Office of Transportation and Air Quality 
conducts full-scale photochemical air quality modeling to demonstrate 
how its national mobile source regulatory actions affect ambient 
concentrations of regional pollutants throughout the United States. As 
described in RIA Chapter 6.2, the air quality modeling we conducted for 
the proposal also supports our analysis of future projections of 
PM2.5 and ozone concentrations in a ``baseline'' scenario 
absent the rule and in a ``control''

[[Page 4425]]

scenario that assumes the rule is in place.\512\
---------------------------------------------------------------------------

    \512\ Air quality modeling was performed for the proposed rule, 
which used emission reductions that are very similar to the emission 
reductions projected for the final rule. Given the similar structure 
of the proposed and final programs, we expect consistent geographic 
distribution of emissions reductions and modeled improvements in air 
quality, and that the air quality modeling conducted at the time of 
proposal adequately represents the final rule. Specifically, we 
expect this rule will decrease ambient concentrations of air 
pollutants, including significant improvements in ozone 
concentrations in 2045 as demonstrated in the air quality modeling 
analysis.
---------------------------------------------------------------------------

    This air quality modeling data can also be used to conduct a 
demographic analysis of human exposure to future air quality in 
scenarios with and without the rule in place. Although the spatial 
resolution of the air quality modeling is not sufficient to capture 
very local heterogeneity of human exposures, particularly the pollution 
concentration gradients near roads, the analysis does allow estimates 
of demographic trends at a national scale. We developed this approach 
by considering the purpose and specific characteristics of this 
rulemaking, as well as the nature of known and potential exposures to 
the air pollutants controlled by the standards. The heavy-duty 
standards apply nationally and will be implemented consistently across 
roadways throughout the United States. The pollutant predominantly 
controlled by the standard is NOX. Reducing emissions of 
NOX will reduce formation of ozone and secondarily formed 
PM2.5, which will reduce human exposures to regional 
concentrations of ambient ozone and PM2.5. These reductions 
will be geographically widespread. Taking these factors into 
consideration, this demographic analysis evaluates the exposure outcome 
distributions that will result from this rule at the national scale 
with a focus on locations that are projected to have the highest 
baseline concentrations of PM2.5 and ozone.
    To analyze trends in exposure outcomes, we sorted projected 2045 
baseline air quality concentrations from highest to lowest 
concentration and created two groups: Areas within the contiguous 
United States with the worst air quality (highest 5 percent of 
concentrations) and the rest of the country. This approach can then 
answer two principal questions to determine disparity among people of 
color:
    1. What is the demographic composition of areas with the worst 
baseline air quality in 2045?
    2. Are those with the worst air quality benefiting more from the 
heavy-duty vehicle and engine standards?
    We found that in the 2045 baseline, the number of people of color 
projected to live within the grid cells with the highest baseline 
concentrations of ozone (26 million) is nearly double that of non-
Hispanic Whites (14 million). Thirteen percent of people of color are 
projected to live in areas with the worst baseline ozone, compared to 
seven percent of non-Hispanic Whites. The number of people of color 
projected to live within the grid cells with the highest baseline 
concentrations of PM2.5 (93 million) is nearly double that 
of non-Hispanic Whites (51 million). Forty-six percent of people of 
color are projected to live in areas with the worst baseline 
PM2.5, compared to 25 percent of non-Hispanic Whites. We 
also found that the largest predicted improvements in both ozone and 
PM2.5 are estimated to occur in areas with the worst 
baseline air quality, and that a larger number of people of color are 
projected to reside in these areas.
    EPA received comments related to the methods the Agency used to 
analyze the distribution of impacts of the heavy-duty vehicle and 
engine standards. We summarize and respond to those comments in the 
Response to Comments document that accompanies this rulemaking. After 
consideration of comments, we have retained our approach used in the 
proposal for this final rule. However, after considering comments that 
EPA undertake an analysis of race/ethnicity-stratified impacts, we have 
added an analysis of the demographic composition of air quality impacts 
that accrue to specific race and ethnic groups. The result of that 
analysis found that non-Hispanic Blacks will experience the greatest 
reductions in PM2.5 and ozone concentrations as a result of 
the standards. Chapter 6.6.9 of the RIA describes the data and methods 
used to conduct the demographic analysis and presents our results in 
detail.

VIII. Benefits of the Heavy-Duty Engine and Vehicle Standards

    The highway heavy-duty engines and vehicles subject to the final 
rule are significant sources of mobile source air pollution, including 
directly-emitted PM2.5 as well as NOX and VOC 
emissions (both precursors to ozone formation and secondarily-formed 
PM2.5). The final program will reduce exhaust emissions of 
these pollutants from the regulated engines and vehicles, which will in 
turn reduce ambient concentrations of ozone and PM2.5, as 
discussed in Sections VI and VII. Exposures to these pollutants are 
linked to adverse environmental and human health impacts, such as 
premature deaths and non-fatal illnesses (see Section II).
    In this section, we present the quantified and monetized human 
health benefits from reducing concentrations of ozone and 
PM2.5 using the air quality modeling results described in 
Section VII. As noted in Section VII, we performed full-scale 
photochemical air quality modeling for the proposal. No further air 
quality modeling has been conducted to reflect the emissions impacts of 
the final program. Because air quality modeling results are necessary 
to quantify estimates of avoided mortality and illness attributable to 
changes in ambient PM2.5 and ozone, we present the benefits 
from the proposal as a proxy for the health benefits associated with 
the final program. RIA Chapter 5 describes the differences in emissions 
between those used to estimate the air quality impacts of the proposal 
and those that will be achieved by the final program. Emission 
reductions associated with the final program are similar to those used 
in the air quality modeling conducted for the proposal. We therefore 
conclude that the health benefits from the proposal are a fair 
characterization of those that will be achieved due to the substantial 
improvements in air quality attributable to the final program.
    The approach we used to estimate health benefits is consistent with 
the approach described in the technical support document (TSD) that was 
published for the final Revised Cross-State Air Pollution Rule (CSAPR) 
Update RIA.\513\ Table VIII-1 and Table VIII-2 present quantified 
health benefits from reductions in human exposure to ambient 
PM2.5 and ozone, respectively, in 2045. Table VIII-3 
presents the total monetized benefits attributable to the final rule in 
2045. We estimate that in 2045, the annual monetized benefits are $12 
and $33 billion at a 3 percent discount rate and $10 and $30 billion at 
a 7 percent discount rate (2017 dollars).
---------------------------------------------------------------------------

    \513\ U.S. Environmental Protection Agency (U.S. EPA). 2021. 
Estimating PM2.5- and Ozone-Attributable Health Benefits. 
Technical Support Document (TSD) for the Final Revised Cross-State 
Air Pollution Rule Update for the 2008 Ozone Season NAAQS. EPA-HQ-
OAR-2020-0272. March.
---------------------------------------------------------------------------

    There are additional human health and environmental benefits 
associated with reductions in exposure to ambient concentrations of 
PM2.5, ozone, and NO2 that EPA has not quantified 
due to data, resource, or methodological limitations. There are also 
benefits associated with reductions in air toxic pollutant emissions 
that result from the final standards, but EPA is not currently able to 
monetize those impacts due to methodological limitations. The estimated 
benefits of this rule would be

[[Page 4426]]

larger if we were able to monetize all unquantified benefits at this 
time.
    EPA received several comments related to the methods the Agency 
used to estimate the benefits of the proposal. We summarize and respond 
to those comments in the Response to Comments document that accompanies 
this rulemaking. After consideration of comments, we have retained our 
approach to estimating benefits and have not made any changes to the 
analysis. For more detailed information about the benefits analysis 
conducted for this rule, please refer to RIA Chapter 8 that accompanies 
this preamble.

 Table VIII-1--Estimated Avoided PM2.5 Mortality and Illnesses for 2045
                  [95 Percent confidence interval] \ab\
------------------------------------------------------------------------
                                                      Avoided health
                                                         incidence
------------------------------------------------------------------------
Avoided premature mortality:
    Turner et al. (2016)--Ages 30+..............  740 (500 to 980).
    Di et al. (2017)--Ages 65+..................  800 (780 to 830).
    Woodruff et al. (2008)--Ages <1.............  4.1 (-2.6 to 11).
Non-fatal heart attacks among adults:
    Short-term exposure:
        Peters et al. (2001)....................  790 (180 to 1,400).
        Pooled estimate.........................  85 (31 to 230).
Morbidity effects:
    Long-term exposure:
        Asthma onset............................  1,600 (1,500 to
                                                   1,600).
        Allergic rhinitis symptoms..............  10,000 (2,500 to
                                                   18,000)
        Stroke..................................  41 (11 to 70).
        Lung cancer.............................  52 (16 to 86).
        Hospital Admissions--Alzheimer's disease  400 (300 to 500).
        Hospital Admissions--Parkinson's disease  43 (22 to 63).
    Short-term exposure:
        Hospital admissions--cardiovascular.....  110 (76 to 130).
        ED visits--cardiovascular...............  210 (-82 to 500).
        Hospital admissions--respiratory........  68 (23 to 110).
        ED visits--respiratory..................  400 (78 to 830).
        Asthma symptoms.........................  210,000 (-100,000 to
                                                   520,000).
        Minor restricted-activity days..........  460,000 (370,000 to
                                                   550,000).
        Cardiac arrest..........................  10 (-4.2 to 24).
        Lost work days..........................  78,000 (66,000 to
                                                   90,000).
------------------------------------------------------------------------
\a\ Values rounded to two significant figures.
\b\ PM2.5 exposure metrics are not presented here because all PM health
  endpoints are based on studies that used daily 24-hour average
  concentrations. Annual exposures are estimated using daily 24-hour
  average concentrations.

 Table VIII-2--Estimated Avoided Ozone Mortality and Illnesses for 2045
                  [95 Percent confidence interval] \a\
------------------------------------------------------------------------
                                   Metric and season    Avoided health
                                          \b\              incidence
------------------------------------------------------------------------
Avoided premature mortality:
    Long-term exposure:
        Turner et al. (2016)....  MDA8; April-        2,100 (1,400 to
                                   September.          2,700).
    Short-term exposure:
        Katsouyanni et al.        MDA1; April-        120 (-69 to 300).
         (2009).                   September.
Morbidity effects:
    Long-term exposure:
        Asthma onset \c\........  MDA8; June-August.  16,000 (14,000 to
                                                       18,000).
    Short-term exposure:
        Allergic rhinitis         MDA8; May-          88,000 (47,000 to
         symptoms.                 September.          130,000).
        Hospital admissions--     MDA1; April-        350 (-91 to 770).
         respiratory.              September.
        ED visits--respiratory..  MDA8; May-          5,100 (1,400 to
                                   September.          11,000).
        Asthma symptoms--Cough    MDA8; May-          920,000 (-50,000
         \d\.                      September.          to 1,800,000).
        Asthma symptoms--Chest    MDA8; May-          770,000 (85,000 to
         Tightness \d\.            September.          1,400,000).
        Asthma symptoms--         MDA8; May-          390,000 (-330,000
         Shortness of Breath \d\.  September.          to 1,100,000).
        Asthma symptoms--Wheeze   MDA8; May-          730,000 (-57,000
         \d\.                      September.          to 1,500,000).
        Minor restricted-         MDA1; May-          1,600,000 (650,000
         activity days \d\.        September.          to 2,600,000).
        School absence days.....  MDA8; May-          1,100,000 (-
                                   September.          150,000 to
                                                       2,200,000).
------------------------------------------------------------------------
\a\ Values rounded to two significant figures.
\b\ MDA8--maximum daily 8-hour average; MDA1--maximum daily 1-hour
  average. Studies of ozone vary with regards to season, limiting
  analyses to various definitions of summer (e.g., April-September, May-
  September or June-August). These differences can reflect state-
  specific ozone seasons, EPA-defined seasons or another seasonal
  definition chosen by the study author. The paucity of ozone monitoring
  data in winter months complicates the development of full year
  projected ozone surfaces and limits our analysis to only warm seasons.
\c\ The underlying metric associated with this risk estimate is daily 8-
  hour average from 10 a.m.-6 p.m. (AVG8); however, we ran the study
  with a risk estimate converted to MDA8.
\d\ Applied risk estimate derived from full year exposures to estimates
  of ozone across a May-September ozone season. When risk estimates
  based on full-year, long-term ozone exposures are applied to warm
  season air quality projections, the resulting benefits assessment may
  underestimate impacts, due to a shorter timespan for impacts to
  accrue.

[[Page 4427]]

                        Table VIII-3--Total Ozone and PM2.5-Attributable Benefits in 2045
                            [95 Percent confidence interval; billions of 2017$] \a b\
----------------------------------------------------------------------------------------------------------------
 
----------------------------------------------------------------------------------------------------------------
                                                                          Total annual benefits in 2045
----------------------------------------------------------------------------------------------------------------
3% Discount Rate..............................................                 $12      and                 $33
                                                                ($0.72 to $31) \c\            ($3.5 to $87) \d\
7% Discount Rate..............................................                 $10      and                 $30
                                                                ($0.37 to $28) \c\            ($3.0 to $78) \d\
----------------------------------------------------------------------------------------------------------------
\a\ The benefits associated with the standards presented here do not include the full complement of health and
  environmental benefits that, if quantified and monetized, would increase the total monetized benefits.
\b\ Values rounded to two significant figures. The two benefits estimates separated by the word ``and'' signify
  that they are two separate estimates. The estimates do not represent lower- and upper-bound estimates though
  they do reflect a grouping of estimates that yield more and less conservative benefit totals. They should not
  be summed.
\c\ Sum of benefits using the Katsouyanni et al. (2009) short-term exposure ozone respiratory mortality risk
  estimate and the Turner et al. (2016) long-term exposure PM2.5 all-cause risk estimate.
\d\ Sum of benefits using the Turner et al. (2016) long-term exposure ozone respiratory mortality risk estimate
  and the Di et al. (2017) long-term exposure PM2.5 all-cause risk estimate.

    The full-scale criteria pollutant benefits analysis that was 
conducted for the proposal, and is presented here, reflects spatially 
and temporally allocated emissions inventories (see RIA Chapter 5), 
photochemical air quality modeling (see RIA Chapter 6), and 
PM2.5 and ozone benefits generated using EPA's Environmental 
Benefits Mapping and Analysis Program--Community Edition (BenMAP-CE) 
(see RIA Chapter 8),\514\ all for conditions projected to occur in 
calendar year 2045. As we presented in Sections V and VI, national 
estimates of program costs and emissions were generated for each 
analysis year from the final rule's implementation to a year when the 
final rule will be fully phased-in and the vehicle fleet is approaching 
full turnover (2027-2045). The computational requirements needed to 
conduct photochemical air quality modeling to support a full-scale 
benefits analysis for analysis years from 2027 to 2044 precluded the 
Agency from conducting benefits analyses comparable to the proposal's 
benefits analysis for calendar year 2045. Instead, we use a reduced-
form approach to scale total benefits in 2045 back to 2027 using 
projected reductions in year-over-year NOX emissions so we 
can estimate the present and annualized values of the stream of 
estimated benefits for the final rule.\515\ For more information on the 
benefits scaling approach we applied to estimate criteria pollutant 
benefits over time, please refer to RIA Chapter 8.6 that accompanies 
this preamble.
---------------------------------------------------------------------------

    \514\ BenMAP-CE is an open-source computer program that 
calculates the number and economic value of air pollution-related 
deaths and illnesses. The software incorporates a database that 
includes many of the concentration-response relationships, 
population files, and health and economic data needed to quantify 
these impacts. More information about BenMAP-CE, including 
downloadable versions of the tool and associated user manuals, can 
be found at EPA's website www.epa.gov/benmap.
    \515\ Because NOX is the dominant pollutant 
controlled by the final rule, we make a simplifying assumption that 
total PM and ozone benefits can be scaled by NOX 
emissions, even though emissions of other pollutants are controlled 
in smaller amounts by the final rule.
---------------------------------------------------------------------------

    Table VIII-4 and Table VIII-5 present the annual, estimated 
undiscounted total health benefits (PM2.5 plus ozone) for 
the stream of years beginning with the first year of rule 
implementation, 2027, through 2045. The tables also display the present 
and annualized values of benefits over this time series, discounted 
using both 3 percent and 7 percent discount rates and reported in 2017 
dollars. Table VIII-4 presents total benefits as the sum of short-term 
ozone respiratory mortality benefits for all ages, long-term 
PM2.5 all-cause mortality benefits for ages 30 and above, 
and all monetized avoided illnesses. Table VIII-5 presents total 
benefits as the sum of long-term ozone respiratory mortality benefits 
for ages 30 and above, long-term PM2.5 all-cause mortality 
benefits for ages 65 and above, and all monetized avoided illnesses.

   Table VIII-4--Undiscounted Stream and Present Value of Human Health
Benefits From 2027 Through 2045: Monetized Benefits Quantified as Sum of
  Short-Term Ozone Respiratory Mortality Ages 0-99, and Long-Term PM2.5
                      All-Cause Mortality Ages 30+
     [Discounted at 3 percent and 7 percent; billions of 2017$] a b
------------------------------------------------------------------------
                                                Monetized benefits
                                         -------------------------------
                                            3% Discount     7% Discount
                                               rate            rate
------------------------------------------------------------------------
2027....................................           $0.66           $0.59
2028....................................             1.4             1.2
2029....................................             2.1             1.9
2030....................................             2.8             2.6
2031....................................             3.8             3.4
2032....................................             4.8             4.3
2033....................................             5.5             5.0
2034....................................             6.2             5.6
2035....................................             6.9             6.2
2036....................................             7.5             6.7
2037....................................             8.0             7.2
2038....................................             8.6             7.7
2039....................................             9.1             8.2
2040....................................             9.6             8.7

[[Page 4428]]

 
2041....................................              10             9.0
2042....................................              10             9.4
2043....................................              11             9.7
2044....................................              11              10
2045 \c\................................              12              10
Present Value...........................              91              53
Annualized Value........................             6.3             5.1
------------------------------------------------------------------------
\a\ The benefits associated with the standards presented here do not
  include the full complement of health and environmental benefits that,
  if quantified and monetized, would increase the total monetized
  benefits.
\b\ Benefits calculated as value of avoided: PM2.5-attributable deaths
  (quantified using a concentration-response relationship from the
  Turner et al. 2016 study); Ozone-attributable deaths (quantified using
  a concentration-response relationship from the Katsouyanni et al. 2009
  study); and PM2.5 and ozone-related morbidity effects.
\c\ Year in which PM2.5 and ozone air quality was simulated (2045).

   Table VIII-5--Undiscounted Stream and Present Value of Human Health
Benefits From 2027 Through 2045: Monetized Benefits Quantified as Sum of
Long-Term Ozone Respiratory Mortality Ages 30+, and Long-Term PM2.5 All-
                        Cause Mortality Ages 65+
     [Discounted at 3 percent and 7 percent; billions of 2017$] a b
------------------------------------------------------------------------
                                                Monetized benefits
                                         -------------------------------
                                            3% Discount     7% Discount
                                               rate            rate
------------------------------------------------------------------------
2027....................................            $1.8            $1.6
2028....................................             3.7             3.3
2029....................................             5.7             5.1
2030....................................             7.9             7.1
2031....................................              11             9.6
2032....................................              13              12
2033....................................              16              14
2034....................................              18              16
2035....................................              19              17
2036....................................              21              19
2037....................................              23              21
2038....................................              25              22
2039....................................              26              23
2040....................................              28              25
2041....................................              29              26
2042....................................              30              27
2043....................................              31              28
2044....................................              32              29
2045 \c\................................              33              30
Present Value...........................             260             150
Annualized Value........................              18              14
------------------------------------------------------------------------
\a\ The benefits associated with the standards presented here do not
  include the full complement of health and environmental benefits that,
  if quantified and monetized, would increase the total monetized
  benefits.
\b\ Benefits calculated as value of avoided: PM2.5-attributable deaths
  (quantified using a concentration-response relationship from the Di et
  al. 2017 study); Ozone-attributable deaths (quantified using a
  concentration-response relationship from the Turner et al. 2016
  study); and PM2.5 and ozone-related morbidity effects.
\c\ Year in which PM2.5 and ozone air quality was simulated (2045).

    This analysis includes many data sources as inputs that are each 
subject to uncertainty. Input parameters include projected emission 
inventories, air quality data from models (with their associated 
parameters and inputs), population data, population estimates, health 
effect estimates from epidemiology studies, economic data, and 
assumptions regarding the future state of the world (i.e., regulations, 
technology, and human behavior). When compounded, even small 
uncertainties can greatly influence the size of the total quantified 
benefits. Please refer to RIA Chapter 8 for more information on the 
uncertainty associated with the benefits presented here.

IX. Comparison of Benefits and Costs

    This section compares the estimated range of total monetized health 
benefits to total costs associated with the final rule. This section 
also presents the range of monetized net benefits (benefits minus 
costs) associated with the final rule. Program costs are detailed and 
presented in Section V of this preamble.

[[Page 4429]]

Those costs include costs for both the new technology and the operating 
costs associated with that new technology, as well as costs associated 
with the final rule's warranty and useful life provisions. Program 
benefits are presented in Section VIII. Those benefits are the 
monetized economic value of the reduction in PM2.5- and 
ozone-related premature deaths and illnesses that result from 
reductions in NOX emissions and directly emitted 
PM2.5 attributable to implementation of the final rule.
    As noted in Section II and Sections V through VIII, these estimated 
benefits, costs, and net benefits do not reflect all the anticipated 
impacts of the final rule.516 517
---------------------------------------------------------------------------

    \516\ As detailed in RIA Chapter 8, estimates of health benefits 
are based on air quality modeling conducted for the proposal, and 
thus differences between the proposal and final rule are not 
reflected in the benefits analysis. We have concluded, however, that 
the health benefits estimated for the proposal are a fair 
characterization of the benefits that will be achieved due to the 
substantial improvements in air quality attributable to the final 
rule.
    \517\ EPA's analysis of costs and benefits does not include 
California's Omnibus rule or actions by other states to adopt it. 
EPA is reviewing a waiver request under CAA section 209(b) from 
California for the Omnibus rule; until EPA grants the waiver, the HD 
Omnibus program is not enforceable.
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A. Methods

    EPA presents three different benefit-cost comparisons for the final 
rule:
    1. A future-year snapshot comparison of annual benefits and costs 
in the year 2045, chosen to approximate the annual health benefits that 
will occur in a year when the program will be fully implemented and 
when most of the regulated fleet will have turned over. Benefits, costs 
and net benefits are presented in year 2017 dollars and are not 
discounted. However, 3 percent and 7 percent discount rates were 
applied in the valuation of avoided premature deaths from long-term 
pollution exposure to account for a twenty-year segmented cessation 
lag.
    2. The present value (PV) of the stream of benefits, costs and net 
benefits calculated for the years 2027-2045, discounted back to the 
first year of implementation of the final rule (2027) using both a 3 
percent and 7 percent discount rate, and presented in year 2017 
dollars. Note that year-over-year costs are presented in Section V and 
year-over-year benefits can be found in Section VIII.
    3. The equivalent annualized value (EAV) of benefits, costs and net 
benefits representing a flow of constant annual values that, had they 
occurred in each year from 2027 to 2045, will yield an equivalent 
present value to the present value estimated in method 2 (using either 
a 3 percent or 7 percent discount rate). Each EAV represents a typical 
benefit, cost or net benefit for each year of the analysis and is 
presented in year 2017 dollars.
    The two estimates of monetized benefits (and net benefits) in each 
of these benefit-cost comparisons reflect alternative combinations of 
the economic value of PM2.5- and ozone-related premature 
deaths summed with the economic value of illnesses for each discount 
rate (see RIA Chapter 8 for more detail).

B. Results

    Table IX-1 presents the benefits, costs and net benefits of the 
final rule in annual terms for year 2045, in PV terms, and in EAV 
terms.

 Table IX-1--Annual Value, Present Value and Equivalent Annualized Value
          of Costs, Benefits and Net Benefits of the Final Rule
                          [billions, 2017$] a b
------------------------------------------------------------------------
                                            3% Discount     7% Discount
------------------------------------------------------------------------
2045:
    Benefits............................         $12-$33         $10-$30
    Costs...............................             4.7             4.7
    Net Benefits........................          6.9-29          5.8-25
Present Value:
    Benefits............................          91-260          53-150
    Costs...............................              55              39
    Net Benefits........................          36-200          14-110
Equivalent Annualized Value:
    Benefits............................          6.3-18          5.1-14
    Costs...............................             3.8             3.8
    Net Benefits........................          2.5-14          1.3-11
------------------------------------------------------------------------
\a\ All benefits estimates are rounded to two significant figures;
  numbers may not sum due to independent rounding. The range of benefits
  (and net benefits) in this table are two separate estimates and do not
  represent lower- and upper-bound estimates, though they do reflect a
  grouping of estimates that yield more and less conservative benefits
  totals. The costs and benefits in 2045 are presented in annual terms
  and are not discounted. However, all benefits in the table reflect a 3
  percent and 7 percent discount rate used to account for cessation lag
  in the valuation of avoided premature deaths associated with long-term
  exposure.
\b\ The benefits associated with the standards presented here do not
  include the full complement of health and environmental benefits that,
  if quantified and monetized, would increase the total monetized
  benefits.

    Annual benefits are larger than the annual costs in 2045, with 
annual net benefits of $5.8 and $25 billion using a 7 percent discount 
rate, and $6.9 and $29 billion using a 3 percent discount rate.\518\ 
Benefits also outweigh the costs when expressed in PV terms (net 
benefits of $14 and $110 billion using a 7 percent discount rate, and 
$36 and $200 billion using a 3 percent discount rate) and EAV terms 
(net benefits of $1.3 and $11 billion using a 7 percent discount rate, 
and $2.5 and $14 billion using a 3 percent discount rate).
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    \518\ The range of benefits and net benefits presented in this 
section reflect a combination of assumed PM2.5 and ozone 
mortality risk estimates and selected discount rate.
---------------------------------------------------------------------------

    Given these results, implementation of the final rule will provide 
society with a substantial net gain in welfare, notwithstanding the 
health and other benefits we were unable to quantify (see RIA Chapter 
8.7 for more information about unquantified benefits). EPA does not 
expect the omission of unquantified benefits to impact the Agency's 
evaluation of the costs and benefits of the final rule, though net 
benefits would be larger if unquantified benefits were monetized.

X. Economic Impact Analysis

    This section describes our Economic Impact Analysis for the final 
rule. Our analysis focuses on the potential impacts of the standards on 
heavy-duty

[[Page 4430]]

(HD) vehicles (sales, mode shift, fleet turnover) and employment in the 
HD industry. This section describes our evaluation.

A. Impact on Vehicle Sales, Mode Shift, and Fleet Turnover

    This final rulemaking will require HD engine manufacturers to 
develop and implement emission control technologies capable of 
controlling NOX at lower levels over longer emission 
warranty and regulatory useful life periods. These changes in 
requirements will increase the cost of producing and selling compliant 
HD vehicles. These increased costs are likely to lead to increases in 
prices for HD vehicles, which might lead to reductions in truck sales. 
In addition, there may be a period of ``pre-buying'' in anticipation of 
potentially higher prices, during which there is an increase in new 
vehicle purchases before the implementation of new requirements, 
followed by a period of ``low-buying'' directly after implementation, 
during which new vehicle purchases decrease. EPA acknowledges that the 
final rule may lead to some pre-buy before the implementation date of 
the standards, and some low-buy after the standards are implemented. 
EPA is unable to estimate sales impacts based on existing literature, 
and as such contracted with ERG to complete a literature review, as 
well as conduct original research to estimate sales impacts for 
previous EPA HD vehicle rules on pre- and low-buy for HD vehicles. The 
resulting analysis examines the effect of four HD truck regulations, 
those that became effective in 2004, 2007, 2010 and 2014, on the sales 
of Class 6, 7 and 8 vehicles over the twelve months before and after 
each standard. The rules with implementation dates in 2004, 2007 and 
2010 focused on reducing criteria pollutant emissions. The 2014 
regulation focused on reducing GHG emissions. The report finds little 
evidence of sales impacts for Class 6 and 7 vehicles. For Class 8 
vehicles, evidence of pre-buy was found before the 2010 and 2014 
standards' implementation dates, and evidence of low-buy was found 
after the 2002, 2007 and 2010 standards' implementation dates. Based on 
the results of this study, EPA outlined an approach in the RIA that 
could be used to estimate pre- and low-buy effects. In the RIA, we 
explain the methods used to estimate sales effects, as well as how the 
results can be applied to a regulatory analysis (see the RIA, Chapter 
10.1, for further discussion). Our results for the final standards 
suggest pre- and low-buy for Class 8 trucks may range from zero to 
approximately two percent increase in sales over a period of up to 8 
months before the final standards become effective for MY 2027 (pre-
buy), and a decrease in sales from zero to just under three percent 
over a period of up to 12 months after the standards begin (low-buy).
    In response to our request for comment in the NPRM on the approach 
to estimate sales effects discussed in the RIA, some commenters stated 
that EPA estimates of pre- and low-buy in the draft RIA were 
underestimated, citing results from ACT Research. The estimated costs 
used by ACT Research were significantly higher than those estimated by 
EPA in the NPRM, which led, in part, to higher estimated sales effects. 
Another commenter pointed out limitations in EPA's approach that could 
lead to overestimates of sales effects, and they recommended removing 
the quantitative analysis of sales effects. We believe that despite its 
limitations, EPA's peer-reviewed approach continues to be appropriate 
given the data and literature that are currently available. In 
addition, the EPA peer-reviewed study and method used to estimate 
illustrative results in Chapter 10 of the RIA is transparent, 
reproducible, and ``is based on the best reasonably obtainable 
scientific, technical, and economic information available,'' in 
compliance with OMB Circular A-4.\519\ The model and assumptions used 
by ACT Research did not include sufficient detail for EPA to evaluate 
or replicate that approach, and the other commenter's suggestions of 
how to improve EPA's approach are not currently feasible with available 
data. Furthermore, our analysis is clear that the lower bound is zero 
(i.e., there may be no sales effect). For further detail regarding 
these comments and EPA's response to the costs estimates cited by 
commenters, see Section 18 of the Response to Comments. For information 
on costs estimated in this final rule, see Chapter 7 of the RIA. For 
further information on comments EPA received and EPA's response to 
comments on our sales effects analysis, see Section 25 of the Response 
to Comments.
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    \519\ OMB Circular A-4 (found at https://obamawhitehouse.archives.gov/omb/circulars_a004_a-4/#d) provides 
guidance to Federal Agencies on the development of regulatory 
analyses as required under Executive Order 12866.
---------------------------------------------------------------------------

    In addition to potential sales impacts from changes in purchase 
price, the requirement for longer useful life and emission warranty 
periods may also affect vehicle sales. While longer emission warranty 
periods and useful life are likely to increase the purchase price of 
new HD vehicles, these increases may be offset by reduced operating 
costs. This is because longer useful life periods are expected to make 
emission control technology components more durable, and more durable 
components, combined with manufacturers paying for repairs during the 
longer warranty periods, will in turn reduce repair costs for vehicle 
owners. These combined effects may increase (or reduce the decrease in) 
sales of new HD vehicles if fleets and independent owner-operators 
prefer to purchase more durable vehicles with overall lower repair 
costs.\520\ EPA is unable to quantify these effects because existing 
literature does not provide sufficient insight on the relationship 
between warranty changes, increases in prices due to increased warranty 
periods, and sales impacts. EPA continues to investigate methods for 
estimating sales impacts of longer emission warranty periods and useful 
life. See the RIA, Chapter 10.1.1, for more information.
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    \520\ The reduced repair costs may counteract some of the sales 
effect of increased vehicle purchase cost. As a result, they may 
reduce incentives for pre- and low-buy and mitigate adverse sales 
impacts.
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    Another potential effect of the final standards is transportation 
mode shift, which is a change from using a heavy duty-truck to using 
another mode of transportation (typically rail or marine). Whether 
shippers switch to a different transportation mode for freight depends 
not only on the cost per mile of the shipment (freight rate), but also 
the value of the shipment, the time needed for shipment, and the 
availability of supporting infrastructure. This final rule is not 
expected to have a large impact on truck freight rates given that the 
price of the truck is only a small part of the cost per mile of a ton 
of goods. For that reason, we expect little mode shift due to the final 
standards. The RIA, Chapter 10.1.3, discusses this issue.
    An additional potential area of impact of the standards is on fleet 
turnover and the associated reduction in emissions from new vehicles. 
After implementation of the final standards, each individual new 
vehicle sold will produce lower emissions per mile relative to legacy 
vehicles. However, the standards will reduce total HD highway fleet 
emissions gradually. This is because, initially, the vehicles meeting 
the final standards will only be a small portion of the total fleet; 
over time, as more vehicles subject to the standards enter the market 
and older vehicles leave the market, greater emission reductions will 
occur. If pre-buy and low-buy behaviors occur, then the initial 
emission reductions are likely to be smaller than expected. This is

[[Page 4431]]

because, under pre-buy conditions, the pre-bought vehicles will be 
certified to less stringent standards and their emission reductions 
will be smaller than what will be realized if those vehicles were 
subject to the final standards. However, the new vehicles are likely 
less polluting than the older vehicles that they are most likely to 
displace, and there may be an earlier reduction in emissions than would 
have occurred without the standards since the vehicles are being 
purchased ahead of the implementation of new standards, rather than at 
a natural point in the purchase cycle. Under low-buy, emission 
reductions will be slower because there is slower adoption of new 
vehicles than without the standards. See the RIA, Chapter 10.1.2, for 
more information on this, as well as the discussion in this section 
related to vehicle miles traveled (VMT).
    The standards may also result in a net reduction in new vehicle 
sales if there is either a smaller pre-buy than a post-standards low-
buy, or some potential buyers decide not to purchase at all. In this 
case, the VMT of vehicles in the existing fleet may increase to 
compensate for the ``missing'' vehicles. However, since we expect this 
effect to be small, to the extent it might exist, we expect the total 
effect on emissions reductions to be small.

B. Employment Impacts

    This section discusses potential employment impacts due to this 
regulation, as well as our partial estimates of those impacts. We focus 
our analysis on the motor vehicle manufacturing and the motor vehicle 
parts manufacturing sectors because these sectors are most directly 
affected.\521\ While the final rule primarily affects heavy duty 
vehicle engines, the employment effects are expected to be felt more 
broadly in the motor vehicle and parts sectors due to the effects of 
the standards on sales.
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    \521\ The employment analysis in the RIA is part of the EPA's 
ongoing effort to ``conduct continuing evaluations of potential loss 
or shifts of employment which may result from the administration or 
enforcement of [the Act]'' pursuant to CAA section 321(a).
---------------------------------------------------------------------------

    In general, the employment effects of environmental regulation are 
difficult to disentangle from other economic changes (especially the 
state of the macroeconomy) and business decisions that affect 
employment, both over time and across regions and industries. In light 
of these difficulties, we look to economic theory to provide a 
constructive framework for approaching these assessments and for better 
understanding the inherent complexities in such assessments.
    Economic theory of labor demand indicates that employers affected 
by environmental regulation may change their demand for different types 
of labor in different ways. They may increase their demand for some 
types, decrease demand for other types, or maintain demand for still 
other types. To present a complete picture, an employment impact 
analysis describes both positive and negative changes in employment. A 
variety of conditions can affect employment impacts of environmental 
regulation, including baseline labor market conditions, employer and 
worker characteristics, industry, and region.
    In the RIA, we describe three ways employment at the firm level 
might be affected by changes in a firm's production costs due to 
environmental regulation: A demand effect, caused by higher production 
costs increasing market prices and decreasing demand; a cost effect, 
caused by additional environmental protection costs leading regulated 
firms to increase their use of inputs; and a factor-shift effect, in 
which post-regulation production technologies may have different labor 
intensities than their pre-regulation counterparts.522 523
---------------------------------------------------------------------------

    \522\ Morgenstern, Richard D., William A. Pizer, and Jhih-Shyang 
Shih (2002). ``Jobs Versus the Environment: An Industry-Level 
Perspective.'' Journal of Environmental Economics and Management 43: 
412-436.
    \523\ Berman and Bui have a similar framework in which they 
consider output and substitution effects that are similar to 
Morgenstern et al.'s three effect (Berman, E. and L.T. M. Bui 
(2001). ``Environmental Regulation and Labor Demand: Evidence from 
the South Coast Air Basin.'' Journal of Public Economics 79(2): 265-
295).
---------------------------------------------------------------------------

    Due to data limitations, EPA is not quantifying the impacts of the 
final regulation on firm-level employment for affected companies, 
although we acknowledge these potential impacts. Instead, we discuss 
factor-shift, demand, and cost employment effects for the regulated 
sector at the industry level in the RIA. Factor-shift effects are due 
to changes in labor intensity of production due to the standards. We do 
not have information on how regulations might affect labor intensity of 
production, and therefore we cannot estimate the factor-shift effect on 
employment. Demand effects on employment are due to changes in labor 
due to changes in demand. In general, if the regulation causes HD sales 
to decrease, fewer people would be needed to assemble trucks and to 
manufacture their components. If pre-buy occurs, HD vehicle sales may 
increase temporarily in advance of the standards, leading to temporary 
increases in employment, but if low-buy occurs following the standards, 
there could be temporary decreases in employment. We outlined a method 
to quantify sales impacts, though we are not using it to estimate 
effects on fleet turnover in this rulemaking. As such, we do not 
estimate the demand-effect impact on employment due to the standards. 
However, after consideration of comments, we have added an explanation 
of a method to Chapter 10.2 of the RIA that could be used to estimate 
sales effects on employment. We also extend the illustrative sales 
effects results to show how that method could be used to estimate 
demand employment effects of this final rule. These results, to the 
extent they occur, should be interpreted as short-term effects, due to 
the short-term nature of pre- and low-buy, with a lower-bound of no 
change in employment due to no change in sales. If the maximum 
estimated total change in sales were to occur, our illustrative results 
suggest that this level of pre-buy could lead to an increase of up to 
about 450 job-years before implementation in 2027, and the maximum 
level of low-buy could lead to a decrease of up to about 640 job-years 
after implementation regulation.
    Cost effects on employment are due to changes in labor associated 
with increases in costs of production, and we do estimate a partial 
employment impact due to changes in cost. This cost effect includes the 
impact on employment due to the increase in production costs needed for 
vehicles to meet the standards. (Note that this analysis is separate 
from any employment effect due to changes in vehicle sales; in other 
words, the analysis holds output constant.) In the RIA, we capture 
these effects using the historic share of labor as a part of the cost 
of production to extrapolate future estimates of the share of labor as 
a cost of production. This provides a sense of the order of magnitude 
of expected impacts on employment.
    These estimates are averages, covering all the activities in these 
sectors. The estimates may not be representative of the labor effects 
when expenditures are required on specific activities, or when 
manufacturing processes change sufficiently that labor intensity 
changes. In addition, these estimates do not include changes in 
industries that supply these sectors, such as steel or electronics 
producers, or in other potentially indirectly affected sectors (such as 
shipping). Other sectors that sell, purchase, or service HD vehicles 
may also face employment impacts due to the standards. The effects on 
these

[[Page 4432]]

sectors will depend on the degree to which compliance costs are passed 
through to prices for HD vehicles and the effects of warranty and 
useful life requirements on demand for vehicle repair and maintenance. 
EPA does not have data to estimate the full range of possible 
employment impacts. For more information on how we estimate the 
employment impacts due to increased costs, see Chapter 10 of the RIA.
    We estimated employment effects due to increases in vehicle costs, 
based on the ratio of labor to production costs derived from historic 
data for the final rule. Results are provided in job-years, where a 
job-year is, for example, one year of full-time work for one person, or 
one year of half-time work for two people. Increased cost of vehicles 
and parts will, by itself and holding labor intensity constant, be 
expected to increase employment by 1,000 to 5,300 job years in 2027, 
with effects decreasing every year after, see Chapter 10 of the RIA for 
details.
    While we estimate employment impacts, measured in job-years, 
beginning with program implementation, some of these employment gains 
may occur earlier as vehicle manufacturers and parts suppliers hire 
staff in anticipation of compliance with the standards. Additionally, 
holding all other factors constant, demand-effect employment may 
increase prior to MY 2027 due to pre-buy, and may decrease, potentially 
temporarily, afterwards.\524\ We present a range of possible results 
because our analysis consists of data from multiple industrial sectors 
that we expect will be directly affected by the final regulation, as 
well as data from multiple sources. For more information on the data we 
use to estimate the cost effect, see Chapter 10.2 of the RIA.
---------------------------------------------------------------------------

    \524\ Note that the standards are not expected to provide 
incentives for manufacturers to shift employment between domestic 
and foreign production. This is because the standards will apply to 
vehicles sold in the U.S. regardless of where they are produced.
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XI. Other Amendments

    This section describes several amendments to correct, clarify, and 
streamline a wide range of regulatory provisions for many different 
types of engines, vehicles, and equipment.\525\ Section XI.A includes 
technical amendments to compliance provisions that apply broadly across 
EPA's emission control programs to multiple industry sectors, including 
light-duty vehicles, light-duty trucks, marine diesel engines, 
locomotives, and various types of nonroad engines, vehicles, and 
equipment. Some of those amendments are for broadly applicable testing 
and compliance provisions in 40 CFR parts 1065, 1066, and 1068. Other 
cross-sector issues involve making the same or similar changes in 
multiple standard-setting parts for individual industry sectors.
---------------------------------------------------------------------------

    \525\ A docket memo includes redline text to highlight all the 
changes to the regulations in the final rule. See ``Redline Document 
Showing Final Changes to Regulatory Text in the Heavy-Duty 2027 
Rule'', EPA memorandum from Alan Stout to Docket EPA-HQ-OAR-2019-
0055.
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    We are adopting amendments in two areas of note for the general 
compliance provisions in 40 CFR part 1068. First, we are adopting a 
comprehensive approach for making confidentiality determinations 
related to compliance information that EPA collects from companies. We 
are applying these confidentiality determination provisions for all 
highway, nonroad, and stationary engine, vehicle, and equipment 
programs, as well as aircraft and portable fuel containers. Second, we 
are adopting provisions that include clarifying text to establish what 
qualifies as an adjustable parameter and to identify the practically 
adjustable range for those adjustable parameters. The final rule 
includes specific provisions related to electronic controls that aim to 
deter tampering.
    The rest of Section XI describes amendments that apply uniquely to 
individual industry sectors. These amendments apply to heavy-duty 
highway engines and vehicles, light-duty motor vehicles, large nonroad 
SI engines, small nonroad SI engines, recreational vehicles and nonroad 
equipment, marine diesel engines, locomotives, and stationary emergency 
CI engines.

A. General Compliance Provisions (40 CFR Part 1068) and Other Cross-
Sector Issues

    The regulations in 40 CFR part 1068 include compliance provisions 
that apply broadly across EPA's emission control programs for engines, 
vehicles, and equipment. This section describes several amendments to 
these regulations. This section also includes amendments that make the 
same or similar changes in multiple standard-setting parts for 
individual industry sectors or other related portions of the CFR. The 
following sections describe these cross-sector issues.
1. Confidentiality Determinations
    EPA adopts emission standards and corresponding certification 
requirements and compliance provisions that apply to on-highway CI and 
SI engines (such as those adopted in this action for on-highway heavy-
duty engines) and vehicles, and to stationary and nonroad CI and SI 
engines, vehicles, and equipment.\526\ This final rule amends our 
regulations, including 40 CFR parts 2 and 1068 and the standard-setting 
parts,\527\ to establish a broadly applicable set of confidentiality 
determinations by categories of information, through rulemaking. Under 
this final rule, EPA is determining that certain information 
manufacturers must submit (or EPA otherwise collects) under the 
standard-setting parts including for certification, compliance 
oversight, and in response to certain enforcement activities,\528\ is 
either emission data or otherwise not entitled to confidential 
treatment. As a result of these determinations, information in these 
categories is not subject to the case-by-case or class determination 
processes under 40 CFR part 2 that EPA typically uses to evaluate 
whether such information qualifies for confidential treatment. Where we 
codify a determination that information is emission data or otherwise 
not entitled to confidential treatment, it will be subject to 
disclosure to the public without further notice. Any determination that 
applies for submitted information continues to apply even if that 
information is carried into other documents that EPA prepares for 
internal review or publication. EPA also notes that we are not making 
confidentiality determinations in this rulemaking for certain other 
identified information submitted to us for certification and 
compliance, which will remain subject to the case-by-case or class 
determination process under 40 CFR part 2, as established in this 
rulemaking under 40 CFR 2.301(j)(4).
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    \526\ Nonroad applications include marine engines, locomotives, 
and a wide range of other land-based vehicles and equipment. 
Standards and certification requirements also apply for portable 
fuel containers and for fuel tanks and fuel lines used with some 
types of nonroad equipment. Standards and certification requirements 
also apply for stationary engines and equipment, such as generators 
and pumps. EPA also has emission standards for aircraft and aircraft 
engines. This preamble refers to all these different regulated 
products as ``sources.''
    \527\ 40 CFR parts 59, 60, 85, 86, 87, 1068, 1030, 1031, 1033, 
1036, 1037, 1039, 1042, 1043, 1045, 1048, 1051, 1054, and 1060. 
These parts are hereinafter collectively referred to as ``the 
standard-setting parts.''
    \528\ We also receive numerous FOIA requests for information 
once enforcement actions have concluded. In responding to those 
requests, to the extent the information collected through the 
enforcement action corresponds to a category of certification or 
compliance information that we have determined to be emission data 
or otherwise not entitled to confidential treatment in this 
rulemaking, this final rule establishes that such information is 
also subject to the same categorical confidentiality determinations 
specified in 40 CFR 1068.11.

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[[Page 4433]]

    The CAA states that ``[a]ny records, reports or information 
obtained under [section 114 and parts B and C of Subchapter II] shall 
be available to the public. . . . '' \529\ Thus, the CAA begins with a 
presumption that the information submitted to EPA will be available to 
be disclosed to the public.\530\ It then provides a narrow exception to 
that presumption for information that ``would divulge methods or 
processes entitled to protection as trade secrets. . . .'' \531\ The 
CAA then narrows this exception further by excluding ``emission data'' 
from the category of information eligible for confidential treatment. 
While the CAA does not define ``emission data,'' EPA has done so by 
regulation at 40 CFR 2.301(a)(2)(i). EPA releases, on occasion, some of 
the information submitted under CAA sections 114 and 208 to parties 
outside of the Agency of its own volition, through responses to 
requests submitted under the Freedom of Information Act 
(``FOIA''),\532\ or through civil litigation. Typically, manufacturers 
may claim some of the information they submit to EPA is entitled to 
confidential treatment as confidential business information (``CBI''), 
which is exempt from disclosure under Exemption 4 of the FOIA.\533\ 
Generally, when we have information that we intend to disclose publicly 
that is covered by a claim of confidentiality under FOIA Exemption 4, 
EPA has a process to make case-by-case or class determinations under 40 
CFR part 2 to evaluate whether such information is or is not emission 
data, and whether it otherwise qualifies for confidential treatment 
under FOIA Exemption 4.\534\
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    \529\ CAA section 114(c) and 208(c); 42 U.S.C. 7414(c) and 
7542(c).
    \530\ CAA section 114(c) and 208(c); 42 U.S.C. 7414(c) and 
7542(c).
    \531\ CAA section 114(c) and 208(c); 42 U.S.C. 7414(c) and 
7542(c).
    \532\ 5 U.S.C. 552.
    \533\ 5 U.S.C. 552(b)(4).
    \534\ 40 CFR 2.205.
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    This final rule adopts provisions regarding the confidentiality of 
certification and compliance information that is submitted by 
manufacturers to EPA for a wide range of engines, vehicles, and 
equipment that are subject to emission standards and other requirements 
under the CAA. This includes motor vehicles and motor vehicle engines, 
nonroad engines and nonroad equipment, aircraft and aircraft engines, 
and stationary engines. It also includes portable fuel containers 
regulated under 40 CFR part 59, subpart F, and fuel tanks, fuel lines, 
and related fuel system components regulated under 40 CFR part 1060. 
The regulatory provisions regarding confidentiality determinations for 
these products are being codified broadly in 40 CFR 1068.11, with 
additional detailed provisions for specific sectors in the regulatory 
parts referenced in 40 CFR 1068.1. With this notice-and-comment 
rulemaking, EPA is making categorical emission data and confidentiality 
determinations that will apply to certain information collected by EPA 
for engine, vehicle, and equipment certification and compliance, 
including information collected during certain enforcement 
actions.\535\
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    \535\ Throughout this preamble, we refer to certification and 
compliance information. Hereinafter, the enforcement information 
covered by the confidentiality determination in this final rule is 
included when we refer to certification and compliance information.
---------------------------------------------------------------------------

    At this time, EPA is not determining that any specific information 
is CBI or entitled to confidential treatment. EPA is instead 
identifying categories of information that are not appropriate for such 
treatment. We are maintaining the 40 CFR part 2 process for any 
information we are not determining to be emission data or otherwise not 
entitled to confidential treatment in this rulemaking. As explained 
further in the following discussion, the emission data and 
confidentiality determinations in this action are intended to increase 
the efficiency with which the Agency responds to FOIA requests and to 
provide consistency in the treatment of the same or similar information 
collected under the standard-setting parts. Establishing these 
determinations through this rulemaking will provide predictability for 
both information requesters and submitters. The emission data and 
confidentiality determinations in this final rule will also increase 
transparency in the certification programs.
    After consideration of comments, we are revising the regulation 
from that proposed in the final rule to clarify that information 
submitted in support of a request for an exemption from emission 
standards and certification requirements will be subject to the 40 CFR 
part 2 process unless information from such a request is specifically 
identified as emission data in 40 CFR 1068.11. For example, emission 
test results used to demonstrate that engines meet a certain level of 
emission control that is required as a condition of a hardship 
exemption would not be entitled to confidential treatment, while other 
information not identified as emission data in 40 CFR 1068.11 would be 
subject to the 40 CFR part 2 process for making confidentiality 
determinations. These provisions apply equally for exemptions 
identified in 40 CFR part 1068, subpart C or D, or in the standard-
setting parts.
    In 2013 EPA published CBI class determinations for information 
related to certification of engines and vehicles under the standard-
setting parts.\536\ These determinations established whether those 
particular classes of information were releasable or entitled to 
confidential treatment and were instructive when making case-by-case 
determinations for other similar information within the framework of 
the CAA and the regulations. However, the determinations did not 
resolve all confidentiality questions regarding information submitted 
to the Agency for the standard-setting parts, and EPA receives numerous 
requests each year to disclose information that is not within the scope 
of these 2013 CBI class determinations.
---------------------------------------------------------------------------

    \536\ EPA, Class Determination 1-13, Confidentiality of Business 
Information Submitted in Certification Applications for 2013 and 
subsequent model year Vehicles, Engines and Equipment, March 28, 
2013, available at https://www.epa.gov/sites/default/files/2020-02/documents/1-2013_class_determination.pdf.
---------------------------------------------------------------------------

    Prior to this rulemaking, the Agency has followed the existing 
process in 40 CFR part 2 when making case-by-case or class 
confidentiality determinations. The part 2 confidentiality 
determination process is time consuming for information requesters, 
information submitters, and EPA. The determinations in this rulemaking 
will allow EPA to process requests for information more quickly, as the 
Agency will not always need to go through the part 2 process to make 
case-by-case determinations. Additionally, the determinations in this 
rulemaking will also provide predictability and consistency to 
information submitters on how EPA will treat the information. Finally, 
the part 2 confidentiality determination process is very resource-
intensive for EPA, as it requires personnel in the program office to 
draft letters to the manufacturers (of which there may be many) 
requesting that they substantiate their claims of confidentiality, 
review each manufacturer's substantiation response, and prepare a 
recommendation for the Office of General Counsel. The Office of General 
Counsel then must review the recommendation and all the materials to 
issue a final determination on the entitlement of the information to 
confidential treatment. For these reasons, we are amending our 
regulations in 40 CFR parts 2 and 1068 to establish a broadly 
applicable set of confidentiality determinations for categories of 
information, through this rulemaking. This final action supersedes

[[Page 4434]]

the class determinations made in 2013.\537\
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    \537\ We intend for this rulemaking to be consistent with Tables 
1 and 2 from the 2013 class determinations. Specifically, the CBI 
class determinations reflected in Table 1 and Table 2 of the 2013 
determination are consistent with the determinations described in 
Section XI.A.1.i. and Section XI.A.1.iii, respectively. However, for 
the reasons described in Section XI.A.1.iv, the information in Table 
3 of the 2013 determination will be subject to the existing part 2 
process, such that EPA will continue to make case-by-case CBI 
determinations as described in Section XI.A.1.iv.
---------------------------------------------------------------------------

    In this action, EPA is finalizing regulations to establish 
categories for certain certification and compliance information 
submitted under the standard-setting parts and determining that certain 
categories of certification and compliance information are not entitled 
to confidential treatment, including revisions to 40 CFR parts 2, 59, 
60, 85, 86, 87, 1030, 1031, 1033, 1036, 1037, 1043, 1045, 1048, 1051, 
1054, 1060, and 1068. The confidentiality determinations for these 
categories, and the basis for such determinations, are described in the 
following discussion. Additionally, a detailed description of the 
specific information submitted under the standard-setting parts that 
currently falls within these categories is also available in the docket 
for this rulemaking.\538\ The determinations made in this rulemaking 
will serve as notification of the Agency's decisions on: (1) The 
categories of information the Agency will not treat as confidential; 
and (2) the categories of information that may be claimed as 
confidential but will remain subject to the existing part 2 process. We 
are not making in this rule a determination in favor of confidential 
treatment for any information collected for certification and 
compliance of engines, vehicles, equipment, and products subject to 
evaporative emission standards. In responding to requests for 
information not determined in this rule to be emission data or 
otherwise not entitled to confidential treatment, we will continue to 
apply the existing case-by-case process governed by 40 CFR part 2.
---------------------------------------------------------------------------

    \538\ See Zaremski, Sara. Memorandum to docket EPA-HQ-OAR-2019-
0055. ``Supplemental Information for CBI Categories for All 
Industries and All Programs''. October 1, 2021, and attachment ``CBI 
Categories for All Industries All Programs'' (hereinafter ``CBI 
Chart''), available in the docket for this action.
---------------------------------------------------------------------------

    We are also establishing provisions in the Agency's Clean Air Act-
specific FOIA regulations at 40 CFR 2.301(j)(2) and (4) concerning 
information determined to be entitled to confidential treatment through 
rulemaking in 40 CFR part 1068. These provisions are very similar to 
the regulations established by the Greenhouse Gas Reporting Program 
from 40 CFR part 98 that is addressed at 40 CFR 2.301(d). The 
regulation at 40 CFR 2.301(j)(4)(ii) addresses the Agency's process for 
reconsidering a determination that information is entitled to 
confidential treatment under 40 CFR 2.204(d)(2) if there is a change in 
circumstance in the future. This provision is intended to maintain 
flexibility the Agency currently has under its part 2 regulations. Note 
that because this rulemaking is not determining that any information is 
entitled to confidential treatment, these regulations at 40 CFR 
2.301(j)(2) and (4) do not apply to any confidentiality determination 
made by this rulemaking.
    The information categories established in this final action are:
    (1) Certification and compliance information,
    (2) fleet value information,
    (3) source family information,
    (4) test information and results,
    (5) averaging, banking, and trading (``ABT'') credit information,
    (6) production volume information,
    (7) defect and recall information, and
    (8) selective enforcement audit (``SEA'') compliance information.
    The information submitted to EPA under the standard-setting parts 
can be grouped in these categories based on their shared 
characteristics. That said, much of the information submitted under the 
standard-setting parts could be logically grouped into more than one 
category. For the sake of organization, we have chosen to label 
information as being in just one category where we think it fits best. 
We believe this approach will promote greater accessibility to the CBI 
determinations, reduce redundancy within the categories that could lead 
to confusion, and ensure consistency in the treatment of similar 
information in the future. We received supporting comment on the 
following: (1) Our proposed categories of information; (2) the proposed 
confidentiality determination on each category; and (3) our placement 
of each data point under the category proposed. None of the comments we 
received on the proposed emission data determinations disputed EPA's 
conclusion that the information specified in those determinations is 
emission data. We have responded to these comments in the Response to 
Comments.
    i. Information that is emission data and therefore not entitled to 
confidential treatment.
    We are applying the regulatory definition of ``emission data'' in 
40 CFR 2.301(a)(2)(i) to determine that certain categories of source 
certification and compliance information are not entitled to 
confidential treatment. As relevant here, a source is generally the 
engine, vehicle, or equipment covered by a certificate of conformity. 
Alternatively, a source is each individual engine, vehicle, or 
equipment produced under a certificate of conformity. CAA sections 114 
and 208 provide that certain information submitted to EPA may be 
entitled to confidential treatment. However, section 114 also expressly 
excludes emission data from that category of information. The CAA does 
not define ``emission data,'' but EPA has done so by regulation in 40 
CFR 2.301(a)(2)(i).
    EPA's regulations broadly define emission data as information that 
falls into one or more of three types of information. Specifically, 
emission data is defined in 40 CFR 2.301(a)(2)(i), for any source of 
emission of any substance into the air as:
     Information necessary to determine the identity, amount, 
frequency, concentration, or other characteristics (to the extent 
related to air quality) of any emission which has been emitted by the 
source (or of any pollutant resulting from any emission by the source), 
or any combination of the foregoing;
     Information necessary to determine the identity, amount, 
frequency, concentration, or other characteristics (to the extent 
related to air quality) of the emissions which, under an applicable 
standard or limitation, the source was authorized to emit (including, 
to the extent necessary for such purposes, a description of the manner 
or rate of operation of the source); and
     A general description of the location and/or nature of the 
source to the extent necessary to identify the source and to 
distinguish it from other sources (including, to the extent necessary 
for such purposes, a description of the device, installation, or 
operation constituting the source).
    EPA's broad general definitions of emissions data also exclude 
certain information related to products still in the research and 
development phase or products not yet on the market except for limited 
purposes. Thus, for example, 40 CFR 2.301(a)(2)(ii) excludes 
information related to ``any product, method, device, or installation 
(or any component thereof) designed and intended to be marketed or used 
commercially but not yet so marketed or used.'' This specific exclusion 
from the definition of emissions data is limited in time.
    Consistent with this limitation, and as described in Sections 
XI.A.1.i and iii, in this rulemaking we are maintaining

[[Page 4435]]

confidential treatment prior to the introduction-into-commerce date for 
the information included in an application for certification. Though 
the nature of this information would otherwise make it emissions data, 
it is not emissions data for purposes of this regulatory definition and 
thus subject to release, until the product related to the information 
has been introduced into commerce, consistent with 40 CFR 
2.301(a)(2)(ii). The introduction-to-commerce date is generally 
specified in an application for certification, even in cases where it 
is not required. After consideration of comments, we are clarifying 
from the proposal in the final rule that when an application for 
certification does not specify an introduction into commerce date or in 
situations where a certificate of conformity is issued after the 
introduction-into-commerce date, EPA will use the date of certificate 
issuance, as stated in the final 40 CFR 1068.10(d)(1).
    We are establishing in 40 CFR 1068.11(a) that certain categories of 
information the Agency collects in connection with the Title II 
programs are information that meet the regulatory definition of 
emission data under 40 CFR 2.301(a)(2)(i). The following sections 
describe the categories of information we have determined to be 
emission data, based on application of the definition at 40 CFR 
2.301(a)(2)(i) to the shared characteristics of the information in each 
category and our rationale for each determination. The CBI Chart in the 
docket provides a comprehensive list of the current regulatory 
citations under which we collect the information that we have grouped 
into each category and can be found in the docket for this action. For 
ease of reference, we have also indicated in the CBI Chart the 
reason(s) explained in Sections XI.A.1 and 3 of this action for why EPA 
has determined that the information submitted is not entitled to 
confidential treatment. The CBI Chart provides the information EPA 
currently collects that is covered by the determinations in this 
rulemaking, the regulatory citation the information is collected under, 
the information category for the information, the confidentiality 
determination for the information, and the rationale EPA used to 
determine whether the information is not entitled to confidential 
treatment (i.e., the information qualifies as emission data under one 
or more subparagraphs of the regulatory definition of emission data, is 
both emission data and publicly available after the introduction-into-
commerce-date, etc.). Much of the information covered by these 
determinations are emission data under more than one basis under the 
regulatory definition of emission data, as described at the end of each 
of the sections that follow. For each category of information and each 
data point we have determined belongs in each category, each basis 
independently is an alternative argument supporting EPA's final 
determinations.
    ii. Information necessary to determine the identity, amount, 
frequency, concentration, or other characteristics (to the extent 
related to air quality) of any emission which has been emitted by the 
source (or of any pollutant resulting from any emission by the source), 
or any combination of the foregoing.
    We are finalizing the proposed determination that the categories of 
information identified meet the regulatory definition of emission data 
under 40 CFR 2.301(a)(2)(i)(A), which defines emission data to include 
``[i]nformation necessary to determine the identity, amount, frequency, 
concentration, or other characteristics (to the extent related to air 
quality) of any emission which has been emitted by the source (or of 
any pollutant resulting from any emission by the source), or any 
combination of the foregoing[.]'' \539\ For shorthand convenience, we 
refer to information that qualifies as emission data under subparagraph 
(A) in the definition of emission data as merely ``paragraph A 
information.''
---------------------------------------------------------------------------

    \539\ 40 CFR 2.301(a)(2)(i)(A).
---------------------------------------------------------------------------

    EPA collects emission information during certification, compliance 
reporting, SEAs, defect and recall reporting, in ABT programs, and in 
various testing programs like production line testing (``PLT'') and in-
use testing. The following categories of information are emission data 
under 40 CFR 2.301(a)(2)(i)(A):
    (1) Fleet value information,
    (2) test information and results (including certification testing, 
PLT, in-use testing, fuel economy testing, and SEA testing),
    (3) ABT credit information,
    (4) production volume,
    (5) defect and recall information, and
    (6) SEA compliance information.
    All these categories include information that also fits under the 
other emission data regulatory definition subparagraphs, therefore, the 
lists in this section are not exhaustive of the information in each 
category. The 40 CFR 2.301(a)(2)(i)(A) information we identify in this 
section under each of the categories is also emission data under 
paragraph (a)(2)(i)(B) of the definition of emission data and may also 
be emission data under paragraph (a)(2)(i)(C) of the definition of 
emission data. In the CBI Chart in the docket, we have identified for 
every piece of information in every category all the applicable 
emission data definition subparagraphs. Nevertheless, in this action, 
we have chosen to explain each piece of information in detail only 
under the most readily applicable subparagraph of emission data, while 
highlighting that the information could also qualify as emission data 
under another subparagraph of the regulatory definition of emission 
data. Consistent with 40 CFR 2.301(a)(2)(ii), under this determination, 
we will not release information included in an application for 
certification prior to the introduction-into-commerce-date, except 
under the limited circumstances already provided for in that regulatory 
provision.
    Fleet Value Information: The fleet value information category 
includes the following information that underlies the ABT compliance 
demonstrations and fleet average compliance information for on-highway 
and nonroad:
    (1) Offsets,
    (2) displacement,
    (3) useful life,
    (4) power payload tons,
    (5) load factor,
    (6) integrated cycle work,
    (7) cycle conversion factor, and
    (8) test cycle.
    The information in this category underlies the fleet average 
calculations, which are necessary to understand the type and amount of 
emissions released in-use from sources regulated under the standard-
setting parts that require a fleet average compliance value. These 
values represent compounds emitted, though the raw emissions from an 
individual source may be different from these values due to other 
variables in the fleet value calculation. For these reasons, we 
determine the fleet value information category is emission data because 
it is necessary to identify and determine the amount of emissions 
emitted by sources.\540\ Note, we are also determining that a portion 
of the fleet value information category meets another basis in the 
emission data definition in 40 CFR 2.301(a)(2)(i), as discussed in more 
detail in Section XI.A.1.i.b, because it is ``[i]nformation necessary 
to determine the identity, amount, frequency, concentration, or other 
characteristics (to the extent related to air quality) of the emissions 
which, under an applicable standard or limitation, the source was 
authorized to

[[Page 4436]]

emit (including, to the extent necessary for such purposes, a 
description of the manner or rate of operation of the source)[.]'' 
\541\
---------------------------------------------------------------------------

    \540\ Id.
    \541\ 40 CFR 2.301(a)(2)(i)(B).
---------------------------------------------------------------------------

    Test Information and Results: The test information and results 
category includes information collected during the certification 
process, PLT testing, in-use testing programs, testing to determine 
fuel economy, and testing performed during an SEA. This category 
encompasses the actual test results themselves and information 
necessary to understand how the test was conducted, and other 
information to fully understand the results. We are including in the 
test information and results category the certification test results 
information, including emission test results which are required under 
the standard-setting parts. Before introducing a source into commerce, 
manufacturers must certify that the source meets the applicable 
emission standards and emissions related requirements. To do this, 
manufacturers conduct specified testing during the useful life of a 
source and submit information related to those tests. Emission test 
results are a straightforward example of emission data, as they 
identify and measure the compounds emitted from the source during the 
test. Furthermore, the tests were designed and are performed for the 
explicit purpose of determining the identity, amount, frequency, 
concentration, or other air quality characteristics of emissions from a 
source. For these reasons, we are determining that test information and 
results category is emission data because it is necessary to determine 
the emissions emitted by a source.\542\ We are also determining that 
all the information in the test information and results category, 
except fuel economy label information, is emissions data under another 
subsection of the regulatory definition of emissions data it is 
``[i]nformation necessary to determine the identity, amount, frequency, 
concentration, or other characteristics (to the extent related to air 
quality) of the emissions which, under an applicable standard or 
limitation, the source was authorized to emit (including, to the extent 
necessary for such purposes, a description of the manner or rate of 
operation of the source)[.]'' \543\ See Section XI.A.1.i.b for a more 
detailed discussion for issues related to test information and results. 
See Section XI.A.1.iii for additional discussion of fuel economy label 
information.
---------------------------------------------------------------------------

    \542\ 40 CFR 2.301(a)(2)(i)(A).
    \543\ 40 CFR 2.301(a)(2)(i)(B).
---------------------------------------------------------------------------

    EPA collects the following test information and results from the 
PLT program. For CI engines and vehicles these include: CO results, 
particulate matter (PM) results, NOX results, NOX 
+ HC results, and HC results. For SI engines and vehicles and for 
products subject to the evaporative emission standards these include: 
Fuel type used, number of test periods, actual production per test 
period, adjustments, modifications, maintenance, test number, test 
duration, test date, end test period date, service hours accumulated, 
test cycle, number of failed engines, initial test results, final test 
results, and cumulative summation. Manufacturer-run production-line 
testing is conducted under the standard-setting parts to ensure that 
the sources produced conform to the certificate issued. PLT results are 
emission test results and, for that reason, are among the most 
straightforward examples of emission data, as they identify and measure 
the compounds emitted from the source during the test. For example, the 
measured amounts of specified compounds (like HC results, CO results, 
and PM results) are measured emissions, i.e, the factual results of 
testing. Similarly, the number of failed engines is emission data as it 
reflects the results of emissions testing. Additionally, adjustments, 
modifications, maintenance, and service hours accumulated are 
information necessary for understanding the test results. We determine 
that the categories of information listed in this paragraph is 
necessary to understand the context and conditions in which the test 
was performed, like test number, test duration, test date, number of 
test periods, actual production per test period, end test period, and 
is, therefore, emission data because it is information necessary for 
understanding the characteristics of the test as performed, the test 
results, and the information that goes into the emissions calculations. 
Furthermore, PLT is performed for the explicit purpose of determining 
the identity, amount, frequency, concentration, or other air quality 
characteristics of emissions from a source. For these reasons, we 
determine that test information and results category is emission data 
because it is necessary to determine the emissions emitted by a 
source.\544\ Note, we are also determining that the PLT information in 
the test information and results category is emissions data under 
another subsection of the regulatory definition of emissions data, as 
discussed in more detail in Section XI.A.1.i.b, as it additionally 
provides ``[i]nformation necessary to determine the identity, amount, 
frequency, concentration, or other characteristics (to the extent 
related to air quality) of the emissions which, under an applicable 
standard or limitation, the source was authorized to emit (including, 
to the extent necessary for such purposes, a description of the manner 
or rate of operation of the source)[.]'' \545\
---------------------------------------------------------------------------

    \544\ 40 CFR 2.301(a)(2)(i)(A).
    \545\ 40 CFR 2.301(a)(2)(i)(B).
---------------------------------------------------------------------------

    The test information and results category also includes the 
following information from the in-use testing program: A description of 
how the manufacturer recruited vehicles, the criteria use to recruit 
vehicles, the rejected vehicles and the reason they were rejected, test 
number, test date and time, test duration and shift-days of testing, 
weather conditions during testing (ambient temperature and humidity, 
atmospheric pressure, and dewpoint), differential back pressure, 
results from all emissions testing, total hydrocarbons (HC), NMHC, 
carbon monoxide, carbon dioxide, oxygen, NOX, PM, and 
methane, applicable test phase (Phase 1 or Phase 2), adjustments, 
modifications, repairs, maintenance history, vehicle mileage at start 
of test, fuel test results, total lifetime operating hours, total non-
idle operation hours, a description of vehicle operation during 
testing, number of valid Not to Exceed (NTE) events, exhaust flow 
measurements, recorded one-hertz test data, number of engines passed, 
vehicle pass ratio, number of engines failed, outcome of Phase 1 
testing, testing to determine why a source failed, the number of 
incomplete or invalid tests, usage hours and use history, vehicle on 
board diagnostic (``OBD'') system history, engine diagnostic system, 
number of disqualified engines, and number of invalid tests. The in-use 
testing information includes actual test results and the information 
that goes into the emissions calculations. For example, the measured 
amounts of specified compounds (like total HC) are measured emissions, 
and adjustments, modifications, and repairs are information necessary 
for understanding the test results. It is necessary to know if and how 
a source has changed from its certified condition during its use, as 
these changes may impact the source's emissions. Total lifetime 
operating hours and usage hours information is also used to calculate 
emissions during in-use testing. The diagnostic system information is 
necessary for

[[Page 4437]]

understanding emissions, as well, because it provides context to and 
explains the test results; if an issue or question arises from the in-
use testing, the diagnostic system information allows for greater 
understanding of the emissions performance. Additionally, the number of 
disqualified engines is necessary to determine the sources tested, if 
an end user has modified the source such that it cannot be used for in-
use testing, this directly relates to the sources eligible for in-use 
testing and the emission measurements resulting from those tests. For 
these reasons, we determine that the in-use testing information is 
emission data because it is necessary to determine the emissions 
emitted by sources.\546\ Note, we are also determining that the in-use 
testing information is emissions data under another subsection of the 
regulatory definition of emissions data, as discussed in more detail in 
Section XI.A.1.i.b, as it additionally provides ``[i]nformation 
necessary to determine the identity, amount, frequency, concentration, 
or other characteristics (to the extent related to air quality) of the 
emissions which, under an applicable standard or limitation, the source 
was authorized to emit (including, to the extent necessary for such 
purposes, a description of the manner or rate of operation of the 
source)[.]'' \547\
---------------------------------------------------------------------------

    \546\ 40 CFR 2.301(a)(2)(i)(A).
    \547\ 40 CFR 2.301(a)(2)(i)(B).
---------------------------------------------------------------------------

    We are also determining that the test information and results 
category include the underlying information necessary to determine the 
adjusted and rounded fuel economy label values and the resulting label 
values. The underlying information includes test result values that are 
plugged into a calculation included in the standard-setting parts that 
establish the fuel economy rating. These results represent emissions, 
the rate at which they are released, and are necessary to understanding 
the fuel economy rating. For these reasons, the fuel economy label 
information is appropriately included in the test information and 
results category. Accordingly, we determine that fuel economy label 
information is emission data because it is necessary to determine the 
emissions emitted by sources.\548\ Note, also, that a portion of the 
fuel economy label information is not entitled to confidential 
treatment because it is required to be publicly available and is 
discussed in more detail in Section XI.A.1.iii. We are, in this 
rulemaking, superseding the 2013 class determination Table 3 for all 
fuel economy label information, but the determination here applies only 
to a portion of the fuel economy label information, as explained in 
Section XI.A.1.iv.
---------------------------------------------------------------------------

    \548\ 40 CFR 2.301(a)(2)(i)(A).
---------------------------------------------------------------------------

    We are determining that the test information and results category 
include the following information from SEA testing: The test procedure, 
initial test results, rounded test results, final test results, final 
deteriorated test results, the number of valid tests conducted, the 
number of invalid tests conducted, adjustments, modifications, repairs, 
test article preparation, test article maintenance, and the number of 
failed engines and vehicles. SEAs can be required of manufacturers that 
obtain certificates of conformity for their engines, vehicles, and 
equipment. SEA test information includes emission test results from 
tests performed on production engines and equipment covered by a 
certificate of conformity. These tests measure the emissions emitted 
from the test articles; therefore, they are emission data and not 
entitled to confidentiality. The information supporting the test 
results, such as the number of valid tests conducted, the adjustments, 
modifications, repairs, and maintenance regarding the test article, is 
necessary to understand the test results and is, therefore, also 
emission data. For these reasons, we also determine that SEA test 
information is appropriately grouped in test information and results 
category and is emission data because it is necessary to identify and 
determine the amount of emissions from a source.\549\ The SEA test 
information, like all the information in the test information and 
results category, is emissions data under another subsection of the 
regulatory definition of emissions data, as discussed in more detail in 
Section XI.A.1.i.b, as it provides ``[i]nformation necessary to 
determine the identity, amount, frequency, concentration, or other 
characteristics (to the extent related to air quality) of the emissions 
which, under an applicable standard or limitation, the source was 
authorized to emit (including, to the extent necessary for such 
purposes, a description of the manner or rate of operation of the 
source)[.]'' \550\
---------------------------------------------------------------------------

    \549\ Id.
    \550\ 40 CFR 2.301(a)(2)(i)(B).
---------------------------------------------------------------------------

    Production Volume: We are determining that the production volume 
category is emission data and is not entitled to confidential treatment 
because the information is necessary to determine the total emissions 
emitted by the source, where the source is the type of engine, vehicle, 
or equipment covered by a certificate of conformity. The certificate of 
conformity for a source does not, on its face, provide aggregate 
emissions information for all the sources covered by that certificate. 
Rather, it provides information relative to each single unit of the 
source covered by a certificate. The production volume is necessary to 
understand the amount, frequency, and concentration of emissions 
emitted from the aggregate of units covered by a single certificate 
that comprise the source. In other words, unless there will only ever 
be one single engine, vehicle, or equipment covered by the certificate 
of conformity, the emissions from that source will not be expressed by 
the certificate and compliance information alone. The total number of 
engines, vehicles, or equipment produced, in combination with the 
certificate information, is necessary to know the real-world impact on 
emissions from that source. Additionally, the production volume is also 
collected for the purpose of emission modeling. For example, engine 
population (the number of engines in use) is used in the non-road 
emissions model to establish emission standards. Production volume, 
when used in combination with the other emission data we collect 
(certification test results, in-use test results, defects and recalls, 
etc.), also allows EPA and independent third parties to calculate total 
mobile source air emissions. For these reasons, production volume is 
``necessary to determine the identity, amount, frequency, 
concentration, or other characteristics (to the extent related to air 
quality) of any emission which has been emitted by the source (or of 
any pollutant resulting from any emission by the source), or any 
combination of the foregoing[.]'' \551\ Note also that the production 
volume category is emissions data under another subsection of the 
regulatory definition of emissions data, as discussed in more detail in 
Section XI.A.1.i.c, as it additionally provides ``[a] general 
description of the location and/or nature of the source to the extent 
necessary to identify the source and to distinguish it from other 
sources (including, to the extent necessary for such purposes, a 
description of the device, installation, or operation constituting the 
source).'' \552\
---------------------------------------------------------------------------

    \551\ 40 CFR 2.301(a)(2)(i)(A).
    \552\ 40 CFR 2.301(a)(2)(i)(C).
---------------------------------------------------------------------------

    Defect and Recall Information: We are determining that the defect 
and recall information category is emission data and not entitled to 
confidential treatment because it is information necessary to determine 
the emissions from a source that has been issued a

[[Page 4438]]

certificate of conformity.\553\ The only defects and recalls that 
manufacturers or certificate holders are required to report to EPA are 
ones that impact emissions or could impact emissions. Therefore, if a 
defect or recall is reported to us, it is because it causes or may 
cause increased emissions and information relating to that defect or 
recall is necessarily emission data, as it directly relates to the 
source's emissions. The defect and recall information category includes 
any reported emission data available. This information is the available 
test results that a manufacturer has after conducting emission testing, 
and an estimate of the defect's impact on emissions, with an 
explanation of how the manufacturer calculated this estimate and a 
summary of any available emission data demonstrating the impact of the 
defect. Note, we are only determining that a portion of the defect and 
recall information category is paragraph A information. As discussed in 
Section XI.A.1.iv, we are not making a confidentiality determination on 
the defect investigation report at this time. We are also determining 
that the information in this category, excluding the defect 
investigation report, is emissions data under another subsection of the 
regulatory definition of emissions data, as discussed in more detail in 
Section XI.A.1.i.b, as it additionally provides ``[i]nformation 
necessary to determine the identity, amount, frequency, concentration, 
or other characteristics (to the extent related to air quality) of the 
emissions which, under an applicable standard or limitation, the source 
was authorized to emit (including, to the extent necessary for such 
purposes, a description of the manner or rate of operation of the 
source)[.]'' \554\
---------------------------------------------------------------------------

    \553\ 40 CFR 2.301(a)(2)(i)(A).
    \554\ 40 CFR 2.301(a)(2)(i)(B) and (C).
---------------------------------------------------------------------------

    As noted throughout this section, the information included in the 
categories identified as paragraph A information also meet another 
prong of the definition of emission data.\555\ See Section XI.A.1.i.b 
for our discussion of why this information is also emission data as 
defined at 40 CFR 2.301(a)(2)(i)(B). See Section XI.A.1.i.c for our 
discussion of why this information is also emission data as defined at 
40 CFR 2.301(a)(2)(i)(C).
---------------------------------------------------------------------------

    \555\ 40 CFR 2.301(a)(2)(i)(B).
---------------------------------------------------------------------------

    iii. Information necessary to determine the identity, amount, 
frequency, concentration, or other characteristics (to the extent 
related to air quality) of the emissions which, under an applicable 
standard or limitation, the source was authorized to emit (including, 
to the extent necessary for such purposes, a description of the manner 
or rate of operation of the source).
    We are determining that information within the categories explained 
in this subsection meets the regulatory definition of emission data 
under 40 CFR 2.301(a)(2)(i)(B) because it is ``[i]nformation necessary 
to determine the identity, amount, frequency, concentration, or other 
characteristics (to the extent related to air quality) of the emissions 
which, under an applicable standard or limitation, the source was 
authorized to emit (including, to the extent necessary for such 
purposes, a description of the manner or rate of operation of the 
source)[.]'' We will refer to subparagraph (B) in the definition of 
emission data as ``paragraph B information'' throughout this section.
    The vast majority of the information we collect for certification 
and compliance fits within this subparagraph of the definition of 
emission data. We determine that the following categories are paragraph 
B information and not entitled to confidential treatment:
    (1) Certification and compliance information,
    (2) ABT credit information,
    (3) fleet value information,
    (4) production volumes,
    (5) test information and results,
    (6) defect and recall information, and
    (7) SEA compliance information.
    These categories are summarized here and described in more detail 
in the following discussion. Certification and compliance information 
category includes information that is submitted in manufacturers' 
certificate of conformity applications and information reported after 
the certificate is issued to ensure compliance with both the 
certificate and the applicable standards, which is required under EPA's 
regulation. ABT credit information shows whether a manufacturer 
participating in an ABT program has complied with the applicable 
regulatory standards. Additionally, fleet value information is 
collected by EPA to calculate average and total emissions for a fleet 
of sources, thereby demonstrating compliance with the applicable 
regulatory standards when a manufacturer participates in an ABT program 
or for fleet averaging programs. A portion of the test and test result 
category of information is distinguishable under the paragraph A 
information basis. This portion of the test information and results 
category includes information that explains how the tests and test 
results demonstrate compliance with the applicable standards and is 
identified and discussed in this section. The test information and 
results described in Section XI.A.1.i.a is also necessary to understand 
whether a source complies with the applicable standard-setting parts. 
The SEA compliance information category includes information related to 
understanding how the results of the SEA reflect whether a source 
complies with the applicable standard-setting parts. Consistent with 40 
CFR 2.301(a)(2)(ii), under this determination, we will not release 
information included in an application for certification prior to the 
introduction-into-commerce-date, except under the limited circumstances 
already provided for in that regulatory provision.
    These categories apply to information submitted for certification 
and compliance reporting across the standard-setting parts. These 
categories make up the largest amount of information addressed by the 
confidentiality determinations.
    Certification and Compliance Information: Once EPA certifies a 
source as conforming to applicable emission standards (i.e., the source 
has a certificate of conformity), all sources the manufacturer produces 
under that certificate must conform to the requirements of the 
certificate for the useful life of the source. In short, a source's 
compliance is demonstrated against the applicable certificate of 
conformity through inspection and testing conducted by EPA and the 
manufacturers. Therefore, certification and compliance information 
falls under subparagraph B of emission data because it is ``necessary 
to determine the identity, amount, frequency, concentration, or other 
characteristic (to the extent related to air quality) of the emissions 
which, under an applicable standard or limitation, the source was 
authorized to emit (including, to the extent necessary for such 
purposes, a description of the manner or rate of operation of the 
source)[.]'' \556\ The certification and compliance information 
category includes models and parts information, family determinants, 
general emission control system information, and certificate request 
information (date, requester, etc.), contact names, importers, agents 
of service, and ports of entry used. The models and parts information 
is necessary to determine that the sources actually manufactured 
conform to the specifications of the certificate. Lastly, certificate 
request information is general information necessary to identify the

[[Page 4439]]

applicable certificate of conformity for a source, as well as 
understanding the timing and processing of the request. For these 
reasons, we are determining certificate information is emission data 
because it is necessary to determine whether a source has achieved 
compliance with the applicable standards.\557\ Note, also, that a 
portion of the category of certification and compliance information 
meets another basis in the emission data definition, as discussed in 
more detail in Section XI.A.1.i.c, as it additionally provides ``[a] 
general description of the location and/or nature of the source to the 
extent necessary to identify the source and to distinguish it from 
other sources (including, to the extent necessary for such purposes, a 
description of the device, installation, or operation constituting the 
source).'' \558\
---------------------------------------------------------------------------

    \556\ Id.
    \557\ Id.
    \558\ 40 CFR 2.301(a)(2)(i)(C).
---------------------------------------------------------------------------

    ABT Credit Information: ABT programs are an option for compliance 
with certain emissions standards. In ABT programs, manufacturers may 
generate credits when they certify that their vehicles, engines, and 
equipment achieve greater emission reductions than the applicable 
standards require. ``Averaging'' within ABT programs means exchanging 
emission credits between vehicle or engine families within a given 
manufacturer's regulatory subcategories and averaging sets. This can 
allow a manufacturer to certify one or more vehicle or engine families 
within the same averaging set at levels higher than the applicable 
numerical emission standard under certain regulatory conditions. The 
increased emissions over the otherwise applicable standard would need 
to be offset by one or more vehicle or engine families within that 
manufacturer's averaging set that are certified lower than the same 
emission numerical standard, such that the average emissions from all 
the manufacturer's vehicle or engine families, weighted by engine 
power, regulatory useful life, and production volume, are at or below 
the numerical level required by the applicable standards. ``Banking'' 
means the retention of emission credits by the manufacturer for use in 
future model year averaging or trading. ``Trading'' means the exchange 
of emission credits between manufacturers, which can then be used for 
averaging purposes, banked for future use, or traded again to another 
manufacturer. The ABT credit information category includes a 
manufacturer's banked credits, transferred credits, traded credits, 
total credits, credit balance, and annual credit balance. Because 
manufacturers participating in ABT programs use credits to demonstrate 
compliance with the applicable standards, ABT information is 
``necessary to determine the identity, amount, frequency, 
concentration, or other characteristic (to the extent related to air 
quality) of the emissions which, under an applicable standard or 
limitation, the source was authorized to emit (including, to the extent 
necessary for such purposes, a description of the manner or rate of 
operation of the source)[.]'' \559\ For these reasons, we determine ABT 
credit information is emission data because it is necessary to 
determine whether a source has achieved compliance with the applicable 
standards.\560\
---------------------------------------------------------------------------

    \559\ 40 CFR 2.301(a)(2)(i)(B).
    \560\ Id.
---------------------------------------------------------------------------

    Fleet Value Information: ABT credit information must be reviewed by 
EPA in conjunction with the fleet value information, which underlies a 
manufacturer's credit balance. The two categories are distinct from 
each other, though the information under the two categories is closely 
related. In addition to reasons described in Section XI.A.1.i.a, 
manufacturers submit fleet value information also used for compliance 
reporting under ABT programs, though some fleet value information is 
collected during certification for the on-highway sectors. The fleet 
value information category includes: Source classification, averaging 
set, engine type or category, conversion factor, engine power, payload 
tons, intended application, advanced technology (``AT'') indicator, AT 
CO2 emission, AT improvement factor, AT CO2 
benefit, innovative technology (``IT'') indicator, IT approval code, 
and IT CO2 improvement factor. Additionally, the fleet value 
information category includes the following for light-duty vehicles and 
engines, non-road SI engines, and products subject to evaporative 
emission standards: Total area of the internal surface of a fuel tank, 
adjustment factor, and deterioration factor. Fleet value information is 
used in ABT programs to explain and support a manufacturer's ABT credit 
balance. For the standard-setting parts that require a fleet average 
compliance value, the fleet value information is used to demonstrate 
compliance with the applicable standard setting parts. For these 
reasons, we are determining that the fleet value information category 
is emission data because it is information necessary to understand the 
ABT compliance demonstration and compliance with the fleet average 
value, as applicable.\561\ Additionally, a portion of the fleet value 
information is emission data, as described in Section XI.A.1.i.a, 
because it is ``necessary to determine the identity, amount, frequency, 
concentration, or other characteristics (to the extent related to air 
quality) of any emission which has been emitted by the source (or of 
any pollutant resulting from any emission by the source), or any 
combination of the foregoing[.]'' \562\
---------------------------------------------------------------------------

    \561\ Id.
    \562\ 40 CFR 2.301(a)(2)(i)(A).
---------------------------------------------------------------------------

    Production Volumes: The production volume category is emission data 
because it is necessary to determine compliance with the standards when 
a manufacturer meets requirements in an ABT credit, PLT, or in-use 
testing program, and also for GHG fleet compliance assessment. When a 
manufacturer is subject to these programs, the production volume is 
necessary to determine whether that manufacturer has complied with the 
applicable standards and limitations. In ABT programs, the averages 
used to calculate credit balances are generated based on the production 
volumes of the various families certified. For GHG standards 
compliance, manufacturers generally comply based on their overall fleet 
average, therefore, the production volume is necessary to calculate the 
fleet average and whether the manufacturers' fleet complies with the 
applicable standards. For these reasons, production volume information 
is necessary to understanding the calculations behind a manufacturer's 
credit generation and use, as well as a manufacturer's fleet average, 
which are then used to demonstrate compliance with the applicable 
standards.\563\ Additionally, for PLT and in-use testing, production 
volumes are used to determine whether and how many sources are required 
to be tested or, in some cases, whether the testing program needs to be 
undertaken at all. In this way, production volume is tied to compliance 
with the PLT and in-use testing requirements and is paragraph B 
information necessary for demonstrating compliance with an applicable 
standard. Note, that the production volume category is emission data 
for multiple reasons, as discussed in Sections XI.A.1.i.a and 
XI.A.1.i.c.
---------------------------------------------------------------------------

    \563\ 40 CFR 2.301(a)(2)(i)(B).
---------------------------------------------------------------------------

    Test Information and Results: The test information and results 
category includes the testing conducted by manufacturers and is 
necessary to demonstrate that the test parameters meet the requirements 
of the regulations. This ensures that the test

[[Page 4440]]

results are reliable and consistent. If a test does not meet the 
requirements in the applicable regulations, then the results cannot be 
used for certification or compliance purposes. The parameters and 
underlying information of an emissions test is information necessary to 
understanding the test results themselves. Adjustable parameter 
information is necessary to understand the tests used to certify a 
source and, therefore, also necessary to understand the test results 
and whether the source achieved compliance with the applicable 
standard. For these reasons, we are determining that the test 
information and results category is ``necessary to determine the 
identity, amount, frequency, concentration, or other characteristic (to 
the extent related to air quality) of the emissions which, under an 
applicable standard or limitation, the source was authorized to emit 
(including, to the extent necessary for such purposes, a description of 
the manner or rate of operation of the source[.]'' \564\ Test 
information and results collected under the standard-setting parts 
includes the following: Test temperature, adjustable test parameters, 
exhaust emission standards and family emission limits (FELs), emission 
deterioration factors, fuel type used, intended application, CO 
standard, particulate matter (``PM'') standard, NOX + HC 
standard, NOX standard, HC standard, CO2 
alternate standard, alternate standard approval code, CO2 
family emission limit (``FEL''), CO2 family certification 
level (``FCL''), NOX and NMHC + NOX standard, 
NOX and NMHC + NOX alternate standard, 
N2O standard, N2O FEL, CH4 standard, 
CH4 FEL, NOX or NMHC + NOX FEL, PM 
FEL, test number, test time, engine configuration, green engine factor, 
the test article's service hours, the deterioration factor type, test 
location, test facility, the manufacturer's test contact, fuel test 
results, vehicle mileage at the start of the test, exhaust 
aftertreatment temperatures, engine speed, engine brake torque, engine 
coolant temperature, intake manifold temperature and pressure, throttle 
position, parameter sensed, emission-control system controlled, fuel-
injection timing, NTE threshold, limited testing region, meets vehicle 
pass criteria (i.e., whether the test passes the applicable emission 
standard), number of engines tested, number of engines still needing to 
be tested, number of engines passed, purpose of diagnostics, instances 
for OBD illuminated or set trouble codes, instance of misfuelling, 
incomplete or invalid test information, the minimum tests required, 
diagnostic system, and the number of disqualified engines. For the 
reasons given, we are determining that test information and results is 
emission data because it is both necessary to understand how the source 
meets the applicable standards, including, but not limited to, ABT 
compliance demonstrations, and to ensure a source is complying with its 
certificate of conformity.\565\ Additionally, a portion of the 
information included in the test information and results category is 
emissions data under another subsection of the regulatory definition of 
emissions data, as discussed in more detail in Section XI.A.1.i.a, as 
it is also ``[i]nformation necessary to determine the identity, amount, 
frequency, concentration, or other characteristics (to the extent 
related to air quality) of any emission which has been emitted by the 
source (or of any pollutant resulting from any emission by the source), 
or any combination of the foregoing[.]'' \566\
---------------------------------------------------------------------------

    \564\ Id.
    \565\ Id.
    \566\ 40 CFR 2.301(a)(2)(i)(A).
---------------------------------------------------------------------------

    Defect and Recall Information: We are determining that the defect 
and recall information category is emission data and not entitled to 
confidential treatment because it is information necessary to determine 
compliance with an applicable standard or limitation.\567\ The only 
defects and recalls that manufacturers are required to report to EPA 
are ones that impact emissions or could impact emissions. Therefore, if 
a defect is reported to us, it is because it causes or may cause 
increased emissions and information relating to that defect is 
necessarily emission data, as it directly relates to the source's 
compliance with an applicable standard. The defect and recall 
information category, including information collected under the 
standard-setting parts, includes: System compliance reporting type, EPA 
compliance report name, manufacturer compliance report, manufacturer 
compliance report identifier, contact identifier, process code, 
submission status, EPA submission status and last modified date, 
submission creator, submission creation date, last modified date, last 
modified by, EPA compliance report identifier, compliance report type, 
defect category, defect description, defect emissions impact estimate, 
defect remediation plan explanation, drivability problems description, 
emission data available indicator, OBD MIL illumination indicator, 
defect identification source/method, plant address where defects were 
manufactured, certified sales area, carline manufacturer code, 
production start date, defect production end date, total production 
volume of affected engines or vehicles, estimated or potential number 
of engines or vehicles affected, actual number identified, estimated 
affected percentage, make, model, additional model identifier, specific 
displacement(s) impacted description, specific transmission(s) impacted 
description, related defect report indicator, related EPA defect report 
identifier, related defect description, remediation description, 
proposed remedy supporting information, description of the impact on 
fuel economy of defect remediation, description of the impact on 
drivability from remediation, description of the impact on safety from 
remediation, recalled source description, part availability method 
description, repair performance/maintenance description, repair 
instructions, nonconformity correction procedure description, 
nonconformity estimated correction date, defect remedy time, defect 
remedy facility, owner demonstration of repair eligibility description, 
owner determination method description, owner notification method 
description, owner notification start date, owner notification final 
date, number of units involved in recall, calendar quarter, calendar 
year, quarterly report number, related EPA recall report/remedial plan 
identifier, number of sources inspected, number of sources needing 
repair, number of sources receiving repair, number of sources 
ineligible due to improper maintenance, number of sources ineligible 
for repair due to exportation, number of sources ineligible for repair 
due to theft, number of sources ineligible for repair due to scrapping, 
number of sources ineligible for repair due to other reasons, 
additional owner notification indicator, and the number of owner 
notifications sent. We are not including defect investigation reports 
in this category, instead the part 2 process will continue to apply as 
described in Section XI.A.1.iv for defect investigation reports. 
Additionally, a portion of the information included in this category is 
emissions data under another subsection of the regulatory definition of 
emissions data, as discussed in more detail in Section XI.A.1.i.a, as 
it is also ``[i]nformation necessary to determine the identity, amount, 
frequency, concentration, or other characteristics (to the extent 
related to air quality) of any emission which has been emitted by the 
source (or of any pollutant resulting

[[Page 4441]]

from any emission by the source), or any combination of the 
foregoing[.]'' \568\
---------------------------------------------------------------------------

    \567\ 40 CFR 2.301(a)(2)(i)(B).
    \568\ 40 CFR 2.301(a)(2)(i)(A).
---------------------------------------------------------------------------

    SEA Compliance Information: We are determining that the SEA 
compliance information category is emission data because it is 
necessary to determine whether a source complies with its certificate 
and the standards. This category includes the facility name and 
location where the SEA was conducted, number of tests conducted, model 
year, build date, hours of operation, location of accumulated hours, 
the date the engines shipped, how the engines were stored, and, for 
imported engines, the port facility and date of arrival. This 
information collected through SEAs is necessary for determining whether 
a source that was investigated through an SEA complies with the 
applicable standards. For that reason, EPA is determining that this 
category is emission data as defined at 40 CFR 2.301(a)(2)(i)(B). 
Additionally, certain information collected during an SEA is included 
in the test information and results category. We determine that SEA 
compliance information is emission data because it is both paragraph B 
information and ``[i]nformation necessary to determine the identity, 
amount, frequency, concentration, or other characteristics (to the 
extent related to air quality) of any emission which has been emitted 
by the source (or of any pollutant resulting from any emission by the 
source), or any combination of the foregoing[.]'' \569\
---------------------------------------------------------------------------

    \569\ Id.
---------------------------------------------------------------------------

    iv. Information that is emission data because it provides a general 
description of the location and/or nature of the source to the extent 
necessary to identify the source and to distinguish it from other 
sources (including, to the extent necessary for such purposes, a 
description of the device, installation, or operation constituting the 
source).
    We are determining that certain categories of information meet the 
regulatory definition of emission data under 40 CFR 2.301(a)(2)(i)(C) 
because they convey a ``[g]eneral description of the location and/or 
nature of the source to the extent necessary to identify the source and 
to distinguish it from other sources (including, to the extent 
necessary for such purposes, a description of the device, installation, 
or operation constituting the source).'' \570\ We will refer to 
subparagraph (C) in the definition of emission data as ``paragraph C 
information'' throughout this section. We are determining that two 
categories of information fall primarily under this regulatory 
definition of emissions data: (1) Source family information, and (2) 
production volume information. We determine these categories are 
paragraph C information and are, therefore, emission data and not 
entitled to confidential treatment. However, under this determination, 
consistent with 40 CFR 2.301(a)(2)(ii), we will not release information 
included in an application for certification prior to the introduction-
into-commerce-date, except under the limited circumstances already 
provided for in that regulatory provision.
---------------------------------------------------------------------------

    \570\ 40 CFR 2.301(a)(2)(i)(C).
---------------------------------------------------------------------------

    Source Family Information: The information included in the source 
family information category includes engine family information, vehicle 
family information, evaporative family information, equipment family 
information, subfamily name, engine family designation, emission family 
name, and test group information. The engine, vehicle, and evaporative 
family information includes information necessary to identify the 
emission source for which the certificate was issued; this determines 
the emission standards that apply to the source and distinguishes the 
source's emissions from other sources. Manufacturers request 
certification using the family name of the engines, vehicles, or 
equipment they intend to produce for sale in the United States. Test 
group information identifies the sources tested and covered by a 
certificate. The source family is the basic unit used to identify a 
group of sources for certification and compliance purposes. The source 
family is a code with 12 digits that identifies all parts of that 
source. More specifically, information conveyed in the source family 
code include the model year, manufacturer, industry sector, engine 
displacement, and the manufacturer's self-designated code for the 
source family. We are determining that the source family information 
category of information is emission data because it is information that 
provides a ``[g]eneral description of the location and/or nature of the 
source to the extent necessary to identify the source and to 
distinguish it from other sources (including, to the extent necessary 
for such purposes, a description of the device, installation, or 
operation constituting the source).'' \571\
---------------------------------------------------------------------------

    \571\ 40 CFR 2.301(a)(2)(i)(C).
---------------------------------------------------------------------------

    Production Volume: Additionally, we are determining that production 
volume is emission data necessary to identify the source. Where the 
source is each individual engine, vehicle, or equipment produced, the 
production volume provides information necessary for EPA or the public 
to identify that source (the certificate only identifies one source, 
where the production volume identifies all the sources) and distinguish 
that source's emissions from the emissions of other sources. In other 
words, actual production volume provides necessary information to 
identify the number of sources operating under a certificate of 
conformity and distinguish their total emissions from other sources. In 
this way, the total number of sources operating under a certificate of 
conformity provides a ``[g]eneral description . . . of nature of the 
source'' or, alternatively, provides information necessary such that 
the source can be identified in total, since it is generally unlikely 
that only a single unit of any engine, vehicle, or equipment would be 
produced under a certificate. For this additional reason, we determine 
that the production volume category is emission data, not only for the 
reasons provided in Sections X.A.1.i.a and b, but also because it also 
provides a ``[g]eneral description of the location and/or nature of the 
source to the extent necessary to identify the source and to 
distinguish it from other sources (including, to the extent necessary 
for such purposes, a description of the device, installation, or 
operation constituting the source).'' \572\
---------------------------------------------------------------------------

    \572\ Id.
---------------------------------------------------------------------------

    v. Information submitted as preliminary and superseded will have 
the same confidentiality treatment as the final reported information.
    In the course of certifying and demonstrating compliance, 
manufacturers may submit information to EPA before the applicable 
deadline, and may update or correct that information before the 
deadline for certification or compliance reporting. Similarly, 
manufacturers routinely update their applications for certification to 
include more or different information. EPA treats this information as 
an Agency record as soon as it is received through the Engine and 
Vehicle Certification Information System (EVCIS). We are applying the 
same confidentiality determinations to this ``early'' information by 
category as we are making for the information included in the final 
certification request or compliance report in the categories generally. 
EPA generally does not intend to publish or release such preliminary or 
superseded information, because we believe the inclusion of preliminary 
information in Agency publications could lead to an inaccurate or 
misleading understanding of emissions or of a manufacturer's compliance 
status. However, because

[[Page 4442]]

such early information becomes an Agency record upon receipt, we may be 
obligated to release information from those preliminary or superseded 
documents that is not entitled to confidential treatment if a requester 
specifically requests such pre-final information in a FOIA request. In 
such circumstances, we intend to provide a statement regarding the 
preliminary or superseded nature of the information in the final FOIA 
response. EPA also does not intend to disclose information in submitted 
reports until we have reviewed them to verify the reports' accuracy, 
though the Agency may be required to release such information if it is 
specifically requested under the FOIA. Note that this subsection's 
determinations and intended approaches for preliminary and superseded 
information submitted as part of the certification and compliance 
reporting processes apply only to such information for those categories 
of information where we are making confidentiality determinations in 
this final rule. In other words, this subsection is not intended to 
address preliminary or projected information for the types of 
information we are not including in the determinations made in this 
final rule and that remain subject to the part 2 process (see Section 
XI.A.1.iv).
    vi. Information that is never entitled to confidential treatment 
because it is publicly available or discernible information or becomes 
public after a certain date.
    We are also determining that information that is or becomes 
publicly available under the applicable standard-setting parts is not 
entitled to confidential treatment by EPA. Information submitted under 
the standard-setting parts generally becomes publicly available in one 
of two ways: (1) Information is required to be publicly disclosed under 
the standard-settings parts, or (2) information becomes readily 
measurable or observable after the introduction-to-commerce date. 
Information that is required to be publicly available under the 
standard-setting parts includes: Information contained in the fuel 
economy label, the vehicle emission control information (``VECI'') 
label, the engine emission control information label, owner's manuals, 
and information submitted by the manufacturer expressly for public 
release. The information in the labels is designed to make the public 
aware of certain emissions related information and thus is in no way 
confidential. Similarly, manufacturers submit documents specifically 
prepared for public disclosure to EPA with the understanding that they 
are intended for public disclosure. We determine that these public 
facing documents are not entitled to confidential treatment, as they 
are prepared expressly for public availability.
    Additionally, we are determining that the types of information 
provided in the next paragraph that are measurable or observable by the 
public after the source is introduced into commerce are not entitled to 
confidential treatment by EPA after the introduction-to-commerce date. 
This information may also be emission data and included in the one of 
the categories established in this action, accordingly, we determine 
that it is emission data as described in Section XI.A.1.i. The fact 
that this information is or becomes publicly available is an additional 
reason for it to be not entitled to confidential treatment after the 
introduction into commerce date, and is an independent alternative 
basis for our determination that the information is not entitled to 
confidential treatment.
    This information includes: Model and parts information, source 
footprint information, manufacturer, model year, category, service 
class, whether the engine is remanufactured, engine type/category, 
engine displacement, useful life, power, payload tons, intended 
application, model year, fuel type, tier, and vehicle make and model. 
Footprint information is readily observable by the public after the 
introduction-to-commerce date, as one can measure and calculate that 
value once the source is introduced into commerce. Additionally, models 
and parts information is also readily available to the public after the 
source is introduced into commerce. Because this information is 
publicly available, it is not entitled to confidential treatment. 
Therefore, we will not provide any additional notice or process prior 
to releasing these type of information in the future.
    vii. Information not included in this rule's determinations will be 
treated as confidential, if the submitter claimed it as such, until a 
confidentiality substantiation is submitted and a determination made 
under the 40 CFR part 2 process.
    We are not making a confidentiality determination under 40 CFR 
1068.11 for certain information submitted to EPA for certification and 
compliance. This information, if claimed as confidential by the 
submitters, will be treated by EPA as confidential until such time as 
it is requested under the FOIA or EPA otherwise goes through a case-by-
case or class determination process under 40 CFR part 2. At that time, 
we will make a confidentiality determination in accordance with 40 CFR 
part 2, and as established in this rulemaking under 40 CFR 2.301(j)(4). 
This final action supersedes the Table 3 CBI class determinations that 
EPA previously made in 2013, such that the same categories of 
information in Table 3 will not have an applicable class determination 
and will now be subject to the 40 CFR part 2 process.
    The types of information we are not including in the determinations 
made in this final rule, and remain subject to the part 2 process, 
includes:
    (1) Projected production and sales,
    (2) Production start and end dates outside of the defect and recall 
context,
    (3) Specific and detailed descriptions of the emissions control 
operation and function,
    (4) Design specifications related to aftertreatment devices,
    (5) Specific and detailed descriptions of auxiliary emission 
control devices (AECDs),
    (6) Plans for meeting regulatory requirements (e.g., ABT pre-
production plans),
    (7) Procedures to determine deterioration factors and other 
emission adjustment factors and any information used to justify those 
procedures,
    (8) Financial information related to ABT credit transactions 
(including dollar amount, parties to the transaction and contract 
information involved) and manufacturer bond provisions (including 
aggregate U.S. asset holdings, financial details regarding specific 
assets, whether the manufacturer or importer obtains a bond, and copies 
of bond policies),
    (9) Serial numbers or other information to identify specific 
engines or equipment selected for testing,
    (10) Procedures that apply based on the manufacturers request to 
test engines or equipment differently than we specify in the applicable 
standard-setting parts,
    (11) Information related to testing vanadium catalysts in 40 CFR 
part 1065, subpart L (established in this rule),
    (12) GPS data identifying the location and route for in-use 
emission testing, and
    (13) Defect investigation reports. The information contained in 
defect investigation reports may encompass both emission data and 
information that may be CBI, so we are not making a determination for 
this report as whole. Instead, procedurally we will treat these reports 
in accordance with the existing part 2 process.
    Additionally, we are creating a category of information to include 
information EPA received through

[[Page 4443]]

``comments submitted in the comment field,'' where the Agency's 
compliance reporting software has comment fields to allow manufacturers 
to submit clarifying information in a narrative format. We are not 
making a determination on this broad category of potential information 
at this time, as the narrative comments may or may not contain emission 
data. Therefore, EPA will undertake a case-by-case determination 
pursuant to 40 CFR part 2 for any information provided in a comment 
field. As explained earlier in this subsection, after further 
consideration, this final action supersedes the Table 3 CBI class 
determination made in 2013 and EPA is also not making a determination 
at this time regarding whether the information in Table 3 of the 2013 
determination may meet the definition of emission data or otherwise may 
not be entitled to confidential treatment in certain circumstances 
under individual standard-setting parts, and instead thinks that a 
case-by-case determination process is better suited to these categories 
of information.
2. Adjustable Parameters
    One of the goals of the certification process is to ensure that the 
emission controls needed to meet emission standards cannot be bypassed 
or rendered inoperative. Consistent with this goal, the standard-
setting parts generally require that engines, vehicles, and equipment 
with adjustable parameters meet all the requirements of part 1068 for 
any adjustment in the physically adjustable range. This applies for 
testing pre-production engines, production engines, and in-use engines.
    The underlying principles of the current regulations and policy can 
be traced to the early emission standards for mechanically controlled 
engines. The regulations at 40 CFR 86.094-22(e) illustrate how the 
relevant provisions currently apply for heavy-duty highway engines. The 
earliest generation of engines with emission control technology subject 
to emission standards included components such as simple screws to 
adjust a variety of engine operating parameters, including fuel-air 
ratio and idle speed. Owners were then able to adjust the engines based 
on their priority for power, efficiency, or durability. At the same 
time, manufacturers sought to reduce emissions by limiting the physical 
range of adjustment of these parameters, so EPA developed regulations 
to ensure that the engines' limitations were sufficiently robust to 
minimize operation outside the specified range (48 FR 1418, January 12, 
1983).
    Since then, heavy-duty highway engine manufacturers have developed 
new technologies that did not exist when we adopted the existing 
regulations related to adjustable parameters. The regulations at 40 CFR 
86.094-22(e) therefore provide a limited framework under which to 
administer the current certification for heavy-duty highway engines. 
Current certification practice consists of applying these broad 
principles to physically adjustable operating parameters in a way that 
is similar for both highway and nonroad applications. EPA developed 
guidance with detailed provisions for addressing adjustable parameters 
at certification for land-based nonroad spark-ignition engines at or 
below 19 kW.\573\ To date, programmable operating parameters have 
generally not been treated as adjustable parameters for Federal 
regulatory purposes, except that manufacturers need to identify all 
available operating modes (such as eco-performance or rabbit/turtle 
operation).
---------------------------------------------------------------------------

    \573\ ``Clean Air Act Requirements for Small Nonroad Spark-
Ignition Engines: Reporting Adjustable Parameters and Enforcement 
Guidance,'' EPA Guidance CD-12-11 (Small SI Guidance), August 24, 
2012.
---------------------------------------------------------------------------

    EPA's Office of Enforcement and Compliance Assurance (OECA) has 
found extensive evidence of tampering with the electronic controls on 
heavy-duty engines and vehicles nationwide, although EPA lacks robust 
data on the exact rate of tampering.\574\ Recently, OECA announced a 
new National Compliance Initiative (``NCI'') to address the 
manufacture, sale, and installation of defeat devices on vehicles and 
engines through civil enforcement.\575\ Section VI.C includes a 
discussion on the potential for significant increases in emissions from 
tampering with current heavy-duty engines, and the provisions in the 
final rule that we expect will reduce incentives to tamper with model 
year 2027 and later heavy-duty engines.
---------------------------------------------------------------------------

    \574\ U.S. EPA. ``Tampered Diesel Pickup Trucks: A Review of 
Aggregated Evidence from EPA Civil Enforcement Investigations'', 
November 20, 2021, Available online: https://www.epa.gov/enforcement/tampered-diesel-pickup-trucks-review-aggregated-evidence-epa-civil-enforcement.
    \575\ U.S. EPA. National Compliance Initiative: Stopping 
Aftermarket Defeat Devices for Vehicles and Engines. Available 
online: https://www.epa.gov/enforcement/national-compliance-initiative-stopping-aftermarket-defeat-devices-vehicles-and-engines.
---------------------------------------------------------------------------

    Manufacturers are required by existing regulations to describe in 
their application for certification how they address potentially 
adjustable operating parameters. As with all elements of certification, 
the regulations require manufacturers to use good engineering judgment 
for decisions related to adjustable parameters. The regulations also 
describe a process for manufacturers to ask for preliminary approval 
for decisions related to new technologies, substantially changed engine 
designs, or new methods for limiting adjustability. See, for example, 
40 CFR 1039.115 and 1039.210. Note that the certification requirements 
described in this section for manufacturers apply equally to anyone 
certifying remanufactured engines or associated remanufacturing systems 
where such certification is required.
    We are adopting a new 40 CFR 1068.50 to update the current 
regulatory provisions such that the established principles and 
requirements related to adjustable parameters also apply for current 
technologies. Thus, the new provisions indicate how our established 
principles regarding adjustable parameters apply for the full range of 
emission control technologies.
    The provisions are largely based on regulations that already apply 
for highway engines and vehicles under 40 CFR 86.094-22(e) and 86.1833-
01. Most of what we are adopting in 40 CFR 1068.50 is an attempt to 
codify in one place a set of provisions that are consistent with 
current practice. Some provisions may represent new or more detailed 
approaches, as described further in the following paragraphs, 
especially in the context of electronic controls. The provisions in the 
final 40 CFR 1068.50 are intended to apply broadly across EPA's engine, 
vehicle, and equipment programs. The language is intended to capture 
the full range of engine technologies represented by spark-ignition and 
compression-ignition engines used in highway, nonroad, and stationary 
applications. We are accordingly applying the new provisions for all 
the types of engines, vehicles and equipment that are broadly subject 
to 40 CFR part 1068, as described in 40 CFR 1068.1. For example, the 
provisions apply for nonroad sectors and for heavy-duty highway 
engines, but not for highway motorcycles or motor vehicles subject to 
standards under 40 CFR part 86, subpart S. Note that regulatory 
provisions for adjustable parameters refer to engines, because most 
adjustable parameters are integral to the engine and its controls. In 
the case of equipment-based standards and alternative power 
configurations such as electric vehicles, the requirement to meet 
emission standards across the physically adjustable range. As with 
other provisions in 40 CFR part 1068, if the standard-setting part 
specifies some

[[Page 4444]]

provisions that are different than 40 CFR 1068.50, the provisions in 
the standard-setting part apply instead of the provisions in 40 CFR 
1068.50. For example, we will continue to rely on the provisions 
related to adjusting air-fuel ratios in 40 CFR part 1051 for 
recreational vehicles in addition to the new provisions from 40 CFR 
1068.50. In this final rule, we are also making some minor adjustments 
to the regulatory provisions in the standard-setting parts to align 
with the language in 40 CFR 1068.50.
    The regulations in this final rule include several changes from the 
proposed rule. We have added the word ``significant'' as a qualifying 
term for the amount of emissions impact required from the adjustment of 
an operating parameter for an operating parameter to be considered an 
adjustable parameter. This term was missed in the proposed migration of 
adjustable parameter language from 40 CFR 86.094-22(e)(1)(ii) to 40 CFR 
1068.50. We have also updated the language and organization of 40 CFR 
1068.50 to make the regulation easier to read. This update in language 
is not meant to change the meaning of the terms, only to provide 
greater consistency in the intent of our regulation. We did this by 
changing ``mechanically controlled parameter'' to ``physically 
adjustable parameter'' and ``electronically controlled parameter'' to 
``programmable parameter''. We updated our terminology of tools used to 
determine whether operating parameters are considered practically 
adjustable by changing from ``simple tools'' to ``ordinary tools''. We 
also updated the list of ordinary tools to be a specific list of tools 
used in their intended manner for engines less 30 kW, expanding this 
list for 30-560 kW engines, and allowing any available tools for 
engines above 560 kW. We did this to stay consistent with the existing 
Small SI Guidance. We added a time limit for determining whether 
operating parameters are considered practically adjustable for engines 
above 560 kW as it would be unreasonable to allow an unlimited amount 
of time for a mechanic to modify an engine in this determination. We 
have updated 40 CFR 1068.50 to address crimped fasteners and bimetal 
springs and removed the limitation of only applying the physically 
adjustable parameter requirements of crimped fasteners and bimetal 
springs to mechanically controlled engines since bimetal springs and 
crimped fasteners are not limited in use to mechanically controlled 
engines. To remain consistent with the Small SI Guidance, we have added 
extraordinary measures as an exception for determining the practical 
adjustability of an operating parameter. We have also added removal of 
cylinder heads as an extraordinary measure as any modification of 
internal engine components requires specialty knowledge and there can 
be a high degree of difficulty in removing cylinder heads. To address 
concerns about listing all programmable variables as operating 
parameters, which could affect thousands of different control 
strategies, we will allow all programmable parameters not involving 
user-selectable controls to be a single, collective operating 
parameter. We have removed the requirement for potting or encapsulating 
circuit boards in a durable resin as a requirement for tamper-proofing 
programmable controls since anyone tampering with programmable controls 
would almost certainly accomplish that as a software change through 
reflashing rather than modifying circuit boards directly. We have 
adjusted the date for implementing the new adjustable-parameter 
provisions as described in the next section. See the Response to 
Comments for a more thorough discussion of the comments.
i. Lead Time
    We proposed to apply the adjustable-parameter requirements of 40 
CFR 1068.50 starting in model year 2024. This short lead time was based 
on (1) the expectation that the new regulation was only modestly 
different than existing requirements for physically adjustable 
operating parameters and (2) the proposed requirements for programmable 
operating parameters were intended to substantially align with 
manufacturers' current and ongoing efforts to prevent in-use tampering. 
Considering these factors, we -proposed model year 2024 to provide a 
short lead time that would be sufficient for manufacturers. This lead 
time would also allow EPA time to prepare internal processes for 
handling the additional information.
    As detailed in the Response to Comments document, the Truck and 
Engine Manufacturers Association, the Outdoor Power Equipment 
Institute, and Cummins suggested that the final rule should allow more 
time to comply with the new requirements.
    We are revising the final rule from the proposal to specify that 
the final adjustable-parameter provisions in 40 CFR 1068.50 start to 
apply in model year 2027. Until then, manufacturers may optionally 
comply with 40 CFR 1068.50 early, but will otherwise continue to be 
subject to adjustable parameter provisions as established for each 
standard-setting part.
    Our starting expectation is that EPA and manufacturers have a 
mutual interest in preventing tampering with in-use engines. We also 
understand, as described further in this section, that it is not 
possible to adopt a single standard for tamper-proofing electronic 
controls that will continue to be effective years into the future. 
Discussion of the certification process in section XI.A.2.iii therefore 
clarifies that EPA reviewers intend to consider the totality of the 
circumstances as we determine whether a manufacturer's effort to 
prevent inappropriate in-use adjustments is adequate. That 
consideration may involve, for example, EPA assessing the most recent 
provisions adopted in voluntary consensus standards, the extent to 
which manufacturers of similar engines have taken steps to prevent 
tampering, any reports of tampering with an individual manufacturer's 
in-use engines, and the availability of replacement parts or services 
intended to bypass emission controls. EPA review of engine designs 
would account for the practical limitations of designing engine 
upgrades, both for initial approval under 40 CFR 1068.50 and for year-
by-year review of certification applications as time passes.
    As a result, we expect to work with manufacturers to establish and 
implement plans to incorporate reasonable tamper-proofing designs, 
consistent with prevailing industry practices, in a reasonable time 
frame. We understand that tying compliance to prevailing industry 
practices creates a measure of ambiguity regarding the deadline to 
comply for model year 2027. We would generally expect manufacturers to 
successfully certify based on their current and upcoming efforts to 
protect their engines from maladjustment. Some manufacturers will have 
plans for making additional changes to their engines beyond model year 
2027. We can also work with such manufacturers to plan for making those 
additional changes in later model years if, for example, their further 
technology development moves them in the direction of improving engine 
control module (ECM) security with up-and-coming designs. Manufacturers 
might also need additional time to deploy established technologies for 
niche products after implementing those improvements in their high-
volume product lines. This dynamic regarding the lead time for meeting 
requirements in model year 2027 is no different than what will apply in 
the future any time there is a development or innovation

[[Page 4445]]

that leads manufacturers to integrate the next generation of tamper-
proofing across their product line.
ii. Operating Parameters, Adjustable Parameters, and Statement of 
Adjustable Range
    The regulation establishes that operating parameters are features 
that can be adjusted to affect engine performance, and that adjustable 
parameters are operating parameters that are practically adjustable by 
a user or other person by physical adjustment, programmable adjustment, 
or regular replenishment of a fluid or other consumable material. 
However, we do not consider operating parameters to be adjustable 
parameters if the operating parameters are permanently sealed or are 
not practically adjustable, or if we determine that engine operation 
over the full range of adjustment does not affect emissions without 
also degrading engine performance to the extent that operators will be 
aware of the problem. For example, while spark plug gap and valve lash 
are operating parameters that can be adjusted to affect engine 
performance, we do not treat them as adjustable parameters because 
adjusting them does not affect emissions without also degrading engine 
performance to the extent that operators will be aware of the problem. 
The following sections describes how we consider whether parameters are 
practically adjustable.
a. Physically Adjustable Operating Parameters
    In the final 40 CFR 1068.50(e), a physically adjustable parameter 
is considered ``practically adjustable'' for engines at or below 30 kW 
if a typical user can adjust the parameter with ordinary tools within 
15 minutes using service parts that cost no more than $30.\576\ 
Similarly, a physically adjustable parameter is considered 
``practically adjustable'' for 30-560 kW engines if a qualified 
mechanic can adjust the parameter with ordinary tools within 60 minutes 
using service parts that cost no more than $60. The term ``ordinary 
tools'' is defined in the final regulations based on the size of the 
engine. For engines at or below 30 kW, the definition includes slotted 
and Phillips head screwdrivers, pliers, hammers, awls, wrenches, 
electric screwdrivers, electric drills, and any tools supplied by the 
manufacturer, where those tools are used for their intended purpose. 
For 30-560 kW engines, the definition includes all ordinary tools 
specified for engines at or below 30 kW and also includes solvents, or 
other supplies that are reasonably available to the operator and any 
other hand tools sold at hardware stores, automotive parts supply 
stores, or on the internet. These thresholds are intended to be 
consistent with the provisions that apply under current regulations but 
tailored to represent an appropriate level of deterrence relative to 
typical maintenance experiences for the different sizes of engines.
---------------------------------------------------------------------------

    \576\ The cost thresholds do not include the cost of labor or 
the cost of any necessary tools or nonconsumable supplies; the time 
thresholds refer to the time required to access and adjust the 
parameter, excluding any time necessary to purchase parts, tools, or 
supplies or to perform testing. These costs are in 2020 dollars. 
Manufacturers will adjust these values for certification by 
comparing to the most recently available Consumer Price Index for 
All Urban Consumers value published by the Bureau of Labor 
Statistics www.bls.gov/data/inflation_calculator.htm.
---------------------------------------------------------------------------

    For engines above 560 kW, a physically adjustable parameter is 
considered ``practically adjustable'' if a qualified mechanic can 
adjust the parameter using any available tools within 60 minutes. We 
are not setting a cost threshold for engines above 560 kW because of 
the very large costs for purchasing, servicing, and operating these 
engines. Owners of these low-volume, high-cost engines are more likely 
to have ready access to experienced mechanics to continuously manage 
the maintenance and performance of their engines. For example, owners 
of marine vessels often have engineers traveling with vessels to always 
be ready to perform extensive repairs or maintenance as needed. Owners 
of engines above 560 kW also commonly do their own work to 
substantially overhaul engines. We expect this arrangement for 
qualifying adjustable parameters will cause manufacturers to develop 
designs for properly limiting adjustability of engines above 560 kW.
    Physically adjustable parameters usually have physical limits or 
stops to restrict adjustability. Specific characteristics are 
identified in the final 40 CFR 1068.50(f) to illustrate how physical 
limits or stops should function to control the adjustable range. For 
example, a physical stop defines the limit of the range of 
adjustability for a physically adjustable operating parameter if 
operators cannot exceed the travel or rotation limits using the 
appropriate tools without causing damage exceeding specified 
thresholds.
    We are changing the proposed provisions in this final rule to 
include reference to extraordinary measures. We will not require 
manufacturers to extend the physically adjustable range to account for 
such extraordinary measures. The final regulation establishes the 
following steps as extraordinary measures: Removing a cylinder head 
from the engine block, fully or partially removing a carburetor, 
drilling or grinding through caps or plugs, causing damage to the 
engine or equipment that would exceed the specified time or cost 
thresholds, or making special tools to override design features that 
prevent adjustment. Note that extraordinary measures do not include 
purchase of such special tools if they become available for purchase.
b. Programmable Operating Parameters
    The final 40 CFR 1068.50(e)(2) states that programmable operating 
parameters will be considered ``practically adjustable'' if they can be 
adjusted using any available tools (including devices that are used to 
alter computer code). This will apply for engines with any degree of 
electronic control. The final 40 CFR 1068.50(e) will also include 
special provisions for determining whether electronic control modules 
that can be adjusted by changing software or operating parameters 
(``reflashed'') are practically adjustable and to determine the 
practically adjustable range. First, where any of the following 
characteristics apply for a given electronic parameter, it will be 
considered practically adjustable:
     If an engine family includes multiple operating modes or 
other algorithms that can be selected or are easily accessible, the 
operating parameter will be practically adjustable and each of the 
selectable or accessible modes or settings will be within the 
practically adjustable range.
     If the manufacturer sells software (or other tools) that 
an experienced, independent mechanic could use to reflash or otherwise 
modify the electronic control module, the operating parameter will be 
practically adjustable and all those settings will be within the 
practically adjustable range.
     If the engines/equipment have other electronic settings 
that can be adjusted using any available service tools (such as fuel 
injection maps), the operating parameter will be practically adjustable 
and all those settings will be within the practically adjustable range.
    Injection fuel maps and other similar electronic parameters will 
not be considered practically adjustable if the manufacturer adequately 
prevents access to the electronic control modules with encryption or 
password protection consistent with good engineering judgment, such as 
having adequate protections in place to prevent distribution and use of 
passwords or encryption keys. Manufacturers will be able to exclude 
electronic operating

[[Page 4446]]

parameters from being considered adjustable parameters (or identify 
them as adjustable parameters but narrow the adjustable range) where 
they appropriately determine that the operating parameters will not be 
subject to in-use adjustment; EPA retains the right to review the 
appropriateness of such statements. The final regulations also allow us 
to specify conditions to ensure that the certified configuration 
includes electronic parameter settings representing adjustable ranges 
that reflect the expected range of in-use adjustment or modification.
    To address the safety, financial liability, operational, and 
privacy concerns which can result from tampering, manufacturers, 
industry organizations, and regulators have been working to develop 
standards and design principles to improve the security of ECMs. Three 
such efforts where cybersecurity guidelines and procedures are either 
under development or already in publication are ISO/SAE J21434, UNECE 
WP29 Cybersecurity Regulation, and SAE J3061.\577\ \578\ \579\ Since 
security principles are constantly evolving as new threats are 
identified, it is impractical to codify specific requirements to be 
applied in an annual emission certification process. However, we expect 
to require manufacturers to update their tamper-resistance features 
over time to keep up with industry best practices. In addition, 
manufacturers may choose to utilize different mixes of technical 
standards or principles of those recommended by these organizations, 
and a one-size-fits-all approach with detailed requirements for ECM 
security will be neither practical nor prudent. Manufacturers need the 
flexibility to quickly implement measures to address new or emerging 
threats and vulnerabilities. Accordingly, the final regulation 
specifies that the manufacturer's application for certification must 
identify their ECM security measures. Manufacturers need to describe 
the measures they are using, whether proprietary, industry technical 
standards, or a combination of both, to prevent unauthorized access to 
the ECM. At a minimum, for determining whether the parameter is an 
operating parameter or an adjustable parameter, this documentation will 
need to describe in sufficient detail the measures that a manufacturer 
has used to prevent unauthorized access; ensure that calibration 
values, software, or diagnostic features cannot be modified or 
disabled; and respond to repeated, unauthorized attempts at 
reprogramming or tampering.
---------------------------------------------------------------------------

    \577\ ``Road vehicles--Cybersecurity engineering'', ISO/SAE FDIS 
21434, https://www.iso.org/standard/70918.html.
    \578\ United Nations Economic Commission for Europe, ``UNECE 
WP29 Automotive Cybersecurity Regulation'', Available online: 
unece.org/DAM/trans/doc/2020/wp29grva/ECE-TRANS-WP29-2020-079-Revised.pdf.
    \579\ Society of Automotive Engineers, ``Cybersecurity Guidebook 
for Cyber-Physical Vehicle Systems''. SAE J3061, Available online: 
https://www.sae.org/standards/content/j3061_201601/.
---------------------------------------------------------------------------

    Some commenters expressed a concern that state or Federal ``right 
to repair'' legislation may conflict with EPA's requirement to limit 
access to an engine's electronic controls, and one commenter suggested 
edits creating an exception in EPA's proposed regulation intended to 
address such a conflict. Commenters did not specifically identify how 
any specific existing state or Federal law conflicts with EPA's 
regulation, and we are finalizing the requirements as described in this 
section without the suggested exception. See section 30.2 of the 
Response to Comments for further detail on comments received and EPA's 
responses.
c. Aftermarket Fuel Conversions
    Aftermarket fuel conversions for heavy-duty highway engines and 
vehicles are a special case. We expect aftermarket converters to 
continue their current practice of modifying engines to run on 
alternative fuels under the clean alternative fuel conversion program 
in 40 CFR part 85, subpart F. The anti-tampering provisions in the 
final 40 CFR 1068.50 are not intended to interfere with actions 
aftermarket converters may need to take to modify or replace ECMs as 
part of the conversion process consistent with 40 CFR part 85, subpart 
F. The final provisions direct manufacturers to prevent unauthorized 
access to reprogram ECMs. Aftermarket converters will presumably need 
to either use a replacement ECM with a full calibration allowing the 
engine to run on the alternative fuel or perhaps create a piggyback ECM 
that modifies the engine's calibration only as needed to accommodate 
the unique properties of the alternative fuel. Aftermarket converters 
can alternatively work with engine manufacturers to access and change 
the engine's existing ECM programming for operation on the alternative 
fuel.
d. Consumption, Replenishment, and the Certified Configuration
    Certain elements of design involving consumption and replenishment 
may be considered adjustable parameters. Two significant examples are 
DEF tank fill level and hybrid battery state of charge. The final 
provisions in 40 CFR 1068.50(h) address these issues.
    For these adjustable parameters, the range of adjustability is 
determined based on the likelihood of in-use operation at a given point 
in the physically adjustable range. We may determine that operation in 
certain subranges within the physically adjustable range is 
sufficiently unlikely that the subranges may be excluded from the 
allowable adjustable range for testing. In such cases, the engines/
equipment are not required to meet the emission standards for operation 
in an excluded subrange.
    The final 40 CFR 1068.50(h) describes how we will not require new 
engines to be within the range of adjustability for a certified 
configuration for adjustments related to consumption and replenishment. 
Specifically, manufacturers will not violate the prohibition in 40 CFR 
1068.101(a)(1) by introducing into commerce a vehicle with an empty DEF 
tank or an uncharged hybrid battery.
    Except for these special cases related to consumption and 
replenishment, final 40 CFR 1068.50(k) specifies that engines are not 
in the certified configuration if manufacturers produce them with 
adjustable parameters set outside the range specified in the 
application for certification. Similarly, engines are not in the 
certified configuration if manufacturers produce them with other 
operating parameters that do not conform to the certified 
configuration. Such engines will therefore not be covered by a 
certificate of conformity in violation of 40 CFR 1068.101(a)(1).
iii. Certification Process
    The existing regulations in each standard-setting part describe how 
manufacturers need to identify their adjustable parameters, along with 
the corresponding physical stops and adjustable ranges. The existing 
certification process includes a review of the manufacturer's specified 
adjustable parameters, including consideration of the limits of 
adjustability. This has generally focused on physically adjustable 
parameters. Under the new regulations, we intend to consider the 
totality of the circumstances as we determine whether a manufacturer's 
effort to prevent inappropriate adjustment is adequate. See text 
further clarifying this principle in final 40 CFR 1068.50(i). Under the 
existing certification process, we may also evaluate the 
appropriateness of a manufacturer's statement regarding an adjustable 
parameter if we learn from

[[Page 4447]]

observation of in-use engines with such parameters or other information 
that a parameter was in fact practically adjustable or that the 
specified adjustable range was in fact not correct.
    We are requiring manufacturers in the certification application to 
state, with supporting justification, that they designed physically 
adjustable operating parameters to prevent in-use adjustment outside 
the intended adjustable range, that they designed physically adjustable 
parameters to prevent in-use operation outside the intended adjustable 
range, and that they have limited access to the electronic controls as 
specified in 40 CFR 1068.50 to prevent in-use adjustment of operating 
parameters and prevent in-use operation outside the intended adjustable 
range. We are clarifying in this rule that manufacturers must consider 
programmable parameters to be operating parameters that may also be 
adjustable. All operating modes available for selection by the operator 
must be described in the certification application and are considered 
adjustable parameters and fall within the engine's practically 
adjustable range; however, programmable parameters that do not involve 
user-selectable controls can be described as a single operating 
parameter. The manufacturer must describe in the certification 
application how they have restricted access to the electronic controls 
to prevent unauthorized modification of in-use engines. Manufacturers 
will need to follow accepted industry best practices to include 
password restrictions, encryption, two-step authentication, and other 
methods as appropriate. Manufacturers will need to implement those 
newer methods as practices change over time, especially where there are 
observed cases of unauthorized changes to in-use engines.
    Manufacturers must name all available operating modes in the 
application for certification and describe their approach for 
restricting access to electronic controls. This description must 
include naming any applicable encryption protocols, along with any 
additional relevant information to characterize how the system is 
designed to prevent unauthorized access. Manufacturers must separately 
identify information regarding their auxiliary emission control 
devices. Manufacturers will not need to report additional detailed 
programming information describing electronically adjustable operating 
parameters that are inaccessible to owners.
    While EPA retains the right to review the manufacturer's specified 
adjustable parameters in the certification process, the manufacturer 
will be responsible for ensuring all aspects of the manufacturer's 
statements regarding adjustable parameters are appropriate for each 
certification application. EPA may review this information each year to 
evaluate whether the designs are appropriate. As industry practices 
evolve to improve tamper-resistance with respect to electronic 
controls, manufacturers will need to upgrade tamper-resistance features 
to include more effective protocols to support their statement that the 
electronic controls are both restricted from unauthorized access and 
limited to the identified practically adjustable range.
    The provisions in 40 CFR 1068.50 are not intended to limit the 
tampering prohibition of 40 CFR 1068.101(b)(1) or the defeat-device 
prohibition of 40 CFR 1068.101(b)(2). For example, it would be 
prohibited tampering to bypass a manufacturer's stops. Similarly, 
aftermarket software that reduces the effectiveness of controls 
specified by the manufacturer in the application for certification 
would be a prohibited defeat device.
    If EPA discovers that someone manufactures or installs a modified 
ECM or reflashes an engine's ECM in a way that is not a certified 
configuration represented in the application for certification, those 
persons will be liable for violating the tampering prohibition of 40 
CFR 1068.101(b)(1) or the defeat-device prohibition in 40 CFR 
1068.101(b)(2). As we gather information about cases where third 
parties have successfully penetrated ECM access restrictions, the 
manufacturer will be responsible in each certification application for 
ensuring all aspects of the manufacturer's statements regarding such 
adjustable parameters are still appropriate and we may also engage with 
the manufacturer to see if there is need or opportunity to upgrade 
future designs for better protection.
iv. Engine Inspections
    EPA may want to inspect engines to determine if they meet the final 
specifications for adjustable parameters as described in 40 CFR 
1068.50. These inspections could be part of the certification process, 
or we could inspect in-use engines after certification. For example, we 
may request a production engine be sent to an EPA designated lab for 
inspection to test the limits of the adjustable parameters as described 
in 40 CFR 1068.50(j).
3. Exemptions for Engines, Vehicles, and Equipment Under 40 CFR Part 
1068, Subparts C and D
    40 CFR part 1068, subparts C and D, describe various exemption 
provisions for engines, vehicles and equipment that are subject to 
emission standards and certification requirements. We are amending 
several of these exemption provisions. We received no comments on the 
proposed exemption provisions and are finalizing the proposed changes 
without modification. The following paragraphs use the term engines to 
refer generically to regulated engines, vehicles, and equipment.
    The test exemption in 40 CFR 1068.210 applies for certificate 
holders performing test programs ``over a two-year period''. We are 
removing this time limitation. We may impose reasonable time limits on 
the duration of the exemption for individual engines under another 
existing provision (40 CFR 1068.210(e)). Such limitations may take the 
form of a defined time for manufacturers to produce exempt engines, or 
a defined time for individual engines to remain in exempt status. This 
exemption applies for a wide range of products and experience has shown 
that circumstances may call for the exemption to apply for longer than 
(or less than) two years. We may therefore continue to apply a two-year 
limit for producing or using exempt engines based on a case-specific 
assessment of the need for the exemption. We could alternatively 
identify a shorter or longer exemption period based on the 
circumstances for each requested exemption. The exemption approval 
could also allow test engines to operate indefinitely, perhaps with 
additional conditions on modifying the engine to include software or 
hardware changes that result from the test program or other design 
improvements. This approach may be appropriate for manufacturing one or 
more engines as part of a pilot project to prove out designs and 
calibrations for meeting new emission standards. Separate provisions 
apply for importing engines under the testing exemption in 40 CFR 
1068.325, which we discuss further later in this section.
    The display exemption in 40 CFR 1068.220 applies for using 
noncompliant engines/equipment for display purposes that are ``in the 
interest of a business or the general public.'' The regulation 
disallows the display exemption for private use, private collections, 
and any other purposes we determine to be inappropriate. We have been 
aware of several cases involving displays we may

[[Page 4448]]

have considered to be in the interest of the general public, but they 
did not qualify for the display exemption because they were mostly for 
private use. Experience has shown that it may be difficult to 
distinguish private and public displays. For example, private 
collections are sometimes shared with the general public. We are 
accordingly preserving the fundamental limitation of the display 
exemption to cases involving the interest of a business or the general 
public. We are revising 40 CFR 1068.220 to no longer categorically 
disallow the display exemption for engines and vehicles displayed for 
private use or for engines in private collections. We are retaining the 
discretion to disallow the display exemption for inappropriate 
purposes. This would apply, for example, if engines or vehicles from a 
private collection will not be displayed for the general public or for 
any business interest. Consistent with longstanding policy, such 
private displays do not warrant an exemption from emission standards.
    The regulation defines provisions that apply for ``delegated 
assembly'' of aftertreatment and other components in 40 CFR 1068.261. 
Under the current regulation, manufacturers must follow a set of 
detailed requirements for shipping partially complete engines to 
equipment manufacturers to ensure that the equipment manufacturer will 
fully assemble the engine into a certified configuration. A much 
simpler requirement applies for engine manufacturers that produce 
engines for installation in equipment that they also produce. 
Manufacturers have raised questions about how these requirements apply 
in the case of joint ventures, subsidiary companies, and similar 
business arrangements. We are revising 40 CFR 1068.261(b) through (d) 
to clarify that the simpler requirements for intra-company shipments 
apply for engines shipped to affiliated companies. Conversely, engine 
manufacturers shipping partially complete engines to any unaffiliated 
company would need to meet the additional requirements that apply for 
inter-company shipments. We define ``affiliated companies'' in 40 CFR 
1068.30.
    The identical configuration exemption in 40 CFR 1068.315(h) allows 
for importation of uncertified engines that are identical to engines 
that have been certified. This might apply, for example, for engines 
that meet both European and U.S. emission standards but were originally 
sold in Europe. We are modifying the regulatory language from 
``identical'' to ``identical in all material respects.'' This change 
allows for minor variation in engines/equipment, such as the location 
of mounting brackets, while continuing to require that engines/
equipment remain identical to a certified configuration as described in 
the manufacturer's application for certification.
    The ancient engine/equipment exemption in 40 CFR 1068.315(i) 
includes an exemption for nonconforming engines/equipment that are at 
least 21 years old that are substantially in their original 
configuration. We originally adopted these for nonroad spark-ignition 
engines in 2002 to align with a similar exemption that was in place for 
light-duty motor vehicles (67 FR 68242, November 8, 2002). Now that 
part 1068 applies for a much wider range of applications, many with 
very long operating lives, it has become clear that this exemption is 
no longer appropriate for importing nonconforming engines. Keeping the 
exemption would risk compromising the integrity of current standards to 
the extent importers misuse this provision to import high-emitting 
engines. This was not the original intent of the exemption. We are 
therefore removing the ancient engine/equipment exemption. The 
identical configuration exemption will continue to be available to 
allow importation of nonconforming engines/equipment that continue to 
be in a configuration corresponding to properly certified engines.
    The regulations at 40 CFR 1068.325 describe provisions that apply 
for temporarily exempting engines/equipment from certification 
requirements. As noted in the introduction to 40 CFR 1068.325, we may 
ask U.S. Customs and Border Protection (CBP) to require a specific bond 
amount to make sure importers comply with applicable requirements. We 
use the imports declaration form (3520-21) to request CBP to require a 
bond equal to the value of these imported engines/equipment for 
companies that are not certificate holders. Several of the individual 
paragraphs describing provisions that apply for specific exemptions 
include a separate statement requiring the importer to post bond for 
these products. We are removing the reference to the bond requirement 
in the individual paragraphs because the introduction addresses the 
bonding requirement broadly for all of 40 CFR 1068.325.
    We are revising the diplomatic or military exemption at 40 CFR 
1068.325(e) to clarify that someone qualifying for an exemption needs 
to show written confirmation of being qualified for the exemption to 
U.S. Customs and Border Protection, not EPA. This may involve 
authorization from the U.S. State Department or a copy of written 
orders for military duty in the United States. Consistent with current 
practice, EPA would not be involved in the transaction of importing 
these exempted products, except to the extent that U.S. Customs and 
Border Protection seeks input or clarification of the requirements that 
apply.
    The regulations at 40 CFR 1068.260(c) currently include an 
exemption allowing manufacturers to ship partially complete engines 
between two of their facilities. This may be necessary for assembling 
engines in stages across short distances. It might also involve 
shipping engines across the country to a different business unit under 
the same corporate umbrella. The regulation at 40 CFR 1068.325(g) 
includes additional provisions for cases involving importation. Multi-
national corporations might also import partially complete engines from 
outside the United States to an assembly plant inside the United 
States. We are revising 40 CFR 1068.325(g) to require that imported 
engines in this scenario have a label that identifies the name of the 
company and the regulatory cite authorizing the exemption. This will 
provide EPA and U.S. Customs and Border Protection with essential 
information to protect against parties exploiting this provision to 
import noncompliant engines without authorization.
    Most of the exemptions that allow manufacturers to import 
uncertified engines include labeling requirements to identify the 
engine manufacturer and the basis of the exemption. We are adding a 
general requirement in 40 CFR 1068.301 to clarify that labels are 
required on all exempted engines. In cases where there are no labeling 
specifications for a given exemption, we are creating a default 
labeling requirement to add a label for exempted engines to identify 
the engine manufacturer and the basis of the exemption.
4. Other Amendments to 40 CFR Part 1068
    We are adopting the following additional amendments to 40 CFR part 
1068:
     Section 1068.1: Clarifying how part 1068 applies for older 
engines. This is necessary for nonroad engines certified to standards 
under 40 CFR parts 89, 90, 91, 92, and 94 because those emission 
standards and regulatory provisions have been removed from the CFR. 
These amendments were inadvertently omitted

[[Page 4449]]

from the rule to remove those obsolete parts.
     Section 1068.1: Changing 40 CFR 1068.1(a)(4) to include 
references to 40 CFR parts 1030 and 1031 for aircraft and aircraft 
engines, instead of the currently listed 40 CFR part 87. 40 CFR part 
1068 contains several general compliance provisions, but the only 
provisions from part 1068 that are relevant to and referenced by the 
regulations for aircraft and aircraft engines are related to procedures 
for handling confidential business information and the definition and 
process for ``good engineering judgment.'' Revising 40 CFR 1068.1 to 
reference 40 CFR parts 1030 and 1031 would not impose any new 
requirements; rather, the updated reference aligns with the existing 
requirements already established in 40 CFR parts 1030 and 1031. This 
amendment was not included in the proposal for this rulemaking. 
However, adopting this change will help readers understand the 
regulations without adding any new requirements.
     Section 1068.1: Clarifying how part 1068 applies for motor 
vehicles and motor vehicle engines. Vehicles and engines certified 
under part 86 are subject to certain provisions in part 1068 as 
specified in part 86. Vehicles and engines certified under parts 1036 
and 1037 are subject to all the provisions of part 1068. This 
correction aligns with regulatory text adopted in previous rulemakings.
     Section 1068.101(a): The regulations at 40 CFR 1068.101(a) 
set forth the prohibitions that apply for engines and equipment that 
are subject to EPA emission standards and certification requirements. 
The regulation includes at 40 CFR 1068.101(a)(2) a prohibition related 
to reporting and recordkeeping requirements. Section 1068.101(a)(3) 
similarly includes a prohibition to ensure that EPA inspectors have 
access to test facilities. These prohibitions derive from CAA section 
208(a), which applies the information and access requirements to 
manufacturers ``and other persons subject to the requirements of this 
part or part C.'' The very first provision of 40 CFR part 1068 at 40 
CFR 1068.1(a) clearly makes the provisions of part 1068 applicable ``to 
everyone with respect to the engine and equipment categories as 
described in this paragraph (a)[, . . .] including owners, operators, 
parts manufacturers, and persons performing maintenance''. However, the 
regulation in 40 CFR 1068.101(a) as written inadvertently limits the 
prohibitions to manufacturers. We are accordingly revising the scope of 
the prohibitions in 40 CFR 1068.101(a) to apply to both manufacturers 
and ``other persons as provided in 40 CFR 1068.1(a)'' in accord with 
those in CAA section 203(a).
     Section 1068.101(b)(5): Removing extraneous words.
     Section 1068.240(a): Removing reference to paragraph (d) 
as an alternative method of qualifying for the replacement engine 
exemption. Paragraph (d) only describes some administrative provisions 
related to labeling partially complete engines so it is not correct to 
describe that as an additional ``approach for exempting'' replacement 
engines.
     Section 1068.240(b) and (c): Adding text to clarify that 
owners may retain possession of old engines after installing an exempt 
replacement engine. This is intended to address a concern raised by 
engine owners that they generally expect to be able to continue to use 
a replaced engine.\580\ Engine owners stated that they expect to use 
the replaced engine for either replacement parts or continued use in a 
different piece of equipment and were surprised to learn that engine 
manufacturers were insisting that the owner turn ownership of the old 
engine to the engine manufacturer. The existing regulation disallows 
simply installing those replaced engines in a different piece of 
equipment, but destroying the engine block and using the engine core as 
a source of replacement parts is acceptable under the existing 
regulation.
---------------------------------------------------------------------------

    \580\ Email exchange regarding replacement engines, August 2020, 
Docket EPA-HQ-OAR-2019-0055.
---------------------------------------------------------------------------

     Sections 1068.601 and 1068.630: Adding provisions to 
establish procedures for hearings related to an EPA decision to approve 
maintenance procedures associated with new technology for heavy-duty 
highway engines. As described in Section IV.B.5.v, we are updating 
regulatory provisions related to engine maintenance for heavy-duty 
highway engines. Section XI.A.9 describes how we may eventually extend 
those same provisions for nonroad engines. The provisions adopted in 
this rule include a commitment for EPA to describe approved maintenance 
for new technology in a Federal Register notice, along with an 
allowance for any manufacturer to request a hearing to object to EPA's 
decision. The general provisions related to hearing procedures in 40 
CFR part 1068, subpart G, cover the maintenance-related hearing 
procedures. We are amending the regulation to provide examples of the 
reasons a manufacturer may request a hearing, including if a 
manufacturer believes certain EPA decisions may cause harm to its 
competitive position, and to add detailed specifications for requesting 
and administering such a hearing for maintenance-related decisions for 
heavy-duty highway engines.
5. Engine and Vehicle Testing Procedures (40 CFR Parts 1036, 1037, 1065 
and 1066)
    The regulations in 40 CFR part 1036, subpart F, 40 CFR part 1037, 
subpart F, and 40 CFR parts 1065 and 1066 describe emission measurement 
procedures that apply broadly across EPA's emission control programs 
for engines, vehicles, and equipment. This final rule includes several 
amendments to these regulations.
    We are deleting the hybrid engine test procedure in 40 CFR 1036.525 
as it was applicable only for model year 2014 to 2020 engines and has 
been replaced with the hybrid powertrain test procedure for model 2021 
and later engines in the existing 40 CFR 1037.550.
    We are updating the engine mapping test procedure in 40 CFR 
1065.510. To generate duty cycles for each engine configuration, engine 
manufacturers identify the maximum brake torque versus engine speed 
using the engine mapping procedures of 40 CFR 1065.510. The measured 
torque values are intended to represent the maximum torque the engine 
can achieve under fully warmed-up operation when using the fuel grade 
recommended by the manufacturer across the range of engine speeds 
expected in real-world conditions. Historically, the mapping procedure 
required the engine to stabilize at discrete engine speed points 
ranging from idle to the electronically limited highest RPM before 
recording the peak engine torque values at any given speed. We adopted 
a provision in the final 40 CFR 1065.510(b)(5)(ii) that allows 
manufacturers to perform a transient sweep from idle to maximum rated 
speed, which requires less time than stabilizing at each measurement 
point.
    The updates to the engine mapping test procedure in 40 CFR 1065.510 
are intended to ensure the resulting engine map achieves its intended 
purpose. The current test procedure is intended to generate a ``torque 
curve'' that represents the peak torque at any specific engine speed 
point. The transient sweep from idle to maximum rated speed can create 
engine conditions that trigger electronic control features on modern 
heavy-duty spark-ignition engines that result in lower-than-peak torque 
levels. Engine control features that can cause variability in the

[[Page 4450]]

maximum torque levels include spark advance, fuel-air ratio, and 
variable valve timing that temporarily alter torque levels to meet 
supplemental goals (such as torque management for transmissions 
shifts).\581\ If the engine map does not capture the true maximum 
torque, the duty cycles generated using the map may not accurately 
recreate the highest-load conditions; this could lead to higher in-use 
emissions.
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    \581\ These AECDS are typically electronic controls that are 
timer-based and initiated for a set duration. In a transient test, 
measurements are taken continuously, and the controls remain 
engaged; the same controls would ``time out'' if each measurement 
was taken at stabilized conditions.
---------------------------------------------------------------------------

    We are finalizing updates to 40 CFR 1065.510(a) to require that the 
torque curve established during the mapping procedure represent the 
highest torque level possible when using the manufacturer's recommended 
fuel grade. Specifically, we are requiring manufacturers to disable 
electronic controls or other auxiliary emission control devices if they 
are of a transient nature and impact peak torque during the engine 
mapping procedure.\582\ Manufacturers would continue to implement their 
engine control during duty-cycle testing, enabling their engines to 
react to the test conditions as they would in real-world operation. The 
changes to the mapping procedure will ensure that testing appropriately 
represents torque output and emissions during high-load and transient 
conditions.
---------------------------------------------------------------------------

    \582\ These electronic controls would be reported as an AECD 
under 40 CFR 1036.205(b).
---------------------------------------------------------------------------

    This final rule includes the following additional amendments to 40 
CFR parts 1065 and 1066, which we are finalizing as proposed unless 
specifically noted otherwise:
     Sections 1065.301 and 1065.1001: Revising NIST-
traceability requirements to allow the use of international standards 
recognized by the CIPM Mutual Recognition Arrangement without prior EPA 
approval. The current regulation allows us to approve international 
standards that are not NIST-traceable, but this was intended only to 
accommodate laboratories in other countries that meet CIPM requirements 
instead of following NIST-traceable protocols. With this approach there 
will no longer be any need for a separate approval process for using 
international standards that are not NIST-traceable. NIST-traceable 
standards are traceable to the International System of Units (SI) as 
specified in NIST Technical Note 1297, which is referenced in the 
definition of NIST-traceable in 40 CFR part 1065. This same 
traceability to the International System of Units is required of 
standards recognized by the CIPM Mutual Recognition Arrangement, thus 
putting them on par with NIST-traceable standards.
     Section 1065.298: Adopting a new 40 CFR 1065.298 with in-
use particulate matter (PM) measurement methods to augment real-time PM 
measurement with gravimetric PM filter measurement for field-testing 
analysis. These methods have been approved for use for over 10 years as 
alternative methods under 40 CFR 1065.10 and 1065.12.
     Section 1065.410: Clarifying that manufacturers may 
inspect engines using electronic tools to monitor engine performance. 
For example, this may apply for OBD signals, onboard health monitors, 
and other prognostic tools manufacturers incorporate into their engine 
designs. As described in the current regulation, inspection tools are 
limited to those that are available in the marketplace. This prevents 
engine manufacturers from handling a test engine more carefully than 
what would be expected with in-use engines. Extending that principle to 
inspection with electronic tools, we are limiting the use of those 
inspections to include only information that can be accessed without 
needing specialized equipment.
     Section 1065.650(c)(6): Adding an allowance to determine 
nonmethane nonethane hydrocarbon (NMNEHC) for engines fueled with 
natural gas as 1.0 times the corrected mass of NMHC if the test fuel 
has 0.010 mol/mol of ethane or more. This may result in a higher 
reported NMNEHC emission value. The engine manufacturer may use this 
method if reducing test burden is more important than the potential for 
a slightly higher reported emission value.
     Section 1065.720: Removing the test fuel specification 
related to volatility residue for liquefied petroleum gas. The 
identified reference procedure, ASTM D1837, has been withdrawn, at 
least in part, due to limited availability of mercury thermometers. 
There is no apparent replacement for ASTM D1837. Rather than adopting 
an alternative specification for volatility residue, we will instead 
rely on the existing residual matter specification based on the 
measurement procedure in ASTM D2158. This alternative specification 
should adequately address concerns about nonvolatile impurities in the 
test fuel.
     Section 1065.910(b): Adding a requirement to locate the 
PEMS during field testing in an area that minimizes the effects of 
ambient temperature changes, electromagnetic radiation, shock, and 
vibration. This may involve putting the PEMS in an environmental 
enclosure to reduce the effect of these parameters. We are also 
removing (1) the recommendation to install the PEMS in the passenger 
compartment because that does not necessarily lead to better mitigation 
of temperature effects as the cab temperature can vary during vehicle 
soaks, (2) ambient pressure as a parameter to minimize as there are no 
known pressure effects on PEMS, and (3) ambient hydrocarbon as a 
parameter because it is more of a PEMS design issue that is handled 
with an activated carbon filter on the burner air inlet, which is 
already covered in 40 CFR 1065.915(c).
     Section 1065.920: Broadening the PEMS calibration and 
verification requirements to make them apply for the new emission 
measurement bin structure we are adopting in 40 CFR part 1036. The 
verification is now generic to verifications for both NTE and binned 
windows for a shift-day of data over 6 to 9 hours. Data would then be 
processed as they would be for an in-use test (either NTE or binned 
windows) and compare the performance of the PEMS to the lab-based 
measurement system.
     Section 1065.935(d): Updating the zero and span 
verification requirements to include new provisions for the emission 
measurement bin structure we are adopting in 40 CFR part 1036 and 
retaining the current requirements for NTE testing only. The procedure 
now includes the requirement to perform zero-verifications at least 
hourly using purified air. Span verifications must be performed at the 
end of the shift-day or more frequently based on the PEMS 
manufacturer's recommendation or good engineering judgment.
     Section 1065.935(g)(5)(iii): Revising from the proposed 
provisions for the final rule to clarify the consequences when PEMS gas 
analyzers (used to determine bin emission values) do not meet zero- or 
span-drift criteria. The intent is that all the test data would be 
considered invalid when drift criteria are not met as this indicates a 
malfunctioning analyzer, calling into question the quality of the data. 
We have added regulatory text to 40 CFR 1065.935(g)(5)(iii) to 
invalidate data for the entire shift day if measurements exceed either 
of the NOX analyzer drift limits in 40 CFR 
1065.935(g)(5)(iii).
     Section 1065.935(g)(6): Adding a new paragraph to include 
new drift limits instead of those in 40 CFR 1065.550 for the emission 
measurement bin structure we are adopting in 40 CFR part 1036. The 
analyzer zero drift limit between the hourly or more frequent zero 
verifications is 2.5 ppm, while the limit over the entire shift-day (or 
more

[[Page 4451]]

frequently if you perform zero-adjustments) is 10 ppm. The analyzer 
span drift limit between the beginning and end of the shift-day or more 
frequent span verification(s) or adjustment(s) must be within 4 percent of the measured span value.
     Sections 1065.1123, 1065.1125, and 1065.1127: Adding new 
regulatory sections to migrate the smoke test procedure in 40 CFR part 
86, subpart I, into 40 CFR part 1065. This provides a common location 
for the test procedure and analyzer requirements for all parts that 
still require smoke measurement except for locomotive testing. The 
locomotive test procedure continues to reside in 40 CFR part 1033, 
subpart F, as it is specific to locomotive testing and operation at 
specific notches. No updates were made to the procedure that affect 
analyzer requirements and setup or how a laboratory reports test 
results. For all engines required to carry out smoke testing, other 
than locomotive engines, we are updating operation at curb idle speed 
to instead reference warm idle speed, and we are changing from ``rated 
speed'' to instead reference ``maximum test speed''. This change should 
not adversely affect the acceleration and lugging modes of the test and 
it will make smoke testing consistent with all other engine-based 
testing that now use warm idle speed and maximum test speed.
     Part 1066, subpart D: Incorporating by reference and 
making applicable as specified in this part an updated version of SAE 
J2263 for coastdown measurements. The updated standard incorporates EPA 
guidance for vehicles certified under 40 CFR part 86, subpart S.\583\ 
The updated version of the test method also reduces the wind speed 
allowed for performing measurements, allows for adding ballast to 
vehicles if needed, and adds clarifying procedures for testing on oval 
tracks. These changes, which align with current practice for light-duty 
vehicles, will have no substantial effect for measurements with heavy-
duty vehicles. We are therefore applying the updated version of SAE 
J2263 for all light-duty and heavy-duty vehicles. After consideration 
of comments, we have changed the final rule to make the new test 
specifications optional through model year 2025.
---------------------------------------------------------------------------

    \583\ ``Determination and Use of Vehicle Road-Load Force and 
Dynamometer Settings'', EPA Guidance Document CD-15-04, February 23, 
2015.
---------------------------------------------------------------------------

     Section 1066.420: Adding the existing 40 CFR 86.140-94 
requirement to zero and span calibrate the hydrocarbon analyzer by 
overflowing the zero and span gas at the hydrocarbon sampling system 
probe inlet during analyzer calibration when testing vehicles that are 
14,000 GVWR or less. This requirement was inadvertently missed during 
the migration of the light-duty test procedures to 40 CFR part 1066. 
After consideration of comments, the final rule revises the proposal by 
reducing the HC contamination limit in 40 CFR 1066.420(b)(1)(iii) from 
2 [micro]mol/mol to 0.5 [micro]mol/mol for vehicles at or below 14,000 
pounds GVWR with compression-ignition engines.
     Section 1066.831: Removing the reference to 40 CFR part 
1065 regarding how to measure THC emissions, as the method for 
measuring THC emission is already covered in 40 CFR part 1066, subparts 
B and E.
    This final rule includes additional amendments that are regarded as 
clarifications in the following sections of 40 CFR parts 1036, 1037, 
1065, and 1066 (as numbered in this final rule): 40 CFR 1036.501, 
1036.505, 1036.510, 1036.512, 1036.520, 1036.535, 1036.540, 1036.543, 
and 1036.550; 40 CFR 1037.320, 1037.510, 1037.515, 1037.520, 1037.534, 
1037.540, 1037.550, 1037.551, 1037.555, 1037.601, 1037.615, and 
1037.725; 40 CFR 1065.1, 1065.5, 1065.10, 1065.12, 1065.140, 1065.145, 
1065.190, 1065.210, 1065.284, 1065.301, 1065.305, 1065.307, 1065.308, 
1065.309, 1065.315, 1065.320, 1065.325, 1065.330, 1065.345, 1065.350, 
1065.410, 1065.501, 1065.510, 1065.512, 1065,514, 1065.530, 1065.543, 
1065.545, 1065.610, 1065.630, 1065.650, 1065.655, 1065.660, 1065.667, 
1065.670, 1065.675, 1065.680, 1065.695, 1065.715, 1065.720, 1065.790, 
1065.901, 1065.915, 1065.920, 1065.1001, and 1065.1005; and 40 CFR 
1066.110, 1066.220, 1066.301, 1066.415, 1066.420, 1066.710, 1066.815, 
1066.835, 1066.845, 1066.1001, and 1066.1005.
    See Section 14 through 16 of the Response to Comments for a 
discussion of comments related to engine and vehicle testing 
provisions.
6. Vanadium-Based SCR Catalysts
    In certain diesel engine applications vanadium-based SCR catalysts 
may provide a performance and cost advantage over other types of 
catalysts. However, vanadium material can sublime from the catalyst in 
the presence of high exhaust gas temperatures.\584\ Sublimation of 
vanadium catalyst material leads to reduced NOX conversion 
efficiency of the catalyst and possible exposure of the public to 
vanadium emissions. In 2016 EPA provided certification guidance to 
manufacturers of diesel engines equipped with vanadium-based SCR 
catalysts (``2016 guidance'').\585\ The certification guidance 
clarified EPA's expectations for manufacturers using vanadium-based SCR 
catalysts and provided our views and recommendations on reasonable 
steps manufacturers can take to protect against excessive loss of 
vanadium from these SCR systems. We are now codifying these provisions 
as regulatory requirements for using vanadium-based SCR catalysts. We 
are adopting these requirements for all types of highway and nonroad 
diesel engines. The regulatory provisions are consistent with the 2016 
guidance and will begin to apply when the final rule becomes effective. 
To facilitate this direct implementation for 2026 and earlier model 
years, we are updating 40 CFR 86.007-11 to reference the new 40 CFR 
1036.115(g)(2), which contains the requirements related to vanadium-
based SCR catalysts.
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    \584\ The temperature at which vanadium sublimation occurs 
varies by engine and catalyst and is generally 550 [deg]C or higher.
    \585\ ``Certification of Diesel Engines Equipped with Vanadium-
based SCR Catalyst'', EPA guidance document CD-16-09, June 13, 2016.
---------------------------------------------------------------------------

    To meet the new requirements, manufacturers of engines equipped 
with vanadium-based SCR catalysts must determine vanadium sublimation 
temperatures and thermal management strategies and include 
documentation in their certification applications. EPA will use the 
information submitted by manufacturers in evaluating a manufacturer's 
engine and aftertreatment design as part of the application for 
certification. Note that the certification requirements described in 
this section for manufacturers apply equally to anyone certifying 
remanufactured engines or associated remanufacturing systems where such 
certification is required.
    In their certification applications, engine manufacturers must 
provide information identifying the vanadium sublimation temperature 
threshold for the specific catalyst product being used. To identify the 
vanadium sublimation temperature, manufacturers must use the vanadium 
sublimation sampling and analytical test method we are adopting in 40 
CFR part 1065, subpart L, which is consistent with the procedures 
identified in the 2016 guidance.\586\ Manufacturers must also identify 
their thermal management strategy that prevents exhaust gas 
temperatures from exceeding the vanadium sublimation temperature. In 
addition, manufacturers

[[Page 4452]]

must identify how their thermal management strategy will protect the 
catalyst in the event of high-temperature exotherms resulting from 
upstream engine component failures, as well as exotherms resulting from 
hydrocarbon buildup during normal engine operation. EPA expects to 
approve applications describing thermal management strategies that 
prevent exhaust gas temperatures from exceeding the vanadium 
sublimation temperature.
---------------------------------------------------------------------------

    \586\ EPA is adopting the test method from CD-16-09 in 40 CFR 
part 1065, subpart L; 40 CFR 1065.12 describes the process for 
approving alternative test procedures.
---------------------------------------------------------------------------

    Commenters noted that the unit of measure for the method detection 
limit should be a volume-normalized concentration for a gaseous sample, 
rather than a solid mass volume, as this will address concerns with the 
variable impact of dilution effect based on sample size. We are 
finalizing a recommended method detection limit of 15 [mu]g/m\3\ based 
on a target mass-based method detection limit of 2 ppm, a 60 g capture 
bed mass, a 0.0129 L (1'' long x 1'' diameter core) catalyst volume, an 
SV of 35,000 s-\1\, and an 18-hour test duration. We also 
agree that the units in EPA guidance document CD-16-09 are inaccurate 
and reflect a typographical error, and that the units should be in 
[mu]g instead of pg to reflect a detection limit of ppm.
    If a manufacturer is interested in pursuing another means to 
determine the vanadium sublimation threshold, for example by performing 
an engine dynamometer-based test utilizing the full production 
aftertreatment system, they may request the approval of alternative 
vanadium sublimation test procedures as described in current 40 CFR 
1065.10(c)(7).
7. ULSD-Related Exemption for Guam
    EPA's in-use fuel requirements at 40 CFR part 1090 include an 
exemption from the 15-ppm sulfur standard for Guam, American Samoa, and 
the Commonwealth of the Northern Mariana Islands (40 CFR 1090.620). 
Diesel fuel meeting the 15-ppm standard is known as ultra-low sulfur 
diesel or ULSD. EPA's emission standards for highway and nonroad diesel 
engines generally involves SCR as a control technology. The durability 
of SCR systems depends on the use of fuel meeting the 15-ppm ULSD 
standard, so we adopted a corresponding exemption from the most 
stringent emission standards for engines used in these three 
territories (see 40 CFR 86.007-11(f) for heavy-duty highway engines and 
40 CFR 1039.655 for land-based nonroad diesel engines).
    Guam has in the meantime adopted rules requiring the 15-ppm sulfur 
standard for in-use diesel fuel for both highway and nonroad engines 
and vehicles. As a result, there is no longer a reason to keep the 
exemption from emission standards for engines used in Guam. We are 
therefore removing the exemption for these engines in Guam. In response 
to manufacturers' request for time to work through supply and inventory 
logistics, the final rule removes the Guam exemption effective January 
1, 2024.
    We are not aware of American Samoa and the Northern Mariana Islands 
adopting ULSD requirements and we are therefore not removing the 
exemption for those territories in this final rule.
    We are also clarifying that the exemption for land-based nonroad 
diesel engines at 40 CFR 1039.655 applies only for engines at or above 
56 kW. Smaller engines are not subject to NOX standards that 
would lead manufacturers to use SCR or other sulfur-sensitive 
technologies, so we do not expect anyone to be using this exemption for 
engines below 56 kW in any area where the exemption applies. We note 
that Guam's 15-ppm sulfur standard for in-use diesel fuel is now 
identical to EPA's 15-ppm diesel fuel sulfur standards in 40 CFR part 
1090 and as such could not be preempted under CAA section 
211(c)(4)(A)(ii). We intend to revisit the exemption from the Federal 
15-ppm ULSD standard for diesel fuel in Guam under 40 CFR part 1090 in 
a future action. Removing the Federal exemption for diesel fuel in Guam 
would likely involve new or revised regulatory provisions for parties 
that make, distribute, and sell diesel fuel in Guam such as additional 
reporting, recordkeeping, and other compliance-related provisions.
8. Deterioration Factors for Certifying Nonroad Engines
    Section IV describes an approach for manufacturers of heavy-duty 
highway engines to establish deterioration factors (DFs) based on 
bench-aged aftertreatment in combination with a plan for testing in-use 
engines to verify that the original deterioration factor properly 
predicts an engine's emission levels at the end of the useful life. As 
described in Section IV.F, we are adopting the new approach for 
establishing deterioration factors to take advantage of available 
techniques for bench-aging aftertreatment devices to streamline the 
certification and product-development timeline. The leaner up-front 
testing can be complemented by measurements from in-use engines to 
verify that the original deterioration factors are still appropriate 
for certifying engines in later model years.
    This same dynamic applies for nonroad applications. We are 
therefore adopting amendments to allow manufacturers of all types of 
nonroad diesel engines and manufacturers of land-based nonroad spark-
ignition engines above 19 kW to use these same procedures to establish 
and verify DFs. These amendments apply for 40 CFR parts 1033, 1039, 
1042, and 1048. We are not adopting any changes to the existing 
certification and durability procedures for these nonroad engines if 
the manufacturer does not rely on the new DF verification protocol.
    Most of the new DF verification procedures for heavy-duty highway 
engines apply equally for nonroad engines, but unique aspects of each 
certification program call for making the following adjustments:
     Marine and land-based nonroad diesel engines are subject 
to not-to-exceed standards and corresponding test procedures that will 
continue to apply instead of the in-use measurement protocols adopted 
in this rule for heavy-duty highway engines.
     Land-based nonroad spark-ignition engines above 19 kW 
(Large SI engines) are subject to field-testing standards and 
corresponding test procedures that will continue to apply instead of 
the in-use measurement protocols adopted in this rule for heavy-duty 
highway engines.
     Locomotives are not subject to off-cycle emission 
standards or emission measurement procedures that apply during normal 
in-use operation. However, manufacturers can perform in situ testing on 
in-use locomotives that meets all the specifications for certification 
testing in a laboratory. This allows for testing in-use engines to 
verify that deterioration factors based on bench-aged aftertreatment 
devices are appropriate for predicting full-life emissions.
     Each type of nonroad diesel engine already has sector-
specific methods for calculating infrequent regeneration adjustment 
factors.
    We are not adding the option to use this approach for certifying 
recreational vehicles, land-based nonroad spark-ignition engines at or 
below 19 kW, or marine spark-ignition engines. These engines are 
generally subject to certification of a useful life that is much 
shorter than the values that apply for the types of engines for which 
we are adding the option to use the new DF verification protocol. Many 
nonroad spark-ignition engines are also certified without 
aftertreatment. As a result, it is not clear that manufacturers of 
these other types of engines would find a benefit of using the new DF 
verification procedures.
    We are adopting the proposed changes without modification. See

[[Page 4453]]

Section 30.4 of the Response to Comments for a discussion of the 
comments submitted regarding deterioration factors for nonroad engines.

B. Heavy-Duty Highway Engine and Vehicle Emission Standards (40 CFR 
Parts 1036 and 1037)

1. Timing of Annual Reports
    We are adopting amendments to simplify annual reporting 
requirements to account for the extensive information submissions 
related to the greenhouse gas emission standards. Vehicle manufacturers 
are required to report on GEM results and production volumes for 
thousands of distinct vehicle configurations at the end of the model 
year to show that emission credits related to calculated average 
CO2 emission rates are sufficient to comply with standards. 
The regulation currently requires an interim end-of-year report by 
March 31 and a final report by September 30 (see 40 CFR 1037.730). This 
same schedule is typical for documentation related to emission credits 
for various types of nonroad engines and vehicles. In contrast to those 
nonroad programs, compliance with the heavy-duty highway CO2 
emission standards relies on a detailed assessment of GEM results and 
corresponding production volumes to determine all the necessary credit 
calculations for the model year. We are amending 40 CFR 1037.730 to no 
longer require the interim end-of-year report, because we have observed 
that manufacturers need more time to complete their effort to fully 
document their compliance for the model year and we believe the interim 
end-of-year report is unnecessary for heavy-duty vehicles. The 
regulation allows us to waive this interim report, and we have 
routinely approved such requests. We are not adopting any change to the 
content of the final report due in September and will continue to rely 
on that final report to evaluate compliance with standards.
    Engine manufacturers generate and use emission credits based on 
production volumes that correspond to the vehicle production. As a 
result, it is beneficial for both EPA and engine manufacturers to align 
the emission credit reporting requirements for engines and vehicles. We 
are therefore amending 40 CFR 1036.730 to also omit the interim end-of-
year report and instead rely only on the final report submitted by 
September 30 following each model year. In addition, the regulations at 
40 CFR 1036.250 and 1037.250 currently specify that engine and vehicle 
manufacturers must report their production volumes within 90 days after 
the end of the model year. For the same reasons given for modifying the 
schedule for credit reports, we are aligning this production reporting 
with the final ABT report, requiring manufacturers to report their 
production volumes also by September 30 following the end of the model 
year.
    We received no comments on these proposed amendments for credit 
reporting and are finalizing the proposed changes without modification.
2. Scope and Timing for Amending Applications for Certification
    Engines must be produced in a certified configuration to be covered 
by the certificate of conformity. Manufacturers routinely need to amend 
their applications for certification during the model year to reflect 
ongoing product development. These amendments may involve new 
configurations or improvements to existing configurations. The current 
regulations describe how manufacturers can make these amendments in a 
way that allow them to comply with the general requirement to produce 
engines that are in a certified configuration (see 40 CFR 1036.225 and 
1037.225). We generally refer to these amendments as running changes. 
Manufacturers apply these running changes to new engines they continue 
to build during the model year. Applying these running changes to 
engines that have already been produced is referred to as a ``field 
fix''. We have provided ``field-fix'' guidance since the earliest days 
of EPA emission standards.\587\
---------------------------------------------------------------------------

    \587\ ``Field Fixes Related to Emission Control-Related 
Components,'' EPA Advisory Circular, March 17, 1975.
---------------------------------------------------------------------------

    We recently adopted regulatory provisions in 40 CFR parts 1036 and 
1037 to describe how manufacturers may modify engines as reflected in 
the modified application for certification, which included essential 
elements of the 1975 field-fix guidance (80 FR 73478, October 25, 
2016).
    There is also a related field-fix question of how to allow for 
design changes to produced engines (before or after initial shipment) 
that the manufacturer identifies after the end of the model year. The 
preamble for that recent final rule explained that the regulatory 
provisions also included how manufacturers may amend an application for 
certification after the end of the model year to support intended 
modifications to in-use engines.
    After further consideration, we are revising 40 CFR 1036.225 and 
1037.225 to limit manufacturers to having the ability to amend an 
application for certification only during the production period 
represented by the model year. These revisions apply starting with the 
effective date of the final rule. Manufacturers can continue to apply 
field fixes to engines they have already produced if those engine 
modifications are consistent with the amended application for 
certification.
    The process for amending applications for certification under 40 
CFR 1036.225 and 1037.225 does not apply for field fixes that the 
manufacturer identifies after the end of the model year. Like our 
approach in other standard-setting parts for nonroad applications, we 
refer manufacturers to the 1975 field-fix guidance for recommendations 
on how to approach design changes after the end of the model year. 
EPA's certification software is already set up to accommodate 
manufacturers that submit documentation for field fixes related to 
engine families from earlier model years. We believe this approach is 
effective, and it involves less burden for EPA implementation than 
allowing manufacturers to amend their application for certification 
after the end of the model year.
    We received no comments on the proposed provisions related to 
amending applications for certification and are finalizing the proposed 
changes without modification.
    We expect to propose further regulatory provisions in a future 
rulemaking to update and clarify implementation of the field-fix policy 
for design changes that occur after the end of the model year. We 
expect that rulemaking to include consideration of such provisions for 
all types of highway and nonroad engines and vehicles.
3. Alternate Standards for Specialty Vehicles
    The final rule adopting HD GHG Phase 2 standards for heavy-duty 
highway engines and vehicles included provisions allowing limited 
numbers of specialty motor vehicles to have engines meeting alternate 
standards derived from EPA's nonroad engine programs (80 FR 73478, 
October 25, 2016). The provisions applied for amphibious vehicles, 
vehicles with maximum operating speed of 45 mph or less, and all-
terrain vehicles with portal axles. The provisions also apply for 
hybrid vehicles with engines that provide energy for a Rechargeable 
Energy Storage System, but only through model year 2027.
    We continue to recognize the need for and benefit of alternate 
standards that

[[Page 4454]]

address limitations associated with specialty vehicles. We are 
therefore, as proposed, migrating these alternate standards from 40 CFR 
86.007-11 and 86.008-10 into 40 CFR 1036.605 without modification. See 
section 29.1 of the Response to Comments for a discussion of the 
comment submitted regarding alternate standards for specialty vehicles.
    We are mindful of two important regulatory and technological 
factors that may lead us to revise the alternate standards for 
specialty vehicles in a future rulemaking. First, certifying based on 
powertrain testing addresses the testing limitations associated with 
nonstandard power configurations. Second, emission control technologies 
may support more stringent alternate emission standards than the 
current nonroad engine standards. Furthermore, CARB has not adopted 
that same approach to apply alternate standards for specialty vehicles 
and we are unaware of manufacturers certifying any of these types of 
specialty vehicles to the full engine and vehicle standards.
4. Additional Amendments
    We are amending 40 CFR parts 1036 and 1037 to describe units for 
tire rolling resistance as newtons per kilonewton (N/kN) instead of kg/
tonne. SAE J2452 treats these as interchangeable units, but ISO 28580, 
which we incorporated by reference at 40 CFR 1037.810, establishes N/kN 
as the appropriate units for measuring rolling resistance. Since the 
units in the numerator and denominator cancel each other out either 
way, this change in units has no effect on the numerical values 
identified in the regulation or on data submitted by manufacturers.
    The regulation at 40 CFR 1037.115(e) describes how manufacturers 
demonstrate that they meet requirements related to air conditioning 
leakage. Paragraph (e) allows for alternative demonstration methods 
where the specified method is impossible or impractical, but limits 
that alternative to systems with capacity above 3000 grams of 
refrigerant. We recognize alternative demonstrations may also be 
necessary for systems with smaller capacity and are therefore removing 
this qualifying criterion. This change is also consistent with 
amendments CARB adopted in the Omnibus rule.\588\
---------------------------------------------------------------------------

    \588\ California Air Resources Board, ``Appendix B-3 Proposed 
30-Day Modifications to the Greenhouse Gas Test Procedures'', May 5, 
2021, Available online: https://ww2.arb.ca.gov/sites/default/files/barcu/regact/2020/hdomnibuslownox/30dayappb3.pdf, page 20.
---------------------------------------------------------------------------

    The SET duty cycle specified in 40 CFR 86.1362 contains the engine 
speed and load as well as vehicle speed and road grade to carry out 
either engine or powertrain testing. The table defining the duty cycle 
contains two errors in the vehicle speed column for modes 1a and 14. 
The vehicle speed is set to ``warm idle speed'' in the table, which is 
an engine test set point. Since this is an idle mode and the vehicle is 
not moving, the vehicle speeds should be set to 0 mi/hr. This 
correction will have no effect on how powertrain testing over this duty 
cycle is carried out.
    We are correcting a typo in 40 CFR 1036.235(c)(5)(iv)(C) regarding 
EPA's confirmatory testing of a manufacturer's fuel map for 
demonstrating compliance with greenhouse gas emission standards. We are 
changing the reference to ``greater than or equal to'' and instead 
saying ``at or below'' to be consistent with the related interim 
provision in 40 CFR 1036.150(q). The intent of the EPA testing is to 
confirm that the manufacturer-declared value is at or below EPA's 
measured values.
    We are clarifying that ``mixed-use vehicles'' qualify for alternate 
standards under 40 CFR 1037.105(h) if they meet any one of the criteria 
specified in 40 CFR 1037.631(a)(1) or (2). In contrast, vehicles 
meeting the criterion in 40 CFR 1037.631(a)(1) and at least one of the 
criteria in 40 CFR 1037.631(a)(2) automatically qualify as being exempt 
from GHG standards under 40 CFR part 1037.
    We are amending 40 CFR 1036.250(a) to clarify that engine 
manufacturers' annual production report needs to include all engines 
covered by EPA certification, which includes total nationwide 
production volumes. We inadvertently used the term ``U.S.-directed 
production volume'', which we define in 40 CFR 1036.801 to exclude 
engines certified to state emission standards that are different than 
EPA emission standards. That exclusion applies only for emission credit 
calculations under 40 CFR part 1036, subpart H, and reports under the 
ABT program. Manufacturers typically already report nationwide 
production volumes in their reports under 40 CFR 1036.250(a), so this 
change will have little or no impact on current certification 
practices.
    We received no comments on the proposed amendments described in 
this section and are finalizing the proposed changes without 
modification.

C. Fuel Dispensing Rates for Heavy-Duty Vehicles (40 CFR Parts 80 and 
1090)

    EPA adopted a regulation limiting the fuel dispensing rate to a 
maximum of 10 gallons per minute for gasoline dispensed into motor 
vehicles (58 FR 16002, March 24, 1993). The dispensing limit 
corresponded with the test procedure for vehicle manufacturers to 
demonstrate compliance with a refueling spitback standard adopted in 
the same final rule. Spitback involves a spray of liquid fuel during a 
refueling event if the vehicle cannot accommodate the flow of fuel into 
the fuel tank. The spitback standard applied only for vehicles at or 
below 14,000 pounds GVWR, so we provided an exemption from the 
dispensing limit for dispensing pumps dedicated exclusively to heavy-
duty vehicles (see 40 CFR 80.22(j) and 1090.1550(b)). Just like for 
spitback testing with vehicles at or below 14,000 pounds GVWR, vehicles 
designed with onboard refueling vapor recovery systems depend on a 
reliable maximum dispensing rate to manage vapor flow into the carbon 
canister.
    Now that we are adopting a requirement for all gasoline-fueled 
heavy-duty highway vehicle manufacturers to comply with refueling 
standards, it is no longer appropriate to preserve the exemption from 
the dispensing rate limit for dispensing pumps dedicated exclusively to 
heavy-duty vehicles. Retail stations and fleets rarely have dispensing 
pumps that are dedicated to heavy-duty vehicles. Since there are no 
concerns of feasibility or other issues related to meeting the 10 
gallon per minute dispensing limit, we are removing the exemption upon 
the effective date of the final rule.
    We received no adverse comments on these proposed amendments 
related to in-use gasoline dispensing rates and are finalizing the 
proposed changes without modification.
    We note that existing dispensing rate limits relate only to 
gasoline-fueled motor vehicles. There is no rate restriction on 
dispensing diesel fuel into motor vehicles, or on dispensing any kind 
of fuel into aircraft, marine vessels, other nonroad equipment, or 
portable or permanently installed storage tanks. We are also not 
adopting new dispensing rate limits for these fuels in this action.

D. Refueling Interface for Motor Vehicles (40 CFR Parts 80 and 1090)

    We proposed to remove the filler-neck restriction in 40 CFR 80.24. 
The proposal included a decision not to migrate that restriction to 40 
CFR part 86, subpart S, for chassis-certified motor vehicles. 
Commenters highlighted the continued commercial and regulatory need for 
EPA to keep the requirement for engine manufacturers to standardize the 
size of the filler-necks orifice for

[[Page 4455]]

gasoline-fueled vehicles. We are therefore moving the filler-neck 
requirement from 40 CFR 80.24 to 40 CFR 86.1810-17 without changing the 
substantive requirement. See Section 31.2 of the Response to Comments. 
This requirement applies for vehicles with gross vehicle weight rating 
up to 14,000 pounds. We are including no lead time for this requirement 
because it is consistent with the requirement from 40 CFR 80.24.

E. Light-Duty Motor Vehicles (40 CFR Parts 85, 86, and 600)

    EPA's emission standards, certification requirements, and fuel 
economy provisions for light-duty motor vehicles are in 40 CFR part 85, 
40 CFR part 86, subpart S, and 40 CFR part 600.
1. Testing With Updated Versions of SAE J1634
i. Existing BEV Test Procedures
    EPA's existing regulations for testing Battery Electric Vehicles 
(BEVs) can be found in 40 CFR part 600--Fuel Economy and Greenhouse Gas 
Emissions of Motor Vehicles. The existing EPA regulations (40 CFR 
600.116-12(a) and 600.311-12(j) and (k)) reference the 2012 version of 
the SAE Standard J1634--Battery Electric Vehicle Energy Consumption and 
Range Test Procedure.
    Current regulations (40 CFR 600.116-12(a)) allow manufacturers to 
perform either single cycle tests (SCT) or the multi-cycle test (MCT) 
as described in the EPA regulations and the 2012 version of SAE J1634. 
The SCT and MCT are used to determine the unrounded and unadjusted city 
and highway range values and the city and highway mile per gallon 
equivalent (MPGe) fuel economy values.
    The 2012 version of SAE J1634 specifies 55 miles per hour (mph) as 
the speed to be used during the mid-test and end-of-test constant-speed 
cycles of the MCT. The 2017 version of SAE J1634 specifies 65 mph as 
the speed to be used during the constant-speed cycles of the MCT. 
Manufacturers have reached out to the Agency and requested to use the 
2017 version of SAE J1634 to reduce the time required to perform the 
MCT and the Agency has generally approved these requests. EPA's fuel 
economy regulations allow manufacturers to use procedures other than 
those specified in the regulations. The special test procedure option 
is described in 40 CFR 600.111-08(h). This option is used when vehicles 
cannot be tested according to the procedures in the EPA regulations or 
when an alternative procedure is determined to be equivalent to the EPA 
regulation.
    EPA regulations found in 40 CFR 600.210-12(d)(3) specify three 
options for manufacturers to adjust the unrounded and unadjusted 2-
cycle (city and highway) results for fuel economy labeling purposes. 
The three methods include: Generating 5-cycle data; multiplying the 2-
cycle values by 0.7; and asking the Administrator to approve adjustment 
factors based on operating data from in-use vehicles. To date the 
Agency has not approved any requests to use operating data from in-use 
vehicles to generate an adjustment factor.
    Many manufacturers use the option to multiply their 2-cycle fuel 
consumption and range result by the 0.7 adjustment factor. The benefit 
of this option for the manufacturer is that the manufacturer does not 
need to perform any of the additional 5-cycle tests to determine the 
label result. This method is equivalent to the derived 5-cycle method 
which allows manufacturers to adjust their 2-cycle fuel economy test 
results for gasoline vehicles based on the EPA determined slope and 
intercept values generated from 5-cycle testing performed on emission 
data vehicles (EDVs).
    A few manufacturers have been using the option to generate 5-cycle 
data which is then used for determining a 5-cycle adjustment factor. 
The specific 5-cycle adjustment factor is then multiplied by the 
unrounded, unadjusted 2-cycle results to determine fuel economy label 
values.
    EPA's current regulations do not specify a method for performing 5-
cycle testing for BEVs. EPA acknowledged this in the 2011 rulemaking 
that created the fuel economy label requirement for BEVs:
    The 5-cycle testing methodology for electric vehicles is still 
under development at the time of this final rule. This final rule will 
address 2-cycle and the derived adjustments to the 2-cycle testing, for 
electric vehicles. As 5-cycle testing methodology develops, EPA may 
address alternate test procedures. EPA regulations allow test methods 
alternate to the 2-cycle and derived 5-cycle to be used with 
Administrator approval. (76 FR 39501, July 6, 2011)
    The first manufacturer to approach EPA and request to perform 5-
cycle testing for BEVs was Tesla, and EPA approved Tesla's request. The 
method Tesla proposed is known as the BEV 5-cycle adjustment factor 
method, and it was added to Appendices B and C of the SAE J1634 
Standard in the 2017 update.
    Since publication of the 2017 version of SAE J1634, BEV 
manufacturers in addition to Tesla have been approaching the Agency and 
seeking to use the 5-cycle adjustment factor methodology outlined in 
Appendices B and C. EPA has generally approved manufacturer requests to 
use this method.
    The 5-cycle method outlined in the 2017 version of SAE J1634 is 
essentially the same method that EPA uses to determine 5-cycle fuel 
economy for vehicles with internal combustion engines. There are, 
however, two differences between the EPA approved BEV 5-cycle 
adjustment factor method compared to the 5-cycle calculation 
methodology outlined in 40 CFR 600.114-12, Vehicle-specific 5-cycle 
fuel economy and carbon-related exhaust emission calculations. The 
first difference is that the numerator of the City and Highway fuel 
economy equations is 0.92 rather than 0.905. This was done to remove 
the ethanol correction from the 5-cycle fuel economy equation for BEVs. 
The second change was to allow BEV manufacturers to use the results of 
a full charge depleting Cold Temperature Test Procedure (CTTP or 20 
[deg]F FTP) in the City fuel economy calculation when calculating the 
running fuel consumption. Vehicles with internal combustion engines 
(ICE) use only the bag 2 and bag 3 fuel economy results from the CTTP. 
The CTTP is performed at an ambient temperature of 20 [deg]F after the 
vehicle has cold-soaked in the 20 [deg]F test chamber for a minimum of 
12 hours and a maximum of 36 hours. In addition, to reduce the testing 
burden the current BEV 5-cycle procedure allows manufacturers to skip 
the 10-minute key-off soak between UDDS cycles after the second UDDS 
cycle. This test procedure allowance was made to reduce the time burden 
for performing full charge depletion testing in the cold test chamber.
ii. Summary of Changes
    The final rule amends the revisions to Sec.  600.116-12(a) and 
Sec. Sec.  600.311-12(j)(2) and 600.311-12(j)(4)(i).
    EPA is adopting the proposal to update the SAE J1634 standard 
referenced in 40 CFR part 600 from the 2012 version to the 2017 
version. This update will require manufacturers to use 65 mph for the 
constant-speed cycles of the MCT. In addition, this update will allow 
manufacturers to use the BEV 5-cycle adjustment factor methodology 
outlined in Appendices B and C of the 2017 version of SAE J1634 with 
the revisions described in this section.

[[Page 4456]]

    EPA received comments requesting the Agency adopt the 2021 version 
of SAE J1634. The 2021 version of SAE J1634 includes several additional 
test procedure changes not included in the 2017 version. Updates for 
the 2021 version include the development of additional test procedures 
including the shortened multi-cycle test (SMCT) and the shortened 
multi-cycle test plus (SMCT+); and, the capability to pre-condition the 
BEV prior to performing any of the test procedures, including the 20 
[deg]F UDDS, also known as the cold temperature test procedure (CTTP).
    At this time the Agency is not prepared to adopt the 2021 version 
of SAE J1634 with these additional test procedures and pre-conditioning 
process. The Agency is evaluating the new test procedures (SMCT and 
SMCT+) to ensure they produce results equivalent to those generated 
using the existing SCT and MCT test procedures. In addition, the Agency 
is assessing the use of pre-conditioning the battery and cabin of BEVs 
prior to performing tests. The Agency is not prepared to adopt 
preconditioning for BEVs during the soak period prior to starting the 
drive cycle for the CTTP. The intent of the 12 to 36 hour cold soak 
period prior to the start of the drive cycle for the CTTP is to 
stabilize the vehicle and its components at 20 [deg]F prior to starting 
the driving portion of the test. While BEVs have technology and have 
operating modes that allow the battery and cabin to be preconditioned 
while the vehicle is soaking, for this technology to function the 
vehicle must have access to a dedicated EVSE and the operator must 
enable this operation. The Agency does not expect that a predominance 
of BEVs will have access to a dedicated EVSE while the vehicle is `cold 
soaking' prior to many cold starts and that the operator will have 
enabled the preconditioning mode during the soak period. Therefore, the 
Agency is not adopting the 2021 version of SAE J1634 in this final 
rule.
    EPA proposed for model year 2023, that manufacturers could continue 
to perform full charge depletion testing on BEVs when running the CTTP 
to determine the 5-cycle adjustment factor. However, EPA proposed 
requiring in model year 2023 that manufacturers perform a 10-minute 
key-off soak between each UDDS cycle as part of the charge depleting 
CTTP. The Agency has decided not to adopt this proposal based on 
stakeholder comments and the effort required to update test cells for a 
procedural change which would only be in effect for one model year.
    We are not changing the existing requirement to submit a written 
request for EPA approval to perform 5-cycle testing prior to beginning 
5-cycle adjustment procedure testing. Manufacturers must attest that 
the vehicle was not preconditioned or connected to an external power 
source during the 20 [deg]F cold soak period.
    The Agency proposed requiring manufacturers to perform only two 
UDDS cycles when running the CTTP, with a 10-minute key-off soak 
between the UDDS cycles to generate their BEV 5-cycle adjustment factor 
beginning in model year 2024. The Agency is adopting this proposal and 
is delaying the start from model year 2024 to the 2025 based on 
comments received from stakeholders and the timing of the final 
rulemaking. The running fuel consumption for the City fuel economy 
equation comes from a modified form of the equation provided in 
Appendix C of the 2017 version of SAE J1634. The charge-depletion value 
is replaced with the results from Bag 2 of the first and second UDDS 
and Bag 1 from the second UDDS. Manufacturers may use their existing 
CTTP test results to make these calculations, or they may perform new 
tests with the option to select the vehicle's state-of-charge so it can 
capture regeneration energy during the first UDDS cycle.
    EPA is also adopting the following additional changes to the 
procedures outlined in the 2017 version of SAE J1634:
     Specifying a maximum constant-speed phase time of 1 hour 
with 5- to 30 minute key-off soak following each one-hour constant-
speed phase.
     Specifying the use of the methods in Appendix A of the 
2017 version of SAE J1634 to determine the constant-speed cycle's total 
time for the mid-test constant-speed cycle, or the manufacturer may use 
a method they developed using good engineering judgment.
     Specifying that energy depleted from the propulsion 
battery during key-off engine soak periods is not included in the 
useable battery energy (UBE) measurement.
iii. Discussion of Changes
    The Agency is adopting in this final rule portions of Appendix B 
and C of the 2017 version of SAE J1634 as the process for determining 
the 5-cycle adjustment factor with modifications. Manufacturers must 
request EPA approval to use the process outlined in the Appendices with 
the following modifications:
     Preconditioning any vehicle components, including the 
propulsion battery and vehicle cabin, is prohibited.
     Beginning in model year 2025, only two UDDS cycles may be 
performed on the CTTP, instead of allowing manufacturers to choose how 
many UDDS cycles to perform up to and including full charge-depletion 
testing on the CTTP.
    The Agency has concluded not to proceed with the proposal for 
performing a charge depleting CTTP while requiring a 10-minute key-off 
soak period between each charge depleting UDDS cycle. The Agency did 
not intend to force BEV manufacturers to perform all new charge 
depletion testing for a single model year. As proposed, the change 
would have created a discrepancy between vehicles tested using the CTTP 
with only one 10-min key-off soak period between the first and second 
UDDS and vehicles testing with a 10-min key-off soak period between all 
UDDS cycles. This would not have been consistent with the Agency's 
objective of maintaining test procedure consistency for fuel economy 
labeling. Therefore, this requirement, which had been proposed for only 
the 2023 model year has been dropped from the final rule.
    The current approved 5-cycle test procedure includes allowing a 
complete charge depleting CTTP to generate data for the city fuel 
economy calculation. As the Agency has gathered data from manufacturers 
performing this test, it has become apparent that the charge depletion 
testing on the CTTP generates fuel consumption data that are not 
representative of the extreme cold start test conditions this test was 
designed to capture. A long-range BEV can complete as many as 50 UDDS 
cycles at -7 [deg]C (20 [deg]F) before depleting the battery. With the 
allowance to skip the 10-minute key off soak period after the second 
UDDS a long-range BEV will reach a stabilized warmed-up energy 
consumption condition after 6 to 10 UDDS cycles. At this point the 
vehicle is warmed-up and will have approximately the same energy 
consumption for each of the remaining 30 to 40 UDDS cycles. The 
averaged energy consumption value from this full charge depletion 
test--as many as 50 UDDS cycles--is entered into the 5-cycle equation 
for the running fuel consumption for the city fuel economy calculation. 
In contrast, for vehicles using fuels other than electricity the 
running fuel consumption is calculated using the values from Bag 2 of 
the first UDDS cycle and Bag 1 of the second UDDS cycle.
    It has become apparent to the Agency that modifications are needed 
to this method to ensure all vehicles are tested under similar 
conditions and use equivalent data for generating fuel economy label 
values. Allowing BEVs to perform a full charge depletion CTTP

[[Page 4457]]

creates test procedure differences between BEVs and non-BEVs. Non-BEVs 
are not allowed to run more than one UDDS cycle followed by one Bag 1 
phase from the second UDDS cycle.
    The intent of the CTTP is to capture the performance of vehicles 
under extreme cold start conditions during short trip city driving. The 
CTTP procedure used by vehicles other than BEVs consists of one UDDS 
cycle (consisting of Bag 1 and Bag 2) followed by a 10-minute key-off 
soak followed by the first 505 seconds (Bag 3) of the second UDDS 
cycle. The data from these three bags are utilized by all vehicles, 
other than BEVs, when calculating the vehicle's city fuel economy (40 
CFR 600.114-12). Allowing BEVs to use a fuel consumption value based on 
fully depleting the battery, while not performing any key-off soaks 
between any UDDS cycle after the second UDDS cycle is not 
representative of short trip urban driving or equivalent to the 
procedure performed by vehicles using fuels other than electricity.
    Based on these observations, the Agency has concluded that allowing 
BEVs to perform full charge depletion testing on the CTTP, with only 
one 10-minute key-off soak occurring between the first and second UDDS 
cycle, does not generate data representative of the vehicles' 
performance during extreme cold start short trip city driving 
conditions. Therefore, starting in model year 2025, EPA will allow BEVs 
to perform only two UDDS cycles with a 10-minute key-off soak between 
them. The final rule includes the following change to the running fuel 
consumption equation for calculating the city fuel economy outlined in 
Appendix C of the 2017 Version of SAE J1634:
[GRAPHIC] [TIFF OMITTED] TR24JA23.003

    In the proposal, EPA sought comment on whether it was reasonable to 
perform two UDDS cycles as part of the CTTP or whether the test should 
conclude after the first 505 seconds (phase 1) of the second UDDS. The 
Agency did not receive any comments on this proposal. The Agency did 
receive comments from stakeholders on related topics: Requesting the 
Agency continue to allow full charge depletion testing for the CTTP; 
requesting the Agency update to the 2021 version of SAE J1634 which 
would allow for battery and cabin preconditioning during the CTTP; and 
requesting the Agency revise the CTTP procedure by utilizing a 
methodology which would stop the CTTP once the vehicle had reached a 
stabilized energy consumption rate.
    As the Agency did not receive comments on the proposal to limit the 
CTTP for BEVs to one UDDS followed by the first phase (505 seconds) of 
the second UDDS after a 10-minute key-off soak, the Agency is not 
adopting this proposal.
    As noted in the preceding paragraphs, the Agency believes allowing 
a full charge depleting test during the CTTP produces data which is not 
representative of short trip urban driving or equivalent to the 
procedure performed by vehicles using fuels other than electricity. The 
intent of the CTTP is to determine the fuel consumption of vehicles 
during short trip urban driving following an extended cold soak at 20 
[deg]F. Data generated from operating a BEV over an entire charge 
depleting test does not represent the fuel consumption of the vehicle 
during the first 2 UDDS cycles. Therefore, the Agency is adopting the 
proposal to replace the charge depleting CTTP for BEV 5-cycle testing 
with a CTTP consisting of 2 UDDS cycles with a 10-minute key-off soak 
between the UDDS cycles.
    The suggestion to allow preconditioning for BEVs during the CTTP 
would result in procedural differences between BEV's and non-BEV CTTP 
testing. The intent of the CTTP is to determine the fuel consumption of 
the vehicle during a short-trip urban drive following an extended soak 
at period at 20 [deg]F, with the vehicle and all powertrain components 
stabilized at 20 [deg]F. While BEVs have technology which will 
precondition the cabin and battery at cold ambient temperatures, this 
technology requires access to a dedicated EVSE along with the operator 
selecting the appropriate mode to enable preconditioning. The Agency 
does not believe a predominance of cold soaks for BEVs with this 
technology will occur where the vehicle has access to a dedicated EVSE 
and the operator will enable the preconditioning mode. The Agency 
policy with respect to fuel economy testing is for the test procedures 
(including the soak period prior to beginning a test) be equivalent for 
all vehicles independent of fuel type. For these reasons the Agency is 
not prepared to adopt the preconditioning provisions of the 2021 
version of SAE J1634.
    The Agency also received a comment proposing to modify the CTTP by 
running repeat UDDS cycles until the energy consumption stabilizes. The 
stabilized energy consumption measured during the last few UDDS cycles, 
along with the energy consumption measured during the first phase of 
the first and second UDDS would be used for the 5-cycle adjustment 
factor calculation. This proposal would reduce the time required to 
perform the CTTP as it would be expected that less than 10 UDDS cycles 
would be required. This proposal would also use the energy consumption 
value measured after the BEV has driven from 3 to 5 or possibly more 
UDDS cycles to represent the energy consumption occurring during short 
trip urban driving. As this procedure uses data taken after the vehicle 
has driven over twenty miles, these data are not representative of 
short trip urban energy consumption.
    The possibility exists that a BEV manufacturer may decide to 
consume stored battery energy to precondition the battery depending on 
the ambient temperature, the battery temperature when the vehicle is 
parked, and other factors. Using stored battery energy for 
preconditioning the battery temperature is not addressed in either EPA 
regulations or SAE J1634. Were a

[[Page 4458]]

manufacturer to implement such a strategy, the Agency would expect the 
energy consumed during the extended cold soak prior to the CTTP would 
need to be considered as DC discharge energy. The BEV CTTP does not 
require measuring DC discharge energy during the extended cold soak 
prior to starting the CTTP drive cycle. It is assumed the BEV goes into 
sleep mode during the cold soak and consumes minimal to no electrical 
energy. If such a strategy was implemented the Agency would want the 
manufacturer to disclose this operation and work with the Agency to 
determine the appropriate means for accounting for this energy use. The 
Agency is not aware of any vehicles which, when not plugged into an 
EVSE, will consume stored energy to maintain the temperature of the 
battery during extended cold soaks.
    The Agency understands the BEV CTTP test procedure and the 5-cycle 
fuel economy equation are different from those that apply for non-BEVs. 
Unlike vehicles using combustion engines, BEVs do not generate 
significant quantities of waste heat from their operation, and 
typically require using stored energy, when not being preconditioned at 
cold ambient temperatures, to produce heat for both the cabin and the 
battery. The Agency expects BEVs will require more than two UDDS cycles 
with a 10-minute key-off soak between them for the vehicle to reach a 
fully warmed up and stabilized operating point. As such, the Agency 
believes it is reasonable to include an additional data point (i.e., 
UDDS2 Bag2) for use in the running fuel consumption equation for BEVs.
    For model year 2025, manufacturers may recalculate the city fuel 
economy for models they are carrying-over using the first two UDDS 
cycles from their prior charge-depletion CTTP test procedures to 
generate new model year 2025 label values. Manufacturers might not want 
to use these data, as the test might not be representative, since the 
vehicle's regeneration capability may be limited by the fully charged 
battery during the first and possibly second UDDS cycles on the CTTP. 
The manufacturer will be able to determine an appropriate state-of-
charge (SoC) and set the battery to that SoC value prior to beginning 
the cold soak for the CTTP. The manufacturer will be required to 
disclose the desired SoC level to the Agency. One possible approach 
consists of charging the vehicle to a level that produces a battery 
state-of-charge (SoC) equivalent to 50 percent following the first UDDS 
cycle. The 2017 version of SAE J1634 refers to this SoC level as the 
mid-point test charge (MC).
    As BEVs have become more efficient and as battery capacities have 
increased over the past decade, the time required to perform CTTP 
charge-depletion testing has dramatically increased. The amendments in 
this final rule will result in significant time savings for 
manufacturers as the BEV CTTP will consist of two UDDS cycles. The test 
also no longer allows charge-depletion testing, which in many instances 
would require multiple shifts to complete. The Agency also believes the 
results obtained from the amended test procedure better represent the 
energy consumption observed during short urban trips under extreme cold 
temperature conditions.
    Based on stakeholder comments and for model years prior to 2025, 
the Agency will continue to allow BEV manufacturers to determine the 5-
cycle adjustment factor using the methods outlined in Appendices B and 
C of the 2017 version of SAE J1634. This option is now included in the 
regulations at Sec.  600.116-12(a)(11).
    The Agency has also included the option for manufacturers to use a 
method developed by the manufacturer, based on good engineering 
judgment, to determine the mid-test constant speed cycle distance. In 
the proposal EPA allowed manufacturers to use one of the two methods in 
Appendix A of SAE J1634 to estimate the mid-test constant speed 
distance. It is apparent to the Agency that manufacturers will have 
additional information and prior development testing experience to 
accurately estimate the mid-test constant speed distance and therefore 
the Agency is including this as an option in Sec.  600.116-12(a)(4).
    The Agency received comments that during the 15 second key-on pause 
between UDDS1 and HFEDS1 and UDDS3 and HFEDS2, the discharge energy 
should be measured and included in the UBE measurement and not applied 
to the HFEDS energy consumption. The Agency agrees with the commentors 
that the energy consumption should not be applied to the HFEDS cycle as 
measurement for this cycle starts just prior to the vehicle beginning 
the drive trace. However, the sampling for the UDDS cycle ends when the 
drive trace for the UDDS cycle reaches 0 mph. Therefore, the 15 second 
key-on pause between the UDDS and HFEDS cycle is not included in either 
the discharge energy consumption for the UDDS or the HFEDS cycle. Since 
UBE is the summation of the cycle discharge energy and since the key-on 
pause energy is not included in either cycle values, the energy 
discharged during this 15-second period is not included in the UBE. 
This same criterion applies to the discharge energy that occurs during 
key-off soak periods as these periods are not measured. This also 
includes the key-off soak periods between phases of the constant-speed 
cycles.
    The Agency has decided to proceed with requiring 5-minute to 30-
minute key-off breaks during constant speed cycles which require more 
than one-hour to complete. The requirements for determining the breaks 
are outlined in Sec. Sec.  600.116-12(a)(5) and 600.116-12(a)(7). The 
specification for the key-off breaks are based on Section 6.6 of the 
2017 version of J1634.
    Based on comments and additional review of SAE J1634 the Agency set 
the key-on pauses and key-off soak periods for the MCT equivalent to 
the times found in Section 8.3.4 of the 2017 version of SAE J1634. The 
Agency received comments indicating a maximum key-off pause time needed 
to be set in the instances where the Agency had previously only 
provided a minimum key-off time. The Agency has set the key-off pause 
times equivalent to the pause times specified in SAE J1634 in Section 
6.6 and Section 8.3.4.
iv. Changes to Procedures for Testing Electric Vehicles
    EPA is updating the regulation from the 2012 version of SAE J1634 
to instead reference the 2017 version of SAE J1634. EPA is also 
including regulatory provisions that amend or clarify the BEV test 
procedures outlined in the 2017 version of SAE J1634 in Sec.  600.116-
12(a). These amendments are intended to minimize test procedure 
variations allowed in the 2017 version, which the Agency has concluded 
can impact test results. For example, the SAE standard allows for the 
constant-speed cycles to be performed as a single phase or broken into 
multiple phases with key-off soak periods. Depending on how the 
constant-speed portion is subdivided, the UBE measurement can vary. The 
regulatory amendments are intended to reduce the variations between 
tests and to improve test-to-test and laboratory-to-laboratory 
repeatability. This final rule includes the following changes:
     Allowing for Administrator approval for vehicles that 
cannot complete the Multi-Cycle Range and Energy Consumption Test (MCT) 
because of the distance required to complete the test or maximum speed 
for the UDDS or HFEDS cycle in Sec.  600.116-12(a)(1).
     In alignment with SAE J1634, Section 6.6 and Section 
8.3.4, key-on pause times and key-off soak times have been set to the 
same minimum and

[[Page 4459]]

maximum values as outlined in SAE J1634 and where key-off soak periods 
have to be conducted with the key or power switch in the ``off'' 
position, the hood closed, and test cell fan(s) off, and the brake 
pedal not depressed as required in Sec. Sec.  600.116-12(a)(2), 
600.116-12(a)(3), 600.116-12(a)(5), and 600.116-12(a)(7).
     Manufacturers predetermine estimates of the mid-test 
constant-speed cycle distance (dM) using the methods in SAE J1634, 
Appendix A or a method developed by the manufacturer using good 
engineering judgment as required in Sec.  600.116-12(a)(4).
     Mid-test constant-speed cycles that do not exceed one hour 
do not need a key-off soak period. If the mid-test constant-speed cycle 
exceeds one hour, the cycle needs to be separated into phases of less 
than one-hour, and a 5-minute to 30-minute key-off soak is needed at 
the end of each phase as required in Sec.  600.116-12(a)(5).
     Using good engineering judgment, end-of-test constant-
speed cycles do not exceed 20 percent of total distance driven during 
the MCT, as described in SAE J1634, Section 8.3.3 is required in Sec.  
600.116-12(a)(6).
     End-of-test constant-speed cycles that do not exceed one 
hour do not a need key-off soak period. If the end-of-test constant-
speed cycle exceeds one hour, the cycle needs to be separated into 
phases of less than one-hour, and a 5-minute to 30-minute key-off soak 
is needed at the end of each phase as required in and 600.116-12(a)(7).
     Recharging the vehicle's battery must start within three 
hours after testing as required in Sec.  600.116-12(a)(9).
     The Administrator may approve a manufacturer's request to 
use an earlier version of SAE J1634 for carryover vehicles as required 
in Sec.  600.116-12(a)(10).
     All label values related to fuel economy, energy 
consumption, and range must be based on 5-cycle testing, or values must 
be adjusted to be equivalent to 5-cycle results. Manufacturers may 
request Administrator approval to use SAE J1634, Appendix B and 
Appendix C for determining 5-cycle adjustment factors as required in 
Sec.  600.116-12(a)(11).
2. Additional Light-Duty Changes Related to Certification Requirements 
and Measurement Procedures
    This final rule includes the following additional amendments 
related to criteria standards and general certification requirements, 
which we are finalizing as proposed unless specifically noted 
otherwise:
     40 CFR part 85, subpart V: Correcting the warranty periods 
identified in the regulation to align with the Clean Air Act, as 
amended, and clarifying that the warranty provisions apply to both 
types of warranty specified in CAA section 207(a) and (b)--an emission 
defect warranty and an emission performance warranty. EPA adopted 
warranty regulations in 1980 to apply starting with model year 1981 
vehicles (45 FR 34802, May 22, 1980). The Clean Air Act as amended in 
1990 changed the warranty period for model year 1995 and later light-
duty vehicles and light-duty trucks to 2 years or 24,000 miles of use 
(whichever occurs first), except that a warranty period of 8 years or 
80,000 miles applied for specified major emission control components.
     Section 86.117-96: Revising paragraph (d)(1), which 
describes how to calculate evaporative emissions from methanol-fueled 
vehicles. The equation in the regulation inadvertently mimics the 
equation used for calculating evaporative emissions from gasoline-
fueled vehicles. We are revising the equation to properly represent the 
fuel-specific calculations in a way that includes temperature 
correction for the sample volume based on the sample and SHED 
temperatures. The final rule includes a correction to a typographical 
error in the equation from the proposed rule.
     Section 86.143-96: We are finalizing changes to the 
equation for calculating methanol mass emissions. A commenter pointed 
out that this equation is the same as the one we proposed to correct in 
40 CFR 86.117-96.
     Section 86.1810: Clarifying the certification 
responsibilities for cases involving small-volume manufacturers that 
modify a vehicle already certified by a different company and recertify 
the modified vehicle to the standards that apply for a new vehicle 
under 40 CFR part 86, subpart S. Since the original certifying 
manufacturer accounts for these vehicles in their fleet-average 
calculations, these secondary vehicle manufacturers should not be 
required to repeat those fleet-average calculations for the affected 
vehicles. This applies to fleet average standards for criteria exhaust 
emissions, evaporative emissions, and greenhouse gas emissions. The 
secondary vehicle manufacturer would need to meet all the same bin 
standards and family emission limits as specified by the original 
certifying manufacturer.
     Section 86.1819-14: Clarifying that the definition of 
``engine code'' for implementing heavy-duty greenhouse gas standards 
(Class 2b and 3) is the same ``engine code'' definition that applies to 
light-duty vehicles in the part 600 regulations.
     Section 86.1823-08: Revising to specify a simulated test 
weight based on Loaded Vehicle Weight for light light-duty trucks (LDT1 
and LDT2). The regulation inadvertently applies adjusted loaded vehicle 
weight, which is substantially greater and inappropriate for light 
light-duty trucks because they are most often used like lightly loaded 
passenger vehicles rather than cargo-carrying commercial trucks. In 
practice, we have been allowing manufacturers to implement test 
requirements for these vehicles based on Loaded Vehicle Weight. This 
revision is responsive to manufacturers' request to clarify test 
weights for the affected vehicles.
     Section 86.1843-01(f)(2): Delaying the end-of-year 
reporting deadline to May 1 following the end of the model year. 
Manufacturers requested that we routinely allow for later submissions 
instead of setting the challenging deadline of January 1 and allowing 
extensions.
    We are adopting the following additional amendments related to 
greenhouse gas emissions and fuel economy testing:
     Section 86.1823-12: Revising paragraph (m)(1) to reflect 
current practices with respect to CO2 durability 
requirements. The revisions clarify how certification and testing 
procedures apply in areas that are not entirely specified in current 
regulations. The amendments in this final rule reflect the procedures 
EPA and manufacturers have worked out in the absence of the detailed 
regulatory provisions. For example, while conventional vehicles 
currently have a multiplicative CO2 deterioration factor of 
one or an additive deterioration factor of zero to determine full 
useful life emissions for FTP and highway fuel economy tests, many 
plug-in hybrid electric vehicles have non-zero additive CO2 
deterioration factors (or manufacturers perform fuel economy tests 
using aged components). These changes have no impact on conventional 
vehicles, but they strengthen the CO2 durability 
requirements for plug-in hybrid electric vehicles. In response to a 
comment, we are revising the regulation for the final rule to 
specifically name batteries as one of the aged components to install on 
a test vehicle, rather than referring generically to ``aged 
components.''
     Section 600.001: Clarifying that manufacturers should send 
reports and requests for approval to Designated

[[Page 4460]]

Compliance Officer, which we are defining in 40 CFR 600.002.
     Section 600.002: Revising the definition of ``engine 
code'' to refer to a ``test group'' instead of an ``engine-system 
combination''. This change reflects updated terminology corresponding 
to current certification procedures.
     Part 600, subpart B: Updating test procedures with 
references to 40 CFR part 1066 to reflect the migration of procedures 
from 40 CFR part 86, subpart B. The migrated test procedures allow us 
to delete the following obsolete regulatory sections: 600.106, 600.108, 
600.109, 600.110, and 600.112, along with references to those sections.
     Sections 600.115 and 600.210: EPA issued guidance in 2015 
for the fuel economy program to reflect technology trends.\589\ We are 
amending the regulation to include these changes. First, as outlined in 
the EPA guidance letter and provisions of 40 CFR 600.210-12(a)(2)(iv), 
``[t]he Administrator will periodically update the slopes and 
intercepts through guidance and will determine the model year that the 
new coefficients must take effect.'' Thus, we are updating the 
coefficients used for calculating derived 5-cycle city and highway mpg 
values in 40 CFR 600.210 to be consistent with the coefficients 
provided in the 2015 EPA guidance letter and to be more representative 
of the fuel economy characteristics of the current fleet. Second, for 
reasons discussed on page 2 of the EPA guidance letter, we are amending 
40 CFR 600.115 to allow manufacturers to calculate derived 5-cycle fuel 
economy and CO2 emission values using a factor of 0.7 only 
for battery electric vehicles, fuel cell vehicles, and plug-in hybrid 
electric vehicles (during charge depleting operation only).
---------------------------------------------------------------------------

    \589\ ``Derived 5-cycle Coefficients for 2017 and Later Model 
Years'', EPA Guidance Document CD-15-15, June 22, 2015.
---------------------------------------------------------------------------

     Section 600.210: The regulation already allows 
manufacturers to voluntarily decrease fuel economy values and raise 
CO2 emission values if they determine that the values on the 
fuel economy label do not properly represent in-use performance. The 
expectation is that manufacturers would prefer not to include label 
values that create an unrealistic expectation for consumers. We are 
adding a condition that the manufacturer may adjust these values only 
if the manufacturer changes both values and revises any other affected 
label value accordingly for a model type (including but not limited to 
the fuel economy 1-10 rating, greenhouse gas 1-10 rating, annual fuel 
cost, and 5-year fuel cost information). We are also extending these 
same provisions for electric vehicles and plug-in hybrid electric 
vehicles based on both increasing energy consumption values and 
lowering the electric driving range values.
     Section 600.311: Adding clarifying language to reference 
the adjusted driving ranges to reflect in-use driving conditions. These 
adjusted values are used for fuel economy labeling. For plug-in hybrid 
electric vehicles, we are also correcting terminology from ``battery 
driving range'' to ``adjusted charge-depleting driving range 
(Rcda)'' for clarity and to be consistent with the terms 
used in SAE Recommended Practice J1711. The final rule includes 
adjustments to the wording of the amendments in 40 CFR 600.311 for 
greater clarity and consistency.
     Section 600.510-12: Providing a more detailed cross 
reference to make sure manufacturers use the correct equation for 
calculating average combined fuel economy.
     Section 600.512-12: Delaying the deadline for the model 
year report from the end of March to May 1 to align the deadline 
provisions with the amendment for end-of-year reporting as described in 
40 CFR 86.1843-01(f)(2).
    See Section 32.2 of the Response to Comments for a discussion of 
comments related to these amendments for the light-duty program in 40 
CFR part 85, 40 CFR part 86, subpart S, and 40 CFR part 600.
    Note that we are adopting additional amendments to 40 CFR part 86, 
subparts B and S, that are related to the new refueling emission 
standards for heavy-duty vehicles described in section III.E of this 
preamble.

F. Large Nonroad Spark-Ignition Engines (40 CFR Part 1048)

    EPA's emission standards and certification requirements for land-
based nonroad spark-ignition engines above 19 kW are set out in 40 CFR 
part 1048. We are adopting the following amendments to part 1048:
     Section 1048.501: Correct a mistaken reference to duty 
cycles in appendix II.
     Section 1048.620: Remove obsolete references to 40 CFR 
part 89.
    We received no comments on these proposed amendments and are 
finalizing the proposed changes without modification.

G. Small Nonroad Spark-Ignition Engines (40 CFR Part 1054)

    EPA's emission standards and certification requirements for land-
based nonroad spark-ignition engines at or below 19 kW (``Small SI 
engines'') are set out in 40 CFR part 1054. We recently proposed 
several amendments to part 1054 (85 FR 28140, May 12, 2020). Comments 
submitted in response to that proposed rule suggested additional 
amendments related to testing and certifying these Small SI engines. 
The following discussion describes several amendments that are 
responsive to these suggested additional amendments. Otherwise, we are 
finalizing the provisions as proposed, except as specifically noted.
1. Engine Test Speed
    The duty cycle established for nonhandheld Small SI engines 
consists of six operating modes with varying load, and with engine 
speed corresponding to typical governed speed for the intended 
application. This generally corresponds to an ``A cycle'' with testing 
at 3060 rpm to represent a typical operating speed for a lawnmower, and 
a ``B cycle'' with testing at 3600 rpm to represent a typical operating 
speed for a generator. While lawnmowers and generators are the most 
common equipment types, there are many other applications with widely 
varying speed setpoints.
    In 2020, we issued guidance to clarify manufacturers' testing 
responsibilities for the range of equipment using engines from a given 
emission family.\590\ We are adopting the provisions described in that 
guidance document. This includes two main items. First, we are amending 
the regulation at 40 CFR 1054.801 to identify all equipment in which 
the installed engine's governed speed at full load is at or above 3400 
rpm as ``rated-speed equipment'', and all equipment in which the 
installed engine's governed speed at full load is below 3330 rpm as 
``intermediate-speed equipment''. For equipment in which the installed 
engine's governed speed at full load is between 3330 and 3400 rpm, the 
engine manufacturer may consider that to be either ``rated-speed 
equipment'' or ``intermediate-speed equipment''. This allows 
manufacturers to reasonably divide their engine models into separate 
families for testing only on the A cycle or the B cycle, as 
appropriate. For emission families including both rated-speed equipment 
and intermediate-speed equipment, manufacturers must measure emissions 
over both the A cycle and the B cycle

[[Page 4461]]

and certify based on the worst-case HC+NOX emission results.
---------------------------------------------------------------------------

    \590\ ``Small Spark-Ignition Nonhandheld Engine Test Cycle 
Selection,'' EPA guidance document CD-2020-06, May 11, 2020.
---------------------------------------------------------------------------

    Second, we are limiting the applicability of the A cycle to engines 
with governed speed at full load that is at or above 2700 rpm, and 
limiting the applicability of the B cycle to engines with governed 
speed at full load that is at or below 4000 rpm. These values represent 
an approximate 10 percent variation from the nominal test speed. For 
engines with governed speed at full load outside of these ranges, we 
will require that manufacturers use the provisions for special 
procedures in 40 CFR 1065.10(c)(2) to identify suitable test speeds for 
those engines. Manufacturers may take reasonable measures to name 
alternate test speeds to represent multiple engine configurations and 
equipment installations.
    See Section 32.3 of the Response to Comments for a discussion of 
the comments submitted regarding test selection.
2. Steady-State Duty Cycles
    As noted in Section XI.G.1, the duty cycle for nonhandheld engines 
consists of a six-mode duty cycle that includes idle and five loaded 
test points. This cycle is not appropriate for engines designed to be 
incapable of operating with no load at a reduced idle speed. For many 
years, we have approved a modified five-mode duty cycle for these 
engines by removing the idle mode and reweighting the remaining five 
modes. We are adopting that same alternative duty cycle into the 
regulation and requiring manufacturers to use it for all engines that 
are not designed to idle. For emission families that include both types 
of engines, manufacturers must measure emissions over both the six-mode 
and five-mode duty cycles and certify based on the worst-case 
HC+NOX emission results.
    We are adopting the proposed changes without modification, except 
that we are adding a clarifying note to limit the reporting requirement 
to the worst-case value if a manufacturer performs tests both with and 
without idle. See Section 32.4 of the Response to Comments.
    The discussion in Section XI.G.1 applies equally for nonhandheld 
engines whether or not they are designed to idle. As a result, if an 
emission family includes engines designed for idle with governed speeds 
corresponding to rated-speed equipment and intermediate-speed 
equipment, and engines in the same emission family that are not 
designed to idle have governed speeds corresponding to rated-speed 
equipment and intermediate-speed equipment, the manufacturer must 
perform A cycle and B cycle testing for both the six-mode duty cycle 
and the five-mode duty cycle. Manufacturers would then perform those 
four sets of emission measurements and certify based on the worst-case 
HC+NOX emission results.
    The nonhandheld six-mode duty cycle in appendix II to 40 CFR part 
1054 includes an option to do discrete-mode or ramped-modal testing. 
The ramped-modal test method involves collecting emissions during the 
established modes and defined transition steps between modes to allow 
manufacturers to treat the full cycle as a single measurement. However, 
no manufacturer has ever used ramped-modal testing. This appears to be 
based largely on the greater familiarity with discrete-mode testing and 
on the sensitivity of small engines to small variations in speed and 
load. Rather than increasing the complexity of the regulation by 
multiplying the number of duty cycles, we are removing the ramped-modal 
test option for the six-mode duty cycle.
3. Engine Family Criteria
    Manufacturers requested that we allow open-loop and closed-loop 
engines to be included together in a certified emission family, with 
the testing demonstration for certification based on the worst-case 
configuration.
    The key regulatory provision for this question is in 40 CFR 
1054.230(b)(8), which says that engine configurations can be in the 
same emission family if they are the same in the ``method of control 
for engine operation, other than governing (mechanical or 
electronic)''.
    Engine families are intended to group different engine models and 
configurations together if they will have similar emission 
characteristics throughout the useful life. The general description of 
an engine's ``method of control for engine operation'' requires that 
EPA apply judgment to establish which fuel-system technologies should 
be eligible for treating together in a single engine family. We have 
implemented this provision by allowing open-loop and closed-loop engine 
configurations to be in the same emission family if they have the same 
design values for spark timing and targeted air-fuel ratio. This 
approach allows us to consider open-loop vs. closed-loop configurations 
as different ``methods of control'' when the engines have fundamentally 
different approaches for managing combustion. We do not intend to 
change this current practice and we are therefore not amending 40 CFR 
1054.230 to address the concern about open-loop and closed-loop engine 
configurations.
    The existing text of 40 CFR 1054.230(b)(8) identifies ``mechanical 
or electronic'' control to be fundamental for differentiating emission 
families. However, as is expected for open-loop and closed-loop 
configurations, we expect engines with electronic throttle-body 
injection and mechanical carburetion to have very similar emission 
characteristics if they have the same design values for spark timing 
and targeted air-fuel ratio. A more appropriate example to establish a 
fundamental difference in method of control is the contrast between 
port fuel injection and carburetion (or throttle-body injection). We 
are therefore revising the regulation with this more targeted example. 
This revision allows manufacturers to group engine configurations with 
carburetion and throttle-body injection into a shared emission family 
as long as they have the same design values for spark timing and 
targeted air-fuel ratio.
    We are adopting the proposed changes without modification. See 
Section 32.5 of the Response to Comments for a discussion of the 
comments submitted regarding engine family criteria.
4. Miscellaneous Amendments for Small Nonroad Spark-Ignition Engines
    We are adopting the following additional amendments to 40 CFR part 
1054:
     Section 1054.115: Revising the description of prohibited 
controls to align with similar provisions from the regulations that 
apply for other sectors.
     Section 1054.505(b)(1)(i): Correcting typographical 
errors.
     Appendix I: Clarifying that requirements related to 
deterioration factors, production-line testing, and in-use testing did 
not apply for Phase 1 engines certified under 40 CFR part 90.
    We received no comments on these proposed provisions and are 
finalizing the proposed changes without modification.

H. Recreational Vehicles and Nonroad Evaporative Emissions (40 CFR 
Parts 1051 and 1060)

    EPA's emission standards and certification requirements for 
recreational vehicles are set out in 40 CFR part 1051, with additional 
specifications for evaporative emission standards in 40 CFR part 1060. 
We are adopting the following amendments to parts 1051 and 1060:
     Section 1051.115(d): Aligning the time and cost 
specification related to air-fuel adjustments with those that

[[Page 4462]]

apply for physically adjustable parameters we are adopting in 40 CFR 
1068.50(e)(1) in this final rule. This creates a uniform set of 
specifications for time and cost thresholds for all types of adjustable 
parameters.
     Sections 1051.501(c) and 1060.515(c) and (d): Creating an 
exception to the ambient temperature specification for fuel-line 
testing to allow for removing the test article from an environmental 
chamber for daily weight measurements. This amendment aligns with our 
recent change to allow for this same exception in the measurement 
procedure for fuel tank permeation (86 FR 34308, June 29, 2021).
     Section 1051.501(c): Specifying that fuel-line testing 
involves daily weight measurements for 14 days. This is consistent with 
the specifications in 40 CFR 1060.515. This amendment codifies EPA's 
guidance to address these test parameters that are missing from the 
referenced SAE J30 test procedure.\591\
---------------------------------------------------------------------------

    \591\ ``Evaporative Permeation Requirements for 2008 and Later 
Model Year New Recreational Vehicles and Highway Motorcycles'', EPA 
guidance document CD-07-02, March 26, 2007.
---------------------------------------------------------------------------

     Section 1051.501(d): Updating referenced procedures. The 
referenced procedure in 40 CFR 1060.810 is the 2006 version of ASTM 
D471. We inadvertently left the references in 40 CFR 1051.501 to the 
1998 version of ASTM D471. Citing the standard without naming the 
version allows us to avoid a similar error in the future.
     Section 1051.515: Revising the soak period specification 
to allow an alternative of preconditioning fuel tanks at 43  5 [deg]C for 10 weeks. The existing regulation allows for a soak 
period that is shorter and higher temperature than the specified soak 
of 28  5 [deg]C for 20 weeks. This approach to an 
alternative soak period is the same as what is specified in 40 CFR 
1060.520(b)(1).
     Section 1060.520: Adding ``'' where that was 
inadvertently omitted in describing the temperature range that applies 
for soaking fuel tanks for 10 weeks.
    We are adopting an additional amendment related to snowmobile 
emission standards. The original exhaust emission standards for 
snowmobiles in 40 CFR 1051.103 included standards for NOX 
emissions. However, EPA removed those NOX emission standards 
in response to an adverse court decision.\592\ We are therefore 
removing the reference to NOX emissions in the description 
of emission credits for snowmobiles in 40 CFR 1051.740(b).
---------------------------------------------------------------------------

    \592\ ``Bluewater Network vs. EPA, No. 03-1003, September Term, 
2003'' Available here: https://www.govinfo.gov/content/pkg/USCOURTS-caDC-03-01249/pdf/USCOURTS-caDC-03-01249-0.pdf. The Court found that 
the EPA had authority to regulate CO under CAA 213(a)(3) and HC 
under CAA 213(a)(4), but did not have authority to regulate 
NOX under CAA 213(a)(4) as it was explicitly referred to 
in CAA 213(a)(2) and CAA 213(a)(4) only grants authority to regulate 
emissions ``not referred to in paragraph (2).''
---------------------------------------------------------------------------

    We received no comments on the proposed provisions for recreational 
vehicles and are finalizing the proposed changes without modification.

I. Marine Diesel Engines (40 CFR Parts 1042 and 1043)

    EPA's emission standards and certification requirements for marine 
diesel engines under the CAA are in 40 CFR part 1042. Emission 
standards and related fuel requirements that apply internationally are 
in 40 CFR part 1043. We are finalizing the amendments in 40 CFR parts 
1042 and 1043 as proposed, except as specifically noted.
1. Production-Line Testing
    Engine manufacturers have been testing production engines as 
described in 40 CFR part 1042. This generally involves testing up to 1 
percent of production engines for engine families with production 
volumes greater than 100 engines. We adopted these testing provisions 
in 1999 with the expectation that most families would have production 
volumes greater than 100 engines per year (64 FR 73300, December 29, 
1999). That was the initial rulemaking to set emission standards for 
marine diesel engines. As a result, there was no existing certification 
history to draw on for making good estimates of the number of engine 
families or the production volumes in those engine families. Now that 
we have almost 20 years of experience in managing certification for 
these engines, we can observe that manufacturers have certified a few 
engine families with production volumes substantially greater than 100 
engines per year, but many engine families are not subject to 
production-line testing because production volumes are below 100 
engines per year. As a result, manufacturers test several engines in 
large engine families, but many engine families have no production-line 
testing at all.
    We are revising the production-line testing regimen for marine 
diesel engines to reflect a more tailored approach. The biggest benefit 
of production-line testing for this sector is to confirm that engine 
manufacturers can go beyond the prototype engine build for 
certification and move to building compliant engines in a production 
environment. From this perspective, the first test is of most value, 
with additional tests adding assurance of proper quality control 
procedures for ongoing production. Additional testing might also add 
value to confirm that design changes and updated production practices 
over time do not introduce problems.
    Testing is based on a default engine sampling rate of one test per 
family. An engine test from an earlier year counts as a sufficient 
demonstration for an engine family, as long as the manufacturer 
certifies the engine family using carryover emission data. At the same 
time, we are removing the testing exemption for small-volume engine 
manufacturers and low-volume engine families. In summary, this 
approach:
     Removes the testing exemption for low-volume families and 
small-volume manufacturers, and remove the 1 percent sampling rate. The 
amendments revise the engine sampling instruction to require one test 
for each family. A test from a prior year can meet the test requirement 
for carryover families. This includes tests performed before these 
changes to the regulation become effective. This may also involve 
shared testing for recreational and commercial engine families if they 
rely on the same emission-data engine.
     Requires a single test engine randomly selected early in 
the production run. EPA may direct the manufacturer to select a 
specific configuration and build date. The manufacturer continues to be 
subject to the requirement to test two more engines for each failing 
engine, and notify EPA if an engine family fails.
     Requires a full test report within 45 days after testing 
is complete for the family. There are no additional quarterly or annual 
reports.
     Allows manufacturers to transition to the new test 
requirements by spreading out tests over multiple years if several 
engine families are affected. Small-volume engine manufacturers need to 
test no more than two engine families in a single model year, and other 
engine manufacturers need to test no more than four engine families in 
a single model year.
     Allows EPA to withhold approval of a request for 
certification for a family for a given year if PLT work from the 
previous model year is not done.
     Preserves EPA's ability to require an additional test in 
the same model year or a later model year for cause even after there 
was a passing result based on any reasonable suspicion that engines may 
not meet emission standards.
    The proposed rule described how the amended regulatory provisions 
in this

[[Page 4463]]

rule are different than what we included in an earlier draft document 
in anticipation of the proposed regulations.
    An EPA decision to require additional testing for cause would 
include a more detailed description to illustrate the types of concerns 
leading us to identify the need for additional testing. Reporting 
defects for an engine family would raise such a concern. In addition, 
amending applications for certification might also raise concerns.\593\ 
Decreasing an engine family's Family Emission Limit without submitting 
new emission data would be a concern because the manufacturer would 
appear to be creating credits from what was formerly considered a 
necessary compliance margin. Changing suppliers or specifications for 
critical emission-related components would raise concerns about whether 
the emission controls system is continuing to meet performance 
expectations. Adding a new or modified engine configuration always 
involves a judgment about whether the original test data continue to 
represent the worst-case configuration for the expanded family. In any 
of these cases, we may direct the manufacturer to perform an additional 
test with a production engine to confirm that the family meets emission 
standards. In addition to these specific concerns, we expect 
manufacturers to have a greater vigilance in making compliant products 
if they know that they may need to perform additional testing. 
Conversely, removing the possibility of further testing for the 
entirety of a production run spanning several years could substantially 
weaken our oversight presence to ensure compliance.
---------------------------------------------------------------------------

    \593\ In this context, making the described changes in an 
application for certification applies equally for running changes 
within a model year and for changes that are introduced at the start 
of a new model year.
---------------------------------------------------------------------------

    The net effect of the changes for production-line testing will be a 
substantial decrease in overall testing. We estimate industry-wide 
testing will decrease by about 30 engines per year. Spreading test 
requirements more widely across the range of engine families should 
allow for a more effective program in spite of the reduced testing 
rate. We acknowledge that some individual companies will test more 
engines; however, by limiting default test rates to one per engine 
family, including future years, this represents a small test burden 
even for the companies with new or additional testing requirements.
    We are adopting two additional clarifications related to 
production-line testing. First, we are clarifying that test results 
from the as-built engine are the final results to represent that 
engine. Manufacturers may modify the test engine to develop alternative 
strategies or to better understand the engine's performance; however, 
testing from those modified engines do not represent the engine family 
unless the manufacturer changes their production processes for all 
engines to match those engine modifications. Testing modified engines 
to meet production-line testing obligations counts as a separate engine 
rather than replacing the original test results.
    Second, we are clarifying that Category 3 auxiliary engines 
exempted from EPA certification under part 1042 continue to be subject 
to production-line testing under 40 CFR 1042.305. This question came up 
because we recently amended 40 CFR 1042.650(d) to allow Category 3 
auxiliary engines installed in certain ships to meet Annex VI 
certification requirements instead of EPA certification requirements 
under part 1042 (86 FR 34308, June 29, 2021). As with Category 1 and 
Category 2 engines covered by production-line testing requirements in 
40 CFR 1042.301, these test requirements apply for all engines subject 
to part 1042, even if they are not certified under part 1042.
    Third, we are clarifying that manufacturers need to test engines 
promptly after selecting them for production-line testing. This is 
intended to allow flexibility where needed, for example, if engines 
need to be transported to an off-site laboratory for testing. Except 
for meeting those logistical needs, we would expect manufacturers to 
prioritize completion of their test requirements to allow for a timely 
decision for the family. While we did not propose this edit, adding the 
textual clarification to the final rule is consistent with EPA's 
expectation and the intent of the original provisions. This edit adds 
clarity without creating any new or additional test burden.
    We received no comments on the proposed amendments related to 
production-line testing and are finalizing these provisions as 
proposed, except as noted for the timing of performing tests.
2. Applying Reporting Requirements to EGR-Equipped Engines
    EPA received comments suggesting that we apply the SCR-related 
monitoring and reporting requirements in 40 CFR 1042.660(b) to engines 
that instead use exhaust gas recirculation (EGR) to meet Tier 4 
standards. We understand SCR and EGR to be fundamentally different in 
ways that lead us not to make this suggested change.
i. Maintenance
    There are two principal modes of EGR failure: (1) Failure of the 
valve itself (physically stuck or not able to move or adjust within 
normal range) and (2) EGR cooler fouling. EGR cooler maintenance is 
typically listed in the maintenance instructions provided by engine 
manufacturers to owners. If done according to the prescribed schedule, 
this should prevent fouling of the EGR cooler. Similarly, EGR valves 
typically come with prescribed intervals for inspection and 
replacement. For both components, the intervals are long and occur at 
the time that other maintenance is routinely performed. Under 40 CFR 
1042.125(a)(2), the minimum interval for EGR-related filters and 
coolers is 1500 hours, and the minimum interval for other EGR-related 
components is either 3000 hours or 4500 hours depending on the engine's 
max power.
    In contrast, SCR systems depend on the active, ongoing involvement 
of the operator to maintain an adequate supply of Diesel Exhaust Fluid 
(DEF) as a reductant to keep the catalyst functioning properly. EPA 
does not prescribe the size of DEF storage tanks for vessels, but the 
engine manufacturers provide installation instructions with 
recommendations for tank sizing to ensure that enough DEF is available 
onboard for the duration of a workday or voyages between ports. At the 
frequencies that this fluid needs replenishing, it is not expected that 
other routine maintenance must also be performed, aside from refueling.
    DEF consumption from marine diesel engines is estimated to be 3-8 
percent of diesel fuel consumption. Recommended DEF tank sizes are 
generally about 10 percent of the onboard fuel storage, with the 
expectation that operators refill DEF tanks during a refueling event.
    Another point of contrast is that SCR systems have many failure 
modes in addition to the failure to maintain an adequate supply of 
reductant. For example, dosing may stop due to faulty sensors, 
malfunctions of components in the reductant delivery system, or 
freezing of the reductant.
    Over the years of implementing regulations for which SCR is the 
adopted technology, EPA has produced several guidance documents to 
assist manufacturers in developing approvable SCR engine designs.\594\ 
\595\ \596\ Many of

[[Page 4464]]

the features implemented to assure that SCR systems are properly 
maintained by vehicle and equipment operators are not present with 
systems on marine vessels. Thus, we rely on the reporting provision of 
40 CFR 1042.660(b) to enhance our assurance that maintenance will occur 
as prescribed.
---------------------------------------------------------------------------

    \594\ ``Revised Guidance for Certification of Heavy-Duty Diesel 
Engines Using Selective Catalyst Reduction (SCR) Technologies'', EPA 
guidance document CISD-09-04, December 30, 2009.
    \595\ ``Nonroad SCR Certification'', EPA Webinar Presentation, 
July 26, 2011.
    \596\ ``Certification of Nonroad Diesel Engines Equipped with 
SCR Emission Controls'', EPA guidance document CD-14-10, May 12, 
2014.
---------------------------------------------------------------------------

ii. Tampering
    Engine manufacturers and others have asked questions about 
generation of condensate from an EGR-equipped engine. This condensate 
is an acidic liquid waste that must be discharged in accordance with 
water quality standards (and IMO, U.S. Coast Guard, and local port 
rules). The Tier 4 EGR-equipped engines that EPA has certified are 
believed to generate a very small amount of EGR condensate. Larger 
quantities of condensate may be generated from an aftercooler, but that 
is non-acidic, non-oily water that generally does not need to be held 
onboard or treated. In the absence of compelling information to the 
contrary, we believe the burden of storing, treating, and discharging 
the EGR condensate is not great enough to motivate an operator to 
tamper with the engine.
    Most EGR-equipped engines have internal valves and components that 
are not readily accessible to operators. In these cases, the controls 
to activate or deactivate EGR are engaged automatically by the engine's 
electronic control module and are not vulnerable to operator tampering. 
Where an engine design has external EGR, even though emission-related 
components may be somewhat accessible to operators, the controls are 
still engaged automatically by the engine's electronic control module 
and continued compliance is ensured if prescribed maintenance is 
performed on schedule and there is no tampering.
iii. Nature of the Risk
    There are five manufacturers actively producing hundreds of 
certified Category 1 marine diesel engines each year using EGR to 
achieve Tier 3 emission standards. EPA is aware of no suggestion that 
these EGR controls are susceptible to tampering or malmaintenance.
    There is one manufacturer who has certified two Category 3 marine 
diesel engine families using EGR to achieve the Tier 3 emission 
standards for these large engines. If there is any risk with these, 
it's that the ocean-going vessel may not visit an ECA often enough to 
exercise the EGR valve and prevent it from getting corroded or stuck. 
These engines are already subject to other onboard diagnostics and 
reporting requirements, so we expect no need to expand 40 CFR 
1042.660(b) for these engines.
    There is one manufacturer producing Category 2 marine diesel 
engines using EGR to achieve the Tier 4 emission standards. We again do 
not see the need to include them in the reporting scheme in 40 CFR 
1042.660(b).
3. Miscellaneous Amendments for Marine Diesel Engines
    We are adopting the following additional amendments for our marine 
diesel engine program, which we are finalizing as proposed unless 
specifically noted otherwise:
     Sections 1042.110 and 1042.205: Revising text to refer to 
``warning lamp'' instead of ``malfunction indicator light'' to prevent 
confusion with conventional onboard diagnostic controls. This aligns 
with changes adopted for land-based nonroad diesel engines in 40 CFR 
part 1039. We are also clarifying that the manufacturer's description 
of the diagnostic system in the application for certification needs to 
identify which communication protocol the engine uses.
     Section 1042.110: Revising text to refer more broadly to 
detecting a proper supply of Diesel Exhaust Fluid to recognize, for 
example, that a closed valve may interrupt the supply (not just an 
empty tank).
     Section 1042.115: Revising provisions related to 
adjustable parameters, as described in Section XI.H.1.
     Section 1042.115: Adding provisions to address concerns 
related to vanadium sublimation, as described in Section XI.B.
     Section 1042.615: Clarifying that engines used to repower 
a steamship may be considered to qualify for the replacement engine 
exemption. This exemption applies relative to EPA standards in 40 CFR 
part 1042. We are also amending 40 CFR 1043.95 relative to the 
application of MARPOL Annex VI requirements for repowering Great Lakes 
steamships.
     Section 1042.660(b): Revising the instruction for 
reporting related to vessel operation without reductant for SCR-
equipped engines to describe the essential items to be reported, which 
includes the cause, the remedy, and an estimate of the extent of 
operation without reductant. We are also revising the contact 
information for reporting, and to clarify that the reporting 
requirement applies equally for engines that meet standards under 
MARPOL Annex VI instead of or in addition to meeting EPA standards 
under part 1042. We are also aware that vessel owners may choose to 
voluntarily add SCR systems to engines certified without 
aftertreatment; we are clarifying that the reporting requirement of 40 
CFR 1042.660(b) does not apply for these uncertified systems. These 
changes are intended to clarify the reporting instructions for 
manufacturers under this provision rather than creating a new reporting 
obligation. In response to a question raised after the proposal, we 
note that the regulatory text requires reporting under 40 CFR 
1042.660(b) for any vessel operation without the appropriate reductant, 
regardless of what caused the noncompliance.
     Section 1042.901: Clarifying that the displacement value 
differentiating Category 1 and Category 2 engines subject to Tier 1 and 
Tier 2 standards was 5.0 liters per cylinder, rather than the value of 
7.0 liters per cylinder that applies for engines subject to Tier 3 and 
Tier 4 standards.
     Part 1042, appendix I: Correcting the decimal places to 
properly identify the historical Tier 1 and Tier 2 p.m. standards for 
19-37 kW engines.
     Section 1043.20: Revising the definition of ``public 
vessel'' to clarify how national security exemptions relate to 
applicability of requirements under MARPOL Annex VI. Specifically, 
vessels with an engine-based national security exemption are exempt 
from NOX standards under MARPOL Annex VI, and vessels with a 
fuel-based national security exemption are exempt from the fuel 
standards under MARPOL Annex VI. Conversely, an engine-based national 
security exemption does not automatically exempt a vessel from the fuel 
standards under MARPOL Annex VI, and a fuel-based national security 
exemption does not automatically exempt a vessel from the 
NOX standards under MARPOL Annex VI. These distinctions are 
most likely to come into play for merchant marine vessels that are 
intermittently deployed for national (noncommercial) service.
     Section 1043.55: Revising text to clarify that U.S. Coast 
Guard is the approving authority for technologies that are equivalent 
to meeting sulfur standards under Regulation 4 of MARPOL Annex VI.
     Section 1043.95: Expanding the Great Lakes steamship 
provisions to allow for engine repowers to qualify for an exemption 
from the Annex VI Tier III

[[Page 4465]]

NOX standard. This amendment allows EPA to approve a ship 
owner's request to install engines meeting the IMO Tier II 
NOX standard. Consistent with EPA's determination for EPA 
Tier 4 engines replacing engines certified to earlier tiers of 
standards under 40 CFR 1042.615(a)(1), we understand that engines 
certified to the Annex VI Tier III NOX standard may not have 
the appropriate physical or performance characteristics to replace a 
steamship's powerplant. This new provision is therefore intended to 
create an incentive for shipowners to upgrade the vessel by replacing 
steam boilers with IMO Tier II engines, with very substantial expected 
reductions in NOX, PM, and CO2 emissions compared 
to emission rates from continued operation as steamships. We are also 
simplifying the fuel-use exemption for Great Lakes steamships to allow 
for continued use of high-sulfur fuel for already authorized 
steamships, while recognizing that the fuel-use exemption is no longer 
available for additional steamships.

J. Locomotives (40 CFR Part 1033)

    EPA's emission standards and certification requirements for 
locomotives and locomotive engines are in 40 CFR part 1033. This final 
rule includes several amendments that affect locomotives, as discussed 
in Sections XI.A and XI.L.
    In addition, we are amending 40 CFR 1033.815 to clarify how penalty 
provisions apply relative to maintenance and remanufacturing 
requirements. We have become aware that the discussion of violations 
and penalties in 40 CFR 1033.815(f) addresses failure to perform 
required maintenance but omits reference to the recordkeeping 
requirements described in that same regulatory section. We originally 
adopted the maintenance and recordkeeping requirements with a statement 
describing that failing to meet these requirements would be considered 
a violation of the tampering prohibition in 40 CFR 1068.101(b)(1). The 
requirement for owners to keep records for the specified maintenance 
are similarly tied to the tampering prohibition, but failing to keep 
required records cannot be characterized as a tampering violation per 
se. As a result, we are amending 40 CFR 1033.815(f) to clarify that a 
failure to keep records violates 40 CFR 1068.101(a)(2).
    We are also amending 40 CFR 1033.815(f) to specifically name the 
tampering prohibition as the relevant provision related to maintenance 
requirements for locomotives, rather than making a more general 
reference to prohibitions in 40 CFR 1068.101.
    We are amending 40 CFR 1033.525 to remove the smokemeter 
requirements and replace them with a reference to 40 CFR 1065.1125, 
which will serve as the central location for all instrument and setup 
requirements for measuring smoke. We are also adding data analysis 
requirements for locomotives to 40 CFR 1033.525 that were never 
migrated over from 40 CFR 92.131; manufacturers still use these 
procedures to analyze and submit smoke data for certifying locomotives. 
It is our understanding is that all current smoke testing includes 
computer-based analysis of measured results; we are therefore removing 
the references to manual or graphical analysis of smoke test data.
    Finally, we are amending 40 CFR 1033.1 to clarify that 40 CFR part 
1033 applies to engines that were certified under part 92 before 2008. 
We are also removing 40 CFR 1033.102 and revising 40 CFR 1033.101 and 
appendix A of part 1033 to more carefully describe how locomotives were 
subject to different standards in the transition to the standards 
currently specified in 40 CFR 1033.101.
    We received no comments on these proposed amendments and are 
finalizing the proposed amendments without modification.

K. Stationary Compression-Ignition Engines (40 CFR Part 60, Subpart 
IIII)

    EPA's emission standards and certification requirements for 
stationary compression-ignition engines are in 40 CFR part 60, subpart 
IIII. Section 60.4202 establishes emission standards for stationary 
emergency compression-ignition engines. We are correcting a reference 
in 40 CFR 60.4202 to the Tier 3 standards for marine engines contained 
in 40 CFR part 1042. EPA emission standards for certain engine power 
ratings go directly from Tier 2 to Tier 4. Such engines are never 
subject to Tier 3 standards, so the reference in 40 CFR 60.4202 is 
incorrect. Section 60.4202 currently describes the engines as those 
that otherwise ``would be subject to the Tier 4 standards''. We are 
amending the regulation to more broadly refer to the ``previous tier of 
standards'' instead of naming Tier 3. In most cases, this will continue 
to apply the Tier 3 standards for these engines, but the Tier 2 
standards will apply if the regulation specifies no Tier 3 standard.
    We received no comments on the proposed amendment and are 
finalizing the proposed amendment without modification.

L. Nonroad Compression-Ignition Engines (40 CFR Part 1039)

    EPA's emission standards and certification requirements for nonroad 
compression-ignition engines are in 40 CFR part 1039. We are 
republishing the tables with Tier 1 and Tier 2 standards in appendix I 
of 40 CFR part 1039 to correctly characterize these historical 
standards. The tables codified in the CFR included errors that were 
introduced in the process of publishing those standards (86 FR 34308, 
June 29, 2021).\597\
---------------------------------------------------------------------------

    \597\ Stout, Alan. Memorandum to docket EPA-HQ-OAR-2019-0055. 
``Correction to Tables in 40 CFR part 1039, Appendix I''. June 7, 
2022.
---------------------------------------------------------------------------

XII. Statutory and Executive Order Reviews

    Additional information about these statutes and Executive Orders 
can be found at http://www.epa.gov/laws-regulations/laws-and-executive-orders.

A. Executive Order 12866: Regulatory Planning and Review and Executive 
Order 13563: Improving Regulation and Regulatory Review

    This action is an economically significant regulatory action that 
was submitted to the Office of Management and Budget (OMB) for review. 
Any changes made in response to OMB recommendations have been 
documented in the docket. EPA prepared an analysis of the potential 
costs and benefits associated with this action. This analysis, the 
``Regulatory Impact Analysis--Control of Air Pollution from New Motor 
Vehicles: Heavy-Duty Engine and Vehicle Standards,'' is available in 
the docket. The analyses contained in this document are also summarized 
in Sections V, VI, VII, VIII, IX, and X of this preamble.

B. Paperwork Reduction Act (PRA)

    The information collection activities in this rule have been 
submitted for approval to the Office of Management and Budget (OMB) 
under the PRA. The Information Collection Request (ICR) document that 
EPA prepared has been assigned EPA ICR Number 2621.02. You can find a 
copy of the ICR in the docket for this rule, and it is briefly 
summarized here. The information collection requirements are not 
enforceable until OMB approves them.
    The rule builds on existing certification and compliance 
requirements required under title II of the Clean Air Act (42 U.S.C. 
7521 et seq.). Existing requirements are covered under two ICRs: (1) 
EPA ICR Number 1684.20, OMB Control Number 2060-

[[Page 4466]]

0287, Emissions Certification and Compliance Requirements for Nonroad 
Compression-ignition Engines and On-highway Heavy Duty Engines; and (2) 
EPA ICR Number 1695.14, OMB Control Number 2060-0338, Certification and 
Compliance Requirements for Nonroad Spark-ignition Engines. Therefore, 
this ICR only covers the incremental burden associated with the updated 
regulatory requirements as described in this final rule.
     Respondents/affected entities: The entities potentially 
affected by this action are manufacturers of engines and vehicles in 
the heavy-duty on-highway industries, including alternative fuel 
converters, and secondary vehicle manufacturers. Manufacturers of 
light-duty vehicles, light-duty trucks, marine diesel engines, 
locomotives, and various other types of nonroad engines, vehicles, and 
equipment may be affected to a lesser degree.
     Respondent's obligation to respond: Regulated entities 
must respond to this collection if they wish to sell their products in 
the United States, as prescribed by CAA section 203(a). Participation 
in some programs is voluntary; but once a manufacturer has elected to 
participate, it must submit the required information.
     Estimated number of respondents: Approximately 279 
(total).
     Frequency of response: Annually or on occasion, depending 
on the type of response.
     Total estimated burden: 16,951 hours per year. Burden is 
defined at 5 CFR 1320.03(b).
     Total estimated cost: $3,313,619 (per year), includes an 
estimated $1,685,848 annualized capital or maintenance and operational 
costs.
    An agency may not conduct or sponsor, and a person is not required 
to respond to, a collection of information unless it displays a 
currently valid OMB control number. The OMB control numbers for EPA's 
regulations in title 40 of the Code of Federal Regulations are listed 
in 40 CFR part 9. When OMB approves this ICR, the Agency will announce 
that approval in the Federal Register and amend 40 CFR part 9 as needed 
to display the OMB control number for the approved information 
collection activities contained in this final rule.

C. Regulatory Flexibility Act (RFA)

    I certify that this action will not have a significant economic 
impact on a substantial number of small entities under the RFA. The 
small entities subject to the requirements of this final action are 
heavy-duty alternative fuel engine converters and heavy-duty secondary 
vehicle manufacturers. While this final rule also includes regulatory 
amendments for sectors other than highway heavy-duty engines and 
vehicles, these amendments for other sectors correct, clarify, and 
streamline the regulatory provisions and they will impose no additional 
burden on small entities in these other sectors.
    We identified 251 small entities in the heavy-duty sector that are 
expected to be subject to the final rule: Two heavy-duty alternative 
fuel engine converters and 249 heavy-duty secondary vehicle 
manufacturers. The Agency has determined that 203 of the 251 small 
entities subject to the rule are expected to experience an impact of 
less than 1 percent of annual revenue; 48 small entities are expected 
to experience an impact of 1 to less than 3 percent of annual revenue; 
and no small entity is expected to experience an impact of 3 percent or 
greater of annual revenue. Specifically, the two alternative fuel 
engine converters and 201 secondary vehicle manufacturers are expected 
to experience an impact of less than 1 percent of annual revenue, and 
48 secondary vehicle manufacturers are expected to experience an impact 
of 1 to less than 3 percent of annual revenue. Details of this analysis 
are presented in Chapter 11 of the RIA.

D. Unfunded Mandates Reform Act (UMRA)

    This action contains no unfunded Federal mandate for State, local, 
or Tribal governments as described in UMRA, 2 U.S.C. 1531-1538, and 
does not significantly or uniquely affect small governments. This 
action imposes no enforceable duty on any State, local or Tribal 
government. This action contains Federal mandates under UMRA that may 
result in annual expenditures of $100 million or more for the private 
sector. Accordingly, the costs and benefits associated with this action 
are discussed in Section IX of this preamble and in the RIA, which is 
in the docket for this rule.
    This action is not subject to the requirements of UMRA section 203 
because it contains no regulatory requirements that might significantly 
or uniquely affect small governments.

E. Executive Order 13132: Federalism

    This action does not have Federalism implications. It will not have 
substantial direct effects on states, on the relationship between the 
national government and states, or on the distribution of power and 
responsibilities among the various levels of government.

F. Executive Order 13175: Consultation and Coordination With Indian 
Tribal Governments

    This action does not have Tribal implications as specified in 
Executive Order 13175. This action does not have substantial direct 
effects on one or more Indian tribes, on the relationship between the 
Federal Government and Indian tribes, or on the distribution of power 
and responsibilities between the Federal Government and Indian tribes. 
Thus, Executive Order 13175 does not apply to this action.

G. Executive Order 13045: Protection of Children From Environmental 
Health and Safety Risks

    This action is subject to Executive Order 13045 because it is an 
economically significant regulatory action as defined by Executive 
Order 12866, and EPA believes that the environmental health risks or 
safety risks addressed by this action may have a disproportionate 
effect on children. The 2021 Policy on Children's Health also applies 
to this action. Accordingly, we have evaluated the environmental health 
or safety effects of air pollutants affected by this program on 
children. The results of this evaluation are described in Section II 
regarding the Need for Additional Emissions Control and associated 
references in Section II. The protection offered by these standards may 
be especially important for children because childhood represents a 
life stage associated with increased susceptibility to air pollutant-
related health effects.
    Children make up a substantial fraction of the U.S. population, and 
often have unique factors that contribute to their increased risk of 
experiencing a health effect from exposures to ambient air pollutants 
because of their continuous growth and development. Children are more 
susceptible than adults to many air pollutants because they have (1) a 
developing respiratory system, (2) increased ventilation rates relative 
to body mass compared with adults, (3) an increased proportion of oral 
breathing, particularly in boys, relative to adults, and (4) behaviors 
that increase chances for exposure. Even before birth, the developing 
fetus may be exposed to air pollutants through the mother that affect 
development and permanently harm the individual when the mother is 
exposed.
    Certain motor vehicle emissions present greater risks to children 
as well. Early lifestages (e.g., children) are thought to be more 
susceptible to tumor development than adults when exposed to 
carcinogenic chemicals that act

[[Page 4467]]

through a mutagenic mode of action.\598\ Exposure at a young age to 
these carcinogens could lead to a higher risk of developing cancer 
later in life. Section II.B.7 describes a systematic review and meta-
analysis conducted by the U.S. Centers for Disease Control and 
Prevention that reported a positive association between proximity to 
traffic and the risk of leukemia in children.
---------------------------------------------------------------------------

    \598\ U.S. Environmental Protection Agency (2005). Supplemental 
guidance for assessing susceptibility from early-life exposure to 
carcinogens. Washington, DC: Risk Assessment Forum. EPA/630/R-03/
003F. https://www3.epa.gov/airtoxics/childrens_supplement_final.pdf.
---------------------------------------------------------------------------

    The adverse effects of individual air pollutants may be more severe 
for children, particularly the youngest age groups, than adults. As 
described in Section II.B, the Integrated Science Assessments for a 
number of pollutants affected by this rule, including those for 
NO2, PM, ozone and CO, describe children as a group with 
greater susceptibility. Section II.B.7 discusses a number of childhood 
health outcomes associated with proximity to roadways, including 
evidence for exacerbation of asthma symptoms and suggestive evidence 
for new onset asthma.
    There is substantial evidence that people who live or attend school 
near major roadways are more likely to be people of color, Hispanic 
ethnicity, and/or low SES. Within these highly exposed groups, 
children's exposure and susceptibility to health effects is greater 
than adults due to school-related and seasonal activities, behavior, 
and physiological factors.
    Section VI.B of this preamble presents the estimated emission 
reductions from this final rule, including substantial reductions in 
NOX and other criteria and toxic pollutants. Section VII of 
this preamble presents the air quality impacts of this final rule. The 
air quality modeling predicts decreases in ambient concentrations of 
air pollutants in 2045 due to these standards, including significant 
improvements in ozone concentrations. Ambient PM2.5, 
NO2 and CO concentrations are also predicted to improve in 
2045 because of this program. We also expect this rule's emission 
reductions to reduce air pollution in close proximity to major 
roadways.
    Children are not expected to experience greater ambient 
concentrations of air pollutants than the general population. However, 
because of their greater susceptibility to air pollution and their 
increased time spent outdoors, it is likely that these standards will 
have particular benefits for children's health.

H. Executive Order 13211: Actions Concerning Regulations That 
Significantly Affect Energy Supply, Distribution, or Use

    This action is not a ``significant energy action'' because it is 
not likely to have a significant adverse effect on the supply, 
distribution, or use of energy. In fact, this final rule will have an 
incremental positive impact on energy supply and use. Section III.E and 
Section V describe our projected fuel savings due to new refueling 
emissions standards for certain Spark-ignition heavy-duty vehicles. 
These refueling emission standards require manufacturers to implement 
emission control systems to trap vented fuel instead of releasing it 
into the ambient air during a refueling event. Considering the 
estimated incremental fuel savings from the new refueling emission 
standards, we have concluded that this rule is not likely to have any 
adverse energy effects.

I. National Technology Transfer and Advancement Act (NTTAA) and 1 CFR 
Part 51

    This action involves technical standards. Except for the standards 
discussed in this section, the standards included in the regulatory 
text as incorporated by reference were all previously approved for IBR 
and no change is included in this action.
    In accordance with the requirements of 1 CFR 51.5, we are 
incorporating by reference the use of test methods and standards from 
ASTM International (ASTM). The referenced standards and test methods 
may be obtained through the ASTM website (www.astm.org) or by calling 
(610) 832-9585. We are incorporating by reference the following ASTM 
standards:

------------------------------------------------------------------------
    Standard or test method         Regulation            Summary
------------------------------------------------------------------------
ASTM D975-22, Standard          40 CFR             Fuel specification
 Specification for Diesel        1036.415(c) and    needed for
 Fuel.''.                        1036.810(a).       manufacturer-run
                                                    field-testing
                                                    program. This is a
                                                    newly referenced
                                                    standard.
ASTM D3588-98 (Reapproved       40 CFR             Test method describes
 2017)e1, Standard Practice      1036.550(b) and    how to measure mass-
 for Calculating Heat Value,     1036.810(a).       specific net energy
 Compressibility Factor, and                        content and related
 Relative Density of Gaseous                        parameters of
 Fuels.                                             gaseous fuels.
ASTM D4809-18, Standard Test    40 CFR             Test method describes
 Method for Heat of Combustion   1036.550(b) and    how to determine the
 of Liquid Hydrocarbon Fuels     1036.810(a).       heat of combustion
 by Bomb Calorimeter                                of liquid
 (Precision Method).                                hydrocarbon fuels.
                                                    This reference test
                                                    method replaces an
                                                    earlier version.
ASTM D4814-21c, Standard        40 CFR             Fuel specification
 Specification for Automotive    1036.415(c) and    needed for
 Spark-Ignition Engine Fuel.     1036.810(a).       manufacturer-run
                                                    field-testing
                                                    program. This is a
                                                    newly referenced
                                                    standard.
ASTM D7467-20a, Standard        40 CFR             Fuel specification
 Specification for Diesel Fuel   1036.415(c) and    needed for
 Oil, Biodiesel Blend (B6 to     1036.810(a).       manufacturer-run
 B20).                                              field-testing
                                                    program. This is a
                                                    newly referenced
                                                    standard.
------------------------------------------------------------------------

    In accordance with the requirements of 1 CFR 51.5, we are 
incorporating by reference the use of test methods and standards from 
SAE International. The referenced standards and test methods may be 
obtained through the SAE International website (www.sae.org) or by 
calling (800) 854-7179. We are incorporating by reference the following 
SAE International standards and test methods:

------------------------------------------------------------------------
    Standard or test method         Regulation            Summary
------------------------------------------------------------------------
SAE J1634, July 2017, Battery   40 CFR             The procedure
 Electric Vehicle Energy         600.011(c),        describes how to
 Consumption and Range Test      600.116-12(a),     measure energy
 Procedure.                      600.210-12(d),     consumption and
                                 and 600.311-       range from electric
                                 12(j) and (k).     vehicles. This is an
                                 40 CFR             updated version of
                                 1066.501(a) and    the document
                                 1066.1010(b).      currently specified
                                                    in the regulation.
SAE J1711, June 2010,           40 CFR             The recommended
 Recommended Practice for        1066.501(a),       practice describes
 Measuring the Exhaust           1066.1001, and     how to measure fuel
 Emissions and Fuel Economy of   1066.1010(b).      economy and
 Hybrid-Electric Vehicles,                          emissions from light-
 Including Plug-In Hybrid                           duty vehicles,
 Vehicles.                                          including hybrid-
                                                    electric vehicles.
                                                    This final rule
                                                    cites the reference
                                                    document in an
                                                    additional place in
                                                    the regulation.

[[Page 4468]]

 
SAE J1979-2, April 22, 2021, E/ 40 CFR             The standard includes
 E Diagnostic Test Modes:        1036.150(v) and    information
 OBDonUDS.                       1036.810(c).       describing interface
                                                    protocols for
                                                    onboard diagnostic
                                                    systems. This is a
                                                    newly referenced
                                                    standard.
SAE J2263, May 2020, Road Load  40 CFR 1037.528    The procedure
 Measurement Using Onboard       introductory       describes how to
 Anemometry and Coastdown        text, (a), (b),    perform coastdown
 Techniques.                     (d), and (f),      measurements with
                                 1037.665(a), and   light-duty and heavy-
                                 1037.810(e). 40    duty vehicles. This
                                 CFR 1066.301(b),   is an updated
                                 1066.305,          version of the
                                 1066.310(b),       document currently
                                 1066.1010(b).      specified in the
                                                    regulation. We are
                                                    keeping the
                                                    reference to the
                                                    older version of the
                                                    same procedure to
                                                    allow for continued
                                                    testing with that
                                                    procedure through
                                                    model year 2025.
SAE J2711, May 2020,            40 CFR             The recommended
 Recommended Practice for        1066.501(a),       practice describes
 Measuring Fuel Economy and      1066.1001, and     how to measure fuel
 Emissions of Hybrid-Electric    1066.1010(b).      economy and
 and Conventional Heavy-Duty                        emissions from heavy-
 Vehicles.                                          duty vehicles,
                                                    including hybrid-
                                                    electric vehicles.
                                                    This is an updated
                                                    version of the
                                                    document currently
                                                    specified in the
                                                    regulation.
SAE J2841, March 2009, Utility  40 CFR             The standard practice
 Factor Definitions for Plug-    1037.550(a) and    establishes
 In Hybrid Electric Vehicles     1037.810(e).       terminology and
 Using 2001 U.S. DOT National                       procedures for
 Household Travel Survey Data.                      calculating emission
                                                    rates and fuel
                                                    consumption for plug-
                                                    in hybrid electric
                                                    vehicles.
------------------------------------------------------------------------

    In accordance with the requirements of 1 CFR 51.5, we are 
incorporating by reference the use of test methods and standards from 
the California Air Resources Board (CARB), published by the State of 
California in the California Code of Regulations (CCR). The referenced 
standards and test methods may be obtained through the CARB website 
(www.arb.ca.gov) or by calling (916) 322-2884. We are incorporating by 
reference the following CARB documents:

------------------------------------------------------------------------
    Standard or test method         Regulation            Summary
------------------------------------------------------------------------
2019 13 CCR 1968.2: Title 13.   40 CFR             The CARB standards
 Motor Vehicles, Division 3.     1036.110(b),       establish
 Air Resources Board, Chapter    1036.111(a), and   requirements for
 1. Motor Vehicle Pollution      1036.810(d).       onboard diagnostic
 Control Devices, Article 2.                        systems for heavy-
 Approval of Motor Vehicle                          duty vehicles. These
 Pollution Control Devices                          are newly referenced
 (New Vehicles), Sec.                               standards.
 1968.2. Malfunction and
 Diagnostic System
 Requirements--2004 and
 Subsequent Model-Year
 Passenger Cars, Light-Duty
 Trucks, and Medium-Duty
 Vehicles and Engines.
2019 13 CCR 1968.5: Title 13.   40 CFR             The CARB standards
 Motor Vehicles, Division 3.     1036.110(b) and    establish
 Air Resources Board, Chapter    1036.810(d).       requirements for
 1. Motor Vehicle Pollution                         onboard diagnostic
 Control Devices, Article 2.                        systems for heavy-
 Approval of Motor Vehicle                          duty vehicles. These
 Pollution Control Devices                          are newly referenced
 (New Vehicles), Sec.                               standards.
 1968.5. Enforcement of
 Malfunction and Diagnostic
 System Requirements for 2004
 and Subsequent Model-Year
 Passenger Cars, Light-Duty
 Trucks, and Medium-Duty
 Vehicles and Engines.
2019 13 CCR 1971.1: Title 13.   40 CFR             The CARB standards
 Motor Vehicles, Division 3.     1036.110(b),       establish
 Air Resources Board, Chapter    1036.111(a),       requirements for
 1. Motor Vehicle Pollution      1036.150(v), and   onboard diagnostic
 Control Devices, Article 2.     1036.810(d).       systems for heavy-
 Approval of Motor Vehicle                          duty vehicles. This
 Pollution Control Devices                          is a newly
 (New Vehicles), Sec.                               referenced standard.
 1971.1. On-Board Diagnostic
 System Requirements--2010 and
 Subsequent Model-Year Heavy-
 Duty Engines.
13 CA ADC 1971.5: 2019 CA REG   40 CFR             The California
 TEXT 504962 (NS) California's   1036.110(b) and    standards establish
 2019 heavy-duty OBD             1036.810(d).       requirements for
 requirements, 13 CA ADC                            onboard diagnostic
 1971.5. Enforcement of                             systems for heavy-
 Malfunction and Diagnostic                         duty vehicles. These
 System Requirements for 2010                       are newly referenced
 and Subsequent Model-Year                          standards.
 Heavy-Duty Engines.
------------------------------------------------------------------------

    The following standards are already approved for the reg text in 
which they appear: ASTM D1267; ASTM D1838; ASTM D2163; ASTM D2158; ASTM 
D2598; ASTM D2713; ASTM D5291; ASTM D6667; GEM Phase 2; ISO/IEC 
18004:2006(E); ISO 28580; NIST Special Publication 811; NIST Technical 
Note 1297; SAE J30; SAE J1263; SAE J1527; SAE J2263 DEC2008; SAE J2996.

J. Executive Order 12898: Federal Actions To Address Environmental 
Justice in Minority Populations and Low-Income Populations

    Executive Order 12898 (59 FR 7629, February 16, 1994) directs 
Federal agencies, to the greatest extent practicable and permitted by 
law, to make environmental justice part of their mission by identifying 
and addressing, as appropriate, disproportionately high and adverse 
human health or environmental effects of their programs, policies, and 
activities on minority populations (people of color and/or indigenous 
peoples) and low-income populations.
    The EPA believes that the human health or environmental conditions 
that exist prior to this action result in or have the potential to 
result in disproportionate and adverse human health or environmental 
effects on people of color, low-income populations and/or indigenous 
peoples. EPA provides a summary of the evidence for potentially 
disproportionate and adverse effects among people of color and low-
income populations in Section VII.H of this preamble.
    EPA believes that this action is likely to reduce existing 
disproportionate and adverse effects on people of color, low-income 
populations and/or indigenous peoples. The information supporting this 
Executive Order review is contained in Section VII.H of this preamble 
and Chapter 4.3 and Chapter 6.4.9 of the RIA, and all supporting 
documents have been placed in the public docket for this action.
    Section VII.H of this preamble summarizes evidence that communities 
with environmental justice concerns are disproportionately impacted by 
mobile source emissions and will therefore benefit from the anticipated 
emission reductions. Section VII.H.1 also presents the results of new 
work showing that, relative to the rest of the population, people 
living near truck routes are more likely to be people of color and have 
lower incomes than the general population. EPA's review of populations 
living near truck routes and the study of

[[Page 4469]]

NO2 reductions during the COVID lockdown together provide 
evidence that motor vehicle emission reductions may reduce disparities 
in exposure to traffic-related air pollution.
    With respect to emission reductions and associated improvements in 
air quality, EPA has determined that this rule will benefit all U.S. 
populations, including people of color, low-income populations, and 
indigenous peoples. Section VI of this preamble presents the estimated 
emission reductions, including substantial reductions in NOX 
and other criteria and toxic pollutants. Section VII of this preamble 
presents the projected air quality impacts. Air quality modeling 
predicts that this final rule will decrease ambient concentrations of 
air pollutants in 2045, including significant improvements in ozone 
concentrations. Ambient PM2.5, NO2 and CO 
concentrations are also predicted to decrease in 2045 as a result of 
this final rule. We also expect this rule's emission reductions to 
reduce air pollution in close proximity to major roadways.
    In terms of benefits to human health, reduced ambient 
concentrations of ozone and PM2.5 will reduce many adverse 
environmental and human health impacts in 2045, including reductions in 
premature deaths and many nonfatal illnesses. These health benefits, 
described in Section VIII of this preamble, apply for all U.S. 
populations, including people of color, low-income populations, and 
indigenous peoples.
    EPA conducted a demographic analysis of air quality modeling data 
in 2045 to examine trends in human exposure to future air quality in 
scenarios both with and without this final rule. That analysis, 
summarized in Section VII.H.2 of this preamble and presented in more 
detail in RIA Chapter 6.3.9, supports the conclusion that in the 2045 
baseline, nearly double the number of people of color live within areas 
with the worst ozone and PM2.5 air quality compared to non-
Hispanic whites. We also found that the largest predicted improvements 
in both ozone and PM2.5 are estimated to occur in areas with 
the worst baseline air quality. This final rule will improve air 
quality for people of color; however, disparities in PM2.5 
and ozone exposure are projected to remain.
    EPA additionally identified environmental justice concerns and took 
the following actions to enable meaningful involvement in this 
rulemaking, including: (1) Contacting individuals in environmental 
justice groups to provide information on pre-registration for the 
public hearings for the proposed rule (March 17, 2022); (2) contacting 
individuals in environmental justice groups again when the proposed 
rule was published in the Federal Register (March 28, 2022); (3) 
providing information on our website in both Spanish and English, as 
well as providing Spanish translation during the public hearings for 
the rule; (4) providing additional time to participate in the public 
hearings for the proposed rule, including extending the hearings by one 
day and providing for evening hours; (5) providing an ``Overview of 
EPA's Heavy Duty Vehicle Proposal for EJ Stakeholders'' on April 18, 
2022; (6) posting materials on our website for the proposed rule, 
including a copy of materials used for the overview on April 18, 2022 
and a fact sheet specific to transportation and environmental justice 
with information relevant to the proposed rule and related EPA actions.

K. Congressional Review Act

    This action is subject to the Congressional Review Act, and EPA 
will submit a rule report to each House of the Congress and to the 
Comptroller General of the United States. This action is a ``major 
rule'' as defined by 5 U.S.C. 804(2).

L. Judicial Review

    Under CAA section 307(b)(1), judicial review of this final rule is 
available only by filing a petition for review in the U.S. Court of 
Appeals for the District of Columbia Circuit by March 27, 2023. Under 
CAA section 307(d)(7)(B), only an objection to this final rule that was 
raised with reasonable specificity during the period for public comment 
can be raised during judicial review. CAA section 307(d)(7)(B) also 
provides a mechanism for EPA to convene a proceeding for 
reconsideration, ``[i]f the person raising an objection can demonstrate 
to EPA that it was impracticable to raise such objection within [the 
period for public comment] or if the grounds for such objection arose 
after the period for public comment (but within the time specified for 
judicial review) and if such objection is of central relevance to the 
outcome of the rule.'' Any person seeking to make such a demonstration 
should submit a Petition for Reconsideration to the Office of the 
Administrator, Environmental Protection Agency, Room 3000, William 
Jefferson Clinton Building, 1200 Pennsylvania Ave. NW, Washington, DC 
20460, with an electronic copy to the person listed in FOR FURTHER 
INFORMATION CONTACT, and the Associate General Counsel for the Air and 
Radiation Law Office, Office of General Counsel (Mail Code 2344A), 
Environmental Protection Agency, 1200 Pennsylvania Ave. NW, Washington, 
DC 20004. Note that under CAA section 307(b)(2), the requirements 
established by this final rule may not be challenged separately in any 
civil or criminal proceedings brought by EPA to enforce these 
requirements.

XIII. Statutory Provisions and Legal Authority

    Statutory authority for this rulemaking is in the Clean Air Act (42 
U.S.C. 7401-7671q), including CAA sections 202, 203, 206, 207, 208, 
213, 216, and 301 (42 U.S.C. 7521, 7522, 7525, 7541, 7542, 7547, 7550, 
and 7601); the Energy Policy and Conservation Act (49 U.S.C. 32901-
32919q); and the Act to Prevent Pollution from Ships (33 U.S.C. 1901-
1912).

List of Subjects

40 CFR Part 2

    Administrative practice and procedure, Confidential business 
information, Courts, Environmental protection, Freedom of information, 
Government employees.

40 CFR Part 59

    Air pollution control, Confidential business information, Labeling, 
Ozone, Reporting and recordkeeping requirements, Volatile organic 
compounds.

40 CFR Part 60

    Administrative practice and procedure, Air pollution control, 
Aluminum, Beverages, Carbon monoxide, Chemicals, Coal, Electric power 
plants, Fluoride, Gasoline, Glass and glass products, Grains, 
Greenhouse gases, Household appliances, Industrial facilities, 
Insulation, Intergovernmental relations, Iron, Labeling, Lead, Lime, 
Metals, Motor vehicles, Natural gas, Nitrogen dioxide, Petroleum, 
Phosphate, Plastics materials and synthetics, Polymers, Reporting and 
recordkeeping requirements, Rubber and rubber products, Sewage 
disposal, Steel, Sulfur oxides, Vinyl, Volatile organic compounds, 
Waste treatment and disposal, Zinc.

40 CFR Part 80

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Diesel fuel, Fuel additives, Gasoline, Imports, 
Oil imports, Petroleum, Renewable fuel.

40 CFR Part 85

    Confidential business information, Greenhouse gases, Imports, 
Labeling, Motor vehicle pollution, Reporting and

[[Page 4470]]

recordkeeping requirements, Research, Warranties.

40 CFR Part 86

    Environmental protection, Administrative practice and procedure, 
Confidential business information, Incorporation by reference, 
Labeling, Motor vehicle pollution, Reporting and recordkeeping 
requirements.

40 CFR Part 600

    Environmental protection, Administrative practice and procedure, 
Electric power, Fuel economy, Incorporation by reference, Labeling, 
Reporting and recordkeeping requirements.

40 CFR Part 1027

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Reporting and recordkeeping requirements.

40 CFR Part 1030

    Environmental protection, Air pollution control, Aircraft, 
Greenhouse gases.

40 CFR Part 1031

    Environmental protection, Aircraft, confidential business 
information.

40 CFR Part 1033

    Environmental protection, Administrative practice and procedure, 
Confidential business information, Environmental protection, Labeling, 
Penalties, Railroads, Reporting and recordkeeping requirements.

40 CFR Part 1036

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Greenhouse 
gases, Incorporation by reference, Labeling, Motor vehicle pollution, 
Reporting and recordkeeping requirements, Warranties.

40 CFR Part 1037

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Incorporation 
by reference, Labeling, Motor vehicle pollution, Reporting and 
recordkeeping requirements, Warranties.

40 CFR Part 1039

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Labeling, Penalties, Reporting and recordkeeping requirements, 
Warranties.

40 CFR Part 1042

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Environmental 
protection, Imports, Labeling, Penalties, Reporting and recordkeeping 
requirements, Vessels, Warranties.

40 CFR Part 1043

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Imports, Reporting and recordkeeping 
requirements, Vessels.

40 CFR Part 1045

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Labeling, Penalties, Reporting and recordkeeping requirements, 
Warranties.

40 CFR Part 1048

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Labeling, Penalties, Reporting and recordkeeping requirements, 
Research, Warranties.

40 CFR Parts 1051 and 1054

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Labeling, Penalties, Reporting and recordkeeping requirements, 
Warranties.

40 CFR Part 1060

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Incorporation by reference, Labeling, Penalties, Reporting and 
recordkeeping requirements, Warranties.

40 CFR Part 1065

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Incorporation by reference, Reporting and 
recordkeeping requirements, Research.

40 CFR Part 1066

    Environmental protection, Air pollution control, Incorporation by 
reference, Reporting and recordkeeping requirements.

40 CFR Part 1068

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Confidential business information, Imports, 
Motor vehicle pollution, Penalties, Reporting and recordkeeping 
requirements, Warranties.

40 CFR Part 1090

    Environmental protection, Administrative practice and procedure, 
Air pollution control, Diesel fuel, Fuel additives, Gasoline, Imports, 
Oil imports, Petroleum, Renewable fuel.

Michael S. Regan,
Administrator.

    For the reasons set out in the preamble, we are amending title 40, 
chapter I of the Code of Federal Regulations as set forth below.

PART 2--PUBLIC INFORMATION

0
1. The authority citation for part 2 continues to read as follows:

    Authority: 5 U.S.C. 552, 552a, 553; 28 U.S.C. 509, 510, 534; 31 
U.S.C. 3717.

0
2. Amend Sec.  2.301 by adding and reserving paragraph (i) and adding 
paragraph (j) to read as follows:

Sec.  2.301  Special rules governing certain information obtained under 
the Clean Air Act.

* * * * *
    (j) Requests for or release of information subject to a 
confidentiality determination through rulemaking as specified in 40 CFR 
part 1068. This paragraph (j) describes provisions that apply for a 
wide range of engines, vehicles, and equipment that are subject to 
emission standards and other requirements under the Clean Air Act. This 
includes motor vehicles and motor vehicle engines, nonroad engines and 
nonroad equipment, aircraft and aircraft engines, and stationary 
engines. It also includes portable fuel containers regulated under 40 
CFR part 59, subpart F, and fuel tanks, fuel lines, and related fuel-
system components regulated under 40 CFR part 1060. Regulatory 
provisions related to confidentiality determinations for these products 
are codified broadly in 40 CFR part 1068, with additional detailed 
provisions for specific sectors in the regulatory parts referenced in 
40 CFR 1068.1. References in this paragraph (j) to 40 CFR part 1068 
also include these related regulatory parts.
    (1) Unless noted otherwise, 40 CFR 2.201 through 2.215 do not apply 
for information covered by the confidentiality determinations in 40 CFR 
part 1068 if EPA has determined through rulemaking that information to 
be any of the following pursuant to 42 U.S.C. 7414 or 7542(c) in a 
rulemaking subject to 42 U.S.C. 7607(d):
    (i) Emission data as defined in paragraph (a)(2)(i) of this 
section.

[[Page 4471]]

    (ii) Data not entitled to confidential treatment.
    (2) Unless noted otherwise, Sec. Sec.  2.201 through 2.208 do not 
apply for information covered by the confidentiality determinations in 
40 CFR part 1068 if EPA has determined through rulemaking that 
information to be entitled to confidential treatment pursuant to 42 
U.S.C. 7414 or 7542(c) in a rulemaking subject to 42 U.S.C. 7607(d). 
EPA will treat such information as confidential in accordance with the 
provisions of Sec. Sec.  2.209 through 2.215, subject to paragraph 
(j)(4) of this section.
    (3) EPA will deny a request for information under 5 U.S.C. 
552(b)(4) if EPA has determined through rulemaking that the information 
is entitled to confidential treatment under 40 CFR part 1068. The 
denial notification will include a regulatory cite to the appropriate 
determination.
    (4) A determination made pursuant to 42 U.S.C. 7414 or 7542 in a 
rulemaking subject to 42 U.S.C. 7607(d) that information specified in 
40 CFR part 1068 is entitled to confidential treatment shall continue 
in effect unless EPA takes one of the following actions to modify the 
determination:
    (i) EPA determines, pursuant to 5 U.S.C. 552(b)(4) and the Clean 
Air Act (42 U.S.C. 7414; 7542(c)) in a rulemaking subject to 42 U.S.C. 
7607(d), that the information is entitled to confidential treatment, or 
that the information is emission data or data that is otherwise not 
entitled to confidential treatment by statute or regulation.
    (ii) EPA determines, pursuant to 5 U.S.C. 552(b)(4) and the Clean 
Air Act (42 U.S.C. 7414; 7542(c)) that the information is emission data 
or data that is otherwise clearly not entitled to confidential 
treatment by statute or regulation under 40 CFR 2.204(d)(2).
    (iii) The Office of General Counsel revisits an earlier 
determination, pursuant to 5 U.S.C. 552(b)(4) and the Clean Air Act (42 
U.S.C. 7414; 7542(c)), that the information is entitled to confidential 
treatment because of a change in the applicable law or newly discovered 
or changed facts. Prior to a revised final determination, EPA shall 
afford the business an opportunity to submit a substantiation on the 
pertinent issues to be considered, including any described in 
Sec. Sec.  2.204(e)(4) or 2.205(b), within 15 days of the receipt of 
the notice to substantiate. If, after consideration of any timely 
comments made by the business in its substantiation, the Office of 
General Counsel makes a revised final determination that the 
information is not entitled to confidential treatment under 42 U.S.C. 
7414 or 7542, EPA will notify the business in accordance with Sec.  
2.205(f)(2).
    (5) The provisions of 40 CFR 2.201 through 2.208 continue to apply 
for the categories of information identified in 40 CFR 1068.11(c) for 
which there is no confidentiality determination in 40 CFR part 1068.

PART 59--NATIONAL VOLATILE ORGANIC COMPOUND EMISSION STANDARDS FOR 
CONSUMER AND COMMERCIAL PRODUCTS

0
3. The authority citation for part 59 continues to read as follows:

    Authority: 42 U.S.C. 7414 and 7511b(e).

0
4. Revise Sec.  59.695 to read as follows:

Sec.  59.695  What provisions apply to confidential information?

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

PART 60--STANDARDS OF PERFORMANCE FOR NEW STATIONARY SOURCES

0
5. The authority citation for part 60 continues to read as follows:

    Authority: 42 U.S.C. 7401 et seq.

0
6. Amend Sec.  60.4202 by revising paragraph (g) introductory text to 
read as follows:

Sec.  60.4202  What emission standards must I meet for emergency 
engines if I am a stationary CI internal combustion engine 
manufacturer?

* * * * *
    (g) Notwithstanding the requirements in paragraphs (a) through (d) 
of this section, stationary emergency CI ICE identified in paragraphs 
(a) and (c) of this section may be certified to the provisions of 40 
CFR part 1042 for commercial engines that are applicable for the 
engine's model year, displacement, power density, and maximum engine 
power if the engines will be used solely in either or both of the 
locations identified in paragraphs (g)(1) and (2) of this section. 
Engines that would be subject to the Tier 4 standards in 40 CFR part 
1042 that are used solely in either or both of the locations identified 
in paragraphs (g)(1) and (2) of this section may instead continue to be 
certified to the previous tier of standards in 40 CFR part 1042. The 
previous tier is Tier 3 in most cases; however, the previous tier is 
Tier 2 if there are no Tier 3 standards specified for engines of a 
certain size or power rating.
* * * * *

0
7. Revise Sec.  60.4218 to read as follows:

Sec.  60.4218  What General Provisions and confidential information 
provisions apply to me?

    (a) Table 8 to this subpart shows which parts of the General 
Provisions in Sec. Sec.  60.1 through 60.19 apply to you.
    (b) The provisions of 40 CFR 1068.10 and 1068.11 apply for engine 
manufacturers. For others, the general confidential business 
information (CBI) provisions apply as described in 40 CFR part 2.

0
8. Revise Sec.  60.4246 to read as follows:

Sec.  60.4246  What General Provisions and confidential information 
provisions apply to me?

    (a) Table 3 to this subpart shows which parts of the General 
Provisions in Sec. Sec.  60.1 through 60.19 apply to you.
    (b) The provisions of 40 CFR 1068.10 and 1068.11 apply for engine 
manufacturers. For others, the general confidential business 
information (CBI) provisions apply as described in 40 CFR part 2.

PART 80--REGULATION OF FUELS AND FUEL ADDITIVES

0
9. The authority citation for part 80 continues to read as follows:

    Authority: 42 U.S.C. 7414, 7521, 7542, 7545, and 7601(a).

Subpart B [Removed and reserved]

0
10. Remove and reserve subpart B.

PART 85--CONTROL OF AIR POLLUTION FROM MOBILE SOURCES

0
11. The authority citation for part 85 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
12. Amend Sec.  85.1501 by revising paragraph (a) to read as follows:

Sec.  85.1501  Applicability.

    (a) Except where otherwise indicated, this subpart is applicable to 
motor vehicles offered for importation or imported into the United 
States for which the Administrator has promulgated regulations under 40 
CFR part 86, subpart D or S, prescribing emission standards, but which 
are not covered by certificates of conformity issued under section 
206(a) of the Clean Air Act (i.e., which are nonconforming vehicles as 
defined in Sec.  85.1502), as amended, and part 86 at the time of 
conditional importation. Compliance with regulations under this subpart 
shall not relieve any person or entity from compliance with other 
applicable provisions of the Clean Air Act. This subpart no longer 
applies for heavy-duty engines certified under 40 CFR part 86,

[[Page 4472]]

subpart A, or 40 CFR part 1036; references in this subpart to 
``engines'' therefore apply only for replacement engines intended for 
installation in motor vehicles that are subject to this subpart.
* * * * *

Sec.  85.1513  [Amended]

0
13. Amend Sec.  85.1513 by removing and reserving paragraph (e)(5).

0
14. Revise Sec.  85.1514 to read as follows:

Sec.  85.1514  Treatment of confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this subpart.

0
15. Amend Sec.  85.1515 by revising paragraph (a)(2)(ii)(A) to read as 
follows:

Sec.  85.1515  Emission standards and test procedures applicable to 
imported nonconforming motor vehicles and motor vehicle engines.

    (a) * * *
    (2) * * *
    (ii) * * *
    (A) Exhaust and fuel economy tests. You must measure emissions over 
the FTP driving cycle and the highway fuel economy driving cycle as 
specified in 40 CFR 1066.801 to meet the fuel economy requirements in 
40 CFR part 600 and demonstrate compliance with the exhaust emission 
standards in 40 CFR part 86 (other than PM). Measure exhaust emissions 
and fuel economy with the same test procedures used by the original 
manufacturer to test the vehicle for certification. However, you must 
use an electric dynamometer meeting the requirements of 40 CFR part 
1066, subpart B, unless we approve a different dynamometer based on 
excessive compliance costs. If you certify based on testing with a 
different dynamometer, you must state in the application for 
certification that all vehicles in the emission family will comply with 
emission standards if tested on an electric dynamometer.
* * * * *

0
16. Amend Sec.  85.1701 by revising paragraphs (a)(1), (b), and (c) to 
read as follows:

Sec.  85.1701  General applicability.

    (a) * * *
    (1) Beginning January 1, 2014, the exemption provisions of 40 CFR 
part 1068, subpart C, apply instead of the provisions of this subpart 
for heavy-duty motor vehicle engines and heavy-duty motor vehicles 
regulated under 40 CFR part 86, subpart A, 40 CFR part 1036, or 40 CFR 
part 1037, except that the nonroad competition exemption of 40 CFR 
1068.235 and the nonroad hardship exemption provisions of 40 CFR 
1068.245, 1068.250, and 1068.255 do not apply for motor vehicle 
engines. Note that the provisions for emergency vehicle field 
modifications in Sec.  85.1716 continue to apply for heavy-duty 
engines.
* * * * *
    (b) The provisions of 40 CFR 1068.10 and 1068.11 apply for 
information you submit under this subpart.
    (c) References to engine families and emission control systems in 
this subpart or in 40 CFR part 1068 apply to durability groups and test 
groups as applicable for manufacturers certifying vehicles under the 
provisions of 40 CFR part 86, subpart S.
* * * * *

Sec.  85.1712  [Removed and Reserved]

0
17. Remove and reserve Sec.  85.1712.

0
18. Revise Sec.  85.1808 to read as follows:

Sec.  85.1808  Treatment of confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this subpart.

0
19. Amend Sec.  85.1901 by revising paragraph (a) to read as follows:

Sec.  85.1901  Applicability.

    (a) The requirements of this subpart shall be applicable to all 
1972 and later model year motor vehicles and motor vehicle engines, 
except that the provisions of 40 CFR 1068.501 apply instead for heavy-
duty motor vehicle engines and heavy-duty motor vehicles certified 
under 40 CFR part 86, subpart A, or 40 CFR part 1036 or 1037 starting 
January 1, 2018.
* * * * *

0
20. Revise Sec.  85.1909 to read as follows:

Sec.  85.1909  Treatment of confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this subpart.

0
21. Revise the heading of subpart V to read as follows:

Subpart V--Warranty Regulations and Voluntary Aftermarket Part 
Certification Program

0
22. Amend Sec.  85.2102 by revising paragraphs (a)(1), (2), (4) through 
(6), (10), and (13) to read as follows:

Sec.  85.2102  Definitions.

    (a) * * *
    (1) Act means Part A of Title II of the Clean Air Act, 42 U.S.C. 
7421 et seq.
    (2) Office Director means the Director for the Office of 
Transportation and Air Quality in the Office of Air and Radiation of 
the Environmental Protection Agency or other authorized representative 
of the Office Director.
* * * * *
    (4) Emission performance warranty means that warranty given 
pursuant to this subpart and 42 U.S.C. 7541(b).
    (5) Emission warranty means a warranty given pursuant to this 
subpart and 42 U.S.C. 7541(a) or (b).
    (6) Model year means the manufacturer's annual production period as 
described in subpart X of this part.
* * * * *
    (10) Useful life means that period established pursuant to 42 
U.S.C. 7521(d) and regulations promulgated thereunder.
* * * * *
    (13) Written instructions for proper maintenance and use means 
those maintenance and operation instructions specified in the owner's 
manual as being necessary to assure compliance of a vehicle with 
applicable emission standards for the useful life of the vehicle that 
are:
    (i) In accordance with the instructions specified for performance 
on the manufacturer's prototype vehicle used in certification 
(including those specified for vehicles used under special 
circumstances); and
    (ii) In compliance with the requirements of 40 CFR 86.1808; and
    (iii) In compliance with any other EPA regulations governing 
maintenance and use instructions.
* * * * *

0
23. Amend Sec.  85.2103 by revising paragraph (a)(3) to read as 
follows:

Sec.  85.2103  Emission performance warranty.

    (a) * * *
    (3) Such nonconformity results or will result in the vehicle owner 
having to bear any penalty or other sanction (including the denial of 
the right to use the vehicle) under local, State or Federal law, then 
the manufacturer shall remedy the nonconformity at no cost to the 
owner; except that, if the vehicle has been in operation for more than 
24 months or 24,000 miles, the manufacturer shall be required to remedy 
only those nonconformities resulting from the failure of any of the 
specified major emission control components listed in 42 U.S.C. 
7541(i)(2) or components which have been designated by the 
Administrator under 42 U.S.C. 7541(i)(2) to be specified major emission 
control

[[Page 4473]]

components until the vehicle has been in operation for 8 years or 
80,000 miles.
* * * * *

0
24. Amend Sec.  85.2104 by revising paragraphs (a) and (h) introductory 
text to read as follows:

Sec.  85.2104  Owners' compliance with instructions for proper 
maintenance and use.

    (a) An emission warranty claim may be denied on the basis of 
noncompliance by a vehicle owner with the written instructions for 
proper maintenance and use.
* * * * *
    (h) In no case may a manufacturer deny an emission warranty claim 
on the basis of--
* * * * *

0
25. Amend Sec.  85.2106 by revising paragraphs (b) introductory text, 
(c), (d) introductory text, (d)(2), and (g) to read as follows:

Sec.  85.2106  Warranty claim procedures.

* * * * *
    (b) A claim under any emission warranty required by 42 U.S.C. 
7541(a) or (b) may be submitted by bringing a vehicle to:
* * * * *
    (c) To the extent required by any Federal or State law, whether 
statutory or common law, a vehicle manufacturer shall be required to 
provide a means for non-franchised repair facilities to perform 
emission warranty repairs.
    (d) The manufacturer of each vehicle to which the warranty is 
applicable shall establish procedures as to the manner in which a claim 
under the emission warranty is to be processed. The procedures shall--
* * * * *
    (2) Require that if the facility at which the vehicle is initially 
presented for repair is unable for any reason to honor the particular 
claim, then, unless this requirement is waived in writing by the 
vehicle owner, the repair facility shall forward the claim to an 
individual or office authorized to make emission warranty 
determinations for the manufacturer.
* * * * *
    (g) The vehicle manufacturer shall incur all costs associated with 
a determination that an emission warranty claim is valid.

0
26. Amend Sec.  85.2107 by revising paragraphs (a) and (b) to read as 
follows:

Sec.  85.2107  Warranty remedy.

    (a) The manufacturer's obligation under the emission warranties 
provided under 42 U.S.C. 7541(a) and (b) shall be to make all 
adjustments, repairs or replacements necessary to assure that the 
vehicle complies with applicable emission standards of the U.S. 
Environmental Protection Agency, that it will continue to comply for 
the remainder of its useful life (if proper maintenance and operation 
are continued), and that it will operate in a safe manner. The 
manufacturer shall bear all costs incurred as a result of the above 
obligation, except that after the first 24 months or 24,000 miles 
(whichever first occurs) the manufacturer shall be responsible only 
for:
    (1) The adjustment, repair or replacement of any of the specified 
major emission control components listed in 42 U.S.C. 7541(i)(2) or 
components which have been designated by the administrator to be 
specified major emission control components until the vehicle has been 
in operation for 8 years or 80,000 miles; and
    (2) All other components which must be adjusted, repaired or 
replaced to enable a component adjusted, repaired, or replaced under 
paragraph (a)(1) of this section to perform properly.
    (b) Manufacturers shall be liable for the total cost of the remedy 
for any vehicle validly presented for repair under an emission warranty 
to any authorized service facility authorized by the vehicle 
manufacturer. State or local limitations as to the extent of the 
penalty or sanction imposed upon an owner of a failed vehicle shall 
have no bearing on this liability.
* * * * *

0
27. Amend Sec.  85.2109 by revising paragraphs (a) introductory text 
and (a)(6) to read as follows:

Sec.  85.2109  Inclusion of warranty provisions in owners' manuals and 
warranty booklets.

    (a) A manufacturer shall furnish with each new motor vehicle, a 
full explanation of the emission warranties required by 42 U.S.C. 
7541(a) and (b), including at a minimum the following information:
* * * * *
    (6) An explanation that an owner may obtain further information 
concerning the emission warranties or that an owner may report 
violations of the terms of the emission warranties provided under 42 
U.S.C. 7541(a) and (b) by contacting the Director, Compliance Division, 
Environmental Protection Agency, 2000 Traverwood Dr, Ann Arbor, MI 
48105 (Attention: Warranty) or email to: [email protected].
* * * * *

0
28. Amend Sec.  85.2111 by revising the introductory text and 
paragraphs (b) introductory text, (c), and (d) to read as follows:

Sec.  85.2111  Warranty enforcement.

    The following acts are prohibited and may subject a manufacturer to 
a civil penalty as described in paragraph (d) of this section:
* * * * *
    (b) Failing or refusing to comply with the terms and conditions of 
the emission warranties provided under 42 U.S.C. 7541(a) and (b) with 
respect to any vehicle to which this subpart applies. Acts constituting 
such a failure or refusal shall include, but are not limited to, the 
following:
* * * * *
    (c) To provide directly or indirectly in any communication to the 
ultimate purchaser or any subsequent purchaser that emission warranty 
coverage is conditioned upon the use of any name brand component, or 
system or upon service (other than a component or service provided 
without charge under the terms of the purchase agreement), unless the 
communication is made pursuant to a written waiver by the Office 
Director.
    (d) The maximum penalty value is $37,500 for each offense that 
occurs after November 2, 2015. Maximum penalty limits may be adjusted 
based on the Consumer Price Index as described at 40 CFR part 19.
* * * * *

0
29. Revise Sec.  85.2123 to read as follows:

Sec.  85.2123  Treatment of confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this subpart.

0
30. Revise the heading for subpart W to read as follows:

Subpart W--Emission Control System Performance Warranty Tests

PART 86--CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES 
AND ENGINES

0
31. The authority citation for part 86 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
32. Amend Sec.  86.007-11 by revising paragraphs (f) and (g) 
introductory text to read as follows:

Sec.  86.007-11  Emission standards and supplemental requirements for 
2007 and later model year diesel heavy-duty engines and vehicles.

* * * * *

[[Page 4474]]

    (f) Model year 2007 and later diesel-fueled heavy-duty engines and 
vehicles for sale in Guam, American Samoa, or the Commonwealth of the 
Northern Mariana Islands may be subject to alternative standards under 
40 CFR 1036.655.
    (g) Model years 2018 through 2026 engines at or above 56 kW that 
will be installed in specialty vehicles as allowed by 40 CFR 1037.605 
may meet alternate emission standards as follows:
* * * * *

0
33. Amend Sec.  86.008-10 by revising paragraph (g) introductory text 
to read as follows:

Sec.  86.008-10  Emission standards for 2008 and later model year Otto-
cycle heavy-duty engines and vehicles.

* * * * *
    (g) Model years 2018 through 2026 engines that will be installed in 
specialty vehicles as allowed by 40 CFR 1037.605 may meet alternate 
emission standards as follows:
* * * * *

0
34. Amend Sec.  86.010-18 by:
0
a. Revising paragraph (a) introductory text.
0
b. Removing and reserving paragraph (o)
    The revision reads as follows:

Sec.  86.010-18  On-board Diagnostics for engines used in applications 
greater than 14,000 pounds GVWR.

    (a) General. Heavy-duty engines intended for use in a heavy-duty 
vehicle weighing more than 14,000 pounds GVWR must be equipped with an 
on-board diagnostic (OBD) system capable of monitoring all emission-
related engine systems or components during the life of the engine. The 
OBD requirements of 40 CFR 1036.110 apply starting in model year 2027. 
In earlier model years, manufacturers may meet the requirements of this 
section or the requirements of 40 CFR 1036.110. Note that 40 CFR 
1036.150(v) allows for an alternative communication protocol before 
model year 2027. The OBD system is required to detect all malfunctions 
specified in paragraphs (g), (h), and (i) of this section even though 
the OBD system is not required to use a unique monitor to detect each 
of those malfunctions.
* * * * *

0
35. Amend Sec.  86.016-1 by:
0
a. Revising paragraphs (a) introductory text, (d) introductory text, 
and (d)(4).
0
b. Adding and reserving paragraph (i) adding paragraph (j).
    The revisions and additions read as follows:

Sec.  86.016-1  General applicability.

    (a) Applicability. The provisions of this subpart apply for certain 
types of new heavy-duty engines and vehicles as described in this 
section. As described in paragraph (j) of this section, most of this 
subpart no longer applies starting with model year 2027. Note that this 
subpart does not apply for light-duty vehicles, light-duty trucks, 
medium-duty passenger vehicles, or vehicles at or below 14,000 pounds 
GVWR that have no propulsion engine, such as electric vehicles; see 
subpart S of this part for requirements that apply for those vehicles. 
In some cases, manufacturers of heavy-duty engines and vehicles can 
choose to meet the requirements of this subpart or the requirements of 
subpart S of this part; those provisions are therefore considered 
optional, but only to the extent that manufacturers comply with the 
other set of requirements. In cases where a provision applies only for 
a certain vehicle group based on its model year, vehicle class, motor 
fuel, engine type, or other distinguishing characteristics, the limited 
applicability is cited in the appropriate section. The provisions of 
this subpart apply for certain heavy-duty engines and vehicles as 
follows:
* * * * *
    (d) Non-petroleum fueled vehicles. Standards and requirements apply 
to model year 2016 and later non-petroleum fueled motor vehicles as 
follows:
* * * * *
    (4) The standards and requirements of 40 CFR part 1037 apply for 
vehicles above 14,000 pounds GVWR that have no propulsion engine, such 
as electric vehicles. Electric heavy-duty vehicles may not generate PM 
emission credits. Electric heavy-duty vehicles may not generate 
NOX emission credits except as allowed under 40 CFR part 
1037.
* * * * *
    (j) Transition to 40 CFR parts 1036 and 1037. Except for Sec.  
86.010-38(j), this subpart no longer applies starting with model year 
2027. Individual provisions in 40 CFR parts 1036 and 1037 apply instead 
of the provisions of this subpart before model year 2027 as specified 
in this subpart and 40 CFR parts 1036 and 1037.

0
36. Amend Sec.  86.090-5 by adding paragraph (b)(4) to read as follows.

Sec.  86.090-5  General standards; increase in emissions; unsafe 
conditions.

* * * * *
    (b) * * *
    (4) Manufacturers of engines equipped with vanadium-based SCR 
catalysts must design the engine and its emission controls to prevent 
vanadium sublimation and protect the catalyst from high temperatures as 
described in 40 CFR 1036.115(g)(2).

0
37. Amend Sec.  86.117-96 by revising paragraphs (d)(1) to read as 
follows.

Sec.  86.117-96  Evaporative emission enclosure calibrations.

* * * * *
    (d) * * *
    (1) The calculation of net methanol and hydrocarbon mass change is 
used to determine enclosure background and leak rate. It is also used 
to check the enclosure volume measurements. The methanol mass change is 
calculated from the initial and final methanol samples, the net 
withdrawn methanol (in the case of diurnal emission testing with fixed-
volume enclosures), and initial and final temperature according to the 
following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.004

Where:

MCH3OH = Methanol mass change, [mu]g.
Vn = Enclosure volume, in ft\3\, as measured in paragraph 
(b)(1) of this section.
TE = Temperature of sample withdrawn, R.
f = Final sample.
CMS = GC concentration of test sample.
1 = First impinger.
AV = Volume of absorbing reagent in impinger (ml).
2 = Second impinger.

[[Page 4475]]

VE = Volume of sample withdrawn, ft3. Sample 
volumes must be corrected for differences in temperature to be 
consistent with determination of Vn, prior to being used 
in the equation.
TSHED = Temperature of SHED, R.
i = Initial sample.
MCH3OH,out = mass of methanol exiting the enclosure, in 
the case of fixed volume enclosures for diurnal emission testing, 
[mu]g.
MCH3OH,in = mass of methanol exiting the enclosure, in 
the case of fixed volume enclosures for diurnal emission testing, 
[mu]g.
* * * * *

0
38. Amend Sec.  86.137-94 by revising paragraph (b)(24) to read as 
follows.

Sec.  86.137-94  Dynamometer test run, gaseous and particulate 
emissions.

* * * * *
    (b) * * *
    (24) This completes the test sequence for vehicles that do not need 
testing for evaporative emissions. Continue testing for evaporative 
emissions as follows:
    (i) For the three-day diurnal test sequence, proceed according to 
Sec.  86.134.
    (ii) For the two-day diurnal test sequence, proceed according to 
Sec.  86.138-96(k). The following additional provisions apply for 
heavy-duty vehicles:
    (A) For vehicles with a nominal fuel tank capacity at or above 50 
gallons, operate the vehicle over a second full FTP cycle before 
measuring evaporative emissions; exhaust emission measurement is not 
required for the additional FTP cycle.
    (B) [Reserved]

0
39. Amend Sec.  86.143-96 by revising paragraph (b)(1)(i) to read as 
follows.

Sec.  86.143-96  Calculations; evaporative emissions.

* * * * *
    (b) * * *
    (1) * * *
    (i) Methanol emissions:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.005
    
Where:

MCH3OH = Methanol mass change, [mu]g.
Vn = Net enclosure volume, ft3, as determined 
by subtracting 50 ft3 (volume of vehicle with trunk and 
windows open) from the enclosure volume. A manufacturer may use the 
measured volume of the vehicle (instead of the nominal 50 
ft3) with advance approval by the Administrator: 
Provided, the measured volume is determined and used for all 
vehicles tested by that manufacturer.
TE = Temperature of sample withdrawn, R.
f = Final sample.
CMS = GC concentration of sample, [mu]g/ml.
1 = First impinger.
AV = Volume of absorbing reagent in impinger.
2 = Second impinger.
VE = Volume of sample withdrawn, ft3. Sample 
volumes must be corrected for differences in temperature to be 
consistent with determination of Vn, prior to being used 
in the equation.
TSHED = Temperature of SHED, R.
i = Initial sample.
MCH3OH,out = mass of methanol exiting the enclosure, in 
the case of fixed-volume enclosures for diurnal emission testing, 
[mu]g.
MCH3OH,in = mass of methanol entering the enclosure, in 
the case of fixed-volume enclosures for diurnal emission testing, 
[mu]g.
* * * * *

0
40. Amend Sec.  86.154-98 by revising paragraph (e)(9) to read as 
follows.

Sec.  86.154-98  Measurement procedure; refueling test.

* * * * *
    (e) * * *
    (9) For vehicles equipped with more than one fuel tank, use good 
engineering judgment to apply the procedures described in this section 
for each fuel tank.

0
41. Add Sec.  86.450 to subpart E to read as follows:

Sec.  86.450  Treatment of confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this subpart.

Subpart I [Removed and Reserved]

0
42. Subpart I, consisting of Sec. Sec.  86.1101-87 through 86.1116-87, 
is removed and reserved.

0
43. Add Sec.  86.1117 to subpart L to read as follows:

Sec.  86.1117  Labeling.

    (a) Light-duty trucks and heavy-duty vehicles and engines for which 
nonconformance penalties are to be paid in accordance with Sec.  
86.1113-87(b) must have information printed on the emission control 
information label or a supplemental label as follows.
    (1) The manufacturer must begin labeling production engines or 
vehicles within 10 days after the completion of the PCA.
    (2) This statement shall read: ``The manufacturer of this [engine 
or vehicle, as applicable] will pay a nonconformance penalty to be 
allowed to introduce it into U.S. commerce at an emission level higher 
than the applicable emission standard. The [compliance level or 
alternative emission standard] for this engine/vehicle is [insert the 
applicable pollutant and compliance level calculated in accordance with 
Sec.  86.1112-87(a)].''
    (3) If a manufacturer introduces an engine or vehicle into U.S. 
commerce prior to the compliance level determination of Sec.  86.1112-
87(a), it must provide the engine or vehicle owner with a label as 
described in paragraph (a)(2) of this section to be affixed in a 
location in proximity to the emission control information label within 
30 days of the completion of the PCA.
    (b) The Administrator may approve in advance other label content 
and formats, provided the alternative label contains information 
consistent with this section.

0
44. Revise Sec.  86.1301 to read as follows:

Sec.  86.1301  Scope; applicability.

    (a) This subpart specifies gaseous emission test procedures for 
Otto-cycle and diesel heavy-duty engines, and particulate emission test 
procedures for diesel heavy-duty engines.
    (b) You may optionally demonstrate compliance with the emission 
standards of this part by testing hybrid engines and hybrid powertrains 
using the test procedures in 40 CFR part 1036, rather than testing the 
engine alone. If you choose this option, you may meet the supplemental 
emission test (SET) requirements by using the SET duty cycle specified 
in either Sec.  86.1362 or 40 CFR 1036.510. Except as specified, 
provisions of this subpart and subpart A of this part that reference 
engines apply equally to hybrid engines and hybrid powertrains.

[[Page 4476]]

    (c) The abbreviations and acronyms from subpart A of this part 
apply to this subpart.

Sec. Sec.  86.1302-84, 86.1303-84, and 86.1304  [Removed]

0
45. Remove Sec. Sec.  86.1302-84, 86.1303-84, and 86.1304.

0
46. Amend Sec.  86.1362 by revising paragraph (b) to read as follows:

Sec.  86.1362  Steady-state testing with a ramped-modal cycle.

* * * * *
    (b) Measure emissions by testing the engine on a dynamometer with 
the following ramped-modal duty cycle to determine whether it meets the 
applicable steady-state emission standards in this part and 40 CFR part 
1036:
BILLING CODE 6560-50-P

[[Page 4477]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.006

[[Page 4478]]

BILLING CODE 6560-50-C

0
47. Amend Sec.  86.1372 by revising paragraph (a) introductory text to 
read as follows:

Sec.  86.1372  Measuring smoke emissions within the NTE zone.

* * * * *
    (a) For steady-state or transient smoke testing using full-flow 
opacimeters, use equipment meeting the requirements of 40 CFR part 
1065, subpart L.
* * * * *

0
48. Amend Sec.  86.1801-12 by revising paragraphs (a) introductory 
text, (a)(2)(iii), (a)(3) introductory text, (a)(3)(iii) and (iv), (b), 
and (g) to read as follows:

Sec.  86.1801-12  Applicability.

    (a) Applicability. The provisions of this subpart apply to certain 
types of new vehicles as described in this paragraph (a). Where the 
provisions apply for a type of vehicle, they apply for vehicles powered 
by any fuel, unless otherwise specified. In cases where a provision 
applies only to a certain vehicle group based on its model year, 
vehicle class, motor fuel, engine type, or other distinguishing 
characteristics, the limited applicability is cited in the appropriate 
section. Testing references in this subpart generally apply to Tier 2 
and older vehicles, while testing references to 40 CFR part 1066 
generally apply to Tier 3 and newer vehicles; see Sec.  86.101 for 
detailed provisions related to this transition. The provisions of this 
subpart apply to certain vehicles as follows:
* * * * *
    (2) * * *
    (iii) The provisions of this subpart are optional for diesel-fueled 
Class 3 heavy-duty vehicles in a given model year if those vehicles are 
equipped with engines certified to the appropriate standards in Sec.  
86.007-11 or 40 CFR 1036.104 for which less than half of the engine 
family's sales for the model year in the United States are for complete 
Class 3 heavy-duty vehicles. This includes engines sold to all vehicle 
manufacturers. If you are the original manufacturer of the engine and 
the vehicle, base this showing on your sales information. If you 
manufacture the vehicle but are not the original manufacturer of the 
engine, you must use your best estimate of the original manufacturer's 
sales information.
    (3) The provisions of this subpart generally do not apply to 
incomplete heavy-duty vehicles of any size, or to complete vehicles 
above 14,000 pounds GVWR (see Sec.  86.016-1 and 40 CFR parts 1036 and 
1037). However, this subpart applies to such vehicles in the following 
cases:
* * * * *
    (iii) The evaporative emission standards apply for incomplete 
heavy-duty vehicles at or below 14,000 pounds GVWR.
    (iv) Evaporative and refueling emission standards apply for 
complete and incomplete heavy-duty vehicles above 14,000 pounds GVWR as 
specified in 40 CFR 1037.103.
* * * * *
    (b) Relationship to 40 CFR parts 1036 and 1037. If any heavy-duty 
vehicle is not subject to standards and certification requirements 
under this subpart, the vehicle and its installed engine are instead 
subject to standards and certification requirements under 40 CFR parts 
1036 and 1037, as applicable. If you optionally certify engines or 
vehicles to standards under 40 CFR part 1036 or 40 CFR part 1037, 
respectively, those engines or vehicles are subject to all the 
regulatory requirements in 40 CFR parts 1036 and 1037 as if they were 
mandatory. Note that heavy-duty engines subject to greenhouse gas 
standards under 40 CFR part 1036 before model year 2027 are also 
subject to standards and certification requirements under 40 CFR part 
86, subpart A.
* * * * *
    (g) Complete and incomplete vehicles. Several provisions in this 
subpart, including the applicability provisions described in this 
section, are different for complete and incomplete vehicles. We 
differentiate these vehicle types as described in 40 CFR 1037.801.
* * * * *

0
49. Amend Sec.  86.1806-17 by adding paragraphs (a)(9) and (b)(4) to 
read as follows:

Sec.  86.1806-17  Onboard diagnostics.

* * * * *
    (a) * * *
    (9) Apply thresholds as specified in 40 CFR 1036.110(b)(5) for 
engines certified to emission standards under 40 CFR part 1036.
    (b) * * *
    (4) For vehicles with installed compression-ignition engines that 
are subject to standards and related requirements under 40 CFR 1036.104 
and 1036.111, you must comply with the following additional 
requirements:
    (i) Make parameters related to engine derating and other 
inducements available for reading with a generic scan tool as specified 
in 40 CFR 110(b)(9)(vi).
    (ii) Design your vehicles to display information 1036.related to 
engine derating and other inducements in the cab as specified in 40 CFR 
1036.110(c)(1).
* * * * *

0
50. Amend Sec.  86.1810-17 by adding paragraphs (j) and (k) to read as 
follows:

Sec.  86.1810-17  General requirements.

* * * * *
    (j) Small-volume manufacturers that modify a vehicle already 
certified by a different company may recertify that vehicle under this 
subpart S based on the vehicle supplier's compliance with fleet average 
standards for criteria exhaust emissions, evaporative emissions, and 
greenhouse gas emissions as follows:
    (1) The recertifying manufacturer must certify the vehicle at bin 
levels and family emission limits that are the same as or more 
stringent than the corresponding bin levels and family emission limits 
for the vehicle supplier.
    (2) The recertifying manufacturer must meet all the standards and 
requirements described in this subpart S, except for the fleet average 
standards for criteria exhaust emissions, evaporative emissions, and 
greenhouse gas emissions.
    (3) The vehicle supplier must send the small-volume manufacturer a 
written statement accepting responsibility to include the subject 
vehicles in the vehicle supplier's exhaust and evaporative fleet 
average calculations in Sec. Sec.  86.1860-17, 86.1864-10, and 86.1865-
12.
    (4) The small-volume manufacturer must describe in the application 
for certification how the two companies are working together to 
demonstrate compliance for the subject vehicles. The application must 
include the statement from the vehicle supplier described in paragraph 
(j)(3) of this section.
    (5) The vehicle supplier must include a statement that the vehicle 
supplier is including the small volume manufacturer's sales volume and 
emissions levels in the vehicle supplier's fleet average reports under 
Sec. Sec.  86.1860-17, 86.1864-10, and 86.1865-12.
    (k) Gasoline-fueled vehicles must have a restriction in the tank 
filler inlet that allows inserting nozzles meeting the specifications 
of 40 CFR 1090.1550(a), but not nozzles with an outside diameter 
greater than 2.3 centimeters.

0
51. Amend Sec.  86.1813-17 by revising paragraphs (a)(2)(iii) and (b) 
to read as follows:

Sec.  86.1813-17  Evaporative and refueling emission standards.

* * * * *
    (a) * * *

[[Page 4479]]

    (2) * * *
    (iii) Hydrocarbon emissions must not exceed 0.020 g for LDV and LDT 
and 0.030 g for HDV when tested using the Bleed Emission Test Procedure 
adopted by the California Air Resources Board as part of the LEV III 
program. This procedure quantifies diurnal emissions using the two-
diurnal test sequence without measuring hot soak emissions. For heavy-
duty vehicles with a nominal fuel tank capacity at or above 50 gallons, 
operate the vehicle over a second full FTP cycle before measuring 
diurnal emissions. The standards in this paragraph (a)(2)(iii) do not 
apply for testing at high-altitude conditions. For vehicles with non-
integrated refueling canisters, the bleed emission test and standard do 
not apply to the refueling canister. You may perform the Bleed Emission 
Test Procedure using the analogous test temperatures and the E10 test 
fuel specified in subpart B of this part.
* * * * *
    (b) Refueling emissions. Light-duty vehicles, light-duty trucks, 
and heavy-duty vehicles must meet the refueling emission standards in 
this paragraph (b) as follows when measured over the procedure 
specified in Sec.  86.150:
    (1) The following implementation dates apply for incomplete 
vehicles:
    (i) Refueling standards apply starting with model year 2027 for 
incomplete vehicles certified under 40 CFR part 1037, unless the 
manufacturer complies with the alternate phase-in specified in 
paragraph (b)(1)(iii) of this section. If you do not meet the 
alternative phase-in requirement for model year 2026, you must certify 
all your incomplete heavy-duty vehicles above 14,000 pounds GVWR to the 
refueling standard in model year 2027.
    (ii) Refueling standards are optional for incomplete heavy-duty 
vehicles at or below 14,000 pounds GVWR, unless the manufacturer uses 
the alternate phase-in specified in paragraph (b)(1)(iii) of this 
section to meet standards together for heavy-duty vehicles above and 
below 14,000 pounds GVWR.
    (iii) Manufacturers may comply with an alternate phase-in of the 
refueling standard for incomplete heavy-duty vehicles as described in 
this paragraph (b)(1)(iii). Manufacturers must meet the refueling 
standard during the phase-in based on their projected nationwide 
production volume of all incomplete heavy-duty vehicles subject to 
standards under this subpart and under 40 CFR part 1037 as described in 
Table 4 of this section. Keep records as needed to show that you meet 
phase-in requirements.

     Table 4 of Sec.   86.1813-17--Alternative Phase-In Schedule for
     Refueling Emission Standards for Incomplete Heavy-Duty Vehicles
------------------------------------------------------------------------
                                                              Minimum
                                                           percentage of
                                                             vehicles
                       Model year                         subject to the
                                                             refueling
                                                             standard
------------------------------------------------------------------------
2026....................................................              40
2027....................................................              40
2028....................................................              80
2029....................................................              80
2030....................................................             100
------------------------------------------------------------------------

    (2) The following refueling standards apply:
    (i) 0.20 g THCE per gallon of fuel dispensed for vehicles using 
volatile liquid fuels. This standard also applies for diesel-fueled 
LDV.
    (ii) 0.15 g THC per gallon of fuel dispensed for liquefied 
petroleum gas-fueled vehicles and natural gas-fueled vehicles.
* * * * *

Sec.  86.1819  [Removed]

0
52. Remove Sec.  86.1819.

0
53. Amend Sec.  86.1819-14 by revising paragraph (d)(12)(i) to read as 
follows:

Sec.  86.1819-14  Greenhouse gas emission standards for heavy-duty 
vehicles.

* * * * *
    (d) * * *
    (12) * * *
    (i) Configuration means a subclassification within a test group 
based on engine code, transmission type and gear ratios, final drive 
ratio, and other parameters we designate. Engine code means the 
combination of both ``engine code'' and ``basic engine'' as defined for 
light-duty vehicles in 40 CFR 600.002.
* * * * *

0
54. Amend Sec.  86.1821-01 by revising paragraph (a) and adding 
paragraph (g) to read as follows:

Sec.  86.1821-01  Evaporative/refueling family determination.

    (a) The gasoline-, ethanol-, metha- nol-, liquefied petroleum gas-, 
and natural gas-fueled vehicles described in a certification 
application will be divided into groupings expected to have similar 
evaporative and/or refueling emission characteristics (as applicable) 
throughout their useful life. Each group of vehicles with similar 
evaporative and/or refueling emission characteristics shall be defined 
as a separate evaporative/refueling family. Manufacturers shall use 
good engineering judgment to determine evaporative/refueling families. 
This section applies for all sizes and types of vehicles that are 
subject to evaporative or refueling standards, including those subject 
to standards under 40 CFR 1037.103.
* * * * *
    (g) Determine evaporative/refueling families separately for 
vehicles subject to standards under 40 CFR 1037.103 based on the 
criteria in paragraph (b) of this section, even for vehicles you 
certify based on engineering analysis under 40 CFR 1037.103(c). In 
addition, if you certify such vehicles based on testing, include only 
those vehicle models in the family that are properly represented by 
that testing, as described in Sec.  86.1828.

0
55. Amend Sec.  86.1823-08 by:
0
a. Revising paragraph (c)(1)(iv)(A).
0
b. Adding paragraph (m) introductory text.
0
c. Revising paragraph (m)(1).
    The addition and revisions read as follows:

Sec.  86.1823-08  Durability demonstration procedures for exhaust 
emissions.

* * * * *
    (c) * * *
    (1) * * *
    (iv) * * *
    (A) The simulated test weight will be the equivalent test weight 
specified in Sec.  86.129 using a weight basis of the loaded vehicle 
weight for light-duty vehicles and light light-duty trucks, and ALVW 
for all other vehicles.
* * * * *
    (m) Durability demonstration procedures for vehicles subject to the 
greenhouse gas exhaust emission standards specified in Sec.  86.1818. 
Determine a deterioration factor for each exhaust constituent as 
described in this paragraph (m) and in 40 CFR 600.113-12(h) through (m) 
to calculate the composite CREE DF value.
    (1) CO2. (i) Unless otherwise specified under paragraph 
(m)(1)(ii) or (iii) of this section, manufacturers may use a 
multiplicative CO2 deterioration factor of one or an 
additive deterioration factor of zero to determine full useful life 
emissions for the FTP and HFET tests.
    (ii) Based on an analysis of industry-wide data, EPA may 
periodically establish and/or update the deterioration factor for 
CO2 emissions, including air conditioning and other credit-
related emissions. Deterioration factors established and/or updated 
under this paragraph (m)(1)(ii) will provide adequate lead time for 
manufacturers to plan for the change.
    (iii) For plug-in hybrid electric vehicles and any other vehicle 
model

[[Page 4480]]

the manufacturer determines will experience increased CO2 
emissions over the vehicle's useful life, consistent with good 
engineering judgment, manufacturers must either install aged batteries 
and other relevant components on test vehicles as provided in paragraph 
(f)(2) of this section, determine a deterioration factor based on 
testing, or provide an engineering analysis that the vehicle is 
designed such that CO2 emissions will not increase over the 
vehicle's useful life. Manufacturers may test using the whole-vehicle 
mileage accumulation procedures in Sec.  86.1823-08 (c) or (d)(1), or 
manufacturers may request prior EPA approval for an alternative 
durability procedure based on good engineering judgment. For the 
testing option, each FTP test performed on the durability data vehicle 
selected under Sec.  86.1822 must also be accompanied by an HFET test, 
and combined FTP/HFET CO2 results determined by averaging 
the city (FTP) and highway (HFET) CO2 values, weighted 0.55 and 0.45 
respectively. The deterioration factor will be determined for this 
combined CO2 value. Calculated multiplicative deterioration 
factors that are less than one shall be set to equal one, and 
calculated additive deterioration factors that are less than zero shall 
be set to zero.
* * * * *

0
56. Amend Sec.  86.1843-01 by revising paragraph (f)(2) and adding 
paragraph (i) to read as follows:

Sec.  86.1843-01  General information requirements.

* * * * *
    (f) * * *
    (2) The manufacturer must submit a final update to Part 1 and Part 
2 of the Application by May 1 following the end of the model year to 
incorporate any applicable running changes or corrections which 
occurred between January 1 of the applicable model year and the end of 
the model year. A manufacturer may request an extension for submitting 
the final update. The request must clearly indicate the circumstances 
necessitating the extension.
* * * * *
    (i) Confidential information. The provisions of 40 CFR 1068.10 and 
1068.11 apply for information you submit under this subpart.

0
57. Amend Sec.  86.1869-12 by revising paragraph (d)(2)(i) to read as 
follows:

Sec.  86.1869-12  CO2 credits for off-cycle CO2 reducing technologies.

* * * * *
    (d) * * *
    (2) * * *
    (i) The Administrator will publish a notice of availability in the 
Federal Register notifying the public of a manufacturer's proposed 
alternative off-cycle credit calculation methodology. The notice will 
include details regarding the proposed methodology but will not include 
any Confidential Business Information (see 40 CFR 1068.10 and 1068.11). 
The notice will include instructions on how to comment on the 
methodology. The Administrator will take public comments into 
consideration in the final determination and will notify the public of 
the final determination. Credits may not be accrued using an approved 
methodology until the first model year for which the Administrator has 
issued a final approval.
* * * * *

PART 600--FUEL ECONOMY AND GREENHOUSE GAS EXHAUST EMISSIONS OF 
MOTOR VEHICLES

0
58. The authority citation for part 600 continues to read as follows:

    Authority: 49 U.S.C. 32901--23919q, Pub. L. 109-58.

0
59. Amend Sec.  600.001 by removing the paragraph heading from 
paragraph (e) and adding paragraph (f) to read as follows:

Sec.  600.001  General applicability.

* * * * *
    (f) Unless we specify otherwise, send all reports and requests for 
approval to the Designated Compliance Officer (see Sec.  600.002).

0
60. Amend Sec.  600.002 by adding a definition of ``Designated 
Compliance Officer'' in alphabetical order and revising the definitions 
of ``Engine code'', ``SC03'', and ``US06'' to read as follows:

Sec.  600.002  Definitions.

* * * * *
    Designated Compliance Officer means the Director, Light-Duty 
Vehicle Center, U.S. Environmental Protection Agency, 2000 Traverwood 
Drive, Ann Arbor, MI 48105; [email protected]; www.epa.gov/ve-certification.
* * * * *
    Engine code means one of the following:
    (1) For LDV, LDT, and MDPV, engine code means a unique combination, 
within a test group (as defined in Sec.  86.1803 of this chapter), of 
displacement, fuel injection (or carburetion or other fuel delivery 
system), calibration, distributor calibration, choke calibration, 
auxiliary emission control devices, and other engine and emission 
control system components specified by the Administrator. For electric 
vehicles, engine code means a unique combination of manufacturer, 
electric traction motor, motor configuration, motor controller, and 
energy storage device.
    (2) For HDV, engine code has the meaning given in Sec.  86.1819-
14(d)(12) of this chapter.
* * * * *
    SC03 means the test procedure specified in 40 CFR 1066.801(c)(2).
* * * * *
    US06 means the test procedure as described in 40 CFR 
1066.801(c)(2).
* * * * *

0
61. Amend Sec.  600.011 by:
0
a. Adding introductory text;
0
b. Removing paragraph (a);
0
c. Redesignating paragraph (b) as new paragraph (a);
0
d. Adding a new paragraph (b);
0
e. Revising paragraph (c)(2); and
0
f. Removing paragraph (d).
    The additions and revisions read as follows:

Sec.  600.011  Incorporation by reference.

    Certain material is incorporated by reference into this part with 
the approval of the Director of the Federal Register under 5 U.S.C. 
552(a) and 1 CFR part 51. To enforce any edition other than that 
specified in this section, EPA must publish a document in the Federal 
Register and the material must be available to the public. All approved 
incorporation by reference (IBR) material is available for inspection 
at EPA and at the National Archives and Records Administration (NARA). 
Contact EPA at: U.S. EPA, Air and Radiation Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004; 
www.epa.gov/dockets; (202) 202-1744. For information on inspecting this 
material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be 
obtained from the following sources:
* * * * *
    (b) International Organization for Standardization, Case Postale 
56, CH-1211 Geneva 20, Switzerland; (41) 22749 0111; [email protected]; 
or www.iso.org.
    (1) ISO/IEC 18004:2006(E), Information technology--Automatic 
identification and data capture techniques--QR Code 2005 bar code 
symbology specification, Second

[[Page 4481]]

Edition, September 1, 2006, IBR approved for Sec.  600.302-12(b).
    (2) [Reserved]
    (c) * * *
    (2) SAE J1634 JUL2017, Battery Electric Vehicle Energy Consumption 
and Range Test Procedure, Revised July 2017; IBR approved for 
Sec. Sec.  600.116-12(a); 600.210-12(d); 600.311-12(j) and (k).
* * * * *

Subpart B [Amended]

Sec. Sec.  600.106-08, 600.108-08, 600.109-08, and 600.110-
08  [Removed]

0
62. Remove Sec. Sec.  600.106-08, 600.108-08, 600.109-08, and 600.110-
08.

0
63. Amend Sec.  600.111-08 by revising the introductory text to read as 
follows:

Sec.  600.111-08  Test procedures.

    This section describes test procedures for the FTP, highway fuel 
economy test (HFET), US06, SC03, and the cold temperature FTP tests. 
See 40 CFR 1066.801(c) for an overview of these procedures. Perform 
testing according to test procedures and other requirements contained 
in this part 600 and in 40 CFR part 1066. This testing includes 
specifications and procedures for equipment, calibrations, and exhaust 
sampling. Manufacturers may use data collected according to previously 
published test procedures for model years through 2021. In addition, we 
may approve the use of previously published test procedures for later 
model years as an alternative procedure under 40 CFR 1066.10(c). 
Manufacturers must comply with regulatory requirements during the 
transition as described in 40 CFR 86.101 and 86.201.
* * * * *

Sec.  600.112-08  [Removed]

0
64. Remove Sec.  600.112-08.

0
65. Amend Sec.  600.113-12 by revising paragraphs (a)(1), (b) through 
(d), and (e)(1) to read as follows:

Sec.  600.113-12  Fuel economy, CO2 emissions, and carbon-
related exhaust emission calculations for FTP, HFET, US06, SC03 and 
cold temperature FTP tests.

* * * * *
    (a) * * *
    (1) Calculate the weighted grams/mile values for the FTP test for 
CO2, HC, and CO, and where applicable, CH3OH, 
C2H5OH, C2H4O, HCHO, NMHC, 
N2O, and CH4 as specified in 40 CFR 1066.605. 
Measure and record the test fuel's properties as specified in paragraph 
(f) of this section.
* * * * *
    (b) Calculate the HFET fuel economy as follows:
    (1) Calculate the mass values for the highway fuel economy test for 
HC, CO, and CO2, and where applicable, CH3OH, 
C2H5OH, C2H4O, HCHO, NMHC, 
N2O, and CH4 as specified in 40 CFR 1066.605. 
Measure and record the test fuel's properties as specified in paragraph 
(f) of this section.
    (2) Calculate the grams/mile values for the highway fuel economy 
test for HC, CO, and CO2, and where applicable 
CH3OH, C2H5OH, 
C2H4O, HCHO, NMHC, N2O, and 
CH4 by dividing the mass values obtained in paragraph (b)(1) 
of this section, by the actual driving distance, measured in miles, as 
specified in 40 CFR 1066.840.
    (c) Calculate the cold temperature FTP fuel economy as follows:
    (1) Calculate the weighted grams/mile values for the cold 
temperature FTP test for HC, CO, and CO2, and where 
applicable, CH3OH, C2H5OH, 
C2H4O, HCHO, NMHC, N2O, and 
CH4 as specified in 40 CFR 1066.605.
    (2) Calculate separately the grams/mile values for the cold 
transient phase, stabilized phase and hot transient phase of the cold 
temperature FTP test as specified in 40 CFR 1066.605.
    (3) Measure and record the test fuel's properties as specified in 
paragraph (f) of this section.
    (d) Calculate the US06 fuel economy as follows:
    (1) Calculate the total grams/mile values for the US06 test for HC, 
CO, and CO2, and where applicable, CH3OH, 
C2H5OH, C2H4O, HCHO, NMHC, 
N2O, and CH4 as specified in 40 CFR 1066.605.
    (2) Calculate separately the grams/mile values for HC, CO, and 
CO2, and where applicable, CH3OH, 
C2H5OH, C2H4O, HCHO, NMHC, 
N2O, and CH4, for both the US06 City phase and 
the US06 Highway phase of the US06 test as specified in 40 CFR 1066.605 
and 1066.831. In lieu of directly measuring the emissions of the 
separate city and highway phases of the US06 test according to the 
provisions of 40 CFR 1066.831, the manufacturer may optionally, with 
the advance approval of the Administrator and using good engineering 
judgment, analytically determine the grams/mile values for the city and 
highway phases of the US06 test. To analytically determine US06 City 
and US06 Highway phase emission results, the manufacturer shall 
multiply the US06 total grams/mile values determined in paragraph 
(d)(1) of this section by the estimated proportion of fuel use for the 
city and highway phases relative to the total US06 fuel use. The 
manufacturer may estimate the proportion of fuel use for the US06 City 
and US06 Highway phases by using modal CO2, HC, and CO 
emissions data, or by using appropriate OBD data (e.g., fuel flow rate 
in grams of fuel per second), or another method approved by the 
Administrator.
    (3) Measure and record the test fuel's properties as specified in 
paragraph (f) of this section.
    (e) * * *
    (1) Calculate the grams/mile values for the SC03 test for HC, CO, 
and CO2, and where applicable, CH3OH, 
C2H5OH, C2H4O, HCHO, NMHC, 
N2O, and CH4 as specified in 40 CFR 1066.605.
* * * * *

0
66. Amend Sec.  600.115-11 by revising the introductory text to read as 
follows:

Sec.  600.115-11  Criteria for determining the fuel economy label 
calculation method.

    This section provides the criteria to determine if the derived 5-
cycle method for determining fuel economy label values, as specified in 
Sec.  600.210-08(a)(2) or (b)(2) or Sec.  600.210-12(a)(2) or (b)(2), 
as applicable, may be used to determine label values. Separate criteria 
apply to city and highway fuel economy for each test group. The 
provisions of this section are optional. If this option is not chosen, 
or if the criteria provided in this section are not met, fuel economy 
label values must be determined according to the vehicle-specific 5-
cycle method specified in Sec.  600.210-08(a)(1) or (b)(1) or Sec.  
600.210-12(a)(1) or (b)(1), as applicable. However, dedicated 
alternative-fuel vehicles (other than battery electric vehicles and 
fuel cell vehicles), dual fuel vehicles when operating on the 
alternative fuel, MDPVs, and vehicles imported by Independent 
Commercial Importers may use the derived 5-cycle method for determining 
fuel economy label values whether or not the criteria provided in this 
section are met. Manufacturers may alternatively account for this 
effect for battery electric vehicles, fuel cell vehicles, and plug-in 
hybrid electric vehicles (when operating in the charge-depleting mode) 
by multiplying 2-cycle fuel economy values by 0.7 and dividing 2-cycle 
CO2 emission values by 0.7.
* * * * *

0
67. Amend Sec.  600.116-12 by revising paragraph (a) to read as 
follows:

Sec.  600.116-12  Special procedures related to electric vehicles and 
hybrid electric vehicles.

    (a) Determine fuel economy values for electric vehicles as 
specified in Sec. Sec.  600.210 and 600.311 using the procedures of SAE 
J1634 (incorporated by reference in Sec.  600.011). Use the procedures 
of SAE J1634, Section 8, with the following clarifications and

[[Page 4482]]

modifications for using this and other sections of SAE J1634:
    (1) Vehicles that cannot complete the Multi-Cycle Range and Energy 
Consumption Test (MCT) because they are unable travel the distance 
required to complete the test with a fully charged battery, or they are 
unable to achieve the maximum speed on either the UDDS or HFEDS 
(Highway Fuel Economy Drive Cycle also known as the HFET) cycle should 
seek Administrator approval to use the procedures outlined in SAE J1634 
Section 7 Single Cycle Range and Energy Consumption Test (SCT).
    (2) The MCT includes the following key-on soak times and key-off 
soak periods:
    (i) As noted in SAE J1634 Section 8.3.4, a 15 second key-on pause 
is required between UDDS1 and HFEDS1, and 
UDDS3 and HFEDS2.
    (ii) As noted in SAE J1634 Section 8.3.4, a 10-minute key-off soak 
period is required between HFEDS1 and UDDS2, and 
HFEDS2 and UDDS4.
    (iii) A key-off soak period up to 30 minutes may be inserted 
between UDDS2 and the first phase of the mid-test constant 
speed cycle, between UDDS4 and the first phase of the end-
of-test constant speed cycle, and between the end of the mid-test 
constant speed cycle and UDDS3. Start the next test segment 
immediately if there is no key-off soak between test segments.
    (iv) If multiple phases are required during either the mid-test 
constant speed cycle or the end-of-test constant speed cycle there must 
be a 5-minute to 30-minute key-off soak period between each constant 
speed phase as noted in SAE J1634 Section 6.6.
    (3) As noted in SAE J1634 Section 8.3.4, during all `key-off' soak 
periods, the key or power switch must be in the ``off'' position, the 
hood must be closed, the test cell fan(s) must be off, and the brake 
pedal not depressed. For vehicles which do not have a key or power 
switch the vehicle must be placed in the `mode' the manufacturer 
recommends when the vehicle is to be parked and the occupants exit the 
vehicle.
    (4) Manufacturers may determine the mid-test constant speed cycle 
distance (dM) using their own methodology and good 
engineering judgment. Otherwise, either Method 1 or Method 2 described 
in Appendix A of SAE J1634 may be used to estimate the mid-test 
constant speed cycle distance (dM). The mid-test constant 
speed cycle distance calculation needs to be performed prior to 
beginning the test and should not use data from the test being 
performed. If Method 2 is used, multiply the result determined by the 
Method 2 equation by 0.8 to determine the mid-test constant speed cycle 
distance (dM).
    (5) Divide the mid-test constant speed cycle distance 
(dM) by 65 mph to determine the total time required for the 
mid-test constant speed cycle. If the time required is one hour or 
less, the mid-test constant speed cycle can be performed with no key-
off soak periods. If the time required is greater than one hour, the 
mid-test constant speed cycle must be separated into phases such that 
no phase exceeds more than one hour. At the conclusion of each mid-test 
constant speed phase, except at the conclusion of the mid-test constant 
speed cycle, perform a 5-minute to 30-minute key-off soak. A key-off 
soak period up to 30 minutes may be inserted between the end of the 
mid-test constant speed cycle and UDDS3.
    (6) Using good engineering judgment determine the end-of-test 
constant speed cycle distance so that it does not exceed 20% of the 
total distance driven during the MCT as described in SAE J1634 Section 
8.3.3.
    (7) Divide the end-of-test constant speed cycle distance 
(dE) by 65 mph to determine the total time required for the 
end-of-test constant speed cycle. If the time required is one-hour or 
less the end-of-test constant speed cycle can be performed with no key-
off soak periods. If the time required is greater than one-hour the 
end-of-test constant speed cycle must be separated into phases such 
that no phase exceeds more than one-hour. At the conclusion of each 
end-of-test constant speed phase, perform a 5-minute to 30-minute key-
off soak.
    (8) SAE J1634 Section 3.13 defines useable battery energy (UBE) as 
the total DC discharge energy (Edctotal), measured in DC 
watt-hours for a full discharge test. The total DC discharge energy is 
the sum of all measured phases of a test inclusive of all drive cycle 
types. As key-off soak periods are not considered part of the test 
phase, the discharge energy that occurs during the key-off soak periods 
is not included in the useable battery energy.
    (9) Recharging the vehicle's battery must start within three hours 
after the end of testing.
    (10) At the request of a manufacturer, the Administrator may 
approve the use of an earlier version of SAE J1634 when a manufacturer 
is carrying over data for vehicles tested using a prior version of SAE 
J1634.
    (11) All label values related to fuel economy, energy consumption, 
and range must be based on 5-cycle testing or on values adjusted to be 
equivalent to 5-cycle results. Prior to performing testing to generate 
a 5-cycle adjustment factor, manufacturers must request Administrator 
approval to use SAE J1634 Appendices B and C for determining a 5-cycle 
adjustment factor with the following modifications, clarifications, and 
attestations:
    (i) Before model year 2025, prior to performing the 20 [deg]F 
charge-depleting UDDS, the vehicle must soak for a minimum of 12 hours 
and a maximum of 36 hours at a temperature of 20 [deg]F. Prior to 
beginning the 12 to 36 hour cold soak at 20 [deg]F the vehicle must be 
fully charged, the charging can take place at test laboratory ambient 
temperatures (68 to 86 [deg]F) or at 20 [deg]F. During the 12 to 36 
hour cold soak period the vehicle may not be connected to a charger nor 
is the vehicle cabin or battery to be preconditioned during the 20 
[deg]F soak period.
    (ii) Beginning with model year 2025, the 20 [deg]F UDDS charge-
depleting UDDS test will be replaced with a 20 [deg]F UDDS test 
consisting of two UDDS cycles performed with a 10-minute key-off soak 
between the two UDDS cycles. The data from the two UDDS cycles will be 
used to calculate the five-cycle adjustment factor, instead of using 
the results from the entire charge-depleting data set. Manufacturers 
that have submitted and used the average data from 20 [deg]F charge-
depleting UDDS data sets will be required to revise their 5-cycle 
adjustment factor calculation and re-label vehicles using the data from 
the first two UDDS cycles only. Manufacturers, at their discretion, 
would also be allowed to re-run the 20 [deg]F UDDS test with the 
battery charged to a state-of-charge (SoC) determined by the 
manufacturer. The battery does not need to be at 100% SoC before the 20 
[deg]F cold soak.
    (iii) Manufacturers must submit a written attestation to the 
Administrator at the completion of testing with the following 
information:
    (A) A statement noting the SoC level of the rechargeable energy 
storage system (RESS) prior to beginning the 20 [deg]F cold soak for 
testing performed beginning with model year 2025.
    (B) A statement confirming the vehicle was not charged or 
preconditioned during the 12 to 36 hour 20 [deg]F soak period before 
starting the 20 [deg]F UDDS cycle.
    (C) A summary of all the 5-cycle test results and the calculations 
used to generate the 5-cycle adjustment factor, including all the 20 
[deg]F UDDS cycles, the distance travelled during each UDDS and the 
measured DC discharge energy during each UDDS phase. Beginning in model 
year 2025, the 20 [deg]F UDDS test results will consist of only two 
UDDS cycles.

[[Page 4483]]

    (D) Beginning in model year 2025, calculate City Fuel Economy using 
the following equation for RunningFC instead of the equation on Page 30 
in Appendix C of SAE J1634:
[GRAPHIC] [TIFF OMITTED] TR24JA23.007

    (E) A description of each test group and configuration which will 
use the 5-cycle adjustment factor, including the battery capacity of 
the vehicle used to generate the 5-cycle adjustment factor and the 
battery capacity of all the configurations to which it will be applied.
    (iv) At the conclusion of the manufacturers testing and after 
receiving the attestations from the manufacturer regarding the 
performance of the 20 [deg]F UDDS test processes, the 5-cycle test 
results, and the summary of vehicles to which the manufacturer proposes 
applying the 5-cycle adjustment factor, the Administrator will review 
the submittals and inform the manufacturer in writing if the 
Administrator concurs with the manufacturer's proposal. If not, the 
Administrator will describe the rationale to the manufacturer for not 
approving their request.
* * * * *

Subpart C [Amended]

0
68. Amend Sec.  600.210-12 by revising paragraphs (a) introductory 
text, (a)(2)(iii), and (d) to read as follows:

Sec.  600.210-12  Calculation of fuel economy and CO2 emission values 
for labeling.

    (a) General labels. Except as specified in paragraphs (d) and (e) 
of this section, fuel economy and CO2 emissions for general 
labels may be determined by one of two methods. The first is based on 
vehicle-specific model-type 5-cycle data as determined in Sec.  
600.209-12(b). This method is available for all vehicles and is 
required for vehicles that do not qualify for the second method as 
described in Sec.  600.115 (other than electric vehicles). The second 
method, the derived 5-cycle method, determines fuel economy and 
CO2 emissions values from the FTP and HFET tests using 
equations that are derived from vehicle-specific 5-cycle model type 
data, as determined in paragraph (a)(2) of this section. Manufacturers 
may voluntarily lower fuel economy (MPG) values and raise 
CO2 values if they determine that the label values from any 
method are not representative of the in-use fuel economy and 
CO2 emissions for that model type, but only if the 
manufacturer changes both the MPG values and the CO2 value 
and revises any other affected label value accordingly for a model type 
(including but not limited to the fuel economy 1-10 rating, greenhouse 
gas 1-10 rating, annual fuel cost, 5-year fuel cost information). 
Similarly, for any electric vehicles and plug-in hybrid electric 
vehicles, manufacturers may voluntarily lower the fuel economy (MPGe) 
and raise the energy consumption (kW-hr/100 mile) values if they 
determine that the label values are not representative of the in-use 
fuel economy, energy consumption, and CO2 emissions for that 
model type, but only if the manufacturer changes both the MPGe and the 
energy consumption value and revises any other affected label value 
accordingly for a model type. Manufacturers may voluntarily lower the 
value for electric driving range if they determine that the label 
values are not representative of the in-use electric driving range.
* * * * *
    (2) * * *
    (iii) Unless and until superseded by written guidance from the 
Administrator, the following intercepts and slopes shall be used in the 
equations in paragraphs (a)(2)(i) and (ii) of this section:
    City Intercept = 0.004091.
    City Slope = 1.1601.
    Highway Intercept = 0.003191.
    Highway Slope = 1.2945.
* * * * *
    (d) Calculating combined fuel economy, CO2 emissions, 
and driving range. (1) If the criteria in Sec.  600.115-11(a) are met 
for a model type, both the city and highway fuel economy and 
CO2 emissions values must be determined using the vehicle-
specific 5-cycle method. If the criteria in Sec.  600.115-11(b) are met 
for a model type, the city fuel economy and CO2 emissions 
values may be determined using either method, but the highway fuel 
economy and CO2 emissions values must be determined using 
the vehicle-specific 5-cycle method (or modified 5-cycle method as 
allowed under Sec.  600.114-12(b)(2)).
    (2) If the criteria in Sec.  600.115 are not met for a model type, 
the city and highway fuel economy and CO2 emission label 
values must be determined by using the same method, either the derived 
5-cycle or vehicle-specific 5-cycle.
    (3) Manufacturers may use one of the following methods to determine 
5-cycle values for fuel economy, CO2 emissions, and driving 
range for electric vehicles:
    (i) Generate 5-cycle data as described in paragraph (a)(1) of this 
section using the procedures of SAE J1634 (incorporated by reference in 
Sec.  600.011) with amendments and revisions as described in Sec.  
600.116-12(a).
    (ii) Multiply 2-cycle fuel economy values and driving range by 0.7 
and divide 2-cycle CO2 emission values by 0.7.
    (iii) Manufacturers may ask the Administrator to approve adjustment 
factors for deriving 5-cycle fuel economy results from 2-cycle test 
data based on operating data from their in-use vehicles. Such data 
should be collected from multiple vehicles with different drivers over 
a range of representative driving routes and conditions. The 
Administrator may approve such an adjustment factor for any of the 
manufacturer's vehicle models that are properly represented by the 
collected data.
* * * * *

Subpart D [Amended]

0
69. Amend Sec.  600.311-12 by revising paragraphs (j)(2), (j)(4) 
introductory text, and (j)(4)(i) to read as follows:

Sec.  600.311-12  Determination of values for fuel economy labels.

* * * * *
    (j) * * *
    (2) For electric vehicles, determine the vehicle's overall driving 
range as described in Section 8 of SAE J1634 (incorporated by reference 
in Sec.  600.011),

[[Page 4484]]

with amendments and revisions as described in Sec.  600.116. Determine 
separate range values for FTP-based city and HFET-based highway 
driving. Adjust these values to represent 5-cycle values as described 
in Sec.  600.210-12(d)(3), then combine them arithmetically by 
averaging the two values, weighted 0.55 and 0.45, respectively, and 
rounding to the nearest whole number.
* * * * *
    (4) For plug-in hybrid electric vehicles, determine the adjusted 
charge-depleting (Rcda) driving range, the adjusted all electric 
driving range (if applicable), and overall adjusted driving range as 
described in SAE J1711 (incorporated by reference in Sec.  600.011), as 
described in Sec.  600.116, as follows:
    (i) Determine the vehicle's Actual Charge-Depleting Range, 
Rcda, separately for FTP-based city and HFET-based highway 
driving. Adjust these values to represent 5-cycle values as described 
in 600.115-11, then combine them arithmetically by averaging the two 
values, weighted 0.55 and 0.45, respectively, and rounding to the 
nearest whole number. Precondition the vehicle as needed to minimize 
engine operation for consuming stored fuel vapors in evaporative 
canisters; for example, you may purge the evaporative canister or time 
a refueling event to avoid engine starting related to purging the 
canister. For vehicles that use combined power from the battery and the 
engine before the battery is fully discharged, also use this procedure 
to establish an all electric range by determining the distance the 
vehicle drives before the engine starts, rounded to the nearest mile. 
You may represent this as a range of values. We may approve adjustments 
to these procedures if they are necessary to properly characterize a 
vehicle's all electric range.
* * * * *

Subpart F [Amended]

0
70. Amend Sec.  600.510-12 by revising the entry defining the term 
``AFE'' under the formula in paragraph (e) to read as follows:

Sec.  600.510-12  Calculation of average fuel economy and average 
carbon-related exhaust emissions.

* * * * *
    (e) * * *
    AFE = Average combined fuel economy as calculated in paragraph 
(c)(2) of this section, rounded to the nearest 0.0001 mpg;
* * * * *

0
71. Amend Sec.  600.512-12 by adding paragraph (a)(3) and revising 
paragraph (b) to read as follows:

Sec.  600.512-12  Model year report.

    (a) * * *
    (3) Separate reports shall be submitted for passenger automobiles 
and light trucks (as identified in Sec.  600.510-12).
    (b) The model year report shall be in writing, signed by the 
authorized representative of the manufacturer and shall be submitted no 
later than May 1 following the end of the model year. A manufacturer 
may request an extension for submitting the model year report if that 
is needed to provide all additional required data as determined in 
Sec.  600.507-12. The request must clearly indicate the circumstances 
necessitating the extension.
* * * * *

PART 1027--FEES FOR VEHICLE AND ENGINE COMPLIANCE PROGRAMS

0
72. The authority citation for part 1027 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
73. Amend Sec.  1027.101 by revising paragraph (a)(1) to read as 
follows:

Sec.  1027.101  To whom do these requirements apply?

    (a) * * *
    (1) Motor vehicles and motor vehicle engines we regulate under 40 
CFR part 86 or 1036. This includes light-duty vehicles, light-duty 
trucks, medium-duty passenger vehicles, highway motorcycles, and heavy-
duty highway engines and vehicles.
* * * * *

PART 1030--CONTROL OF GREENHOUSE GAS EMISSIONS FROM ENGINES 
INSTALLED ON AIRPLANES

0
74. The authority citation for part 1030 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
75. Revise Sec.  1030.98 to read as follows:

Sec.  1030.98  Confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

PART 1031--CONTROL OF AIR POLLUTION FROM AIRCRAFT ENGINES

0
76. The authority citation for part 1031 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart C [Amended]

0
77. Revise Sec.  1031.170 to read as follows:

Sec.  1031.170  Confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

PART 1033--CONTROL OF EMISSIONS FROM LOCOMOTIVES

0
78. The authority citation for part 1033 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart A [Amended]

0
79. Amend Sec.  1033.1 by revising paragraph (e) to read as follows:

Sec.  1033.1  Applicability.

* * * * *
    (e) This part applies for locomotives that were certified as 
freshly manufactured or remanufactured locomotives under 40 CFR part 
92.

Sec.  1033.5  [Amended]

0
80. Amend Sec.  1033.5 by removing and reserving paragraph (c).

Subpart B [Amended]

0
81. Amend Sec.  1033.101 by revising the introductory text to read as 
follows:

Sec.  1033.101  Exhaust emission standards.

    See appendix A of this part to determine how emission standards 
apply before 2023.
* * * * *

Sec.  1033.102  [Removed]

0
82. Remove Sec.  1033.102.

0
83. Amend Sec.  1033.115 by revising paragraphs (b) introductory text 
and (c) to read as follows:

Sec.  1033.115  Other requirements.

* * * * *
    (b) Adjustable parameters. Locomotives that have adjustable 
parameters must meet all the requirements of this part for any 
adjustment in the approved adjustable range. General provisions for 
adjustable parameters apply as specified in 40 CFR 1068.50. You must 
specify in your application for certification the adjustable range of 
each adjustable parameter on a new locomotive or new locomotive engine 
to--
* * * * *
    (c) Prohibited controls. (1) General provisions. You may not design 
or produce your locomotives with emission control devices, systems, or 
elements of design that cause or

[[Page 4485]]

contribute to an unreasonable risk to public health, welfare, or safety 
while operating. For example, a locomotive may not emit a noxious or 
toxic substance it would otherwise not emit that contributes to such an 
unreasonable risk.
    (2) Vanadium sublimation in SCR catalysts. For engines equipped 
with vanadium-based SCR catalysts, you must design the engine and its 
emission controls to prevent vanadium sublimation and protect the 
catalyst from high temperatures. We will evaluate your engine design 
based on the following information that you must include in your 
application for certification:
    (i) Identify the threshold temperature for vanadium sublimation for 
your specified SCR catalyst formulation as described in 40 CFR 
1065.1113 through 1065.1121.
    (ii) Describe how you designed your engine to prevent catalyst 
inlet temperatures from exceeding the temperature you identify in 
paragraph (c)(2)(i) of this section, including consideration of engine 
wear through the useful life. Also describe your design for catalyst 
protection in case catalyst temperatures exceed the specified 
temperature. In your description, include how you considered elevated 
catalyst temperature resulting from sustained high-load engine 
operation, catalyst exotherms, particulate filter regeneration, and 
component failure resulting in unburned fuel in the exhaust stream.
* * * * *

0
84. Amend Sec.  1033.120 by revising paragraph (c) to read as follows:

Sec.  1033.120  Emission-related warranty requirements.

* * * * *
    (c) Components covered. The emission-related warranty covers all 
components whose failure would increase a locomotive's emissions of any 
regulated pollutant. This includes components listed in 40 CFR part 
1068, appendix A, and components from any other system you develop to 
control emissions. The emission-related warranty covers the components 
you sell even if another company produces the component. Your emission-
related warranty does not need to cover components whose failure would 
not increase a locomotive's emissions of any regulated pollutant. For 
remanufactured locomotives, your emission-related warranty is required 
to cover only those parts that you supply or those parts for which you 
specify allowable part manufacturers. It does not need to cover used 
parts that are not replaced during the remanufacture.
* * * * *

Subpart C [Amended]

0
85. Amend Sec.  1033.205 by revising paragraph (d)(6) to read as 
follows:

Sec.  1033.205  Applying for a certificate of conformity.

* * * * *
    (d) * * *
    (6) A description of injection timing, fuel rate, and all other 
adjustable operating parameters, including production tolerances. For 
any operating parameters that do not qualify as adjustable parameters, 
include a description supporting your conclusion (see 40 CFR 
1068.50(c)). Include the following in your description of each 
adjustable parameter:
    (i) For practically adjustable operating parameters, include the 
nominal or recommended setting, the intended practically adjustable 
range, the limits or stops used to limit adjustable ranges, and 
production tolerances of the limits or stops used to establish each 
practically adjustable range. State that the physical limits, stops or 
other means of limiting adjustment, are effective in preventing 
adjustment of parameters on in-use engines to settings outside your 
intended practically adjustable ranges and provide information to 
support this statement.
    (ii) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustments on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
* * * * *

0
86. Amend Sec.  1033.245 by adding paragraph (f) to read as follows:

Sec.  1033.245  Deterioration factors.

* * * * *
    (f) You may alternatively determine and verify deterioration 
factors based on bench-aged aftertreatment as described in 40 CFR 
1036.245 and 1036.246, with the following exceptions:
    (1) The minimum required aging for locomotive engines as specified 
in 40 CFR 1036.245(c)(2) is 3,000 hours. Operate the engine for service 
accumulation using the same sequence of duty cycles that would apply 
for determining a deterioration factor under paragraphs (a) through (d) 
of this section.
    (2) Perform verification testing as described in subpart F of this 
part rather than 40 CFR 1036.555. The provisions of 40 CFR 
1036.246(d)(2) do not apply. Perform testing consistent with the 
original certification to determine whether tested locomotives meet the 
duty-cycle emission standards in Sec.  1033.101.
    (3) Apply infrequent regeneration adjustment factors as specified 
in Sec.  1033.535 rather than 40 CFR 1036.580.

Subpart F [Amended]

0
87. Revise Sec.  1033.525 to read as follows:

Sec.  1033.525  Smoke opacity testing.

    Analyze exhaust opacity test data as follows:
    (a) Measure exhaust opacity using the procedures specified in 40 
CFR 1065.1125. Perform the opacity test with a continuous digital 
recording of smokemeter response identified by notch setting over the 
entire locomotive test cycle specified in Sec.  1033.515(c)(4) or Sec.  
1033.520(e)(4). Measure smokemeter response in percent opacity to 
within one percent resolution.
    (b) Calibrate the smokemeter as follows:
    (1) Calibrate using neutral density filters with approximately 10, 
20, and 40 percent opacity. Confirm that the opacity values for each of 
these reference filters are NIST-traceable within 185 days of testing, 
or within 370 days of testing if you consistently protect the reference 
filters from light exposure between tests.
    (2) Before each test, remove the smokemeter from the exhaust 
stream, if applicable, and calibrate as follows:
    (i) Zero. Adjust the smokemeter to give a zero response when there 
is no detectable smoke.
    (ii) Linearity. Insert each of the qualified reference filters in 
the light path perpendicular to the axis of the light beam and adjust 
the smokemeter to give a result within 1 percentage point of the named 
value for each reference filter.
    (c) Use computer analysis to evaluate percent opacity for each 
notch setting. Treat the start of the first idle mode as the start of 
the test. Each mode ends when operator demand changes for the next mode 
(or for the end of the test). Analyze the opacity trace using the 
following procedure:
    (1) 3 second peak. Identify the highest opacity value over the test 
and integrate the highest 3 second average including that highest 
value.
    (2) 30 second peak. Divide the test into a series of 30 second 
segments, advancing each segment in 1 second increments. Determine the 
opacity value for each segment and identify the

[[Page 4486]]

highest opacity value from all the 30 second segments.
    (3) Steady-state. Calculate the average of second-by-second values 
between 120 and 180 seconds after the start of each mode. For RMC modes 
that are less than 180 seconds, calculate the average over the last 60 
seconds of the mode. Identify the highest of those steady-state values 
from the different modes.
    (d) Determine values of standardized percent opacity, 
[kappa]std, by correcting to a reference optical path length 
of 1 meter for comparing to the standards using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.008

Where:

[kappa]meas = the value of percent opacity from 
paragraphs (c)(1) through (3) of this section.
lmeas = the smokemeter's optical path length in the 
exhaust plume, expressed to the nearest 0.01 meters.

Example:

[kappa]meas = 14.1%
lmeas = 1.11 m
[GRAPHIC] [TIFF OMITTED] TR24JA23.009

[kappa]std = 12.8%

Subpart G [Amended]

0
88. Amend Sec.  1033.630 by revising paragraph (b)(1) to read as 
follows:

Sec.  1033.630  Staged-assembly and delegated assembly exemptions.

* * * * *
    (b) * * *
    (1) In cases where an engine has been assembled in its certified 
configuration, properly labeled, and will not require an aftertreatment 
device to be attached when installed in the locomotive, no exemption is 
needed to ship the engine. You do not need an exemption to ship engines 
without specific components if they are not emission-related components 
identified in appendix A of 40 CFR part 1068.
* * * * *

0
89. Amend Sec.  1033.815 by revising paragraph (f) to read as follows:

Sec.  1033.815  Maintenance, operation, and repair.

* * * * *
    (f) Failure to perform required maintenance is a violation of the 
tampering prohibition in 40 CFR 1068.101(b)(1). Failure of any person 
to comply with the recordkeeping requirements of this section is a 
violation of 40 CFR 1068.101(a)(2).

Subpart J [Amended]

0
90. Amend Sec.  1033.901 by revising the definitions of ``Adjustable 
parameter'' and ``Designated Compliance Officer'' to read as follows:

Sec.  1033.901  Definitions.

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *
    Designated Compliance Officer means the Director, Diesel Engine 
Compliance Center, U.S. Environmental Protection Agency, 2000 
Traverwood Drive, Ann Arbor, MI 48105; [email protected]; 
www.epa.gov/ve-certification.
* * * * *

0
91. Redesignate appendix I to part 1033 as appendix A to part 1033 and 
revise newly redesignated appendix A to read as follows:

Appendix A to Part 1033--Original Standards for Tier 0, Tier 1 and Tier 
2 Locomotives

    (a) Locomotives were originally subject to Tier 0, Tier 1, and 
Tier 2 emission standards described in paragraph (b) of this 
appendix as follows:
    (1) The Tier 0 and Tier 1 standards in paragraph (b) of this 
appendix applied instead of the Tier 0 and Tier 1 standards of Sec.  
1033.101 for locomotives manufactured and remanufactured before 
January 1, 2010. For example, a locomotive that was originally 
manufactured in 2004 and remanufactured on April 10, 2011, was 
subject to the original Tier 1 standards specified in paragraph (b) 
of this appendix and became subject to the Tier 1 standards of Sec.  
1033.101 when it was remanufactured on April 10, 2011.
    (2) The Tier 2 standards in paragraph (b) of this appendix 
applied instead of the Tier 2 standards of Sec.  1033.101 for 
locomotives manufactured and remanufactured before January 1, 2013.
    (b) The following NOX and PM standards applied before 
the dates specified in paragraph (a) of this appendix:

                          Table 1 to Appendix A--Original Locomotive Emission Standards
----------------------------------------------------------------------------------------------------------------
                                                                               Standards (g/bhp-hr)
                                      Year of                    -----------------------------------------------
        Type of standard             original          Tier                                        PM-alternate
                                    manufacture                         NOX         PM-primary          \a\
----------------------------------------------------------------------------------------------------------------
Line-haul.......................       1973-1992          Tier 0             9.5            0.60            0.30
                                       1993-2004          Tier 1             7.4            0.45            0.22
                                       2005-2011          Tier 2             5.5            0.20            0.10
Switch..........................       1973-1992          Tier 0            14.0            0.72            0.36
                                       1993-2004          Tier 1            11.0            0.54            0.27

[[Page 4487]]

 
                                       2005-2011          Tier 2             8.1            0.24            0.12
----------------------------------------------------------------------------------------------------------------
\a\ Locomotives certified to the alternate PM standards are also subject to alternate CO standards of 10.0 for
  the line-haul cycle and 12.0 for the switch cycle.

    (c) The original Tier 0, Tier 1, and Tier 2 standards for HC and CO 
emissions and smoke are the same standards identified in Sec.  
1033.101.
0
92. Revise part 1036 to read as follows:

PART 1036--CONTROL OF EMISSIONS FROM NEW AND IN-USE HEAVY-DUTY 
HIGHWAY ENGINES

Subpart A--Overview and Applicability
Sec.
1036.1 Applicability.
1036.2 Compliance responsibility.
1036.5 Excluded engines.
1036.10 Organization of this part.
1036.15 Other applicable regulations.
1036.30 Submission of information.
Subpart B--Emission Standards and Related Requirements
1036.101 Overview of exhaust emission standards.
1036.104 Criteria pollutant emission standards--NOX, HC, PM, and CO.
1036.108 Greenhouse gas emission standards--CO2, 
CH4, and N2O.
1036.110 Diagnostic controls.
1036.111 Inducements related to SCR.
1036.115 Other requirements.
1036.120 Emission-related warranty requirements.
1036.125 Maintenance instructions and allowable maintenance.
1036.130 Installation instructions for vehicle manufacturers.
1036.135 Labeling.
1036.136 Clean Idle sticker.
1036.140 Primary intended service class and engine cycle.
1036.150 Interim provisions.
Subpart C--Certifying Engine Families
1036.201 General requirements for obtaining a certificate of 
conformity.
1036.205 Requirements for an application for certification.
1036.210 Preliminary approval before certification.
1036.225 Amending applications for certification.
1036.230 Selecting engine families.
1036.235 Testing requirements for certification.
1036.240 Demonstrating compliance with criteria pollutant emission 
standards.
1036.241 Demonstrating compliance with greenhouse gas emission 
standards.
1036.245 Deterioration factors for exhaust emission standards.
1036.246 Verifying deterioration factors.
1036.250 Reporting and recordkeeping for certification.
1036.255 EPA oversight on certificates of conformity.
Subpart D--Testing Production Engines and Hybrid Powertrains
1036.301 Measurements related to GEM inputs in a selective 
enforcement audit.
Subpart E--In-use Testing
1036.401 Testing requirements for in-use engines.
1036.405 Overview of the manufacturer-run field-testing program.
1036.410 Selecting and screening vehicles and engines for testing.
1036.415 Preparing and testing engines.
1036.420 Pass criteria for individual engines.
1036.425 Pass criteria for engine families.
1036.430 Reporting requirements.
1036.435 Recordkeeping requirements.
1036.440 Warranty obligations related to in-use testing.
Subpart F--Test Procedures
1036.501 General testing provisions.
1036.505 Engine data and information to support vehicle 
certification.
1036.510 Supplemental Emission Test.
1036.512 Federal Test Procedure.
1036.514 Low Load Cycle.
1036.520 Determining power and vehicle speed values for powertrain 
testing.
1036.525 Clean Idle test.
1036.530 Test procedures for off-cycle testing.
1036.535 Determining steady-state engine fuel maps and fuel 
consumption at idle.
1036.540 Determining cycle-average engine fuel maps.
1036.543 Carbon balance error verification.
1036.550 Calculating greenhouse gas emission rates.
1036.555 Test procedures to verify deterioration factors.
1036.580 Infrequently regenerating aftertreatment devices.
Subpart G--Special Compliance Provisions
1036.601 Overview of compliance provisions.
1036.605 Alternate emission standards for engines used in specialty 
vehicles.
1036.610 Off-cycle technology credits and adjustments for reducing 
greenhouse gas emissions.
1036.615 Engines with Rankine cycle waste heat recovery and hybrid 
powertrains.
1036.620 Alternate CO2 standards based on model year 2011 
compression-ignition engines.
1036.625 In-use compliance with CO2 family emission 
limits (FELs).
1036.630 Certification of engine greenhouse gas emissions for 
powertrain testing.
1036.655 Special provisions for diesel-fueled engines sold in 
American Samoa or the Commonwealth of the Northern Mariana Islands.
Subpart H--Averaging, Banking, and Trading for Certification
1036.701 General provisions.
1036.705 Generating and calculating emission credits.
1036.710 Averaging.
1036.715 Banking.
1036.720 Trading.
1036.725 Required information for certification.
1036.730 ABT reports.
1036.735 Recordkeeping.
1036.740 Restrictions for using emission credits.
1036.745 End-of-year CO2 credit deficits.
1036.750 Consequences for noncompliance.
1036.755 Information provided to the Department of Transportation.
Subpart I--Definitions and Other Reference Information
1036.801 Definitions.
1036.805 Symbols, abbreviations, and acronyms.
1036.810 Incorporation by reference.
1036.815 Confidential information.
1036.820 Requesting a hearing.
1036.825 Reporting and recordkeeping requirements.
Appendix A of Part 1036--Summary of Previous Emission Standards
Appendix B of Part 1036--Transient Duty Cycles
Appendix C of Part 1036--Default Engine Fuel Maps for Sec.  1036.540

    Authority: 42 U.S.C. 7401--7671q.

Subpart A--Overview and Applicability

Sec.  1036.1  Applicability.

    (a) Except as specified in Sec.  1036.5, the provisions of this 
part apply for engines that will be installed in heavy-duty vehicles 
(including glider vehicles). Heavy-duty engines produced before 
December 20, 2026 are subject to greenhouse gas emission standards and 
related provisions under this part as specified in Sec.  1036.108; 
these engines are subject to exhaust emission standards for 
NOX, HC, PM, and CO, and related provisions under 40 CFR 
part 86, subpart A and subpart N, instead of this part, except as 
follows:

[[Page 4488]]

    (1) The provisions of Sec. Sec.  1036.115, 1036.501(d), and 
1036.601 apply.
    (2) 40 CFR parts 85 and 86 may specify that certain provisions in 
this part apply.
    (3) This part describes how several individual provisions are 
optional or mandatory before model year 2027. For example, Sec.  
1036.150(a) describes how you may generate emission credits by meeting 
the standards of this part before model year 2027.
    (b) The provisions of this part also apply for fuel conversions of 
all engines described in paragraph (a) of this section as described in 
40 CFR 85.502.
    (c) Gas turbine heavy-duty engines and other heavy-duty engines not 
meeting the definition of compression-ignition or spark-ignition are 
deemed to be compression-ignition engines for purposes of this part.
    (d) For the purpose of applying the provisions of this part, 
engines include all emission-related components and any components or 
systems that should be identified in your application for 
certification, such as hybrid components for engines that are certified 
as hybrid engines or hybrid powertrains.

Sec.  1036.2  Compliance responsibility.

    The regulations in this part contain provisions that affect both 
engine manufacturers and others. However, the requirements of this part 
are generally addressed to the engine manufacturer(s). The term ``you'' 
generally means the engine manufacturer(s), especially for issues 
related to certification. Additional requirements and prohibitions 
apply to other persons as specified in subpart G of this part and 40 
CFR part 1068.

Sec.  1036.5  Excluded engines.

    (a) The provisions of this part do not apply to engines used in 
medium-duty passenger vehicles or other heavy-duty vehicles that are 
subject to regulation under 40 CFR part 86, subpart S, except as 
specified in 40 CFR part 86, subpart S, and Sec.  1036.150(j). For 
example, this exclusion applies for engines used in vehicles certified 
to the standards of 40 CFR 86.1818 and 86.1819.
    (b) An engine installed in a heavy-duty vehicle that is not used to 
propel the vehicle is not a heavy-duty engine. The provisions of this 
part therefore do not apply to these engines. Note that engines used to 
indirectly propel the vehicle (such as electrical generator engines 
that provide power to batteries for propulsion) are subject to this 
part. See 40 CFR part 1039, 1048, or 1054 for other requirements that 
apply for these auxiliary engines. See 40 CFR part 1037 for 
requirements that may apply for vehicles using these engines, such as 
the evaporative and refueling emission requirements of 40 CFR 1037.103.
    (c) The provisions of this part do not apply to aircraft or 
aircraft engines. Standards apply separately to certain aircraft 
engines, as described in 40 CFR part 87.
    (d) The provisions of this part do not apply to engines that are 
not internal combustion engines. For example, the provisions of this 
part generally do not apply to fuel cells. Note that gas turbine 
engines are internal combustion engines.
    (e) The provisions of this part do not apply for model year 2013 
and earlier heavy-duty engines unless they were:
    (1) Voluntarily certified to this part.
    (2) Installed in a glider vehicle subject to 40 CFR part 1037.

Sec.  1036.10  Organization of this part.

    This part is divided into the following subparts:
    (a) Subpart A of this part defines the applicability of this part 
and gives an overview of regulatory requirements.
    (b) Subpart B of this part describes the emission standards and 
other requirements that must be met to certify engines under this part. 
Note that Sec.  1036.150 describes certain interim requirements and 
compliance provisions that apply only for a limited time.
    (c) Subpart C of this part describes how to apply for a certificate 
of conformity.
    (d) Subpart D of this part addresses testing of production engines.
    (e) Subpart E of this part describes provisions for testing in-use 
engines.
    (f) Subpart F of this part describes how to test your engines 
(including references to other parts of the Code of Federal 
Regulations).
    (g) Subpart G of this part describes requirements, prohibitions, 
and other provisions that apply to engine manufacturers, vehicle 
manufacturers, owners, operators, rebuilders, and all others.
    (h) Subpart H of this part describes how you may generate and use 
emission credits to certify your engines.
    (i) Subpart I of this part contains definitions and other reference 
information.

Sec.  1036.15  Other applicable regulations.

    (a) Parts 85 and 86 of this chapter describe additional provisions 
that apply to engines that are subject to this part. See Sec.  
1036.601.
    (b) Part 1037 of this chapter describes requirements for 
controlling evaporative and refueling emissions and greenhouse gas 
emissions from heavy-duty vehicles, whether or not they use engines 
certified under this part.
    (c) Part 1065 of this chapter describes procedures and equipment 
specifications for testing engines to measure exhaust emissions. 
Subpart F of this part describes how to apply the provisions of part 
1065 of this chapter to determine whether engines meet the exhaust 
emission standards in this part.
    (d) The requirements and prohibitions of part 1068 of this chapter 
apply as specified in Sec.  1036.601 to everyone, including anyone who 
manufactures, imports, installs, owns, operates, or rebuilds any of the 
engines subject to this part, or vehicles containing these engines. See 
Sec.  1036.601 to determine how to apply the part 1068 regulations for 
heavy-duty engines. The issues addressed by these provisions include 
these seven areas:
    (1) Prohibited acts and penalties for engine manufacturers, vehicle 
manufacturers, and others.
    (2) Rebuilding and other aftermarket changes.
    (3) Exclusions and exemptions for certain engines.
    (4) Importing engines.
    (5) Selective enforcement audits of your production.
    (6) Recall.
    (7) Procedures for hearings.
    (e) Other parts of this chapter apply if referenced in this part.

Sec.  1036.30  Submission of information.

    Unless we specify otherwise, send all reports and requests for 
approval to the Designated Compliance Officer (see Sec.  1036.801). See 
Sec.  1036.825 for additional reporting and recordkeeping provisions.

Subpart B--Emission Standards and Related Requirements

Sec.  1036.101  Overview of exhaust emission standards.

    (a) You must show that engines meet the following exhaust emission 
standards:
    (1) Criteria pollutant standards for NOX, HC, PM, and CO 
apply as described in Sec.  1036.104.
    (2) Greenhouse gas (GHG) standards for CO2, 
CH4, and N2O apply as described in Sec.  
1036.108.
    (b) You may optionally demonstrate compliance with the emission 
standards of this part by testing hybrid engines and hybrid 
powertrains, rather than testing the engine alone. Except as specified, 
provisions of this part that reference engines apply equally to hybrid 
engines and hybrid powertrains.

[[Page 4489]]

Sec.  1036.104  Criteria pollutant emission standards--NOX, HC, PM, and 
CO.

    This section describes the applicable NOX, HC, CO, and 
PM standards for model years 2027 and later. These standards apply 
equally for all primary intended service classes unless otherwise 
noted.
    (a) Emission standards. Exhaust emissions may not exceed the 
standards in this section, as follows:
    (1) The following emission standards apply for Light HDE, Medium 
HDE, and Heavy HDE over the FTP, SET, and LLC duty cycles using the 
test procedures described in subpart F of this part:

      Table 1 to Paragraph (a)(1) of Sec.   1036.104--Compression-Ignition Standards for Duty Cycle Testing
----------------------------------------------------------------------------------------------------------------
                                                      NOX mg/         HC mg/          PM mg/           CO g/
                   Duty cycle                      hp[middot]hr    hp[middot]hr    hp[middot]hr    hp[middot]hr
----------------------------------------------------------------------------------------------------------------
SET and FTP.....................................              35              60               5             6.0
LLC.............................................              50             140               5             6.0
----------------------------------------------------------------------------------------------------------------

    (2) The following emission standards apply for Spark-ignition HDE 
over the FTP and SET duty cycles using the test procedures described in 
subpart F of this part:

         Table 2 to Paragraph (a)(2) of Sec.   1036.104--Spark-Ignition Standards for Duty Cycle Testing
----------------------------------------------------------------------------------------------------------------
                                                      NOX mg/         HC mg/          PM mg/           CO g/
                   Duty cycle                      hp[middot]hr    hp[middot]hr    hp[middot]hr    hp[middot]hr
----------------------------------------------------------------------------------------------------------------
SET.............................................              35              60               5            14.4
FTP.............................................              35              60               5             6.0
----------------------------------------------------------------------------------------------------------------

    (3) The following off-cycle emission standards apply for Light HDE, 
Medium HDE, and Heavy HDE using the procedures specified in Sec.  
1036.530, as follows:

      Table 3 to Paragraph (a)(3) of Sec.   1036.104--Compression-Ignition Standards for Off-Cycle Testing
----------------------------------------------------------------------------------------------------------------
                                                   Temperature        HC mg/          PM mg/           CO g/
        Off-cycle Bin                 NOX         adjustment \a\   hp[middot]hr    hp[middot]hr    hp[middot]hr
----------------------------------------------------------------------------------------------------------------
Bin 1........................  10.0 g/hr.......  (25.0-Tamb)      ..............  ..............  ..............
                                                  [middot] 0.25.
Bin 2........................  58 mg/            (25.0-Tamb)                 120             7.5               9
                                hp[middot]hr.     [middot] 2.2.
----------------------------------------------------------------------------------------------------------------
\a\ Tamb is the mean ambient temperature over a shift-day, or equivalent. Adjust the off-cycle NOX standard for
  Tamb below 25.0 [deg]C by adding the calculated temperature adjustment to the specified NOX standard. Round
  the temperature adjustment to the same precision as the NOX standard for the appropriate bin. If you declare a
  NOX FEL for the engine family, do not apply the FEL scaling calculation from paragraph (c)(3) of this section
  to the calculated temperature adjustment.

    (b) Clean Idle. You may optionally certify compression-ignition 
engines to the Clean Idle NOX emission standard using the 
Clean Idle test specified in Sec.  1036.525. The optional Clean Idle 
NOX emission standard is 30.0 g/h for model years 2024 
through 2026, and 10.0 g/hr for model year 2027 and later. The standard 
applies separately to each mode of the Clean Idle test. If you certify 
an engine family to the Clean Idle standards, it is subject to all 
these voluntary standards as if they were mandatory.
    (c) Averaging, banking, and trading. You may generate or use 
emission credits under the averaging, banking, and trading (ABT) 
program described in subpart H of this part for demonstrating 
compliance with NOX emission standards in paragraph (a) of 
this section. You must meet the PM, HC, and CO emission standards in 
Sec.  1036.104(a) without generating or using emission credits.
    (1) To generate or use emission credits, you must specify a family 
emission limit for each engine family. Declare the family emission 
limit corresponding to full useful life for engine operation over the 
FTP duty cycle, FELFTP, expressed to the same number of 
decimal places as the emission standard. Use FELFTP to 
calculate emission credits in subpart H of this part.
    (2) The following NOX FEL caps are the maximum value you 
may specify for FELFTP:
    (i) 65 mg/hp[middot]hr for model years 2027 through 2030.
    (ii) 50 mg/hp[middot]hr for model year 2031 and later.
    (iii) 70 mg/hp[middot]hr for model year 2031 and later Heavy HDE.
    (3) Calculate the NOX family emission limit, 
FEL[cycle]NOX, that applies for each duty-cycle or off-cycle 
standard using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.010

Where:

Std[cycle]NOX, = the NOX emission standard 
that applies for the applicable cycle or for off-cycle testing under 
paragraph (a)

[[Page 4490]]

of this section for engines not participating in the ABT program.
FELFTPNOX = the engine family's declared FEL for 
NOX over the FTP duty cycle from paragraph (c)(1) of this 
section.
StdFTPNOX = the NOX emission standard that 
applies for the FTP duty cycle under paragraph (a) of this section 
for engines not participating in the ABT program.

Example for model year 2029 Medium HDE for the SET:

StdSETNOX = 35 mg/hp[middot]hr
    FELFTP = 121 mg/hp[middot]hr
    StdFTPNOX = 35 mg/hp[middot]hr
    [GRAPHIC] [TIFF OMITTED] TR24JA23.011
    
FELSETNOX = 121 mg/hp[middot]hr
    (4) The family emission limits you select under this paragraph (c) 
serve as the emission standards for compliance testing instead of the 
standards specified in this section.
    (d) Fuel types. The exhaust emission standards in this section 
apply for engines using the fuel type on which the engines in the 
engine family are designed to operate. You must meet the numerical 
emission standards for HC in this section based on the following types 
of hydrocarbon emissions for engines powered by the following fuels:
    (1) Alcohol-fueled engines: NMHCE emissions.
    (2) Gaseous-fueled engines: NMNEHC emissions.
    (3) Other engines: NMHC emissions.
    (e) Useful life. The exhaust emission standards of this section 
apply for the useful life, expressed in vehicle miles, or hours of 
engine operation, or years in service, whichever comes first, as 
follows:

           Table 4 to Paragraph (e) of Sec.   1036.104--Useful Life by Primary Intended Service Class
----------------------------------------------------------------------------------------------------------------
                                                  Model year 2026 and earlier       Model year 2027 and later
        Primary intended service class         -----------------------------------------------------------------
                                                  Miles      Years      Hours      Miles      Years      Hours
----------------------------------------------------------------------------------------------------------------
Spark-ignition HDE............................    110,000         10  .........    200,000         15     10,000
Light HDE.....................................    110,000         10  .........    270,000         15     13,000
Medium HDE....................................    185,000         10  .........    350,000         12     17,000
Heavy HDE.....................................    435,000         10     22,000    650,000         11     32,000
----------------------------------------------------------------------------------------------------------------

    (f) Applicability for testing. The emission standards in this 
subpart apply to all testing, including certification, selective 
enforcement audits, and in-use testing. For selective enforcement 
audits, we may require you to perform the appropriate duty-cycle 
testing as specified in Sec. Sec.  1036.510, 1036.512, and 1036.514. We 
may direct you to do additional testing to show that your engines meet 
the off-cycle standards.

Sec.  1036.108  Greenhouse gas emission standards--CO2, CH4, and N2O.

    This section contains standards and other regulations applicable to 
the emission of the air pollutant defined as the aggregate group of six 
greenhouse gases: carbon dioxide, nitrous oxide, methane, 
hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride. This 
section describes the applicable CO2, N2O, and 
CH4 standards for engines.
    (a) Emission standards. Emission standards apply for engines and 
optionally powertrains measured using the test procedures specified in 
subpart F of this part as follows:
    (1) CO2 emission standards in this paragraph (a)(1) 
apply based on testing as specified in subpart F of this part. The 
applicable test cycle for measuring CO2 emissions differs 
depending on the engine family's primary intended service class and the 
extent to which the engines will be (or were designed to be) used in 
tractors. For Medium HDE and Heavy HDE certified as tractor engines, 
measure CO2 emissions using the SET steady-state duty cycle 
specified in Sec.  1036.510. This testing with the SET duty cycle is 
intended for engines designed to be used primarily in tractors and 
other line-haul applications. Note that the use of some SET-certified 
tractor engines in vocational applications does not affect your 
certification obligation under this paragraph (a)(1); see other 
provisions of this part and 40 CFR part 1037 for limits on using 
engines certified to only one cycle. For Medium HDE and Heavy HDE 
certified as both tractor and vocational engines, measure 
CO2 emissions using the SET duty cycle specified in Sec.  
1036.510 and the FTP transient duty cycle specified in Sec.  1036.512. 
Testing with both SET and FTP duty cycles is intended for engines that 
are designed for use in both tractor and vocational applications. For 
all other engines (including Spark-ignition HDE), measure 
CO2 emissions using the FTP transient duty cycle specified 
in Sec.  1036.512.
    (i) The Phase 1 CO2 standard is 627 g/hp[middot]hr for 
all spark-ignition engines for model years 2016 through 2020. This 
standard continues to apply in later model years for all spark-ignition 
engines that are not Heavy HDE.
    (ii) The following Phase 1 CO2 standards apply for 
compression-ignition engines (in g/hp[middot]hr):

 Table 1 to Paragraph (a)(1)(ii) of Sec.   1036.108--Compression-Ignition Engine Standards for Model Years 2014-
                                                      2020
----------------------------------------------------------------------------------------------------------------
                                                  Medium HDE--     Heavy HDE--     Medium HDE--     Heavy HDE--
          Model years              Light HDE       vocational       vocational        tractor         tractor
----------------------------------------------------------------------------------------------------------------
2014-2016.....................             600              600              567             502             475
2017-2020.....................             576              576              555             487             460
----------------------------------------------------------------------------------------------------------------

[[Page 4491]]

    (iii) The following Phase 2 CO2 standards apply for 
compression-ignition engines and all Heavy HDE (in g/hp[middot]hr):

 Table 2 to Paragraph (a)(1)(iii) of Sec.   1036.108--Compression-Ignition Engine Standards for Model Years 2021
                                                    and Later
----------------------------------------------------------------------------------------------------------------
                                                  Medium HDE--     Heavy HDE--     Medium HDE--     Heavy HDE--
          Model years              Light HDE       vocational       vocational        tractor         tractor
----------------------------------------------------------------------------------------------------------------
2021-2023.....................             563              545              513             473             447
2024-2026.....................             555              538              506             461             436
2027 and later................             552              535              503             457             432
----------------------------------------------------------------------------------------------------------------

    (iv) You may certify spark-ignition engines to the compression-
ignition standards for the appropriate model year under this paragraph 
(a). If you do this, those engines are treated as compression-ignition 
engines for all the provisions of this part.
    (2) The CH4 emission standard is 0.10 g/hp[middot]hr 
when measured over the applicable FTP transient duty cycle specified in 
Sec.  1036.512. This standard begins in model year 2014 for 
compression-ignition engines and in model year 2016 for spark-ignition 
engines. Note that this standard applies for all fuel types just like 
the other standards of this section.
    (3) The N2O emission standard is 0.10 g/hp[middot]hr 
when measured over the applicable FTP transient duty cycle specified in 
Sec.  1036.512. This standard begins in model year 2014 for 
compression-ignition engines and in model year 2016 for spark-ignition 
engines.
    (b) Family Certification Levels. You must specify a CO2 
Family Certification Level (FCL) for each engine family expressed to 
the same number of decimal places as the emission standard. The FCL may 
not be less than the certified emission level for the engine family. 
The CO2 family emission limit (FEL) for the engine family is 
equal to the FCL multiplied by 1.03.
    (c) Averaging, banking, and trading. You may generate or use 
emission credits under the averaging, banking, and trading (ABT) 
program described in subpart H of this part for demonstrating 
compliance with CO2 emission standards. Credits (positive 
and negative) are calculated from the difference between the FCL and 
the applicable emission standard. As described in Sec.  1036.705, you 
may use CO2 credits to certify your engine families to FELs 
for N2O and/or CH4, instead of the 
N2O/CH4 standards of this section that otherwise 
apply. Except as specified in Sec. Sec.  1036.150 and 1036.705, you may 
not generate or use credits for N2O or CH4 
emissions.
    (d) Useful life. The exhaust emission standards of this section 
apply for the useful life, expressed as vehicle miles, or hours of 
engine operation, or years in service, whichever comes first, as 
follows:

   Table 3 to Paragraph (d) of Sec.   1036.108--Useful Life by Primary
          Intended Service Class for Model Year 2021 and Later
------------------------------------------------------------------------
     Primary intended service class            Miles           Years
------------------------------------------------------------------------
Spark-ignition HDE \a\..................         150,000              15
Light HDE \a\...........................         150,000              15
Medium HDE..............................         185,000              10
Heavy HDE \b\...........................         435,000              10
------------------------------------------------------------------------
\a\ Useful life for Spark-ignition HDE and Light HDE before model year
  2021 is 110,000 miles or 10 years, whichever occurs first.
\b\ Useful life for Heavy HDE is also expressed as 22,000 operating
  hours. For an individual engine, the useful life is no shorter than 10
  years or 100,000 miles, whichever occurs first, regardless of
  operating hours.

    (e) Applicability for testing. The emission standards in this 
subpart apply as specified in this paragraph (e) to all duty-cycle 
testing (according to the applicable test cycles) of testable 
configurations, including certification, selective enforcement audits, 
and in-use testing. The CO2 FCLs serve as the CO2 
emission standards for the engine family with respect to certification 
and confirmatory testing instead of the standards specified in 
paragraph (a)(1) of this section. The FELs serve as the emission 
standards for the engine family with respect to all other duty-cycle 
testing. See Sec. Sec.  1036.235 and 1036.241 to determine which engine 
configurations within the engine family are subject to testing. Note 
that engine fuel maps and powertrain test results also serve as 
standards as described in Sec. Sec.  1036.535, 1036.540, and 1036.630 
and 40 CFR 1037.550.

Sec.  1036.110  Diagnostic controls.

    Onboard diagnostic (OBD) systems must generally detect malfunctions 
in the emission control system, store trouble codes corresponding to 
detected malfunctions, and alert operators appropriately. Starting in 
model year 2027, new engines must have OBD systems as described in this 
section. You may optionally comply with any or all of the requirements 
of this section instead of 40 CFR 86.010-18 in earlier model years.
    (a) Chassis-based OBD requirements apply instead of the 
requirements of this section for certain engines as follows:
    (1) Heavy-duty engines intended to be installed in heavy duty 
vehicles at or below 14,000 pounds GVWR must meet the requirements in 
40 CFR 86.1806. Note that 40 CFR 86.1806 allows for using later 
versions of specified OBD requirements from the California Air 
Resources Board, which includes meeting the 2019 heavy-duty OBD 
requirements adopted for California and updated emission thresholds as 
described in this section.
    (2) Heavy-duty spark-ignition engines intended to be installed in 
heavy-duty vehicles above 14,000 pounds GVWR may meet the requirements 
in 40 CFR 86.1806 if the same engines are also installed in vehicles 
certified under 40 CFR part 86, subpart S, where both sets

[[Page 4492]]

of vehicles share similar emission controls.
    (b) Engines must comply with the 2019 heavy-duty OBD requirements 
adopted for California as described in this paragraph (b). California's 
2019 heavy-duty OBD requirements are part of 13 CCR 1968.2, 1968.5, 
1971.1, and 1971.5 (incorporated by reference in Sec.  1036.810). We 
may approve your request to certify an OBD system meeting alternative 
specifications if you submit information as needed to demonstrate that 
it meets the intent of this section. For example, we may approve your 
request for a system that meets a later version of California's OBD 
requirements if you demonstrate that it meets the intent of this 
section; the demonstration must include identification of any approved 
deficiencies and your plans to resolve such deficiencies. To 
demonstrate that your engine meets the intent of this section, the OBD 
system meeting alternative specifications must address all the 
provisions described in this paragraph (b) and in paragraph (c) of this 
section. The following clarifications and exceptions apply for engines 
certified under this part:
    (1) We may approve a small manufacturer's request to delay 
complying with the requirements of this section for up to three model 
years if that manufacturer has not certified those engines or other 
comparable engines in California for those model years.
    (2) For engines not certified in California, references to vehicles 
meeting certain California Air Resources Board emission standards are 
understood to refer to the corresponding EPA emission standards for a 
given family, where applicable. Use good engineering judgment to 
correlate the specified standards with the EPA standards that apply 
under this part. You must describe in your application for 
certification how you will perform testing to demonstrate compliance 
with OBD requirements to represent all your engine families over five 
or fewer model years.
    (3) Engines must comply with OBD requirements throughout the useful 
life as specified in Sec.  1036.104(e).
    (4) The purpose and applicability statements in 13 CCR 1971.1(a) 
and (b) do not apply.
    (5) Emission thresholds apply as follows:
    (i) Spark-ignition engines are subject to a NOX 
threshold of 0.35 g/hp[middot]hr for catalyst monitoring and 0.30 g/
hp[middot]hr in all other cases. Spark-ignition engines are subject to 
a PM threshold of 0.015 g/hp[middot]hr. Thresholds apply for operation 
on the FTP and SET duty cycles.
    (ii) Compression-ignition engines are subject to a NOX 
threshold of 0.40 g/hp[middot]hr and a PM threshold of 0.03 g/
hp[middot]hr for operation on the FTP and SET duty cycles.
    (iii) All engines are subject to HC and CO thresholds as specified 
in 13 CCR 1968.2 and 1971.1, except that the ``applicable standards'' 
for determining these thresholds are 0.14 g/hp[middot]hr for HC, 14.4 
g/hp[middot]hr for CO from spark-ignition engines, and 15.5 g/
hp[middot]hr for CO from compression-ignition engines.
    (iv) Compression-ignition engines may be exempt from certain 
monitoring in 13 CCR 1968.2 and 1971.1 based on specified test-out 
criteria. To calculate these test-out criteria, the ``applicable 
standards'' are 0.20 g/hp[middot]hr for NOX, 0.14 g/
hp[middot]hr for HC, 0.01 g/hp[middot]hr for PM, 14.4 g/hp[middot]hr 
for CO from spark-ignition engines, and 15.5 g/hp[middot]hr for CO from 
compression-ignition engines.
    (6) The provisions related to verification of in-use compliance in 
13 CCR 1971.1(l) do not apply. The provisions related to manufacturer 
self-testing in 13 CCR 1971.5(c) also do not apply.
    (7) The deficiency provisions described in paragraph (d) of this 
section apply instead of 13 CCR 1971.1(k).
    (8) Include the additional data-stream signals in 13 CCR 
1971.1(h)(4.2.3)(E), (F), and (G) as freeze-frame conditions as 
required in 13 CCR 1971.1(h)(4.3).
    (9) Design compression-ignition engines to make the following 
additional data-stream signals available on demand with a generic scan 
tool according to 13 CCR 1971.1(h)(4.2), if the engine is so equipped:
    (i) Engine and vehicle parameters. Status of parking brake, neutral 
switch, brake switch, and clutch switch, wastegate control solenoid 
output, wastegate position (commanded and actual), speed and output 
shaft torque consistent with Sec.  1036.115(d).
    (ii) Diesel oxidation catalyst parameters. Include inlet and outlet 
pressure and temperature for the diesel oxidation catalyst.
    (iii) Particulate filter parameters. Include filter soot load and 
ash load for all installed particulate filters.
    (iv) EGR parameters. Include differential pressure for exhaust gas 
recirculation.
    (v) SCR parameters. Include DEF quality-related signals, DEF 
coolant control valve position (commanded and actual), DEF tank 
temperature, DEF system pressure, DEF pump commanded percentage, DEF 
doser control status, DEF line heater control outputs, aftertreatment 
dosing quantity commanded and actual.
    (vi) Derating parameters. Include any additional parameters used to 
apply inducements under Sec.  1036.111 or any other SCR-related or DPF-
related engine derates under Sec.  1036.125.
    (10) Design spark-ignition engines to make the following additional 
parameters available for reading with a generic scan tool, if 
applicable:
    (i) Air-fuel enrichment parameters. Percent of time in enrichment, 
both for each trip (key-on to key-off) and as a cumulative lifetime 
value. Track values separately for enrichment based on throttle, engine 
protection, and catalyst protection. Include all time after engine 
warm-up when the engine is not operating at the air-fuel ratio designed 
for peak three-way catalyst efficiency. Peak efficiency typically 
involves closed-loop feedback control.
    (ii) [Reserved]
    (11) If you have an approved Executive order from the California 
Air Resources Board for a given engine family, we may rely on that 
Executive order to evaluate whether you meet federal OBD requirements 
for that same engine family or an equivalent engine family. Engine 
families are equivalent if they are identical in all aspects material 
to emission characteristics; for example, we would consider different 
inducement strategies and different warranties not to be material to 
emission characteristics relevant to these OBD testing requirements. 
EPA would count two equivalent engine families as one for the purposes 
of determining OBD demonstration testing requirements. Send us the 
following information:
    (i) You must submit additional information as needed to demonstrate 
that you meet the requirements of this section that are not covered by 
the California Executive order.
    (ii) Send us results from any testing you performed for certifying 
engine families (including equivalent engine families) with the 
California Air Resources Board, including the results of any testing 
performed under 13 CCR 1971.1(l) for verification of in-use compliance 
and 13 CCR 1971.5(c) for manufacturer self-testing within the deadlines 
set out in 13 CCR 1971.1.
    (iii) We may require that you send us additional information if we 
need it to evaluate whether you meet the requirements of this paragraph 
(b)(11). This may involve sending us copies of documents you send to 
the California Air Resources Board.
    (12) You may ask us to approve conditions for which the diagnostic 
system may disregard trouble codes, as described in 13 CCR 
1971.1(g)(5.3)-(5.6).

[[Page 4493]]

    (13) References to the California ARB Executive Officer are deemed 
to be the EPA Administrator.
    (c) Design the diagnostic system to display the following 
information in the cab:
    (1) For inducements specified in Sec.  1036.111 and any other AECD 
that derates engine output related to SCR or DPF systems, indicate the 
fault code for the detected problem, a description of the fault code, 
and the current speed restriction. For inducement faults under Sec.  
1036.111, identify whether the fault condition is for DEF quantity, DEF 
quality, or tampering; for other faults, identify whether the fault 
condition is related to SCR or DPF systems. If there are additional 
derate stages, also indicate the next speed restriction and the time 
remaining until starting the next restriction. If the derate involves 
something other than restricting vehicle speed, such as a torque 
derate, adjust the information to correctly identify any current and 
pending restrictions.
    (2) Identify on demand the total number of diesel particulate 
filter regeneration events that have taken place since installing the 
current particulate filter.
    (3) Identify on demand the historical and current rate of DEF 
consumption, such as gallons of DEF consumed per mile or gallons of DEF 
consumed per gallon of diesel fuel consumed. Design the system to allow 
the operator to reset the current rate of DEF consumption.
    (d) You may ask us to accept as compliant an engine that does not 
fully meet specific requirements under this section. The following 
provisions apply regarding OBD system deficiencies:
    (1) We will not approve a deficiency for gasoline-fueled or diesel-
fueled engines if it involves the complete lack of a major diagnostic 
monitor, such as monitors related to exhaust aftertreatment devices, 
oxygen sensors, air-fuel ratio sensors, NOX sensors, engine 
misfire, evaporative leaks, and diesel EGR (if applicable). We may 
approve such deficiencies for engines using other fuels if you 
demonstrate that the alternative fuel causes these monitors to be 
unreliable.
    (2) We will approve a deficiency only if you show us that full 
compliance is infeasible or unreasonable considering any relevant 
factors, such as the technical feasibility of a given monitor, or the 
lead time and production cycles of vehicle designs and programmed 
computing upgrades.
    (3) Our approval for a given deficiency applies only for a single 
model year, though you may continue to ask us to extend a deficiency 
approval in renewable one-year increments. We may approve an extension 
if you demonstrate an acceptable level of progress toward compliance 
and you show that the necessary hardware or software modifications 
would pose an unreasonable burden. We will approve a deficiency for 
more than three years only if you further demonstrate that you need the 
additional lead time to make substantial changes to engine hardware.
    (4) We will not approve deficiencies retroactively.

Sec.  1036.111  Inducements related to SCR.

    Engines using SCR to control emissions depend on a constant supply 
of diesel exhaust fluid (DEF). This section describes how manufacturers 
must design their engines to derate power output to induce operators to 
take appropriate actions to ensure the SCR system is working properly. 
The requirements of this section apply equally for engines installed in 
heavy-duty vehicles at or below 14,000 lbs GVWR. The requirements of 
this section apply starting in model year 2027, though you may comply 
with the requirements of this section in earlier model years.
    (a) General provisions. The following terms and general provisions 
apply under this section:
    (1) As described in Sec.  1036.110, this section relies on terms 
and requirements specified for OBD systems by California ARB in 13 CCR 
1968.2 and 1971.1 (incorporated by reference in Sec.  1036.810).
    (2) The provisions of this section apply differently based on an 
individual vehicle's speed history. A vehicle's speed category is based 
on the OBD system's recorded value for average speed for the preceding 
30 hours of non-idle engine operation. The vehicle speed category 
applies at the point that the engine first detects a fault condition 
identified under paragraph (b) of this section and continues to apply 
until the fault condition is fully resolved as specified in paragraph 
(e) of this section. Non-idle engine operation includes all operating 
conditions except those that qualify as idle based on OBD system 
controls as specified in 13 CCR 1971.1(h)(5.4.10). Apply speed derates 
based on the following categories:

   Table 1 to Paragraph (a)(2) of Sec.   1036.111--Vehicle Categories
------------------------------------------------------------------------
             Vehicle category                   Average speed (mi/hr)
------------------------------------------------------------------------
Low-speed.................................  speed <15.
Medium-speed..............................  15 <=speed <25.
High-speed................................  speed >=25.
------------------------------------------------------------------------

    (3) Where engines derate power output as specified in this section, 
the derate must decrease vehicle speed by 1 mi/hr for every five 
minutes of engine operation until reaching the specified derate speed. 
This requirement applies at the onset of an inducement, at any 
transition to a different step of inducement, and for any derate that 
recurs under paragraph (e)(3) of this section.
    (b) Fault conditions. Create derate strategies that monitor for and 
trigger an inducement based on the following conditions:
    (1) DEF supply falling to a level corresponding to three hours of 
engine operation, based on available information on DEF consumption 
rates.
    (2) DEF quality failing to meet your concentration specifications.
    (3) Any signal indicating that a catalyst is missing.
    (4) Open circuit faults related to the following: DEF tank level 
sensor, DEF pump, DEF quality sensor, SCR wiring harness, 
NOX sensors, DEF dosing valve, DEF tank heater, DEF tank 
temperature sensor, and aftertreatment control module.
    (c) [Reserved]
    (d) Derate schedule. Engines must follow the derate schedule 
described in this paragraph (d) if the engine detects a fault condition 
identified in paragraph (b) of this section. The derate takes the form 
of a maximum drive speed for the vehicle. This maximum drive speed 
decreases over time based on hours of non-idle engine operation without 
regard to engine starting.
    (1) Apply speed-limiting derates according to the following 
schedule:

[[Page 4494]]

               Table 2 to Paragraph (d)(1) of Sec.   1036.111--Derate Schedule for Detected Faults
----------------------------------------------------------------------------------------------------------------
         High-speed vehicles                   Low-speed vehicles                    Low-speed vehicles
----------------------------------------------------------------------------------------------------------------
Hours of non-idle  Maximum speed (mi/ Hours of non-idle  Maximum speed (mi/ Hours of non-idle  Maximum speed (mi/
 engine operation         hr)          engine operation         hr)          engine operation         hr)
----------------------------------------------------------------------------------------------------------------
             0                 65                  0                 55                  0                 45
             6                 60                  6                 50                  5                 40
            12                 55                 12                 45                 10                 35
            20                 50                 45                 40                 30                 25
            86                 45                 70                 35     .................  .................
           119                 40                 90                 25     .................  .................
           144                 35     .................  .................  .................  .................
           164                 25     .................  .................  .................  .................
----------------------------------------------------------------------------------------------------------------
\a\ Hours start counting when the engine detects a fault condition specified in paragraph (b) of this section.
  For DEF supply, you may program the engine to reset the timer to three hours when the engine detects an empty
  DEF tank.

    (2) You may design and produce engines that will be installed in 
motorcoaches with an alternative derate schedule that starts with a 65 
mi/hr derate when a fault condition is first detected, steps down to 50 
mi/hr after 80 hours, and concludes with a final derate speed of 25 mi/
hr after 180 hours of non-idle operation.
    (e) Deactivating derates. Program the engine to deactivate derates 
as follows:
    (1) Evaluate whether the detected fault condition continues to 
apply. Deactivate derates if the engine confirms that the detected 
fault condition is resolved.
    (2) Allow a generic scan tool to deactivate inducement-related 
fault codes while the vehicle is not in motion.
    (3) Treat any detected fault condition that recurs within 40 hours 
of engine operation as the same detected fault condition, which would 
restart the derate at the same point in the derate schedule that the 
system last deactivated the derate.

Sec.  1036.115  Other requirements.

    Engines that are required to meet the emission standards of this 
part must meet the following requirements, except as noted elsewhere in 
this part:
    (a) Crankcase emissions. Engines may not discharge crankcase 
emissions into the ambient atmosphere throughout the useful life, other 
than those that are routed to the exhaust upstream of exhaust 
aftertreatment during all operation, except as follow:
    (1) Engines equipped with turbochargers, pumps, blowers, or 
superchargers for air induction may discharge crankcase emissions to 
the ambient atmosphere if the emissions are added to the exhaust 
emissions (either physically or mathematically) during all emission 
testing.
    (2) If you take advantage of this exception, you must manufacture 
the engines so that all crankcase emissions can be routed into the 
applicable sampling systems specified in 40 CFR part 1065. You must 
also account for deterioration in crankcase emissions when determining 
exhaust deterioration factors as described in Sec.  1036.240(c)(5).
    (b) Fuel mapping. You must perform fuel mapping for your engine as 
described in Sec.  1036.505(b).
    (c) Evaporative and refueling emissions. You must design and 
produce your engines to comply with evaporative and refueling emission 
standards as follows:
    (1) For complete heavy-duty vehicles you produce, you must certify 
the vehicles to emission standards as specified in 40 CFR 1037.103.
    (2) For incomplete heavy-duty vehicles, and for engines used in 
vehicles you do not produce, you do not need to certify your engines to 
evaporative and refueling emission standards or otherwise meet those 
standards. However, vehicle manufacturers certifying their vehicles 
with your engines may depend on you to produce your engines according 
to their specifications. Also, your engines must meet applicable 
exhaust emission standards in the installed configuration.
    (d) Torque broadcasting. Electronically controlled engines must 
broadcast their speed and output shaft torque (in newton-meters). 
Engines may alternatively broadcast a surrogate value for determining 
torque. Engines must broadcast engine parameters such that they can be 
read with a remote device or broadcast them directly to their 
controller area networks.
    (e) EPA access to broadcast information. If we request it, you must 
provide us any hardware, tools, and information we would need to 
readily read, interpret, and record all information broadcast by an 
engine's on-board computers and electronic control modules. If you 
broadcast a surrogate parameter for torque values, you must provide us 
what we need to convert these into torque units. We will not ask for 
hardware or tools if they are readily available commercially.
    (f) Adjustable parameters. Engines that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range.
    (1) We may require that you set adjustable parameters to any 
specification within the practically adjustable range during any 
testing, including certification testing, selective enforcement 
auditing, or in-use testing.
    (2) General provisions apply for adjustable parameters as specified 
in 40 CFR 1068.50.
    (3) DEF supply and DEF quality are adjustable parameters. The 
physically adjustable range includes any amount of DEF for which the 
engine's diagnostic system does not trigger inducement provisions under 
Sec.  1036.111.
    (g) Prohibited controls. (1) General provisions. You may not design 
your engines with emission control devices, systems, or elements of 
design that cause or contribute to an unreasonable risk to public 
health, welfare, or safety while operating. For example, this would 
apply if the engine emits a noxious or toxic substance it would 
otherwise not emit that contributes to such an unreasonable risk.
    (2) Vanadium sublimation in SCR catalysts. For engines equipped 
with vanadium-based SCR catalysts, you must design the engine and its 
emission controls to prevent vanadium sublimation and protect the 
catalyst from high temperatures. We will evaluate your engine design 
based on the following information that you must include in your 
application for certification:
    (i) Identify the threshold temperature for vanadium sublimation for 
your specified SCR catalyst formulation as

[[Page 4495]]

described in 40 CFR 1065.1113 through 1065.1121.
    (ii) Describe how you designed your engine to prevent catalyst 
inlet temperatures from exceeding the temperature you identify in 
paragraph (g)(2)(i) of this section, including consideration of engine 
wear through the useful life. Also describe your design for catalyst 
protection in case catalyst temperatures exceed the specified 
temperature. In your description, include how you considered elevated 
catalyst temperature resulting from sustained high-load engine 
operation, catalyst exotherms, particulate filter regeneration, and 
component failure resulting in unburned fuel in the exhaust stream.
    (h) Defeat devices. You may not equip your engines with a defeat 
device. A defeat device is an auxiliary emission control device (AECD) 
that reduces the effectiveness of emission controls under conditions 
that may reasonably be expected in normal operation and use. However, 
an AECD is not a defeat device if you identify it in your application 
for certification and any of the following is true:
    (1) The conditions of concern were substantially included in the 
applicable procedure for duty-cycle testing as described in subpart F 
of this part.
    (2) You show your design is necessary to prevent engine (or 
vehicle) damage or accidents. Preventing engine damage includes 
preventing damage to aftertreatment or other emission-related 
components.
    (3) The reduced effectiveness applies only to starting the engine.
    (4) The AECD applies only for engines that will be installed in 
emergency vehicles, and the need is justified in terms of preventing 
the engine from losing speed, torque, or power due abnormal conditions 
of the emission control system, or in terms of preventing such abnormal 
conditions from occurring, during operation related to emergency 
response. Examples of such abnormal conditions may include excessive 
exhaust backpressure from an overloaded particulate trap, and running 
out of diesel exhaust fluid for engines that rely on urea-based 
selective catalytic reduction.
    (i) DEF tanks. Diesel exhaust fluid tanks must be sized to require 
refilling no more frequently than the vehicle operator will need to 
refill the fuel tank, even for worst-case assumptions related to fuel 
efficiency and refueling volumes.
    (j) Special provisions for spark-ignition engines. The following 
provisions apply for spark-ignition engines that control air-fuel 
ratios at or near stoichiometry starting with model year 2027:
    (1) Catalyst bed temperature during extended idle may not fall 
below 350 [deg]C, or a lower temperature that we approve. Describe how 
you designed your engine to meet this requirement in your application 
for certification. You may ask us to approve alternative strategies to 
prevent emissions from increasing during idle.
    (2) In addition to the information requirements of Sec.  
1036.205(b), describe why you rely on any AECDs instead of other engine 
designs for thermal protection of catalyst or other emission-related 
components. Also describe the accuracy of any modeled or measured 
temperatures used to activate the AECD. We may ask you to submit a 
second-by-second comparison of any modeled and measured component 
temperatures as part of your application for certification.

Sec.  1036.120  Emission-related warranty requirements.

    (a) General requirements. You must warrant to the ultimate 
purchaser and each subsequent purchaser that the new engine, including 
all parts of its emission control system, meets two conditions:
    (1) It is designed, built, and equipped so it conforms at the time 
of sale to the ultimate purchaser with the requirements of this part.
    (2) It is free from defects in materials and workmanship that may 
keep it from meeting these requirements.
    (b) Warranty period. Your emission-related warranty must be valid 
for at least as long as the minimum warranty periods listed in this 
paragraph (b) in vehicle miles, or hours of engine operation, or years 
in service, whichever comes first. You may offer an emission-related 
warranty more generous than we require. The emission-related warranty 
for the engine may not be shorter than any published warranty you offer 
without charge for the engine. Similarly, the emission-related warranty 
for any component may not be shorter than any published warranty you 
offer without charge for that component. If an extended warranty 
requires owners to pay for a portion of repairs, those terms apply in 
the same manner to the emission-related warranty. The warranty period 
begins when the vehicle is placed into service. The following minimum 
warranty periods apply:

                                 Table 1 to Paragraph (b) of Sec.   1036.120--Warranty by Primary Intended Service Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                    Model year 2026 and earlier                      Model year 2027 and later
             Primary intended service class              -----------------------------------------------------------------------------------------------
                                                              Mileage          Years           Hours          Mileage          Years           Hours
--------------------------------------------------------------------------------------------------------------------------------------------------------
Spark-Ignition HDE......................................          50,000               5  ..............         160,000              10           8,000
Light HDE...............................................          50,000               5  ..............         210,000              10          10,000
Medium HDE..............................................         100,000               5  ..............         280,000              10          14,000
Heavy HDE...............................................         100,000               5  ..............         450,000              10          22,000
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (c) Components covered. The emission-related warranty covers all 
components listed in 40 CFR part 1068, appendix A, and components from 
any other system you develop to control emissions. The emission-related 
warranty covers any components, regardless of the company that produced 
them, that are the original components or the same design as components 
from the certified configuration.
    (d) Limited applicability. You may deny warranty claims under this 
section if the operator caused the problem through improper maintenance 
or use, subject to the provisions in Sec.  1036.125 and 40 CFR 
1068.115.
    (e) Owners manual. Describe in the owners manual the emission-
related warranty provisions from this section that apply to the engine.

Sec.  1036.125  Maintenance instructions and allowable maintenance.

    Maintenance includes any inspection, adjustment, cleaning, repair, 
or replacement of components and is classified as either emission-
related or not emission-related and each of these can be classified as 
either scheduled or

[[Page 4496]]

unscheduled. Further, some emission-related maintenance is also 
classified as critical emission-related maintenance. Give the ultimate 
purchaser of each new engine written instructions for maintaining and 
using the engine. As described in paragraph (h) of this section, these 
instructions must identify how owners properly maintain and use engines 
to clarify responsibilities for regulatory requirements such as 
emission-related warranty and defect reporting.
    (a) Critical emission-related maintenance. Critical emission-
related maintenance includes any adjustment, cleaning, repair, or 
replacement of components listed in paragraph (a)(2) of this section. 
Critical emission-related maintenance may also include other 
maintenance that you determine is critical, including maintenance on 
other emission-related components as described in 40 CFR part 1068, 
appendix A, if we approve it in advance. You may perform scheduled 
critical emission-related maintenance during service accumulation on 
your emission-data engines at the intervals you specify.
    (1) Maintenance demonstration. You must demonstrate that the 
maintenance is reasonably likely to be done at your recommended 
intervals on in-use engines. We will accept DEF replenishment as 
reasonably likely to occur if your engine meets the specifications in 
Sec.  1036.111. We will accept other scheduled maintenance as 
reasonably likely to occur if you satisfy any of the following 
conditions:
    (i) You present data showing that, if a lack of maintenance 
increases emissions, it also unacceptably degrades the engine's 
performance.
    (ii) You design and produce your engines with a system we approve 
that displays a visible signal to alert drivers that maintenance is 
due, either as a result of component failure or the appropriate degree 
of engine or vehicle operation. The signal must clearly display 
``maintenance needed'', ``check engine'', or a similar message that we 
approve. The signal must be continuous while the engine is operating 
and not be easily eliminated without performing the specified 
maintenance. Your maintenance instructions must specify resetting the 
signal after completing the specified maintenance. We must approve the 
method for resetting the signal. You may not design the system to be 
less effective at the end of the useful life. If others install your 
engine in their vehicle, you may rely on installation instructions to 
ensure proper mounting and operation of the display. Disabling or 
improperly resetting the system for displaying these maintenance-
related signals without performing the indicated maintenance violates 
the tampering prohibition in 42 U.S.C. 7522(a)(3).
    (iii) You present survey data showing that at least 80 percent of 
engines in the field get the maintenance you specify at the recommended 
intervals.
    (iv) You provide the maintenance free of charge and clearly say so 
in your maintenance instructions.
    (v) You otherwise show us that the maintenance is reasonably likely 
to be done at the recommended intervals.
    (2) Minimum scheduled maintenance intervals. You may not schedule 
critical emission-related maintenance more frequently than the minimum 
intervals specified or allowed in this paragraph (a), except as 
specified in paragraph (g) of this section. The minimum intervals 
specified for each component applies to actuators, sensors, tubing, 
valves, and wiring associated with that component, except as specified.

Table 1 to Paragraph (a)(2) of Sec.   1036.125--Minimum Scheduled Maintenance Intervals for Replacement in Miles
                                                   (or Hours)
----------------------------------------------------------------------------------------------------------------
                                                  Spark-ignition
                   Components                           HDE          Light HDE      Medium HDE       Heavy HDE
----------------------------------------------------------------------------------------------------------------
Spark plugs.....................................    25,000 (750)  ..............  ..............  ..............
DEF filters.....................................  ..............         100,000         100,000         100,000
                                                                         (3,000)         (3,000)         (3,000)
Crankcase ventilation valves and filters........  60,000 (1,800)  60,000 (1,800)  60,000 (1,800)  60,000 (1,800)
Ignition wires and coils........................  50,000 (1,500)  ..............  ..............  ..............
Oxygen sensors..................................  80,000 (2,400)  ..............  ..............  ..............
Air injection system components.................         110,000  ..............  ..............  ..............
                                                         (3,300)
Sensors, actuators, and related control modules          100,000         100,000         150,000         150,000
 that are not integrated into other systems.....         (3,000)         (3,000)         (4,500)         (4,500)
Particulate filtration systems (other than               100,000  100,000 3,000)  250,000 7,500)         250,000
 filter substrates).............................         (3,000)                                         (7,500)
Catalyst systems (other than catalyst                    110,000         110,000  185,000 5,550)         435,000
 substrates), fuel injectors, electronic control         (3,300)         (3,300)                        (13,050)
 modules, hybrid system components,
 turbochargers, and EGR system components
 (including filters and coolers) ...............
Catalyst substrates and particulate filter               200,000         270,000         350,000         650,000
 substrates.....................................        (10,000)        (13,000)        (17,000)        (32,000)
----------------------------------------------------------------------------------------------------------------

    Table 2 to Paragraph (a)(2) of Sec.   1036.125--Minimum Scheduled Maintenance Intervals for Adjustment or
                                                    Cleaning
----------------------------------------------------------------------------------------------------------------
                                                      Accumulated miles (hours) for components
                                   -----------------------------------------------------------------------------
             Component              Spark-ignition
                                          HDE          Light HDE          Medium HDE             Heavy HDE
----------------------------------------------------------------------------------------------------------------
Spark plugs.......................    25,000 (750)
EGR-related filters and coolers,    50,000 (1,500)  50,000 (1,500)  50,000 (1,500).......  50,000 (1,500)
 fuel injectors, and crankcase
 ventilation valves and filters.
DEF filters.......................  ..............  50,000 (1,500)  50,000 (1,500).......  50,000 (1,500)

[[Page 4497]]

 
Ignition wires and coils..........  50,000 (1,500)
Oxygen sensors....................  80,000 (2,400)
Air injection system components...         100,000
                                           (3,000)
Catalyst system components, EGR            100,000         100,000  100,000 (3,000), then  100,000 (3,000), then
 system components (other than             (3,000)         (3,000)   50,000 (4,500).        150,000 (4,500)
 filters or coolers), particulate
 filtration system components, and
 turbochargers.
----------------------------------------------------------------------------------------------------------------

    (3) New technology. You may ask us to approve scheduled critical 
emission-related maintenance of components not identified in paragraph 
(a)(2) of this section that is a direct result of the implementation of 
new technology not used in model year 2020 or earlier engines, subject 
to the following provisions:
    (i) Your request must include your recommended maintenance 
interval, including data to support the need for the maintenance, and a 
demonstration that the maintenance is likely to occur at the 
recommended interval using one of the conditions specified in paragraph 
(a)(1) of this section.
    (ii) For any such new technology, we will publish a Federal 
Register notice based on information you submit and any other available 
information to announce that we have established new allowable minimum 
maintenance intervals. Any manufacturer objecting to our decision may 
ask for a hearing (see Sec.  1036.820).
    (4) System components. The following provisions clarify which 
components are included in certain systems:
    (i) Catalyst system refers to the aftertreatment assembly used for 
gaseous emission control and generally includes catalyst substrates, 
substrate housings, exhaust gas temperature sensors, gas concentration 
sensors, and related control modules. SCR-based catalyst systems also 
include DEF level sensors, DEF quality sensors, and DEF temperature 
sensors.
    (ii) Particulate filtration system refers to the aftertreatment 
assembly used for exhaust PM filtration and generally includes filter 
substrates, substrate housings, pressure sensors, pressure lines and 
tubes, exhaust gas temperature sensors, fuel injectors for active 
regeneration, and related control modules.
    (b) Recommended additional maintenance. You may recommend any 
amount of critical emission-related maintenance that is additional to 
what we approve in paragraph (a) of this section, as long as you state 
clearly that the recommended additional maintenance steps are not 
necessary to keep the emission-related warranty valid. If operators do 
the maintenance specified in paragraph (a) of this section, but not the 
recommended additional maintenance, this does not allow you to 
disqualify those engines from in-use testing or deny a warranty claim. 
Do not take these maintenance steps during service accumulation on your 
emission-data engines.
    (c) Special maintenance. You may specify more frequent maintenance 
to address problems related to special situations, such as atypical 
engine operation. For example, you may specify more frequent 
maintenance if operators fuel the engine with an alternative fuel such 
as biodiesel. You must clearly state that this special maintenance is 
associated with the special situation you are addressing. We may 
disapprove your maintenance instructions if we determine that you have 
specified special maintenance steps to address engine operation that is 
not atypical, or that the maintenance is unlikely to occur in use. If 
we determine that certain maintenance items do not qualify as special 
maintenance under this paragraph (c), you may identify them as 
recommended additional maintenance under paragraph (b) of this section.
    (d) Noncritical emission-related maintenance. You may specify any 
amount of emission-related inspection or other maintenance that is not 
approved critical emission-related maintenance under paragraph (a) of 
this section, subject to the provisions of this paragraph (d). 
Noncritical emission-related maintenance generally includes maintenance 
on the components we specify in 40 CFR part 1068, appendix A, that is 
not covered in paragraph (a) of this section. You must state in the 
owners manual that these steps are not necessary to keep the emission-
related warranty valid. If operators fail to do this maintenance, this 
does not allow you to disqualify those engines from in-use testing or 
deny a warranty claim. Do not take these inspection or other 
maintenance steps during service accumulation on your emission-data 
engines.
    (e) Maintenance that is not emission-related. You may schedule any 
amount of maintenance unrelated to emission controls that is needed for 
proper functioning of the engine. This might include adding engine oil; 
changing air, fuel, or oil filters; servicing engine-cooling systems; 
adjusting idle speed, governor, engine bolt torque, valve lash, 
injector lash, timing, or tension of air pump drive belts; and 
lubricating the heat control valve in the exhaust manifold. For 
maintenance that is not emission-related, you may perform the 
maintenance during service accumulation on your emission-data engines 
at the least frequent intervals that you recommend to the ultimate 
purchaser (but not the intervals recommended for special situations).
    (f) [Reserved]
    (g) Payment for scheduled maintenance. Owners are responsible for 
properly maintaining their engines, which generally includes paying for 
scheduled maintenance. However, you may commit to paying for scheduled 
maintenance as described in paragraph (a)(1)(iv) of this section to 
demonstrate that the maintenance will occur. You may also schedule 
maintenance not otherwise allowed by paragraph (a)(2) of this section 
if you pay for it. You must pay for scheduled maintenance on any 
component during the useful life if it meets all the following 
conditions:
    (1) Each affected component was not in general use on similar 
engines before 1980.
    (2) The primary function of each affected component is to reduce 
emissions.
    (3) The cost of the maintenance is more than 2 percent of the price 
of the engine.

[[Page 4498]]

    (4) Failure to perform the maintenance would not cause clear 
problems that would significantly degrade the engine's performance.
    (h) Owners manual. Include the following maintenance-related 
information in the owners manual, consistent with the requirements of 
this section:
    (1) Clearly describe the scheduled maintenance steps, consistent 
with the provisions of this section, using nontechnical language as 
much as possible. Include a list of components for which you will cover 
scheduled replacement costs.
    (2) Identify all maintenance you consider necessary for the engine 
to be considered properly maintained for purposes of making valid 
warranty claims. Describe what documentation you consider appropriate 
for making these demonstrations. Note that you may identify failure to 
repair critical emission-related components as improper maintenance if 
the repairs are related to an observed defect. Your maintenance 
instructions under this section may not require components or service 
identified by brand, trade, or corporate name. Also, do not directly or 
indirectly require that the engine be serviced by your franchised 
dealers or any other service establishments with which you have a 
commercial relationship. However, you may disregard these limitations 
on your maintenance requirements if you do one of the following things:
    (i) Provide a component or service without charge under the 
purchase agreement.
    (ii) Get us to waive this prohibition in the public's interest by 
convincing us the engine will work properly only with the identified 
component or service.
    (3) Describe how the owner can access the OBD system to 
troubleshoot problems and find emission-related diagnostic information 
and codes stored in onboard monitoring systems as described in Sec.  
1036.110(b) and (c). These instructions must at a minimum include 
identification of the OBD communication protocol used, location and 
type of OBD connector, brief description of what OBD is (including type 
of information stored, what a MIL is, and explanation that some MILs 
may self-extinguish), and a note that generic scan tools can provide 
engine maintenance information.
    (4) Describe the elements of the emission control system and 
provide an overview of how they function.
    (5) Include one or more diagrams of the engine and its emission-
related components with the following information:
    (i) The flow path for intake air and exhaust gas.
    (ii) The flow path of evaporative and refueling emissions for 
spark-ignition engines, and DEF for compression-ignition engines, as 
applicable.
    (iii) The flow path of engine coolant if it is part of the emission 
control system described in the application for certification.
    (iv) The identity, location, and arrangement of relevant sensors, 
DEF heater and other DEF delivery components, and other critical 
emission-related components. Terminology to identify components must be 
consistent with codes you use for the OBD system.
    (6) Include one or more exploded-view drawings that allow the owner 
to identify the following components: EGR valve, EGR actuator, EGR 
cooler, all emission sensors (such as NOX sensors and soot 
sensors), temperature and pressure sensors (such as sensors related to 
EGR, DPF, DOC, and SCR and DEF), quality sensors, DPF filter, DOC, SCR 
catalyst, fuel (DPF-related) and DEF dosing units and components (e.g., 
pumps, metering units, filters, nozzles, valves, injectors), 
aftertreatment-related control modules, any other DEF delivery-related 
components (such as delivery lines and freeze-protection components), 
and separately replaceable aftertreatment-related wiring harnesses. 
Terminology to identify components must be consistent with codes you 
use for the OBD system. Include part numbers for sensors and filters 
related to SCR and DPF systems for the current model year or any 
earlier model year.
    (7) Include the following statement: ``Technical service bulletins, 
emission-related recalls, and other information for your engine may be 
available at www.nhtsa.gov/recalls.''
    (8) Include a troubleshooting guide to address the following 
warning signals related to SCR inducement:
    (i) The inducement derate schedule (including indication that 
inducements will begin prior to the DEF tank being completely empty).
    (ii) The meaning of any trouble lights that indicate specific 
problems (e.g., DEF level).
    (iii) A description of the three types of SCR-related derates (DEF 
quality, DEF quality and tampering) and that further information on the 
inducement cause (e.g., trouble codes) is available using the OBD 
system.
    (9) Describe how to access OBD fault codes related to DPF-related 
derates.
    (10) Identify a website for the service information required in 40 
CFR 86.010-38(j).

Sec.  1036.130  Installation instructions for vehicle manufacturers.

    (a) If you sell an engine for someone else to install in a vehicle, 
give the engine installer instructions for installing it consistent 
with the requirements of this part. Include all information necessary 
to ensure that an engine will be installed in its certified 
configuration.
    (b) Make sure these instructions have the following information:
    (1) Include the heading: ``Emission-related installation 
instructions''.
    (2) State: ``Failing to follow these instructions when installing a 
certified engine in a heavy-duty motor vehicle violates federal law, 
subject to fines or other penalties as described in the Clean Air 
Act.''
    (3) Provide all instructions needed to properly install the exhaust 
system and any other components. Include any appropriate instructions 
for configuring the exhaust system in the vehicle to allow for 
collecting emission samples for in-use testing where that is practical.
    (4) Describe any necessary steps for installing any diagnostic 
system required under Sec.  1036.110.
    (5) Describe how your certification is limited for any type of 
application. For example, if you certify Heavy HDE to the 
CO2 standards using only transient FTP testing, you must 
make clear that the engine may not be installed in tractors.
    (6) Describe any other instructions to make sure the installed 
engine will operate according to design specifications in your 
application for certification. This may include, for example, 
instructions for installing aftertreatment devices when installing the 
engines.
    (7) Give the following instructions if you do not ship diesel 
exhaust fluid tanks with your engines:
    (i) Specify that vehicle manufacturers must install diesel exhaust 
fluid tanks meeting the specifications of Sec.  1036.115(i).
    (ii) Describe how vehicle manufacturers must install diesel exhaust 
fluid tanks with sensors as needed to meet the requirements of 
Sec. Sec.  1036.110 and 1036.111.
    (8) State: ``If you install the engine in a way that makes the 
engine's emission control information label hard to read during normal 
engine maintenance, you must place a duplicate label on the vehicle, as 
described in 40 CFR 1068.105.''
    (9) Describe how vehicle manufacturers need to apply stickers to 
qualifying vehicles as described in Sec.  1036.136 if you certify 
engines to the

[[Page 4499]]

Clean Idle NOX standard of Sec.  1036.104(b).
    (c) Give the vehicle manufacturer fuel map results as described in 
Sec.  1036.505(b).
    (d) You do not need installation instructions for engines that you 
install in your own vehicles.
    (e) Provide instructions in writing or in an equivalent format. For 
example, you may post instructions on a publicly available website for 
downloading or printing. If you do not provide the instructions in 
writing, explain in your application for certification how you will 
ensure that each installer is informed of the installation 
requirements.

Sec.  1036.135  Labeling.

    (a) Assign each engine a unique identification number and 
permanently affix, engrave, or stamp it on the engine in a legible way.
    (b) At the time of manufacture, affix a permanent and legible label 
identifying each engine. The label must meet the requirements of 40 CFR 
1068.45.
    (c) The label must--
    (1) Include the heading ``EMISSION CONTROL INFORMATION''.
    (2) Include your full corporate name and trademark. You may 
identify another company and use its trademark instead of yours if you 
comply with the branding provisions of 40 CFR 1068.45.
    (3) Include EPA's standardized designation for the engine family.
    (4) Identify the primary intended service class.
    (5) State the engine's displacement (in liters); however, you may 
omit this from the label if all the engines in the engine family have 
the same per-cylinder displacement and total displacement.
    (6) State the date of manufacture [DAY (optional), MONTH, and 
YEAR]; however, you may omit this from the label if you stamp, engrave, 
or otherwise permanently identify it elsewhere on the engine, in which 
case you must also describe in your application for certification where 
you will identify the date on the engine.
    (7) State the NOX FEL to which the engines are certified 
if applicable. Identify the Clean Idle standard if you certify the 
engine to the NOX standard of Sec.  1036.104(b).
    (8) State: ``THIS ENGINE COMPLIES WITH U.S. EPA REGULATIONS FOR 
[MODEL YEAR] HEAVY-DUTY HIGHWAY ENGINES.''
    (9) Identify any limitations on your certification. For example, if 
you certify Heavy HDE to the CO2 standards using only 
steady-state testing, include the statement ``TRACTORS ONLY''. 
Similarly, for engines with one or more approved AECDs for emergency 
vehicle applications under Sec.  1036.115(h)(4), the statement: ``THIS 
ENGINE IS FOR INSTALLATION IN EMERGENCY VEHICLES ONLY''.
    (d) You may add information to the emission control information 
label as follows:
    (1) You may identify other emission standards that the engine meets 
or does not meet. You may add the information about the other emission 
standards to the statement we specify, or you may include it in a 
separate statement.
    (2) You may add other information to ensure that the engine will be 
properly maintained and used.
    (3) You may add appropriate features to prevent counterfeit labels. 
For example, you may include the engine's unique identification number 
on the label.
    (e) You may ask us to approve modified labeling requirements in 
this part if you show that it is necessary or appropriate. We will 
approve your request if your alternate label is consistent with the 
requirements of this part. We may also specify modified labeling 
requirements to be consistent with the intent of 40 CFR part 1037.
    (f) If you obscure the engine label while installing the engine in 
the vehicle such that the label cannot be read during normal 
maintenance, you must place a duplicate label on the vehicle. If others 
install your engine in their vehicles in a way that obscures the engine 
label, we require them to add a duplicate label on the vehicle (see 40 
CFR 1068.105); in that case, give them the number of duplicate labels 
they request and keep the following records for at least five years:
    (1) Written documentation of the request from the vehicle 
manufacturer.
    (2) The number of duplicate labels you send for each engine family 
and the date you sent them.

Sec.  1036.136  Clean Idle sticker.

    (a) Design and produce stickers showing that your engines meet the 
federal Clean Idle standard if you certify engines to the Clean Idle 
NOX standard of Sec.  1036.104(b). The sticker must--
    (1) Meet the requirements of 40 CFR 1068.45 for permanent labels. 
The preferred location for sticker placement is on the driver's side of 
the hood.
    (2) Include one or both of your corporate name and trademark.
    (3) Identify that the engine is qualified to meet the federal Clean 
Idle NOX standard.
    (4) Include a serial number or other method to confirm that 
stickers have been properly applied to vehicles.
    (b) The following provisions apply for placing Clean Idle stickers 
on vehicles with installed engines that have been certified to the 
NOX standard of Sec.  1036.104(b):
    (1) If you install engines in vehicles you produce, you must apply 
a sticker to each vehicle certified to the Clean Idle standard.
    (2) If you ship engines for others to install in vehicles, include 
in your purchasing documentation the manufacturer's request for a 
specific number of labels corresponding to the number of engines 
ordered. Supply the vehicle manufacturer with exactly one sticker for 
each shipped engine certified to the Clean Idle standard. Prepare your 
emission-related installation instructions to ensure that vehicle 
manufacturers meet all application requirements. Keep the following 
records for at least five years:
    (i) Written documentation of the vehicle manufacturer's request for 
stickers.
    (ii) Tracking information for stickers you send and the date you 
sent them.
    (c) The provisions in 40 CFR 1068.101 apply for the Clean Idle 
sticker in the same way that those provisions apply for emission 
control information labels.

Sec.  1036.140  Primary intended service class and engine cycle.

    You must identify a single primary intended service class for each 
engine family that best describes vehicles for which you design and 
market the engine, as follows:
    (a) Divide compression-ignition engines into primary intended 
service classes based on the following engine and vehicle 
characteristics:
    (1) Light HDE includes engines that are not designed for rebuild 
and do not have cylinder liners. Vehicle body types in this group might 
include any heavy-duty vehicle built from a light-duty truck chassis, 
van trucks, multi-stop vans, and some straight trucks with a single 
rear axle. Typical applications would include personal transportation, 
light-load commercial delivery, passenger service, agriculture, and 
construction. The GVWR of these vehicles is normally at or below 19,500 
pounds.
    (2) Medium HDE includes engines that may be designed for rebuild 
and may have cylinder liners. Vehicle body types in this group would 
typically include school buses, straight trucks with single rear axles, 
city tractors, and a variety of special purpose vehicles such as small 
dump trucks, and refuse trucks. Typical applications would include 
commercial short haul and intra-city delivery and pickup. Engines

[[Page 4500]]

in this group are normally used in vehicles whose GVWR ranges from 
19,501 to 33,000 pounds.
    (3) Heavy HDE includes engines that are designed for multiple 
rebuilds and have cylinder liners. Vehicles in this group are normally 
tractors, trucks, straight trucks with dual rear axles, and buses used 
in inter-city, long-haul applications. These vehicles normally exceed 
33,000 pounds GVWR.
    (b) Divide spark-ignition engines into primary intended service 
classes as follows:
    (1) Spark-ignition engines that are best characterized by paragraph 
(a)(1) or (2) of this section are in a separate Spark-ignition HDE 
primary intended service class.
    (2) Spark-ignition engines that are best characterized by paragraph 
(a)(3) of this section are included in the Heavy HDE primary intended 
service class along with compression-ignition engines. Gasoline-fueled 
engines are presumed not to be characterized by paragraph (a)(3) of 
this section; for example, vehicle manufacturers may install some 
number of gasoline-fueled engines in Class 8 trucks without causing the 
engine manufacturer to consider those to be Heavy HDE.
    (c) References to ``spark-ignition standards'' in this part relate 
only to the spark-ignition engines identified in paragraph (b)(1) of 
this section. References to ``compression-ignition standards'' in this 
part relate to compression-ignition engines, to spark-ignition engines 
optionally certified to standards that apply to compression-ignition 
engines, and to all engines identified under paragraph (b)(2) of this 
section as Heavy HDE.

Sec.  1036.150  Interim provisions.

    The provisions in this section apply instead of other provisions in 
this part. This section describes when these interim provisions expire, 
if applicable.
    (a) Transitional ABT credits for NOX emissions. You may generate 
NOX credits from model year 2026 and earlier engines and use 
those as transitional credits for model year 2027 and later engines 
using any of the following methods:
    (1) Discounted credits. Generate discounted credits by certifying 
any model year 2022 through 2026 engine family to meet all the 
requirements that apply under 40 CFR part 86, subpart A. Calculate 
discounted credits for certifying engines in model years 2027 through 
2029 as described in Sec.  1036.705 relative to a NOX 
emission standard of 200 mg/hp[middot]hr and multiply the result by 
0.6. You may not use discounted credits for certifying model year 2030 
and later engines.
    (2) Partial credits. Generate partial credits by certifying any 
model year 2024 through 2026 compression-ignition engine family as 
described in this paragraph (a)(2). You may not use partial credits for 
certifying model year 2033 and later engines. Certify engines for 
partial credits to meet all the requirements that apply under 40 CFR 
part 86, subpart A, with the following adjustments:
    (i) Calculate credits as described in Sec.  1036.705 relative to a 
NOX emission standard of 200 mg/hp[middot]hr using the 
appropriate useful life mileage from 40 CFR 86.004-2. Your declared 
NOX family emission limit applies for the FTP and SET duty 
cycles.
    (ii) Engines must meet a NOX standard when tested over 
the Low Load Cycle as described in Sec.  1036.514. Engines must also 
meet an off-cycle NOX standard as specified in Sec.  
1036.104(a)(3). Calculate the NOX family emission limits for 
the Low Load Cycle and for off-cycle testing as described in Sec.  
1036.104(c)(3) with StdFTPNOx set to 35 mg/hp[middot]hr and 
Std[cycle]NOx set to the values specified in Sec.  
1036.104(a)(2) or (3), respectively. No standard applies for HC, PM, 
and CO emissions for the Low Load Cycle or for off-cycle testing, but 
you must record measured values for those pollutants and include those 
measured values where you report NOX emission results.
    (iii) For engines selected for in-use testing, we may specify that 
you perform testing as described in 40 CFR part 86, subpart T, or as 
described in subpart E of this part.
    (iv) Add the statement ``Partial credit'' to the emission control 
information label.
    (3) Full credits. Generate full credits by certifying any model 
year 2024 through 2026 engine family to meet all the requirements that 
apply under this part. Calculate credits as described in Sec.  1036.705 
relative to a NOX emission standard of 200 mg/hp[middot]hr. 
You may not use full credits for certifying model year 2033 and later 
engines.
    (4) 2026 service class pull-ahead credits. Generate credits from 
diesel-fueled engines under this paragraph (a)(4) by certifying all 
your model year 2026 diesel-fueled Heavy HDE to meet all the 
requirements that apply under this part, with a NOX family 
emission limit for FTP testing at or below 50 mg/hp[middot]hr. 
Calculate credits as described in Sec.  1036.705 relative to a 
NOX emission standard of 200 mg/hp[middot]hr. You may use 
credits generated under this paragraph (a)(4) through model year 2034, 
but not for later model years. Credits generated by Heavy HDE may be 
used for certifying Medium HDE after applying a 10 percent discount 
(multiply credits by 0.9). Engine families using credits generated 
under this paragraph (a)(4) are subject to a NOX FEL cap of 
50 mg/hp[middot]hr for FTP testing.
    (b) Model year 2014 N2O standards. In model year 2014 and earlier, 
manufacturers may show compliance with the N2O standards 
using an engineering analysis. This allowance also applies for later 
families certified using carryover CO2 data from model 2014 
consistent with Sec.  1036.235(d).
    (c) Engine cycle classification. Through model year 2020, engines 
meeting the definition of spark-ignition, but regulated as compression-
ignition engines under Sec.  1036.140, must be certified to the 
requirements applicable to compression-ignition engines under this 
part. Such engines are deemed to be compression-ignition engines for 
purposes of this part. Similarly, through model year 2020, engines 
meeting the definition of compression-ignition, but regulated as Otto-
cycle under 40 CFR part 86 must be certified to the requirements 
applicable to spark-ignition engines under this part. Such engines are 
deemed to be spark-ignition engines for purposes of this part. See 
Sec.  1036.140 for provisions that apply for model year 2021 and later.
    (d) Small manufacturers. The greenhouse gas standards of this part 
apply on a delayed schedule for manufacturers meeting the small 
business criteria specified in 13 CFR 121.201. Apply the small business 
criteria for NAICS code 336310 for engine manufacturers with respect to 
gasoline-fueled engines and 333618 for engine manufacturers with 
respect to other engines; the employee limits apply to the total number 
employees together for affiliated companies. Qualifying small 
manufacturers are not subject to the greenhouse gas emission standards 
in Sec.  1036.108 for engines with a date of manufacture on or after 
November 14, 2011 but before January 1, 2022. In addition, qualifying 
small manufacturers producing engines that run on any fuel other than 
gasoline, E85, or diesel fuel may delay complying with every later 
greenhouse gas standard under this part by one model year. Small 
manufacturers may certify their engines and generate emission credits 
under this part before standards start to apply, but only if they 
certify their entire U.S.-directed production volume within that 
averaging set for that model year. Note that engines not yet subject to 
standards must nevertheless supply fuel maps to vehicle manufacturers 
as described in paragraph (n) of this

[[Page 4501]]

section. Note also that engines produced by small manufacturers are 
subject to criteria pollutant standards.
    (e) Alternate phase-in standards for greenhouse gas emissions. 
Where a manufacturer certifies all of its model year 2013 compression-
ignition engines within a given primary intended service class to the 
applicable alternate standards of this paragraph (e), its compression-
ignition engines within that primary intended service class are subject 
to the standards of this paragraph (e) for model years 2013 through 
2016. This means that once a manufacturer chooses to certify a primary 
intended service class to the standards of this paragraph (e), it is 
not allowed to opt out of these standards.

           Table 1 to Paragraph (e) of Sec.   1036.150--Alternate Phase-In Standards (g/hp[middot]hr)
----------------------------------------------------------------------------------------------------------------
          Vehicle type                Model years          Light HDE          Medium HDE           Heavy HDE
----------------------------------------------------------------------------------------------------------------
Tractors........................  2013-2015.........  NA................  512 g/hp[middot]hr  485 g/
                                  2016 and later \a\  NA................  487 g/hp[middot]hr   hp[middot]hr.
                                                                                              460 g/
                                                                                               hp[middot]hr.
Vocational......................  2013-2015.........  618 g/hp[middot]hr  618 g/hp[middot]hr  577 g/
                                  2016 through 2020   576 g/hp[middot]hr  576 g/hp[middot]hr   hp[middot]hr.
                                   \a\.                                                       555 g/
                                                                                               hp[middot]hr.
----------------------------------------------------------------------------------------------------------------
\a\ Note: these alternate standards for 2016 and later are the same as the otherwise applicable standards for
  2017 through 2020.

    (f) [Reserved]
    (g) Default deterioration factors for greenhouse gas standards. You 
may use default deterioration factors (DFs) without performing your own 
durability emission tests or engineering analysis as follows:
    (1) You may use a default additive DF of 0.0 g/hp[middot]hr for 
CO2 emissions from engines that do not use advanced or off-
cycle technologies. If we determine it to be consistent with good 
engineering judgment, we may allow you to use a default additive DF of 
0.0 g/hp[middot]hr for CO2 emissions from your engines with 
advanced or off-cycle technologies.
    (2) You may use a default additive DF of 0.010 g/hp[middot]hr for 
N2O emissions from any engine through model year 2021, and 
0.020 g/hp[middot]hr for later model years.
    (3) You may use a default additive DF of 0.020 g/hp[middot]hr for 
CH4 emissions from any engine.
    (h) Advanced-technology credits. If you generate CO2 
credits from model year 2020 and earlier engines certified for advanced 
technology, you may multiply these credits by 1.5.
    (i) CO2 credits for low N2O emissions. If you certify your model 
year 2014, 2015, or 2016 engines to an N2O FEL less than 
0.04 g/hp[middot]hr (provided you measure N2O emissions from 
your emission-data engines), you may generate additional CO2 
credits under this paragraph (i). Calculate the additional 
CO2 credits from the following equation instead of the 
equation in Sec.  1036.705:
[GRAPHIC] [TIFF OMITTED] TR24JA23.012

    (j) Alternate standards under 40 CFR part 86. This paragraph (j) 
describes alternate emission standards for loose engines certified 
under 40 CFR 86.1819-14(k)(8). The standards of Sec.  1036.108 do not 
apply for these engines. The standards in this paragraph (j) apply for 
emissions measured with the engine installed in a complete vehicle 
consistent with the provisions of 40 CFR 86.1819-14(k)(8)(vi). The only 
requirements of this part that apply to these engines are those in this 
paragraph (j), Sec. Sec.  1036.115 through 1036.135, 1036.535, and 
1036.540.
    (k) Limited production volume allowance under ABT. You may produce 
a limited number of Heavy HDE that continue to meet the standards that 
applied under 40 CFR 86.007-11 in model years 2027 through 2029. The 
maximum number of engines you may produce under this limited production 
allowance is 5 percent of the annual average of your actual U.S.-
directed production volume of Heavy HDE in model years 2023-2025. 
Engine certification under this paragraph (k) is subject to the 
following conditions and requirements:
    (1) Engines must meet all the standards and other requirements that 
apply under 40 CFR part 86 for model year 2026. Engine must be 
certified in separate engine families that qualify for carryover 
certification as described in Sec.  1036.235(d).
    (2) The NOX FEL must be at or below 200 mg/hp[middot]hr. 
Calculate negative credits as described in Sec.  1036.705 by comparing 
the NOX FEL to the FTP emission standard specified in Sec.  
1036.104(a)(1), with a value for useful life of 650,000 miles. Meet the 
credit reporting and recordkeeping requirements in Sec. Sec.  1036.730 
and 1036.735.
    (3) Label the engine as described in 40 CFR 86.095-35, but include 
the following alternate compliance statement: ``THIS ENGINE CONFORMS TO 
U.S. EPA REGULATIONS FOR MODEL YEAR 2026 ENGINES UNDER 40 CFR 
1036.150(k).''
    (l) Credit adjustment for spark-ignition engines and light heavy-
duty compression-ignition engines. For greenhouse gas emission credits 
generated from model year 2020 and earlier spark-ignition and light 
heavy-duty engines, multiply any banked CO2 credits that you 
carry forward to demonstrate compliance with model year 2021 and later 
standards by 1.36.
    (m) Infrequent regeneration. For model year 2020 and earlier, you 
may invalidate any test interval with respect to CO2 
measurements if an infrequent regeneration event occurs during the test 
interval. Note that Sec.  1036.580 specifies how to apply infrequent 
regeneration adjustment factors for later model years.
    (n) Supplying fuel maps. Engine manufacturers not yet subject to 
standards under Sec.  1036.108 in model year 2021 must supply vehicle 
manufacturers with fuel maps (or powertrain test results) as described 
in Sec.  1036.130 for those engines.
    (o) Engines used in glider vehicles. For purposes of recertifying a 
used engine for installation in a glider vehicle, we may allow you to 
include in an existing certified engine family those engines you modify 
(or otherwise demonstrate) to be identical to engines already covered 
by the certificate. We would base such an approval on our review of any 
appropriate documentation. These engines must have emission control 
information

[[Page 4502]]

labels that accurately describe their status.
    (p) Transition to Phase 2 CO2 standards. If you certify all your 
model year 2020 engines within an averaging set to the model year 2021 
FTP and SET standards and requirements, you may apply the provisions of 
this paragraph (p) for enhanced generation and use of emission credits. 
These provisions apply separately for Medium HDE and Heavy HDE.
    (1) Greenhouse gas emission credits you generate with model year 
2018 through 2024 engines may be used through model year 2030, instead 
of being limited to a five-year credit life as specified in Sec.  
1036.740(d).
    (2) You may certify your model year 2024 through 2026 engines to 
the following alternative standards:

     Table 2 to Paragraph (p)(2) of Sec.   1036.150--Alternative Standards for Model Years 2024 Through 2026
----------------------------------------------------------------------------------------------------------------
                                               Medium heavy-     Heavy heavy-
                 Model years                       duty-            duty-         Medium heavy-    Heavy heavy-
                                                 vocational       vocational     duty- tractor    duty- tractor
----------------------------------------------------------------------------------------------------------------
2024-2026...................................             542              510              467              442
----------------------------------------------------------------------------------------------------------------

    (q) Confirmatory testing of fuel maps defined in Sec.  1036.505(b). 
For model years 2021 and later, where the results from Eq. 1036.235-1 
for a confirmatory test are at or below 2.0%, we will not replace the 
manufacturer's fuel maps.
    (r) Fuel maps for the transition to updated GEM. (1) You may use 
fuel maps from model year 2023 and earlier engines for certifying model 
year 2024 and later engines using carryover provisions in Sec.  
1036.235(d).
    (2) Compliance testing will be based on the GEM version you used to 
generate fuel maps for certification. For example, if you perform a 
selective enforcement audit with respect to fuel maps, use the same GEM 
version that you used to generate fuel maps for certification. 
Similarly, we will use the same GEM version that you used to generate 
fuel maps for certification if we perform confirmatory testing with one 
of your engine families.
    (s) Greenhouse gas compliance testing. Select duty cycles and 
measure emissions to demonstrate compliance with greenhouse gas 
emission standards before model year 2027 as follows:
    (1) For model years 2016 through 2020, measure emissions using the 
FTP duty cycle specified in Sec.  1036.512 and the SET duty cycle 
specified in 40 CFR 86.1362, as applicable.
    (2) The following provisions apply for model years 2021 through 
2026:
    (i) Determine criteria pollutant emissions during any testing used 
to demonstrate compliance with greenhouse gas emission standards; 
however, the duty-cycle standards of Sec.  1036.104 apply for measured 
criteria pollutant emissions only as described in subpart F of this 
part.
    (ii) You may demonstrate compliance with SET-based greenhouse gas 
emission standards in Sec.  1036.108(a)(1) using the SET duty cycle 
specified in 40 CFR 86.1362 if you collect emissions with continuous 
sampling. Integrate the test results by mode to establish separate 
emission rates for each mode (including the transition following each 
mode, as applicable). Apply the CO2 weighting factors 
specified in 40 CFR 86.1362 to calculate a composite emission result.
    (t) Model year 2027 compliance date. The following provisions 
describe when this part 1036 starts to apply for model year 2027 
engines:
    (1) Split model year. Model year 2027 engines you produce before 
December 20, 2026 are subject to the criteria standards and related 
provisions in 40 CFR part 86, subpart A, as described in Sec.  
1036.1(a). Model year 2027 engines you produce on or after December 20, 
2026 are subject to all the provisions of this part.
    (2) Optional early compliance. You may optionally certify model 
year 2027 engines you produce before December 20, 2026 to all the 
provisions of this part.
    (3) Certification. If you certify any model year 2027 engines to 40 
CFR part 86, subpart A, under paragraph (t)(1) of this section, certify 
the engine family by dividing the model year into two partial model 
years. The first portion of the model year starts when it would 
normally start and ends when you no longer produce engines meeting 
standards under 40 CFR part 86, subpart A, on or before December 20, 
2026. The second portion of the model year starts when you begin 
producing engines meeting standards under this part 1036, and ends on 
the day your model year would normally end. The following additional 
provisions apply for model year 2027 if you split the model year as 
described in this paragraph (t):
    (i) You may generate emission credits only with engines that are 
certified under this part 1036.
    (ii) In your production report under Sec.  1036.250(a), identify 
production volumes separately for the two parts of the model year.
    (iii) OBD testing demonstrations apply singularly for the full 
model year.
    (u) Crankcase emissions. The provisions of 40 CFR 86.007-11(c) for 
crankcase emissions continue to apply through model year 2026.
    (v) OBD communication protocol. We may approve the alternative 
communication protocol specified in SAE J1979-2 (incorporated by 
reference in Sec.  1036.810) if the protocol is approved by the 
California Air Resources Board. The alternative protocol would apply 
instead of SAE J1939 and SAE J1979 as specified in 40 CFR 86.010-
18(k)(1). Engines designed to comply with SAE J1979-2 must meet the 
freeze-frame requirements in Sec.  1036.110(b)(8) and in 13 CCR 
1971.1(h)(4.3.2) (incorporated by reference in Sec.  1036.810). This 
paragraph (v) also applies for model year 2026 and earlier engines.
    (w) Greenhouse gas warranty. For model year 2027 and later engines, 
you may ask us to approve the model year 2026 warranty periods 
specified in Sec.  1036.120 for components or systems needed to comply 
with greenhouse gas emission standards if those components or systems 
do not play a role in complying with criteria pollutant standards.
    (x) Powertrain testing for criteria pollutants. You may apply the 
powertrain testing provisions of Sec.  1036.101(b) for demonstrating 
compliance with criteria pollutant emission standards in 40 CFR part 86 
before model year 2027.
    (y) NOX compliance allowance for in-use testing. A NOX 
compliance allowance of 15 mg/hp[middot]hr applies for any in-use 
testing of Medium HDE and Heavy HDE as described in subpart E of this 
part. Add the compliance allowance to the NOX standard that 
applies for each duty cycle and for off-cycle testing, with both field 
testing and laboratory testing. The NOX compliance allowance 
does not apply for the bin 1 off-cycle standard. As an example, for 
manufacturer-run field-testing of a

[[Page 4503]]

Heavy HDE, add the 15 mg/hp[middot]hr compliance allowance and the 5 
mg/hp[middot]hr accuracy margin from Sec.  1036.420 to the 58 mg/
hp[middot]hr[middot]bin 2 off-cycle standard to calculate a 78 mg/
hp[middot]hr NOX standard.
    (z) Alternate family pass criteria for in-use testing. The 
following family pass criteria apply for manufacturer-run in-use 
testing instead of the pass criteria described in Sec.  1036.425 for 
model years 2027 and 2028:
    (1) Start by measuring emissions from five engines using the 
procedures described in subpart E of this part and Sec.  1036.530. If 
four or five engines comply fully with the off-cycle bin standards, the 
engine family passes and you may stop testing.
    (2) If exactly two of the engines tested under paragraph (z)(1) of 
this section do not comply fully with the off-cycle bin standards, test 
five more engines. If these additional engines all comply fully with 
the off-cycle bin standards, the engine family passes and you may stop 
testing.
    (3) If three or more engines tested under paragraphs (z)(1) and (2) 
of this section do not comply fully with the off-cycle bin standards, 
test a total of at least 10 but not more than 15 engines. Calculate the 
arithmetic mean of the bin emissions from all the engine tests as 
specified in Sec.  1036.530(g) for each pollutant. If the mean values 
are at or below the off-cycle bin standards, the engine family passes. 
If the mean value for any pollutant is above an off-cycle bin standard, 
the engine family fails.

Subpart C--Certifying Engine Families

Sec.  1036.201  General requirements for obtaining a certificate of 
conformity.

    (a) You must send us a separate application for a certificate of 
conformity for each engine family. A certificate of conformity is valid 
from the indicated effective date until December 31 of the model year 
for which it is issued.
    (b) The application must contain all the information required by 
this part and must not include false or incomplete statements or 
information (see Sec.  1036.255).
    (c) We may ask you to include less information than we specify in 
this subpart, as long as you maintain all the information required by 
Sec.  1036.250.
    (d) You must use good engineering judgment for all decisions 
related to your application (see 40 CFR 1068.5).
    (e) An authorized representative of your company must approve and 
sign the application.
    (f) See Sec.  1036.255 for provisions describing how we will 
process your application.
    (g) We may require you to deliver your test engines to a facility 
we designate for our testing (see Sec.  1036.235(c)). Alternatively, 
you may choose to deliver another engine that is identical in all 
material respects to the test engine, or another engine that we 
determine can appropriately serve as an emission-data engine for the 
engine family.
    (h) For engines that become new after being placed into service, 
such as rebuilt engines installed in new vehicles, we may specify 
alternate certification provisions consistent with the intent of this 
part. See 40 CFR 1068.120(h) and the definition of ``new motor vehicle 
engine'' in Sec.  1036.801.

Sec.  1036.205  Requirements for an application for certification.

    This section specifies the information that must be in your 
application, unless we ask you to include less information under Sec.  
1036.201(c). We may require you to provide additional information to 
evaluate your application.
    (a) Identify the engine family's primary intended service class and 
describe how that conforms to the specifications in Sec.  1036.140. 
Also, describe the engine family's specifications and other basic 
parameters of the engine's design and emission controls with respect to 
compliance with the requirements of this part. List the fuel type on 
which your engines are designed to operate (for example, gasoline, 
diesel fuel, or natural gas). For engines that can operate on multiple 
fuels, identify whether they are dual-fuel or flexible-fuel engines; 
also identify the range of mixtures for operation on blended fuels, if 
applicable. List each engine configuration in the engine family. List 
the rated power for each engine configuration.
    (b) Explain how the emission control system operates. Describe in 
detail all system components for controlling greenhouse gas and 
criteria pollutant emissions, including all auxiliary emission control 
devices (AECDs) and all fuel-system components you will install on any 
production or test engine. Identify the part number of each component 
you describe. For this paragraph (b), treat as separate AECDs any 
devices that modulate or activate differently from each other. Include 
all the following:
    (1) Give a general overview of the engine, the emission control 
strategies, and all AECDs.
    (2) Describe each AECD's general purpose and function.
    (3) Identify the parameters that each AECD senses (including 
measuring, estimating, calculating, or empirically deriving the 
values). Include engine-based parameters and state whether you simulate 
them during testing with the applicable procedures.
    (4) Describe the purpose for sensing each parameter.
    (5) Identify the location of each sensor the AECD uses.
    (6) Identify the threshold values for the sensed parameters that 
activate the AECD.
    (7) Describe the parameters that the AECD modulates (controls) in 
response to any sensed parameters, including the range of modulation 
for each parameter, the relationship between the sensed parameters and 
the controlled parameters and how the modulation achieves the AECD's 
stated purpose. Use graphs and tables, as necessary.
    (8) Describe each AECD's specific calibration details. This may be 
in the form of data tables, graphical representations, or some other 
description.
    (9) Describe the hierarchy among the AECDs when multiple AECDs 
sense or modulate the same parameter. Describe whether the strategies 
interact in a comparative or additive manner and identify which AECD 
takes precedence in responding, if applicable.
    (10) Explain the extent to which the AECD is included in the 
applicable test procedures specified in subpart F of this part.
    (11) Do the following additional things for AECDs designed to 
protect engines or vehicles:
    (i) Identify any engine and vehicle design limits that make 
protection necessary and describe any damage that would occur without 
the AECD.
    (ii) Describe how each sensed parameter relates to the protected 
components' design limits or those operating conditions that cause the 
need for protection.
    (iii) Describe the relationship between the design limits/
parameters being protected and the parameters sensed or calculated as 
surrogates for those design limits/parameters, if applicable.
    (iv) Describe how the modulation by the AECD prevents engines and 
vehicles from exceeding design limits.
    (v) Explain why it is necessary to estimate any parameters instead 
of measuring them directly and describe how the AECD calculates the 
estimated value, if applicable.
    (vi) Describe how you calibrate the AECD modulation to activate 
only during conditions related to the stated need to protect components 
and only as needed to sufficiently protect those components in a way 
that minimizes the emission impact.

[[Page 4504]]

    (c) Explain in detail how the engine diagnostic system works, 
describing especially the engine conditions (with the corresponding 
diagnostic trouble codes) that cause the malfunction indicator to go 
on. You may ask us to approve conditions under which the diagnostic 
system disregards trouble codes as described in Sec.  1036.110.
    (d) Describe the engines you selected for testing and the reasons 
for selecting them.
    (e) Describe any test equipment and procedures that you used, 
including any special or alternate test procedures you used (see Sec.  
1036.501).
    (f) Describe how you operated the emission-data engine before 
testing, including the duty cycle and the number of engine operating 
hours used to stabilize emission levels. Explain why you selected the 
method of service accumulation. Describe any scheduled maintenance you 
did.
    (g) List the specifications of the test fuel to show that it falls 
within the required ranges we specify in 40 CFR part 1065.
    (h) Identify the engine family's useful life.
    (i) Include the warranty statement and maintenance instructions you 
will give to the ultimate purchaser of each new engine (see Sec. Sec.  
1036.120 and 1036.125).
    (j) Include the emission-related installation instructions you will 
provide if someone else installs your engines in their vehicles (see 
Sec.  1036.130).
    (k) Describe your emission control information label (see Sec.  
1036.135). We may require you to include a copy of the label.
    (l) Identify the duty-cycle emission standards from Sec. Sec.  
1036.104(a) and (b) and 1036.108(a) that apply for the engine family. 
Also identify FELs and FCLs as follows:
    (1) Identify the NOX FEL over the FTP for the engine 
family.
    (2) Identify the CO2 FCLs for the engine family; also 
identify any FELs that apply for CH4 and N2O. The 
actual U.S.-directed production volume of configurations that have 
CO2 emission rates at or below the FCL and CH4 
and N2O emission rates at or below the applicable standards 
or FELs must be at least one percent of your actual (not projected) 
U.S.-directed production volume for the engine family. Identify 
configurations within the family that have emission rates at or below 
the FCL and meet the one percent requirement. For example, if your 
U.S.-directed production volume for the engine family is 10,583 and the 
U.S.-directed production volume for the tested rating is 75 engines, 
then you can comply with this provision by setting your FCL so that one 
more rating with a U.S.-directed production volume of at least 31 
engines meets the FCL. Where applicable, also identify other testable 
configurations required under Sec.  1036.230(f)(2)(ii).
    (m) Identify the engine family's deterioration factors and describe 
how you developed them (see Sec. Sec.  1036.240 and 1036.241). Present 
any test data you used for this. For engines designed to discharge 
crankcase emissions to the ambient atmosphere, use the deterioration 
factors for crankcase emission to determine deteriorated crankcase 
emission levels of NOX, HC, PM, and CO as specified in Sec.  
1036.240(e).
    (n) State that you operated your emission-data engines as described 
in the application (including the test procedures, test parameters, and 
test fuels) to show you meet the requirements of this part.
    (o) Present emission data from all valid tests on an emission-data 
engine to show that you meet emission standards. Note that Sec.  
1036.235 allows you to submit an application in certain cases without 
new emission data. Present emission data as follows:
    (1) For hydrocarbons (such as NMHC or NMHCE), NOX, PM, 
and CO, as applicable, show your engines meet the applicable exhaust 
emission standards we specify in Sec.  1036.104. Show emission figures 
for duty-cycle exhaust emission standards before and after applying 
adjustment factors for regeneration and deterioration factors for each 
engine.
    (2) For CO2, CH4, and N2O, show 
that your engines meet the applicable emission standards we specify in 
Sec.  1036.108. Show emission figures before and after applying 
deterioration factors for each engine. In addition to the composite 
results, show individual measurements for cold-start testing and hot-
start testing over the transient test cycle. For each of these tests, 
also include the corresponding exhaust emission data for criteria 
emissions.
    (3) If we specify more than one grade of any fuel type (for 
example, a summer grade and winter grade of gasoline), you need to 
submit test data only for one grade, unless the regulations of this 
part specify otherwise for your engine.
    (p) State that all the engines in the engine family comply with the 
off-cycle emission standards we specify in Sec.  1036.104 for all 
normal operation and use when tested as specified in Sec.  1036.530. 
Describe any relevant testing, engineering analysis, or other 
information in sufficient detail to support your statement. We may 
direct you to include emission measurements representing typical engine 
in-use operation at a range of ambient conditions. For example, we may 
specify certain transient and steady-state engine operation that is 
typical for the types of vehicles that use your engines. See Sec.  
1036.210.
    (q) We may ask you to send information to confirm that the emission 
data you submitted were from valid tests meeting the requirements of 
this part and 40 CFR part 1065. You must indicate whether there are 
test results from invalid tests or from any other tests of the 
emission-data engine, whether or not they were conducted according to 
the test procedures of subpart F of this part. We may require you to 
report these additional test results.
    (r) Describe all adjustable operating parameters (see Sec.  
1036.115(f)), including production tolerances. For any operating 
parameters that do not qualify as adjustable parameters, include a 
description supporting your conclusion (see 40 CFR 1068.50(c)). Include 
the following in your description of each adjustable parameter:
    (1) For practically adjustable operating parameters, include the 
nominal or recommended setting, the intended practically adjustable 
range, and the limits or stops used to establish adjustable ranges. 
State that the limits, stops, or other means of inhibiting adjustment 
are effective in preventing adjustment of parameters on in-use engines 
to settings outside your intended practically adjustable ranges and 
provide information to support this statement.
    (2) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustment on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
    (s) Provide the information to read, record, and interpret all the 
information broadcast by an engine's onboard computers and ECMs as 
described in Sec.  1036.115(d). State that, upon request, you will give 
us any hardware, software, or tools we would need to do this.
    (t) State whether your certification is limited for certain 
engines. For example, you might certify engines only for use in 
tractors, in emergency vehicles, or in vehicles with hybrid 
powertrains. If this is the case, describe how you will prevent use of 
these engines in vehicles for which they are not certified.
    (u) Unconditionally certify that all the engines in the engine 
family comply with the requirements of this part, other referenced 
parts of the CFR, and the

[[Page 4505]]

Clean Air Act. Note that Sec.  1036.235 specifies which engines to test 
to show that engines in the entire family comply with the requirements 
of this part.
    (v) Include good-faith estimates of nationwide production volumes. 
Include a justification for the estimated production volumes if they 
are substantially different than actual production volumes in earlier 
years for similar models.
    (w) Include the information required by other subparts of this 
part. For example, include the information required by Sec.  1036.725 
if you participate in the ABT program.
    (x) Include other applicable information, such as information 
specified in this part or 40 CFR part 1068 related to requests for 
exemptions.
    (y) Name an agent for service located in the United States. Service 
on this agent constitutes service on you or any of your officers or 
employees for any action by EPA or otherwise by the United States 
related to the requirements of this part.
    (z) For imported engines, identify the following:
    (1) Describe your normal practice for importing engines. For 
example, this may include identifying the names and addresses of anyone 
you have authorized to import your engines. Engines imported by 
nonauthorized agents are not covered by your certificate.
    (2) The location of a test facility in the United States where you 
can test your engines if we select them for testing under a selective 
enforcement audit, as specified in 40 CFR part 1068, subpart E.
    (aa) Include information needed to certify vehicles to greenhouse 
gas standards under 40 CFR part 1037 as described in Sec.  1036.505.

Sec.  1036.210  Preliminary approval before certification.

    If you send us information before you finish the application, we 
may review it and make any appropriate determinations, especially for 
questions related to engine family definitions, auxiliary emission 
control devices, adjustable parameters, deterioration factors, testing 
for service accumulation, and maintenance. Decisions made under this 
section are considered to be preliminary approval, subject to final 
review and approval. We will generally not reverse a decision where we 
have given you preliminary approval, unless we find new information 
supporting a different decision. If you request preliminary approval 
related to the upcoming model year or the model year after that, we 
will make best-efforts to make the appropriate determinations as soon 
as practicable. We will generally not provide preliminary approval 
related to a future model year more than two years ahead of time.

Sec.  1036.225  Amending applications for certification.

    Before we issue you a certificate of conformity, you may amend your 
application to include new or modified engine configurations, subject 
to the provisions of this section. After we have issued your 
certificate of conformity, you may send us an amended application any 
time before the end of the model year requesting that we include new or 
modified engine configurations within the scope of the certificate, 
subject to the provisions of this section. You must also amend your 
application if any changes occur with respect to any information that 
is included or should be included in your application.
    (a) You must amend your application before you take any of the 
following actions:
    (1) Add an engine configuration to an engine family. In this case, 
the engine configuration added must be consistent with other engine 
configurations in the engine family with respect to the design aspects 
listed in Sec.  1036.230.
    (2) Change an engine configuration already included in an engine 
family in a way that may affect emissions, or change any of the 
components you described in your application for certification. This 
includes production and design changes that may affect emissions any 
time during the engine's lifetime.
    (3) Modify an FEL or FCL for an engine family as described in 
paragraph (f) of this section.
    (b) To amend your application for certification, send the relevant 
information to the Designated Compliance Officer.
    (1) Describe in detail the addition or change in the engine model 
or configuration you intend to make.
    (2) Include engineering evaluations or data showing that the 
amended engine family complies with all applicable requirements. You 
may do this by showing that the original emission-data engine is still 
appropriate for showing that the amended family complies with all 
applicable requirements.
    (3) If the original emission-data engine for the engine family is 
not appropriate to show compliance for the new or modified engine 
configuration, include new test data showing that the new or modified 
engine configuration meets the requirements of this part.
    (4) Include any other information needed to make your application 
correct and complete.
    (c) We may ask for more test data or engineering evaluations. You 
must give us these within 30 days after we request them.
    (d) For engine families already covered by a certificate of 
conformity, we will determine whether the existing certificate of 
conformity covers your newly added or modified engine. You may ask for 
a hearing if we deny your request (see Sec.  1036.820).
    (e) The amended application applies starting with the date you 
submit the amended application, as follows:
    (1) For engine families already covered by a certificate of 
conformity, you may start producing a new or modified engine 
configuration any time after you send us your amended application and 
before we make a decision under paragraph (d) of this section. However, 
if we determine that the affected engines do not meet applicable 
requirements in this part, we will notify you to cease production of 
the engines and may require you to recall the engines at no expense to 
the owner. Choosing to produce engines under this paragraph (e) is 
deemed to be consent to recall all engines that we determine do not 
meet applicable emission standards or other requirements in this part 
and to remedy the nonconformity at no expense to the owner. If you do 
not provide information required under paragraph (c) of this section 
within 30 days after we request it, you must stop producing the new or 
modified engines.
    (2) [Reserved]
    (f) You may ask us to approve a change to your FEL in certain cases 
after the start of production, but before the end of the model year. If 
you change an FEL for CO2, your FCL for CO2 is 
automatically set to your new FEL divided by 1.03. The changed FEL may 
not apply to engines you have already introduced into U.S. commerce, 
except as described in this paragraph (f). You may ask us to approve a 
change to your FEL in the following cases:
    (1) You may ask to raise your FEL for your engine family at any 
time. In your request, you must show that you will still be able to 
meet the emission standards as specified in subparts B and H of this 
part. Use the appropriate FELs/FCLs with corresponding production 
volumes to calculate emission credits for the model year, as described 
in subpart H of this part.
    (2) You may ask to lower the FEL for your engine family only if you 
have test data from production engines showing that emissions are below 
the proposed

[[Page 4506]]

lower FEL (or below the proposed FCL for CO2). The lower 
FEL/FCL applies only to engines you produce after we approve the new 
FEL/FCL. Use the appropriate FEL/FCL with corresponding production 
volumes to calculate emission credits for the model year, as described 
in subpart H of this part.
    (g) You may produce engines or modify in-use engines as described 
in your amended application for certification and consider those 
engines to be in a certified configuration. Modifying a new or in-use 
engine to be in a certified configuration does not violate the 
tampering prohibition of 40 CFR 1068.101(b)(1), as long as this does 
not involve changing to a certified configuration with a higher family 
emission limit.

Sec.  1036.230  Selecting engine families.

    (a) For purposes of certification to the standards of this part, 
divide your product line into families of engines that are expected to 
have similar characteristics for criteria emissions throughout the 
useful life as described in this section. Your engine family is limited 
to a single model year.
    (b) Group engines in the same engine family if they are the same in 
all the following design aspects:
    (1) The combustion cycle and fuel. See paragraph (g) of this 
section for special provisions that apply for dual-fuel and flexible-
fuel engines.
    (2) The cooling system (water-cooled vs. air-cooled).
    (3) Method of air aspiration, including the location of intake and 
exhaust valves or ports and the method of intake-air cooling, if 
applicable.
    (4) The arrangement and composition of catalytic converters and 
other aftertreatment devices.
    (5) Cylinder arrangement (such as in-line vs. vee configurations) 
and bore center-to-center dimensions.
    (6) Method of control for engine operation other than governing 
(i.e., mechanical or electronic).
    (7) The numerical level of the applicable criteria emission 
standards. For example, an engine family may not include engines 
certified to different family emission limits for criteria emission 
standards, though you may change family emission limits without 
recertifying as specified in Sec.  1036.225(f).
    (c) You may subdivide a group of engines that is identical under 
paragraph (b) of this section into different engine families if you 
show the expected criteria emission characteristics are different 
during the useful life.
    (d) In unusual circumstances, you may group engines that are not 
identical with respect to the design aspects listed in paragraph (b) of 
this section in the same engine family if you show that their criteria 
emission characteristics during the useful life will be similar.
    (e) Engine configurations certified as hybrid engines or hybrid 
powertrains may not be included in an engine family with engines that 
have nonhybrid powertrains. Note that this does not prevent you from 
including engines in a nonhybrid family if they are used in hybrid 
vehicles, as long as you certify them based on engine testing.
    (f) You must certify your engines to the greenhouse gas standards 
of Sec.  1036.108 using the same engine families you use for criteria 
pollutants. The following additional provisions apply with respect to 
demonstrating compliance with the standards in Sec.  1036.108:
    (1) You may subdivide an engine family into subfamilies that have a 
different FCL for CO2 emissions. These subfamilies do not 
apply for demonstrating compliance with criteria standards in Sec.  
1036.104.
    (2) If you certify engines in the family for use as both vocational 
and tractor engines, you must split your family into two separate 
subfamilies.
    (i) Calculate emission credits relative to the vocational engine 
standard for the number of engines sold into vocational applications 
and relative to the tractor engine standard for the number of engines 
sold into non-vocational tractor applications. You may assign the 
numbers and configurations of engines within the respective subfamilies 
at any time before submitting the report required by Sec.  1036.730. If 
the family participates in averaging, banking, or trading, you must 
identify the type of vehicle in which each engine is installed; we may 
alternatively allow you to use statistical methods to determine this 
for a fraction of your engines. Keep records to document this 
determination.
    (ii) If you restrict use of the test configuration for your split 
family only to tractors, or only to vocational vehicles, you must 
identify a second testable configuration for the other type of vehicle 
(or an unrestricted configuration). Identify this configuration in your 
application for certification. The FCL for the engine family applies 
for this configuration as well as the primary test configuration.
    (3) If you certify both engine fuel maps and powertrain fuel maps 
for an engine family, you may split the engine family into two separate 
subfamilies. Indicate this in your application for certification, and 
identify whether one or both of these sets of fuel maps applies for 
each group of engines. If you do not split your family, all engines 
within the family must conform to the engine fuel maps, including any 
engines for with the powertrain maps also apply.
    (4) If you certify in separate engine families engines that could 
have been certified in vocational and tractor engine subfamilies in the 
same engine family, count the two families as one family for purposes 
of determining your obligations with respect to the OBD requirements 
and in-use testing requirements. Indicate in the applications for 
certification that the two engine families are covered by this 
paragraph (f)(4).
    (5) Except as described in this paragraph (f), engine 
configurations within an engine family must use equivalent greenhouse 
gas emission controls. Unless we approve it, you may not produce 
nontested configurations without the same emission control hardware 
included on the tested configuration. We will only approve it if you 
demonstrate that the exclusion of the hardware does not increase 
greenhouse gas emissions.
    (g) You may certify dual-fuel or flexible-fuel engines in a single 
engine family. You may include dedicated-fuel versions of this same 
engine model in the same engine family, as long as they are identical 
to the engine configuration with respect to that fuel type for the 
dual-fuel or flexible-fuel version of the engine. For example, if you 
produce an engine that can alternately run on gasoline and natural gas, 
you can include the gasoline-only and natural gas-only versions of the 
engine in the same engine family as the dual-fuel engine if engine 
operation on each fuel type is identical with or without installation 
of components for operating on the other fuel.

Sec.  1036.235  Testing requirements for certification.

    This section describes the emission testing you must perform to 
show compliance with the emission standards in Sec. Sec.  1036.104 and 
1036.108.
    (a) Select and configure one or two emission-data engines from each 
engine family as follows:
    (1) You may use one engine for criteria pollutant testing and a 
different engine for greenhouse gas emission testing, or you may use 
the same engine for all testing.
    (2) For criteria pollutant emission testing, select the engine 
configuration with the highest volume of fuel injected per cylinder per 
combustion cycle at the point of maximum torque--unless good

[[Page 4507]]

engineering judgment indicates that a different engine configuration is 
more likely to exceed (or have emissions nearer to) an applicable 
emission standard or FEL. If two or more engines have the same fueling 
rate at maximum torque, select the one with the highest fueling rate at 
rated speed. In making this selection, consider all factors expected to 
affect emission-control performance and compliance with the standards, 
including emission levels of all exhaust constituents, especially 
NOX and PM. To the extent we allow it for establishing 
deterioration factors, select for testing those engine components or 
subsystems whose deterioration best represents the deterioration of in-
use engines.
    (3) For greenhouse gas emission testing, the standards of this part 
apply only with respect to emissions measured from the tested 
configuration and other configurations identified in Sec.  
1036.205(l)(2). Note that configurations identified in Sec.  
1036.205(l)(2) are considered to be ``tested configurations'' whether 
or not you test them for certification. However, you must apply the 
same (or equivalent) emission controls to all other engine 
configurations in the engine family. In other contexts, the tested 
configuration is sometimes referred to as the ``parent configuration'', 
although the terms are not synonymous.
    (b) Test your emission-data engines using the procedures and 
equipment specified in subpart F of this part. In the case of dual-fuel 
and flexible-fuel engines, measure emissions when operating with each 
type of fuel for which you intend to certify the engine.
    (1) For criteria pollutant emission testing, measure 
NOX, PM, CO, and NMHC emissions using each duty cycle 
specified in Sec.  1036.104.
    (2) For greenhouse gas emission testing, measure CO2, 
CH4, and N2O emissions; the following provisions 
apply regarding test cycles for demonstrating compliance with tractor 
and vocational standards:
    (i) If you are certifying the engine for use in tractors, you must 
measure CO2 emissions using the SET duty cycle specified in 
Sec.  1036.510, taking into account the interim provisions in Sec.  
1036.150(s), and measure CH4 and N2O emissions 
using the FTP transient cycle.
    (ii) If you are certifying the engine for use in vocational 
applications, you must measure CO2, CH4, and 
N2O emissions using the appropriate FTP transient duty 
cycle, including cold-start and hot-start testing as specified in Sec.  
1036.512.
    (iii) You may certify your engine family for both tractor and 
vocational use by submitting CO2 emission data and 
specifying FCLs for both SET and FTP transient duty cycles.
    (iv) Some of your engines certified for use in tractors may also be 
used in vocational vehicles, and some of your engines certified for use 
in vocational may be used in tractors. However, you may not knowingly 
circumvent the intent of this part (to reduce in-use emissions of 
CO2) by certifying engines designed for tractors or 
vocational vehicles (and rarely used in the other application) to the 
wrong cycle. For example, we would generally not allow you to certify 
all your engines to the SET duty cycle without certifying any to the 
FTP transient cycle.
    (c) We may perform confirmatory testing by measuring emissions from 
any of your emission-data engines. If your certification includes 
powertrain testing as specified in Sec.  1036.630, this paragraph (c) 
also applies for the powertrain test results.
    (1) We may decide to do the testing at your plant or any other 
facility. If we do this, you must deliver the engine to a test facility 
we designate. The engine you provide must include appropriate 
manifolds, aftertreatment devices, ECMs, and other emission-related 
components not normally attached directly to the engine block. If we do 
the testing at your plant, you must schedule it as soon as possible and 
make available the instruments, personnel, and equipment we need.
    (2) If we measure emissions on your engine, the results of that 
testing become the official emission results for the engine as 
specified in this paragraph (c). Unless we later invalidate these data, 
we may decide not to consider your data in determining if your engine 
family meets applicable requirements in this part.
    (3) Before we test one of your engines, we may set its adjustable 
parameters to any point within the practically adjustable ranges (see 
Sec.  1036.115(f)).
    (4) Before we test one of your engines, we may calibrate it within 
normal production tolerances for anything we do not consider an 
adjustable parameter. For example, we may calibrate it within normal 
production tolerances for an engine parameter that is subject to 
production variability because it is adjustable during production, but 
is not considered an adjustable parameter because it is permanently 
sealed. For parameters that relate to a level of performance that is 
itself subject to a specified range (such as maximum power output), we 
will generally perform any calibration under this paragraph (c)(4) in a 
way that keeps performance within the specified range.
    (5) For greenhouse gas emission testing, we may use our emission 
test results for steady-state, idle, cycle-average and powertrain fuel 
maps defined in Sec.  1036.505(b) as the official emission results. We 
will not replace individual points from your fuel map.
    (i) We will determine fuel masses, mfuel[cycle], and 
mean idle fuel mass flow rates, mifuelidle, if applicable, 
using both direct and indirect measurement. We will determine the 
result for each test point based on carbon balance error verification 
as described in Sec.  1036.535(g)(3)(i) and (ii).
    (ii) We will perform this comparison using the weighted results 
from GEM, using vehicles that are appropriate for the engine under 
test. For example, we may select vehicles that the engine went into for 
the previous model year.
    (iii) If you supply cycle-average engine fuel maps for the highway 
cruise cycles instead of generating a steady-state fuel map for these 
cycles, we may perform a confirmatory test of your engine fuel maps for 
the highway cruise cycles by either of the following methods:
    (A) Directly measuring the highway cruise cycle-average fuel maps.
    (B) Measuring a steady-state fuel map as described in this 
paragraph (c)(5) and using it in GEM to create our own cycle-average 
engine fuel maps for the highway cruise cycles.
    (iv) We will replace fuel maps as a result of confirmatory testing 
as follows:
    (A) Weight individual duty cycle results using the vehicle 
categories determined in paragraph (c)(5)(i) of this section and 
respective weighting factors in 40 CFR 1037.510(c) to determine a 
composite CO2 emission value for each vehicle configuration; 
then repeat the process for all the unique vehicle configurations used 
to generate the manufacturer's fuel maps.
    (B) The average percent difference between fuel maps is calculated 
using the following equation:

[[Page 4508]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.013

Where:

i = an indexing variable that represents one individual weighted 
duty cycle result for a vehicle configuration.
N = total number of vehicle configurations.
eCO2compEPAi = unrounded composite mass of CO2 
emissions in g/ton-mile for vehicle configuration i for the EPA 
test.
eCO2compManui = unrounded composite mass of 
CO2 emissions in g/ton-mile for vehicle configuration i 
for the manufacturer-declared map.

    (C) Where the unrounded average percent difference between our 
composite weighted fuel map and the manufacturer's is at or below 0%, 
we will not replace the manufacturer's maps, and we will consider an 
individual engine to have passed the fuel map.
    (6) We may perform confirmatory testing with an engine dynamometer 
to simulate normal engine operation to determine whether your emission-
data engine meets off-cycle emission standards. The accuracy margins 
described in Sec.  1036.420(a) do not apply for such laboratory 
testing.
    (d) You may ask to use carryover emission data from a previous 
model year instead of doing new tests, but only if all the following 
are true:
    (1) The engine family from the previous model year differs from the 
current engine family only with respect to model year, items identified 
in Sec.  1036.225(a), or other characteristics unrelated to emissions. 
We may waive this criterion for differences we determine not to be 
relevant.
    (2) The emission-data engine from the previous model year remains 
the appropriate emission-data engine under paragraph (a) of this 
section.
    (3) The data show that the emission-data engine would meet all the 
requirements that apply to the engine family covered by the application 
for certification.
    (e) We may require you to test a second engine of the same 
configuration in addition to the engines tested under paragraph (a) of 
this section.
    (f) If you use an alternate test procedure under 40 CFR 1065.10 and 
later testing shows that such testing does not produce results that are 
equivalent to the procedures specified in subpart F of this part, we 
may reject data you generated using the alternate procedure.
    (g) We may evaluate or test your engines to determine whether they 
have a defeat device before or after we issue a certificate of 
conformity. We may test or require testing on any vehicle or engine at 
a designated location, using driving cycles and conditions that may 
reasonably be expected in normal operation and use to investigate a 
potential defeat device. If we designate an engine's AECD as a possible 
defeat device, you must demonstrate to us that that the AECD does not 
reduce emission control effectiveness when the engine operates under 
conditions that may reasonably be expected in normal operation and use, 
unless one of the specific exceptions described in Sec.  1036.115(h) 
applies.

Sec.  1036.240  Demonstrating compliance with criteria pollutant 
emission standards.

    (a) For purposes of certification, your engine family is considered 
in compliance with the duty-cycle emission standards in Sec.  
1036.104(a)(1) and (2) if all emission-data engines representing that 
family have test results showing official emission results and 
deteriorated emission levels at or below these standards (including all 
corrections and adjustments). This also applies for all test points for 
emission-data engines within the family used to establish deterioration 
factors. Note that your FELs are considered to be the applicable 
emission standards with which you must comply if you participate in the 
ABT program in subpart H of this part. Use good engineering judgment to 
demonstrate compliance with off-cycle standards throughout the useful 
life.
    (b) Your engine family is deemed not to comply if any emission-data 
engine representing that family has test results showing an official 
emission result or a deteriorated emission level for any pollutant that 
is above an applicable emission standard (including all corrections and 
adjustments). Similarly, your engine family is deemed not to comply if 
any emission-data engine representing that family has test results 
showing any emission level above the applicable off-cycle emission 
standard for any pollutant. This also applies for all test points for 
emission-data engines within the family used to establish deterioration 
factors.
    (c) To compare emission levels from the emission-data engine with 
the applicable duty-cycle emission standards, apply deterioration 
factors to the measured emission levels for each pollutant. Section 
1036.245 specifies how to test engines and engine components to develop 
deterioration factors that represent the deterioration expected in 
emissions over your engines' useful life. Section 1036.246 describes 
how to confirm or modify deterioration factors based on in-use 
verification testing. Your deterioration factors must take into account 
any available data from other in-use testing with similar engines. 
Small manufacturers may use assigned deterioration factors that we 
establish. Apply deterioration factors as follows:
    (1) Additive deterioration factor for exhaust emissions. Except as 
specified in paragraph (c)(2) of this section, use an additive 
deterioration factor for exhaust emissions. An additive deterioration 
factor is the difference between exhaust emissions at the end of the 
useful life and exhaust emissions at the low-hour test point. In these 
cases, adjust the official emission results for each tested engine at 
the selected test point by adding the factor to the measured emissions. 
If the factor is less than zero, use zero. Additive deterioration 
factors must be specified to one more decimal place than the applicable 
standard.
    (2) Multiplicative deterioration factor for exhaust emissions. Use 
a multiplicative deterioration factor if good engineering judgment 
calls for the deterioration factor for a pollutant to be the ratio of 
exhaust emissions at the end of the useful life to exhaust emissions at 
the low-hour test point. For example, if you use aftertreatment 
technology that controls emissions of a pollutant proportionally to 
engine-out emissions, it is often appropriate to use a multiplicative 
deterioration factor. Adjust the official emission results for each 
tested engine at the selected test point by multiplying the measured 
emissions by the deterioration factor. If the factor is less than one, 
use one. A multiplicative deterioration factor may not be appropriate 
in cases where testing variability is significantly greater than 
engine-to-engine variability. Multiplicative deterioration factors must

[[Page 4509]]

be specified to one more significant figure than the applicable 
standard.
    (3) Sawtooth and other nonlinear deterioration patterns. The 
deterioration factors described in paragraphs (c)(1) and (2) of this 
section assume that the highest useful life emissions occur either at 
the end of useful life or at the low-hour test point. The provisions of 
this paragraph (c)(3) apply where good engineering judgment indicates 
that the highest useful life emissions will occur between these two 
points. For example, emissions may increase with service accumulation 
until a certain maintenance step is performed, then return to the low-
hour emission levels and begin increasing again. Such a pattern may 
occur with battery-based electric hybrid engines. Base deterioration 
factors for engines with such emission patterns on the difference 
between (or ratio of) the point at which the highest emissions occur 
and the low-hour test point. Note that this applies for maintenance-
related deterioration only where we allow such critical emission-
related maintenance.
    (4) Dual-fuel and flexible-fuel engines. In the case of dual-fuel 
and flexible-fuel engines, apply deterioration factors separately for 
each fuel type. You may accumulate service hours on a single emission-
data engine using the type of fuel or the fuel mixture expected to have 
the highest combustion and exhaust temperatures; you may ask us to 
approve a different fuel mixture if you demonstrate that a different 
criterion is more appropriate.
    (5) Deterioration factor for crankcase emissions. If engines route 
crankcase emissions into the ambient atmosphere or into the exhaust 
downstream of exhaust aftertreatment, you must account for any increase 
in crankcase emissions throughout the useful life using good 
engineering judgment. Use separate deterioration factors for crankcase 
emissions of each pollutant (either multiplicative or additive).
    (d) Determine the official emission result for each pollutant to at 
least one more decimal place than the applicable standard. Apply the 
deterioration factor to the official emission result, as described in 
paragraph (c) of this section, then round the adjusted figure to the 
same number of decimal places as the emission standard. Compare the 
rounded emission levels to the emission standard for each emission-data 
engine.
    (e) You do not need deterioration factors to demonstrate compliance 
with off-cycle standards. However, for engines designed to discharge 
crankcase emissions to the ambient atmosphere, you must determine 
deteriorated emission levels to represent crankcase emissions at the 
end of useful life for purposes of demonstrating compliance with off-
cycle emission standards. Determine an official brake-specific 
crankcase emission result for each pollutant based on operation over 
the FTP duty cycle. Also determine an official crankcase emission 
result for NOX in g/hr from the idle portion of any of the 
duty cycles specified in subpart F of this part. Apply crankcase 
deterioration factors to all these official crankcase emission results 
as described in paragraph (c) of this section, then round the adjusted 
figures to the same number of decimal places as the off-cycle emission 
standards in Sec.  1036.104(a)(3).

Sec.  1036.241  Demonstrating compliance with greenhouse gas emission 
standards.

    (a) For purposes of certification, your engine family is considered 
in compliance with the emission standards in Sec.  1036.108 if all 
emission-data engines representing the tested configuration of that 
engine family have test results showing official emission results and 
deteriorated emission levels at or below the standards. Note that your 
FCLs are considered to be the applicable emission standards with which 
you must comply for certification.
    (b) Your engine family is deemed not to comply if any emission-data 
engine representing the tested configuration of that engine family has 
test results showing an official emission result or a deteriorated 
emission level for any pollutant that is above an applicable emission 
standard (generally the FCL). Note that you may increase your FCL if 
any certification test results exceed your initial FCL.
    (c) Apply deterioration factors to the measured emission levels for 
each pollutant to show compliance with the applicable emission 
standards. Your deterioration factors must take into account any 
available data from in-use testing with similar engines. Apply 
deterioration factors as follows:
    (1) Additive deterioration factor for greenhouse gas emissions. 
Except as specified in paragraphs (c)(2) and (3) of this section, use 
an additive deterioration factor for exhaust emissions. An additive 
deterioration factor is the difference between the highest exhaust 
emissions (typically at the end of the useful life) and exhaust 
emissions at the low-hour test point. In these cases, adjust the 
official emission results for each tested engine at the selected test 
point by adding the factor to the measured emissions. If the factor is 
less than zero, use zero. Additive deterioration factors must be 
specified to one more decimal place than the applicable standard.
    (2) Multiplicative deterioration factor for greenhouse gas 
emissions. Use a multiplicative deterioration factor for a pollutant if 
good engineering judgment calls for the deterioration factor for that 
pollutant to be the ratio of the highest exhaust emissions (typically 
at the end of the useful life) to exhaust emissions at the low-hour 
test point. Adjust the official emission results for each tested engine 
at the selected test point by multiplying the measured emissions by the 
deterioration factor. If the factor is less than one, use one. A 
multiplicative deterioration factor may not be appropriate in cases 
where testing variability is significantly greater than engine-to-
engine variability. Multiplicative deterioration factors must be 
specified to one more significant figure than the applicable standard.
    (3) Sawtooth and other nonlinear deterioration patterns. The 
deterioration factors described in paragraphs (c)(1) and (2) of this 
section assume that the highest useful life emissions occur either at 
the end of useful life or at the low-hour test point. The provisions of 
this paragraph (c)(3) apply where good engineering judgment indicates 
that the highest useful life emissions will occur between these two 
points. For example, emissions may increase with service accumulation 
until a certain maintenance step is performed, then return to the low-
hour emission levels and begin increasing again. Such a pattern may 
occur with battery-based electric hybrid engines. Base deterioration 
factors for engines with such emission patterns on the difference 
between (or ratio of) the point at which the highest emissions occur 
and the low-hour test point. Note that this applies for maintenance-
related deterioration only where we allow such critical emission-
related maintenance.
    (4) Dual-fuel and flexible-fuel engines. In the case of dual-fuel 
and flexible-fuel engines, apply deterioration factors separately for 
each fuel type by measuring emissions with each fuel type at each test 
point. You may accumulate service hours on a single emission-data 
engine using the type of fuel or the fuel mixture expected to have the 
highest combustion and exhaust temperatures; you may ask us to approve 
a different fuel mixture if you demonstrate that a different criterion 
is more appropriate.
    (d) Calculate emission data using measurements to at least one more 
decimal place than the applicable standard. Apply the deterioration 
factor to the official emission result, as described in paragraph (c) 
of this

[[Page 4510]]

section, then round the adjusted figure to the same number of decimal 
places as the emission standard. Compare the rounded emission levels to 
the emission standard for each emission-data engine.
    (e) If you identify more than one configuration in Sec.  
1036.205(l)(2), we may test (or require you to test) any of the 
identified configurations. We may also require you to provide an 
engineering analysis that demonstrates that untested configurations 
listed in Sec.  1036.205(l)(2) comply with their FCL.

Sec.  1036.245  Deterioration factors for exhaust emission standards.

    This section describes how to determine deterioration factors, 
either with pre-existing test data or with new emission measurements. 
Apply these deterioration factors to determine whether your engines 
will meet the duty-cycle emission standards throughout the useful life 
as described in Sec.  1036.240. The provisions of this section and the 
verification provisions of Sec.  1036.246 apply for all engine families 
starting in model year 2027; you may optionally use these provisions to 
determine and verify deterioration factors for earlier model years.
    (a) You may ask us to approve deterioration factors for an engine 
family based on an engineering analysis of emission measurements from 
similar highway or nonroad engines if you have already given us these 
data for certifying the other engines in the same or earlier model 
years. Use good engineering judgment to decide whether the two engines 
are similar. We will approve your request if you show us that the 
emission measurements from other engines reasonably represent in-use 
deterioration for the engine family for which you have not yet 
determined deterioration factors.
    (b) [Reserved]
    (c) If you are unable to determine deterioration factors for an 
engine family under paragraph (a) of this section, select engines, 
subsystems, or components for testing. Determine deterioration factors 
based on service accumulation and related testing to represent the 
deterioration expected from in-use engines over the useful life, 
including crankcase emissions. You may perform maintenance on emission-
data engines as described in Sec.  1036.125 and 40 CFR part 1065, 
subpart E. Use good engineering judgment for all aspects of the effort 
to establish deterioration factors under this paragraph (c). Send us 
your test plan for our preliminary approval under Sec.  1036.210. You 
may apply deterioration factors based on testing under this paragraph 
(c) to multiple engine families, consistent with the provisions in 
paragraph (a) of this section. Determine deterioration factors based on 
a combination of minimum required engine dynamometer aging hours and 
accelerated bench-aged aftertreatment as follows:
    (1) Select an emission-data engine and aftertreatment devices and 
systems that can be assembled into a certified configuration to 
represent the engine family. Stabilize the engine and aftertreatment 
devices and systems, together or separately, to prepare for emission 
measurements. Perform low-hour emission measurement once the engine has 
operated with aftertreatment long enough to stabilize the emission 
control. Measure emissions of all regulated pollutants while the engine 
operates over all applicable duty cycles on an engine dynamometer as 
described in subpart F of this part.
    (2) Perform additional service accumulation as described in 
paragraph (c)(3) of this section on an engine dynamometer meeting at 
least the following minimum specifications:

 Table 1 to Paragraph (c)(2) of Sec.   1036.245--Minimum Required Engine
        Dynamometer Aging Hours by Primary Intended Service Class
------------------------------------------------------------------------
                                                          Minimum engine
             Primary intended service class                 dynamometer
                                                               hours
------------------------------------------------------------------------
Spark-ignition HDE......................................             300
Light HDE...............................................           1,250
Medium HDE..............................................           1,500
Heavy HDE...............................................           1,500
------------------------------------------------------------------------

    (3) Perform service accumulation in the laboratory by operating the 
engine repeatedly over one of the following test sequences, or a 
different test sequence that we approve in advance:
    (i) Use duty-cycle sequence 1 for operating any engine on an engine 
dynamometer, as follows:
    (A) Operate at idle for 2 hours.
    (B) Operate for 105  1 hours over a repeat sequence of 
one FTP followed by one RMC.
    (C) Operate over one LLC.
    (D) Operate at idle for 2 hours.
    (E) Shut down the engine for cooldown to ambient temperature.
    (ii) Duty-cycle sequence 2 is based on operating over the LLC and 
the vehicle-based duty cycles from 40 CFR part 1037. Select the vehicle 
subcategory and vehicle configuration from Sec.  1036.540 with the 
highest reference cycle work for each vehicle-based duty cycle. Operate 
the engine as follows for duty-cycle sequence 2:
    (A) Operate at idle for 2 hours.
    (B) Operate for 105  1 hours over a repeat sequence of 
one Heavy-duty Transient Test Cycle, then one 55 mi/hr highway cruise 
cycle, and then one 65 mi/hr highway cruise cycle.
    (C) Operate over one LLC.
    (D) Operate at idle for 2 hours.
    (E) Shut down the engine for cooldown to ambient temperature.
    (4) Perform all the emission measurements described in paragraph 
(c)(1) of this section when the engine has reached the minimum service 
accumulation specified in paragraph (c)(2) of this section, and again 
after you finish service accumulation in the laboratory if your service 
accumulation exceeds the values specified in paragraph (c)(2) of this 
section.
    (5) Determine the deterioration factor based on a combination of 
actual and simulated service accumulation represented by a number of 
hours of engine operation calculated using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.014

Where:

UL = useful life mileage from Sec.  1036.104(e).
k = 1.15 for Heavy HDE and 1.0 for all other primary intended 
service classes.
vagingcycle = average speed of aging cycle in paragraph 
(c)(3) of this section. Use 40.26 mi/hr for duty-cycle sequence 1 
and 44.48 mi/hr for duty-cycle sequence 2.

Example for Heavy HDE for Duty-Cycle Sequence 1:

UL = 650,000 miles
k = 1.15
vagingcycle = 40.26 mi/hr
[GRAPHIC] [TIFF OMITTED] TR24JA23.015

ttotal = 18,567 hr

    (6) Perform accelerated bench aging of aftertreatment devices to 
represent normal engine operation over the useful life using the 
service accumulation hours determined in paragraph (c)(5) of this 
section. Design your bench aging to represent 10,000 hours of in-use 
engine operation for every 1,000 hours of accelerated bench aging. Use 
the accelerated bench-aging procedure in 40 CFR 1065.1131 through 
1065.1145 or get our advance approval to use a different procedure that 
adequately that accounts for thermal and chemical degradation. For 
example, this might involve testing consistent with the analogous 
procedures that apply for light-duty vehicles under 40 CFR part 86, 
subpart S.

[[Page 4511]]

    (7) After bench-aging aftertreatment devices, install or reinstall 
those aftertreatment devices and systems on an emission-data engine (or 
an equivalent engine) that has been stabilized without aftertreatment. 
Ensure that the aftertreatment is installed such that the engine is in 
a certified configuration to represent the engine family.
    (8) Operate the engine with the bench-aged aftertreatment devices 
to stabilize emission controls for at least 100 hours on an engine 
dynamometer.
    (9) Once stabilization is complete, repeat the low-hour emission 
measurements.
    (10) Calculate deterioration factors by comparing exhaust emissions 
with the bench-aged aftertreatment and exhaust emissions at the low-
hour test point. Create a linear curve fit if testing includes 
intermediate test points. Calculate deterioration factors based on 
measured values, without extrapolation.
    (d) If you determine deterioration factors as described in 
paragraph (c) of this section, you may apply those deterioration 
factors in later years for engine families that qualify for carryover 
certification as described in Sec.  1036.235(d). You may also apply 
those deterioration factors for additional engine families as described 
in paragraph (a) of this section.
    (e) Include the following information in your application for 
certification:
    (1) If you use test data from a different engine family, explain 
why this is appropriate and include all the emission measurements on 
which you base the deterioration factors. If the deterioration factors 
for the new engine family are not identical to the deterioration 
factors for the different engine family, describe your engineering 
analysis to justify the revised values and state that all your data, 
analyses, evaluations, and other information are available for our 
review upon request.
    (2) If you determined deterioration factors under paragraph (c) of 
this section, include the following information in the first year that 
you use those deterioration factors:
    (i) Describe your accelerated bench aging or other procedures to 
represent full-life service accumulation for the engine's emission 
controls.
    (ii) Describe how you prepared the test engine before and after 
installing aftertreatment systems to determine deterioration factors.
    (iii) Identify the power rating of the emission-data engine used to 
determine deterioration factors.

Sec.  1036.246  Verifying deterioration factors.

    We may require you to test in-use engines as described in this 
section to verify that the deterioration factors you determined under 
Sec.  1036.245 are appropriate.
    (a) Select and prepare in-use engines representing the engine 
family we identify for verification testing under this section as 
follows:
    (1) You may recruit candidate engines any time before testing. This 
may involve creating a pool of candidate engines and vehicles in 
coordination with vehicle manufacturers and vehicle purchasers to 
ensure availability and to confirm a history of proper maintenance. You 
may meet the testing requirements of this section by repeating tests on 
a given engine as it ages, or you may test different engines over the 
course of verification testing; however, you may not choose whether to 
repeat tests on a given engine at a later stage based on its measured 
emission levels. We generally require that you describe your plan for 
selecting engines in advance and justify any departures from that plan.
    (2) Selected vehicles must come from independent sources, unless we 
approve your request to select vehicles that you own or manage. In your 
request, you must describe how you will ensure that the vehicle 
operator will drive in a way that represents normal in-use operation 
for the engine family.
    (3) Select vehicles with installed engines from the same engine 
family and with the same power rating as the emission-data engine used 
to determine the deterioration factors. However, if the test engine 
does not have the specified power rating, you may ask for our approval 
to either test in the as-received condition or modify engines in 
selected vehicles by reflashing the ECM or replacing parts to change 
the engines to be in a different certified configuration for proper 
testing.
    (4) Selected engines must meet the screening criteria described in 
Sec.  1036.410(b)(2) through (4). Selected engines must also have their 
original aftertreatment components and be in a certified configuration. 
You may ask us to approve replacing a critical emission-related 
component with an equivalent part that has undergone a comparable 
degree of aging.
    (5) We may direct you to preferentially select certain types of 
vehicles, vehicles from certain model years. or vehicles within some 
range of service accumulation. We will not direct you to select 
vehicles that are 10 or more years old, or vehicles with an odometer 
reading exceeding 85 percent of the engine's useful life. We will 
specify a time frame for completing required testing.
    (b) Perform verification testing with one of the following 
procedures, or with an alternative procedure that you demonstrate to be 
equally effective:
    (1) Engine dynamometer testing. Measure emissions from engines 
equipped with in-use aftertreatment systems on an engine dynamometer as 
follows:
    (i) Test the aftertreatment system from at least two engines using 
the procedures specified in subpart F of this part and 40 CFR part 
1065. Install the aftertreatment system from the selected in-use 
vehicle, including all associated wiring, sensors, and related hardware 
and software, on one of the following partially complete engines:
    (A) The in-use engine from the same vehicle.
    (B) The emission-data engine used to determine the deterioration 
factors.
    (C) A different emission-data engine from the same engine family 
that has been stablized as described in 40 CFR 1065.405(c).
    (ii) Perform testing on all certification duty cycles with brake-
specific emission standards (g/hp[middot]hr) to determine whether the 
engine meets all the duty-cycle emission standards, including any 
compliance allowance, for criteria pollutants. Apply infrequent 
regeneration adjustment factors as included in your application for 
certification or develop new factors if we request it.
    (iii) Evaluate verification testing for each pollutant 
independently. You pass the verification test if at least 70 percent of 
tested engines meet standards for each pollutant over all duty cycles. 
You fail the verification test if fewer than 70 percent of engines meet 
standards for a given pollutant over all duty cycles.
    (2) PEMS testing. Measure emissions using PEMS with in-use engines 
that remain installed in selected vehicles as follows:
    (i) Test at least five engines using the procedures specified in 
Sec.  1036.555 and 40 CFR part 1065, subpart J.
    (ii) Measure emissions of NOX, HC, and CO as the test 
vehicle's normal operator drives over a regular shift-day to determine 
whether the engine meets all the off-cycle emission standards that 
applied for the engine's original certification. Apply infrequent 
regeneration adjustment factors as included in your application for 
certification. For Spark-ignition HDE, calculate off-cycle emission 
standards for purposes of this subpart by multiplying the FTP duty-
cycle standards in Sec.  1036.104(a) by 1.5 and

[[Page 4512]]

rounding to the same number of decimal places.
    (iii) Evaluate verification testing for each pollutant 
independently. You pass the verification test if at least 70 percent of 
tested engines meet the off-cycle standards including any compliance 
allowance and accuracy margin, for each pollutant. You fail the 
verification test if fewer than 70 percent of tested engines do not 
meet standards for a given pollutant.
    (iv) You may reverse a fail determination under paragraph 
(b)(2)(iii) of this section by restarting and successfully completing 
the verification test for that year using the procedures specified in 
paragraph (b)(1) of this section. If you do this, you must use the 
verification testing procedures specified in paragraph (b)(1) of this 
section for all remaining verification testing for the engine family.
    (c) You may stop testing under the verification test program and 
concede a fail result before you meet all the testing requirements of 
this section.
    (d) Prepare a report to describe your verification testing each 
year. Include at least the following information:
    (1) Identify whether you tested using the procedures specified in 
paragraph (b)(1) or (2) of this section.
    (2) Describe how the test results support a pass or fail decision 
for the verification test. For in-field measurements, include 
continuous 1 Hz data collected over the shift-day and binned emission 
values determined under Sec.  1036.530.
    (3) If your testing included invalid test results, describe the 
reasons for invalidating the data. Give us the invalid test results if 
we ask for them.
    (4) Describe the types of vehicles selected for testing. If you 
determined that any selected vehicles with enough mileage accumulation 
were not suitable for testing, describe why you chose not to test them.
    (5) For each tested engine, identify the vehicle's VIN, the 
engine's serial number, the engine's power rating, and the odometer 
reading and the engine's lifetime operating hours at the start of 
testing (or engine removal).
    (6) State that the tested engines have been properly maintained and 
used and describe any noteworthy aspects of each vehicle's maintenance 
history. Describe the steps you took to prepare the engines for 
testing.
    (7) For testing with engines that remain installed in vehicles, 
identify the date and location of testing. Also describe the ambient 
conditions and the driving route over the course of the shift-day.
    (e) Send electronic reports to the Designated Compliance Officer 
using an approved information format. If you want to use a different 
format, send us a written request with justification.
    (1) You may send us reports as you complete testing for an engine 
instead of waiting until you complete testing for all engines.
    (2) We may ask you to send us less information in your reports than 
we specify in this section.
    (3) We may require you to send us more information to evaluate 
whether your engine family meets the requirements of this part.
    (4) Once you send us information under this section, you need not 
send that information again in later reports.
    (5) We will review your test report to evaluate the results of the 
verification testing at each stage. We will notify you if we disagree 
with your conclusions, if we need additional information, or if you 
need to revise your testing plan for future testing.

Sec.  1036.250  Reporting and recordkeeping for certification.

    (a) By September 30 following the end of the model year, send the 
Designated Compliance Officer a report including the total nationwide 
production volume of engines you produced in each engine family during 
the model year (based on information available at the time of the 
report). Report the production by serial number and engine 
configuration. You may combine this report with reports required under 
subpart H of this part. We may waive the reporting requirements of this 
paragraph (a) for small manufacturers.
    (b) Organize and maintain the following records:
    (1) A copy of all applications and any summary information you send 
us.
    (2) Any of the information we specify in Sec.  1036.205 that you 
were not required to include in your application.
    (3) A detailed history of each emission-data engine. For each 
engine, describe all of the following:
    (i) The emission-data engine's construction, including its origin 
and buildup, steps you took to ensure that it represents production 
engines, any components you built specially for it, and all the 
components you include in your application for certification.
    (ii) How you accumulated engine operating hours (service 
accumulation), including the dates and the number of hours accumulated.
    (iii) All maintenance, including modifications, parts changes, and 
other service, and the dates and reasons for the maintenance.
    (iv) All your emission tests, including documentation on routine 
and standard tests, as specified in part 40 CFR part 1065, and the date 
and purpose of each test.
    (v) All tests to diagnose engine or emission control performance, 
giving the date and time of each and the reasons for the test.
    (vi) Any other significant events.
    (4) Production figures for each engine family divided by assembly 
plant.
    (5) Engine identification numbers for all the engines you produce 
under each certificate of conformity.
    (c) Keep routine data from emission tests required by this part 
(such as test cell temperatures and relative humidity readings) for one 
year after we issue the associated certificate of conformity. Keep all 
other information specified in this section for eight years after we 
issue your certificate.
    (d) Store these records in any format and on any media, as long as 
you can promptly send us organized, written records in English if we 
ask for them. You must keep these records readily available. We may 
review them at any time.

Sec.  1036.255  EPA oversight on certificates of conformity.

    (a) If we determine an application is complete and shows that the 
engine family meets all the requirements of this part and the Act, we 
will issue a certificate of conformity for the engine family for that 
model year. We may make the approval subject to additional conditions.
    (b) We may deny an application for certification if we determine 
that an engine family fails to comply with emission standards or other 
requirements of this part or the Clean Air Act. We will base our 
decision on all available information. If we deny an application, we 
will explain why in writing.
    (c) In addition, we may deny your application or suspend or revoke 
a certificate of conformity if you do any of the following:
    (1) Refuse to comply with any testing or reporting requirements in 
this part.
    (2) Submit false or incomplete information. This includes doing 
anything after submitting an application that causes submitted 
information to be false or incomplete.
    (3) Cause any test data to become inaccurate.
    (4) Deny us from completing authorized activities (see 40 CFR 
1068.20). This includes a failure to provide reasonable assistance.
    (5) Produce engines for importation into the United States at a 
location where local law prohibits us from carrying out authorized 
activities.

[[Page 4513]]

    (6) Fail to supply requested information or amend an application to 
include all engines being produced.
    (7) Take any action that otherwise circumvents the intent of the 
Act or this part.
    (d) We may void a certificate of conformity if you fail to keep 
records, send reports, or give us information as required under this 
part or the Act. Note that these are also violations of 40 CFR 
1068.101(a)(2).
    (e) We may void a certificate of conformity if we find that you 
intentionally submitted false or incomplete information. This includes 
doing anything after submitting an application that causes submitted 
information to be false or incomplete after submission.
    (f) If we deny an application or suspend, revoke, or void a 
certificate, you may ask for a hearing (see Sec.  1036.820).

Subpart D--Testing Production Engines and Hybrid Powertrains

Sec.  1036.301  Measurements related to GEM inputs in a selective 
enforcement audit.

    (a) Selective enforcement audits apply for engines as specified in 
40 CFR part 1068, subpart E. This section describes how this applies 
uniquely in certain circumstances.
    (b) Selective enforcement audit provisions apply with respect to 
your fuel maps as follows:
    (1) A selective enforcement audit for an engine with respect to 
fuel maps would consist of performing measurements with production 
engines to determine fuel-consumption rates as declared for GEM 
simulations, and running GEM for the vehicle configurations specified 
in paragraph (b)(2) of this section based on those measured values. The 
engine is considered passing for a given configuration if the new 
modeled emission result for each applicable duty cycle is at or below 
the modeled emission result corresponding to the declared GEM inputs. 
The engine is considered failing if we determine that its fuel map 
result is above the modeled emission result corresponding to the result 
using the manufacturer-declared fuel maps, as specified in Sec.  
1036.235(c)(5).
    (2) If the audit includes fuel-map testing in conjunction with 
engine testing relative to exhaust emission standards, the fuel-map 
simulations for the whole set of vehicles and duty cycles counts as a 
single test result for purposes of evaluating whether the engine family 
meets the pass-fail criteria under 40 CFR 1068.420.
    (c) If your certification includes powertrain testing as specified 
in 40 CFR 1036.630, these selective enforcement audit provisions apply 
with respect to powertrain test results as specified in 40 CFR part 
1037, subpart D, and 40 CFR 1037.550. We may allow manufacturers to 
instead perform the engine-based testing to simulate the powertrain 
test as specified in 40 CFR 1037.551.
    (d) We may suspend or revoke certificates for any appropriate 
configurations within one or more engine families based on the outcome 
of a selective enforcement audit.

Subpart E--In-Use Testing

Sec.  1036.401  Testing requirements for in-use engines.

    (a) We may perform in-use testing of any engine family subject to 
the standards of this part, consistent with the Clean Air Act and the 
provisions of Sec.  1036.235.
    (b) This subpart describes a manufacturer-run field-testing program 
that applies for engines subject to compression-ignition standards 
under Sec.  1036.104. Note that the testing requirements of 40 CFR part 
86, subpart T, continue to apply for engines subject to exhaust 
emission standards under 40 CFR part 86.
    (c) In-use test procedures for engines subject to spark-ignition 
standards apply as described in Sec.  1036.530. We won't require 
routine manufacturer-run field testing for Spark-ignition HDE, but the 
procedures of this subpart describe how to use field-testing procedures 
to measure emissions from engines installed in vehicles. Use good 
engineering judgment to apply the measurement procedures for fuels 
other than gasoline.
    (d) We may void your certificate of conformity for an engine family 
if you do not meet your obligations under this subpart. We may also 
void individual tests and require you to retest those vehicles or take 
other appropriate measures in instances where you have not performed 
the testing in accordance with the requirements described in this 
subpart.

Sec.  1036.405  Overview of the manufacturer-run field-testing program.

    (a) You must test in-use engines from the families we select. We 
may select the following number of engine families for testing, except 
as specified in paragraph (b) of this section:
    (1) We may select up to 25 percent of your engine families in any 
calendar year, calculated by dividing the number of engine families you 
certified in the model year corresponding to the calendar year by four 
and rounding to the nearest whole number. We will consider only engine 
families with annual nationwide production volumes above 1,500 units in 
calculating the number of engine families subject to testing each 
calendar year under the annual 25 percent engine family limit. If you 
have only three or fewer families that each exceed an annual nationwide 
production volume of 1,500 units, we may select one engine family per 
calendar year for testing.
    (2) Over any four-year period, we will not select more than the 
average number of engine families that you have certified over that 
four-year period (the model year when the selection is made and the 
preceding three model years), based on rounding the average value to 
the nearest whole number.
    (3) We will not select engine families for testing under this 
subpart from a given model year if your total nationwide production 
volume was less than 100 engines.
    (b) If there is clear evidence of a nonconformity with regard to an 
engine family, we may select that engine family without counting it as 
a selected engine family under paragraph (a) of this section. For 
example, there may be clear evidence of a nonconformity if you certify 
an engine family using carryover data after reaching a fail decision 
under this subpart in an earlier model year without modifying the 
engine to remedy the problem.
    (c) We may select any individual engine family for testing, 
regardless of its production volume except as described in paragraph 
(a)(3) of this section, as long as we do not select more than the 
number of engine families described in paragraph (a) of this section. 
We may select an engine family from model year 2027 or any later model 
year.
    (d) You must complete all the required testing and reporting under 
this subpart (for all ten test engines, if applicable), within 18 
months after we receive your proposed plan for recruiting, screening, 
and selecting vehicles. We will typically select engine families for 
testing and notify you in writing by June 30 of the applicable calendar 
year. If you request it, we may allow additional time to send us this 
information.
    (e) If you make a good-faith effort to access enough test vehicles 
to complete the testing requirements under this subpart for an engine 
family, but are unable to do so, you must ask us either to modify the 
testing requirements for the selected engine family or to select a 
different engine family.

[[Page 4514]]

    (f) We may select an engine family for repeat testing in a later 
calendar year. Such a selection for repeat testing would count as an 
additional engine family for that year under paragraph (a) of this 
section.

Sec.  1036.410  Selecting and screening vehicles and engines for 
testing.

    (a) Send us your proposed plan for recruiting, screening, and 
selecting vehicles. Identify the types of vehicles, location, and any 
other relevant criteria. We will approve your plan if it supports the 
objective of measuring emissions to represent a broad range of 
operating characteristics.
    (b) Select vehicles and engines for testing that meet the following 
criteria:
    (1) The vehicles come from at least two independent sources.
    (2) Powertrain, drivetrain, emission controls, and other key 
vehicle and engine systems have been properly maintained and used. See 
Sec.  1036.125.
    (3) The engines have not been tampered with, rebuilt, or undergone 
major repair that could be expected to affect emissions.
    (4) The engines have not been misfueled. Do not consider engines 
misfueled if they have used fuel meeting the specifications of Sec.  
1036.415(c).
    (5) The vehicles are likely to operate for at least three hours of 
non-idle operation over a complete shift-day, as described in Sec.  
1036.415(f).
    (6) The vehicles have not exceeded the applicable useful life, in 
miles, hours, or years; you may otherwise not exclude engines from 
testing based on their age or mileage.
    (7) The vehicle has appropriate space for safe and proper mounting 
of the portable emission measurement system (PEMS) equipment.
    (c) You must notify us before disqualifying any vehicle based on 
illuminated MIL or stored OBD trouble codes as described in Sec.  
1036.415(b)(2), or for any other reasons not specified in paragraph (b) 
of this section. For example, notify us if you disqualify any vehicle 
because the engine does not represent the engine family or the 
vehicle's usage is atypical for the particular application. You do not 
need to notify us in advance if the owner declines to participate in 
the test program.

Sec.  1036.415  Preparing and testing engines.

    (a) You must limit maintenance to what is in the owners manual for 
engines with that amount of service and age. For anything we consider 
an adjustable parameter (see Sec.  1036.115(f)), you may adjust that 
parameter only if it is outside its adjustable range. You must then set 
the adjustable parameter to your recommended setting or the mid-point 
of its adjustable range, unless we approve your request to do 
otherwise. You must get our approval before adjusting anything not 
considered an adjustable parameter. You must keep records of all 
maintenance and adjustments, as required by Sec.  1036.435. You must 
send us these records, as described in Sec.  1036.430(a)(2)(ix), unless 
we instruct you not to send them.
    (b) You may treat a vehicle with an illuminated MIL or stored 
trouble code as follows:
    (1) If a candidate vehicle has an illuminated MIL or stored trouble 
code, either test the vehicle as received or repair the vehicle before 
testing. Once testing is initiated on the vehicle, you accept that the 
vehicle has been properly maintained and used.
    (2) If a MIL illuminates or a trouble code appears on a test 
vehicle during a field test, stop the test and repair the vehicle. 
Determine test results as specified in Sec.  1036.530 using one of the 
following options:
    (i) Restart the testing and use only the portion of the full test 
results without the MIL illuminated or trouble code set.
    (ii) Initiate a new test and use only the post-repair test results.
    (3) If you determine that repairs are needed but they cannot be 
completed in a timely manner, you may disqualify the vehicle and 
replace it with another vehicle.
    (c) Use appropriate fuels for testing, as follows:
    (1) You may use any diesel fuel that meets the specifications for 
S15 in ASTM D975 (incorporated by reference in Sec.  1036.810). You may 
use any commercially available biodiesel fuel blend that meets the 
specifications for ASTM D975 or ASTM D7467 (incorporated by reference 
in Sec.  1036.810) that is either expressly allowed or not otherwise 
indicated as an unacceptable fuel in the vehicle's owner or operator 
manual or in the engine manufacturer's published fuel recommendations. 
You may use any gasoline fuel that meets the specifications in ASTM 
D4814 (incorporated by reference in Sec.  1036.810). For other fuel 
types, you may use any commercially available fuel.
    (2) You may drain test vehicles' fuel tanks and refill them with 
diesel fuel conforming to the specifications in paragraph (c)(1) of 
this section.
    (3) Any fuel that is added to a test vehicle's fuel tanks must be 
purchased at a local retail establishment near the site of vehicle 
recruitment or screening, or along the test route. Alternatively, the 
fuel may be drawn from a central fueling source, as long as the fuel 
represents commercially available fuel in the area of testing.
    (4) No post-refinery fuel additives are allowed, except that 
specific fuel additives may be used during field testing if you can 
document that the test vehicle has a history of normally using the fuel 
treatments and they are not prohibited in the owners manual or in your 
published fuel-additive recommendations.
    (5) You may take fuel samples from test vehicles to ensure that 
appropriate fuels were used during field testing. If a vehicle fails 
the vehicle-pass criteria and you can show that an inappropriate fuel 
was used during the failed test, that particular test may be voided. 
You may drain vehicles' fuel tanks and refill them with diesel fuel 
conforming to the specifications described in paragraph (c)(1) of this 
section. You must report any fuel tests that are the basis of voiding a 
test in your report under Sec.  1036.430.
    (d) You must test the selected engines using the test procedure 
described in Sec.  1036.530 while they remain installed in the vehicle. 
Testing consists of characterizing emission rates for moving average 
300 second windows while driving, with those windows divided into bins 
representing different types of engine operation over a shift-day. 
Measure emissions as follows:
    (1) Perform all testing with PEMS and field-testing procedures 
referenced in 40 CFR part 1065, subpart J. Measure emissions of 
NOX, CO, and CO2. We may require you to also 
measure emissions of HC and PM. You may determine HC emissions by any 
method specified in 40 CFR 1065.660(b).
    (2) If the engine's crankcase discharges emissions into the ambient 
atmosphere, as allowed by Sec.  1036.115(a), you must either route all 
crankcase emissions into the exhaust for a combined measurement or add 
the crankcase emission values specified in Sec.  1036.240(e) to 
represent emission levels at full useful life instead of measuring 
crankcase emissions in the field.
    (e) Operate the test vehicle under conditions reasonably expected 
during normal operation. For the purposes of this subpart, normal 
operation generally includes the vehicle's normal routes and loads 
(including auxiliary loads such as air conditioning in the cab), normal 
ambient conditions, and the normal driver.
    (f) Once an engine is set up for testing, test the engine for one 
shift-day, except as allowed in Sec.  1036.420(d). To complete a shift-
day's worth of testing,

[[Page 4515]]

start sampling at the beginning of a shift and continue sampling for 
the whole shift, subject to the calibration requirements of the PEMS. A 
shift-day is the period of a normal workday for an individual employee. 
Evaluate the emission data as described in Sec.  1036.420 and include 
the data in the reporting and record keeping requirements specified in 
Sec. Sec.  1036.430 and 1036.435.
    (g) For stop-start and automatic engine shutdown systems meeting 
the specifications of 40 CFR 1037.660, override idle-reduction features 
if they are adjustable under 40 CFR 1037.520(j)(4). If those systems 
are tamper-resistant under 40 CFR 1037.520(j)(4), set the 1-Hz emission 
rate to zero for all regulated pollutants when the idle-reduction 
feature is active. Do not exclude these data points under Sec.  
1036.530(c)(3)(ii).

Sec.  1036.420  Pass criteria for individual engines.

    Perform the following steps to determine whether an engine meets 
the binned emission standards in Sec.  1036.104(a)(3):
    (a) Determine the emission standard for each regulated pollutant 
for each bin by adding the following accuracy margins for PEMS to the 
off-cycle standards in Sec.  1036.104(a)(3):

                Table 1 to Paragraph (a) of Sec.   1036.420--Accuracy Margins for In-Use Testing
----------------------------------------------------------------------------------------------------------------
                                       NOX                HC                PM                     CO
----------------------------------------------------------------------------------------------------------------
Bin 1.........................  0.4 g/hr.........
Bin 2.........................  5 mg/hp[middot]hr  10 mg/            6 mg/             0.025 g/hp[middot]hr.
                                                    hp[middot]hr.     hp[middot]hr.
----------------------------------------------------------------------------------------------------------------

    (b) Calculate the mass emission rate for each pollutant as 
specified in Sec.  1036.530.
    (c) For engines subject to compression-ignition standards, 
determine the number of windows in each bin. A bin is valid under this 
section only if it has at least 2,400 windows for bin 1 and 10,000 
windows for bin 2.
    (d) Continue testing additional shift-days as necessary to achieve 
the minimum window requirements for each bin. You may idle the engine 
at the end of the shift day to increase the number of windows in bin 1. 
If the vehicle has tamper-resistant idle-reduction technology that 
prevents idling, populate bin 1 with additional windows by setting the 
1-Hz emission rate for all regulated pollutants to zero as described in 
Sec.  1036.415(g) to achieve exactly 2,400 bin 1 windows.
    (e) An engine passes if the result for each bin is at or below the 
standard determined in paragraph (a) of this section. An engine fails 
if the result for any bin for any pollutant is above the standard 
determined in paragraph (a) of this section.

Sec.  1036.425  Pass criteria for engine families.

    For testing with PEMS under Sec.  1036.415(d)(1), determine the 
number of engines you must test from each selected engine family and 
the family pass criteria as follows:
    (a) Start by measuring emissions from five engines using the 
procedures described in this subpart E and Sec.  1036.530. If all five 
engines comply fully with the off-cycle bin standards, the engine 
family passes, and you may stop testing.
    (b) If only one of the engines tested under paragraph (a) of this 
section does not comply fully with the off-cycle bin standards, test 
one more engine. If this additional engine complies fully with the off-
cycle bin standards, the engine family passes, and you may stop 
testing.
    (c) If two or more engines tested under paragraphs (a) and (b) of 
this section do not comply fully with the off-cycle bin standards, test 
additional engines until you have tested a total of ten engines. 
Calculate the arithmetic mean of the bin emissions from the ten engine 
tests as specified in Sec.  1036.530(g) for each pollutant. If the mean 
values are at or below the off-cycle bin standards, the engine family 
passes. If the mean value for any pollutant is above an off-cycle bin 
standard, the engine family fails.
    (d) You may accept a fail result for the engine family and 
discontinue testing at any point in the sequence of testing the 
specified number of engines.

Sec.  1036.430  Reporting requirements.

    (a) Report content. Prepare test reports as follows:
    (1) Include the following for each engine family:
    (i) Describe how you recruited vehicles. Describe how you used any 
criteria or thresholds to narrow your search or to screen individual 
vehicles.
    (ii) Include a summary of the vehicles you have disqualified and 
the reasons you disqualified them, whether you base the 
disqualification on the criteria in Sec.  1036.410(b), owner 
nonparticipation, or anything else. If you disqualified a vehicle due 
to misfueling, include the results of any fuel sample tests. If you 
reject a vehicle due to tampering, describe how you determined that 
tampering occurred.
    (iii) Identify how many engines you have tested from the applicable 
engine family and how many engines still need to be tested. Identify 
how many tested engines have passed or failed under Sec.  1036.420.
    (iv) After the final test, report the results and state the outcome 
of testing for the engine family based on the criteria in Sec.  
1036.425.
    (v) Describe any incomplete or invalid tests that were conducted 
under this subpart.
    (2) Include the following information for the test vehicle:
    (i) The EPA engine-family designation, and the engine's model 
number, total displacement, and power rating.
    (ii) The date EPA selected the engine family for testing.
    (iii) The vehicle's make and model and the year it was built.
    (iv) The vehicle identification number and engine serial number.
    (v) The vehicle's type or application (such as delivery, line haul, 
or dump truck). Also, identify the type of trailer, if applicable.
    (vi) The vehicle's maintenance and use history.
    (vii) The known status history of the vehicle's OBD system and any 
actions taken to address OBD trouble codes or MIL illumination over the 
vehicle's lifetime.
    (viii) Any OBD codes or MIL illumination that occur after you 
accept the vehicle for field testing under this subpart.
    (ix) Any steps you take to maintain, adjust, modify, or repair the 
vehicle or its engine to prepare for or continue testing, including 
actions to address OBD trouble codes or MIL illumination. Include any 
steps you took to drain and refill the vehicle's fuel tank(s) to 
correct misfueling, and the results of any fuel test conducted to 
identify misfueling.
    (3) Include the following data and measurements for each test 
vehicle:
    (i) The date and time of testing, and the test number.

[[Page 4516]]

    (ii) Number of shift-days of testing (see Sec.  1036.415(f)).
    (iii) Route and location of testing. You may base this description 
on the output from a global-positioning system (GPS).
    (iv) The steps you took to ensure that vehicle operation during 
testing was consistent with normal operation and use, as described in 
Sec.  1036.415(e).
    (v) Fuel test results, if fuel was tested under Sec.  1036.410 or 
Sec.  1036.415.
    (vi) The vehicle's mileage at the start of testing. Include the 
engine's total lifetime hours of operation, if available.
    (vii) The number of windows in each bin (see Sec.  1036.420(c)).
    (viii) The bin emission value per vehicle for each pollutant. 
Describe the method you used to determine HC as specified in 40 CFR 
1065.660(b).
    (ix) Recorded 1 Hz test data for at least the following parameters, 
noting that gaps in the 1 Hz data file over the shift-day are only 
allowed during analyzer zero and span verifications and during engine 
shutdown when the engine is keyed off:
    (A) Ambient temperature.
    (B) Ambient pressure.
    (C) Ambient humidity.
    (D) Altitude.
    (E) Emissions of HC, CO, CO2, and NOX. Report 
results for PM if it was measured in a manner that provides 1 Hz test 
data.
    (F) Differential backpressure of any PEMS attachments to vehicle 
exhaust.
    (G) Exhaust flow.
    (H) Exhaust aftertreatment temperatures.
    (I) Engine speed.
    (J) Engine brake torque.
    (K) Engine coolant temperature
    (L) Intake manifold temperature.
    (M) Intake manifold pressure.
    (N) Throttle position.
    (O) Any parameter sensed or controlled, available over the 
Controller Area Network (CAN) network, to modulate the emission control 
system or fuel-injection timing.
    (4) Include the following summary information after you complete 
testing with each engine:
    (i) State whether the engine meets the off-cycle standards for each 
bin for each pollutant as described in Sec.  1036.420(e).
    (ii) Describe if any testing or evaluations were conducted to 
determine why a vehicle failed the off-cycle emission standards 
described in Sec.  1036.420.
    (iii) Describe the purpose of any diagnostic procedures you 
conduct.
    (iv) Describe any instances in which the OBD system illuminated the 
MIL or set trouble codes. Also describe any actions taken to address 
the trouble codes or MIL.
    (v) Describe any instances of misfueling, the approved actions 
taken to address the problem, and the results of any associated fuel 
sample testing.
    (vi) Describe the number and length of any data gaps in the 1 Hz 
data file, the reason for the gap(s), and the parameters affected.
    (b) Submission. Send electronic reports to the Designated 
Compliance Officer using an approved information format. If you want to 
use a different format, send us a written request with justification.
    (1) You may send us reports as you complete testing for an engine 
instead of waiting until you complete testing for all engines.
    (2) We may ask you to send us less information in your reports than 
we specify in this section.
    (3) We may require you to send us more information to evaluate 
whether your engine family meets the requirements of this part.
    (4) Once you send us information under this section, you need not 
send that information again in later reports.
    (c) Additional notifications. Notify the Designated Compliance 
Officer describing progress toward completing the required testing and 
reporting under this subpart, as follows:
    (1) Notify us once you complete testing for an engine.
    (2) Notify us if your review of the test data for an engine family 
indicates that two of the first five tested engines have failed to 
comply with the vehicle-pass criteria in Sec.  1036.420(e).
    (3) Notify us if your review of the test data for an engine family 
indicates that the engine family does not comply with the family-pass 
criteria in Sec.  1036.425(c).
    (4) Describe any voluntary vehicle/engine emission evaluation 
testing you intend to conduct with PEMS on the same engine families 
that are being tested under this subpart, from the time that engine 
family was selected for field testing under Sec.  1036.405 until the 
final results of all testing for that engine family are reported to us 
under this section.

Sec.  1036.435  Recordkeeping requirements.

    Keep the following paper or electronic records of your field 
testing for five years after you complete all the testing required for 
an engine family:
    (a) Keep a copy of the reports described in Sec.  1036.430.
    (b) Keep any additional records, including forms you create, 
related to any of the following:
    (1) The recruitment, screening, and selection process described in 
Sec.  1036.410, including the vehicle owner's name, address, phone 
number, and email address.
    (2) Pre-test maintenance and adjustments to the engine performed 
under Sec.  1036.415.
    (3) Test results for all void, incomplete, and voluntary testing 
described in Sec.  1036.430.
    (4) Evaluations to determine why an engine failed any of the bin 
standards described in Sec.  1036.420.
    (c) Keep a copy of the relevant calibration results required by 40 
CFR part 1065.

Sec.  1036.440  Warranty obligations related to in-use testing.

    Testing under this subpart that finds an engine exceeding emission 
standards under this subpart is not by itself sufficient to show a 
breach of warranty under 42 U.S.C. 7541(a)(1). A breach of warranty 
would also require that engines fail to meet one or both of the 
conditions specified in Sec.  1036.120(a).

Subpart F--Test Procedures

Sec.  1036.501  General testing provisions.

    (a) Use the equipment and procedures specified in this subpart and 
40 CFR part 1065 to determine whether engines meet the emission 
standards in Sec. Sec.  1036.104 and 1036.108.
    (b) Use the fuels specified in 40 CFR part 1065 to perform valid 
tests, as follows:
    (1) For service accumulation, use the test fuel or any commercially 
available fuel that is representative of the fuel that in-use engines 
will use.
    (2) For diesel-fueled engines, use the ultra-low-sulfur diesel fuel 
specified in 40 CFR part 1065.703 and 40 CFR 1065.710(b)(3) for 
emission testing.
    (3) For gasoline-fueled engines, use the appropriate E10 fuel 
specified in 40 CFR part 1065.
    (c) For engines that use aftertreatment technology with infrequent 
regeneration events, apply infrequent regeneration adjustment factors 
for each duty cycle as described in Sec.  1036.580.
    (d) If your engine is intended for installation in a vehicle 
equipped with stop-start technology meeting the specifications of 40 
CFR 1037.660 to qualify as tamper-resistant under 40 CFR 
1037.520(j)(4), you may shut the engine down during idle portions of 
the duty cycle to represent in-use operation. We recommend installing a 
production engine starter motor and letting the engine's ECM manipulate 
the starter motor to control the engine stop and start events. Use good 
engineering judgment to address the effects of dynamometer inertia on 
restarting the engine by, for example, using a larger starter motor or 
declutching the engine from the dynamometer during restart.

[[Page 4517]]

    (e) You may use special or alternate procedures to the extent we 
allow them under 40 CFR 1065.10.
    (f) This subpart is addressed to you as a manufacturer, but it 
applies equally to anyone who does testing for you, and to us when we 
perform testing to determine if your engines meet emission standards.

Sec.  1036.505  Engine data and information to support vehicle 
certification.

    You must give vehicle manufacturers information as follows so they 
can certify their vehicles to greenhouse gas emission standards under 
40 CFR part 1037:
    (a) Identify engine make, model, fuel type, combustion type, engine 
family name, calibration identification, and engine displacement. Also 
identify whether the engines meet CO2 standards for 
tractors, vocational vehicles, or both.
    (b) This paragraph (b) describes four different methods to generate 
engine fuel maps. For engines without hybrid components and for mild 
hybrid engines where you do not include hybrid components in the test, 
generate fuel maps using either paragraph (b)(1) or (2) of this 
section. For other hybrid engines, generate fuel maps using paragraph 
(b)(3) of this section. For hybrid and nonhybrid powertrains and for 
vehicles where the transmission is not automatic, automated manual, 
manual, or dual-clutch, generate fuel maps using paragraph (b)(4) of 
this section.
    (1) Determine steady-state engine fuel maps as described in Sec.  
1036.535(b). Determine fuel consumption at idle as described in Sec.  
1036.535 (c). Determine cycle-average engine fuel maps as described in 
Sec.  1036.540, excluding cycle-average fuel maps for highway cruise 
cycles.
    (2) Determine steady-state fuel maps as described in either Sec.  
1036.535(b) or (d). Determine fuel consumption at idle as described in 
Sec.  1036.535(c). Determine cycle-average engine fuel maps as 
described in Sec.  1036.540, including cycle-average engine fuel maps 
for highway cruise cycles. We may do confirmatory testing by creating 
cycle-average fuel maps from steady-state fuel maps created in 
paragraph (b)(1) of this section for highway cruise cycles. In Sec.  
1036.540 we define the vehicle configurations for testing; we may add 
more vehicle configurations to better represent your engine's operation 
for the range of vehicles in which your engines will be installed (see 
40 CFR 1065.10(c)(1)).
    (3) Determine fuel consumption at idle as described in Sec.  
1036.535(c) and (d) and determine cycle-average engine fuel maps as 
described in 40 CFR 1037.550, including cycle-average engine fuel maps 
for highway cruise cycles. Set up the test to apply accessory load for 
all operation by primary intended service class as described in the 
following table:

     Table 1 to Paragraph (b)(3) of Sec.   1036.505--Accessory Load
------------------------------------------------------------------------
                                                              Power
                                                          representing
            Primary intended service class               accessory load
                                                              (kW)
------------------------------------------------------------------------
Light HDV.............................................               1.5
Medium HDV............................................               2.5
Heavy HDV.............................................               3.5
------------------------------------------------------------------------

    (4) Generate powertrain fuel maps as described in 40 CFR 1037.550 
instead of fuel mapping under Sec.  1036.535 or Sec.  1036.540. Note 
that the option in 40 CFR 1037.550(b)(2) is allowed only for hybrid 
engine testing. Disable stop-start systems and automatic engine 
shutdown systems when conducting powertrain fuel map testing using 40 
CFR 1037.550.
    (c) Provide the following information if you generate engine fuel 
maps using either paragraph (b)(1), (2), or (3) of this section:
    (1) Full-load torque curve for installed engines and the full-load 
torque curve of the engine (parent engine) with the highest fueling 
rate that shares the same engine hardware, including the turbocharger, 
as described in 40 CFR 1065.510. You may use 40 CFR 1065.510(b)(5)(i) 
for Spark-ignition HDE. Measure the torque curve for hybrid engines 
that have an RESS as described in 40 CFR 1065.510(g)(2) with the hybrid 
system active. Test hybrid engines with no RESS as described in 40 CFR 
1065.510(b)(5)(ii).
    (2) Motoring torque curve as described in 40 CFR 1065.510(c)(2) and 
(5) for nonhybrid and hybrid engines, respectively. For engines with a 
low-speed governor, remove data points where the low-speed governor is 
active. If you don't know when the low-speed governor is active, we 
recommend removing all points below 40 r/min above the warm low-idle 
speed.
    (3) Declared engine idle speed. For vehicles with manual 
transmissions, this is the engine speed with the transmission in 
neutral. For all other vehicles, this is the engine's idle speed when 
the transmission is in drive.
    (4) The engine idle speed during the transient cycle-average fuel 
map.
    (5) The engine idle torque during the transient cycle-average fuel 
map.
    (d) If you generate powertrain fuel maps using paragraph (b)(4) of 
this section, determine the system continuous rated power according to 
Sec.  1036.520.

Sec.  1036.510  Supplemental Emission Test.

    (a) Measure emissions using the steady-state SET duty cycle as 
described in this section. Note that the SET duty cycle is operated as 
a ramped-modal cycle rather than discrete steady-state test points.
    (b) Perform SET testing with one of the following procedures:
    (1) For testing nonhybrid engines, the SET duty cycle is based on 
normalized speed and torque values relative to certain maximum values. 
Denormalize speed as described in 40 CFR 1065.512. Denormalize torque 
as described in 40 CFR 1065.610(d). Note that idle points are to be run 
at conditions simulating neutral or park on the transmission.
    (2) Test hybrid engines and hybrid powertrains as described in 40 
CFR 1037.550, except as specified in this paragraph (b)(2). Do not 
compensate the duty cycle for the distance driven as described in 40 
CFR 1037.550(g)(4). For hybrid engines, select the transmission from 
Table 1 of Sec.  1036.540, substituting ``engine'' for ``vehicle'' and 
``highway cruise cycle'' for ``SET''. Disregard duty cycles in 40 CFR 
1037.550(j). For cycles that begin with idle, leave the transmission in 
neutral or park for the full initial idle segment. Place the 
transmission into drive no earlier than 5 seconds before the first 
nonzero vehicle speed setpoint. For SET testing only, place the 
transmission into park or neutral when the cycle reaches the final idle 
segment. Use the following vehicle parameters instead of those in 40 
CFR 1037.550 to define the vehicle model in 40 CFR 1037.550(a)(3):
    (i) Determine the vehicle test mass, M, as follows:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.016
    
Where:

Pcontrated = the continuous rated power of the hybrid 
system determined in sect; 1036.520.

Example:

Pcontrated = 350.1 kW
M = 15.1[middot]350.1\1.31\
M = 32499 kg

    (ii) Determine the vehicle frontal area, Afront, as 
follows:
    (A) For M <= 18050 kg:

[[Page 4518]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.017

Example:

M = 16499 kg
Afront = 
-1.69[middot]10-\8\[middot]16499\2\+6.33[middot]10
-\4\[middot]16499+1.67
Afront = 7.51 m\2\

    (B) For M > 18050 kg, Afront = 7.59 m\2\
    (iii) Determine the vehicle drag area, CdA, as follows:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.018
    
Where:

g = gravitational constant = 9.80665 m/s\2\.
[rho] = air density at reference conditions. Use [rho] = 1.1845 kg/
m\3\.

Example:
[GRAPHIC] [TIFF OMITTED] TR24JA23.019

    CdA = 3.08 m\2\

    (iv) Determine the coefficient of rolling resistance, 
Crr, as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.020

Example:
[GRAPHIC] [TIFF OMITTED] TR24JA23.021

Crr = 5.7 N/kN = 0.0057 N/N

    (v) Determine the vehicle curb mass, Mcurb, as follows:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.022
    
Example:

Mcurb = -0.000007376537[middot]32499\2\ + 
0.6038432[middot]32499
Mcurb = 11833 kg

    (vi) Determine the linear equivalent mass of rotational moment of 
inertias, Mrotating, as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.023

Example:

Mrotating = 0.07[middot]11833
Mrotating = 828.3 kg

    (vii) Select a drive axle ratio, ka, that represents the 
worst-case combination of final gear ratio, drive axle ratio, and tire 
size for CO2 expected for vehicles in which the hybrid 
powertrain or hybrid engine will be installed. This is typically the 
highest axle ratio.
    (viii) Select a tire radius, r, that represents the worst-case pair 
of tire size and drive axle ratio for CO2 expected for 
vehicles in which the hybrid powertrain or hybrid engine will be 
installed. This is typically the smallest tire radius.
    (ix) If you are certifying a hybrid engine, use a default 
transmission efficiency of 0.95 and create the vehicle model along with 
its default transmission shift strategy as described in 40 CFR 
1037.550(a)(3)(ii). Use the transmission parameters defined in Table 1 
of Sec.  1036.540 to determine transmission type and gear ratio. For 
Light HDV and Medium HDV, use the Light HDV and Medium HDV parameters 
for FTP, LLC, and SET duty cycles. For Tractors and Heavy HDVs, use the 
Tractor and Heavy HDV transient cycle parameters for the FTP and LLC 
duty cycles and the Tractor and Heavy HDV highway cruise cycle 
parameters for the SET duty cycle.
    (c) Measure emissions using the SET duty cycle shown in Table 1 of 
this section to determine whether engines meet the steady-state 
compression-ignition standards specified in subpart B of this part. 
Table 1 of this section specifies test settings, as follows:
    (1) The duty cycle for testing nonhybrid engines involves a 
schedule of normalized engine speed and torque values. Note that 
nonhybrid powertrains are generally tested as engines, so this section 
does not describe separate procedures for that configuration.
    (2) The duty cycle for testing hybrid engines and hybrid 
powertrains involves a schedule of vehicle speeds and road grade as 
follows:
    (i) Determine road grade at each point based on the continuous 
rated power of the hybrid powertrain system, Pcontrated, in 
kW determined in Sec.  1036.520, the vehicle speed (A, B, or C) in mi/
hr for a given SET mode, vref[speed], and the specified 
road-grade coefficients using the following equation:

[[Page 4519]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.024

Example for SET mode 3a in Table 1 of this section:

Pcontrated = 345.2 kW
vrefB = 59.3 mi/hr
Road grade = 8.296 [middot] 10-\9\ [middot] 345.2\3\ + 
(-4.752 [middot] 10-\7\) [middot] 345.2\2\ 
[middot] 59.3 + 1.291 [middot] 10-\5\ [middot] 345.2\2\ + 
2.88 [middot] 10-\4\ [middot] 59.3\2\ + 4.524 [middot] 
10-\4\ [middot] 345.2 [middot] 59.3 + (-1.802 
[middot] 10-\2\) [middot] 345.2 + (-1.83 [middot] 
10-\1\) [middot] 59.3 + 8.81
Road grade = 0.53%

    (ii) Use the vehicle C speed determined in Sec.  1036.520. 
Determine vehicle A and B speeds as follows:
    (A) Determine vehicle A speed using the following equation:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.025
    
Example:

vrefC = 68.42 mi/hr
[GRAPHIC] [TIFF OMITTED] TR24JA23.026

vrefA = 50.2 mi/hr

    (B) Determine vehicle B speed using the following equation:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.027
    
Example:
[GRAPHIC] [TIFF OMITTED] TR24JA23.028

vrefB = 59.3 mi/hr

    (3) Table 1 follows:
BILLING CODE 6560-50-P

[[Page 4520]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.029

[[Page 4521]]

BILLING CODE 6560-50-C
    (d) Determine criteria pollutant emissions for plug-in hybrid 
engines and powertrains as follows:
    (1) Precondition the engine or powertrain in charge-sustaining 
mode. Perform testing as described in this section for hybrid engines 
and hybrid powertrains in charge-sustaining mode.
    (2) Carry out a charge-depleting test as described in paragraph 
(d)(1) of this section, except as follows:
    (i) Fully charge the RESS after preconditioning.
    (ii) Operate the hybrid engine or powertrain continuously over 
repeated SET duty cycles until you reach the end-of-test criterion 
defined in 40 CFR 1066.501(a)(3).
    (iii) Calculate emission results for each SET duty cycle. Figure 1 
of this section provides an example of a charge-depleting test sequence 
where there are two test intervals that contain engine operation.
    (3) Report the highest emission result for each criteria pollutant 
from all tests in paragraphs (d)(1) and (2) of this section, even if 
those individual results come from different test intervals.
    (4) Figure 1 follows:

Figure 1 to Paragraph (d)(4) of Sec.  1036.510--SET Charge-Depleting 
Criteria Pollutant Test Sequence
[GRAPHIC] [TIFF OMITTED] TR24JA23.030

    (e) Determine greenhouse gas pollutant emissions for plug-in hybrid 
engines and powertrains using the emissions results for all the SET 
test intervals for both charge-depleting and charge-sustaining 
operation from paragraph (d)(2) of this section. Calculate the utility 
factor-weighted composite mass of emissions from the charge-depleting 
and charge-sustaining test results, eUF[emission]comp, using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.031

Where:
i = an indexing variable that represents one test interval.
N = total number of charge-depleting test intervals.
e[emission][int]CDi = total mass of emissions in the 
charge-depleting portion of the test for each test interval, i, 
starting from i = 1, including the test interval(s) from the 
transition phase.
UFDCDi = utility factor fraction at distance 
DCDi from Eq. 1036.510-11, as determined by 
interpolating the approved utility factor curve for each test 
interval, i, starting from i = 1. Let UFDCD0 = 0.
j = an indexing variable that represents one test interval.
M = total number of charge-sustaining test intervals.
e[emission][int]CSj = total mass of emissions 
in the charge-sustaining portion of the test for each test interval, 
j, starting from j = 1.
UFRCD = utility factor fraction at the full charge-
depleting distance, RCD, as determined by interpolating 
the approved utility factor curve. RCD is the cumulative 
distance driven over N charge-depleting test intervals.
[GRAPHIC] [TIFF OMITTED] TR24JA23.032

Where:

k = an indexing variable that represents one recorded velocity 
value.
Q = total number of measurements over the test interval.
v = vehicle velocity at each time step, k, starting from k = 1. For 
tests completed under this section, v is the vehicle velocity from 
the vehicle model in 40 CFR 1037.550. Note that this should

[[Page 4522]]

include charge-depleting test intervals that start when the engine 
is not yet operating.
[Delta]t = 1/frecord
frecord = the record rate.

Example using the charge-depletion test in Figure 1 of Sec.  1036.510 
for the SET for CO2 emission determination:

Q = 24000
v1 = 0 mi/hr
v2 = 0.8 mi/hr
v3 = 1.1 mi/hr
frecord = 10 Hz
[Delta]t = 1/10 Hz = 0.1 s
[GRAPHIC] [TIFF OMITTED] TR24JA23.033

DCD1 = 30.1 mi
DCD2 = 30.0 mi
DCD3 = 30.1 mi
DCD4 = 30.2 mi
DCD5 = 30.1 mi
N = 5
UFDCD1 = 0.11
UFDCD2 = 0.23
UFDCD3 = 0.34
UFDCD4 = 0.45
UFDCD5 = 0.53
eCO2SETCD1 = 0 g/hp[middot]hr
eCO2SETCD2 = 0 g/hp[middot]hr
eCO2SETCD3 = 0 g/hp[middot]hr
eCO2SETCD4 = 0 g/hp[middot]hr
eCO2SETCD5 = 174.4 g/hp[middot]hr
M = 1
eCO2SETCS = 428.1 g/hp[middot]hr
UFRCD = 0.53
[GRAPHIC] [TIFF OMITTED] TR24JA23.034

eUFCO2comp = 215.2 g/hp[middot]hr
    (f) Calculate and evaluate cycle statistics as specified in 40 CFR 
1065.514 for nonhybrid engines and 40 CFR 1037.550 for hybrid engines 
and hybrid powertrains.
    (g) Calculate cycle work for powertrain testing using system power, 
Psys. Determine Psys, using Sec.  1036.520(f).

Sec.  1036.512  Federal Test Procedure.

    (a) Measure emissions using the transient Federal Test Procedure 
(FTP) as described in this section to determine whether engines meet 
the emission standards in subpart B of this part. Operate the engine or 
hybrid powertrain over one of the following transient duty cycles:
    (1) For engines subject to spark-ignition standards, use the 
transient test interval described in paragraph (b) of appendix B of 
this part.
    (2) For engines subject to compression-ignition standards, use the 
transient test interval described in paragraph (c) of appendix B of 
this part.
    (b) The following procedures apply differently for testing engines 
and hybrid powertrains:
    (1) The transient test intervals for nonhybrid engine testing are 
based on normalized speed and torque values. Denormalize speed as 
described in 40 CFR 1065.512. Denormalize torque as described in 40 CFR 
1065.610(d).
    (2) Test hybrid engines and hybrid powertrains as described in 
Sec.  1036.510(b)(2), with the following exceptions:
    (i) Replace Pcontrated with Prated, which is 
the peak rated power determined in Sec.  1036.520.
    (ii) Keep the transmission in drive for all idle segments after the 
initial idle segment.
    (iii) For hybrid engines, select the transmission from Table 1 of 
Sec.  1036.540, substituting ``engine'' for ``vehicle''.
    (iv) For hybrid engines, you may request to change the engine-
commanded torque at idle to better represent curb idle transmission 
torque (CITT).
    (v) For plug-in hybrid engines and powertrains, test over the FTP 
in both charge-sustaining and charge-depleting operation for both 
criteria and greenhouse gas pollutant determination.
    (c) The FTP duty cycle consists of an initial run through the test 
interval from a cold start as described in 40 CFR part 1065, subpart F, 
followed by a (20 1) minute hot soak with no engine 
operation, and then a final hot start run through the same transient 
test interval. Engine starting is part of both the cold-start and hot-
start test intervals. Calculate the total emission mass of each 
constituent, m, and the total work, W, over each test interval as 
described in 40 CFR 1065.650. Calculate total work over each test 
interval for powertrain testing using system power, Psys. 
Determine Psys using Sec.  1036.520(f). For powertrains with 
automatic transmissions, account for and include the work produced by 
the engine from the CITT load. Calculate the official transient 
emission result from the cold-start and hot-start test intervals using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.035

    (d) Determine criteria pollutant emissions for plug-in hybrid 
engines and powertrains as follows:
    (1) Precondition the engine or powertrain in charge-sustaining 
mode. Perform testing as described in this section for hybrid engines 
and hybrid powertrains in charge-sustaining mode.
    (2) Carry out a charge-depleting test as described in paragraph 
(d)(1) of this section, except as follows:
    (i) Fully charge the battery after preconditioning.
    (ii) Operate the hybrid engine or powertrain over one FTP duty 
cycle followed by alternating repeats of a 20-minute soak and a hot 
start test interval

[[Page 4523]]

until you reach the end-of-test criteria defined in 40 CFR 1066.501.
    (iii) Calculate emission results for each successive pair of test 
intervals. Calculate the emission result by treating the first of the 
two test intervals as a cold-start test. Figure 1 of Sec.  1036.512 
provides an example of a charge-depleting test sequence where there are 
three test intervals with engine operation for two overlapping FTP duty 
cycles.
    (3) Report the highest emission result for each criteria pollutant 
from all tests in paragraphs (d)(1) and (2) of this section, even if 
those individual results come from different test intervals.
    (4) Figure 1 follows:

Figure 1 to paragraph (d)(4) of Sec.  1036.512--FTP Charge-Depleting 
Criteria Pollutant Test Sequence.
[GRAPHIC] [TIFF OMITTED] TR24JA23.036

    (e) Determine greenhouse gas pollutant emissions for plug-in hybrid 
engines and powertrains using the emissions results for all the 
transient duty cycle test intervals described in either paragraph (b) 
or (c) of appendix B of this part for both charge-depleting and charge-
sustaining operation from paragraph (d)(2) of this section. Calculate 
the utility factor weighted composite mass of emissions from the 
charge-depleting and charge-sustaining test results, 
eUF[emission]comp, as described in Sec.  1036.510(e), 
replacing occurances of ``SET'' with ``transient test interval''. Note 
this results in composite FTP GHG emission results for plug-in hybrid 
engines and powertrains without the use of the cold-start and hot-start 
test interval weighting factors in Eq. 1036.512-1.
    (f) Calculate and evaluate cycle statistics as specified in 40 CFR 
1065.514 for nonhybrid engines and 40 CFR 1037.550 for hybrid engines 
and hybrid powertrains.

Sec.  1036.514  Low Load Cycle.

    (a) Measure emissions using the transient Low Load Cycle (LLC) as 
described in this section to determine whether engines meet the LLC 
emission standards in Sec.  1036.104.
    (b) The LLC duty cycle is described in paragraph (d) of appendix B 
of this part. The following procedures apply differently for testing 
engines and hybrid powertrains:
    (1) For nonhybrid engine testing, the duty cycle is based on 
normalized speed and torque values.
    (i) Denormalize speed as described in 40 CFR 1065.512. Denormalize 
torque as described in 40 CFR 1065.610(d).
    (ii) For idle segments more than 200 seconds, set reference torques 
to the torque needed to meet the accessory loads in Table 1 of this 
section instead of CITT. This is to represent shifting the transmission 
to park or neutral at the start of the idle segment. Change the 
reference torque to CITT no earlier than 5 seconds before the end of 
the idle segment. This is to represent shifting the transmission to 
drive.
    (2) Test hybrid engines and hybrid powertrains as described in 
Sec.  1036.510(b)(2), with the following exceptions:
    (i) Replace Pcontrated with Prated, which is 
the peak rated power determined in Sec.  1036.520.
    (ii) Keep the transmission in drive for all idle segments 200 
seconds or less. For idle segments more than 200 seconds, place the 
transmission in park or neutral at the start of the idle segment and 
place the transmission into drive again no earlier than 5 seconds 
before the first nonzero vehicle speed setpoint.
    (iii) For hybrid engines, select the transmission from Table 1 of 
Sec.  1036.540, substituting ``engine'' for ``vehicle''.
    (iv) For hybrid engines, you may request to change the engine-
commanded torque at idle to better represent curb idle transmission 
torque (CITT).
    (v) For plug-in hybrid engines and powertrains, determine criteria 
pollutant and greenhouse gas emissions as described in Sec.  
1036.510(d) and (e), replacing ``SET'' with ``LLC''.
    (c) Set dynamometer torque demand such that vehicle power 
represents an accessory load for all idle operation as described in 
Table 1 of paragraph (c)(4) of this section for each primary intended 
service class. Additional provisions related to accessory load apply 
for the following special cases:
    (1) For engines with stop-start technology, account for accessory 
load during engine-off conditions by determining the total engine-off 
power demand over the test interval and distributing that load over the 
engine-on portions of the test interval based on calculated average 
power. You may determine the engine-off time by running practice cycles 
or through engineering analysis.
    (2) Apply accessory loads for hybrid powertrain testing that 
includes the

[[Page 4524]]

transmission either as a mechanical or electrical load.
    (3) You may apply the following deviations from specified torque 
settings for smoother idle (other than idle that includes motoring), or 
you may develop different procedures for adjusting accessory load at 
idle consistent with good engineering judgment:
    (i) Set the reference torque to correspond to the applicable 
accessory load for all points with normalized speed at or below zero 
percent and reference torque from zero up to the torque corresponding 
to the accessory load.
    (ii) Change the reference torques to correspond to the applicable 
accessory load for consecutive points with reference torques from zero 
up to the torque corresponding to the accessory load that immediately 
precedes or follows idle points.
    (4) Table 1 follows:

 Table 1 to Paragraph (c)(4) of Sec.   1036.514--Accessory Load at Idle
------------------------------------------------------------------------
                                                               Power
                                                           representing
             Primary intended service class               accessory load
                                                               (kW)
------------------------------------------------------------------------
Light HDE...............................................             1.5
Medium HDE..............................................             2.5
Heavy HDE...............................................             3.5
------------------------------------------------------------------------

    (d) The test sequence consists of preconditioning the engine by 
running one or two FTPs with each FTP followed by (20 1) 
minutes with no engine operation and a hot start run through the LLC. 
You may start any preconditioning FTP with a hot engine. Perform 
testing as described in 40 CFR 1065.530 for a test interval that 
includes engine starting. Calculate the total emission mass of each 
constituent, m, and the total work, W, as described in 40 CFR 1065.650. 
Calculate total work over the test interval for powertrain testing 
using system power, Psys. Determine Psys using 
Sec.  1036.520(f). For powertrains with automatic transmissions, 
account for and include the work produced by the engine from the CITT 
load. For batch sampling, you may sample background periodically into 
the bag over the course of multiple test intervals.
    (e) Calculate and evaluate cycle statistics as specified in 40 CFR 
1065.514 for nonhybrid engines and 40 CFR 1037.550 for hybrid engines 
and hybrid powertrains. For gaseous-fueled engine testing with a 
single-point fuel injection system, you may apply all the statistical 
criteria in Sec.  1036.540(d)(3) to validate the LLC.

Sec.  1036.520  Determining power and vehicle speed values for 
powertrain testing.

    This section describes how to determine the system peak power and 
continuous rated power of hybrid and nonhybrid powertrain systems and 
the vehicle speed for carrying out duty-cycle testing under this part 
and 40 CFR 1037.550.
    (a) You must map or re-map an engine before a test if any of the 
following apply:
    (1) If you have not performed an initial engine map.
    (2) If the atmospheric pressure near the engine's air inlet is not 
within 5 kPa of the atmospheric pressure recorded at the 
time of the last engine map.
    (3) If the engine or emission-control system has undergone changes 
that might affect maximum torque performance. This includes changing 
the configuration of auxiliary work inputs and outputs.
    (4) If you capture an incomplete map on your first attempt or you 
do not complete a map within the specified time tolerance. You may 
repeat mapping as often as necessary to capture a complete map within 
the specified time.
    (b) Set up the powertrain test according to 40 CFR 1037.550, with 
the following exceptions:
    (1) Use vehicle parameters, other than power, as specified in Sec.  
1036.510(b)(2). Use the applicable automatic transmission as specified 
in Sec.  1036.540(c)(2).
    (2) Select a manufacturer-declared value for Pcontrated 
to represent system peak power.
    (c) Verify the following before the start of each test interval:
    (1) The state-of-charge of the rechargeable energy storage system 
(RESS) must be at or above 90% of the operating range between the 
minimum and maximum RESS energy levels specified by the manufacturer.
    (2) The conditions of all hybrid system components must be within 
their normal operating range as declared by the manufacturer, including 
ensuring that no features are actively limiting power or vehicle speed.
    (d) Carry out the test as described in this paragraph (d). Warm up 
the powertrain by operating it. We recommend operating the powertrain 
at any vehicle speed and road grade that achieves approximately 75% of 
its expected maximum power. Continue the warm-up until the engine 
coolant, block, or head absolute temperature is within 2% 
of its mean value for at least 2 min or until the engine thermostat 
controls engine temperature. Within 90 seconds after concluding the 
warm-up, operate the powertrain over a continuous trace meeting the 
following specifications:
    (1) Bring the vehicle speed to 0 mi/hr and let the powertrain idle 
at 0 mi/hr for 50 seconds.
    (2) Set maximum driver demand for a full load acceleration at 6.0% 
road grade with an initial vehicle speed of 0 mi/hr, continuing for 268 
seconds.
    (3) Linearly ramp the grade from 6.0% down to 0.0% over 300 
seconds. Stop the test 30 seconds after the grade setpoint has reached 
0.0%.
    (e) Record the powertrain system angular speed and torque values 
measured at the dynamometer at 100 Hz and use these in conjunction with 
the vehicle model to calculate vehicle system power, 
Psys,vehicle. Note that Psys, is the 
corresponding value for system power at a location that represents the 
transmission input shaft on a conventional powertrain.
    (f) Calculate the system power, Psys, for each data 
point as follows:
    (1) For testing with the speed and torque measurements at the 
transmission input shaft, Psys is equal to the calculated 
vehicle system power, Psys,vehicle, determined in paragraphs 
(d) and (e) of this section.
    (2) For testing with the speed and torque measurements at the axle 
input shaft or the wheel hubs, determine Psys for each data 
point using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.037

Where:

Psys,vehicle = the calculated vehicle system power for 
each 100-Hz data point.
[egr]trans = the default transmission efficiency = 0.95.
[egr]axle = the default axle efficiency. Set this value 
to 1 for speed and torque measurement at the axle input shaft or to 
0.955 at the wheel hubs.

Example:

Psys,vehicle = 317.6 kW
[GRAPHIC] [TIFF OMITTED] TR24JA23.038

Psys = 350.1 kW
    (g) For each 200-ms (5-Hz) time step, t, determine the coefficient 
of variation (COV) of as follows:
    (1) Calculate the standard deviation, [sigma](t) of the 20 100-Hz 
data points in each 5-Hz measurement interval using the following 
equation:

[[Page 4525]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.039

Where:

N = the number of data points in each 5-Hz measurement interval = 
20.
Psysi = the 100-Hz values of Psys within each 
5-Hz measurement interval.
Psys(t) = the mean power from each 5-Hz measurement 
interval.

    (2) Calculate the 5-Hz values for COV(t) for each time step, t, as 
follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.040

    (h) Determine rated power, Prated, as the maximum 
measured power from the data collected in paragraph (f)(2) of this 
section that meets the specifications in paragraph (g) of this section.
    (i) Determine continuous rated power, Pcontrated, as 
follows:
    (1) For nonhybrid powertrains, Pcontrated equals 
Prated.
    (2) For hybrid powertrains, Pcontrated is the maximum 
measured power from the data collected in paragraph (d)(3) of this 
section that meets the specifications in paragraph (g) of this section.
    (j) Determine vehicle C speed, vrefC, as follows:
    (1) If the maximum Psys(t) in the highest gear during 
the maneuver in paragraph (d)(3) of this section is greater than 
0.98[middot]Pcontrated, vrefC is the average of 
the minimum and maximum vehicle speeds where Psys(t) is 
equal to 0.98[middot]Pcontrated during the maneuver in 
paragraph (d)(3) of this section where the transmission is in the 
highest gear, using linear interpolation, as appropriate.
    (2) Otherwise, vrefC is the maximum vehicle speed during 
the maneuver in paragraph (d)(3) where the transmission is in the 
highest gear.
    (k) If Pcontrated as determined in paragraph (i) of this 
section is within 3% of the manufacturer-declared value for 
Pcontrated, use the manufacturer-declared value. Otherwise, 
repeat the procedure in paragraphs (b) through (j) of this section and 
use Pcontrated from paragraph (i) instead of the 
manufacturer-declared value.

Sec.  1036.525  Clean Idle test.

    Measure emissions using the procedures described in this section to 
determine whether engines and hybrid powertrains meet the clean idle 
emission standards in Sec.  1036.104(b). For plug-in hybrid engines and 
powertrains, perform the test with the hybrid function disabled.
    (a) The clean idle test consists of two separate test intervals as 
follows:
    (1) Mode 1 consists of engine operation with a speed setpoint at 
your recommended warm idle speed. Set the dynamometer torque demand 
corresponding to vehicle power requirements at your recommended warm 
idle speed that represent in-use operation.
    (2) Mode 2 consists of engine operation with a speed setpoint at 
1100 r/min. Set the dynamometer torque demand to account for the sum of 
the following power loads:
    (i) Determine power requirements for idling at 1100 r/min.
    (ii) Apply a power demand of 2 kW to account for appliances and 
accessories the vehicle operator may use during rest periods.
    (3) Determine torque demand for testing under this paragraph (a) 
based on an accessory load that includes the engine cooling fan, 
alternator, coolant pump, air compressor, engine oil and fuel pumps, 
and any other engine accessory that operates at the specific test 
condition. Also include the accessory load from the air conditioning 
compressor operating at full capacity for Mode 2. Do not include any 
other load for air conditioning or other cab or vehicle accessories 
except as specified.
    (b) Perform the Clean Idle test as follows:
    (1) Warm up the engine by operating it over the FTP or SET duty 
cycle, or by operating it at any speed above peak-torque speed and at 
(65 to 85) % of maximum mapped power. The warm-up is complete when the 
engine thermostat controls engine temperature or when the engine 
coolant's temperature is within 2% of its mean value for at least 2 
minutes.
    (2) Start operating the engine in Mode 1 as soon as practical after 
the engine warm-up is complete.
    (3) Start sampling emissions 10 minutes after reaching the speed 
and torque setpoints and continue emission sampling and engine 
operation at those setpoints. Stop emission sampling after 1200 seconds 
to complete the test interval.
    (4) Linearly ramp the speed and torque setpoints over 5 seconds to 
start operating the engine in Mode 2. Sample emissions during Mode 2 as 
described in paragraph (b)(3) of this section.
    (c) Verify that the test speed stays within 50 r/min of 
the speed setpoint throughout the test. The torque tolerance is 2 percent of the maximum mapped torque at the test speed. Verify 
that measured torque meets the torque tolerance relative to the torque 
setpoint throughout the test.
    (d) Calculate the mean mass emission rate of NOX, mi, 
over each test interval by calculating the total emission mass mi 
NOx and dividing by the total time.

Sec.  1036.530  Test procedures for off-cycle testing.

    (a) General. This section describes the measurement and calculation 
procedures to perform field testing and determine whether tested 
engines and engine families meet emission standards under subpart E of 
this part. Calculate mass emission rates as specified in 40 CFR part 
1065, subpart G. Use good engineering judgment to adapt these 
procedures for simulating vehicle operation in the laboratory.
    (b) Vehicle preparation and measurement procedures. (1) Set up the 
vehicle for testing with a portable emissions measurement system (PEMS) 
as specified in 40 CFR part 1065, subpart J.
    (2) Begin emission sampling and data collection as described in 40 
CFR 1065.935(c)(3) before starting the engine at the beginning of the 
shift-day. Start the engine only after confirming that engine coolant 
temperature is at or below 40 [deg]C.
    (3) Measure emissions over one or more shift-days as specified in 
subpart E of this part.
    (4) For engines subject to compression-ignition standards, record 1 
Hz measurements of ambient temperature near the vehicle.
    (c) Test Intervals. Determine the test intervals as follows:
    (1) Spark-ignition. Create a single test interval that covers the 
entire shift-day for engines subject to spark-ignition standards. The 
test interval starts with the first pair of consecutive data points 
with no exclusions as described in paragraph (c)(3) of this section 
after the start of the shift-day and ends with the last pair of 
consecutive data points with no exclusions before the end of the shift 
day.
    (2) Compression-ignition. Create a series of 300 second test 
intervals for engines subject to compression-ignition standards 
(moving-average windows) as follows:
    (i) Begin and end each test interval with a pair of consecutive 
data points with no exclusions as described in paragraph (c)(3) of this 
section. Select the last data point of each test interval such that the 
test interval includes 300 seconds of data with no exclusions, as 
described in paragraph (d) of this section. The test interval may be a 
fraction of a second more or less than 300 seconds to account for the 
precision

[[Page 4526]]

of the time stamp in recording 1 Hz data. A test interval may include 
up to 599 seconds of data with continuous exclusions; invalidate any 
test interval that includes at least 600 seconds of continuous sampling 
with excluded data.
    (ii) The first 300 second test interval starts with the first pair 
of consecutive data points with no exclusions. Determine the start of 
each subsequent 300 second test interval by finding the first pair of 
consecutive data points with no exclusions after the initial data point 
of the previous test interval.
    (iii) The last 300 second test interval ends with the last pair of 
consecutive data points with no exclusions before the end of the shift 
day.
    (3) Excluded data. Exclude data from test intervals for any period 
meeting one or more of the following conditions:
    (i) An analyzer or flow meter is performing zero and span drift 
checks or zero and span calibrations, including any time needed for the 
analyzer to stabilize afterward, consistent with good engineering 
judgment.
    (ii) The engine is off, except as specified in Sec.  1036.415(g).
    (iii) The engine is performing an infrequent regeneration. Do not 
exclude data related to any other AECDs, except as specified in 
paragraph (c)(3)(vi) of this section.
    (iv) The recorded ambient air temperature is below 5 [deg]C or 
above the temperature calculated using the following equation.
[GRAPHIC] [TIFF OMITTED] TR24JA23.041

Where:

h = recorded elevation of the vehicle in feet above sea level (h is 
negative for elevations below sea level).

Example:

h = 2679 ft
Tmax = -0.0014[middot]2679 + 37.78
Tmax = 34.0 [deg]C
    (v) The vehicle is operating at an elevation more than 5,500 feet 
above sea level.
    (vi) An engine has one or more active AECDs for emergency vehicles 
under Sec.  1036.115(h)(4).
    (vii) A single data point does not meet any of the conditions 
specified in paragraphs (c)(3)(i) through (vi) of this section, but it 
is preceded and followed by data points that both meet one or more of 
the specified exclusion conditions.
    (d) Assembling test intervals. A test interval may include multiple 
subintervals separated by periods with one or more exclusions under 
paragraph (c)(3) of this section.
    (1) Treat these test subintervals as continuous for calculating 
duration of the test interval for engines subject to compression-
ignition standards.
    (2) Calculate emission mass during each test subinterval and sum 
those subinterval emission masses to determine the emission mass over 
the test interval. Calculate emisson mass as described in 40 CFR 
1065.650(c)(2)(i), with the following exceptions and clarifications:
    (i) Correct NOX emissions for humidity as specified in 
40 CFR 1065.670. Calculate corrections relative to ambient air humidity 
as measured by PEMS.
    (ii) Disregard the provision in 40 CFR 1065.650(g) for setting 
negative emission mass to zero for test intervals and subintervals.
    (iii) Calculation of emission mass in 40 CFR 1065.650 assumes a 
constant time interval, [Delta]t. If it is not appropriate to assume 
[Delta]t is constant for testing under this section, use good 
engineering judgment to record time at each data point and adjust the 
mass calculation from Eq. 1065.650-4 by treating [Delta]t as a 
variable.
    (e) Normalized CO2 emission mass over a 300 second test 
interval. For engines subject to compression-ignition standards, 
determine the normalized CO2 emission mass over each 300 
second test interval, mCO2,norm,testinterval, to the nearest 
0.01% using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.042

Where:

mCO2,testinterval = total CO2 emission mass 
over the test interval.
eCO2FTPFCL = the engine's FCL for CO2 over the 
FTP duty cycle. If the engine family includes no FTP testing, use 
the engine's FCL for CO2 over the SET duty cycle.
Pmax = the highest value of rated power for all the 
configurations included in the engine family.
ttestinterval = duration of the test interval. Note that 
the nominal value is 300 seconds.

Example:

mCO2,testinterval = 3948 g
eCO2FTPFCL = 428.2 g/hp[middot]hrPmax = 406.5 hp
    ttestinterval = 300.01 s = 0.08 hr
    [GRAPHIC] [TIFF OMITTED] TR24JA23.043
    
mCO2,norm,testinterval = 0.2722 = 27.22%

    (f) Binning 300 second test intervals. For engines subject to 
compression-ignition standards, identify the appropriate bin for each 
of the 300 second test intervals based on its normalized CO2 
emission mass, mCO2,norm,testinterval, as follows:

Table 1 to Paragraph (f) of Sec.   1036.530--Criteria for Off-Cycle Bins
------------------------------------------------------------------------
                                            Normalized CO2 emission mass
                    Bin                       over the 300 second test
                                                      interval
------------------------------------------------------------------------
Bin 1.....................................  mCO2,norm,testinterval <=
                                             6.00%.
Bin 2.....................................  mCO2,norm,testinterval >
                                             6.00%.
------------------------------------------------------------------------

    (g) Off-cycle emissions quantities. Determine the off-cycle 
emissions quantities as follows:
    (1) Spark-ignition. For engines subject to spark-ignition 
standards, the off cycle emission quantity, 
e[emission],offcycle, is the value for CO2-
specific emission mass for a given pollutant over the test interval 
representing the shift-day converted to a brake-specific value, as 
calculated for

[[Page 4527]]

each measured pollutant using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.044

Where:

m[emission] = total emission mass for a given pollutant 
over the test interval as determined in paragraph (d)(2) of this 
section.
mCO2 = total CO2 emission mass over the test 
interval as determined in paragraph (d)(2) of this section.
eCO2FTPFCL = the engine's FCL for CO2 over the 
FTP duty cycle.

Example:

mNOx = 1.337 g
mCO2 = 18778 g
eCO2FTPFCL = 505.1 g/hp[middot]hr
[GRAPHIC] [TIFF OMITTED] TR24JA23.045

eNOx,offcycle = 0.035 g/hp[middot]hr

    (2) Compression-ignition. For engines subject to compression-
ignition standards, determine the off-cycle emission quantity for each 
bin. When calculating mean bin emissions from ten engines to apply the 
pass criteria for engine families in Sec.  1036.425(c), set any 
negative off-cycle emissions quantity to zero before calculating mean 
bin emissions.
    (i) Off-cycle emissions quantity for bin 1. The off-cycle emission 
quantity for bin 1, miNOx,offcycle,bin1, is the mean 
NOX mass emission rate from all test intervals associated 
with bin 1 as calculated using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.046

Where:

i = an indexing variable that represents one 300 second test 
interval.
N = total number of 300 second test intervals in bin 1.
mNOXtestinterval,i = total 
NOX emission mass over the test interval i in bin 1 as 
determined in paragraph (d)(2) of this section.
ttestinterval,i = total time of test interval 
i in bin 1 as determined in paragraph (d)(1) of this section. Note 
that the nominal value is 300 seconds.

Example:

N = 10114
mNOX,testinterval,1 = 0.021 g
mNOX,testinterval,2 = 0.025 g
mNOX,testinterval,3 = 0.031 g
ttestinterval,1 = 299.99 s
ttestinterval,2 = 299.98 s
ttestinterval,3 = 300.04 s
[GRAPHIC] [TIFF OMITTED] TR24JA23.047

miNOoffcycle,bin1, = 0.000285 g/s = 1.026 g/hr

    (ii) Off-cycle emissions quantity for bin 2. The off-cycle emission 
quantity for bin 2, e[emission],offcycle,bin2, is the value 
for CO2-specific emission mass for a given pollutant of all 
the 300 second test intervals in bin 2 combined and converted to a 
brake-specific value, as calculated for each measured pollutant using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.048

Where:

i = an indexing variable that represents one 300 second test 
interval.
N = total number of 300 second test intervals in bin 2.
m[emission],testinterval,i = total emission 
mass for a given pollutant over the test interval i in bin 2 as 
determined in paragraph (d)(2) of this section.
mCOX,testinterval,i = total 
CO2 emission mass over the test interval i in bin 2 as 
determined in paragraph (d)(2) of this section.
eCO2FTPFCL = the engine's FCL for CO2 over the 
FTP duty cycle.

Example:

N = 15439
mNOX1 = 0.546 g
mNOX2 = 0.549 g
mNOX3 = 0.556 g
mCOX1 = 10950.2 g
mCOX2 = 10961.3 g
mCOX3 = 10965.3 g
eCOX FTPFCL = 428.1 g/hp[middot]hr

[[Page 4528]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.049

    eNOX,offcycle,bin2 = 0.026 g/hp[middot]hr

    (h) Shift-day ambient temperature. For engines subject to 
compression-ignition standards, determine the mean shift-day ambient 
temperature, Tiamb, considering only temperature readings 
corresponding to data with no exclusions under paragraph (c)(3) of this 
section.
    (i) Graphical illustration. Figure 1 of this section illustrates a 
test interval with interruptions of one or more data points excluded 
under paragraph (c)(3) of this section. The x-axis is time and the y-
axis is the mass emission rate at each data point, m(t) The data points 
coincident with any exclusion are illustrated with open circles. The 
shaded area corresponding to each group of closed circles represents 
the total emission mass over that test subinterval. Note that negative 
values of m(t) are retained and not set to zero in the numerical 
integration calculation. The first group of data points without any 
exclusions is referred to as the first test subinterval and so on.

Figure 1 to Paragraph (i) of Sec.  1036.530--Illustration of 
Integration of Mass of Emissions Over a Test Interval With Exclude Data 
Points
[GRAPHIC] [TIFF OMITTED] TR24JA23.050

Sec.  1036.535  Determining steady-state engine fuel maps and fuel 
consumption at idle.

    The procedures in this section describe how to determine an 
engine's steady-state fuel map and fuel consumption at idle for model 
year 2021 and later vehicles; these procedures apply as described in 
Sec.  1036.505. Vehicle manufacturers may need these values to 
demonstrate compliance with emission standards under 40 CFR part 1037.
    (a) General test provisions. Perform fuel mapping using the 
procedure described in paragraph (b) of this section to establish 
measured fuel-consumption rates at a range of engine speed and load 
settings. Measure fuel consumption at idle using the procedure 
described in paragraph (c) of this section. Paragraph (d) of this 
section describes how to apply the steady-state mapping from paragraph 
(b) of this section for the special case of cycle-average mapping for 
highway cruise cycles as described in Sec.  1036.540. Use these 
measured fuel-consumption values to declare fuel-consumption rates for 
certification as described in paragraph (g) of this section.
    (1) Map the engine's torque curve and declare engine idle speed as 
described in Sec.  1036.505(c)(1) and (3). Perform emission 
measurements as described in 40 CFR 1065.501 and 1065.530 for discrete-
mode steady-state testing. This section uses engine parameters and 
variables that are consistent with 40 CFR part 1065.
    (2) Measure NOX emissions as described in paragraph (f) 
of this section. Include these measured NOX values any time 
you report to us your fuel consumption values from testing under this 
section.
    (3) You may use shared data across engine configurations to the 
extent that the fuel-consumption rates remain valid.
    (4) The provisions related to carbon balance error verification in 
Sec.  1036.543 apply for all testing in this section. These procedures 
are optional, but we will perform carbon balance error verification for 
all testing under this section.
    (5) Correct fuel mass flow rate to a mass-specific net energy 
content of a reference fuel as described in paragraph (e) of this 
section.
    (b) Steady-state fuel mapping. Determine steady-state fuel-
consumption rates for each engine configuration over a series of paired 
engine speed and torque setpoints as described in this paragraph (b). 
For example, if you test a high-output (parent) configuration and 
create a different (child) configuration that uses the same fueling 
strategy but limits the engine operation to be a subset of that from 
the high-output configuration, you may use the fuel-consumption rates 
for the reduced number of mapped points for the low-output 
configuration, as long as the narrower map includes at least 70 points. 
Perform fuel mapping as follows:
    (1) Generate the fuel-mapping sequence of engine speed and torque 
setpoints as follows:
    (i) Select the following required speed setpoints: warm idle speed, 
fnidle the highest speed above maximum power at which 70% of 
maximum power occurs, nhi, and eight (or more) equally 
spaced points between fnidle and nhi. (See 40 CFR 
1065.610(c)). For engines with adjustable warm idle speed, replace 
fnidle with minimum warm idle speed fnidlemin.
    (ii) Determine the following default torque setpoints at each of 
the selected

[[Page 4529]]

speed setpoints: zero (T = 0), maximum mapped torque, 
Tmax mapped, and eight (or more) equally spaced points 
between T = 0 and Tmax mapped. Select the maximum torque 
setpoint at each speed to conform to the torque map as follows:
    (A) Calculate 5 percent of Tmax mapped. Subtract this 
result from the mapped torque at each speed setpoint, Tmax.
    (B) Select Tmax at each speed setpoint as a single 
torque value to represent all the default torque setpoints above the 
value determined in paragraph (b)(1)(ii)(A) of this section. All the 
default torque setpoints less than Tmax at a given speed 
setpoint are required torque setpoints.
    (iii) You may select any additional speed and torque setpoints 
consistent with good engineering judgment. For example you may need to 
select additional points if the engine's fuel consumption is nonlinear 
across the torque map. Avoid creating a problem with interpolation 
between narrowly spaced speed and torque setpoints near 
Tmax. For each additional speed setpoint, we recommend 
including a torque setpoint of Tmax; however, you may select 
torque setpoints that properly represent in-use operation. Increments 
for torque setpoints between these minimum and maximum values at an 
additional speed setpoint must be no more than one-ninth of 
Tmax,mapped. Note that if the test points were added for the 
child rating, they should still be reported in the parent fuel map. We 
will test with at least as many points as you. If you add test points 
to meet testing requirements for child ratings, include those same test 
points as reported values for the parent fuel map. For our testing, we 
will use the same normalized speed and torque test points you use, and 
we may select additional test points.
    (iv) Start fuel-map testing at the highest speed setpoint and 
highest torque setpoint, followed by decreasing torque setpoints at the 
highest speed setpoint. Continue testing at the next lowest speed 
setpoint and the highest torque setpoint at that speed setpoint, 
followed by decreasing torque setpoints at that speed setpoint. Follow 
this pattern through all the speed and torque points, ending with the 
lowest speed (fnidle or fnidlemin) and torque 
setpoint (T = 0). The following figure illustrates an array of test 
points and the corresponding run order.

Figure 1 to Paragraph (b)(1)(iv) of Sec.  1036.535--Illustration of 
Steady-State Fuel-Mapping Test Points and Run Order
[GRAPHIC] [TIFF OMITTED] TR24JA23.051

    (v) The highest torque setpoint for each speed setpoint is an 
optional reentry point to restart fuel mapping after an incomplete test 
run.
    (vi) The lowest torque setpoint at each speed setpoint is an 
optional exit point to interrupt testing. Paragraph (b)(7) of this 
section describes how to interrupt testing at other times.
    (2) If the engine's warm idle speed is adjustable, set it to its 
minimum value, fnidlemin.
    (3) The measurement at each unique combination of speed and torque 
setpoints constitutes a test interval. Unless we specify otherwise, you 
may program the dynamometer to control either speed or torque for a 
given test interval, with operator demand controlling the other 
parameter. Control speed and torque so that all recorded speed points 
are within 1% of nhi from the target speed and 
all recorded engine

[[Page 4530]]

torque points are within 5% of Tmax mapped from 
the target torque during each test interval, except as follows:
    (i) For steady-state engine operating points that cannot be 
achieved, and the operator demand stabilizes at minimum; program the 
dynamometer to control torque and let the engine govern speed (see 40 
CFR 1065.512(b)(1)). Control torque so that all recorded engine torque 
points are within 25 N[middot]m from the target torque. The 
specified speed tolerance does not apply for the test interval.
    (ii) For steady-state engine operating points that cannot be 
achieved and the operator demand stabilizes at maximum and the speed 
setpoint is below 90% of nhi even with maximum operator 
demand, program the dynamometer to control speed and let the engine 
govern torque (see 40 CFR 1065.512(b)(2)). The specified torque 
tolerance does not apply for the test interval.
    (iii) For steady-state engine operating points that cannot be 
achieved and the operator demand stabilizes at maximum and the speed 
setpoint is at or above 90% of nhi even with maximum 
operator demand, program the dynamometer to control torque and let the 
engine govern speed (see 40 CFR 1065.512(b)(1)). The specified speed 
tolerance does not apply for the test interval.
    (iv) For the steady-state engine operating points at the minimum 
speed setpoint and maximum torque setpoint, you may program the 
dynamometer to control speed and let the engine govern torque. The 
specified torque tolerance does not apply for this test interval if 
operator demand stabilizes at its maximum or minimum limit.
    (4) Record measurements using direct and/or indirect measurement of 
fuel flow as follows:
    (i) Direct fuel-flow measurement. Record speed and torque and 
measure fuel consumption with a fuel flow meter for (30  1) 
seconds. Determine the corresponding mean values for the test interval. 
Use of redundant direct fuel-flow measurements requires our advance 
approval.
    (ii) Indirect fuel-flow measurement. Record speed and torque and 
measure emissions and other inputs needed to run the chemical balance 
in 40 CFR 1065.655(c) for (30  1) seconds. Determine the 
corresponding mean values for the test interval. Use of redundant 
indirect fuel-flow measurements requires our advance approval. Measure 
background concentration as described in 40 CFR 1065.140, except that 
you may use one of the following methods to apply a single background 
reading to multiple test intervals:
    (A) For batch sampling, you may sample periodically into the bag 
over the course of multiple test intervals and read them as allowed in 
paragraph (b)(7)(i) of this section. You must determine a single 
background reading for all affected test intervals if you use the 
method described in this paragraph (b)(4)(ii)(A).
    (B) You may measure background concentration by sampling from the 
dilution air during the interruptions allowed in paragraph (b)(7)(i) of 
this section or at other times before or after test intervals. Measure 
background concentration within 30 minutes before the first test 
interval and within 30 minutes before each reentry point. Measure the 
corresponding background concentration within 30 minutes after each 
exit point and within 30 minutes after the final test interval. You may 
measure background concentration more frequently. Correct measured 
emissions for test intervals between a pair of background readings 
based on the average of those two values. Once the system stabilizes, 
collect a background sample over an averaging period of at least 30 
seconds.
    (5) Warm up the engine as described in 40 CFR 1065.510(b)(2). 
Within 60 seconds after concluding the warm-up, linearly ramp the speed 
and torque setpoints over 5 seconds to the starting test point from 
paragraph (b)(1) of this section.
    (6) Stabilize the engine by operating at the specified speed and 
torque setpoints for (70  1) seconds and then start the 
test interval. Record measurements during the test interval. Measure 
and report NOX emissions over each test interval as 
described in paragraph (f) of this section.
    (7) After completing a test interval, linearly ramp the speed and 
torque setpoints over 5 seconds to the next test point.
    (i) You may interrupt the fuel-mapping sequence before a reentry 
point as noted in paragraphs (b)(1)(v) and (vi) of this section. If you 
zero and span analyzers, read and evacuate background bag samples, or 
sample dilution air for a background reading during the interruption, 
the maximum time to stabilize in paragraph (b)(6) of this section does 
not apply. If you shut off the engine, restart with engine warm-up as 
described in paragraph (b)(5) of this section.
    (ii) You may interrupt the fuel-mapping sequence at a given speed 
setpoint before completing measurements at that speed. If this happens, 
you may measure background concentration and take other action as 
needed to validate test intervals you completed before the most recent 
reentry point. Void all test intervals after the last reentry point. 
Restart testing at the appropriate reentry point in the same way that 
you would start a new test. Operate the engine long enough to stabilize 
aftertreatment thermal conditions, even if it takes more than 70 
seconds. In the case of an infrequent regeneration event, interrupt the 
fuel-mapping sequence and allow the regeneration event to finish with 
the engine operating at a speed and load that allows effective 
regeneration.
    (iii) If you void any one test interval, all the testing at that 
speed setpoint is also void. Restart testing by repeating the fuel-
mapping sequence as described in this paragraph (b); include all voided 
speed setpoints and omit testing at speed setpoints that already have a 
full set of valid results.
    (8) If you determine fuel-consumption rates using emission 
measurements from the raw or diluted exhaust, calculate the mean fuel 
mass flow rate, mifuel, for each point in the fuel map using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.052

Where:

mifuel = mean fuel mass flow rate for a given fuel map 
setpoint, expressed to at least the nearest 0.001 g/s.
MC = molar mass of carbon.
wCmeas = carbon mass fraction of fuel (or mixture of test 
fuels) as determined in 40 CFR 1065.655(d), except that you may not 
use the default properties in Table 2 of 40 CFR 1065.655 to 
determine [alpha], [beta], and wC. You may not account 
for the contribution to [alpha], [beta], [gamma], and [delta] of 
diesel exhaust fluid or other non-fuel fluids injected into the 
exhaust.

[[Page 4531]]

niexh = the mean raw exhaust molar flow rate from which 
you measured emissions according to 40 CFR 1065.655.
xCcombdry = the mean concentration of carbon from fuel 
and any injected fluids in the exhaust per mole of dry exhaust as 
determined in 40 CFR 1065.655(c).
xH2Oexhdry = the mean concentration of H2O in 
exhaust per mole of dry exhaust as determined in 40 CFR 1065.655(c).
miCO2DEF = the mean CO2 mass emission rate 
resulting from diesel exhaust fluid decomposition as determined in 
paragraph (b)(9) of this section. If your engine does not use diesel 
exhaust fluid, or if you choose not to perform this correction, set 
miCO2DEF equal to 0.
MCO2 = molar mass of carbon dioxide.

Example:

MC = 12.0107 g/mol
wCmeas = 0.869
niexh = 25.534 mol/s
xCcombdry = 0.002805 mol/mol
xH2Oexhdry = 0.0353 mol/mol
miCO2DEF = 0.0726 g/s
MCO2 = 44.0095 g/mol
[GRAPHIC] [TIFF OMITTED] TR24JA23.053

mifuel = 0.933 g/s

    (9) If you determine fuel-consumption rates using emission 
measurements with engines that utilize diesel exhaust fluid for 
NOX control and you correct for the mean CO2 mass 
emission rate resulting from diesel exhaust fluid decomposition as 
described in paragraph (b)(8) of this section, perform this correction 
at each fuel map setpoint using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.054

Where:

miDEF = the mean mass flow rate of injected urea solution 
diesel exhaust fluid for a given sampling period, determined 
directly from the ECM, or measured separately, consistent with good 
engineering judgment.
MCO2 = molar mass of carbon dioxide.
wCH4N2O = mass fraction of urea in diesel exhaust fluid 
aqueous solution. Note that the subscript ``CH4N2O'' refers to urea 
as a pure compound and the subscript ``DEF'' refers to the aqueous 
urea diesel exhaust fluid as a solution of urea in water. You may 
use a default value of 32.5% or use good engineering judgment to 
determine this value based on measurement.
MCH4N2O = molar mass of urea.

Example:

miDEF = 0.304 g/s
MCO2 = 44.0095 g/mol
wCH4N2O = 32.5% = 0.325
MCH4N2O = 60.05526 g/mol
[GRAPHIC] [TIFF OMITTED] TR24JA23.055

miCO2DEF = 0.0726 g/s

    (10) Correct the measured or calculated mean fuel mass flow rate, 
at each of the engine-idle operating points to account for mass-
specific net energy content as described in paragraph (e) of this 
section.
    (c) Fuel consumption at idle. Determine fuel-consumption rates at 
idle for each engine configuration that is certified for installation 
in vocational vehicles. Determine fuel-consumption rates at idle by 
testing engines over a series of paired engine speed and torque 
setpoints as described in this paragraph (c). Perform measurements as 
follows:
    (1) The idle test sequence consists of measuring fuel consumption 
at four test points representing each combination of the following 
speed and torque setpoints in any order.
    (i) Speed setpoints for engines with adjustable warm idle speed are 
minimum warm idle speed, fnidlemin, and maximum warm idle 
speed, fnidlemax. Speed setpoints for engines with no 
adjustable warm idle speed (with zero torque on the primary output 
shaft) are fnidle and 1.15 times fnidle.
    (ii) Torque setpoints are 0 and 100 N[middot]m.
    (2) Control speed and torque as follows:
    (i) Adjustable warm idle speed. Set the engine's warm idle speed to 
the next speed setpoint any time before the engine reaches the next 
test point. Control both speed and torque when the engine is warming up 
and when it is transitioning to the next test point. Start to control 
both speed and torque. At any time prior to reaching the next engine-
idle operating point, set the engine's adjustable warm idle speed 
setpoint to the speed setpoint of the next engine-idle operating point 
in the sequence. This may be done before or during the warm-up or 
during the transition. Near the end of the transition period control 
speed and torque as described in paragraph (b)(3)(i) of this section 
shortly before reaching each test point. Once the engine is operating 
at the desired speed and torque setpoints, set the operator demand to 
minimum; control torque so that all recorded engine torque points are 
within 25 N[middot]m from the target torque.
    (ii) Nonadjustable warm idle speed. For the lowest speed setpoint, 
control speed and torque as described in paragraph (c)(2)(i) of this 
section, except for adjusting the warm idle speed. For the second-
lowest speed setpoint, control speed and torque so that all recorded 
speed points are within 1% of nhi from the 
target speed and engine torque within 5% of 
Tmax mapped from the target torque.
    (3) Record measurements using direct and/or indirect measurement of 
fuel flow as follows:
    (i) Direct fuel flow measurement. Record speed and torque and 
measure fuel consumption with a fuel flow meter for (600 1) 
seconds. Determine the corresponding mean values for the test interval. 
Use of redundant direct fuel-flow measurements require prior EPA 
approval.

[[Page 4532]]

    (ii) Indirect fuel flow measurement. Record speed and torque and 
measure emissions and other inputs needed to run the chemical balance 
in 40 CFR 1065.655(c) for (600 1) seconds. Determine the 
corresponding mean values for the test interval. Use of redundant 
indirect fuel-flow measurements require prior EPA approval. Measure 
background concentration as described in paragraph (b)(4)(ii) of this 
section. We recommend setting the CVS flow rate as low as possible to 
minimize background, but without introducing errors related to 
insufficient mixing or other operational considerations. Note that for 
this testing 40 CFR 1065.140(e) does not apply, including the minimum 
dilution ratio of 2:1 in the primary dilution stage.
    (4) Warm up the engine as described in 40 CFR 1065.510(b)(2). 
Within 60 seconds after concluding the warm-up, linearly ramp the speed 
and torque over 20 seconds to the first speed and torque setpoint.
    (5) The measurement at each unique combination of speed and torque 
setpoints constitutes a test interval. Operate the engine at the 
selected speed and torque set points for (180 1) seconds, 
and then start the test interval. Record measurements during the test 
interval. Measure and report NOX emissions over each test 
interval as described in paragraph (f) of this section.
    (6) After completing each test interval, repeat the steps in 
paragraphs (c)(4) and (5) of this section for all the remaining engine-
idle test points.
    (7) Each test point represents a stand-alone measurement. You may 
therefore take any appropriate steps between test intervals to process 
collected data and to prepare engines and equipment for further 
testing. Note that the allowances for combining background in paragraph 
(b)(4)(ii)(B) of this section do not apply. If an infrequent 
regeneration event occurs, allow the regeneration event to finish; void 
the test interval if the regeneration starts during a measurement.
    (8) Correct the measured or calculated mean fuel mass flow rate, at 
each of the engine-idle operating points to account for mass-specific 
net energy content as described in paragraph (e) of this section.
    (d) Steady-state fuel maps used for cycle-average fuel mapping of 
the highway cruise cycles. Determine steady-state fuel-consumption 
rates for each engine configuration over a series of paired engine 
speed and torque setpoints near idle as described in this paragraph 
(d). Perform fuel mapping as described in paragraph (b) of this section 
with the following exceptions:
    (1) Select speed setpoints to cover a range of values to represent 
in-use operation at idle. Speed setpoints for engines with adjustable 
warm idle speed must include at least minimum warm idle speed, 
fnidlemin, and a speed at or above maximum warm idle speed, 
fnidlemax. Speed setpoints for engines with no adjustable 
idle speed must include at least warm idle speed (with zero torque on 
the primary output shaft), fnidle, and a speed at or above 
1.15 [middot] fnidle.
    (2) Select the following torque setpoints at each speed setpoint to 
cover a range of values to represent in-use operation at idle:
    (i) The minimum torque setpoint is zero.
    (ii) Choose a maximum torque setpoint that is at least as large as 
the value determined by the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.056

Where:

Tfnstall = the maximum engine torque at 
fnstall.
fnidle = for engines with an adjustable warm idle speed, 
use the maximum warm idle speed, fnidlemax. For engines 
without an adjustable warm idle speed, use warm idle speed, 
fnidle.
fnstall = the stall speed of the torque converter; use 
fntest or 2250 r/min, whichever is lower.
Pacc = accessory power for the vehicle class; use 1500 W 
for Vocational Light HDV, 2500 W for Vocational Medium HDV, and 3500 
W for Tractors and Vocational Heavy HDV. If your engine is going to 
be installed in multiple vehicle classes, perform the test with the 
accessory power for the largest vehicle class the engine will be 
installed in.

Example:

Tfnstall = 1870 N[middot]m
fntest = 1740.8 r/min = 182.30 rad/s
fnstall = 1740.8 r/min = 182.30 rad/s
fnidle = 700 r/min = 73.30 rad/s
Pacc = 1500 W
[GRAPHIC] [TIFF OMITTED] TR24JA23.057

Tidlemaxest = 355.07 N[middot]m

    (iii) Select one or more equally spaced intermediate torque 
setpoints, as needed, such that the increment between torque setpoints 
is no greater than one-ninth of Tmax,mapped.
    (e) Correction for net energy content. Correct the measured or 
calculated mean fuel mass flow rate, , for each test interval to a 
mass-specific net energy content of a reference fuel using the 
following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.058

Where:

Emfuelmeas = the mass-specific net energy content of the 
test fuel as determined in Sec.  1036.550(b)(1).
EmfuelCref = the reference value of carbon-mass-specific 
net energy content for the appropriate fuel. Use the values shown in 
Table 1 in Sec.  1036.550 for the designated fuel types, or values 
we approve for other fuel types.
wCref = the reference value of carbon mass fraction for 
the test fuel as shown in Table 1 of Sec.  1036.550 for the 
designated fuels. For any fuel not identified in the table, use the 
reference carbon mass fraction of diesel fuel for engines subject to 
compression-ignition standards, and use the reference carbon mass 
fraction of gasoline for engines subject to spark-ignition 
standards.

Example:

mifuel = 0.933 g/s
Emfuelmeas = 42.7984 MJ/kgC
EmfuelCref = 49.3112 MJ/kgC

[[Page 4533]]

wCref = 0.874
[GRAPHIC] [TIFF OMITTED] TR24JA23.059

mifuel = 0.927 g/s

    (f) Measuring NOX emissions. Measure NOX emissions for 
each sampling period in g/s. You may perform these measurements using a 
NOX emission-measurement system that meets the requirements 
of 40 CFR part 1065, subpart J. If a system malfunction prevents you 
from measuring NOX emissions during a test under this 
section but the test otherwise gives valid results, you may consider 
this a valid test and omit the NOX emission measurements; 
however, we may require you to repeat the test if we determine that you 
inappropriately voided the test with respect to NOX emission 
measurement.
    (g) Measured vs. declared fuel consumption. Determine declared fuel 
consumption as follows:
    (1) Select fuel consumption rates in g/s to characterize the 
engine's fuel maps. You must select a declared value for each test 
point that is at or above the corresponding value determined in 
paragraphs (b) through (d) of this section, including those from 
redundant measurements.
    (2) Declared fuel consumption serves as emission standards under 
Sec.  1036.108. These are the values that vehicle manufacturers will 
use for certification under 40 CFR part 1037. Note that production 
engines are subject to GEM cycle-weighted limits as described in Sec.  
1036.301.
    (3) If you perform the carbon balance error verification, select 
declared values that are at or above the following emission 
measurements:
    (i) If you pass the [epsi]rC verification, you may use 
the average of the values from direct and indirect fuel measurements.
    (ii) If you fail [epsi]rC verification, but pass either 
the [epsi]aC or [epsi]aCrate verification, use 
the value from indirect fuel measurement.
    (iii) If you fail all three verifications, you must either void the 
test interval or use the highest value from direct and indirect fuel 
measurements. Note that we will consider our test results to be invalid 
if we fail all three verifications.

Sec.  1036.540  Determining cycle-average engine fuel maps.

    (a) Overview. This section describes how to determine an engine's 
cycle-average fuel maps for model year 2021 and later vehicles. Vehicle 
manufacturers may need cycle-average fuel maps for transient duty 
cycles, highway cruise cycles, or both to demonstrate compliance with 
emission standards under 40 CFR part 1037. Generate cycle-average 
engine fuel maps as follows:
    (1) Determine the engine's torque maps as described in Sec.  
1036.505(c).
    (2) Determine the engine's steady-state fuel map and fuel 
consumption at idle as described in Sec.  1036.535. If you are applying 
cycle-average fuel mapping for highway cruise cycles, you may instead 
use GEM's default fuel map instead of generating the steady-state fuel 
map in Sec.  1036.535(b).
    (3) Simulate several different vehicle configurations using GEM 
(see 40 CFR 1037.520) to create new engine duty cycles as described in 
paragraph (c) of this section. The transient vehicle duty cycles for 
this simulation are in 40 CFR part 1037, appendix A; the highway cruise 
cycles with grade are in 40 CFR part 1037, appendix D. Note that GEM 
simulation relies on vehicle service classes as described in 40 CFR 
1037.140.
    (4) Test the engines using the new duty cycles to determine fuel 
consumption, cycle work, and average vehicle speed as described in 
paragraph (d) of this section and establish GEM inputs for those 
parameters for further vehicle simulations as described in paragraph 
(e) of this section.
    (b) General test provisions. The following provisions apply for 
testing under this section:
    (1) To perform fuel mapping under this section for hybrid engines, 
make sure the engine and its hybrid features are appropriately 
configured to represent the hybrid features in your testing.
    (2) Measure NOX emissions for each specified sampling 
period in grams. You may perform these measurements using a 
NOX emission-measurement system that meets the requirements 
of 40 CFR part 1065, subpart J. Include these measured NOX 
values any time you report to us your fuel-consumption values from 
testing under this section. If a system malfunction prevents you from 
measuring NOX emissions during a test under this section but 
the test otherwise gives valid results, you may consider this a valid 
test and omit the NOX emission measurements; however, we may 
require you to repeat the test if we determine that you inappropriately 
voided the test with respect to NOX emission measurement.
    (3) The provisions related to carbon balance error verification in 
Sec.  1036.543 apply for all testing in this section. These procedures 
are optional, but we will perform carbon balance error verification for 
all testing under this section.
    (4) Correct fuel mass to a mass-specific net energy content of a 
reference fuel as described in paragraph (d)(13) of this section.
    (5) This section uses engine parameters and variables that are 
consistent with 40 CFR part 1065.
    (c) Create engine duty cycles. Use GEM to simulate your engine 
operation with several different vehicle configurations to create 
transient and highway cruise engine duty cycles corresponding to each 
vehicle configuration as follows:
    (1) Set up GEM to simulate your engine's operation based on your 
engine's torque maps, steady-state fuel maps, warm-idle speed as 
defined in 40 CFR 1037.520(h)(1), and fuel consumption at idle as 
described in paragraphs (a)(1) and (2) of this section.
    (2) Set up GEM with transmission parameters for different vehicle 
service classes and vehicle duty cycles. Specify the transmission's 
torque limit for each gear as the engine's maximum torque as determined 
in 40 CFR 1065.510. Specify the transmission type as Automatic 
Transmission for all engines and for all engine and vehicle duty 
cycles, except that the transmission type is Automated Manual 
Transmission for Heavy HDE operating over the highway cruise cycles or 
the SET duty cycle. For automatic transmissions set neutral idle to 
``Y'' in the vehicle file. Select gear ratios for each gear as shown in 
the following table:

                    Table 1 to Paragraph (c)(2) of Sec.   1036.540--GEM Input for Gear Ratio
----------------------------------------------------------------------------------------------------------------
                                                 Spark-ignition HDE,
                                                light HDE, and medium        Heavy HDE--      Heavy HDE-- cruise
                 Gear number                     HDE-- all engine and     transient and FTP      and SET duty
                                                 vehicle duty cycles         duty cycles            cycles
----------------------------------------------------------------------------------------------------------------
1............................................                     3.10                  3.51                12.8
2............................................                     1.81                  1.91                9.25

[[Page 4534]]

 
3............................................                     1.41                  1.43                6.76
4............................................                     1.00                  1.00                4.90
5............................................                     0.71                  0.74                3.58
6............................................                     0.61                  0.64                2.61
7............................................  .......................  ....................                1.89
8............................................  .......................  ....................                1.38
9............................................  .......................  ....................                1.00
10...........................................  .......................  ....................                0.73
Lockup Gear..................................                        3                     3  ..................
----------------------------------------------------------------------------------------------------------------

    (3) Run GEM for each simulated vehicle configuration and use the 
GEM outputs of instantaneous engine speed and engine flywheel torque 
for each vehicle configuration to generate a 10 Hz transient duty cycle 
corresponding to each vehicle configuration operating over each vehicle 
duty cycle. Run GEM for the specified number of vehicle configurations. 
You may run additional vehicle configurations to represent a wider 
range of in-use vehicles. Run GEM as follows:
    (i) Determining axle ratio and tire size. Set the axle ratio, 
ka, and tire size,
[GRAPHIC] [TIFF OMITTED] TR24JA23.060

    for each vehicle configuration based on the corresponding 
designated engine speed (fnrefA, fnrefB, 
fnrefC, fnrefD, or fntest as defined 
in 40 CFR 1065.610(c)(2)) at 65 mi/hr for the transient duty cycle and 
for the 65 mi/hr highway cruise cycle. Similarly, set these parameters 
based on the corresponding designated engine speed at 55 mi/hr for the 
55 mi/hr highway cruise cycle. Use one of the following equations to 
determine
[GRAPHIC] [TIFF OMITTED] TR24JA23.061

and ka at each of the defined engine speeds:
[GRAPHIC] [TIFF OMITTED] TR24JA23.062

Where:

fn[speed] = engine's angular speed as determined in 
paragraph (c)(3)(ii) or (iii) of this section.
ktopgear = transmission gear ratio in the highest 
available gear from Table 1 of this section.
vref = reference speed. Use 65 mi/hr for the transient 
cycle and the 65 mi/hr highway cruise cycle and use 55 mi/hr for the 
55 mi/hr highway cruise cycle.
[GRAPHIC] [TIFF OMITTED] TR24JA23.063

Example for a vocational Light HDV or vocational Medium HDV with a 6-
speed automatic transmission at B speed (Test 3 or 4 in Table 3 of this 
section):

fnrefB = 1870 r/min = 31.17 r/s
kaB = 4.0
ktopgear = 0.61
vref = 65 mi/hr = 29.06 m/s

[[Page 4535]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.064

    (ii) Vehicle configurations for Spark-ignition HDE, Light HDE, and 
Medium HDE. Test at least eight different vehicle configurations for 
engines that will be installed in vocational Light HDV or vocational 
Medium HDV using vehicles in the following table:
[GRAPHIC] [TIFF OMITTED] TR24JA23.065

    (iii) Vehicle configurations for Heavy HDE. Test at least nine 
different vehicle configurations for engines that will be installed in 
vocational Heavy HDV and for tractors that are not heavy-haul tractors. 
Test six different vehicle configurations for engines that will be 
installed in heavy-haul tractors. Use the settings specific to each 
vehicle configuration as shown in Table 3 or Table 4 in this section, 
as appropriate. Engines subject to testing under both Table 3 and Table 
4 in this section need not repeat overlapping vehicle configurations, 
so complete fuel mapping requires testing 12 (not 15) vehicle 
configurations for those engines. However, the preceding sentence does 
not apply if you choose to create two separate maps from the vehicle 
configurations defined in Table 3 and Table 4 in this section. Tables 3 
and 4 follow:

[[Page 4536]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.066

    (iv) Vehicle configurations for mixed-use engines. If the engine 
will be installed in a combination of vehicles defined in paragraphs 
(c)(3)(ii) and (iii) of this section, use good engineering judgment to 
select at least nine vehicle configurations from Table 2 and Table 3 in 
this section that best represent the range of vehicles your engine will 
be sold in. This may require you to define additional representative 
vehicle configurations. For example, if your engines will be installed 
in vocational Medium HDV and vocational Heavy HDV, you might select 
Tests 2, 4, 6 and 8 of Table 2 in this section to represent vocational 
Medium HDV and Tests 3, 6, and 9 of Table 3 in this section to 
represent vocational Heavy HDV and add two more vehicle configurations 
that you define.
    (v) Defining GEM inputs. Use the defined values in Tables 1 through 
4 in this section to set up GEM with the correct regulatory subcategory 
and vehicle weight reduction.
    (d) Test the engine with GEM cycles. Test the engine over each of 
the transient engine duty cycles generated in paragraph (c) of this 
section as follows:
    (1) Operate the engine over a sequence of required and optional 
engine duty cycles as follows:
    (i) Sort the list of engine duty cycles into three separate groups 
by vehicle duty cycle: transient vehicle cycle, 55 mi/hr highway cruise 
cycle, and 65 mi/hr highway cruise cycle.
    (ii) Within each group of engine duty cycles derived from the same 
vehicle duty cycle, first run the engine duty cycle with the highest 
reference cycle work, followed by the cycle with the lowest cycle work; 
followed by the cycle with second-highest cycle work, followed by the 
cycle with the second-lowest cycle work; continuing through all the 
cycles for that vehicle duty cycle. The series of engine duty cycles to 
represent a single vehicle duty cycle is a single fuel-mapping 
sequence. Each engine duty cycle represents a different interval. 
Repeat the fuel-mapping sequence for the engine duty cycles derived 
from the other vehicle duty cycles until testing is complete.
    (iii) Operate the engine over two full engine duty cycles to 
precondition before each interval in the fuel-mapping sequence. 
Precondition the engine before the first and second engine duty cycle 
in each fuel-mapping sequence by repeating operation with the engine 
duty cycle with the highest reference cycle work over the relevant 
vehicle duty cycle. The preconditioning for the remaining cycles in the 
fuel-mapping sequence consists of operation over the preceding two 
engine duty cycles in the fuel-mapping sequence (with or without 
measurement). For transient vehicle duty cycles, start each engine duty 
cycle within 10 seconds after finishing the preceding engine duty cycle 
(with or without measurement). For highway cruise cycles, start each 
engine duty cycle and interval after linearly ramping to the speed and 
torque setpoints over 5 seconds and stabilizing for 15 seconds.
    (2) If the engine has an adjustable warm idle speed setpoint, set 
it to the value defined in 40 CFR 1037.520(h)(1).
    (3) Control speed and torque to meet the cycle validation criteria 
in 40 CFR 1065.514 for each interval, except that the standard error of 
the estimate in Table 2 of 40 CFR 1065.514 is the only speed criterion 
that applies if the range of reference speeds is less than 10 percent 
of the mean reference speed. For spark-ignition gaseous-fueled engines 
with fuel delivery at a single point in the intake manifold, you may 
apply the statistical criteria in Table 5 in this section for transient 
testing. Note that 40

[[Page 4537]]

CFR part 1065 does not allow reducing cycle precision to a lower 
frequency than the 10 Hz reference cycle generated by GEM.

  Table 5 to Paragraph (c)(3) of Sec.   1036.540--Statistical Criteria for Validating Duty Cycles for Gaseous-
                                        Fueled Spark-Ignition Engines \a\
----------------------------------------------------------------------------------------------------------------
                Parameter                      Speed                Torque                       Power
----------------------------------------------------------------------------------------------------------------
Slope, a1...............................
Absolute value of intercept,              ..............  <=3% of maximum mapped      ..........................
 [verbar]a0[verbar].                                       torque.
Standard error of the estimate, SEE.....  ..............  <=15% of maximum mapped     <=15% of maximum mapped
                                                           torque.                     power
Coefficient of determination, r \2\.....  ..............  >=0.700...................  >=0.750
----------------------------------------------------------------------------------------------------------------
\a\ Statistical criteria apply as specified in 40 CFR 1065.514 unless otherwise specified.

    (4) Record measurements using direct and/or indirect measurement of 
fuel flow as follows:
    (i) Direct fuel-flow measurement. Record speed and torque and 
measure fuel consumption with a fuel flow meter for the interval 
defined by the engine duty cycle. Determine the corresponding mean 
values for the interval. Use of redundant direct fuel-flow measurements 
requires our advance approval.
    (ii) Indirect fuel-flow measurement. Record speed and torque and 
measure emissions and other inputs needed to run the chemical balance 
in 40 CFR 1065.655(c) for the interval defined by the engine duty 
cycle. Determine the corresponding mean values for the interval. Use of 
redundant indirect fuel-flow measurements requires our advance 
approval. Measure background concentration as described in 40 CFR 
1065.140, except that you may use one of the following methods to apply 
a single background reading to multiple intervals:
    (A) If you use batch sampling to measure background emissions, you 
may sample periodically into the bag over the course of multiple 
intervals. If you use this provision, you must apply the same 
background readings to correct emissions from each of the applicable 
intervals.
    (B) You may determine background emissions by sampling from the 
dilution air over multiple engine duty cycles. If you use this 
provision, you must allow sufficient time for stabilization of the 
background measurement; followed by an averaging period of at least 30 
seconds. Use the average of the two background readings to correct the 
measurement from each engine duty cycle. The first background reading 
must be taken no greater than 30 minutes before the start of the first 
applicable engine duty cycle and the second background reading must be 
taken no later than 30 minutes after the end of the last applicable 
engine duty cycle. Background readings may not span more than a full 
fuel-mapping sequence for a vehicle duty cycle.
    (5) Warm up the engine as described in 40 CFR 1065.510(b)(2). 
Within 60 seconds after concluding the warm-up, start the linear ramp 
of speed and torque over 20 seconds to the first speed and torque 
setpoint of the preconditioning cycle.
    (6) Precondition the engine before the start of testing as 
described in paragraph (d)(1)(iii) of this section.
    (7) Operate the engine over the first engine duty cycle. Record 
measurements during the interval. Measure and report NOX 
emissions over each interval as described in paragraph (b)(2) of this 
section.
    (8) Continue testing engine duty cycles that are derived from the 
other vehicle duty cycles until testing is complete.
    (9) You may interrupt the fuel-mapping sequence after completing 
any interval. You may calibrate analyzers, read and evacuate background 
bag samples, or sample dilution air for measuring background 
concentration before restarting. Shut down the engine during any 
interruption. If you restart the sequence within 30 minutes or less, 
restart the sequence at paragraph (d)(6) of this section and then 
restart testing at the next interval in the fuel-mapping sequence. If 
you restart the sequence after more than 30 minutes, restart the 
sequence at paragraph (d)(5) of this section and then restart testing 
at the next interval in the fuel-mapping sequence.
    (10) The following provisions apply for infrequent regeneration 
events, other interruptions during intervals, and otherwise voided 
intervals:
    (i) Stop testing if an infrequent regeneration event occurs during 
an interval or an interval is interrupted for any other reason. Void 
the interrupted interval and any additional intervals for which you are 
not able to meet requirements for measuring background concentration. 
If the infrequent regeneration event occurs between intervals, void 
completed intervals only if you are not able to meet requirements for 
measuring background concentration for those intervals.
    (ii) If an infrequent regeneration event occurs, allow the 
regeneration event to finish with the engine operating at a speed and 
load that allows effective regeneration.
    (iii) If you interrupt testing during an interval, if you restart 
the sequence within 30 minutes or less, restart the sequence at 
paragraph (d)(6) of this section and then restart testing at the next 
interval in the fuel-mapping sequence. If you restart the sequence 
after more than 30 minutes, restart the sequence at paragraph (d)(5) of 
this section and then restart testing at the next interval in the fuel-
mapping sequence.
    (iv) If you void one or more intervals, you must perform additional 
testing to get results for all intervals. You may rerun a complete 
fuel-mapping sequence or any contiguous part of the fuel-mapping 
sequence. If you get a second valid measurement for any interval, use 
only the result from the last valid interval. If you restart the 
sequence within 30 minutes or less, restart the sequence at paragraph 
(d)(6) of this section and then restart testing at the first selected 
interval in the fuel-mapping sequence. If you restart the sequence 
after more than 30 minutes, restart the sequence at paragraph (d)(5) of 
this section and then restart testing at the first selected interval in 
the fuel-mapping sequence. Continue testing until you have valid 
results for all intervals. The following examples illustrate possible 
scenarios for a partial run through a fuel-mapping sequence:
    (A) If you voided only the interval associated with the fourth 
engine duty cycle in the sequence, you may restart the sequence using 
the second and third engine duty cycles as the preconditioning cycles 
and stop after completing the interval associated with the fourth 
engine duty cycle.
    (B) If you voided the intervals associated with the fourth and 
sixth engine duty cycles, you may restart the

[[Page 4538]]

sequence using the second and third engine duty cycles for 
preconditioning and stop after completing the interval associated with 
the sixth engine duty cycle.
    (11) You may send signals to the engine controller during the test, 
such as current transmission gear and vehicle speed, if that allows 
engine operation to better represent in-use operation.
    (12) Calculate the fuel mass, mfuel, for each duty cycle 
using one of the following equations:
    (i) Determine fuel-consumption using emission measurements from the 
raw or diluted exhaust. Calculate the mass of fuel for each duty cycle, 
mfuel[cycle], as follows:
    (A) For calculations that use continuous measurement of emissions 
and continuous CO2 from urea, calculate 
mfuel[cycle] using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.067

Where:

MC = molar mass of carbon.
wCmeas = carbon mass fraction of fuel (or mixture of 
fuels) as determined in 40 CFR 1065.655(d), except that you may not 
use the default properties in Table 2 of 40 CFR 1065.655 to 
determine [alpha], [beta], and wC. You may not account 
for the contribution to [alpha], [beta], [gamma], and [delta] of 
diesel exhaust fluid or other non-fuel fluids injected into the 
exhaust.
i = an indexing variable that represents one recorded emission 
value.
N = total number of measurements over the duty cycle.
nexh = exhaust molar flow rate from which you measured 
emissions.
xCcombdry = amount of carbon from fuel and any injected 
fluids in the exhaust per mole of dry exhaust as determined in 40 
CFR 1065.655(c).
xH2Oexhdry = amount of H2O in exhaust per mole 
of exhaust as determined in 40 CFR 1065.655(c).
[Delta]t = 1/frecord
MCO2 = molar mass of carbon dioxide.
mCO2DEFi = mass emission rate of CO2 resulting 
from diesel exhaust fluid decomposition over the duty cycle as 
determined from Sec.  1036.535(b)(9). If your engine does not 
utilize diesel exhaust fluid for emission control, or if you choose 
not to perform this correction, set mCO2DEFi equal to 0.

Example:

MC = 12.0107 g/mol
wCmeas = 0.867
N = 6680
nexh1= 2.876 mol/s
nexh1 = 2.224 mol/s
xCcombdry1 = 2.61[middot]10-\3\ mol/mol
xCcombdry2 = 1.91[middot]10-\3\ mol/mol
xH2Oexh1 = 3.53[middot]10-\2\ mol/mol
xH2Oexh2 = 3.13[middot]10-\2\ mol/mol
frecord = 10 Hz
[Delta]t = 1/10 = 0.1 s
MCO2 = 44.0095 g/mol
mCO2DEF1 = 0.0726 g/s
mCO2DEF2 = 0.0751 g/s
[GRAPHIC] [TIFF OMITTED] TR24JA23.068

mfueltransientTest1 = 1619.6 g

    (B) If you measure batch emissions and continuous CO2 
from urea, calculate mfuel[cycle] using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.069

    (C) If you measure continuous emissions and batch CO2 
from urea, calculate mfuel[cycle] using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.070

[[Page 4539]]

    (D) If you measure batch emissions and batch CO2 from 
urea, calculate mfuel[cycle] using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.071

    (ii) Manufacturers may choose to measure fuel mass flow rate. 
Calculate the mass of fuel for each duty cycle, 
mfuel[cycle], as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.072

Where:

i = an indexing variable that represents one recorded value.
N = total number of measurements over the duty cycle. For batch fuel 
mass measurements, set N = 1.
mfueli = the fuel mass flow rate, for each point, i, 
starting from i = 1.
[Delta]t = 1/[fnof]record
[fnof]record = the data recording frequency.

Example:

N = 6680
mfuel1 = 1.856 g/s
mfuel2 = 1.962 g/s
[fnof]record = 10 Hz
[Delta]t = 1/10 = 0.1 s
mfueltransient = (1.856 + 1.962+ . . . 
+mfuel6680) [middot] 0.1
mfueltransient = 111.95 g

    (13) Correct the measured or calculated fuel mass, 
mfuel, for each result to a mass-specific net energy content 
of a reference fuel as described in Sec.  1036.535(e), replacing 
mifuel with mfuel in Eq. 1036.535-4.
    (e) Determine GEM inputs. Use the results of engine testing in 
paragraph (d) of this section to determine the GEM inputs for the 
transient duty cycle and optionally for each of the highway cruise 
cycles corresponding to each simulated vehicle configuration as 
follows:
    (1) Using the calculated fuel mass consumption values, 
mfuel[cycle], described in paragraph (d) of this section, 
declare values using the methods described in Sec.  1036.535(g)(2) and 
(3).
    (2) We will determine mfuel[cycle] values using the 
method described in Sec.  1036.535(g)(3).
    (3) For the transient cycle, calculate engine output speed per unit 
vehicle speed,
[GRAPHIC] [TIFF OMITTED] TR24JA23.073

    by taking the average engine speed measured during the engine test 
while the vehicle is moving and dividing it by the average vehicle 
speed provided by GEM. Note that the engine cycle created by GEM has a 
flag to indicate when the vehicle is moving.
    (4) Determine engine idle speed and torque, by taking the average 
engine speed and torque measured during the engine test while the 
vehicle is not moving. Note that the engine cycle created by GEM has a 
flag to indicate when the vehicle is moving.
    (5) For the cruise cycles, calculate the average engine output 
speed, fnengine, and the average engine output torque 
(positive torque only), Tengine, while the vehicle is 
moving. Note that the engine cycle created by GEM has a flag to 
indicate when the vehicle is moving.
    (6) Determine positive work according to 40 CFR part 1065, 
W[cycle], by using the engine speed and engine torque 
measured during the engine test while the vehicle is moving. Note that 
the engine cycle created by GEM has a flag to indicate when the vehicle 
is moving.
    (7) The following tables illustrate the GEM data inputs 
corresponding to the different vehicle configurations for a given duty 
cycle:
    (i) For the transient cycle:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.074
    

[[Page 4540]]

    (ii) For the cruise cycles:

             Table 7 to Paragraph (e)(7)(ii) of Sec.   1036.540--Generic Example of an Output Matrix for Cruise Cycle Vehicle Configurations
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                   Configuration
                        Parameter                        -----------------------------------------------------------------------------------------------
                                                                 1               2               3               4             . . .             n
--------------------------------------------------------------------------------------------------------------------------------------------------------
mfuel[cycle]............................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
fnengine[cycle].........................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
Tengine[cycle]..........................................
--------------------------------------------------------------------------------------------------------------------------------------------------------
W [cycle]...............................................
--------------------------------------------------------------------------------------------------------------------------------------------------------

Sec.  1036.543  Carbon balance error verification.

    The optional carbon balance error verification in 40 CFR 1065.543 
compares independent assessments of the flow of carbon through the 
system (engine plus aftertreatment). This procedure applies for each 
individual interval in Sec. Sec.  1036.535(b), (c), and (d) and 
1036.540 and 40 CFR 1037.550.

Sec.  1036.550  Calculating greenhouse gas emission rates.

    This section describes how to calculate official emission results 
for CO2, CH4, and N2O.
    (a) Calculate brake-specific emission rates for each applicable 
duty cycle as specified in 40 CFR 1065.650. Apply infrequent 
regeneration adjustment factors as described in Sec.  1036.580.
    (b) Adjust CO2 emission rates calculated under paragraph 
(a) of this section for measured test fuel properties as specified in 
this paragraph (b). This adjustment is intended to make official 
emission results independent of differences in test fuels within a fuel 
type. Use good engineering judgment to develop and apply testing 
protocols to minimize the impact of variations in test fuels.
    (1) Determine your test fuel's mass-specific net energy content, 
Emfuelmeas, also known as lower heating value, in MJ/kg, 
expressed to at least three decimal places. Determine 
Emfuelmeas as follows:
    (i) For liquid fuels, determine Emfuelmeas according to 
ASTM D4809 (incorporated by reference in Sec.  1036.810). Have the 
sample analyzed by at least three different labs and determine the 
final value of your test fuel's Emfuelmeas as the median all 
the lab test results you obtained. If you have results from three 
different labs, we recommend you screen them to determine if additional 
observations are needed. To perform this screening, determine the 
absolute value of the difference between each lab result and the 
average of the other two lab results. If the largest of these three 
resulting absolute value differences is greater than 0.297 MJ/kg, we 
recommend you obtain additional results prior to determining the final 
value of Emfuelmeas.
    (ii) For gaseous fuels, determine Emfuelmeas according 
to ASTM D3588 (incorporated by reference in Sec.  1036.810).
    (2) Determine your test fuel's carbon mass fraction, wC, 
as described in 40 CFR 1065.655(d), expressed to at least three decimal 
places; however, you must measure fuel properties rather than using the 
default values specified in Table 1 of 40 CFR 1065.655.
    (i) For liquid fuels, have the sample analyzed by at least three 
different labs and determine the final value of your test fuel's 
wC as the median of all of the lab results you obtained. If 
you have results from three different labs, we recommend you screen 
them to determine if additional observations are needed. To perform 
this screening, determine the absolute value of the difference between 
each lab result and the average of the other two lab results. If the 
largest of these three resulting absolute value differences is greater 
than 1.56 percent carbon, we recommend you obtain additional results 
prior to determining the final value of wC.
    (ii) For gaseous fuels, have the sample analyzed by a single lab 
and use that result as your test fuel's wC.
    (3) If, over a period of time, you receive multiple fuel deliveries 
from a single stock batch of test fuel, you may use constant values for 
mass-specific energy content and carbon mass fraction, consistent with 
good engineering judgment. To use these constant values, you must 
demonstrate that every subsequent delivery comes from the same stock 
batch and that the fuel has not been contaminated.
    (4) Correct measured CO2 emission rates as follows:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.075
    
Where:

eCO2 = the calculated CO2 emission result.
Emfuelmeas = the mass-specific net energy content of the 
test fuel as determined in paragraph (b)(1) of this section. Note 
that dividing this value by wCmeas (as is done in this 
equation) equates to a carbon-specific net energy content having the 
same units as EmfuelCref.
EmfuelCref = the reference value of carbon-mass-specific 
net energy content for the appropriate fuel type, as determined in 
Table 1 in this section.
wCmeas = carbon mass fraction of the test fuel (or 
mixture of test fuels) as determined in paragraph (b)(2) of this 
section.

Example:

eCO2 = 630.0 g/hp[middot]hr
Emfuelmeas = 42.528 MJ/kg
EmfuelCref = 49.3112 MJ/kgC
wCmeas = 0.870
[GRAPHIC] [TIFF OMITTED] TR24JA23.076

eCO2cor = 624.5 g/hp[middot]hr

[[Page 4541]]

                    Table 1 to Paragraph (b)(4) of Sec.   1036.550--Reference Fuel Properties
----------------------------------------------------------------------------------------------------------------
                                                                     Reference fuel carbon-
                                                                       mass-specific net        Reference fuel
                           Fuel type \a\                                energy content,          carbon mass
                                                                    EmfuelCref (MJ/kgC) \b\  fraction, wCref \b\
 
----------------------------------------------------------------------------------------------------------------
Diesel fuel.......................................................                  49.3112                0.874
Gasoline..........................................................                  50.4742                0.846
Natural gas.......................................................                  66.2910                0.750
LPG...............................................................                  56.5218                0.820
Dimethyl ether....................................................                  55.3886                0.521
High-level ethanol-gasoline blends................................                  50.3211                0.576
----------------------------------------------------------------------------------------------------------------
\a\ For fuels that are not listed, you must ask us to approve reference fuel properties.
\b\ For multi-fuel streams, such as natural gas with diesel fuel pilot injection, use good engineering judgment
  to determine blended values for EmfuelCref and wCref using the values in this table.

    (c) Your official emission result for each pollutant equals your 
calculated brake-specific emission rate multiplied by all applicable 
adjustment factors, other than the deterioration factor.

Sec.  1036.555  Test procedures to verify deterioration factors.

    Sections 1036.240 through 1036.246 describe certification 
procedures to determine, verify, and apply deterioration factors. This 
section describes the measurement procedures for verifying 
deterioration factors using PEMS with in-use vehicles.
    (a) Use PEMS to collect 1 Hz data throughout a shift-day of 
driving. Collect all the data elements needed to determine brake-
specific emissions. Calculate emission results using moving average 
windows as described in Sec.  1036.530.
    (b) Collect data as needed to perform the calculations specified in 
paragraph (a) of this section and to submit the test report specified 
in Sec.  1036.246(d).

Sec.  1036.580  Infrequently regenerating aftertreatment devices.

    For engines using aftertreatment technology with infrequent 
regeneration events that may occur during testing, take one of the 
following approaches to account for the emission impact of regeneration 
on criteria pollutant and greenhouse gas emissions:
    (a) You may use the calculation methodology described in 40 CFR 
1065.680 to adjust measured emission results. Do this by developing an 
upward adjustment factor and a downward adjustment factor for each 
pollutant based on measured emission data and observed regeneration 
frequency as follows:
    (1) Adjustment factors should generally apply to an entire engine 
family, but you may develop separate adjustment factors for different 
configurations within an engine family. Use the adjustment factors from 
this section for all testing for the engine family.
    (2) You may use carryover data to establish adjustment factors for 
an engine family as described in Sec.  1036.235(d), consistent with 
good engineering judgment.
    (3) Identify the value of F[cycle] in each application 
for the certification for which it applies.
    (4) Calculate separate adjustment factors for each required duty 
cycle.
    (b) You may ask us to approve an alternate methodology to account 
for regeneration events. We will generally limit approval to cases 
where your engines use aftertreatment technology with extremely 
infrequent regeneration and you are unable to apply the provisions of 
this section.
    (c) You may choose to make no adjustments to measured emission 
results if you determine that regeneration does not significantly 
affect emission levels for an engine family (or configuration) or if it 
is not practical to identify when regeneration occurs. You may omit 
adjustment factors under this paragraph (c) for N2O, 
CH4, or other individual pollutants under this paragraph (c) 
as appropriate. If you choose not to make adjustments under paragraph 
(a) or (b) of this section, your engines must meet emission standards 
for all testing, without regard to regeneration.

Subpart G--Special Compliance Provisions

Sec.  1036.601  Overview of compliance provisions.

    (a) Engine and vehicle manufacturers, as well as owners, operators, 
and rebuilders of engines subject to the requirements of this part, and 
all other persons, must observe the provisions of this part, the 
provisions of 40 CFR part 1068, and the provisions of the Clean Air 
Act. The provisions of 40 CFR part 1068 apply for heavy-duty highway 
engines as specified in that part, subject to the following provisions:
    (1) The exemption provisions of 40 CFR 1068.201 through 1068.230, 
1068.240, and 1068.260 through 265 apply for heavy-duty motor vehicle 
engines. The other exemption provisions, which are specific to nonroad 
engines, do not apply for heavy-duty vehicles or heavy-duty engines.
    (2) Engine signals to indicate a need for maintenance under Sec.  
1036.125(a)(1)(ii) are considered an element of design of the emission 
control system. Disabling, resetting, or otherwise rendering such 
signals inoperative without also performing the indicated maintenance 
procedure is therefore prohibited under 40 CFR 1068.101(b)(1).
    (3) The warranty-related prohibitions in section 203(a)(4) of the 
Act (42 U.S.C. 7522(a)(4)) apply to manufacturers of new heavy-duty 
highway engines in addition to the prohibitions described in 40 CFR 
1068.101(b)(6). We may assess a civil penalty up to $44,539 for each 
engine or vehicle in violation.
    (b) The following provisions from 40 CFR parts 85 and 86 continue 
to apply after December 20, 2026 for engines subject to the 
requirements of this part:
    (1) The tampering prohibition in 40 CFR 1068.101(b)(1) applies for 
alternative fuel conversions as specified in 40 CFR part 85, subpart F.
    (2) Engine manufacturers must meet service information requirements 
as specified in 40 CFR 86.010-38(j).
    (3) Provisions related to nonconformance penalties apply as 
described in 40 CFR part 86, subpart L. Note that nonconformance 
penalty provisions are not available for current or future emission 
standards unless we revise the regulation to specify how to apply those 
provisions.
    (4) The manufacturer-run in-use testing program described in 40 CFR 
part 86, subpart T, continues to apply

[[Page 4542]]

for engines subject to exhaust emission standards under 40 CFR part 86.
    (c) The emergency vehicle field modification provisions of 40 CFR 
85.1716 apply with respect to the standards of this part.
    (d) Subpart C of this part describes how to test and certify dual-
fuel and flexible-fuel engines. Some multi-fuel engines may not fit 
either of those defined terms. For such engines, we will determine 
whether it is most appropriate to treat them as single-fuel engines, 
dual-fuel engines, or flexible-fuel engines based on the range of 
possible and expected fuel mixtures. For example, an engine might burn 
natural gas but initiate combustion with a pilot injection of diesel 
fuel. If the engine is designed to operate with a single fueling 
algorithm (i.e., fueling rates are fixed at a given engine speed and 
load condition), we would generally treat it as a single-fuel engine. 
In this context, the combination of diesel fuel and natural gas would 
be its own fuel type. If the engine is designed to also operate on 
diesel fuel alone, we would generally treat it as a dual-fuel engine. 
If the engine is designed to operate on varying mixtures of the two 
fuels, we would generally treat it as a flexible-fuel engine. To the 
extent that requirements vary for the different fuels or fuel mixtures, 
we may apply the more stringent requirements.

Sec.  1036.605  Alternate emission standards for engines used in 
specialty vehicles.

    Starting in model year 2027, compression-ignition engines at or 
above 56 kW and spark-ignition engines of any size that will be 
installed in specialty vehicles as allowed by 40 CFR 1037.605 are 
exempt from the standards of subpart B of this part if they are 
certified under this part to alternate emission standards as follows:
    (a) Spark-ignition engines must be of a configuration that is 
identical to one that is certified under 40 CFR part 1048 to Blue Sky 
standards under 40 CFR 1048.140.
    (b) Compression-ignition engines must be of a configuration that is 
identical to one that is certified under 40 CFR part 1039, and meet the 
following additional standards using the same duty cycles that apply 
under 40 CFR part 1039:
    (1) The engines must be certified with a family emission limit for 
PM of 0.020 g/kW-hr.
    (2) Diesel-fueled engines using selective catalytic reduction must 
meet an emission standard of 0.1 g/kW-hr for N2O.
    (c) Except as specified in this section, engines certified under 
this section must meet all the requirements that apply under 40 CFR 
part 1039 or 1048 instead of the comparable provisions in this part. 
Before shipping engines under this section, you must have written 
assurance from vehicle manufacturers that they need a certain number of 
exempted engines under this section. In your annual production report 
under 40 CFR 1039.250 or 1048.250, count these engines separately and 
identify the vehicle manufacturers that will be installing them. Treat 
these engines as part of the corresponding engine family under 40 CFR 
part 1039 or part 1048 for compliance purposes such as testing 
production engines, in-use testing, defect reporting, and recall.
    (d) The engines must be labeled as described in Sec.  1036.135, 
with the following statement instead of the one specified in Sec.  
1036.135(c)(8): ``This engine conforms to alternate standards for 
specialty vehicles under 40 CFR 1036.605.'' Engines certified under 
this section may not have the label specified for nonroad engines in 40 
CFR part 1039 or 1048 or any other label identifying them as nonroad 
engines.
    (e) In a separate application for a certificate of conformity, 
identify the corresponding nonroad engine family, describe the label 
required under section, state that you meet applicable diagnostic 
requirements under 40 CFR part 1039 or part 1048, and identify your 
projected nationwide production volume.
    (f) No additional certification fee applies for engines certified 
under this section.
    (g) Engines certified under this section may not generate or use 
emission credits under this part or under 40 CFR part 1039. The 
vehicles in which these engines are installed may generate or use 
emission credits as described in 40 CFR part 1037.

Sec.  1036.610  Off-cycle technology credits and adjustments for 
reducing greenhouse gas emissions.

    (a) You may ask us to apply the provisions of this section for 
CO2 emission reductions resulting from powertrain 
technologies that were not in common use with heavy-duty vehicles 
before model year 2010 that are not reflected in the specified 
procedure. While you are not required to prove that such technologies 
were not in common use with heavy-duty vehicles before model year 2010, 
we will not approve your request if we determine that they do not 
qualify. We will apply these provisions only for technologies that will 
result in a measurable, demonstrable, and verifiable real-world 
CO2 reduction. Note that prior to model year 2016, these 
technologies were referred to as ``innovative technologies''.
    (b) The provisions of this section may be applied as either an 
improvement factor (used to adjust emission results) or as a separate 
credit, consistent with good engineering judgment. Note that the term 
``credit'' in this section describes an additive adjustment to emission 
rates and is not equivalent to an emission credit in the ABT program of 
subpart H of this part. We recommend that you base your credit/
adjustment on A to B testing of pairs of engines/vehicles differing 
only with respect to the technology in question.
    (1) Calculate improvement factors as the ratio of in-use emissions 
with the technology divided by the in-use emissions without the 
technology. Adjust the emission results by multiplying by the 
improvement factor. Use the improvement-factor approach where good 
engineering judgment indicates that the actual benefit will be 
proportional to emissions measured over the procedures specified in 
this part. For example, the benefits from technologies that reduce 
engine operation would generally be proportional to the engine's 
emission rate.
    (2) Calculate separate credits based on the difference between the 
in-use emission rate (g/ton-mile) with the technology and the in-use 
emission rate without the technology. Subtract this value from your 
measured emission result and use this adjusted value to determine your 
FEL. We may also allow you to calculate the credits based on g/
hp[middot]hr emission rates. Use the separate-credit approach where 
good engineering judgment indicates that the actual benefit will not be 
proportional to emissions measured over the procedures specified in 
this part.
    (3) We may require you to discount or otherwise adjust your 
improvement factor or credit to account for uncertainty or other 
relevant factors.
    (c) Send your request to the Designated Compliance Officer. We 
recommend that you do not begin collecting data (for submission to EPA) 
before contacting us. For technologies for which the vehicle 
manufacturer could also claim credits (such as transmissions in certain 
circumstances), we may require you to include a letter from the vehicle 
manufacturer stating that it will not seek credits for the same 
technology. Your request must contain the following items:
    (1) A detailed description of the off-cycle technology and how it 
functions to reduce CO2 emissions under conditions not 
represented on the duty cycles required for certification.

[[Page 4543]]

    (2) A list of the engine configurations that will be equipped with 
the technology.
    (3) A detailed description and justification of the selected 
engines.
    (4) All testing and simulation data required under this section, 
plus any other data you have considered in your analysis. You may ask 
for our preliminary approval of your plan under Sec.  1036.210.
    (5) A complete description of the methodology used to estimate the 
off-cycle benefit of the technology and all supporting data, including 
engine testing and in-use activity data. Also include a statement 
regarding your recommendation for applying the provisions of this 
section for the given technology as an improvement factor or a credit.
    (6) An estimate of the off-cycle benefit by engine model, and the 
fleetwide benefit based on projected sales of engine models equipped 
with the technology.
    (7) A demonstration of the in-use durability of the off-cycle 
technology, based on any available engineering analysis or durability 
testing data (either by testing components or whole engines).
    (d) We may seek public comment on your request, consistent with the 
provisions of 40 CFR 86.1869-12(d). However, we will generally not seek 
public comment on credits/adjustments based on A to B engine 
dynamometer testing, chassis testing, or in-use testing.
    (e) We may approve an improvement factor or credit for any 
configuration that is properly represented by your testing.
    (1) For model years before 2021, you may continue to use an 
approved improvement factor or credit for any appropriate engine 
families in future model years through 2020.
    (2) For model years 2021 and later, you may not rely on an approval 
for model years before 2021. You must separately request our approval 
before applying an improvement factor or credit under this section for 
2021 and later engines, even if we approved an improvement factor or 
credit for similar engine models before model year 2021. Note that 
approvals for model year 2021 and later may carry over for multiple 
years.

Sec.  1036.615  Engines with Rankine cycle waste heat recovery and 
hybrid powertrains.

    This section specifies how to generate advanced-technology emission 
credits for hybrid powertrains that include energy storage systems and 
regenerative braking (including regenerative engine braking) and for 
engines that include Rankine-cycle (or other bottoming cycle) exhaust 
energy recovery systems. This section applies only for model year 2020 
and earlier engines.
    (a) Pre-transmission hybrid powertrains. Test pre-transmission 
hybrid powertrains with the hybrid engine procedures of 40 CFR part 
1065 or with the post-transmission procedures in 40 CFR 1037.550. Pre-
transmission hybrid powertrains are those engine systems that include 
features to recover and store energy during engine motoring operation 
but not from the vehicle's wheels. Engines certified with pre-
transmission hybrid powertrains must be certified to meet the 
diagnostic requirements as specified in Sec.  1036.110 with respect to 
powertrain components and systems; if different manufacturers produce 
the engine and the hybrid powertrain, the hybrid powertrain 
manufacturer may separately certify its powertrain relative to 
diagnostic requirements.
    (b) Rankine engines. Test engines that include Rankine-cycle 
exhaust energy recovery systems according to the procedures specified 
in subpart F of this part unless we approve alternate procedures.
    (c) Calculating credits. Calculate credits as specified in subpart 
H of this part. Credits generated from engines and powertrains 
certified under this section may be used in other averaging sets as 
described in Sec.  1036.740(c).
    (d) Off-cycle technologies. You may certify using both the 
provisions of this section and the off-cycle technology provisions of 
Sec.  1036.610, provided you do not double-count emission benefits.

Sec.  1036.620  Alternate CO2 standards based on model year 2011 
compression-ignition engines.

    For model years 2014 through 2016, you may certify your 
compression-ignition engines to the CO2 standards of this 
section instead of the CO2 standards in Sec.  1036.108. 
However, you may not certify engines to these alternate standards if 
they are part of an averaging set in which you carry a balance of 
banked credits. You may submit applications for certifications before 
using up banked credits in the averaging set, but such certificates 
will not become effective until you have used up (or retired) your 
banked credits in the averaging set. For purposes of this section, you 
are deemed to carry credits in an averaging set if you carry credits 
from advanced technology that are allowed to be used in that averaging 
set.
    (a) The standards of this section are determined from the measured 
emission rate of the engine of the applicable baseline 2011 engine 
family or families as described in paragraphs (b) and (c) of this 
section. Calculate the CO2 emission rate of the baseline 
engine using the same equations used for showing compliance with the 
otherwise applicable standard. The alternate CO2 standard 
for light and medium heavy-duty vocational-certified engines (certified 
for CO2 using the transient cycle) is equal to the baseline 
emission rate multiplied by 0.975. The alternate CO2 
standard for tractor-certified engines (certified for CO2 
using the SET duty cycle) and all other Heavy HDE is equal to the 
baseline emission rate multiplied by 0.970. The in-use FEL for these 
engines is equal to the alternate standard multiplied by 1.03.
    (b) This paragraph (b) applies if you do not certify all your 
engine families in the averaging set to the alternate standards of this 
section. Identify separate baseline engine families for each engine 
family that you are certifying to the alternate standards of this 
section. For an engine family to be considered the baseline engine 
family, it must meet the following criteria:
    (1) It must have been certified to all applicable emission 
standards in model year 2011. If the baseline engine was certified to a 
NOX FEL above the standard and incorporated the same 
emission control technologies as the new engine family, you may adjust 
the baseline CO2 emission rate to be equivalent to an engine 
meeting the 0.20 g/hp[middot]hr NOX standard (or your higher 
FEL as specified in this paragraph (b)(1)), using certification results 
from model years 2009 through 2011, consistent with good engineering 
judgment.
    (i) Use the following equation to relate model year 2009-2011 
NOX and CO2 emission rates (g/hp[middot]hr): 
CO2 = a x log(NOX)+b.
    (ii) For model year 2014-2016 engines certified to NOX 
FELs above 0.20 g/hp[middot]hr, correct the baseline CO2 
emissions to the actual NOX FELs of the 2014-2016 engines.
    (iii) Calculate separate adjustments for emissions over the SET 
duty cycle and the transient cycle.
    (2) The baseline configuration tested for certification must have 
the same engine displacement as the engines in the engine family being 
certified to the alternate standards, and its rated power must be 
within five percent of the highest rated power in the engine family 
being certified to the alternate standards.
    (3) The model year 2011 U.S.-directed production volume of the 
configuration tested must be at least one percent of the

[[Page 4544]]

total 2011 U.S.-directed production volume for the engine family.
    (4) The tested configuration must have cycle-weighted BSFC 
equivalent to or better than all other configurations in the engine 
family.
    (c) This paragraph (c) applies if you certify all your engine 
families in the primary intended service class to the alternate 
standards of this section. For purposes of this section, you may 
combine Light HDE and Medium HDE into a single averaging set. Determine 
your baseline CO2 emission rate as the production-weighted 
emission rate of the certified engine families you produced in the 2011 
model year. If you produce engines for both tractors and vocational 
vehicles, treat them as separate averaging sets. Adjust the 
CO2 emission rates to be equivalent to an engine meeting the 
average NOX FEL of new engines (assuming engines certified 
to the 0.20 g/hp[middot]hr NOX standard have a 
NOX FEL equal to 0.20 g/hp[middot]hr), as described in 
paragraph (b)(1) of this section.
    (d) Include the following statement on the emission control 
information label: ``THIS ENGINE WAS CERTIFIED TO AN ALTERNATE 
CO2 STANDARD UNDER 40 CFR 1036.620.''
    (e) You may not bank CO2 emission credits for any engine 
family in the same averaging set and model year in which you certify 
engines to the standards of this section. You may not bank any 
advanced-technology credits in any averaging set for the model year you 
certify under this section (since such credits would be available for 
use in this averaging set). Note that the provisions of Sec.  1036.745 
apply for deficits generated with respect to the standards of this 
section.
    (f) You need our approval before you may certify engines under this 
section, especially with respect to the numerical value of the 
alternate standards. We will not approve your request if we determine 
that you manipulated your engine families or engine configurations to 
certify to less stringent standards, or that you otherwise have not 
acted in good faith. You must keep and provide to us any information we 
need to determine that your engine families meet the requirements of 
this section. Keep these records for at least five years after you stop 
producing engines certified under this section.

Sec.  1036.625  In-use compliance with CO2 family emission 
limits (FELs).

    Section 1036.225 describes how to change the FEL for an engine 
family during the model year. This section, which describes how you may 
ask us to increase an engine family's CO2 FEL after the end 
of the model year, is intended to address circumstances in which it is 
in the public interest to apply a higher in-use CO2 FEL 
based on forfeiting an appropriate number of emission credits. For 
example, this may be appropriate where we determine that recalling 
vehicles would not significantly reduce in-use emissions. We will 
generally not allow this option where we determine the credits being 
forfeited would likely have expired.
    (a) You may ask us to increase an engine family's FEL after the end 
of the model year if you believe some of your in-use engines exceed the 
CO2 FEL that applied during the model year (or the 
CO2 emission standard if the family did not generate or use 
emission credits). We may consider any available information in making 
our decision to approve or deny your request.
    (b) If we approve your request under this section, you must apply 
emission credits to cover the increased FEL for all affected engines. 
Apply the emission credits as part of your credit demonstration for the 
current production year. Include the appropriate calculations in your 
final report under Sec.  1036.730.
    (c) Submit your request to the Designated Compliance Officer. 
Include the following in your request:
    (1) Identify the names of each engine family that is the subject of 
your request. Include separate family names for different model years
    (2) Describe why your request does not apply for similar engine 
models or additional model years, as applicable.
    (3) Identify the FEL(s) that applied during the model year and 
recommend a replacement FEL for in-use engines; include a supporting 
rationale to describe how you determined the recommended replacement 
FEL.
    (4) Describe whether the needed emission credits will come from 
averaging, banking, or trading.
    (d) If we approve your request, we will identify the replacement 
FEL. The value we select will reflect our best judgment to accurately 
reflect the actual in-use performance of your engines, consistent with 
the testing provisions specified in this part. We may apply the higher 
FELs to other engine families from the same or different model years to 
the extent they used equivalent emission controls. We may include any 
appropriate conditions with our approval.
    (e) If we order a recall for an engine family under 40 CFR 
1068.505, we will no longer approve a replacement FEL under this 
section for any of your engines from that engine family, or from any 
other engine family that relies on equivalent emission controls.

Sec.  1036.630  Certification of engine greenhouse gas emissions for 
powertrain testing.

    For engines included in powertrain families under 40 CFR part 1037, 
you may choose to include the corresponding engine emissions in your 
engine families under this part instead of (or in addition to) the 
otherwise applicable engine fuel maps.
    (a) If you choose to certify powertrain fuel maps in an engine 
family, the declared powertrain emission levels become standards that 
apply for selective enforcement audits and in-use testing. We may 
require that you provide to us the engine cycle (not normalized) 
corresponding to a given powertrain for each of the specified duty 
cycles.
    (b) If you choose to certify only fuel map emissions for an engine 
family and to not certify emissions over powertrain cycles under 40 CFR 
1037.550, we will not presume you are responsible for emissions over 
the powertrain cycles. However, where we determine that you are 
responsible in whole or in part for the emission exceedance in such 
cases, we may require that you participate in any recall of the 
affected vehicles. Note that this provision to limit your 
responsibility does not apply if you also hold the certificate of 
conformity for the vehicle.
    (c) If you split an engine family into subfamilies based on 
different fuel-mapping procedures as described in Sec.  1036.230(f)(2), 
the fuel-mapping procedures you identify for certifying each subfamily 
also apply for selective enforcement audits and in-use testing.

Sec.  1036.655  Special provisions for diesel-fueled engines sold in 
American Samoa or the Commonwealth of the Northern Mariana Islands.

    (a) The prohibitions in Sec.  1068.101(a)(1) do not apply to 
diesel-fueled engines that are intended for use and will be used in 
American Samoa or the Commonwealth of the Northern Mariana Islands, 
subject to the following conditions:
    (1) The engine meets the emission standards that applied to model 
year 2006 engines as specified in appendix A of this part.
    (2) You meet all the requirements of 40 CFR 1068.265.
    (b) If you introduce an engine into U.S. commerce under this 
section, you must meet the labeling requirements in Sec.  1036.135, but 
add the following statement instead of the compliance statement in 
Sec.  1036.135(c)(8):

[[Page 4545]]

    THIS ENGINE (or VEHICLE, as applicable) CONFORMS TO US EPA EMISSION 
STANDARDS APPLICABLE TO MODEL YEAR 2006. THIS ENGINE (or VEHICLE, as 
applicable) DOES NOT CONFORM TO US EPA EMISSION REQUIREMENTS IN EFFECT 
AT TIME OF PRODUCTION AND MAY NOT BE IMPORTED INTO THE UNITED STATES OR 
ANY TERRITORY OF THE UNITED STATES EXCEPT AMERICAN SAMOA OR THE 
COMMONWEALTH OF THE NORTHERN MARIANA ISLANDS.
    (c) Introducing into U.S. commerce an engine exempted under this 
section in any state or territory of the United States other than 
American Samoa or the Commonwealth of the Northern Mariana Islands, 
throughout its lifetime, violates the prohibitions in 40 CFR 
1068.101(a)(1), unless it is exempt under a different provision.
    (d) The exemption provisions in this section also applied for model 
year 2007 and later engines introduced into commerce in Guam before 
January 1, 2024.

Subpart H--Averaging, Banking, and Trading for Certification

Sec.  1036.701  General provisions.

    (a) You may average, bank, and trade (ABT) emission credits for 
purposes of certification as described in this subpart and in subpart B 
of this part to show compliance with the standards of Sec. Sec.  
1036.104 and 1036.108. Participation in this program is voluntary. Note 
that certification to NOX standards in Sec.  1036.104 is 
based on a family emission limit (FEL) and certification to 
CO2 standards in Sec.  1036.108 is based on a Family 
Certification Level (FCL). This part refers to ``FEL/FCL'' to 
simultaneously refer to FELs for NOX and FCLs for 
CO2. Note also that subpart B of this part requires you to 
assign an FCL to all engine families, whether or not they participate 
in the ABT provisions of this subpart.
    (b) The definitions of subpart I of this part apply to this subpart 
in addition to the following definitions:
    (1) Actual emission credits means emission credits you have 
generated that we have verified by reviewing your final report.
    (2) Averaging set means a set of engines in which emission credits 
may be exchanged. See Sec.  1036.740.
    (3) Broker means any entity that facilitates a trade of emission 
credits between a buyer and seller.
    (4) Buyer means the entity that receives emission credits as a 
result of a trade.
    (5) Reserved emission credits means emission credits you have 
generated that we have not yet verified by reviewing your final report.
    (6) Seller means the entity that provides emission credits during a 
trade.
    (7) Standard means the emission standard that applies under subpart 
B of this part for engines not participating in the ABT program of this 
subpart.
    (8) Trade means to exchange emission credits, either as a buyer or 
seller.
    (c) Emission credits may be exchanged only within an averaging set, 
except as specified in Sec.  1036.740.
    (d) You may not use emission credits generated under this subpart 
to offset any emissions that exceed an FEL/FCL or standard. This 
paragraph (d) applies for all testing, including certification testing, 
in-use testing, selective enforcement audits, and other production-line 
testing. However, if emissions from an engine exceed an FEL/FCL or 
standard (for example, during a selective enforcement audit), you may 
use emission credits to recertify the engine family with a higher FEL/
FCL that applies only to future production.
    (e) You may use either of the following approaches to retire or 
forego emission credits:
    (1) You may retire emission credits generated from any number of 
your engines. This may be considered donating emission credits to the 
environment. Identify any such credits in the reports described in 
Sec.  1036.730. Engines must comply with the applicable FELs even if 
you donate or sell the corresponding emission credits. Donated credits 
may no longer be used by anyone to demonstrate compliance with any EPA 
emission standards.
    (2) You may certify an engine family using an FEL/FCL below the 
emission standard as described in this part and choose not to generate 
emission credits for that family. If you do this, you do not need to 
calculate emission credits for those engine families, and you do not 
need to submit or keep the associated records described in this subpart 
for that family.
    (f) Emission credits may be used in the model year they are 
generated. Surplus emission credits may be banked for future model 
years. Surplus emission credits may sometimes be used for past model 
years, as described in Sec.  1036.745.
    (g) You may increase or decrease an FEL/FCL during the model year 
by amending your application for certification under Sec.  1036.225. 
The new FEL/FCL may apply only to engines you have not already 
introduced into commerce.
    (h) See Sec.  1036.740 for special credit provisions that apply for 
greenhouse gas credits generated under 40 CFR 86.1819-14(k)(7) or Sec.  
1036.615 or 40 CFR 1037.615.
    (i) Unless the regulations in this part explicitly allow it, you 
may not calculate Phase 1 credits more than once for any emission 
reduction. For example, if you generate Phase 1 CO2 emission 
credits for a hybrid engine under this part for a given vehicle, no one 
may generate CO2 emission credits for that same hybrid 
engine and the associated vehicle under 40 CFR part 1037. However, 
Phase 1 credits could be generated for identical vehicles using engines 
that did not generate credits under this part.
    (j) Credits you generate with compression-ignition engines in 2020 
and earlier model years may be used in model year 2021 and later as 
follows:
    (1) For credit-generating engines certified to the tractor engine 
standards in Sec.  1036.108, you may use credits calculated relative to 
the tractor engine standards.
    (2) For credit-generating engines certified to the vocational 
engine standards in Sec.  1036.108, you may optionally carry over 
adjusted vocational credits from an averaging set, and you may use 
credits calculated relative to the emission levels in the following 
table:

   Table 1 to Paragraph (j)(2) of Sec.   1036.701--Emission Levels for
                           Credit Calculation
------------------------------------------------------------------------
                Medium HDE                            Heavy HDE
------------------------------------------------------------------------
558 g/hp[middot]hr........................  525 g/hp[middot]hr.
------------------------------------------------------------------------

    (k) Engine families you certify with a nonconformance penalty under 
40 CFR part 86, subpart L, may not generate emission credits.

Sec.  1036.705  Generating and calculating emission credits.

    (a) The provisions of this section apply separately for calculating 
emission credits for each pollutant.
    (b) For each participating family, calculate positive or negative 
emission credits relative to the otherwise applicable emission 
standard. Calculate positive emission credits for a family that has an 
FEL/FCL below the standard. Calculate negative emission credits for a 
family that has an FEL/FCL above the standard. Sum your positive and 
negative credits for the model year before rounding.

[[Page 4546]]

    (1) Calculate emission credits to the nearest megagram (Mg) for 
each family or subfamily using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.077

Where:

Std = the emission standard, in (mg NOX)/hp[middot]hr or 
(g CO2)/hp[middot]hr, that applies under subpart B of 
this part for engines not participating in the ABT program of this 
subpart (the ``otherwise applicable standard'').
FL = the engine family's FEL for NOX, in mg/hp[middot]hr, 
and FCL for CO2, in g/hp[middot]hr, rounded to the same 
number of decimal places as the emission standard.
CF = a transient cycle conversion factor (hp[middot]hr/mile), 
calculated by dividing the total (integrated) horsepower-hour over 
the applicable duty cycle by 6.3 miles for engines subject to spark-
ignition standards and 6.5 miles for engines subject to compression-
ignition standards. This represents the average work performed over 
the duty cycle. See paragraph (b)(3) of this section for provisions 
that apply for CO2.
Volume = the number of engines eligible to participate in the 
averaging, banking, and trading program within the given engine 
family or subfamily during the model year, as described in paragraph 
(c) of this section.
UL = the useful life for the standard that applies for a given 
primary intended service class, in miles.
c = use 10-\6\ for CO2 and 10-\9\ 
for NOX.

Example for Model Year 2025 Heavy HDE Generating CO2 Credits 
for a Model Year 2028 Heavy HDE:

Std = 432 g/hp[middot]hr
FL = 401 g/hp[middot]hr
CF = 9.78 hp[middot]hr/mile
Volume = 15,342
UL = 435,000 miles
c = 10-\6\
Emission credits = (432 - 401) [middot] 9.78 [middot] 15,342 [middot] 
435,000 [middot] 10-\6\
Emission credits = 28,131,142 Mg
    (2) [Reserved]
    (3) The following additional provisions apply for calculating 
CO2 credits:
    (i) For engine families certified to both the vocational and 
tractor engine standards, calculate credits separately for the 
vocational engines and the tractor engines. We may allow you to use 
statistical methods to estimate the total production volumes where a 
small fraction of the engines cannot be tracked precisely.
    (ii) Calculate the transient cycle conversion factor for vocational 
engines based on the average of vocational engine configurations 
weighted by their production volumes. Similarly, calculate the 
transient cycle conversion factor for tractor engines based on the 
average of tractor engine configurations weighted by their production 
volumes. Note that calculating the transient cycle conversion factor 
for tractors requires you to use the conversion factor even for engines 
certified to standards based on the SET duty cycle.
    (iii) The FCL for CO2 is based on measurement over the 
FTP duty cycle for vocational engines and over the SET duty cycle for 
tractor engines.
    (4) You may not generate emission credits for tractor engines 
(i.e., engines not certified to the transient cycle for CO2) 
installed in vocational vehicles (including vocational tractors 
certified under 40 CFR 1037.630 or exempted under 40 CFR 1037.631). We 
will waive this provision where you demonstrate that less than five 
percent of the engines in your tractor family were installed in 
vocational vehicles. For example, if you know that 96 percent of your 
tractor engines were installed in non-vocational tractors but cannot 
determine the vehicle type for the remaining four percent, you may 
generate credits for all the engines in the family.
    (5) You may generate CO2 emission credits from a model 
year 2021 or later medium heavy-duty engine family subject to spark-
ignition standards for exchanging with other engine families only if 
the engines in the family are gasoline-fueled. You may generate 
CO2 credits from non-gasoline engine families only for the 
purpose of offsetting CH4 and/or N2O emissions 
within the same engine family as described in paragraph (d) of this 
section.
    (c) As described in Sec.  1036.730, compliance with the 
requirements of this subpart is determined at the end of the model year 
based on actual U.S.-directed production volumes. Keep appropriate 
records to document these production volumes. Do not include any of the 
following engines to calculate emission credits:
    (1) Engines that you do not certify to the CO2 standards 
of this part because they are permanently exempted under subpart G of 
this part or under 40 CFR part 1068.
    (2) Exported engines.
    (3) Engines not subject to the requirements of this part, such as 
those excluded under Sec.  1036.5. For example, do not include engines 
used in vehicles certified to the greenhouse gas standards of 40 CFR 
86.1819.
    (4) Any other engines if we indicate elsewhere in this part that 
they are not to be included in the calculations of this subpart.
    (d) You may use CO2 emission credits to show compliance 
with CH4 and/or N2O FELs instead of the otherwise 
applicable emission standards. To do this, calculate the CH4 
and/or N2O emission credits needed (negative credits) using 
the equation in paragraph (b) of this section, using the FEL(s) you 
specify for your engines during certification instead of the FCL. You 
must use 34 Mg of positive CO2 credits to offset 1 Mg of 
negative CH4 credits for model year 2021 and later engines, 
and you must use 25 Mg of positive CO2 credits to offset 1 
Mg of negative CH4 credits for earlier engines. You must use 
298 Mg of positive CO2 credits to offset 1 Mg of negative 
N2O credits.

Sec.  1036.710  Averaging.

    (a) Averaging is the exchange of emission credits among your engine 
families. You may average emission credits only within the same 
averaging set, except as specified in Sec.  1036.740.
    (b) You may certify one or more engine families to an FEL/FCL above 
the applicable standard, subject to any applicable FEL caps and other 
the provisions in subpart B of this part, if you show in your 
application for certification that your projected balance of all 
emission-credit transactions in that model year is greater than or 
equal to zero, or that a negative balance is allowed under Sec.  
1036.745.
    (c) If you certify an engine family to an FEL/FCL that exceeds the 
otherwise applicable standard, you must obtain enough emission credits 
to offset the engine family's deficit by the due date for the final 
report required in Sec.  1036.730. The emission credits used to address 
the deficit may come from your other engine families that generate 
emission credits in the same model year (or from later model years as 
specified in Sec.  1036.745), from emission credits you have banked, or 
from emission credits you obtain through trading.

Sec.  1036.715  Banking.

    (a) Banking is the retention of surplus emission credits by the 
manufacturer generating the emission credits for use in future model 
years for averaging or trading.

[[Page 4547]]

    (b) You may designate any emission credits you plan to bank in the 
reports you submit under Sec.  1036.730 as reserved credits. During the 
model year and before the due date for the final report, you may 
designate your reserved emission credits for averaging or trading.
    (c) Reserved credits become actual emission credits when you submit 
your final report. However, we may revoke these emission credits if we 
are unable to verify them after reviewing your reports or auditing your 
records.
    (d) Banked credits retain the designation of the averaging set in 
which they were generated.

Sec.  1036.720  Trading.

    (a) Trading is the exchange of emission credits between 
manufacturers. You may use traded emission credits for averaging, 
banking, or further trading transactions. Traded emission credits 
remain subject to the averaging-set restrictions based on the averaging 
set in which they were generated.
    (b) You may trade actual emission credits as described in this 
subpart. You may also trade reserved emission credits, but we may 
revoke these emission credits based on our review of your records or 
reports or those of the company with which you traded emission credits. 
You may trade banked credits within an averaging set to any certifying 
manufacturer.
    (c) If a negative emission credit balance results from a 
transaction, both the buyer and seller are liable, except in cases we 
deem to involve fraud. See Sec.  1036.255(e) for cases involving fraud. 
We may void the certificates of all engine families participating in a 
trade that results in a manufacturer having a negative balance of 
emission credits. See Sec.  1036.745.

Sec.  1036.725  Required information for certification.

    (a) You must declare in your application for certification your 
intent to use the provisions of this subpart for each engine family 
that will be certified using the ABT program. You must also declare the 
FEL/FCL you select for the engine family for each pollutant for which 
you are using the ABT program. Your FELs must comply with the 
specifications of subpart B of this part, including the FEL caps.
    (b) Include the following in your application for certification:
    (1) A statement that, to the best of your belief, you will not have 
a negative balance of emission credits for any averaging set when all 
emission credits are calculated at the end of the year; or a statement 
that you will have a negative balance of emission credits for one or 
more averaging sets, but that it is allowed under Sec.  1036.745.
    (2) Detailed calculations of projected emission credits (positive 
or negative) based on projected U.S.-directed production volumes. We 
may require you to include similar calculations from your other engine 
families to project your net credit balances for the model year. If you 
project negative emission credits for a family, state the source of 
positive emission credits you expect to use to offset the negative 
emission credits.

Sec.  1036.730  ABT reports.

    (a) If you certify any of your engine families using the ABT 
provisions of this subpart, you must send us a final report by 
September 30 following the end of the model year.
    (b) Your report must include the following information for each 
engine family participating in the ABT program:
    (1) Engine-family designation and averaging set.
    (2) The emission standards that would otherwise apply to the engine 
family.
    (3) The FEL/FCL for each pollutant. If you change the FEL/FCL after 
the start of production, identify the date that you started using the 
new FEL/FCL and/or give the engine identification number for the first 
engine covered by the new FEL/FCL. In this case, identify each 
applicable FEL/FCL and calculate the positive or negative emission 
credits as specified in Sec.  1036.225(f).
    (4) The projected and actual U.S.-directed production volumes for 
the model year. If you changed an FEL/FCL during the model year, 
identify the actual U.S.-directed production volume associated with 
each FEL/FCL.
    (5) The transient cycle conversion factor for each engine 
configuration as described in Sec.  1036.705.
    (6) Useful life.
    (7) Calculated positive or negative emission credits for the whole 
engine family. Identify any emission credits that you traded, as 
described in paragraph (d)(1) of this section.
    (c) Your report must include the following additional information:
    (1) Show that your net balance of emission credits from all your 
participating engine families in each averaging set in the applicable 
model year is not negative, except as allowed under Sec.  1036.745. 
Your credit tracking must account for the limitation on credit life 
under Sec.  1036.740(d).
    (2) State whether you will reserve any emission credits for 
banking.
    (3) State that the report's contents are accurate.
    (d) If you trade emission credits, you must send us a report within 
90 days after the transaction, as follows:
    (1) As the seller, you must include the following information in 
your report:
    (i) The corporate names of the buyer and any brokers.
    (ii) A copy of any contracts related to the trade.
    (iii) The averaging set corresponding to the engine families that 
generated emission credits for the trade, including the number of 
emission credits from each averaging set.
    (2) As the buyer, you must include the following information in 
your report:
    (i) The corporate names of the seller and any brokers.
    (ii) A copy of any contracts related to the trade.
    (iii) How you intend to use the emission credits, including the 
number of emission credits you intend to apply for each averaging set.
    (e) Send your reports electronically to the Designated Compliance 
Officer using an approved information format. If you want to use a 
different format, send us a written request with justification for a 
waiver.
    (f) Correct errors in your report as follows:
    (1) If you or we determine by September 30 after the end of the 
model year that errors mistakenly decreased your balance of emission 
credits, you may correct the errors and recalculate the balance of 
emission credits. You may not make these corrections for errors that 
are determined later than September 30 after the end of the model year. 
If you report a negative balance of emission credits, we may disallow 
corrections under this paragraph (f)(1).
    (2) If you or we determine any time that errors mistakenly 
increased your balance of emission credits, you must correct the errors 
and recalculate the balance of emission credits.

Sec.  1036.735  Recordkeeping.

    (a) You must organize and maintain your records as described in 
this section. We may review your records at any time.
    (b) Keep the records required by this section for at least eight 
years after the due date for the end-of-year report. You may not use 
emission credits for any engines if you do not keep all the records 
required under this section. You must therefore keep these records to 
continue to bank valid credits. Store these records in any format and 
on any media, as long as you can promptly send us organized, written 
records in English if we ask for them. You must keep these records 
readily available. We may review them at any time.

[[Page 4548]]

    (c) Keep a copy of the reports we require in Sec. Sec.  1036.725 
and 1036.730.
    (d) Keep records of the engine identification number (usually the 
serial number) for each engine you produce that generates or uses 
emission credits under the ABT program. You may identify these numbers 
as a range. If you change the FEL/FCL after the start of production, 
identify the date you started using each FEL/FCL and the range of 
engine identification numbers associated with each FEL/FCL. You must 
also identify the purchaser and destination for each engine you produce 
to the extent this information is available.
    (e) We may require you to keep additional records or to send us 
relevant information not required by this section in accordance with 
the Clean Air Act.

Sec.  1036.740  Restrictions for using emission credits.

    The following restrictions apply for using emission credits:
    (a) Averaging sets. Except as specified in paragraph (c) of this 
section, emission credits may be exchanged only within the following 
averaging sets based on primary intended service class:
    (1) Spark-ignition HDE.
    (2) Light HDE.
    (3) Medium HDE.
    (4) Heavy HDE.
    (b) Applying credits to prior year deficits. Where your 
CO2 credit balance for the previous year is negative, you 
may apply credits to that deficit only after meeting your credit 
obligations for the current year.
    (c) CO2 credits from hybrid engines and other advanced 
technologies. Phase 1 CO2 credits you generate under Sec.  
1036.615 may be used for any of the averaging sets identified in 
paragraph (a) of this section; you may also use those credits to 
demonstrate compliance with the CO2 emission standards in 40 
CFR 86.1819 and 40 CFR part 1037. Similarly, you may use Phase 1 
advanced-technology credits generated under 40 CFR 86.1819-14(k)(7) or 
40 CFR 1037.615 to demonstrate compliance with the CO2 
standards in this part. In the case of Spark-ignition HDE and Light HDE 
you may not use more than 60,000 Mg of credits from other averaging 
sets in any model year.
    (1) The maximum CO2 credits you may bring into the 
following service class groups is 60,000 Mg per model year:
    (i) Spark-ignition HDE, Light HDE, and Light HDV. This group 
comprises the averaging sets listed in paragraphs (a)(1) and (2) of 
this section and the averaging set listed in 40 CFR 1037.740(a)(1).
    (ii) Medium HDE and Medium HDV. This group comprises the averaging 
sets listed in paragraph (a)(3) of this section and 40 CFR 
1037.740(a)(2).
    (iii) Heavy HDE and Heavy HDV. This group comprises the averaging 
sets listed in paragraph (a)(4) of this section and 40 CFR 
1037.740(a)(3).
    (2) Paragraph (c)(1) of this section does not limit the advanced-
technology credits that can be used within a service class group if 
they were generated in that same service class group.
    (d) NOX and CO2 credit life. NOX and CO2 
credits may be used only for five model years after the year in which 
they are generated. For example, credits you generate in model year 
2027 may be used to demonstrate compliance with emission standards only 
through model year 2032.
    (e) Other restrictions. Other sections of this part specify 
additional restrictions for using emission credits under certain 
special provisions.

Sec.  1036.745  End-of-year CO2 credit deficits.

    Except as allowed by this section, we may void the certificate of 
any engine family certified to an FCL above the applicable standard for 
which you do not have sufficient credits by the deadline for submitting 
the final report.
    (a) Your certificate for an engine family for which you do not have 
sufficient CO2 credits will not be void if you remedy the 
deficit with surplus credits within three model years. For example, if 
you have a credit deficit of 500 Mg for an engine family at the end of 
model year 2015, you must generate (or otherwise obtain) a surplus of 
at least 500 Mg in that same averaging set by the end of model year 
2018.
    (b) You may not bank or trade away CO2 credits in the 
averaging set in any model year in which you have a deficit.
    (c) You may apply only surplus credits to your deficit. You may not 
apply credits to a deficit from an earlier model year if they were 
generated in a model year for which any of your engine families for 
that averaging set had an end-of-year credit deficit.
    (d) You must notify us in writing how you plan to eliminate the 
credit deficit within the specified time frame. If we determine that 
your plan is unreasonable or unrealistic, we may deny an application 
for certification for a vehicle family if its FEL would increase your 
credit deficit. We may determine that your plan is unreasonable or 
unrealistic based on a consideration of past and projected use of 
specific technologies, the historical sales mix of your vehicle models, 
your commitment to limit production of higher-emission vehicles, and 
expected access to traded credits. We may also consider your plan 
unreasonable if your credit deficit increases from one model year to 
the next. We may require that you send us interim reports describing 
your progress toward resolving your credit deficit over the course of a 
model year.
    (e) If you do not remedy the deficit with surplus credits within 
three model years, we may void your certificate for that engine family. 
We may void the certificate based on your end-of-year report. Note that 
voiding a certificate applies ab initio. Where the net deficit is less 
than the total amount of negative credits originally generated by the 
family, we will void the certificate only with respect to the number of 
engines needed to reach the amount of the net deficit. For example, if 
the original engine family generated 500 Mg of negative credits, and 
the manufacturer's net deficit after three years was 250 Mg, we would 
void the certificate with respect to half of the engines in the family.
    (f) For purposes of calculating the statute of limitations, the 
following actions are all considered to occur at the expiration of the 
deadline for offsetting a deficit as specified in paragraph (a) of this 
section:
    (1) Failing to meet the requirements of paragraph (a) of this 
section.
    (2) Failing to satisfy the conditions upon which a certificate was 
issued relative to offsetting a deficit.
    (3) Selling, offering for sale, introducing or delivering into U.S. 
commerce, or importing vehicles that are found not to be covered by a 
certificate as a result of failing to offset a deficit.

Sec.  1036.750  Consequences for noncompliance.

    (a) For each engine family participating in the ABT program, the 
certificate of conformity is conditioned upon full compliance with the 
provisions of this subpart during and after the model year. You are 
responsible to establish to our satisfaction that you fully comply with 
applicable requirements. We may void the certificate of conformity for 
an engine family if you fail to comply with any provisions of this 
subpart.
    (b) You may certify your engine family to an FEL/FCL above an 
applicable standard based on a projection that you will have enough 
emission credits to offset the deficit for the engine family. See Sec.  
1036.745 for provisions specifying what happens if you cannot show in 
your final report that you have enough actual emission

[[Page 4549]]

credits to offset a deficit for any pollutant in an engine family.
    (c) We may void the certificate of conformity for an engine family 
if you fail to keep records, send reports, or give us information we 
request. Note that failing to keep records, send reports, or give us 
information we request is also a violation of 42 U.S.C. 7522(a)(2).
    (d) You may ask for a hearing if we void your certificate under 
this section (see Sec.  1036.820).

Sec.  1036.755  Information provided to the Department of 
Transportation.

    After receipt of each manufacturer's final report as specified in 
Sec.  1036.730 and completion of any verification testing required to 
validate the manufacturer's submitted final data, we will issue a 
report to the Department of Transportation with CO2 emission 
information and will verify the accuracy of each manufacturer's 
equivalent fuel consumption data that required by NHTSA under 49 CFR 
535.8. We will send a report to DOT for each engine manufacturer based 
on each regulatory category and subcategory, including sufficient 
information for NHTSA to determine fuel consumption and associated 
credit values. See 49 CFR 535.8 to determine if NHTSA deems submission 
of this information to EPA to also be a submission to NHTSA.

Subpart I--Definitions and Other Reference Information

Sec.  1036.801  Definitions.

    The following definitions apply to this part. The definitions apply 
to all subparts unless we note otherwise. All undefined terms have the 
meaning the Act gives to them. The definitions follow:
    Act means the Clean Air Act, as amended, 42 U.S.C. 7401-7671q.
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
    Advanced technology means technology certified under 40 CFR 
86.1819-14(k)(7), Sec.  1036.615, or 40 CFR 1037.615.
    Aftertreatment means relating to a catalytic converter, particulate 
filter, or any other system, component, or technology mounted 
downstream of the exhaust valve (or exhaust port) whose design function 
is to decrease emissions in the engine exhaust before it is exhausted 
to the environment. Exhaust gas recirculation (EGR) and turbochargers 
are not aftertreatment.
    Aircraft means any vehicle capable of sustained air travel more 
than 100 feet above the ground.
    Alcohol-fueled engine mean an engine that is designed to run using 
an alcohol fuel. For purposes of this definition, alcohol fuels do not 
include fuels with a nominal alcohol content below 25 percent by 
volume.
    Auxiliary emission control device means any element of design that 
senses temperature, motive speed, engine speed (r/min), transmission 
gear, or any other parameter for the purpose of activating, modulating, 
delaying, or deactivating the operation of any part of the emission 
control system.
    Averaging set has the meaning given in Sec.  1036.740.
    Calibration means the set of specifications and tolerances specific 
to a particular design, version, or application of a component or 
assembly capable of functionally describing its operation over its 
working range.
    Carryover means relating to certification based on emission data 
generated from an earlier model year as described in Sec.  1036.235(d).
    Certification means relating to the process of obtaining a 
certificate of conformity for an engine family that complies with the 
emission standards and requirements in this part.
    Certified emission level means the highest deteriorated emission 
level in an engine family for a given pollutant from the applicable 
transient and/or steady-state testing, rounded to the same number of 
decimal places as the applicable standard. Note that you may have two 
certified emission levels for CO2 if you certify a family 
for both vocational and tractor use.
    Charge-depleting has the meaning given in 40 CFR 1066.1001.
    Charge-sustaining has the meaning given in 40 CFR 1066.1001.
    Complete vehicle means a vehicle meeting the definition of complete 
vehicle in 40 CFR 1037.801 when it is first sold as a vehicle. For 
example, where a vehicle manufacturer sells an incomplete vehicle to a 
secondary vehicle manufacturer, the vehicle is not a complete vehicle 
under this part, even after its final assembly.
    Compression-ignition means relating to a type of reciprocating, 
internal-combustion engine that is not a spark-ignition engine. Note 
that Sec.  1036.1 also deems gas turbine engines and other engines to 
be compression-ignition engines.
    Crankcase emissions means airborne substances emitted to the 
atmosphere from any part of the engine crankcase's ventilation or 
lubrication systems. The crankcase is the housing for the crankshaft 
and other related internal parts.
    Criteria pollutants means emissions of NOX, HC, PM, and 
CO.
    Critical emission-related component has the meaning given in 40 CFR 
1068.30.
    Defeat device has the meaning given in Sec.  1036.115(h).
    Designated Compliance Officer means one of the following:
    (1) For engines subject to compression-ignition standards, 
Designated Compliance Officer means Director, Diesel Engine Compliance 
Center, U.S. Environmental Protection Agency, 2000 Traverwood Drive, 
Ann Arbor, MI 48105; [email protected]; www.epa.gov/ve-certification.
    (2) For engines subject to spark-ignition standards, Designated 
Compliance Officer means Director, Gasoline Engine Compliance Center, 
U.S. Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor, 
MI 48105; [email protected]; www.epa.gov/ve-certification.
    Deteriorated emission level means the emission level that results 
from applying the appropriate deterioration factor to the official 
emission result of the emission-data engine. Note that where no 
deterioration factor applies, references in this part to the 
deteriorated emission level mean the official emission result.
    Deterioration factor means the relationship between emissions at 
the end of useful life (or point of highest emissions if it occurs 
before the end of useful life) and emissions at the low-hour/low-
mileage point, expressed in one of the following ways:
    (1) For multiplicative deterioration factors, the ratio of 
emissions at the end of useful life (or point of highest emissions) to 
emissions at the low-hour point.
    (2) For additive deterioration factors, the difference between 
emissions at the end of useful life (or point of highest emissions) and 
emissions at the low-hour point.
    Diesel exhaust fluid (DEF) means a liquid reducing agent (other 
than the engine fuel) used in conjunction with selective catalytic 
reduction to reduce NOX emissions. Diesel exhaust fluid is 
generally understood to be an aqueous solution of urea conforming to 
the specifications of ISO 22241.
    Dual-fuel means relating to an engine designed for operation on two 
different types of fuel but not on a continuous mixture of those fuels 
(see Sec.  1036.601(d)). For purposes of this part, such an engine 
remains a dual-fuel engine even if it is designed for operation on 
three or more different fuels.
    Electronic control module (ECM) means an engine's electronic device 
that

[[Page 4550]]

uses data from engine sensors to control engine parameters.
    Emergency vehicle has the meaning given in 40 CFR 1037.801.
    Emission control system means any device, system, or element of 
design that controls or reduces the emissions of regulated pollutants 
from an engine.
    Emission-data engine means an engine that is tested for 
certification. This includes engines tested to establish deterioration 
factors.
    Emission-related component has the meaning given in 40 CFR part 
1068, appendix A.
    Emission-related maintenance means maintenance that substantially 
affects emissions or is likely to substantially affect emission 
deterioration.
    Engine configuration means a unique combination of engine hardware 
and calibration (related to the emission standards) within an engine 
family, which would include hybrid components for engines certified as 
hybrid engines and hybrid powertrains. Engines within a single engine 
configuration differ only with respect to normal production variability 
or factors unrelated to compliance with emission standards.
    Engine family has the meaning given in Sec.  1036.230.
    Excluded means relating to engines that are not subject to some or 
all of the requirements of this part as follows:
    (1) An engine that has been determined not to be a heavy-duty 
engine is excluded from this part.
    (2) Certain heavy-duty engines are excluded from the requirements 
of this part under Sec.  1036.5.
    (3) Specific regulatory provisions of this part may exclude a 
heavy-duty engine generally subject to this part from one or more 
specific standards or requirements of this part.
    Exempted has the meaning given in 40 CFR 1068.30.
    Exhaust gas recirculation means a technology that reduces emissions 
by routing exhaust gases that had been exhausted from the combustion 
chamber(s) back into the engine to be mixed with incoming air before or 
during combustion. The use of valve timing to increase the amount of 
residual exhaust gas in the combustion chamber(s) that is mixed with 
incoming air before or during combustion is not considered exhaust gas 
recirculation for the purposes of this part.
    Family certification level (FCL) means a CO2 emission 
level declared by the manufacturer that is at or above emission results 
for all emission-data engines. The FCL serves as the emission standard 
for the engine family with respect to certification testing if it is 
different than the otherwise applicable standard.
    Family emission limit (FEL) means one of the following:
    (1) For NOX emissions, family emission limit means a 
NOX emission level declared by the manufacturer to serve in 
place of an otherwise applicable emission standard under the ABT 
program in subpart H of this part. The FEL serves as the emission 
standard for the engine family with respect to all required testing.
    (2) For greenhouse gas standards, family emission limit means an 
emission level that serves as the standard that applies for testing 
individual certified engines. The CO2 FEL is equal to the 
CO2 FCL multiplied by 1.03 and rounded to the same number of 
decimal places as the standard.
    Federal Test Procedure (FTP) means the applicable transient duty 
cycle described in Sec.  1036.512 designed to measure exhaust emissions 
during urban driving.
    Flexible-fuel means relating to an engine designed for operation on 
any mixture of two or more different types of fuels (see Sec.  
1036.601(d)).
    Fuel type means a general category of fuels such as diesel fuel, 
gasoline, or natural gas. There can be multiple grades within a single 
fuel type, such as premium gasoline, regular gasoline, or gasoline with 
10 percent ethanol.
    Good engineering judgment has the meaning given in 40 CFR 1068.30. 
See 40 CFR 1068.5 for the administrative process we use to evaluate 
good engineering judgment.
    Greenhouse gas means one or more compounds regulated under this 
part based primarily on their impact on the climate. This generally 
includes CO2, CH4, and N2O.
    Greenhouse gas Emissions Model (GEM) means the GEM simulation tool 
described in 40 CFR 1037.520. Note that an updated version of GEM 
applies starting in model year 2021.
    Gross vehicle weight rating (GVWR) means the value specified by the 
vehicle manufacturer as the maximum design loaded weight of a single 
vehicle, consistent with good engineering judgment.
    Heavy-duty engine means any engine which the engine manufacturer 
could reasonably expect to be used for motive power in a heavy-duty 
vehicle. For purposes of this definition in this part, the term 
``engine'' includes internal combustion engines and other devices that 
convert chemical fuel into motive power. For example, a gas turbine 
used in a heavy-duty vehicle is a heavy-duty engine.
    Heavy-duty vehicle means any motor vehicle above 8,500 pounds GVWR. 
An incomplete vehicle is also a heavy-duty vehicle if it has a curb 
weight above 6,000 pounds or a basic vehicle frontal area greater than 
45 square feet. Curb weight and basic vehicle frontal area have the 
meaning given in 40 CFR 86.1803-01.
    Hybrid means an engine or powertrain that includes energy storage 
features other than a conventional battery system or conventional 
flywheel. Supplemental electrical batteries and hydraulic accumulators 
are examples of hybrid energy storage systems. Note that certain 
provisions in this part treat hybrid engines and hybrid powertrains 
intended for vehicles that include regenerative braking different than 
those intended for vehicles that do not include regenerative braking.
    Hybrid engine means a hybrid system with features for storing and 
recovering energy that are integral to the engine or are otherwise 
upstream of the vehicle's transmission other than a conventional 
battery system or conventional flywheel. Supplemental electrical 
batteries and hydraulic accumulators are examples of hybrid energy 
storage systems. Examples of hybrids that could be considered hybrid 
engines are P0, P1, and P2 hybrids where hybrid features are connected 
to the front end of the engine, at the crankshaft, or connected between 
the clutch and the transmission where the clutch upstream of the hybrid 
feature is in addition to the transmission clutch(s), respectively. 
Note other examples of systems that qualify as hybrid engines are 
systems that recover kinetic energy and use it to power an electric 
heater in the aftertreatment.
    Hybrid powertrain means a powertrain that includes energy storage 
features other than a conventional battery system or conventional 
flywheel. Supplemental electrical batteries and hydraulic accumulators 
are examples of hybrid energy storage systems. Note other examples of 
systems that qualify as hybrid powertrains are systems that recover 
kinetic energy and use it to power an electric heater in the 
aftertreatment.
    Hydrocarbon (HC) has the meaning given in 40 CFR 1065.1001.
    Identification number means a unique specification (for example, a 
model number/serial number combination) that allows someone to 
distinguish a particular engine from other similar engines.
    Incomplete vehicle means a vehicle meeting the definition of 
incomplete vehicle in 40 CFR 1037.801 when it is first sold (or 
otherwise delivered to another entity) as a vehicle.

[[Page 4551]]

    Innovative technology means technology certified under Sec.  
1036.610 (also described as ``off-cycle technology'').
    Liquefied petroleum gas (LPG) means a liquid hydrocarbon fuel that 
is stored under pressure and is composed primarily of nonmethane 
compounds that are gases at atmospheric conditions. Note that, although 
this commercial term includes the word ``petroleum'', LPG is not 
considered to be a petroleum fuel under the definitions of this 
section.
    Low-hour means relating to an engine that has stabilized emissions 
and represents the undeteriorated emission level. This would generally 
involve less than 300 hours of operation for engines with 
NOX aftertreatment and 125 hours of operation for other 
engines.
    Manufacture means the physical and engineering process of 
designing, constructing, and/or assembling a heavy-duty engine or a 
heavy-duty vehicle.
    Manufacturer has the meaning given in 40 CFR 1068.30.
    Medium-duty passenger vehicle has the meaning given in 40 CFR 
86.1803.
    Mild hybrid means a hybrid engine or powertrain with regenerative 
braking capability where the system recovers less than 20 percent of 
the total braking energy over the transient cycle defined in appendix A 
of 40 CFR part 1037.
    Model year means the manufacturer's annual new model production 
period, except as restricted under this definition. It must include 
January 1 of the calendar year for which the model year is named, may 
not begin before January 2 of the previous calendar year, and it must 
end by December 31 of the named calendar year. Manufacturers may not 
adjust model years to circumvent or delay compliance with emission 
standards or to avoid the obligation to certify annually.
    Motorcoach means a heavy-duty vehicle designed for carrying 30 or 
more passengers over long distances. Such vehicles are characterized by 
row seating, rest rooms, and large luggage compartments, and facilities 
for stowing carry-on luggage.
    Motor vehicle has the meaning given in 40 CFR 85.1703.
    Natural gas means a fuel whose primary constituent is methane.
    New motor vehicle engine has the meaning given in the Act. This 
generally means a motor vehicle engine meeting any of the following:
    (1) A motor vehicle engine for which the ultimate purchaser has 
never received the equitable or legal title is a new motor vehicle 
engine. This kind of engine might commonly be thought of as ``brand 
new'' although a new motor vehicle engine may include previously used 
parts. Under this definition, the engine is new from the time it is 
produced until the ultimate purchaser receives the title or places it 
into service, whichever comes first.
    (2) An imported motor vehicle engine is a new motor vehicle engine 
if it was originally built on or after January 1, 1970.
    (3) Any motor vehicle engine installed in a new motor vehicle.
    Noncompliant engine means an engine that was originally covered by 
a certificate of conformity, but is not in the certified configuration 
or otherwise does not comply with the conditions of the certificate.
    Nonconforming engine means an engine not covered by a certificate 
of conformity that would otherwise be subject to emission standards.
    Nonmethane hydrocarbon (NMHC) means the sum of all hydrocarbon 
species except methane, as measured according to 40 CFR part 1065.
    Nonmethane hydrocarbon equivalent (NMHCE) has the meaning given in 
40 CFR 1065.1001.
    Nonmethane nonethane hydrocarbon equivalent (NMNEHC) has the 
meaning given in 40 CFR 1065.1001.
    Off-cycle technology means technology certified under Sec.  
1036.610 (also described as ``innovative technology'').
    Official emission result means the measured emission rate for an 
emission-data engine on a given duty cycle before the application of 
any deterioration factor, but after the applicability of any required 
regeneration or other adjustment factors.
    Owners manual means a document or collection of documents prepared 
by the engine or vehicle manufacturer for the owner or operator to 
describe appropriate engine maintenance, applicable warranties, and any 
other information related to operating or keeping the engine. The 
owners manual is typically provided to the ultimate purchaser at the 
time of sale. The owners manual may be in paper or electronic format.
    Oxides of nitrogen has the meaning given in 40 CFR 1065.1001.
    Percent has the meaning given in 40 CFR 1065.1001. Note that this 
means percentages identified in this part are assumed to be infinitely 
precise without regard to the number of significant figures. For 
example, one percent of 1,493 is 14.93.
    Placed into service means put into initial use for its intended 
purpose, excluding incidental use by the manufacturer or a dealer.
    Preliminary approval means approval granted by an authorized EPA 
representative prior to submission of an application for certification, 
consistent with the provisions of Sec.  1036.210.
    Primary intended service class has the meaning given in Sec.  
1036.140.
    Rechargeable Energy Storage System (RESS) has the meaning given in 
40 CFR 1065.1001.
    Relating to as used in this section means relating to something in 
a specific, direct manner. This expression is used in this section only 
to define terms as adjectives and not to broaden the meaning of the 
terms.
    Revoke has the meaning given in 40 CFR 1068.30.
    Round has the meaning given in 40 CFR 1065.1001.
    Sample means the collection of engines selected from the population 
of an engine family for emission testing. This may include testing for 
certification, production-line testing, or in-use testing.
    Scheduled maintenance means adjusting, removing, disassembling, 
cleaning, or replacing components or systems periodically to keep a 
part or system from failing, malfunctioning, or wearing prematurely.
    Small manufacturer means a manufacturer meeting the criteria 
specified in 13 CFR 121.201. The employee and revenue limits apply to 
the total number of employees and total revenue together for affiliated 
companies. Note that manufacturers with low production volumes may or 
may not be ``small manufacturers''.
    Spark-ignition means relating to a gasoline-fueled engine or any 
other type of engine with a spark plug (or other sparking device) and 
with operating characteristics significantly similar to the theoretical 
Otto combustion cycle. Spark-ignition engines usually use a throttle to 
regulate intake air flow to control power during normal operation.
    Steady-state has the meaning given in 40 CFR 1065.1001. This 
includes fuel mapping and idle testing where engine speed and load are 
held at a finite set of nominally constant values.
    Suspend has the meaning given in 40 CFR 1068.30.
    Test engine means an engine in a sample.
    Tractor means a vehicle meeting the definition of ``tractor'' in 40 
CFR 1037.801, but not classified as a ``vocational tractor'' under 40 
CFR 1037.630, or relating to such a vehicle.
    Tractor engine means an engine certified for use in tractors. Where 
an engine family is certified for use in both tractors and vocational 
vehicles, ``tractor engine'' means an engine that the engine

[[Page 4552]]

manufacturer reasonably believes will be (or has been) installed in a 
tractor. Note that the provisions of this part may require a 
manufacturer to document how it determines that an engine is a tractor 
engine.
    Ultimate purchaser means, with respect to any new engine or 
vehicle, the first person who in good faith purchases such new engine 
or vehicle for purposes other than resale.
    United States has the meaning given in 40 CFR 1068.30.
    Upcoming model year means for an engine family the model year after 
the one currently in production.
    U.S.-directed production volume means the number of engines, 
subject to the requirements of this part, produced by a manufacturer 
for which the manufacturer has a reasonable assurance that sale was or 
will be made to ultimate purchasers in the United States. This does not 
include engines certified to state emission standards that are 
different than the emission standards in this part.
    Vehicle has the meaning given in 40 CFR 1037.801.
    Vocational engine means an engine certified for use in vocational 
vehicles. Where an engine family is certified for use in both tractors 
and vocational vehicles, ``vocational engine'' means an engine that the 
engine manufacturer reasonably believes will be (or has been) installed 
in a vocational vehicle. Note that the provisions of this part may 
require a manufacturer to document how it determines that an engine is 
a vocational engine.
    Vocational vehicle means a vehicle meeting the definition of 
``vocational'' vehicle in 40 CFR 1037.801.
    Void has the meaning given in 40 CFR 1068.30.
    We (us, our) means the Administrator of the Environmental 
Protection Agency and any authorized representatives.

Sec.  1036.805  Symbols, abbreviations, and acronyms.

    The procedures in this part generally follow either the 
International System of Units (SI) or the United States customary 
units, as detailed in NIST Special Publication 811 (incorporated by 
reference in Sec.  1036.810). See 40 CFR 1065.20 for specific 
provisions related to these conventions. This section summarizes the 
way we use symbols, units of measure, and other abbreviations.
    (a) Symbols for chemical species. This part uses the following 
symbols for chemical species and exhaust constituents:

    Table 1 to Paragraph (a) of Sec.   1036.805--Symbols for Chemical
                    Species and Exhaust Constituents
------------------------------------------------------------------------
                 Symbol                              Species
------------------------------------------------------------------------
C......................................  carbon.
CH4....................................  methane.
CH4N2O.................................  urea.
CO.....................................  carbon monoxide.
CO2....................................  carbon dioxide.
H2O....................................  water.
HC.....................................  hydrocarbon.
NMHC...................................  nonmethane hydrocarbon.
NMHCE..................................  nonmethane hydrocarbon
                                          equivalent.
NMNEHC.................................  nonmethane nonethane
                                          hydrocarbon.
NO.....................................  nitric oxide.
NO2....................................  nitrogen dioxide.
NOX....................................  oxides of nitrogen.
N2O....................................  nitrous oxide.
PM.....................................  particulate matter.
------------------------------------------------------------------------

    (b) Symbols for quantities. This part uses the following symbols 
and units of measure for various quantities:

                       Table 2 to Paragraph (b) of Sec.   1036.805--Symbols for Quantities
----------------------------------------------------------------------------------------------------------------
                                                                                       Unit in terms of SI base
      Symbol             Quantity             Unit                Unit symbol                    units
----------------------------------------------------------------------------------------------------------------
[alpha]...........  atomic hydrogen-   mole per mole....  mol/mol...................  1
                     to-carbon ratio.
[Agr].............  Area.............  square meter.....  m\2\......................  m\2\
[beta]............  atomic oxygen-to-  mole per mole....  mol/mol...................  1
                     carbon ratio.
Cd[Agr]...........  drag area........  meter squared....  m\2\......................  m\2\
Crr...............  coefficient of     newton per         N/kN......................  10-\3\
                     rolling            kilonewton.
                     resistance.
D.................  distance.........  miles or meters..  mi or m...................  m
e.................  efficiency.......
[isin]............  Difference or
                     error quantity.
E.................  mass weighted      grams/ton-mile...  g/ton-mi..................  g/kg-km
                     emission result.
Eff...............  efficiency.......
Em................  mass-specific net  megajoules/        MJ/kg.....................  m\2\[middot]s-\2\
                     energy content.    kilogram.
fn................  angular speed      revolutions per    r/min.....................  [pi][middot]30[middot]s-
                     (shaft).           minute.                                        \1\
g.................  gravitational      meters per second  m/s\2\....................  m[middot]s-\2\
                     acceleration.      squared.
i.................  indexing variable
ka................  drive axle ratio.  .................  ..........................  1
ktopgear..........  highest available
                     transmission
                     gear.
m.................  Mass.............  pound mass or      lbm or kg.................  kg
                                        kilogram.
M.................  molar mass.......  gram per mole....  g/mol.....................  10-
                                                                                       \3\[middot]kg[middot]mol-
                                                                                       \1\
M.................  total number in a
                     series.

[[Page 4553]]

 
M.................  vehicle mass.....  kilogram.........  kg........................  kg
Mrotating.........  inertial mass of   kilogram.........  kg........................  kg
                     rotating
                     components.
N.................  total number in a
                     series.
Q.................  total number in a
                     series.
P.................  Power............  kilowatt.........  kW........................  10\3\[middot]m\2\[middot]k
                                                                                       g[middot]s-\3\
[rho].............  mass density.....  kilogram per       kg/m\3\...................  m-\3\[middot]kg
                                        cubic meter.
r.................  tire radius......  meter............  m.........................  m
SEE...............  standard error of
                     the estimate.
[sigma]...........  standard
                     deviation.
T.................  torque (moment of  newton meter.....  N[middot]m................  m\2\[middot]kg[middot]s-
                     force).                                                           \2\
t.................  Time.............  second...........  s.........................  s
[Delta]t..........  time interval,     second...........  s.........................  s
                     period, 1/
                     frequency.
UF................  utility factor...
v.................  Speed............  miles per hour or  mi/hr or m/s..............  m[middot]s-\1\
                                        meters per
                                        second.
W.................  Work.............  kilowatt-hour....  kW[middot]hr..............  3.6[middot]m\2\[middot]kg[
                                                                                       middot]s-\1\
wC................  carbon mass        gram/gram........  g/g.......................  1
                     fraction.
wCH4N2O...........  urea mass          gram/gram........  g/g.......................  1
                     fraction.
x.................  amount of          mole per mole....  mol/mol...................  1
                     substance mole
                     fraction.
xb................  brake energy
                     fraction.
xbl...............  brake energy
                     limit.
----------------------------------------------------------------------------------------------------------------

    (c) Superscripts. This part uses the following superscripts for 
modifying quantity symbols:

        Table 3 to Paragraph (c) of Sec.   1036.805--Superscripts
------------------------------------------------------------------------
              Superscript                            Meaning
------------------------------------------------------------------------
overbar (such as y)....................  arithmetic mean.
overdot (such as y)....................  quantity per unit time.
------------------------------------------------------------------------

    (d) Subscripts. This part uses the following subscripts for 
modifying quantity symbols:

         Table 4 to Paragraph (d) of Sec.   1036.805--Subscripts
------------------------------------------------------------------------
               Subscript                             Meaning
------------------------------------------------------------------------
65.....................................  65 miles per hour.
A......................................  A speed.
a......................................  absolute (e.g., absolute
                                          difference or error).
acc....................................  accessory.
app....................................  approved.
axle...................................  axle.
B......................................  B speed.
C......................................  C speed.
C......................................  carbon mass.
Ccombdry...............................  carbon from fuel per mole of
                                          dry exhaust.
CD.....................................  charge-depleting.
CO2DEF.................................  CO2 resulting from diesel
                                          exhaust fluid decomposition.
comb...................................  combustion.
comp...................................  composite.
cor....................................  corrected.
CS.....................................  charge-sustaining.
cycle..................................  cycle.
D......................................  distance.
D......................................  D speed.
DEF....................................  diesel exhaust fluid.
engine.................................  engine.
exh....................................  raw exhaust.
front..................................  frontal.
fuel...................................  fuel.
H2Oexhaustdry..........................  H2O in exhaust per mole of
                                          exhaust.
hi.....................................  high.
i......................................  an individual of a series.

[[Page 4554]]

 
idle...................................  idle.
int....................................  test interval.
j......................................  an individual of a series.
k......................................  an individual of a series.
m......................................  mass.
max....................................  maximum.
mapped.................................  mapped.
meas...................................  measured quantity.
MY.....................................  model year.
neg....................................  negative.
pos....................................  positive.
R......................................  range.
r......................................  relative (e.g., relative
                                          difference or error).
rate...................................  rate (divided by time).
rated..................................  rated.
record.................................  record.
ref....................................  reference quantity.
speed..................................  speed.
stall..................................  stall.
test...................................  test.
tire...................................  tire.
transient..............................  transient.
[mu]...................................  vector.
UF.....................................  utility factor.
vehicle................................  vehicle.
------------------------------------------------------------------------

    (e) Other acronyms and abbreviations. This part uses the following 
additional abbreviations and acronyms:

     Table 5 to Paragraph (e) of Sec.   1036.805--Other Acronyms and
                              Abbreviations
------------------------------------------------------------------------
                Acronym                              Meaning
------------------------------------------------------------------------
ABT....................................  averaging, banking, and
                                          trading.
AECD...................................  auxiliary emission control
                                          device.
ASTM...................................  American Society for Testing
                                          and Materials.
BTU....................................  British thermal units.
CD.....................................  charge-depleting.
CFR....................................  Code of Federal Regulations.
CI.....................................  compression-ignition.
COV....................................  coefficient of variation.
CS.....................................  charge-sustaining.
DEF....................................  diesel exhaust fluid.
DF.....................................  deterioration factor.
DOT....................................  Department of Transportation.
E85....................................  gasoline blend including
                                          nominally 85 percent denatured
                                          ethanol.
ECM....................................  Electronic Control Module.
EGR....................................  exhaust gas recirculation.
EPA....................................  Environmental Protection
                                          Agency.
FCL....................................  Family Certification Level.
FEL....................................  family emission limit.
FTP....................................  Federal Test Procedure.
GEM....................................  Greenhouse gas Emissions Model.
g/hp[middot]hr.........................  grams per brake horsepower-
                                          hour.
GPS....................................  global positioning system.
GVWR...................................  gross vehicle weight rating.
Heavy HDE..............................  heavy heavy-duty engine (see
                                          Sec.   1036.140).
Heavy HDV..............................  heavy heavy-duty vehicle (see
                                          40 CFR 1037.140).
Light HDE..............................  light heavy-duty engine (see
                                          Sec.   1036.140).
Light HDV..............................  light heavy-duty vehicle (see
                                          40 CFR 1037.140).
LLC....................................  Low Load Cycle.
LPG....................................  liquefied petroleum gas.
Medium HDE.............................  medium heavy-duty engine (see
                                          Sec.   1036.140).
Medium HDV.............................  medium heavy-duty vehicle (see
                                          40 CFR 1037.140).
NARA...................................  National Archives and Records
                                          Administration.
NHTSA..................................  National Highway Traffic Safety
                                          Administration.
NTE....................................  not-to-exceed.
PEMS...................................  portable emission measurement
                                          system.
RESS...................................  rechargeable energy storage
                                          system.

[[Page 4555]]

 
SCR....................................  selective catalytic reduction.
SEE....................................  standard error of the estimate.
SET....................................  Supplemental Emission Test.
Spark-ignition HDE.....................  spark-ignition heavy-duty
                                          engine (see Sec.   1036.140).
SI.....................................  spark-ignition.
UL.....................................  useful life.
U.S....................................  United States.
U.S.C..................................  United States Code.
------------------------------------------------------------------------

    (f) Constants. This part uses the following constants:

         Table 6 to Paragraph (f) of Sec.   1036.805--Constants
------------------------------------------------------------------------
           Symbol                   Quantity                Value
------------------------------------------------------------------------
g...........................  gravitational         9.80665 m[middot]s-
                               constant.             \2\.
R...........................  molar gas constant..  8.314472 J/
                                                     (mol[middot]K)
                                                     (m\2\[middot]kg[mid
                                                     dot]s-
                                                     \2\[middot]mol-
                                                     \1\[middot]K-\1\).
------------------------------------------------------------------------

    (g) Prefixes. This part uses the following prefixes to define a 
quantity:

          Table 7 to Paragraph (g) of Sec.   1036.805--Prefixes
------------------------------------------------------------------------
             Symbol                      Quantity              Value
------------------------------------------------------------------------
[mu]...........................  micro..................          10-\6\
m..............................  milli..................          10-\3\
c..............................  centi..................          10-\2\
k..............................  kilo...................           10\3\
M..............................  mega...................           10\6\
------------------------------------------------------------------------

Sec.  1036.810  Incorporation by reference.

    Certain material is incorporated by reference into this part with 
the approval of the Director of the Federal Register under 5 U.S.C. 
552(a) and 1 CFR part 51. To enforce any edition other than that 
specified in this section, EPA must publish a document in the Federal 
Register and the material must be available to the public. All approved 
incorporation by reference (IBR) material is available for inspection 
at EPA and at the National Archives and Records Administration (NARA). 
Contact EPA at: U.S. EPA, Air and Radiation Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004; 
www.epa.gov/dockets; (202) 202-1744. For information on inspecting this 
material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be 
obtained from the following sources:
    (a) ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West 
Conshohocken, PA 19428-2959; (877) 909-2786; www.astm.org.
    (1) ASTM D975-22, Standard Specification for Diesel Fuel, approved 
October 1, 2022 (``ASTM D975''); IBR approved for Sec.  1036.415(c).
    (2) ASTM D3588-98 (Reapproved 2017)e1, Standard Practice for 
Calculating Heat Value, Compressibility Factor, and Relative Density of 
Gaseous Fuels, approved April 1, 2017 (``ASTM D3588''); IBR approved 
for Sec.  1036.550(b).
    (3) ASTM D4809-18, Standard Test Method for Heat of Combustion of 
Liquid Hydrocarbon Fuels by Bomb Calorimeter (Precision Method), 
approved July 1, 2018 (``ASTM D4809''); IBR approved for Sec.  
1036.550(b).
    (4) ASTM D4814-21c, Standard Specification for Automotive Spark-
Ignition Engine Fuel, approved December 15, 2021 (``ASTM D4814''); IBR 
approved for Sec.  1036.415(c).
    (5) ASTM D7467-20a, Standard Specification for Diesel Fuel Oil, 
Biodiesel Blend (B6 to B20), approved June 1, 2020 (``ASTM D7467''); 
IBR approved for Sec.  1036.415(c).
    (b) National Institute of Standards and Technology (NIST), 100 
Bureau Drive, Stop 1070, Gaithersburg, MD 20899-1070; (301) 975-6478; 
www.nist.gov.
    (1) NIST Special Publication 811, 2008 Edition, Guide for the Use 
of the International System of Units (SI), Physics Laboratory, March 
2008; IBR approved for Sec.  1036.805.
    (2) [Reserved]
    (c) SAE International, 400 Commonwealth Dr., Warrendale, PA 15096-
0001; (877) 606-7323 (U.S. and Canada) or (724) 776-4970 (outside the 
U.S. and Canada); www.sae.org:
    (1) SAE J1979-2 APR2021, E/E Diagnostic Test Modes: OBDonUDS, 
Issued April 2021, (``SAE J1979-2''); IBR approved for Sec.  
1036.150(v).
    (2) [Reserved]
    (d) State of California, Office of Administrative Law, 300 Capitol 
Mall, Suite 1250, Sacramento, CA 95814-4339; 916-323-6815; 
[email protected]; www.oal.ca.gov/publications/ccr.
    (1) 2019 13 CCR 1968.2, Title 13. Motor Vehicles, Division 3. Air 
Resources Board, Chapter 1. Motor Vehicle Pollution Control Devices, 
Article 2. Approval of Motor Vehicle Pollution Control Devices (New 
Vehicles), Sec.  1968.2. Malfunction and Diagnostic System 
Requirements--2004 and Subsequent Model-Year Passenger Cars, Light-Duty 
Trucks, and Medium-

[[Page 4556]]

Duty Vehicles and Engines, operative October 3, 2019 ``13 CCR 1968.2''; 
into Sec. Sec.  1036.110(b); 1036.111(a).
    (2) 2019 13 CCR 1968.5, Title 13. Motor Vehicles, Division 3. Air 
Resources Board, Chapter 1. Motor Vehicle Pollution Control Devices, 
Article 2. Approval of Motor Vehicle Pollution Control Devices (New 
Vehicles), Sec.  1968.5. Enforcement of Malfunction and Diagnostic 
System Requirements for 2004 and Subsequent Model-Year Passenger Cars, 
Light-Duty Trucks, and Medium-Duty Vehicles and Engines, operative July 
25, 2016 ``13 CCR 1968.5''; into Sec.  1036.110(b).
    (3) 2019 13 CCR 1971.1, Title 13. Motor Vehicles, Division 3. Air 
Resources Board, Chapter 1. Motor Vehicle Pollution Control Devices, 
Article 2. Approval of Motor Vehicle Pollution Control Devices (New 
Vehicles), Sec.  1971.1. On-Board Diagnostic System Requirements--2010 
and Subsequent Model-Year Heavy-Duty Engines, operative October 3, 2019 
``13 CCR 1971.1''; into Sec. Sec.  1036.110(b); 1036.111(a); 
1036.150(v).
    (4) 13 CA ADC 1971.5: 2019 CA REG TEXT 504962 (NS), 13 CA ADC 
1971.5. Enforcement of Malfunction and Diagnostic System Requirements 
for 2010 and Subsequent Model-Year Heavy-Duty Engines, operative 
October 3, 2019 ``13 CCR 1971.5''; into Sec.  1036.110(b).

Sec.  1036.815  Confidential information.

    (a) The provisions of 40 CFR 1068.10 and 1068.11 apply for 
information you submit under this part.
    (b) Emission data or information that is publicly available cannot 
be treated as confidential business information as described in 40 CFR 
1068.11. Data that vehicle manufacturers need for demonstrating 
compliance with greenhouse gas emission standards, including fuel-
consumption data as described in Sec.  1036.535 and 40 CFR 1037.550, 
also qualify as emission data for purposes of confidentiality 
determinations.

Sec.  1036.820  Requesting a hearing.

    (a) You may request a hearing under certain circumstances, as 
described elsewhere in this part. To do this, you must file a written 
request, including a description of your objection and any supporting 
data, within 30 days after we make a decision.
    (b) For a hearing you request under the provisions of this part, we 
will approve your request if we find that your request raises a 
substantial factual issue.
    (c) If we agree to hold a hearing, we will use the procedures 
specified in 40 CFR part 1068, subpart G.

Sec.  1036.825  Reporting and recordkeeping requirements.

    (a) This part includes various requirements to submit and record 
data or other information. Unless we specify otherwise, store required 
records in any format and on any media and keep them readily available 
for eight years after you send an associated application for 
certification, or eight years after you generate the data if they do 
not support an application for certification. We may review these 
records at any time. You must promptly give us organized, written 
records in English if we ask for them. We may require you to submit 
written records in an electronic format.
    (b) The regulations in Sec.  1036.255 and 40 CFR 1068.25 and 
1068.101 describe your obligation to report truthful and complete 
information. This includes information not related to certification. 
Failing to properly report information and keep the records we specify 
violates 40 CFR 1068.101(a)(2), which may involve civil or criminal 
penalties.
    (c) Send all reports and requests for approval to the Designated 
Compliance Officer (see Sec.  1036.801).
    (d) Any written information we require you to send to or receive 
from another company is deemed to be a required record under this 
section. Such records are also deemed to be submissions to EPA. Keep 
these records for eight years unless the regulations specify a 
different period. We may require you to send us these records whether 
or not you are a certificate holder.
    (e) Under the Paperwork Reduction Act (44 U.S.C. 3501 et seq.), the 
Office of Management and Budget approves the reporting and 
recordkeeping specified in the applicable regulations. The following 
items illustrate the kind of reporting and recordkeeping we require for 
engines and vehicles regulated under this part:
    (1) We specify the following requirements related to engine 
certification in this part:
    (i) In Sec.  1036.135 we require engine manufacturers to keep 
certain records related to duplicate labels sent to vehicle 
manufacturers.
    (ii) In Sec.  1036.150 we include various reporting and 
recordkeeping requirements related to interim provisions.
    (iii) In subpart C of this part we identify a wide range of 
information required to certify engines.
    (iv) In Sec. Sec.  1036.430 and 1036.435 we identify reporting and 
recordkeeping requirements related to field testing in-use engines.
    (v) In subpart G of this part we identify several reporting and 
recordkeeping items for making demonstrations and getting approval 
related to various special compliance provisions.
    (vi) In Sec. Sec.  1036.725, 1036.730, and 1036.735 we specify 
certain records related to averaging, banking, and trading.
    (2) We specify the following requirements related to testing in 40 
CFR part 1065:
    (i) In 40 CFR 1065.2 we give an overview of principles for 
reporting information.
    (ii) In 40 CFR 1065.10 and 1065.12 we specify information needs for 
establishing various changes to published procedures.
    (iii) In 40 CFR 1065.25 we establish basic guidelines for storing 
information.
    (iv) In 40 CFR 1065.695 we identify the specific information and 
data items to record when measuring emissions.
    (3) We specify the following requirements related to the general 
compliance provisions in 40 CFR part 1068:
    (i) In 40 CFR 1068.5 we establish a process for evaluating good 
engineering judgment related to testing and certification.
    (ii) In 40 CFR 1068.25 we describe general provisions related to 
sending and keeping information
    (iii) In 40 CFR 1068.27 we require manufacturers to make engines 
available for our testing or inspection if we make such a request.
    (iv) In 40 CFR 1068.105 we require vehicle manufacturers to keep 
certain records related to duplicate labels from engine manufacturers.
    (v) In 40 CFR 1068.120 we specify recordkeeping related to 
rebuilding engines.
    (vi) In 40 CFR part 1068, subpart C, we identify several reporting 
and recordkeeping items for making demonstrations and getting approval 
related to various exemptions.
    (vii) In 40 CFR part 1068, subpart D, we identify several reporting 
and recordkeeping items for making demonstrations and getting approval 
related to importing engines.
    (viii) In 40 CFR 1068.450 and 1068.455 we specify certain records 
related to testing production-line engines in a selective enforcement 
audit.
    (ix) In 40 CFR 1068.501 we specify certain records related to 
investigating and reporting emission-related defects.
    (x) In 40 CFR 1068.525 and 1068.530 we specify certain records 
related to recalling nonconforming engines.

[[Page 4557]]

    (xi) In 40 CFR part 1068, subpart G, we specify certain records for 
requesting a hearing.

Appendix A of Part 1036--Summary of Previous Emission Standards

    The following standards, which EPA originally adopted under 40 
CFR part 85 or part 86, apply to compression-ignition engines 
produced before model year 2007 and to spark-ignition engines 
produced before model year 2008:
    (a) Smoke. Smoke standards applied for compression-ignition 
engines based on opacity measurement using the test procedures in 40 
CFR part 86, subpart I, as follows:
    (1) Engines were subject to the following smoke standards for 
model years 1970 through 1973:
    (i) 40 percent during the engine acceleration mode.
    (ii) 20 percent during the engine lugging mode.
    (2) The smoke standards in 40 CFR 86.007-11 started to apply in 
model year 1974.
    (b) Idle CO. A standard of 0.5 percent of exhaust gas flow at 
curb idle applied through model year 2016 to the following engines:
    (1) Spark-ignition engines with aftertreatment starting in model 
year 1987. This standard applied only for gasoline-fueled engines 
through model year 1997. Starting in model year 1998, the same 
standard applied for engines fueled by methanol, LPG, and natural 
gas. The idle CO standard no longer applied for engines certified to 
meet onboard diagnostic requirements starting in model year 2005.
    (2) Methanol-fueled compression-ignition engines starting in 
model year 1990. This standard also applied for natural gas and LPG 
engines starting in model year 1997. The idle CO standard no longer 
applied for engines certified to meet onboard diagnostic 
requirements starting in model year 2007.
    (c) Crankcase emissions. The requirement to design engines to 
prevent crankcase emissions applied starting with the following 
engines:
    (1) Spark-ignition engines starting in model year 1968. This 
standard applied only for gasoline-fueled engines through model year 
1989, and applied for spark-ignition engines using other fuels 
starting in model year 1990.
    (2) Naturally aspirated diesel-fueled engines starting in model 
year 1985.
    (3) Methanol-fueled compression-ignition engines starting in 
model year 1990.
    (4) Naturally aspirated gaseous-fueled engines starting in model 
year 1997, and all other gaseous-fueled engines starting in 1998.
    (d) Early steady-state standards. The following criteria 
standards applied to heavy-duty engines based on steady-state 
measurement procedures:

               Table 1 of Appendix A--Early Steady-State Emission Standards for Heavy-Duty Engines
----------------------------------------------------------------------------------------------------------------
                                                                               Pollutant
           Model year                    Fuel        -----------------------------------------------------------
                                                              HC               NOX + HC               CO
----------------------------------------------------------------------------------------------------------------
1970-1973.......................  gasoline..........  275 ppm...........  ..................  1.5 volume
                                                                                               percent.
1974-1978.......................  gasoline and        ..................  16 g/hp[middot]hr.  40 g/hp[middot]hr.
                                   diesel.
1979-1984 \a\...................  gasoline and        ..................  5 g/hp[middot]hr    25 g/hp[middot]hr.
                                   diesel.                                 for diesel; 5.0 g/
                                                                           hp[middot]hr for
                                                                           gasoline.
----------------------------------------------------------------------------------------------------------------
\a\ An optional NOX + HC standard of 10 g/hp[middot]hr applied in 1979 through 1984 in conjunction with a
  separate HC standard of 1.5 g/hp[middot]hr.

    (e) Transient emission standards for spark-ignition engines. The 
following criteria standards applied for spark-ignition engines 
based on transient measurement using the test procedures in 40 CFR 
part 86, subpart N. Starting in model year 1991, manufacturers could 
generate or use emission credits for NOX and 
NOX + NMHC standards. Table 2 to this appendix follows:

               Table 2 of Appendix A--Transient Emission Standards for Spark-Ignition Engines a b
----------------------------------------------------------------------------------------------------------------
                                                                    Pollutant (g/hp[middot]hr)
                   Model year                    ---------------------------------------------------------------
                                                        HC              CO              NOX         NOX + NMHC
----------------------------------------------------------------------------------------------------------------
1985-1987.......................................             1.1            14.4            10.6  ..............
1988-1990.......................................             1.1            14.4             6.0  ..............
1991-1997.......................................             1.1            14.4             5.0  ..............
1998-2004 \c\...................................             1.1            14.4             4.0  ..............
2005-2007.......................................  ..............            14.4  ..............         \d\ 1.0
----------------------------------------------------------------------------------------------------------------
\a\ Standards applied only for gasoline-fueled engines through model year 1989. Standards started to apply for
  methanol in model year 1990, and for LPG and natural gas in model year 1998.
\b\ Engines intended for installation only in heavy-duty vehicles above 14,000 pounds GVWR were subject to an HC
  standard of 1.9 g/hp[middot]hr for model years 1987 through 2004, and a CO standard of 37.1 g/hp[middot]hr for
  model years 1987 through 2007. In addition, for model years 1987 through 2007, up to 5 percent of a
  manufacturer's sales of engines intended for installation in heavy-duty vehicles at or below 14,000 pounds
  GVWR could be certified to the alternative HC and CO standards.
\c\ For natural gas engines in model years 1998 through 2004, the NOX standard was 5.0 g/hp[middot]hr; the HC
  standards were 1.7 g/hp[middot]hr for engines intended for installation only in vehicles above 14,000 pounds
  GVWR, and 0.9 g/hp[middot]hr for other engines.
\d\ Manufacturers could delay the 1.0 g/hp[middot]hr NOX + NMHC standard until model year 2008 by meeting an
  alternate NOX + NMHC standard of 1.5 g/hp[middot]hr applied for model years 2004 through 2007.

    (f) Transient emission standards for compression-ignition 
engines. The following criteria standards applied for compression-
ignition engines based on transient measurement using the test 
procedures in 40 CFR part 86, subpart N. Starting in model year 
1991, manufacturers could generate or use emission credits for 
NOX, NOX + NMHC, and PM standards. Table 3 to 
this appendix follows:

[[Page 4558]]

             Table 3 of Appendix A--Transient Emission Standards for Compression-Ignition Engines a
----------------------------------------------------------------------------------------------------------------
                                                             Pollutant (g/hp[middot]hr)
            Model year             -----------------------------------------------------------------------------
                                         HC           CO          NOX        NOX + NMHC              PM
----------------------------------------------------------------------------------------------------------------
1985-1987.........................          1.3         15.5         10.7  ..............  .....................
1988-1989.........................          1.3         15.5         10.7  ..............  0.60
1990..............................          1.3         15.5          6.0  ..............  0.60
1991-1992.........................          1.3         15.5          5.0  ..............  0.25
1993..............................          1.3         15.5          5.0  ..............  0.25 truck, 0.10 bus.
1994-1995.........................          1.3         15.5          5.0  ..............  0.10 truck, 0.07
                                                                                            urban bus.
1996-1997.........................          1.3         15.5          5.0  ..............  0.10 truck, 0.05
                                                                                            urban bus.\b\
1998-2003.........................          1.3         15.5          4.0  ..............  0.10 truck, 0.05
                                                                                            urban bus.\b\
2004-2006.........................  ...........         15.5  ...........         \c\ 2.4  0.10 truck, 0.05
                                                                                            urban bus.\b\
----------------------------------------------------------------------------------------------------------------
\a\ Standards applied only for diesel-fueled engines through model year 1989. Standards started to apply for
  methanol in model year 1990, and for LPG and natural gas in model year 1997. An alternate HC standard of 1.2 g/
  hp[middot]hr applied for natural gas engines for model years 1997 through 2003.
\b\ The in-use PM standard for urban bus engines in model years 1996 through 2006 was 0.07 g/hp[middot]hr.
\c\ An optional NOX + NMHC standard of 2.5 g/hp[middot]hr applied in 2004 through 2006 in conjunction with a
  separate NMHC standard of 0.5 g/hp[middot]hr.

Appendix B of Part 1036--Transient Duty Cycles

    (a) This appendix specifies transient test intervals and duty 
cycles for the engine and powertrain testing described in Sec. Sec.  
1036.512 and 1036.514, as follows:
    (1) The transient test intervals and duty cycle for testing 
engines involves a schedule of normalized engine speed and torque 
values.
    (2) The transient test intervals and duty cycles for powertrain 
testing involves a schedule of vehicle speeds and road grade. 
Determine road grade at each point based on the peak rated power of 
the powertrain system, Prated, determined in Sec.  
1036.520 and road grade coefficients using the following equation: 
Road grade = a [middot] P2rated + b [middot] 
Prated + c
    (3) The operating schedules in this appendix in some cases 
eliminate repetitive information by omitting 1 Hz records where 
there is no change in values. Perform testing by continuing to 
operate at the last specified values until the operating schedule 
shows a change in values. The official operating schedule for 
testing, cycle validation, and other purposes includes both the 
specified and omitted values.
    (b) The following transient test interval applies for spark-
ignition engines and powertrains when testing over the duty cycle 
specified in Sec.  1036.512:

Table 1 of Appendix B--Transient Test Interval for Spark-Ignition 
Engines and Powertrains Under Sec.  1036.512

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    (c) The following transient test interval applies for 
compression-ignition engines and powertrains when testing over the 
duty cycle specified in Sec.  1036.512:

Table 2 of Appendix B--Transient Test Interval for Compression-Ignition 
Engines and Powertrains Under Sec.  1036.512

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    (d) The following transient duty cycle applies for compression-
ignition engines and powertrains when testing under Sec.  1036.514:

Table 3 of Appendix B--Transient Duty Cycle for Compression-Ignition 
Engines and Powertrains Under Sec.  1036.514
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Appendix C of Part 1036--Default Engine Fuel Maps for Sec.  1036.540

    GEM contains the default steady-state fuel maps in this appendix 
for performing cycle-average engine fuel mapping as described in 
Sec.  1036.505(b)(2). Note that manufacturers have the option to 
replace these default values in GEM if they generate a steady-state 
fuel map as described in Sec.  1036.535(b).
    (a) Use the following default fuel map for compression-ignition 
engines that will be installed in Tractors and Vocational Heavy HDV:

Table 1 of Appendix C--Default Fuel Map for Compression-Ignition 
Engines Installed in Tractors and Vocational Heavy HDV

[[Page 4633]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.237

    (b) Use the following default fuel map for compression-ignition 
engines that will be installed in Vocational Light HDV and 
Vocational Medium HDV:

Table 2 of Appendix C--Default Fuel Map for Compression-Ignition 
Engines Installed in Vocational Light HDV and Vocational Medium HDV

[[Page 4634]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.238

    (c) Use the following default fuel map for all spark-ignition 
engines:

Table 3 of Appendix C--Default Fuel Map for Spark-Ignition Engines

[[Page 4635]]

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PART 1037--CONTROL OF EMISSIONS FROM NEW HEAVY-DUTY MOTOR VEHICLES

0
93. The authority citation for part 1037 continues to read as follows:

    Authority: 42 U.S.C. 7401--7671q.

Subpart A [Amended]

0
94. Amend Sec.  1037.1 by revising paragraph (a) to read as follows:

Sec.  1037.1  Applicability.

    (a) The regulations in this part 1037 apply for all new heavy-duty 
vehicles, except as provided in Sec. Sec.  1037.5 and 1037.104. This 
includes electric vehicles, fuel cell vehicles, and vehicles fueled by 
conventional and alternative fuels. This also includes certain trailers 
as described in Sec. Sec.  1037.5, 1037.150, and 1037.801.
* * * * *

0
95. Amend Sec.  1037.5 by revising paragraph (e) to read as follows:

Sec.  1037.5  Excluded vehicles.

* * * * *
    (e) Vehicles subject to the heavy-duty emission standards of 40 CFR 
part 86. See 40 CFR 86.1816 and 86.1819 for emission standards that 
apply for these vehicles. This exclusion generally applies for complete 
heavy-duty vehicles at or below 14,000 pounds GVWR.
* * * * *

0
96. Amend Sec.  1037.10 by revising paragraph (c) to read as follows:

Sec.  1037.10  How is this part organized?

* * * * *
    (c) Subpart C of this part describes how to apply for a certificate 
of conformity.
* * * * *

0
97. Revise Sec.  1037.101 to read as follows:

[[Page 4636]]

Sec.  1037.101  Overview of emission standards.

    This part specifies emission standards for certain vehicles and for 
certain pollutants. This part contains standards and other regulations 
applicable to the emission of the air pollutant defined as the 
aggregate group of six greenhouse gases: carbon dioxide, nitrous oxide, 
methane, hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride.
    (a) You must show that vehicles meet the following emission 
standards:
    (1) Exhaust emissions of criteria pollutants. Criteria pollutant 
standards for NOX, HC, PM, and CO apply as described in 
Sec.  1037.102. These pollutants are sometimes described collectively 
as ``criteria pollutants'' because they are either criteria pollutants 
under the Clean Air Act or precursors to the criteria pollutants ozone 
and PM.
    (2) Exhaust emissions of greenhouse gases. These pollutants are 
described collectively in this part as ``greenhouse gas pollutants'' 
because they are regulated primarily based on their impact on the 
climate. Emission standards apply as follows for greenhouse gas (GHG) 
emissions:
    (i) CO2, CH4, and N2O emission 
standards apply as described in Sec. Sec.  1037.105 through 1037.107.
    (ii) Hydrofluorocarbon standards apply as described in Sec.  
1037.115(e). These pollutants are also ``greenhouse gas pollutants'' 
but are treated separately from exhaust greenhouse gas pollutants 
listed in paragraph (b)(2)(i) of this section.
    (3) Fuel evaporative and refueling emissions. Requirements related 
to fuel evaporative and refueling emissions are described in Sec.  
1037.103.
    (b) The regulated heavy-duty vehicles are addressed in different 
groups as follows:
    (1) For criteria pollutants, vocational vehicles and tractors are 
regulated based on gross vehicle weight rating (GVWR), whether they are 
considered ``spark-ignition'' or ``compression-ignition,'' and whether 
they are first sold as complete or incomplete vehicles.
    (2) For greenhouse gas pollutants, vehicles are regulated in the 
following groups:
    (i) Tractors above 26,000 pounds GVWR.
    (ii) Trailers.
    (iii) Vocational vehicles.
    (3) The greenhouse gas emission standards apply differently 
depending on the vehicle service class as described in Sec.  1037.140. 
In addition, standards apply differently for vehicles with spark-
ignition and compression-ignition engines. References in this part 1037 
to ``spark-ignition'' or ``compression-ignition'' generally relate to 
the application of standards under 40 CFR 1036.140. For example, a 
vehicle with an engine certified to spark-ignition standards under 40 
CFR part 1036 is generally subject to requirements under this part 1037 
that apply for spark-ignition vehicles. However, note that emission 
standards for Heavy HDE are considered to be compression-ignition 
standards for purposes of applying vehicle emission standards under 
this part. Also, for spark-ignition engines voluntarily certified as 
compression-ignition engines under 40 CFR part 1036, you must choose at 
certification whether your vehicles are subject to spark-ignition 
standards or compression-ignition standards.
    (4) For evaporative and refueling emissions, vehicles are regulated 
based on the type of fuel they use. Vehicles fueled with volatile 
liquid fuels or gaseous fuels are subject to evaporative and refueling 
emission standards.

0
98. Revise Sec.  1037.102 to read as follows:

Sec.  1037.102  Exhaust emission standards for NOX, HC, PM, and CO.

    (a) Engines installed in heavy-duty vehicles are subject to 
criteria pollutant standards for NOX, HC, PM, and CO under 
40 CFR part 86 through model year 2026 and 40 CFR part 1036 for model 
years 2027 and later.
    (b) Heavy-duty vehicles with no installed propulsion engine, such 
as electric vehicles, are subject to criteria pollutant standards under 
this part. The emission standards that apply are the same as the 
standards that apply for compression-ignition engines under 40 CFR 
86.007-11 and 1036.104 for a given model year.
    (1) You may state in the application for certification that 
vehicles with no installed propulsion engine comply with all the 
requirements of this part related to criteria emission standards 
instead of submitting test data. Tailpipe emissions of criteria 
pollutants from vehicles with no installed propulsion engine are deemed 
to be zero.
    (2) Vehicles with no installed propulsion engines may not generate 
NOX credits.

0
99. Amend Sec.  1037.103 by:
0
a. Revising paragraph (b)(1);
0
b. Removing paragraph (b)(6); and
0
c. Revising paragraphs (f) and (g)(1) and (2).
    The revisions read as follows:

Sec.  1037.103  Evaporative and refueling emission standards.

* * * * *
    (b) * * *
    (1) The refueling standards in 40 CFR 86.1813-17(b) and the related 
provisions in 40 CFR part 86, subpart S, apply to complete vehicles 
starting in model year 2022. Those standards and related provisions 
apply for incomplete vehicles starting in model year 2027, or as 
described in the alternate phase-in schedule described in 40 CFR 
86.1813-17(b). If you do not certify all your incomplete heavy-duty 
vehicles above 14,000 pounds GVWR to the refueling standards in model 
year 2027, you must use the alternate phase-in schedule described in 40 
CFR 86.1813-17(b).
* * * * *
    (f) Useful life. The evaporative and refueling emission standards 
of this section apply for the full useful life, expressed in service 
miles or calendar years, whichever comes first. The useful life values 
for the standards of this section are the same as the values described 
for evaporative emission standards in 40 CFR 86.1805.
    (g) * * *
    (1) Auxiliary engines and associated fuel-system components must be 
installed when testing fully assembled vehicles. If the auxiliary 
engine draws fuel from a separate fuel tank, you must fill the extra 
fuel tank before the start of diurnal testing as described for the 
vehicle's main fuel tank. Use good engineering judgment to ensure that 
any nonmetal portions of the fuel system related to the auxiliary 
engine have reached stabilized levels of permeation emissions. The 
auxiliary engine must not operate during the running loss test or any 
other portion of testing under this section.
    (2) For testing with partially assembled vehicles, you may omit 
installation of auxiliary engines and associated fuel-system components 
as long as those components installed in the final configuration are 
certified to meet the applicable emission standards for Small SI 
equipment described in 40 CFR 1054.112 or for Large SI engines in 40 
CFR 1048.105. For any fuel-system components that you do not install, 
your installation instructions must describe this certification 
requirement.

0
100. Amend Sec.  1037.105 by:
0
a. Revising paragraph (g)(2);
0
b. Amending paragraph (h)(1) by revising footnote a in Table 5; and
0
c. Revising paragraphs (h)(5) through (7).
    The revisions read as follows:

Sec.  1037.105  CO2 emission standards for vocational vehicles.

* * * * *
    (g) * * *

[[Page 4637]]

    (2) Class 8 hybrid vehicles with Light HDE or Medium HDE may be 
certified to compression-ignition standards for the Heavy HDV service 
class. You may generate and use credits as allowed for the Heavy HDV 
service class.
* * * * *
    (h) * * *
    (1) * * *

                          Table 5 of Sec.   1037.105--Phase 2 Custom Chassis Standards
                                                  [g/ton-mile]
----------------------------------------------------------------------------------------------------------------
                Vehicle type a                  Assigned vehicle service class     MY 2021-2026      MY 2027+
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------
\a\ Vehicle types are generally defined in Sec.   1037.801. ``Other bus'' includes any bus that is not a school
  bus or a coach bus. A ``mixed-use vehicle'' is one that meets at least one of the criteria specified in Sec.
  1037.631(a)(1) or (2).

* * * * *
    (5) Emergency vehicles are deemed to comply with the standards of 
this paragraph (h) if they use tires with TRRL at or below 8.4 N/kN 
(8.7 N/kN for model years 2021 through 2026).
    (6) Concrete mixers and mixed-use vehicles are deemed to comply 
with the standards of this paragraph (h) if they use tires with TRRL at 
or below 7.1 N/kN (7.6 N/kN for model years 2021 through 2026).
    (7) Motor homes are deemed to comply with the standards of this 
paragraph (h) if they have tires with TRRL at or below 6.0 N/kN (6.7 N/
kN for model years 2021 through 2026) and automatic tire inflation 
systems or tire pressure monitoring systems with wheels on all axles.
* * * * *

0
101. Amend Sec.  1037.106 by revising paragraph (f)(1) to read as 
follows:

Sec.  1037.106  Exhaust emission standards for tractors above 26,000 
pounds GVWR.

* * * * *
    (f) * * *
    (1) You may optionally certify 4x2 tractors with Heavy HDE to the 
standards and useful life for Class 8 tractors, with no restriction on 
generating or using emission credits within the Class 8 averaging set.
* * * * *

0
102. Amend Sec.  1037.115 by revising paragraphs (a) and (e)(3) to read 
as follows:

Sec.  1037.115  Other requirements.

* * * * *
    (a) Adjustable parameters. Vehicles that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range. We may require that you set adjustable 
parameters to any specification within the practically adjustable range 
during any testing. See 40 CFR 1068.50 for general provisions related 
to adjustable parameters. You must ensure safe vehicle operation 
throughout the practically adjustable range of each adjustable 
parameter, including consideration of production tolerances. Note that 
adjustable roof fairings and trailer rear fairings are deemed not to be 
adjustable parameters.
* * * * *
    (e) * * *
    (3) If air conditioning systems are designed such that a compliance 
demonstration under 40 CFR 86.1867-12(a) is impossible or impractical, 
you may ask to use alternative means to demonstrate that your air 
conditioning system achieves an equivalent level of control.

0
103. Amend Sec.  1037.120 by revising paragraph (c) to read as follows:

Sec.  1037.120  Emission-related warranty requirements.

* * * * *
    (c) Components covered. The emission-related warranty covers tires, 
automatic tire inflation systems, tire pressure monitoring systems, 
vehicle speed limiters, idle-reduction systems, hybrid system 
components, and devices added to the vehicle to improve aerodynamic 
performance (not including standard components such as hoods or mirrors 
even if they have been optimized for aerodynamics) to the extent such 
emission-related components are included in your application for 
certification. The emission-related warranty also covers other added 
emission-related components to the extent they are included in your 
application for certification. The emission-related warranty covers all 
components whose failure would increase a vehicle's emissions of air 
conditioning refrigerants (for vehicles subject to air conditioning 
leakage standards), and it covers all components whose failure would 
increase a vehicle's evaporative and refueling emissions (for vehicles 
subject to evaporative and refueling emission standards). The emission-
related warranty covers components that are part of your certified 
configuration even if another company produces the component. Your 
emission-related warranty does not need to cover components whose 
failure would not increase a vehicle's emissions of any regulated 
pollutant.
* * * * *

0
104. Amend Sec.  1037.125 by revising paragraphs (a) and (d) to read as 
follows:

Sec.  1037.125  Maintenance instructions and allowable maintenance.

* * * * *
    (a) Critical emission-related maintenance. Critical emission-
related maintenance includes any adjustment, cleaning, repair, or 
replacement of critical emission-related components. Critical emission-
related maintenance may also include additional emission-related 
maintenance that you determine is critical if we approve it in advance. 
You may schedule critical emission-related maintenance on these 
components if you demonstrate that the maintenance is reasonably likely 
to be done at the recommended intervals on in-use vehicles. We will 
accept scheduled maintenance as reasonably likely to occur if you 
satisfy any of the following conditions:
* * * * *
    (d) Noncritical emission-related maintenance. Subject to the 
provisions of this paragraph (d), you may schedule any amount of 
emission-related inspection or maintenance that is not covered by 
paragraph (a) of this section (that is, maintenance that is neither 
explicitly identified as critical emission-related maintenance, nor 
that we approve as critical emission-related maintenance). Noncritical 
emission-related maintenance generally includes maintenance on the 
components we specify in 40 CFR part 1068, appendix A, that is not 
covered in paragraph (a) of this section. You must state in the owners 
manual that these steps are not necessary to keep the emission-related 
warranty valid. If operators fail to do this maintenance, this does not 
allow you to disqualify those vehicles from in-use testing or deny a 
warranty claim. Do

[[Page 4638]]

not take these inspection or maintenance steps during service 
accumulation on your emission-data vehicles.
* * * * *

0
105. Amend Sec.  1037.130 by revising paragraph (b)(3) to read as 
follows:

Sec.  1037.130  Assembly instructions for secondary vehicle 
manufacturers.

* * * * *
    (b) * * *
    (3) Describe the necessary steps for installing emission-related 
diagnostic systems.
* * * * *

0
106. Amend Sec.  1037.135 by revising paragraph (c)(6) to read as 
follows:

Sec.  1037.135  Labeling.

* * * * *
    (c) * * *
    (6) Identify the emission control system. Use terms and 
abbreviations as described in appendix C to this part or other 
applicable conventions. Phase 2 tractors and Phase 2 vocational 
vehicles may omit this information.
* * * * *

0
107. Amend Sec.  1037.140 by revising paragraph (g) to read as follows:

Sec.  1037.140  Classifying vehicles and determining vehicle 
parameters.

* * * * *
    (g) The standards and other provisions of this part apply to 
specific vehicle service classes for tractors and vocational vehicles 
as follows:
    (1) Phase 1 and Phase 2 tractors are divided based on GVWR into 
Class 7 tractors and Class 8 tractors. Where provisions of this part 
apply to both tractors and vocational vehicles, Class 7 tractors are 
considered ``Medium HDV'' and Class 8 tractors are considered ``Heavy 
HDV''. This paragraph (g)(1) applies for hybrid and non-hybrid 
vehicles.
    (2) Phase 1 vocational vehicles are divided based on GVWR. ``Light 
HDV'' includes Class 2b through Class 5 vehicles; ``Medium HDV'' 
includes Class 6 and Class 7 vehicles; and ``Heavy HDV'' includes Class 
8 vehicles.
    (3) Phase 2 vocational vehicles propelled by engines subject to the 
spark-ignition standards of 40 CFR part 1036 are divided as follows:
    (i) Class 2b through Class 5 vehicles are considered ``Light HDV''.
    (ii) Class 6 through Class 8 vehicles are considered ``Medium 
HDV''.
    (4) Phase 2 vocational vehicles propelled by engines subject to the 
compression-ignition standards in 40 CFR part 1036 are divided as 
follows:
    (i) Class 2b through Class 5 vehicles are considered ``Light HDV''.
    (ii) Class 6 through 8 vehicles are considered ``Heavy HDV'' if the 
installed engine's primary intended service class is Heavy HDE (see 40 
CFR 1036.140), except that Class 8 hybrid vehicles are considered 
``Heavy HDV'' regardless of the engine's primary intended service 
class.
    (iii) All other Class 6 through Class 8 vehicles are considered 
``Medium HDV''.
    (5) Heavy-duty vehicles with no installed propulsion engine, such 
as electric vehicles, are divided as follows:
    (i) Class 2b through Class 5 vehicles are considered ``Light HDV''.
    (ii) Class 6 and 7 vehicles are considered ``Medium HDV''.
    (iii) Class 8 vehicles are considered ``Heavy HDV''.
    (6) In certain circumstances, you may certify vehicles to standards 
that apply for a different vehicle service class. For example, see 
Sec. Sec.  1037.105(g) and 1037.106(f). If you optionally certify 
vehicles to different standards, those vehicles are subject to all the 
regulatory requirements as if the standards were mandatory.
* * * * *

0
108. Amend Sec.  1037.150 by revising paragraphs (f) and (y)(1) to read 
as follows:

Sec.  1037.150  Interim provisions.

* * * * *
    (f) Electric and hydrogen fuel cell vehicles. Tailpipe emissions of 
regulated GHG pollutants from electric vehicles and hydrogen fuel cell 
vehicles are deemed to be zero. No CO2-related emission 
testing is required for electric vehicles or hydrogen fuel cell 
vehicles. Use good engineering judgment to apply other requirements of 
this part to electric vehicles.
* * * * *
    (y) * * *
    (1) For vocational Light HDV and vocational Medium HDV, emission 
credits you generate in model years 2018 through 2021 may be used 
through model year 2027, instead of being limited to a five-year credit 
life as specified in Sec.  1037.740(c). For Class 8 vocational vehicles 
with Medium HDE, we will approve your request to generate these credits 
in and use these credits for the Medium HDV averaging set if you show 
that these vehicles would qualify as Medium HDV under the Phase 2 
program as described in Sec.  1037.140(g)(4).
* * * * *

0
109. Amend Sec.  1037.201 by revising paragraph (h) to read as follows:

Sec.  1037.201  General requirements for obtaining a certificate of 
conformity.

* * * * *
    (h) The certification and testing provisions of 40 CFR part 86, 
subpart S, apply instead of the provisions of this subpart relative to 
the evaporative and refueling emission standards specified in Sec.  
1037.103, except that Sec.  1037.243 describes how to demonstrate 
compliance with evaporative and refueling emission standards. For 
vehicles that do not use an evaporative canister for controlling 
diurnal emissions, you may certify with respect to exhaust emissions 
and use the provisions of Sec.  1037.622 to let a different company 
certify with respect to evaporative emissions.
* * * * *

0
110. Amend Sec.  1037.205 by revising paragraphs (e) and (p), and 
adding paragraph (q) to read as follows:

Sec.  1037.205  What must I include in my application?

* * * * *
    (e) Describe any test equipment and procedures that you used, 
including any special or alternate test procedures you used (see Sec.  
1037.501). Include information describing the procedures you used to 
determine CdA values as specified in Sec. Sec.  1037.525 
through 1037.527. Describe which type of data you are using for engine 
fuel maps (see 40 CFR 1036.505). If your trailer certification relies 
on approved data from device manufacturers, identify the device and 
device manufacturer.
* * * * *
    (p) Where applicable, describe all adjustable operating parameters 
(see Sec.  1037.115), including production tolerances. For any 
operating parameters that do not qualify as adjustable parameters, 
include a description supporting your conclusion (see 40 CFR 
1068.50(c)). Include the following in your description of each 
adjustable parameter:
    (1) The nominal or recommended setting.
    (2) The intended practically adjustable range.
    (3) The limits or stops used to establish adjustable ranges.
    (4) Information showing why the limits, stops, or other means of 
inhibiting adjustment are effective in preventing adjustment of 
parameters on in-use engines to settings outside your intended 
practically adjustable ranges.
    (q) Include the following information for electric vehicles and 
fuel cell vehicles to show they meet the standards of this part:

[[Page 4639]]

    (1) You may attest that vehicles comply with the standards of Sec.  
1037.102 instead of submitting test data.
    (2) For vehicles generating credits under Sec.  1037.616, you may 
attest that the vehicle meets the durability requirements described in 
Sec.  1037.102(b)(3) based on an engineering analysis of measured 
values and other information, consistent with good engineering 
judgment, instead of testing at the end of the useful life. Send us 
your test results for work produced over the FTP and initial useable 
battery energy or initial fuel cell voltage. Also send us your 
engineering analysis describing how you meet the durability 
requirements if we ask for it.
* * * * *

0
111. Amend Sec.  1037.225 by revising the introductory text and 
paragraph (g) to read as follows:

Sec.  1037.225  Amending applications for certification.

    Before we issue you a certificate of conformity, you may amend your 
application to include new or modified vehicle configurations, subject 
to the provisions of this section. After we have issued your 
certificate of conformity, you may send us an amended application any 
time before the end of the model year requesting that we include new or 
modified vehicle configurations within the scope of the certificate, 
subject to the provisions of this section. You must amend your 
application if any changes occur with respect to any information that 
is included or should be included in your application.
* * * * *
    (g) You may produce vehicles or modify in-use vehicles as described 
in your amended application for certification and consider those 
vehicles to be in a certified configuration. Modifying a new or in-use 
vehicle to be in a certified configuration does not violate the 
tampering prohibition of 40 CFR 1068.101(b)(1), as long as this does 
not involve changing to a certified configuration with a higher family 
emission limit. See Sec.  1037.621(g) for special provisions that apply 
for changing to a different certified configuration in certain 
circumstances.

0
112. Amend Sec.  1037.230 by revising paragraph (c) to read as follows:

Sec.  1037.230  Vehicle families, sub-families, and configurations.

* * * * *
    (c) Group vehicles into configurations consistent with the 
definition of ``vehicle configuration'' in Sec.  1037.801. Note that 
vehicles with hardware or software differences that are related to 
measured or modeled emissions are considered to be different vehicle 
configurations even if they have the same modeling inputs and FEL. Note 
also, that you are not required to separately identify all 
configurations for certification. Note that you are not required to 
identify all possible configurations for certification; also, you are 
required to include in your final ABT report only those configurations 
you produced.
* * * * *

0
113. Amend Sec.  1037.231 by revising paragraph (b)(1) to read as 
follows:

Sec.  1037.231  Powertrain families.

* * * * *
    (b) * * *
    (1) Engine family as specified in 40 CFR 1036.230.
* * * * *

0
114. Amend Sec.  1037.243 by revising the section heading and 
paragraphs (a) and (b) to read as follows:

Sec.  1037.243  Demonstrating compliance with evaporative and refueling 
emission standards.

    (a) For purposes of certification, your vehicle family is 
considered in compliance with the evaporative and refueling emission 
standards in subpart B of this part if you prepare an engineering 
analysis showing that your vehicles in the family will comply with 
applicable standards throughout the useful life, and there are no test 
results from an emission-data vehicle representing the family that 
exceed an emission standard.
    (b) Your evaporative refueling emission family is deemed not to 
comply if your engineering analysis is not adequate to show that all 
the vehicles in the family will comply with applicable emission 
standards throughout the useful life, or if a test result from an 
emission-data vehicle representing the family exceeds an emission 
standard.
* * * * *

0
115. Amend Sec.  1037.250 by revising paragraph (a) to read as follows:

Sec.  1037.250  Reporting and recordkeeping.

    (a) By September 30 following the end of the model year, send the 
Designated Compliance Officer a report including the total U.S.-
directed production volume of vehicles you produced in each vehicle 
family during the model year (based on information available at the 
time of the report). Report by vehicle identification number and 
vehicle configuration and identify the subfamily identifier. Report 
uncertified vehicles sold to secondary vehicle manufacturers. We may 
waive the reporting requirements of this paragraph (a) for small 
manufacturers.
* * * * *

0
116. Amend Sec.  1037.320 by revising paragraph (b) to read as follows 
and removing Table 1 to Sec.  1037.320:

Sec.  1037.320  Audit procedures for axles and transmissions.

* * * * *
    (b) Run GEM with the define vehicles to determine whether the 
transmission or axle family passes the audit.
    (1) For transmission audits, run GEM for each applicable vehicle 
configuration and GEM regulatory subcategory identified in 40 CFR 
1036.540 and for each vehicle class as defined in Sec.  1037.140(g) 
using the applicable default engine map in appendix C of 40 CFR part 
1036, the cycle-average fuel map in Table 1 of this section, the torque 
curve in Table 2 of this section for both the engine full-load torque 
curve and parent engine full-load torque curve, the motoring torque 
curve in Table 3 of this section, the idle fuel map in Table 4 of this 
section. For transmission testing, use the test transmission's gear 
ratios in place of the gear ratios defined in 40 CFR 1036.540. Table 1 
through Table 4 follow:

                                                Table 1 to Paragraph (b)(1) of Sec.   1037.320--Transient Cycle-Average Fuel Map by Vehicle Class
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
             Light HDV and medium HDV--spark-ignition                       Light HDV and medium HDV--compression-ignition                                    Heavy HDV
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Engine cycle                             Idle                      Engine cycle                            Idle                     Engine cycle                         Idle
      work         N/V (r/      Fuel    speed (r/    Idle torque         work         N/V (r/   Fuel mass  speed (r/  Idle torque         work        N/V (r/    Fuel    speed (r/  Idle torque
 (kW[middot]hr)      min)     mass (g)     min)     (N[middot]m)    (kW[middot]hr)      min)       (g)       min)     (N[middot]m)   (kW[middot]hr)    min)    mass (g)    min)     (N[middot]m)
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
     3.5404         2.8739    1109.31      600.5       37.997            3.3057        2.3317     919.01      750.3      36.347         11.4255        2.3972   2579.58     600.7      89.658
     3.6574         3.0198    1153.35      600.4       37.951            3.3822        2.5075     982.53      750.2      36.461         11.6112        2.2432   2591.08     601.2      90.428
     3.8119         3.0370    1188.66      600.2       37.956            3.4917        2.5320     998.64      750.2      36.608         12.5052        2.1620   2763.28     602.4      92.014
     4.0121         3.1983    1250.76      600.1       38.153            3.6087        2.6181    1036.34      750.2      36.734         17.7747        2.5195   3835.77     602.2      91.780

[[Page 4640]]

 
     5.5567         3.1325    1585.32      604.6       56.535            5.2397        2.5050    1354.33      753.0      51.992         18.4901        2.4155   3994.29     603.5      93.724
     5.6814         3.2956    1639.08      604.0       56.549            5.3153        2.7289    1417.20      751.9      51.488         20.1904        2.3800   4374.06     605.1      96.340
     5.8720         3.3255    1686.14      602.5       56.234            5.4112        2.6689    1416.75      751.3      51.280     ...............  ........  ........  ........  .............
     6.1774         3.4848    1773.39      601.7       56.038            5.5590        2.7231    1450.67      751.0      51.254     ...............  ........  ........  ........  .............
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

                                Table 2 to Paragraph (b)(1) of Sec.   1037.320--Full-Load Torque Curves by Vehicle Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
      Light HDV and medium HDV--spark-ignition         Light HDV and medium HDV--compression-ignition                       Heavy HDV
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                 Engine torque                                      Engine torque                                     Engine torque
   Engine speed (r/min)          (N[middot]m)          Engine speed (r/min)         (N[middot]m)          Engine speed (r/min)         (N[middot]m)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                  600                       433                       750                      470                       600                     1200
                  700                       436                       907                      579                       750                     1320
                  800                       445                      1055                      721                       850                     1490
                  900                       473                      1208                      850                       950                     1700
                 1000                       492                      1358                      876                      1050                     1950
                 1100                       515                      1507                      866                      1100                     2090
                 1200                       526                      1660                      870                      1200                     2100
                 1300                       541                      1809                      868                      1250                     2100
                 1400                       542                      1954                      869                      1300                     2093
                 1500                       542                      2105                      878                      1400                     2092
                 1600                       542                      2258                      850                      1500                     2085
                 1700                       547                      2405                      800                      1520                     2075
                 1800                       550                      2556                      734                      1600                     2010
                 1900                       551                      2600                        0                      1700                     1910
                 2000                       554      .......................  ........................                  1800                     1801
                 2100                       553      .......................  ........................                  1900                     1640
                 2200                       558      .......................  ........................                  2000                     1350
                 2300                       558      .......................  ........................                  2100                      910
                 2400                       566      .......................  ........................                  2250                        0
                 2500                       571
                 2600                       572
                 2700                       581
                 2800                       586
                 2900                       587
                 3000                       590
                 3100                       591
                 3200                       589
                 3300                       585
                 3400                       584
                 3500                       582
                 3600                       573
                 3700                       562
                 3800                       555
                 3900                       544
                 4000                       534
                 4100                       517
                 4200                       473
                 4291                       442
                 4500                       150
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                 Table 3 to Paragraph (b)(1) of Sec.   1037.320--Motoring Torque Curves by Vehicle Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
      Light HDV and medium HDV--spark-ignition         Light HDV and medium HDV--compression-ignition                       Heavy HDV
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                 Engine torque                                      Engine torque                                     Engine torque
   Engine speed (r/min)          (N[middot]m)          Engine speed (r/min)         (N[middot]m)          Engine speed (r/min)         (N[middot]m)
--------------------------------------------------------------------------------------------------------------------------------------------------------
                  700                       -41                       750                     -129                       600                      -98
                  800                       -42                       907                     -129                       750                     -121
                  900                       -43                      1055                     -130                       850                     -138
                 1000                       -45                      1208                     -132                       950                     -155
                 1100                       -48                      1358                     -135                      1050                     -174
                 1200                       -49                      1507                     -138                      1100                     -184
                 1300                       -50                      1660                     -143                      1200                     -204

[[Page 4641]]

 
                 1411                       -51                      1809                     -148                      1250                     -214
                 1511                       -52                      1954                     -155                      1300                     -225
                 1611                       -53                      2105                     -162                      1400                     -247
                 1711                       -56                      2258                     -170                      1500                     -270
                 1811                       -56                      2405                     -179                      1520                     -275
                 1911                       -57                      2556                     -189                      1600                     -294
                 2011                       -57      .......................  ........................                  1700                     -319
                 2111                       -58      .......................  ........................                  1800                     -345
                 2211                       -60      .......................  ........................                  1900                     -372
                 2311                       -65      .......................  ........................                  2000                     -400
                 2411                       -81      .......................  ........................                  2100                     -429
                 2511                       -85
                 2611                       -87
                 2711                       -88
                 2811                       -89
                 2911                       -91
                 3011                       -91
                 3111                       -96
                 3211                       -96
                 3311                       -97
                 3411                       -98
                 3511                       -99
                 3611                      -104
                 3711                      -105
                 3811                      -108
                 3911                      -108
                 4011                      -111
                 4111                      -111
                 4211                      -115
                 4291                      -112
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                 Table 4 to Paragraph (b)(1) of Sec.   1037.320--Engine Idle Fuel Maps by Vehicle Class
--------------------------------------------------------------------------------------------------------------------------------------------------------
      Light HDV and medium HDV-- spark-ignition         Light HDV and medium HDV-- compression-ignition                      Heavy HDV
--------------------------------------------------------------------------------------------------------------------------------------------------------
 Engine speed (r/   Engine torque   Fuel mass rate (g/ Engine speed (r/  Engine torque   Fuel mass rate    Engine speed    Engine torque  Fuel mass rate
       min)          (N[middot]m)           s)               min)        (N[middot]m)         (g/s)           (r/min)      (N[middot]m)        (g/s)
--------------------------------------------------------------------------------------------------------------------------------------------------------
            600                 0            0.4010               750               0           0.2595              600               0          0.3501
            700                 0            0.4725               850               0           0.2626              700               0          0.4745
            600               100            0.6637               750             100           0.6931              600             100          0.6547
            700               100            0.7524               850             100           0.7306              700             100          0.8304
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (2) Follow the procedure in paragraph (b)(1) of this section for 
axle audits, but cover the range of tire sizes by using good 
engineering judgment to select three representative tire sizes for each 
axle ratio for each vehicle configuration instead of using the tire 
size determined in 40 CFR 1036.540.
    (3) The GEM ``Default FEL CO2 Emissions'' result for 
each vehicle configuration counts as a separate test for determining 
whether the family passes the audit. For vocational vehicles, use the 
GEM ``Default FEL CO2 Emissions'' result for the Regional 
subcategory.
* * * * *

0
117. Amend Sec.  1037.510 by revising paragraphs (a)(1)(i), (2), and 
(3) and (d) to read as follows:

Sec.  1037.510  Duty-cycle exhaust testing.

* * * * *
    (a) * * *
    (1) * * *
    (i) Transient cycle. The transient cycle is specified in appendix A 
of this part. Warm up the vehicle. Start the duty cycle within 30 
seconds after concluding the preconditioning procedure. Start sampling 
emissions at the start of the duty cycle.
* * * * *
    (2) Perform cycle-average engine fuel mapping as described in 40 
CFR 1036.540. For powertrain testing under Sec.  1037.550 or Sec.  
1037.555, perform testing as described in this paragraph (a)(2) to 
generate GEM inputs for each simulated vehicle configuration, and test 
runs representing different idle conditions. Perform testing as 
follows:
    (i) Transient cycle. The transient cycle is specified in appendix A 
of this part.
    (ii) Highway cruise cycles. The grade portion of the route 
corresponding to the 55 mi/hr and 65 mi/hr highway cruise cycles is 
specified in appendix D of this part. Maintain vehicle speed between -
1.0 mi/hr and 3.0 mi/hr of the speed setpoint; this speed tolerance 
applies instead of the approach specified in 40 CFR 1066.425(b)(1) and 
(2).
    (iii) Drive idle. Perform testing at a loaded idle condition for 
Phase 2 vocational vehicles. For engines with an adjustable warm idle 
speed setpoint, test at the minimum warm idle speed and the maximum 
warm idle speed;

[[Page 4642]]

otherwise simply test at the engine's warm idle speed. Warm up the 
powertrain as described in 40 CFR 1036.520(c)(1). Within 60 seconds 
after concluding the warm-up, linearly ramp the powertrain down to zero 
vehicle speed over 20 seconds. Apply the brake and keep the 
transmission in drive (or clutch depressed for manual transmission). 
Stabilize the powertrain for (60 1) seconds and then sample 
emissions for (30 1) seconds.
    (iv) Parked idle. Perform testing at a no-load idle condition for 
Phase 2 vocational vehicles. For engines with an adjustable warm idle 
speed setpoint, test at the minimum warm idle speed and the maximum 
warm idle speed; otherwise simply test at the engine's warm idle speed. 
Warm up the powertrain as described in 40 CFR 1036.520(c)(1). Within 60 
seconds after concluding the warm-up, linearly ramp the powertrain down 
to zero vehicle speed in 20 seconds. Put the transmission in park (or 
neutral for manual transmissions and apply the parking brake if 
applicable). Stabilize the powertrain for (180 1) seconds 
and then sample emissions for (600 1) seconds.
    (3) Where applicable, perform testing on a chassis dynamometer as 
follows:
    (i) Transient cycle. The transient cycle is specified in appendix A 
of this part. Warm up the vehicle by operating over one transient 
cycle. Within 60 seconds after concluding the warm up cycle, start 
emission sampling and operate the vehicle over the duty cycle.
    (ii) Highway cruise cycle. The grade portion of the route 
corresponding to the 55 mi/hr and 65 mi/hr highway cruise cycles is 
specified in appendix D of this part. Warm up the vehicle by operating 
it at the appropriate speed setpoint over the duty cycle. Within 60 
seconds after concluding the preconditioning cycle, start emission 
sampling and operate the vehicle over the duty cycle, maintaining 
vehicle speed within 1.0 mi/hr of the speed setpoint; this 
speed tolerance applies instead of the approach specified in 40 CFR 
1066.425(b)(1) and (2).
* * * * *
    (d) For highway cruise and transient testing, compare actual 
second-by-second vehicle speed with the speed specified in the test 
cycle and ensure any differences are consistent with the criteria as 
specified in Sec.  1037.550(g)(1). If the speeds do not conform to 
these criteria, the test is not valid and must be repeated.
* * * * *

0
118. Amend Sec.  1037.520 by revising paragraphs (c)(2) and (3), (f), 
and (h)(1) to read as follows:

Sec.  1037.520  Modeling CO2 emissions to show compliance 
for vocational vehicles and tractors.

* * * * *
    (c) * * *
    (2) Measure tire rolling resistance in newton per kilonewton as 
specified in ISO 28580 (incorporated by reference in Sec.  1037.810), 
except as specified in this paragraph (c). Use good engineering 
judgment to ensure that your test results are not biased low. You may 
ask us to identify a reference test laboratory to which you may 
correlate your test results. Prior to beginning the test procedure in 
Section 7 of ISO 28580 for a new bias-ply tire, perform a break-in 
procedure by running the tire at the specified test speed, load, and 
pressure for (60 2) minutes.
    (3) For each tire design tested, measure rolling resistance of at 
least three different tires of that specific design and size. Perform 
the test at least once for each tire. Calculate the arithmetic mean of 
these results to the nearest 0.1 N/kN and use this value or any higher 
value as your GEM input for TRRL. You must test at least one tire size 
for each tire model, and may use engineering analysis to determine the 
rolling resistance of other tire sizes of that model. Note that for 
tire sizes that you do not test, we will treat your analytically 
derived rolling resistances the same as test results, and we may 
perform our own testing to verify your values. We may require you to 
test a small sub-sample of untested tire sizes that we select.
* * * * *
    (f) Engine characteristics. Enter information from the engine 
manufacturer to describe the installed engine and its operating 
parameters as described in 40 CFR 1036.505. Note that you do not need 
fuel consumption at idle for tractors.
* * * * *
    (h) * * *
    (1) For engines with no adjustable warm idle speed, input vehicle 
idle speed as the manufacturer's declared warm idle speed. For engines 
with adjustable warm idle speed, input your vehicle idle speed as 
follows:

------------------------------------------------------------------------
                                                          Your default
     If your vehicle is a         And your engine is      vehicle idle
                                      subject to          speed is \a\
------------------------------------------------------------------------
(i) Heavy HDV.................  compression-ignition    600 r/min.
                                 or spark-ignition
                                 standards.
(ii) Medium HDV tractor.......  compression-ignition    700 r/min.
                                 standards.
(iii) Light HDV or Medium HDV   compression-ignition    750 r/min.
 vocational vehicle.             standards.
(iv) Light HDV or Medium HDV..  spark-ignition          600 r/min.
                                 standards.
------------------------------------------------------------------------
\a\ If the default idle speed is above or below the engine
  manufacturer's whole range of declared warm idle speeds, use the
  manufacturer's maximum or minimum declared warm idle speed,
  respectively, instead of the default value.

* * * * *

0
119. Amend Sec.  1037.534 by revising paragraph (d)(2) to read as 
follows:

Sec.  1037.534  Constant-speed procedure for calculating drag area 
(CdA).

* * * * *
    (d) * * *
    (2) Perform testing as described in paragraph (d)(3) of this 
section over a sequence of test segments at constant vehicle speed as 
follows:
    (i) (300 30) seconds in each direction at 10 mi/hr.
    (ii) (450 30) seconds in each direction at 70 mi/hr.
    (iii) (450 30) seconds in each direction at 50 mi/hr.
    (iv) (450 30) seconds in each direction at 70 mi/hr.
    (v) (450 30) seconds in each direction at 50 mi/hr.
    (vi) (300 30) seconds in each direction at 10 mi/hr.
* * * * *

0
120. Amend Sec.  1037.540 by revising the introductory text and 
paragraphs (b)(3), (7), (8), and (f) to read as follows:

Sec.  1037.540  Special procedures for testing vehicles with hybrid 
power take-off.

    This section describes optional procedures for quantifying the 
reduction in greenhouse gas emissions for vehicles as a result of 
running power take-off (PTO) devices with a hybrid energy delivery 
system. See Sec.  1037.550 for powertrain testing requirements that 
apply for drivetrain hybrid systems. The procedures are written to test 
the PTO by ensuring that the engine produces all of the energy with no 
net change in stored energy (charge-sustaining), and

[[Page 4643]]

for plug-in hybrid vehicles, also allowing for drawing down the stored 
energy (charge-depleting). The full charge-sustaining test for the 
hybrid vehicle is from a fully charged rechargeable energy storage 
system (RESS) to a depleted RESS and then back to a fully charged RESS. 
You must include all hardware for the PTO system. You may ask us to 
modify the provisions of this section to allow testing hybrid vehicles 
other than battery electric hybrids, consistent with good engineering 
judgment. For plug-in hybrids, use a utility factor to properly weight 
charge-sustaining and charge-depleting operation as described in 
paragraph (f)(3) of this section.
* * * * *
    (b) * * *
    (3) Denormalize the PTO duty cycle in appendix B of this part using 
the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.078

Where:

prefi = the reference pressure at each point i in the PTO 
cycle.
pi = the normalized pressure at each point i in the PTO 
cycle (relative to pmax).
pmax = the mean maximum pressure measured in paragraph (b)(2) of 
this section.
pmin = the mean minimum pressure measured in paragraph (b)(2) of 
this section.
* * * * *
    (7) Depending on the number of circuits the PTO system has, operate 
the vehicle over one or concurrently over both of the denormalized PTO 
duty cycles in appendix B of this part. Measure emissions during 
operation over each duty cycle using the provisions of 40 CFR part 
1066.
    (8) Measured pressures must meet the cycle-validation 
specifications in the following table for each test run over the duty 
cycle:

Table 1 to Paragraph (b)(8) of Sec.   1037.540--Statistical Criteria for
              Validating Each Test Run Over the Duty Cycle
------------------------------------------------------------------------
               Parameter \a\                          Pressure
------------------------------------------------------------------------
Slope, a1.................................  0.950 <=a1 <=1.030.
Absolute value of intercept,                <=2.0% of maximum mapped
 [verbar]a0[verbar].                         pressure.
Standard error of the estimate, SEE.......  <=10% of maximum mapped
                                             pressure.
Coefficient of determination, r2..........  >=0.970.
------------------------------------------------------------------------
\a\ Determine values for specified parameters as described in 40 CFR
  1065.514(e) by comparing measured values to denormalized pressure
  values from the duty cycle in appendix B of this part.

* * * * *
    (f) For Phase 2, calculate the delta PTO fuel results for input 
into GEM during vehicle certification as follows:
    (1) Determine fuel consumption by calculating the mass of fuel for 
each test in grams, mfuelPTO, without rounding, as described 
in 40 CFR 1036.540(d)(12) for both the conventional vehicle and the 
charge-sustaining and charge-depleting portions of the test for the 
hybrid vehicle as applicable.
    (2) Divide the fuel mass by the applicable distance determined in 
paragraph (d)(4) of this section and the appropriate standard payload 
as defined in Sec.  1037.801 to determine the fuel-consumption rate in 
g/ton-mile.
    (3) For plug-in hybrid electric vehicles calculate the utility 
factor weighted fuel-consumption rate in g/ton-mile, as follows:
    (i) Determine the utility factor fraction for the PTO system from 
the table in appendix E of this part using interpolation based on the 
total time of the charge-depleting portion of the test as determined in 
paragraphs (c)(6) and (d)(3) of this section.
    (ii) Weight the emissions from the charge-sustaining and charge-
depleting portions of the test to determine the utility factor-weighted 
fuel mass, mfuelUF[cycle]plug-in, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.079

Where:

i = an indexing variable that represents one test interval.
N = total number of charge-depleting test intervals.
mfuelPTOCD = total mass of fuel per ton-mile in the 
charge-depleting portion of the test for each test interval, i, 
starting from i = 1.
UFDCDi = utility factor fraction at time tCDi 
as determined in paragraph (f)(3)(i) of this section for each test 
interval, i, starting from i = 1.
j = an indexing variable that represents one test interval.
M = total number of charge-sustaining test intervals.
mfuelPTOCS = total mass of fuel per ton-mile in the 
charge-sustaining portion of the test for each test interval, j, 
starting from j = 1.
UFRCD = utility factor fraction at the full charge-
depleting time, tCD, as determined by interpolating the 
approved utility factor curve. tCD is the sum of the time 
over N charge-depleting test intervals.

    (4) Calculate the difference between the conventional PTO emissions 
result and the hybrid PTO emissions result for input into GEM.
* * * * *

0
121. Revise Sec.  1037.550 to read as follows:

Sec.  1037.550  Powertrain testing.

    This section describes the procedure to measure fuel consumption 
and create engine fuel maps by testing a powertrain that includes an 
engine coupled with a transmission, drive axle, and hybrid components 
or any assembly with one or more of those hardware elements. Engine 
fuel maps are part of demonstrating compliance with Phase 2 vehicle 
standards under this part; the powertrain test procedure in this 
section is one option for generating this fuel-mapping information as 
described in 40 CFR 1036.505. Additionally, this powertrain test 
procedure is one option for certifying hybrids to the engine standards 
in 40 CFR 1036.108.
    (a) General test provisions. The following provisions apply broadly 
for testing under this section:
    (1) Measure NOX emissions as described in paragraph (k) 
of this section. Include these measured NOX values any time 
you report to us your greenhouse gas emissions or fuel consumption 
values from testing under this section.
    (2) The procedures of 40 CFR part 1065 apply for testing in this 
section except as specified. This section uses engine parameters and 
variables that are consistent with 40 CFR part 1065.
    (3) Powertrain testing depends on models to calculate certain 
parameters. You can use the detailed equations in this section to 
create your own models, or use the GEM HIL model contained within GEM 
Phase 2, Version 4.0 (incorporated by reference in Sec.  1037.810) to 
simulate vehicle hardware elements as follows:
    (i) Create driveline and vehicle models that calculate the angular 
speed

[[Page 4644]]

setpoint for the test cell dynamometer, fnref,dyno, based on 
the torque measurement location. Use the detailed equations in 
paragraph (f) of this section, the GEM HIL model's driveline and 
vehicle submodels, or a combination of the equations and the submodels. 
You may use the GEM HIL model's transmission submodel in paragraph (f) 
of this section to simulate a transmission only if testing hybrid 
engines.
    (ii) Create a driver model or use the GEM HIL model's driver 
submodel to simulate a human driver modulating the throttle and brake 
pedals to follow the test cycle as closely as possible.
    (iii) Create a cycle-interpolation model or use the GEM HIL model's 
cycle submodel to interpolate the duty-cycles and feed the driver model 
the duty-cycle reference vehicle speed for each point in the duty-
cycle.
    (4) The powertrain test procedure in this section is designed to 
simulate operation of different vehicle configurations over specific 
duty cycles. See paragraphs (h) and (j) of this section.
    (5) For each test run, record engine speed and torque as defined in 
40 CFR 1065.915(d)(5) with a minimum sampling frequency of 1 Hz. These 
engine speed and torque values represent a duty cycle that can be used 
for separate testing with an engine mounted on an engine dynamometer 
under Sec.  1037.551, such as for a selective enforcement audit as 
described in Sec.  1037.301.
    (6) For hybrid powertrains with no plug-in capability, correct for 
the net energy change of the energy storage device as described in 40 
CFR 1066.501. For plug-in hybrid electric powertrains, follow 40 CFR 
1066.501 to determine End-of-Test for charge-depleting operation. You 
must get our approval in advance for your utility factor curve; we will 
approve it if you can show that you created it, using good engineering 
judgment, from sufficient in-use data of vehicles in the same 
application as the vehicles in which the plug-in hybrid electric 
powertrain will be installed. You may use methodologies described in 
SAE J2841 (incorporated by reference in Sec.  1037.810) to develop the 
utility factor curve.
    (7) The provisions related to carbon balance error verification in 
40 CFR 1036.543 apply for all testing in this section. These procedures 
are optional if you are only performing direct or indirect fuel-flow 
measurement, but we will perform carbon balance error verification for 
all testing under this section.
    (8) Do not apply accessory loads when conducting a powertrain test 
to generate inputs to GEM if torque is measured at the axle input shaft 
or wheel hubs.
    (9) If you test a powertrain over the duty cycle specified in 40 
CFR 1036.514, control and apply the electrical accessory loads using 
one of the following systems:
    (i) An alternator with dynamic electrical load control.
    (ii) A load bank connected directly to the powertrain's electrical 
system.
    (b) Test configuration. Select a powertrain for testing as 
described in Sec.  1037.235 or 40 CFR 1036.235 as applicable. Set up 
the engine according to 40 CFR 1065.110 and 40 CFR 1065.405(b). Set the 
engine's idle speed to idle speed defined in Sec.  1037.520(h)(1).
    (1) The default test configuration consists of a powertrain with 
all components upstream of the axle. This involves connecting the 
powertrain's output shaft directly to the dynamometer or to a gear box 
with a fixed gear ratio and measuring torque at the axle input shaft. 
You may instead set up the dynamometer to connect at the wheel hubs and 
measure torque at that location. The preceeding sentence may apply if 
your powertrain configuration requires it, such as for hybrid 
powertrains or if you want to represent the axle performance with 
powertrain test results.
    (2) For testing hybrid engines, connect the engine's crankshaft 
directly to the dynamometer and measure torque at that location.
    (c) Powertrain temperatures during testing. Cool the powertrain 
during testing so temperatures for oil, coolant, block, head, 
transmission, battery, and power electronics are within the 
manufacturer's expected ranges for normal operation. You may use 
electronic control module outputs to comply with this paragraph (c). 
You may use auxiliary coolers and fans.
    (d) Engine break in. Break in the engine according to 40 CFR 
1065.405, the axle assembly according to Sec.  1037.560, and the 
transmission according to Sec.  1037.565. You may instead break in the 
powertrain as a complete system using the engine break in procedure in 
40 CFR 1065.405.
    (e) Dynamometer setup. Set the dynamometer to operate in speed-
control mode (or torque-control mode for hybrid engine testing at idle, 
including idle portions of transient duty cycles). Record data as 
described in 40 CFR 1065.202. Command and control the dynamometer speed 
at a minimum of 5 Hz, or 10 Hz for testing engine hybrids. Run the 
vehicle model to calculate the dynamometer setpoints at a rate of at 
least 100 Hz. If the dynamometer's command frequency is less than the 
vehicle model dynamometer setpoint frequency, subsample the calculated 
setpoints for commanding the dynamometer setpoints.
    (f) Driveline and vehicle model. Use the GEM HIL model's driveline 
and vehicle submodels or the equations in this paragraph (f) to 
calculate the dynamometer speed setpoint, fnref,dyno, based 
on the torque measurement location. For all powertrains, configure GEM 
with the accessory load set to zero. For hybrid engines, configure GEM 
with the applicable accessory load as specified in 40 CFR 1036.505 and 
1036.514. For all powertrains and hybrid engines, configure GEM with 
the tire slip model disabled.
    (1) Driveline model with a transmission in hardware. For testing 
with torque measurement at the axle input shaft or wheel hubs, 
calculate, fnref,dyno, using the GEM HIL model's driveline 
submodel or the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.080

Where:

ka[speed] = drive axle ratio as determined in paragraph 
(h) of this section. Set ka[speed] equal to 1.0 if torque 
is measured at the wheel hubs.
vrefi = simulated vehicle reference speed as calculated 
in paragraph (f)(3) of this section.
r[speed] = tire radius as determined in paragraph (h) of 
this section.

    (2) Driveline model with a simulated transmission. For testing with 
the torque measurement at the engine's crankshaft, 
fnref,dyno is the dynamometer target speed from the GEM HIL 
model's transmission submodel. You may request our approval to change 
the transmission submodel, as long as the changes do not affect the 
gear selection logic. Before testing, initialize the transmission model 
with the engine's measured torque curve and the applicable steady-state 
fuel map from the GEM HIL model. You may request our approval to input 
your own steady-state fuel map. For example, this request for approval 
could include using a fuel map that represents the combined performance 
of the engine and hybrid components. Configure the torque converter to 
simulate neutral idle when using this procedure to generate engine fuel 
maps in 40 CFR 1036.505 or to perform the Supplemental Emission Test 
(SET) testing under 40 CFR

[[Page 4645]]

1036.510. You may change engine commanded torque at idle to better 
represent CITT for transient testing under 40 CFR 1036.512. You may 
change the simulated engine inertia to match the inertia of the engine 
under test. We will evaluate your requests under this paragraph (f)(2) 
based on your demonstration that that the adjusted testing better 
represents in-use operation.
    (i) The transmission submodel needs the following model inputs:
    (A) Torque measured at the engine's crankshaft.
    (B) Engine estimated torque determined from the electronic control 
module or by converting the instantaneous operator demand to an 
instantaneous torque in N[middot]m.
    (C) Dynamometer mode when idling (speed-control or torque-control).
    (D) Measured engine speed when idling.
    (E) Transmission output angular speed, 
fni,transmission, calculated as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.081

Where:

ka[speed] = drive axle ratio as determined in paragraph 
(h) of this section.
vrefi = simulated vehicle reference speed as calculated 
in paragraph (f)(3) of this section.
r[speed] = tire radius as determined in paragraph (h) of 
this section.

    (ii) The transmission submodel generates the following model 
outputs:
    (A) Dynamometer target speed.
    (B) Dynamometer idle load.
    (C) Transmission engine load limit.
    (D) Engine speed target.
    (3) Vehicle model. Calculate the simulated vehicle reference speed, 
[nu]refi, using the GEM HIL model's vehicle submodel or the 
equations in this paragraph (f)(3):
[GRAPHIC] [TIFF OMITTED] TR24JA23.082

Where:

i = a time-based counter corresponding to each measurement during 
the sampling period. Let vref1 = 0; start calculations at 
i = 2. A 10-minute sampling period will generally involve 60,000 
measurements.
T = instantaneous measured torque at the axle input, measured at the 
wheel hubs, or simulated by the GEM HIL model's transmission 
submodel.
Effaxle = axle efficiency. Use Effaxle = 0.955 
for T >=0, and use Effaxle = \1/0\.955 for T <0. Use 
Effaxle = 1.0 if torque is measured at the wheel hubs.
M = vehicle mass for a vehicle class as determined in paragraph (h) 
of this section.
g = gravitational constant = 9.80665 m/s\2\.
Crr = coefficient of rolling resistance for a vehicle 
class as determined in paragraph (h) of this section.
Gi -1 = the percent grade interpolated at 
distance, D i-1, from the duty cycle in appendix D to 
this part corresponding to measurement i-1.

[GRAPHIC] [TIFF OMITTED] TR24JA23.083

[rho] = air density at reference conditions. Use [rho] = 1.1845 kg/
m\3\.
CdA = drag area for a vehicle class as determined in 
paragraph (h) of this section.
Fbrake,i-1 = instantaneous braking 
force applied by the driver model.
[GRAPHIC] [TIFF OMITTED] TR24JA23.084

[Delta]t = the time interval between measurements. For example, at 
100 Hz, [Delta]t = 0.0100 seconds.
Mrotating = inertial mass of rotating components. Let 
Mrotating = 340 kg for vocational Light HDV or vocational 
Medium HDV. See paragraph (h) of this section for tractors and for 
vocational Heavy HDV.

    (4) Example. The following example illustrates a calculation of 
fnref,dyno using paragraph (f)(1) of this section where 
torque is measured at the axle input shaft. This example is for a 
vocational Light HDV or vocational Medium HDV with 6 speed automatic 
transmission at B speed (Test 4 in Table 1 to paragraph (h)(2)(ii) of 
this section).

kaB = 4.0
rB = 0.399 m
T999 = 500.0 N[middot]m
Crr = 7.7 N/kN = 7.7[middot]10-\3\ N/N
M = 11408 kg
CdA = 5.4 m\2\
G999 = 0.39% = 0.0039
[GRAPHIC] [TIFF OMITTED] TR24JA23.085

Fbrake,999 = 0 N
vref,999 = 20.0 m/s
[Delta]t = 0.0100 s
Mrotating = 340 kg
[GRAPHIC] [TIFF OMITTED] TR24JA23.086

[[Page 4646]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.087

    (g) Driver model. Use the GEM HIL model's driver submodel or design 
a driver model to simulate a human driver modulating the throttle and 
brake pedals. In either case, tune the model to follow the test cycle 
as closely as possible meeting the following specifications:
    (1) The driver model must meet the following speed requirements:
    (i) For operation over the highway cruise cycles, the speed 
requirements described in 40 CFR 1066.425(b) and (c).
    (ii) For operation over the transient cycle specified in appendix A 
of this part, the SET as defined 40 CFR 1036.510, the Federal Test 
Procedure (FTP) as defined in 40 CFR 1036.512, and the Low Load Cycle 
(LLC) as defined in 40 CFR 1036.514, the speed requirements described 
in 40 CFR 1066.425(b) and (c).
    (iii) The exceptions in 40 CFR 1066.425(b)(4) apply to the highway 
cruise cycles, the transient cycle specified in appendix A of this 
part, SET, FTP, and LLC.
    (iv) If the speeds do not conform to these criteria, the test is 
not valid and must be repeated.
    (2) Send a brake signal when operator demand is zero and vehicle 
speed is greater than the reference vehicle speed from the test cycle. 
Include a delay before changing the brake signal to prevent dithering, 
consistent with good engineering judgment.
    (3) Allow braking only if operator demand is zero.
    (4) Compensate for the distance driven over the duty cycle over the 
course of the test. Use the following equation to perform the 
compensation in real time to determine your time in the cycle:
[GRAPHIC] [TIFF OMITTED] TR24JA23.088

Where:

vvehicle = measured vehicle speed.
    vcycle = reference speed from the test cycle. If v 
cycle,i -1 <1.0 m/s, set 
vcycle,i-1 = 
vvehicle,i-1.

    (h) Vehicle configurations to evaluate for generating fuel 
maps as defined in 40 CFR 1036.505. Configure the driveline and vehicle 
models from paragraph (f) of this section in the test cell to test the 
powertrain. Simulate multiple vehicle configurations that represent the 
range of intended vehicle applications using one of the following 
options:
    (1) For known vehicle configurations, use at least three equally 
spaced axle ratios or tire sizes and three different road loads (nine 
configurations), or at least four equally spaced axle ratios or tire 
sizes and two different road loads (eight configurations). Select axle 
ratios to represent the full range of expected vehicle installations. 
Select axle ratios and tire sizes such that the ratio of engine speed 
to vehicle speed covers the range of ratios of minimum and maximum 
engine speed to vehicle speed when the transmission is in top gear for 
the vehicles in which the powertrain will be installed. Note that you 
do not have to use the same axle ratios and tire sizes for each GEM 
regulatory subcategory. You may determine appropriate 
Crr, CdA, and mass values to cover the range of 
intended vehicle applications or you may use the 
Crr, CdA, and mass values specified in paragraph 
(h)(2) of this section.
    (2) If vehicle configurations are not known, determine the vehicle 
model inputs for a set of vehicle configurations as described in 40 CFR 
1036.540(c)(3) with the following exceptions:
    (i) In the equations of 40 CFR 1036.540(c)(3)(i), 
ktopgear is the actual top gear ratio of the powertrain 
instead of the transmission gear ratio in the highest available gear 
given in Table 1 in 40 CFR 1036.540.
    (ii) Test at least eight different vehicle configurations for 
powertrains that will be installed in Spark-ignition HDE, vocational 
Light HDV, and vocational Medium HDV using the following table instead 
of Table 2 in 40 CFR 1036.540:

[[Page 4647]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.089

    (iii) Select and test vehicle configurations as described in 40 CFR 
1036.540(c)(3)(iii) for powertrains that will be installed in 
vocational Heavy HDV and tractors using the following tables instead of 
Table 3 and Table 4 in 40 CFR 1036.540:

[[Page 4648]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.090

    (3) For hybrid powertrain systems where the transmission will be 
simulated, use the transmission parameters defined in 40 CFR 
1036.540(c)(2) to determine transmission type and gear ratio. Use a 
fixed transmission efficiency of 0.95. The GEM HIL transmission model 
uses a transmission parameter file for each test that includes the 
transmission type, gear ratios, lockup gear, torque limit per gear from 
40 CFR 1036.540(c)(2), and the values from 40 CFR 1036.505(b)(4) and 
(c).
    (i) [Reserved]
    (j) Duty cycles to evaluate. Operate the powertrain over each of 
the duty cycles specified in Sec.  1037.510(a)(2), and for each 
applicable vehicle configuration from paragraph (h) of this section. 
Determine cycle-average powertrain fuel maps by testing the powertrain 
using the procedures in 40 CFR 1036.540(d) with the following 
exceptions:
    (1) Understand ``engine'' to mean ``powertrain''.
    (2) Warm up the powertrain as described in 40 CFR 1036.520(c)(1).
    (3) Within 90 seconds after concluding the warm-up, start the 
transition to the preconditioning cycle as described in paragraph 
(j)(5) of this section.
    (4) For plug-in hybrid engines, precondition the battery and then 
complete all back-to-back tests for each vehicle configuration 
according to 40 CFR 1066.501 before moving to the next vehicle 
configuration.
    (5) If the preceding duty cycle does not end at 0 mi/hr, transition 
between duty cycles by decelerating at a rate of 2 mi/hr/s at 0% grade 
until the vehicle reaches zero speed. Shut off the powertrain. Prepare 
the powertrain and test cell for the next duty-cycle.
    (6) Start the next duty-cycle within 60 to 180 seconds after 
shutting off the powertrain.
    (i) To start the next duty-cycle, for hybrid powertrains, key on 
the vehicle and then start the duty-cycle. For conventional powertrains 
key on the vehicle, start the engine, wait for the engine to stabilize 
at idle speed, and then start the duty-cycle.
    (ii) If the duty-cycle does not start at 0 mi/hr, transition to the 
next duty cycle by accelerating at a target rate of 1 mi/hr/s at 0% 
grade. Stabilize for 10 seconds at the initial duty cycle conditions 
and start the duty-cycle.
    (7) Calculate cycle work using GEM or the speed and torque from the 
driveline and vehicle models from paragraph (f) of this section to 
determine the sequence of duty cycles.
    (8) Calculate the mass of fuel consumed for idle duty cycles as

[[Page 4649]]

described in paragraph (n) of this section.
    (k) Measuring NOX emissions. Measure NOX 
emissions for each sampling period in grams. You may perform these 
measurements using a NOX emission-measurement system that 
meets the requirements of 40 CFR part 1065, subpart J. If a system 
malfunction prevents you from measuring NOX emissions during 
a test under this section but the test otherwise gives valid results, 
you may consider this a valid test and omit the NOX emission 
measurements; however, we may require you to repeat the test if we 
determine that you inappropriately voided the test with respect to 
NOX emission measurement.
    (l) [Reserved]
    (m) Measured output speed validation. For each test point, validate 
the measured output speed with the corresponding reference values. If 
the range of reference speed is less than 10 percent of the mean 
reference speed, you need to meet only the standard error of the 
estimate in Table 1 of this section. You may delete points when the 
vehicle is stopped. If your speed measurement is not at the location of 
fnref, correct your measured speed using the constant speed 
ratio between the two locations. Apply cycle-validation criteria for 
each separate transient or highway cruise cycle based on the following 
parameters:

  Table 4 to Paragraph (m) of Sec.   1037.550--Statistical Criteria for
                         Validating Duty Cycles
------------------------------------------------------------------------
               Parameter \a\                        Speed control
------------------------------------------------------------------------
Slope, a1.................................  0.990 <=a1 <=1.010.
Absolute value of intercept,                <=2.0% of maximum fnref
 [bond]a0[bond].                             speed.
Standard error of the estimate, SEE.......  <=2.0% of maximum fnref
                                             speed.
Coefficient of determination, r\2\........  >=0.990.
------------------------------------------------------------------------
\a\ Determine values for specified parameters as described in 40 CFR
  1065.514(e) by comparing measured and reference values for fnref,dyno.

    (n) Fuel consumption at idle. Record measurements using direct and/
or indirect measurement of fuel flow. Determine the fuel-consumption 
rates at idle for the applicable duty cycles described in Sec.  
1037.510(a)(2) as follows:
    (1) Direct fuel flow measurement. Determine the corresponding mean 
values for mean idle fuel mass flow rate, mIfuelidle, for 
each duty cycle, as applicable. Use of redundant direct fuel-flow 
measurements require our advance approval.
    (2) Indirect fuel flow measurement. Record speed and torque and 
measure emissions and other inputs needed to run the chemical balance 
in 40 CFR 1065.655(c). Determine the corresponding mean values for each 
duty cycle. Use of redundant indirect fuel-flow measurements require 
our advance approval. Measure background concentration as described in 
40 CFR 1036.535(b)(4)(ii). We recommend setting the CVS flow rate as 
low as possible to minimize background, but without introducing errors 
related to insufficient mixing or other operational considerations. 
Note that for this testing 40 CFR 1065.140(e) does not apply, including 
the minimum dilution ratio of 2:1 in the primary dilution stage. 
Calculate the idle fuel mass flow rate for each duty cycle, 
mIfuelidle, for each set of vehicle settings, as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.091

Where:

MC = molar mass of carbon.
wCmeas = carbon mass fraction of fuel (or mixture of test 
fuels) as determined in 40 CFR 1065.655(d), except that you may not 
use the default properties in Table 2 of 40 CFR 1065.655 to 
determine [alpha], [beta], and wC for liquid fuels.
niexh = the mean raw exhaust molar flow rate from which 
you measured emissions according to 40 CFR 1065.655.
xCcombdry = the mean concentration of carbon from fuel 
and any injected fluids in the exhaust per mole of dry exhaust.
xH2Oexhdry = the mean concentration of 
H2O in exhaust per mole of dry exhaust.
mICO2DEF = the mean CO2 mass 
emission rate resulting from diesel exhaust fluid decomposition over 
the duty cycle as determined in 40 CFR 1036.535(b)(9). If your 
engine does not use diesel exhaust fluid, or if you choose not to 
perform this correction, set miCO2DEF equal to 
0.
MCO2 = molar mass of carbon dioxide.

Example:

MC = 12.0107 g/mol
wCmeas = 0.867
niexh = 25.534 mol/s
xCcombdry = 2.805[middot]10-\3\ mol/mol
xH2Oexhdry = 3.53[middot]10-\2\ mol/
mol
miCO2DEF = 0.0726 g/s
MCO2 = 44.0095
[GRAPHIC] [TIFF OMITTED] TR24JA23.092

mifuelidle = 0.405 g/s = 1458.6 g/hr
    (o) Create GEM inputs. Use the results of powertrain testing to 
determine GEM inputs for the different simulated vehicle configurations 
as follows:
    (1) Correct the measured or calculated fuel masses, 
mfuel[cycle], and mean idle fuel mass flow rates, 
mifuelidle, if applicable, for each test result to a mass-
specific net energy content of a reference fuel as described in 40 CFR 
1036.535(e), replacing mifuel with mfuel[cycle] 
where applicable in Eq. 1036.535-4.
    (2) Declare fuel masses, mfuel[cycle] and 
mifuelidle. Determine mfuel[cycle] using the 
calculated fuel mass consumption values described in 40 CFR 
1036.540(d)(12). In addition, declare mean fuel mass flow rate for each 
applicable idle duty cycle, mifuelidle. These declared 
values may not be lower than any corresponding measured values 
determined in this section. If you use both direct and indirect 
measurement of fuel flow, determine the corresponding declared values 
as described in 40 CFR 1036.535(g)(2) and (3). These declared values, 
which serve as emission standards, collectively represent the 
powertrain fuel map for certification.
    (3) For engines designed for plug-in hybrid electric vehicles, the 
mass of fuel for each cycle, mfuel[cycle], is the utility 
factor-weighted fuel mass, mfuelUF[cycle]. This is 
determined by calculating mfuel for the full charge-
depleting and charge-sustaining portions of the test and

[[Page 4650]]

weighting the results, using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.093

Where:

i = an indexing variable that represents one test interval.
N = total number of charge-depleting test intervals.
mfuel[cycle]CDi = total mass of fuel in the charge-
depleting portion of the test for each test interval, i, starting 
from i = 1, including the test interval(s) from the transition 
phase.
UFDCDi = utility factor fraction at distance 
DCDi from Eq. 1037.505-9 as determined by interpolating 
the approved utility factor curve for each test interval, i, 
starting from i = 1. Let UFDCD0 = 0
j = an indexing variable that represents one test interval.
M = total number of charge-sustaining test intervals.
mfuel[cycle]CSj = total mass of fuel over the charge-
sustaining portion of the test for each test interval, j, starting 
from j = 1.
UFRCD = utility factor fraction at the full charge-
depleting distance, RCD, as determined by interpolating 
the approved utility factor curve. RCD is the cumulative 
distance driven over N charge-depleting test intervals.
[GRAPHIC] [TIFF OMITTED] TR24JA23.094

Where:

k = an indexing variable that represents one recorded velocity 
value.
Q = total number of measurements over the test interval.
v = vehicle velocity at each time step, k, starting from k = 1. For 
tests completed under this section, v is the vehicle velocity as 
determined by Eq. 1037.550-1. Note that this should include charge-
depleting test intervals that start when the engine is not yet 
operating.
[Delta]t = 1/frecord
frecord = the record rate.

Example for the 55 mi/hr Cruise Cycle:

Q = 8790
v1 = 55.0 mi/hr
v2 = 55.0 mi/hr
v3 = 55.1 mi/hr
frecord = 10 Hz
[Delta]t = 1/10 Hz = 0.1 s
[GRAPHIC] [TIFF OMITTED] TR24JA23.095

DCD2 = 13.4 mi
DCD3 = 13.4 mi
N = 3
UFDCD1 = 0.05
UFDCD2 = 0.11
UFDCD3 = 0.21
mfuel55cruiseCD1 = 0 g
mfuel55cruiseCD2 = 0 g
mfuel55cruiseCD3 = 1675.4 g
M = 1
mfuel55cruiseCS = 4884.1 g
UFRCD = 0.21
[GRAPHIC] [TIFF OMITTED] TR24JA23.096

mfuelUF55cruise = 4026.0 g
    (4) For the transient cycle specified in Sec.  1037.510(a)(2)(i), 
calculate powertrain output speed per unit of vehicle speed,
[GRAPHIC] [TIFF OMITTED] TR24JA23.097

using one of the following methods:
    (i) For testing with torque measurement at the axle input shaft:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.098
    
Example:

ka = 4.0
rB = 0.399 m
[GRAPHIC] [TIFF OMITTED] TR24JA23.099

[[Page 4651]]

    (ii) For testing with torque measurement at the wheel hubs, use Eq. 
1037.550-8 setting ka equal to 1.
    (iii) For testing with torque measurement at the engine's 
crankshaft:
[GRAPHIC] [TIFF OMITTED] TR24JA23.100

Where:

fnengine = average engine speed when vehicle speed is at 
or above 0.100 m/s.
vref = average simulated vehicle speed at or above 0.100 
m/s.

Example:

fnengine = 1870 r/min = 31.17 r/s
vref = 19.06 m/s
[GRAPHIC] [TIFF OMITTED] TR24JA23.101

    (5) Calculate engine idle speed, by taking the average engine speed 
measured during the transient cycle test while the vehicle speed is 
below 0.100 m/s. (Note: Use all the charge-sustaining test intervals 
when determining engine idle speed for plug-in hybrid engines and 
powertrains.)
    (6) For the cruise cycles specified in Sec.  1037.510(a)(2)(ii), 
calculate the average powertrain output speed, fnpowertrain, 
and the average powertrain output torque (positive torque only), 
Tpowertrain, at vehicle speed at or above 0.100 m/s. (Note: 
Use all the charge-sustaining and charge-depleting test intervals when 
determining fnpowertrain and Tpowertrain for 
plug-in hybrid engines and powertrains.)
    (7) Calculate positive work, W[cycle], as the work over 
the duty cycle at the axle input shaft, wheel hubs, or the engine's 
crankshaft, as applicable, when vehicle speed is at or above 0.100 m/s. 
For plug-in hybrids engines and powertrains, calculate, 
W[cycle], by calculating the positive work over each of the 
charge-sustaining and charge-depleting test intervals and then 
averaging them together.
    (8) The following tables illustrate the GEM data inputs 
corresponding to the different vehicle configurations for a given duty 
cycle:
    (i) For the transient cycle:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.102
    
    (ii) For the cruise cycles:

              Table 6 to Paragraph (o)(8)(ii) of Sec.   1037.550--Generic Example of Output Matrix for Cruise Cycle Vehicle Configurations
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                        Configuration
             Parameter              --------------------------------------------------------------------------------------------------------------------
                                          1            2            3            4            5            6            7           ...           n
--------------------------------------------------------------------------------------------------------------------------------------------------------
mfuel[cycle].......................
fnpowertrain[cycle]................
Tpowertrain[cycle].................
W[cycle]...........................
--------------------------------------------------------------------------------------------------------------------------------------------------------

[[Page 4652]]

0
122. Amend Sec.  1037.551 by revising the introductory text and 
paragraphs (b) and (c) to read as follows:

Sec.  1037.551  Engine-based simulation of powertrain testing.

    Section 1037.550 describes how to measure fuel consumption over 
specific duty cycles with an engine coupled to a transmission; Sec.  
1037.550(a)(5) describes how to create equivalent duty cycles for 
repeating those same measurements with just the engine. This Sec.  
1037.551 describes how to perform this engine testing to simulate the 
powertrain test. These engine-based measurements may be used for 
selective enforcement audits as described in Sec.  1037.301, as long as 
the test engine's operation represents the engine operation observed in 
the powertrain test. If we use this approach for confirmatory testing, 
when making compliance determinations, we will consider the uncertainty 
associated with this approach relative to full powertrain testing. Use 
of this approach for engine SEAs is optional for engine manufacturers.
* * * * *
    (b) Operate the engine over the applicable engine duty cycles 
corresponding to the vehicle cycles specified in Sec.  1037.510(a)(2) 
for powertrain testing over the applicable vehicle simulations 
described in Sec.  1037.550(j). Warm up the engine to prepare for the 
transient test or one of the highway cruise cycles by operating it one 
time over one of the simulations of the corresponding duty cycle. Warm 
up the engine to prepare for the idle test by operating it over a 
simulation of the 65-mi/hr highway cruise cycle for 600 seconds. Within 
60 seconds after concluding the warm up cycle, start emission sampling 
while the engine operates over the duty cycle. You may perform any 
number of test runs directly in succession once the engine is warmed 
up. Perform cycle validation as described in 40 CFR 1065.514 for engine 
speed, torque, and power.
    (c) Calculate the mass of fuel consumed as described in Sec.  
1037.550(n) and (o). Correct each measured value for the test fuel's 
mass-specific net energy content as described in 40 CFR 1036.550. Use 
these corrected values to determine whether the engine's emission 
levels conform to the declared fuel-consumption rates from the 
powertrain test.

0
123. Amend Sec.  1037.555 by revising the introductory text and 
paragraph (g) to read as follows:

Sec.  1037.555  Special procedures for testing Phase 1 hybrid systems.

    This section describes a powertrain testing procedure for 
simulating a chassis test with a pre-transmission or post-transmission 
hybrid system to perform A to B testing of Phase 1 vehicles. These 
procedures may also be used to perform A to B testing with non-hybrid 
systems. See Sec.  1037.550 for Phase 2 hybrid systems.
* * * * *
    (g) The driver model should be designed to follow the cycle as 
closely as possible and must meet the requirements of Sec.  1037.510 
for steady-state testing and 40 CFR 1066.425 for transient testing. The 
driver model should be designed so that the brake and throttle are not 
applied at the same time.
* * * * *

0
124. Amend Sec.  1037.560 by revising paragraph (c) to read as follows:

Sec.  1037.560  Axle efficiency test.

* * * * *
    (c) Measure input and output speed and torque as described in 40 
CFR 1065.210(b). You must use a speed-measurement system that meets an 
accuracy of 0.05% of point. Use torque transducers that 
meet an accuracy requirement of 1.0 N[middot]m for unloaded 
test points and 0.2% of the maximum tested axle input 
torque or output torque, respectively, for loaded test points. 
Calibrate and verify measurement instruments according to 40 CFR part 
1065, subpart D. Command speed and torque at a minimum of 10 Hz, and 
record all data, including bulk oil temperature, at a minimum of 1 Hz 
mean values.
* * * * *

0
125. Amend Sec.  1037.601 by revising paragraphs (a)(1) and (c) to read 
as follows:

Sec.  1037.601  General compliance provisions.

    (a) * * *
    (1) Except as specifically allowed by this part or 40 CFR part 
1068, it is a violation of 40 CFR 1068.101(a)(1) to introduce into U.S. 
commerce either a tractor or vocational vehicle that is not certified 
to the applicable requirements of this part or a tractor or vocational 
vehicle containing an engine that is not certified to the applicable 
requirements of 40 CFR part 86 or 1036. Further, it is a violation to 
introduce into U.S. commerce a Phase 1 tractor containing an engine not 
certified for use in tractors; or to introduce into U.S. commerce a 
vocational vehicle containing a Light HDE or Medium HDE not certified 
for use in vocational vehicles. These prohibitions apply especially to 
the vehicle manufacturer. Note that this paragraph (a)(1) allows the 
use of Heavy heavy-duty tractor engines in vocational vehicles.
* * * * *
    (c) The prohibitions of 40 CFR 1068.101 apply for vehicles subject 
to the requirements of this part. The following specific provisions 
apply:
    (1) The actions prohibited under this provision include introducing 
into U.S. commerce a complete or incomplete vehicle subject to the 
standards of this part where the vehicle is not covered by a valid 
certificate of conformity or exemption.
    (2) Applying a Clean Idle sticker to a vehicles with an installed 
engine that is not certified to the NOX standard of 40 CFR 
1036.104(b) violates the prohibition in 40 CFR 1068.101(b)(7)(iii).
* * * * *

0
126. Amend Sec.  1037.605 by revising paragraphs (a) introductory text 
and (a)(4) to read as follows:

Sec.  1037.605  Installing engines certified to alternate standards for 
specialty vehicles.

    (a) General provisions. This section allows vehicle manufacturers 
to introduce into U.S. commerce certain new motor vehicles using 
engines certified to alternate emission standards specified in 40 CFR 
1036.605 for motor vehicle engines used in specialty vehicles. You may 
not install an engine certified to these alternate standards if there 
is an engine certified to the full set of requirements of 40 CFR part 
1036 that has the appropriate physical and performance characteristics 
to power the vehicle. Note that, although these alternate emission 
standards are mostly equivalent to standards that apply for nonroad 
engines under 40 CFR part 1039 or 1048, they are specific to motor 
vehicle engines. The provisions of this section apply for the following 
types of specialty vehicles:
* * * * *
    (4) Through model year 2027, vehicles with a hybrid powertrain in 
which the engine provides energy only for the Rechargeable Energy 
Storage System.
* * * * *

0
127. Amend Sec.  1037.615 by revising paragraph (f) to read as follows:

Sec.  1037.615  Advanced technologies.

* * * * *
    (f) For electric vehicles and for fuel cells powered by hydrogen, 
calculate CO2 credits using an FEL of 0 g/ton-mile. Note 
that these vehicles are subject to compression-ignition standards for 
CO2.
* * * * *

[[Page 4653]]

0
128. Amend Sec.  1037.635 by revising paragraph (b)(2) to read as 
follows:

Sec.  1037.635  Glider kits and glider vehicles.

* * * * *
    (b) * * *
    (2) The engine must meet the criteria pollutant standards of 40 CFR 
part 86 or 40 CFR part 1036 that apply for the engine model year 
corresponding to the vehicle's date of manufacture.
* * * * *

0
129. Amend Sec.  1037.705 by revising paragraph (b) to read as follows:

Sec.  1037.705  Generating and calculating emission credits.

* * * * *
    (b) For each participating family or subfamily, calculate positive 
or negative emission credits relative to the otherwise applicable 
emission standard. Calculate positive emission credits for a family or 
subfamily that has an FEL below the standard. Calculate negative 
emission credits for a family or subfamily that has an FEL above the 
standard. Sum your positive and negative credits for the model year 
before rounding. Round the sum of emission credits to the nearest 
megagram (Mg), using consistent units with the following equation:

Emission credits (Mg) = (Std-FEL) x PL x Volume x UL x 10 
-\6\

Where:
Std = the emission standard associated with the specific regulatory 
subcategory (g/ton-mile).
FEL = the family emission limit for the vehicle subfamily (g/ton-
mile).
PL = standard payload, in tons.
    Volume = U.S.-directed production volume of the vehicle 
subfamily. For example, if you produce three configurations with the 
same FEL, the subfamily production volume would be the sum of the 
production volumes for these three configurations.
    UL = useful life of the vehicle, in miles, as described in 
Sec. Sec.  1037.105 and 1037.106. Use 250,000 miles for trailers.
* * * * *

0
130. Amend Sec.  1037.725 by revising the section heading to read as 
follows:

Sec.  1037.725  Required information for certification.

* * * * *

0
131. Amend Sec.  1037.730 by revising paragraphs (a), (b) introductory 
text, (c), and (f) to read as follows:

Sec.  1037.730  ABT reports.

    (a) If you certify any vehicle families using the ABT provisions of 
this subpart, send us a final report by September 30 following the end 
of the model year.
    (b) Your report must include the following information for each 
vehicle family participating in the ABT program:
* * * * *
    (c) Your report must include the following additional information:
    (1) Show that your net balance of emission credits from all your 
participating vehicle families in each averaging set in the applicable 
model year is not negative, except as allowed under Sec.  1037.745. 
Your credit tracking must account for the limitation on credit life 
under Sec.  1037.740(c).
    (2) State whether you will retain any emission credits for banking. 
If you choose to retire emission credits that would otherwise be 
eligible for banking, identify the families that generated the emission 
credits, including the number of emission credits from each family.
    (3) State that the report's contents are accurate.
    (4) Identify the technologies that make up the certified 
configuration associated with each vehicle identification number. You 
may identify this as a range of identification numbers for vehicles 
involving a single, identical certified configuration.
* * * * *
    (f) Correct errors in your report as follows:
    (1) If you or we determine by September 30 after the end of the 
model year that errors mistakenly decreased your balance of emission 
credits, you may correct the errors and recalculate the balance of 
emission credits. You may not make these corrections for errors that 
are determined later than September 30 after the end of the model year. 
If you report a negative balance of emission credits, we may disallow 
corrections under this paragraph (f)(1).
    (2) If you or we determine any time that errors mistakenly 
increased your balance of emission credits, you must correct the errors 
and recalculate the balance of emission credits.

0
132. Amend Sec.  1037.735 by revising paragraph (b) to read as follows:

Sec.  1037.735  Recordkeeping.

* * * * *
    (b) Keep the records required by this section for at least eight 
years after the due date for the final report. You may not use emission 
credits for any vehicles if you do not keep all the records required 
under this section. You must therefore keep these records to continue 
to bank valid credits.
* * * * *

0
133. Amend Sec.  1037.740 by revising paragraph (b) to read as follows:

Sec.  1037.740  Restrictions for using emission credits.

* * * * *
    (b) Credits from hybrid vehicles and other advanced technologies. 
The following provisions apply for credits you generate under Sec.  
1037.615.
    (1) Credits generated from Phase 1 vehicles may be used for any of 
the averaging sets identified in paragraph (a) of this section; you may 
also use those credits to demonstrate compliance with the 
CO2 emission standards in 40 CFR 86.1819 and 40 CFR part 
1036. Similarly, you may use Phase 1 advanced-technology credits 
generated under 40 CFR 86.1819-14(k)(7) or 40 CFR 1036.615 to 
demonstrate compliance with the CO2 standards in this part. 
The maximum amount of advanced-technology credits generated from Phase 
1 vehicles that you may bring into each of the following service class 
groups is 60,000 Mg per model year:
    (i) Spark-ignition HDE, Light HDE, and Light HDV. This group 
comprises the averaging set listed in paragraph (a)(1) of this section 
and the averaging set listed in 40 CFR 1036.740(a)(1) and (2).
    (ii) Medium HDE and Medium HDV. This group comprises the averaging 
sets listed in paragraph (a)(2) of this section and 40 CFR 
1036.740(a)(3).
    (iii) Heavy HDE and Heavy HDV. This group comprises the averaging 
sets listed in paragraph (a)(3) of this section and 40 CFR 
1036.740(a)(4).
    (iv) This paragraph (b)(1) does not limit the advanced-technology 
credits that can be used within a service class group if they were 
generated in that same service class group.
    (2) Credits generated from Phase 2 vehicles are subject to all the 
averaging-set restrictions that apply to other emission credits.
* * * * *

0
134. Amend Sec.  1037.801 by:
0
a. Revising the definitions of ``Adjustable parameter'', ``Automatic 
tire inflation system'', and ``Automatic transmission (AT)'';
0
b. Adding definitions of ``Charge-depleting'', and ``Charge-
sustaining'' in alphabetical order;
0
c. Revising the definitions of ``Designated Compliance Officer'' and of 
``Electric vehicle'';
0
d. Adding a definition of ``Emission-related component'' in 
alphabetical order; and
0
e. Revising the definitions of ``Low rolling resistance tire'', 
``Neutral coasting'', ``Rechargeable Energy Storage System (RESS)'', 
and ``Tire rolling resistance level (TRRL)''.
    The additions and revisions read as follows:

[[Page 4654]]

Sec.  1037.801  Definitions.

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.30.
* * * * *
    Automatic tire inflation system means a pneumatically or 
electronically activated system installed on a vehicle to maintain tire 
pressure at a preset level. These systems eliminate the need to 
manually inflate tires. Note that this is different than a tire 
pressure monitoring system, which we define separately in this section.
    Automatic transmission (AT) means a transmission with a torque 
converter (or equivalent) that uses computerize or other internal 
controls to shift gears in response to a single driver input for 
controlling vehicle speed.. Note that automatic manual transmissions 
are not automatic transmissions because they do not include torque 
converters.
* * * * *
    Charge-depleting has the meaning given in 40 CFR 1066.1001.
    Charge-sustaining has the meaning given in 40 CFR 1066.1001.
* * * * *
    Designated Compliance Officer means one of the following:
    (1) For compression-ignition engines, Designated Compliance Officer 
means Director, Diesel Engine Compliance Center, U.S. Environmental 
Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 
[email protected]; www.epa.gov/ve-certification.
    (2) For spark-ignition engines, Designated Compliance Officer means 
Director, Gasoline Engine Compliance Center, U.S. Environmental 
Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 
[email protected]; www.epa.gov/ve-certification.
* * * * *
    Electric vehicle means a motor vehicle that does not include an 
engine, and is powered solely by an external source of electricity and/
or solar power. Note that this definition does not include hybrid 
electric vehicles or fuel cell vehicles that use a chemical fuel such 
as gasoline, diesel fuel, or hydrogen. Electric vehicles may also be 
referred to as all-electric vehicles to distinguish them from hybrid 
vehicles.
* * * * *
    Emission-related component has the meaning given in 40 CFR part 
1068, appendix A.
* * * * *
    Low rolling resistance tire means a tire on a vocational vehicle 
with a TRRL at or below of 7.7 N/kN, a steer tire on a tractor with a 
TRRL at or below 7.7 N/kN, a drive tire on a tractor with a TRRL at or 
below 8.1 N/kN, a tire on a non-box trailer with a TRRL at or below of 
6.5 N/kN, or a tire on a box van with a TRRL at or below of 6.0 N/kN.
* * * * *
    Neutral coasting means a vehicle technology that automatically puts 
the transmission in neutral when the vehicle has minimal power demand 
while in motion, such as driving downhill.
* * * * *
    Rechargeable Energy Storage System (RESS) has the meaning given in 
40 CFR 1065.1001.
* * * * *
    Tire rolling resistance level (TRRL) means a value with units of N/
kN that represents the rolling resistance of a tire configuration. 
TRRLs are used as modeling inputs under Sec. Sec.  1037.515 and 
1037.520. Note that a manufacturer may use the measured value for a 
tire configuration's coefficient of rolling resistance, or assign some 
higher value.
* * * * *

0
135. Amend Sec.  1037.805 by revising paragraphs (a), (b), (d), (e), 
(f), and (g) to read as follows:

Sec.  1037.805  Symbols, abbreviations, and acronyms.

* * * * *
    (a) Symbols for chemical species. This part uses the following 
symbols for chemical species and exhaust constituents:

    Table 1 to Paragraph (a) of Sec.   1037.805--Symbols for Chemical
                    Species and Exhaust Constituents
------------------------------------------------------------------------
                  Symbol                               Species
------------------------------------------------------------------------
C.........................................  carbon.
CH4.......................................  methane.
CO........................................  carbon monoxide.
CO2.......................................  carbon dioxide.
H2O.......................................  water.
HC........................................  hydrocarbon.
NMHC......................................  nonmethane hydrocarbon.
NMHCE.....................................  nonmethane hydrocarbon
                                             equivalent.
NO........................................  nitric oxide.
NO2.......................................  nitrogen dioxide.
NOX.......................................  oxides of nitrogen.
N2O.......................................  nitrous oxide.
PM........................................  particulate matter.
THC.......................................  total hydrocarbon.
THCE......................................  total hydrocarbon
                                             equivalent.
------------------------------------------------------------------------

    (b) Symbols for quantities. This part 1037 uses the following 
symbols and units of measure for various quantities:

                       Table 2 to Paragraph (b) of Sec.   1037.805--Symbols for Quantities
----------------------------------------------------------------------------------------------------------------
                                                                                        Unit in terms of SI base
      Symbol             Quantity             Unit                 Unit symbol                    units
----------------------------------------------------------------------------------------------------------------
A.................  vehicle            pound force or     lbf or N....................  kg[middot]m[middot]s-
                     frictional load.   newton.                                          \2\.
a.................  axle position
                     regression
                     coefficient.
[alpha]...........  atomic hydrogen-   mole per mole....  mol/mol.....................  1.
                     to-carbon ratio.
[alpha]...........  axle position
                     regression
                     coefficient.
[alpha]0..........  intercept of air
                     speed correction.
[alpha]1..........  slope of air
                     speed correction.
ag................  acceleration of    meters per second  m/s\2\......................  m[middot]s-\2\.
                     Earth's gravity.   squared.
a0................  intercept of
                     least squares
                     regression.
a1................  slope of least
                     squares
                     regression.
B.................  vehicle load from  pound force per    lbf/(mi/hr) or N[middot]s/m.  kg[middot]s-\1\.
                     drag and rolling   mile per hour or
                     resistance.        newton second
                                        per meter.
b.................  axle position
                     regression
                     coefficient.
[beta]............  atomic oxygen-to-  mole per mole....  mol/mol.....................  1.
                     carbon ratio.
[beta]............  axle position
                     regression
                     coefficient.
[beta]0...........  intercept of air
                     direction
                     correction.
[beta]1...........  slope of air
                     direction
                     correction.
C.................  vehicle-specific   pound force per    lbf/mph\2\ or N[middot]s\2\/  kg[middot]m-\1\.
                     aerodynamic        mile per hour      m\2\.
                     effects.           squared or
                                        newton-second
                                        squared per
                                        meter squared.
c.................  axle position
                     regression
                     coefficient.

[[Page 4655]]

 
ci................  axle test
                     regression
                     coefficients.
Ci................  constant.........
[Delta]CdA........  differential drag  meter squared....  m\2\........................  m\2\.
                     area.
CdA...............  drag area........  meter squared....  m\2\........................  m\2\.
Cd................  drag coefficient.
CF................  correction factor
Crr...............  coefficient of     newton per         N/kN........................  10-\3\.
                     rolling            kilonewton.
                     resistance.
D.................  distance.........  miles or meters..  mi or m.....................  m.
e.................  mass-weighted      grams per ton-     g/ton-mi....................  g/kg-km.
                     emission result.   mile.
Eff...............  efficiency.......
F.................  adjustment factor
F.................  force............  pound force or     lbf or N....................  kg[middot]m[middot]s-
                                        newton.                                          \2\.
fn................  angular speed      revolutions per    r/min.......................  [pi][middot]30[middot]s-
                     (shaft).           minute.                                          \1\.
G.................  road grade.......  percent..........  %...........................  10-\2\.
g.................  gravitational      meters per second  m/s\2\......................  m[middot]s-\2\.
                     acceleration.      squared.
h.................  elevation or       meters...........  m...........................  m.
                     height.
i.................  indexing variable
ka................  drive axle ratio.  .................  ............................  1.
kd................  transmission gear
                     ratio.
ktopgear..........  highest available
                     transmission
                     gear.
L.................  load over axle...  pound force or     lbf or N....................  kg[middot]m[middot]s-
                                        newton.                                          \2\.
m.................  mass.............  pound mass or      lbm or kg...................  kg.
                                        kilogram.
M.................  molar mass.......  gram per mole....  g/mol.......................  10-
                                                                                         \3\[middot]kg[middot]mo
                                                                                         l-\1\.
M.................  vehicle mass.....  kilogram.........  kg..........................  kg.
Me................  vehicle effective  kilogram.........  kg..........................  kg.
                     mass.
Mrotating.........  inertial mass of   kilogram.........  kg..........................  kg.
                     rotating
                     components.
N.................  total number in
                     series.
n.................  number of tires..
n.................  amount of          mole per second..  mol/s.......................  mol[middot]s-\1\.
                     substance rate.
P.................  power............  kilowatt.........  kW..........................  10\3\[middot]m\2\[middot
                                                                                         ]kg[middot]s-\3\.
p.................  pressure.........  pascal...........  Pa..........................  kg[middot]m-\1\[middot]s-
                                                                                         \2\.
[rho].............  mass density.....  kilogram per       kg/m\3\.....................  kg[middot]m-\3\.
                                        cubic meter.
PL................  payload..........  tons.............  ton.........................  kg.
[phis]............  direction........  degrees..........  [deg].......................  [deg].
[psi].............  direction........  degrees..........  [deg].......................  [deg].
r.................  tire radius......  meter............  m...........................  m.
r\2\..............  coefficient of
                     determination.
Re ..............  Reynolds number..
SEE...............  standard error of
                     the estimate.
[sigma]...........  standard
                     deviation.
TRPM..............  tire revolutions   revolutions per    r/mi........................
                     per mile.          mile.
TRRL..............  tire rolling       newton per         N/kN........................  10-\3\.
                     resistance level.  kilonewton.
T.................  absolute           kelvin...........  K...........................  K.
                     temperature.
T.................  Celsius            degree Celsius...  [deg]C......................  K-273.15.
                     temperature.
T.................  torque (moment of  newton meter.....  N[middot]m..................  m\2\[middot]kg[middot]s-
                     force).                                                             \2\.
t.................  time.............  hour or second...  hr or s.....................  s.
[Delta]t..........  time interval,     second...........  s...........................  s.
                     period, 1/
                     frequency.
UF................  utility factor...
v.................  speed............  miles per hour or  mi/hr or m/s................  m[middot]s-\1\.
                                        meters per
                                        second.
w.................  weighting factor.
w.................  wind speed.......  miles per hour...  mi/hr.......................  m[middot]s-\1\.
W.................  work.............  kilowatt-hour....  kW[middot]hr................  3.6[middot]m\2\[middot]k
                                                                                         g[middot]s-\1\.
wC................  carbon mass        gram per gram....  g/g.........................  1.
                     fraction.
WR................  weight reduction.  pound mass.......  lbm.........................  kg.
x.................  amount of          mole per mole....  mol/mol.....................  1.
                     substance mole
                     fraction.
----------------------------------------------------------------------------------------------------------------

* * * * *
    (d) Subscripts. This part uses the following subscripts for 
modifying quantity symbols:

         Table 4 to Paragraph (d) of Sec.   1037.805--Subscripts
------------------------------------------------------------------------
               Subscript                             Meaning
------------------------------------------------------------------------
6..........................  6[deg] yaw angle
                                          sweep.
A......................................  A speed.
air....................................  air.
aero...................................  aerodynamic.

[[Page 4656]]

 
alt....................................  alternative.
act....................................  actual or measured condition.
air....................................  air.
axle...................................  axle.
B......................................  B speed.
brake..................................  brake.
C......................................  C speed.
Ccombdry...............................  carbon from fuel per mole of
                                          dry exhaust.
CD.....................................  charge-depleting.
circuit................................  circuit.
CO2DEF.................................  CO2 resulting from diesel
                                          exhaust fluid decomposition.
CO2PTO.................................  CO2 emissions for PTO cycle.
coastdown..............................  coastdown.
comp...................................  composite.
CS.....................................  charge-sustaining.
cycle..................................  test cycle.
drive..................................  drive axle.
drive-idle.............................  idle with the transmission in
                                          drive.
driver.................................  driver.
dyno...................................  dynamometer.
effective..............................  effective.
end....................................  end.
eng....................................  engine.
event..................................  event.
fuel...................................  fuel.
full...................................  full.
grade..................................  grade.
H2Oexhaustdry..........................  H2O in exhaust per mole of
                                          exhaust.
hi.....................................  high.
i......................................  an individual of a series.
idle...................................  idle.
in.....................................  inlet.
inc....................................  increment.
lo.....................................  low.
loss...................................  loss.
max....................................  maximum.
meas...................................  measured quantity.
med....................................  median.
min....................................  minimum.
moving.................................  moving.
out....................................  outlet.
P......................................  power.
pair...................................  pair of speed segments.
parked-idle............................  idle with the transmission in
                                          park.
partial................................  partial.
ploss..................................  power loss.
plug-in................................  plug-in hybrid electric
                                          vehicle.
powertrain.............................  powertrain.
PTO....................................  power take-off.
rated..................................  rated speed.
record.................................  record.
ref....................................  reference quantity.
RL.....................................  road load.
rotating...............................  rotating.
seg....................................  segment.
speed..................................  speed.
spin...................................  axle spin loss.
start..................................  start.
steer..................................  steer axle.
t......................................  tire.
test...................................  test.
th.....................................  theoretical.
total..................................  total.
trac...................................  traction.
trac10.................................  traction force at 10 mi/hr.
trailer................................  trailer axle.
transient..............................  transient.
TRR....................................  tire rolling resistance.
UF.....................................  utility factor.
urea...................................  urea.
veh....................................  vehicle.
w......................................  wind.

[[Page 4657]]

 
wa.....................................  wind average.
yaw....................................  yaw angle.
ys.....................................  yaw sweep.
zero...................................  zero quantity.
------------------------------------------------------------------------

    (e) Other acronyms and abbreviations. This part uses the following 
additional abbreviations and acronyms:

     Table 5 to Paragraph (e) of Sec.   1037.805--Other Acronyms and
                              Abbreviations
------------------------------------------------------------------------
                Acronym                              Meaning
------------------------------------------------------------------------
ABT....................................  averaging, banking, and
                                          trading.
AECD...................................  auxiliary emission control
                                          device.
AES....................................  automatic engine shutdown.
APU....................................  auxiliary power unit.
CD.....................................  charge-depleting.
CFD....................................  computational fluid dynamics.
CFR....................................  Code of Federal Regulations.
CITT...................................  curb idle transmission torque.
CS.....................................  charge-sustaining.
DOT....................................  Department of Transportation.
ECM....................................  electronic control module.
EPA....................................  Environmental Protection
                                          Agency.
FE.....................................  fuel economy.
FEL....................................  Family Emission Limit.
FTP....................................  Federal Test Procedure.
GAWR...................................  gross axle weight rating.
GCWR...................................  gross combination weight
                                          rating.
GEM....................................  greenhouse gas emission model.
GVWR...................................  gross vehicle weight rating.
Heavy HDE..............................  heavy heavy-duty engine (see 40
                                          CFR 1036.140).
Heavy HDV..............................  heavy heavy-duty vehicle (see
                                          Sec.   1037.140).
HVAC...................................  heating, ventilating, and air
                                          conditioning.
ISO....................................  International Organization for
                                          Standardization.
Light HDE..............................  light heavy-duty engine (see 40
                                          CFR 1036.140).
Light HDV..............................  light heavy-duty vehicle (see
                                          Sec.   1037.140).
LLC....................................  Low Load Cycle.
Medium HDE.............................  medium heavy-duty engine (see
                                          40 CFR 1036.140).
Medium HDV.............................  medium heavy-duty vehicle (see
                                          Sec.   1037.140).
NARA...................................  National Archives and Records
                                          Administration.
NHTSA..................................  National Highway Transportation
                                          Safety Administration.
PHEV...................................  plug-in hybrid electric
                                          vehicle.
PTO....................................  power take-off.
RESS...................................  rechargeable energy storage
                                          system.
SAE....................................  SAE International.
SEE....................................  standard error of the estimate.
SET....................................  Supplemental Emission Test.
SKU....................................  stock-keeping unit.
Spark-ignition HDE.....................  spark-ignition heavy-duty
                                          engine (see 40 CFR 1036.140).
TRPM...................................  tire revolutions per mile.
TRRL...................................  tire rolling resistance level.
U.S.C..................................  United States Code.
VSL....................................  vehicle speed limiter.
------------------------------------------------------------------------

    (f) Constants. This part uses the following constants:

         Table 6 to Paragraph (f) of Sec.   1037.805--Constants
------------------------------------------------------------------------
       Symbol                 Quantity                    Value
------------------------------------------------------------------------
g...................  gravitational constant..  9.80665 m[middot]-\2\.
R...................  specific gas constant...  287.058 J/(kg[middot]K).
------------------------------------------------------------------------

    (g) Prefixes. This part uses the following prefixes to define a 
quantity:

          Table 7 to Paragraph (g) of Sec.   1037.805--Prefixes
------------------------------------------------------------------------
             Symbol                    Quantity              Value
------------------------------------------------------------------------
[micro].........................  micro.............  10-\6\
m...............................  milli.............  10-\3\
c...............................  centi.............  10-\2\
k...............................  kilo..............  10\3\
M...............................  mega..............  10\6\
------------------------------------------------------------------------

[[Page 4658]]

0
136. Revise Sec.  1037.810 to read as follows:

Sec.  1037.810  Incorporation by reference.

    Certain material is incorporated by reference into this part with 
the approval of the Director of the Federal Register under 5 U.S.C. 
552(a) and 1 CFR part 51. To enforce any edition other than that 
specified in this section, EPA must publish a document in the Federal 
Register and the material must be available to the public. All approved 
incorporation by reference (IBR) material is available for inspection 
at EPA and at the National Archives and Records Administration (NARA). 
Contact EPA at: U.S. EPA, Air and Radiation Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004; 
www.epa.gov/dockets; (202) 202-1744. For information on inspecting this 
material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be 
obtained from the following sources:
    (a) International Organization for Standardization, Case Postale 
56, CH-1211 Geneva 20, Switzerland; (41) 22749 0111; www.iso.org; or 
[email protected].
    (1) ISO 28580:2009(E) ``Passenger car, truck and bus tyres--Methods 
of measuring rolling resistance--Single point test and correlation of 
measurement results'', First Edition, July 1, 2009, (``ISO 28580''); 
IBR approved for Sec.  1037.520(c).
    (2) [Reserved]
    (b) National Institute of Standards and Technology (NIST), 100 
Bureau Drive, Stop 1070, Gaithersburg, MD 20899-1070; (301) 975-6478; 
www.nist.gov.
    (1) NIST Special Publication 811, 2008 Edition, Guide for the Use 
of the International System of Units (SI), Physics Laboratory, March 
2008; IBR approved for Sec.  1037.805.
    (2) [Reserved]
    (c) SAE International, 400 Commonwealth Dr., Warrendale, PA 15096-
0001, (877) 606-7323 (U.S. and Canada) or (724) 776-4970 (outside the 
U.S. and Canada), www.sae.org.
    (1) SAE J1025 AUG2012, Test Procedures for Measuring Truck Tire 
Revolutions Per Kilometer/Mile, Stabilized August 2012, (``SAE 
J1025''); IBR approved for Sec.  1037.520(c).
    (2) SAE J1252 JUL2012, SAE Wind Tunnel Test Procedure for Trucks 
and Buses, Revised July 2012, (``SAE J1252''); IBR approved for 
Sec. Sec.  1037.525(b); 1037.530(a).
    (3) SAE J1263 MAR2010, Road Load Measurement and Dynamometer 
Simulation Using Coastdown Techniques, Revised March 2010, (``SAE 
J1263''); IBR approved for Sec. Sec.  1037.528 introductory text, (a), 
(b), (c), (e), and (h); 1037.665(a).
    (4) SAE J1594 JUL2010, Vehicle Aerodynamics Terminology, Revised 
July 2010, (``SAE J1594''); IBR approved for Sec.  1037.530(d).
    (5) SAE J2071 REV. JUN94, Aerodynamic Testing of Road Vehicles--
Open Throat Wind Tunnel Adjustment, Revised June 1994, (``SAE J2071''); 
IBR approved for Sec.  1037.530(b).
    (6) SAE J2263 MAY2020, (R) Road Load Measurement Using Onboard 
Anemometry and Coastdown Techniques, Revised May 2020, (``SAE J2263''); 
IBR approved for Sec. Sec.  1037.528 introductory text, (a), (b), (d), 
and (f); 1037.665(a).
    (7) SAE J2343 JUL2008, Recommended Practice for LNG Medium and 
Heavy-Duty Powered Vehicles, Revised July 2008, (``SAE J2343''); IBR 
approved for Sec.  1037.103(e).
    (8) SAE J2452 ISSUED JUN1999, Stepwise Coastdown Methodology for 
Measuring Tire Rolling Resistance, Issued June 1999, (``SAE J2452''); 
IBR approved for Sec.  1037.528(h).
    (9) SAE J2841 MAR2009, Utility Factor Definitions for Plug-In 
Hybrid Electric Vehicles Using 2001 U.S. DOT National Household Travel 
Survey Data, Issued March 2009, (``SAE J2841''); IBR approved for Sec.  
1037.550(a).
    (10) SAE J2966 SEP2013, Guidelines for Aerodynamic Assessment of 
Medium and Heavy Commercial Ground Vehicles Using Computational Fluid 
Dynamics, Issued September 2013, (``SAE J2966''); IBR approved for 
Sec.  1037.532(a).
    (d) U.S. EPA, Office of Air and Radiation, 2565 Plymouth Road, Ann 
Arbor, MI 48105; www.epa.gov.
    (1) Greenhouse gas Emissions Model (GEM), Version 2.0.1, September 
2012 (``GEM version 2.0.1''); IBR approved for Sec.  1037.520.
    (2) Greenhouse gas Emissions Model (GEM) Phase 2, Version 3.0, July 
2016 (``GEM Phase 2, Version 3.0''); IBR approved for Sec.  
1037.150(bb).
    (3) Greenhouse gas Emissions Model (GEM) Phase 2, Version 3.5.1, 
November 2020 (``GEM Phase 2, Version 3.5.1''); IBR approved for Sec.  
1037.150(bb).
    (4) Greenhouse gas Emissions Model (GEM) Phase 2, Version 4.0, 
April 2022 (``GEM Phase 2, Version 4.0''); IBR approved for Sec. Sec.  
1037.150(bb); 1037.520; 1037.550(a).
    (5) GEM's MATLAB/Simulink Hardware-in-Loop model, Version 3.8, 
December 2020 (``GEM HIL model 3.8''); IBR approved for Sec.  
1037.150(bb).
    Note 1 to paragraph (d): The computer code for these models is 
available as noted in the introductory paragraph of this section. A 
working version of the software is also available for download at 
www.epa.gov/regulations-emissions-vehicles-and-engines/greenhouse-gas-emissions-model-gem-medium-and-heavy-duty.

0
137. Revise Sec.  1037.815 to read as follows:

Sec.  1037.815  Confidential information.

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

0
138. Amend Sec.  1037.825 by revising paragraph (e)(1)(i) to read as 
follows:

Sec.  1037.825  Reporting and recordkeeping requirements.

* * * * *
    (e) * * *
    (1) * * *
    (i) In Sec.  1037.150 we include various reporting and 
recordkeeping requirements related to interim provisions.
* * * * *

Appendix I to Part 1037 [Redesignated as Appendix A to Part 1037]

Appendix II to Part 1037 [Redesignated as Appendix B to Part 1037]

Appendix III to Part 1037 [Redesignated as Appendix C to Part 1037]

Appendix IV to Part 1037 [Redesignated as Appendix D to Part 1037]

Appendix V to Part 1037 [Redesignated as Appendix E to Part 1037]

0
139. Redesignate appendices to part 1037 as follows:

------------------------------------------------------------------------
            Old appendix                         New appendix
------------------------------------------------------------------------
appendix I to part 1037              appendix A to part 1037.
appendix II to part 1037             appendix B to part 1037.
appendix III to part 1037            appendix C to part 1037.
appendix IV to part 1037             appendix D to part 1037.
appendix V to part 1037              appendix E to part 1037.
------------------------------------------------------------------------

PART 1039--CONTROL OF EMISSIONS FROM NEW AND IN-USE NONROAD 
COMPRESSION-IGNITION ENGINES

0
140. The authority citation for part 1039 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
141. Amend Sec.  1039.105 by revising the section heading and 
paragraphs (a) introductory text and (b) introductory text to read as 
follows:

[[Page 4659]]

Sec.  1039.105  What smoke opacity standards must my engines meet?

    (a) The smoke opacity standards in this section apply to all 
engines subject to emission standards under this part, except for the 
following engines:
* * * * *
    (b) Measure smoke opacity as specified in Sec.  1039.501(c). Smoke 
opacity from your engines may not exceed the following standards:
* * * * *

0
142. Amend Sec.  1039.115 by revising paragraphs (e) and (f) to read as 
follows:

Sec.  1039.115  What other requirements apply?

* * * * *
    (e) Adjustable parameters. Engines that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range. We may require that you set adjustable 
parameters to any specification within the practically adjustable range 
during any testing, including certification testing, selective 
enforcement auditing, or in-use testing. General provisions for 
adjustable parameters apply as specified in 40 CFR 1068.50.
    (f) Prohibited controls. (1) General provisions. You may not design 
your engines with emission control devices, systems, or elements of 
design that cause or contribute to an unreasonable risk to public 
health, welfare, or safety while operating. For example, an engine may 
not emit a noxious or toxic substance it would otherwise not emit that 
contributes to such an unreasonable risk.
    (2) Vanadium sublimation in SCR catalysts. For engines equipped 
with vanadium-based SCR catalysts, you must design the engine and its 
emission controls to prevent vanadium sublimation and protect the 
catalyst from high temperatures. We will evaluate your engine design 
based on the following information that you must include in your 
application for certification:
    (i) Identify the threshold temperature for vanadium sublimation for 
your specified SCR catalyst formulation as described in 40 CFR 
1065.1113 through 1065.1121.
    (ii) Describe how you designed your engine to prevent catalyst 
inlet temperatures from exceeding the temperature you identify in 
paragraph (f)(2)(i) of this section, including consideration of engine 
wear through the useful life. Also describe your design for catalyst 
protection in case catalyst temperatures exceed the specified 
temperature. In your description, include how you considered elevated 
catalyst temperature resulting from sustained high-load engine 
operation, catalyst exotherms, DPF regeneration, and component failure 
resulting in unburned fuel in the exhaust stream.
* * * * *

0
143. Amend Sec.  1039.205 by revising paragraph (s) to read as follows:

Sec.  1039.205  What must I include in my application?

* * * * *
    (s) Describe all adjustable operating parameters (see Sec.  
1039.115(e)), including production tolerances. For any operating 
parameters that do not qualify as adjustable parameters, include a 
description supporting your conclusion (see 40 CFR 1068.50(c)). Include 
the following in your description of each adjustable parameter:
    (1) For practically adjustable parameters, include the nominal or 
recommended setting, the intended practically adjustable range, and the 
limits or stops used to limit adjustable ranges. State that the limits, 
stops, or other means of inhibiting adjustment are effective in 
preventing adjustment of parameters on in-use engines to settings 
outside your intended practically adjustable ranges.
    (2) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustments on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
* * * * *

0
144. Amend Sec.  1039.245 by adding paragraph (e) to read as follows:

Sec.  1039.245  How do I determine deterioration factors from exhaust 
durability testing?

* * * * *
    (e) You may alternatively determine and verify deterioration 
factors based on bench-aged aftertreatment as described in 40 CFR 
1036.245 and 1036.246, with the following exceptions:
    (1) The minimum required aging for engines as specified in 40 CFR 
1036.245(c)(2) is 1,500 hours. Operate the engine for service 
accumulation using the same sequence of duty cycles that would apply 
for determining a deterioration factor under paragraph (c) of this 
section.
    (2) Use good engineering judgment to perform verification testing 
using the procedures of Sec.  1039.515 rather than 40 CFR 1036.555. For 
PEMS testing, measure emissions as the equipment goes through its 
normal operation over the course of the day (or shift-day).
    (3) Apply infrequent regeneration adjustment factors as specified 
in Sec.  1039.525 rather than 40 CFR 1036.580.

0
145. Amend Sec.  1039.501 by revising paragraph (c) to read as follows:

Sec.  1039.501  How do I run a valid emission test?

* * * * *
    (c) Measure smoke opacity using the procedures in 40 CFR part 1065, 
subpart L, for evaluating whether engines meet the smoke opacity 
standards in Sec.  1039.105, except that you may test two-cylinder 
engines with an exhaust muffler like those installed on in-use engines.
* * * * *

0
146. Revise Sec.  1039.655 to read as follows:

Sec.  1039.655  What special provisions apply to engines sold in 
American Samoa or the Commonwealth of the Northern Mariana Islands?

    (a) The prohibitions in 40 CFR 1068.101(a)(1) do not apply to 
diesel-fueled engines that are intended for use and will be used in 
American Samoa or the Commonwealth of the Northern Mariana Islands, 
subject to the following conditions:
    (1) The engine meets the latest applicable emission standards in 
appendix I of this part.
    (2) You meet all the requirements of 40 CFR 1068.265.
    (b) If you introduce an engine into U.S. commerce under this 
section, you must meet the labeling requirements in Sec.  1039.135, but 
add the following statement instead of the compliance statement in 
Sec.  1039.135(c)(12):
    THIS ENGINE DOES NOT COMPLY WITH U.S. EPA TIER 4 EMISSION 
REQUIREMENTS. IMPORTING THIS ENGINE INTO THE UNITED STATES OR ANY 
TERRITORY OF THE UNITED STATES EXCEPT AMERICAN SAMOA OR THE 
COMMONWEALTH OF THE NORTHERN MARIANA ISLANDS MAY BE A VIOLATION OF 
FEDERAL LAW SUBJECT TO CIVIL PENALTY.
    (c) Introducing into commerce an engine exempted under this section 
in any state or territory of the United States other than American 
Samoa or the Commonwealth of the Northern Mariana Islands, throughout 
its lifetime, violates the prohibitions in 40 CFR 1068.101(a)(1), 
unless it is exempt under a different provision.
    (d) The exemption provisions in this section also applied for 
engines that were introduced into commerce in Guam before January 1, 
2024 if they

[[Page 4660]]

would otherwise have been subject to Tier 4 standards.

0
147. Amend Sec.  1039.801 by revising the definitions of ``Adjustable 
parameter'', ``Critical emission-related component'', and ``Designated 
Compliance Officer'' to read as follows:

Sec.  1039.801  What definitions apply to this part?

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *
    Critical emission-related component has the meaning given in 40 CFR 
1068.30.
* * * * *
    Designated Compliance Officer means the Director, Diesel Engine 
Compliance Center, U.S. Environmental Protection Agency, 2000 
Traverwood Drive, Ann Arbor, MI 48105; [email protected]; 
www.epa.gov/ve-certification
* * * * *

0
148. Amend appendix I of part 1039 by revising paragraphs (a) and (b) 
to read as follows:

Appendix I to Part 1039--Summary of Previous Emission Standards

* * * * *
    (a) Tier 1 standards apply as summarized in the following table:

                                                    Table 1 to Appendix I--Tier 1 Emission Standards
                                                                        [g/kW-hr]
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                          Starting model
                    Rated power (kW)                           year             NOX             HC          NOX + NMHC          CO              PM
--------------------------------------------------------------------------------------------------------------------------------------------------------
kW< 8...................................................            2000  ..............  ..............            10.5             8.0             1.0
8 <= kW < 19............................................            2000  ..............  ..............             9.5             6.6            0.80
19 <= kW < 37...........................................            1999  ..............  ..............             9.5             5.5            0.80
37 <= kW < 75...........................................            1998             9.2  ..............  ..............  ..............  ..............
75 <= kW < 130..........................................            1997             9.2  ..............  ..............  ..............  ..............
130 <= kW <= 560........................................            1996             9.2             1.3  ..............            11.4            0.54
kW > 560................................................            2000             9.2             1.3  ..............            11.4            0.54
--------------------------------------------------------------------------------------------------------------------------------------------------------

    (b) Tier 2 standards apply as summarized in the following table:

                                Table 2 to Appendix I--Tier 2 Emission Standards
                                                    [g/kW-hr]
----------------------------------------------------------------------------------------------------------------
                                                  Starting model
                Rated power (kW)                       year         NOX + NMHC          CO              PM
----------------------------------------------------------------------------------------------------------------
kW< 8...........................................            2005             7.5             8.0            0.80
8 <= kW < 19....................................            2005             7.5             6.6            0.80
19 <= kW < 37...................................            2004             7.5             5.5            0.60
37 <= kW < 75...................................            2004             7.5             5.0            0.40
75 <= kW < 130..................................            2003             6.6             5.0            0.30
130 <= kW < 225.................................            2003             6.6             3.5            0.20
225 <= kW < 450.................................            2001             6.4             3.5            0.20
450 <= kW <= 560................................            2002             6.4             3.5            0.20
kW > 560........................................            2006             6.4             3.5            0.20
----------------------------------------------------------------------------------------------------------------

* * * * *

PART 1042--CONTROL OF EMISSIONS FROM NEW AND IN-USE MARINE 
COMPRESSION-IGNITION ENGINES AND VESSELS

0
149. The authority citation for part 1042 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart B [Amended]

0
150. Amend Sec.  1042.110 by revising paragraph (a)(1) to read as 
follows:

Sec.  1042.110  Recording reductant use and other diagnostic functions.

    (a) * * *
    (1) The diagnostic system must monitor reductant supply and alert 
operators to the need to restore the reductant supply, or to replace 
the reductant if it does not meet your concentration specifications. 
Unless we approve other alerts, use a warning lamp and an audible 
alarm. You do not need to separately monitor reductant quality if your 
system uses input from an exhaust NOX sensor (or other 
sensor) to alert operators when reductant quality is inadequate. 
However, tank level or DEF flow must be monitored in all cases.
* * * * *

0
151. Amend Sec.  1042.115 by revising paragraphs (d) introductory text 
and (e) to read as follows:

Sec.  1042.115  Other requirements.

* * * * *
    (d) Adjustable parameters. General provisions for adjustable 
parameters apply as specified in 40 CFR 1068.50. The following 
additional category-specific provisions apply:
* * * * *
    (e) Prohibited controls. (1) General provisions. You may not design 
your engines with emission control devices, systems, or elements of 
design that cause or contribute to an unreasonable risk to public 
health, welfare, or safety while operating. For example, an engine may 
not emit a noxious or toxic substance it would otherwise not emit that 
contributes to such an unreasonable risk.
    (2) Vanadium sublimation in SCR catalysts. For engines equipped 
with vanadium-based SCR catalysts, you must design the engine and its 
emission controls to prevent vanadium sublimation and protect the 
catalyst from high temperatures. We will evaluate your engine design 
based on

[[Page 4661]]

the following information that you must include in your application for 
certification:
    (i) Identify the threshold temperature for vanadium sublimation for 
your specified SCR catalyst formulation as described in 40 CFR 
1065.1113 through 1065.1121.
    (ii) Describe how you designed your engine to prevent catalyst 
inlet temperatures from exceeding the temperature you identify in 
paragraph (e)(2)(i) of this section, including consideration of engine 
wear through the useful life. Also describe your design for catalyst 
protection in case catalyst temperatures exceed the specified 
temperature. In your description, include how you considered elevated 
catalyst temperature resulting from sustained high-load engine 
operation, catalyst exotherms, DPF regeneration, and component failure 
resulting in unburned fuel in the exhaust stream.
* * * * *

0
152. Amend Sec.  1042.145 by adding paragraph (h) to read as follows:

Sec.  1042.145  Interim provisions.

* * * * *
    (h) Expanded production-line testing. Production-line testing 
requirements for Category 1 engine families with a projected U.S.-
directed production volume below 100 engines and for all families 
certified by small-volume engine manufacturers start to apply in model 
year 2024. All manufacturers must test no more than four engine 
families in a single model year, and small-volume engine manufacturers 
must test no more than two engine families in a single model year.
* * * * *

0
153. Amend Sec.  1042.205 by revising paragraphs (c) and (s) to read as 
follows:

Sec.  1042.205  Application requirements.

* * * * *
    (c) If your engines are equipped with an engine diagnostic system 
as required under Sec.  1042.110, explain how it works, describing 
especially the engine conditions (with the corresponding diagnostic 
trouble codes) that cause the warning lamp to go on. Also identify the 
communication protocol (SAE J1939, SAE J1979, etc.).
* * * * *
    (s) Describe all adjustable operating parameters (see Sec.  
1042.115(d)), including production tolerances. For any operating 
parameters that do not qualify as adjustable parameters, include a 
description supporting your conclusion (see 40 CFR 1068.50(c)). Include 
the following in your description of each adjustable parameter:
    (1) For practically adjustable parameters, include the nominal or 
recommended setting, the intended practically adjustable range, and the 
limits or stops used to establish adjustable ranges.
    (i) For Category 1 engines, state that the limits, stops, or other 
means of inhibiting mechanical adjustment are effective in preventing 
adjustment of parameters on in-use engines to settings outside your 
intended practically adjustable ranges and provide information to 
support this statement.
    (ii) For Category 2 and Category 3 engines, propose a range of 
mechanical adjustment for each adjustable parameter, as described in 
Sec.  1042.115(d). State that the limits, stops, or other means of 
inhibiting mechanical adjustment are effective in preventing adjustment 
of parameters on in-use engines to settings outside your proposed 
adjustable ranges and provide information to support this statement.
    (2) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustments on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
* * * * *

0
154. Amend Sec.  1042.245 by adding paragraph (e) to read as follows:

Sec.  1042.245  Deterioration factors.

* * * * *
    (e) You may alternatively determine and verify deterioration 
factors based on bench-aged aftertreatment as described in 40 CFR 
1036.245 and 1036.246, with the following exceptions:
    (1) The minimum required aging as specified in 40 CFR 
1036.245(c)(2) is 1,500 hours for Category 1 engines and 3,000 hours 
for Category 2 engines. Operate the engine for service accumulation 
using the same sequence of duty cycles that would apply for determining 
a deterioration factor under paragraph (c) of this section.
    (2) Use good engineering judgment to perform verification testing 
using the procedures of Sec.  1042.515 rather than 40 CFR 1036.555. For 
PEMS testing, measure emissions as the vessel goes through its normal 
operation over the course of the day (or shift-day).
    (3) Apply infrequent regeneration adjustment factors as specified 
in Sec.  1042.525 rather than 40 CFR 1036.580.

0
155. Revise Sec.  1042.301 to read as follows:

Sec.  1042.301  General provisions.

    (a) If you produce freshly manufactured marine engines that are 
subject to the requirements of this part, you must test them as 
described in this subpart.
    (b) We may suspend or revoke your certificate of conformity for 
certain engine families if your production-line engines do not meet the 
requirements of this part or you do not fulfill your obligations under 
this subpart (see Sec. Sec.  1042.325 and 1042.340). Similarly, we may 
deny applications for certification for the upcoming model year if you 
do not fulfill your obligations under this subpart (see Sec.  
1042.255(c)(1)).
    (c) Other regulatory provisions authorize us to suspend, revoke, or 
void your certificate of conformity, or order recalls for engine 
families, without regard to whether they have passed production-line 
testing requirements. The requirements of this subpart do not affect 
our ability to do selective enforcement audits, as described in 40 CFR 
part 1068. Individual engines in families that pass production-line 
testing requirements must also conform to all applicable regulations of 
this part and 40 CFR part 1068.
    (d) You may ask to use another alternate program or measurement 
method for testing production-line engines. In your request, you must 
show us that the alternate program gives equal assurance that your 
engines meet the requirements of this part. We may waive some or all of 
this subpart's requirements if we approve your alternate program.
    (e) If you certify a Category 1 or Category 2 engine family with 
carryover emission data, as described in Sec.  1042.235(d), you may 
omit production-line testing if you fulfilled your testing requirements 
with a related engine family in an earlier year, except as follows:
    (1) We may require that you perform additional production-line 
testing under this subpart in any model year for cause, such as if you 
file a defect report related to the engine family or if you amend your 
application for certification in any of the following ways:
    (i) You designate a different supplier or change technical 
specifications for any critical emission-related components.
    (ii) You add a new or modified engine configuration such that the 
test data from the original emission-data engine do not clearly 
continue to serve as worst-case testing for certification.
    (iii) You change your family emission limit without submitting new 
emission data.

[[Page 4662]]

    (2) If you certify an engine family with carryover emission data 
with no production-line testing for more than five model years, we may 
require that you perform production-line testing again for one of those 
later model years unless you demonstrate that none of the circumstances 
identified in paragraph (e)(1) of this section apply for the engine 
family.
    (f) We may ask you to make a reasonable number of production-line 
engines available for a reasonable time so we can test or inspect them 
for compliance with the requirements of this part. For Category 3 
engines, you are not required to deliver engines to us, but we may 
inspect and test your engines at any facility at which they are 
assembled or installed in vessels.

0
156. Amend Sec.  1042.302 by revising the introductory text to read as 
follows:

Sec.  1042.302  Applicability of this subpart for Category 3 engines.

    If you produce Tier 3 or later Category 3 engines that are subject 
to the requirements of this part, you must test them as described in 
this subpart, except as specified in this section.
* * * * *

0
157. Amend Sec.  1042.305 by revising paragraph (a) to read as follows:

Sec.  1042.305  Preparing and testing production-line engines.

* * * * *
    (a) Test procedures. Test your production-line engines using the 
applicable testing procedures in subpart F of this part to show you 
meet the duty-cycle emission standards in subpart B of this part. For 
Category 1 and Category 2 engines, the not-to-exceed standards apply 
for this testing of Category 1 and Category 2 engines, but you need not 
do additional testing to show that production-line engines meet the 
not-to-exceed standards. The mode cap standards apply for testing 
Category 3 engines subject to Tier 3 standards (or for engines subject 
to the Annex VI Tier III NOx standards under Sec.  1042.650(d)).
* * * * *

0
158. Revise Sec.  1042.310 to read as follows:

Sec.  1042.310  Engine selection for Category 1 and Category 2 engines.

    (a) For Category 1 and Category 2 engine families, the minimum 
sample size is one engine. You may ask us to approve treating 
commercial and recreational engines as being from the same engine 
family for purposes of production-line testing if you certify them 
using the same emission-data engine.
    (b) Select engines for testing as follows:
    (1) For Category 1 engines, randomly select one engine within the 
first 60 days of the start of production for each engine family.
    (2) For Category 2 engines, randomly select one engine within 60 
days after you produce the fifth engine from an engine family (or from 
successive families that are related based on your use of carryover 
data under Sec.  1042.230(d)).
    (3) If you do not produce an engine from the engine family in the 
specified time frame, test the next engine you produce.
    (4) Test engines promptly after selecting them. You may 
preferentially select and test engines earlier than we specify.
    (5) You meet the requirement to randomly select engines under this 
section if you assemble the engine in a way that fully represents your 
normal production and quality procedures.
    (c) For each engine that fails to meet emission standards, select 
two engines from the same engine family from the next fifteen engines 
produced or within seven days, whichever is later. If you do not 
produce fifteen additional engines within 90 days, select two 
additional engines within 90 days or as soon as practicable. Test 
engines promptly after selecting them. If an engine fails to meet 
emission standards for any pollutant, count it as a failing engine 
under this paragraph (c).
    (d) Continue testing until one of the following things happens:
    (1) You test the number of engines required under paragraphs (b) 
and (c) of this section. For example, if the initial engine fails and 
then two engines pass, testing is complete for that engine family.
    (2) The engine family does not comply according to Sec.  1042.315 
or you choose to declare that the engine family does not comply with 
the requirements of this subpart.
    (e) You may elect to test more randomly chosen engines than we 
require under this section.

0
159. Amend Sec.  1042.315 by revising paragraphs (a)(1) and (b) to read 
as follows:

Sec.  1042.315  Determining compliance.

* * * * *
    (a) * * *
    (1) Initial and final test results. Calculate and round the test 
results for each engine. If you do multiple tests on an engine in a 
given configuration (without modifying the engine), calculate the 
initial results for each test, then add all the test results together 
and divide by the number of tests. Round this final calculated value 
for the final test results on that engine. Include the Green Engine 
Factor to determine low-hour emission results, if applicable.
* * * * *
    (b) For Category 1 and Category 2 engines, if a production-line 
engine fails to meet emission standards and you test additional engines 
as described in Sec.  1042.310, calculate the average emission level 
for each pollutant for all the engines. If the calculated average 
emission level for any pollutant exceeds the applicable emission 
standard, the engine family fails the production-line testing 
requirements of this subpart. Tell us within ten working days if an 
engine fails. You may request to amend the application for 
certification to raise the FEL of the engine family as described in 
Sec.  1042.225(f).

0
160. Amend Sec.  1042.320 by revising paragraph (c) to read as follows:

Sec.  1042.320  What happens if one of my production-line engines fails 
to meet emission standards?

* * * * *
    (c) Use test data from a failing engine for the compliance 
demonstration under Sec.  1042.315 as follows:
    (1) Use the original, failing test results as described in Sec.  
1042.315, whether or not you modify the engine or destroy it. However, 
for catalyst-equipped engines, you may ask us to allow you to exclude 
an initial failed test if all the following are true:
    (i) The catalyst was in a green condition when tested initially.
    (ii) The engine met all emission standards when retested after 
degreening the catalyst.
    (iii) No additional emission-related maintenance or repair was 
performed between the initial failed test and the subsequent passing 
test.
    (2) Do not use test results from a modified engine as final test 
results under Sec.  1042.315, unless you change your production process 
for all engines to match the adjustments you made to the failing 
engine. If you change production processes and use the test results 
from a modified engine, count the modified engine as the next engine in 
the sequence, rather than averaging the results with the testing that 
occurred before modifying the engine.

0
161. Amend Sec.  1042.325 by revising paragraph (b) to read as follows:

Sec.  1042.325  What happens if an engine family fails the production-
line testing requirements?

* * * * *
    (b) We will tell you in writing if we suspend your certificate in 
whole or in

[[Page 4663]]

part. We will not suspend a certificate until at least 15 days after 
the engine family fails as described in Sec.  1042.315(b). The 
suspension is effective when you receive our notice.
* * * * *

0
162. Revise Sec.  1042.345 to read as follows:

Sec.  1042.345  Reporting.

    (a) Send us a test report within 45 days after you complete 
production-line testing for a Category 1 or Category 2 engine family, 
and within 45 days after you finish testing each Category 3 engine. We 
may approve a later submission for Category 3 engines if it allows you 
to combine test reports for multiple engines.
    (b) Include the following information in the report:
    (1) Describe any facility used to test production-line engines and 
state its location.
    (2) For Category 1 and Category 2 engines, describe how you 
randomly selected engines.
    (3) Describe each test engine, including the engine family's 
identification and the engine's model year, build date, model number, 
identification number, and number of hours of operation before testing. 
Also describe how you developed and applied the Green Engine Factor, if 
applicable.
    (4) Identify how you accumulated hours of operation on the engines 
and describe the procedure and schedule you used.
    (5) Provide the test number; the date, time and duration of 
testing; test procedure; all initial test results; final test results; 
and final deteriorated test results for all tests. Provide the emission 
results for all measured pollutants. Include information for both valid 
and invalid tests and the reason for any invalidation.
    (6) Describe completely and justify any nonroutine adjustment, 
modification, repair, preparation, maintenance, or test for the test 
engine if you did not report it separately under this subpart. Include 
the results of any emission measurements, regardless of the procedure 
or type of engine.
    (c) We may ask you to add information to your written report so we 
can determine whether your new engines conform with the requirements of 
this subpart. We may also ask you to send less information.
    (d) An authorized representative of your company must sign the 
following statement:
    We submit this report under sections 208 and 213 of the Clean Air 
Act. Our production-line testing conformed completely with the 
requirements of 40 CFR part 1042. We have not changed production 
processes or quality-control procedures for test engines in a way that 
might affect emission controls. All the information in this report is 
true and accurate to the best of my knowledge. I know of the penalties 
for violating the Clean Air Act and the regulations. (Authorized 
Company Representative)
    (e) Send electronic reports of production-line testing to the 
Designated Compliance Officer using an approved information format. If 
you want to use a different format, send us a written request with 
justification for a waiver. You may combine reports from multiple 
engines and engine families into a single report.
    (f) We will send copies of your reports to anyone from the public 
who asks for them. See Sec.  1042.915 for information on how we treat 
information you consider confidential.

0
163. Amend Sec.  1042.515 by revising paragraph (d) to read as follows:

Sec.  1042.515  Test procedures related to not-to-exceed standards.

* * * * *
    (d) Engine testing may occur at any conditions expected during 
normal operation but that are outside the conditions described in 
paragraph (c) of this section, as long as measured values are corrected 
to be equivalent to the nearest end of the specified range, using good 
engineering judgment. Correct NOX emissions for humidity as 
specified in 40 CFR part 1065, subpart G.
* * * * *

0
164. Amend Sec.  1042.615 by revising paragraph (g) introductory text 
to read as follows:

Sec.  1042.615  Replacement engine exemption.

* * * * *
    (g) In unusual circumstances, you may ask us to allow you to apply 
the replacement engine exemption of this section for repowering a 
steamship or a vessel that becomes a ``new vessel'' under Sec.  
1042.901 as a result of modifications, as follows:
* * * * *

0
165. Amend Sec.  1042.660 by revising paragraph (b) to read as follows:

Sec.  1042.660  Requirements for vessel manufacturers, owners, and 
operators.

* * * * *
    (b) For vessels equipped with SCR systems requiring the use of urea 
or other reductants, owners and operators must report to the Designated 
Compliance Officer within 30 days any operation of such vessels without 
the appropriate reductant. For each reportable incident, include the 
cause of the noncompliant operation, the remedy, and an estimate of the 
extent of operation without reductant. You must remedy the problem as 
soon as practicable to avoid violating the tampering prohibition in 40 
CFR 1068.101(b)(1). If the remedy is not complete within 30 days of the 
incident, notify the Designated Compliance Officer when the issue is 
resolved, along with any relevant additional information related to the 
repair. This reporting requirement applies for all engines on covered 
vessels even if the engines are certified to Annex VI standards instead 
of or in addition to EPA standards under this part. Failure to comply 
with the reporting requirements of this paragraph (b) is a violation of 
40 CFR 1068.101(a)(2). Note that operating such engines without 
reductant is a violation of 40 CFR 1068.101(b)(1).
* * * * *

0
166. Amend Sec.  1042.901 by revising the definitions of ``Adjustable 
parameter'', ``Category 1'', ``Category 2'', ``Critical emission-
related component'', and ``Designated Compliance Officer'' and removing 
the definition of ``Designated Enforcement Officer'' to read as 
follows:

Sec.  1042.901  Definitions.

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *
    Category 1 means relating to a marine engine with specific engine 
displacement below 7.0 liters per cylinder. See Sec.  1042.670 to 
determine equivalent per-cylinder displacement for nonreciprocating 
marine engines (such as gas turbine engines). Note that the maximum 
specific engine displacement for Category 1 engines subject to Tier 1 
and Tier 2 standards was 5.0 liters per cylinder.
    Category 2 means relating to a marine engine with a specific engine 
displacement at or above 7.0 liters per cylinder but less than 30.0 
liters per cylinder. See Sec.  1042.670 to determine equivalent per-
cylinder displacement for nonreciprocating marine engines (such as gas 
turbine engines). Note that the minimum specific engine displacement 
for Category 2 engines subject to Tier 1 and Tier 2 standards was 5.0 
liters per cylinder.
* * * * *

[[Page 4664]]

    Critical emission-related component has the meaning given in 40 CFR 
1068.30.
* * * * *
    Designated Compliance Officer means the Director, Diesel Engine 
Compliance Center, U.S. Environmental Protection Agency, 2000 
Traverwood Drive, Ann Arbor, MI 48105; [email protected]; 
www.epa.gov/ve-certification.
* * * * *

0
167. Amend appendix I to part 1042 by revising paragraph (a) to read as 
follows:

Appendix I to Part 1042--Summary of Previous Emission Standards

* * * * *
    (a) Engines below 37 kW. Tier 1 and Tier 2 standards for engines 
below 37 kW originally adopted under 40 CFR part 89 apply as 
follows:

                        Table 1 to Appendix I--Emission Standards for Engines Below 37 kW
                                                    [g/kW-hr]
----------------------------------------------------------------------------------------------------------------
        Rated power (kW)               Tier         Model year      NMHC + NOX          CO              PM
----------------------------------------------------------------------------------------------------------------
kW<8............................          Tier 1            2000            10.5             8.0             1.0
                                          Tier 2            2005             7.5             8.0            0.80
8<=k W<19.......................          Tier 1            2000             9.5             6.6            0.80
                                          Tier 2            2005             7.5             6.6            0.80
19<= kW<37......................          Tier 1            1999             9.5             5.5            0.80
                                          Tier 2            2004             7.5             5.5            0.60
----------------------------------------------------------------------------------------------------------------

* * * * *

PART 1043--CONTROL OF NOX, SOX, AND PM EMISSIONS FROM MARINE 
ENGINES AND VESSELS SUBJECT TO THE MARPOL PROTOCOL

0
168. The authority citation for part 1043 continues to read as follows:

    Authority: 33 U.S.C. 1901-1912.

0
169. Amend Sec.  1043.20 by removing the definition of ``Public 
vessels'' and adding a definition of ``Public vessel'' in alphabetical 
order to read as follows:

Sec.  1043.20  Definitions.

* * * * *
    Public vessel means a warship, naval auxiliary vessel, or other 
vessel owned or operated by a sovereign country when engaged in 
noncommercial service. Vessels with a national security exemption under 
40 CFR 1042.635 are deemed to be public vessels with respect to 
compliance with NOX-related requirements of this part when 
engaged in noncommercial service. Similarly, vessels with one or more 
installed engines that have a national security exemption under 40 CFR 
1090.605 are deemed to be public vessels with respect to compliance 
with fuel content requirements when engaged in noncommercial service.
* * * * *

0
170. Amend Sec.  1043.55 by revising paragraphs (a) and (b) to read as 
follows:

Sec.  1043.55  Applying equivalent controls instead of complying with 
fuel requirements.

* * * * *
    (a) The U.S. Coast Guard is the approving authority under APPS for 
such equivalent methods for U.S.-flagged vessels.
    (b) The provisions of this paragraph (b) apply for vessels equipped 
with controls certified by the U.S. Coast Guard or the Administration 
of a foreign-flag vessel to achieve emission levels equivalent to those 
achieved by the use of fuels meeting the applicable fuel sulfur limits 
of Regulation 14 of Annex VI. Fuels not meeting the applicable fuel 
sulfur limits of Regulation 14 of Annex VI may be used on such vessels 
consistent with the provisions of the IAPP certificate, APPS and Annex 
VI.
* * * * *

0
171. Amend Sec.  1043.95 by revising paragraph (b) to read as follows:

Sec.  1043.95  Great Lakes provisions.

* * * * *
    (b) The following exemption provisions apply for ships qualifying 
under paragraph (a) of this section:
    (1) The fuel-use requirements of this part do not apply through 
December 31, 2025, if we approved an exemption under this section 
before [60 days after the date of publication in the Federal Register] 
based on the use of replacement engines certified to applicable 
standards under 40 CFR part 1042 corresponding to the date the vessel 
entered dry dock for service. All other requirements under this part 
1043 continue to apply to exempted vessels, including requirements 
related to bunker delivery notes.
    (2) A marine diesel engine installed to repower a steamship may be 
certified to the Tier II NOX standard instead of the Tier 
III NOX standard pursuant to Regulation 13 of Annex VI.
* * * * *

PART 1045--CONTROL OF EMISSIONS FROM SPARK-IGNITION PROPULSION 
MARINE ENGINES AND VESSELS

0
172. The authority citation for part 1045 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
173. Amend Sec.  1045.115 by revising paragraphs (e) and (f) to read as 
follows:

Sec.  1045.115  What other requirements apply?

* * * * *
    (e) Adjustable parameters. Engines that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range. We may require that you set adjustable 
parameters to any specification within the practically adjustable range 
during any testing, including certification testing, production-line 
testing, or in-use testing. General provisions for adjustable 
parameters apply as specified in 40 CFR 1068.50.
    (f) Prohibited controls. You may not design your engines with 
emission control devices, systems, or elements of design that cause or 
contribute to an unreasonable risk to public health, welfare, or safety 
while operating. For example, an engine may not emit a noxious or toxic 
substance it would otherwise not emit that contributes to such an 
unreasonable risk.
* * * * *

0
174. Amend Sec.  1045.205 by revising paragraph (r) to read as follows:

Sec.  1045.205  What must I include in my application?

* * * * *
    (r) Describe all adjustable operating parameters (see Sec.  
1045.115(e)), including production tolerances. For any operating 
parameters that do not

[[Page 4665]]

qualify as adjustable parameters, include a description supporting your 
conclusion (see 40 CFR 1068.50(c)). Include the following in your 
description of each adjustable parameter:
    (1) For practically adjustable parameters, include the nominal or 
recommended setting, the intended practically adjustable range, and the 
limits or stops used to establish adjustable ranges. State that the 
limits, stops, or other means of inhibiting adjustment are effective in 
preventing adjustment of parameters on in-use engines to settings 
outside your intended practically adjustable ranges and provide 
information to support this statement.
    (2) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustments on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
* * * * *

0
175. Amend Sec.  1045.801 by revising the definitions of ``Adjustable 
parameter'' and ``Critical emission-related component'' to read as 
follows:

Sec.  1045.801  What definitions apply to this part?

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *
    Critical emission-related component has the meaning given in 40 CFR 
1068.30.
* * * * *

0
176. Revise Sec.  1045.815 to read as follows:

Sec.  1045.815  What provisions apply to confidential information?

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

PART 1048--CONTROL OF EMISSIONS FROM NEW, LARGE NONROAD SPARK-
IGNITION ENGINES

0
177. The authority citation for part 1048 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart B [Amended]

0
178. Amend Sec.  1048.115 by revising paragraphs (e) and (f) to read as 
follows:

Sec.  1048.115  What other requirements apply?

* * * * *
    (e) Adjustable parameters. Engines that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range. We may require that you set adjustable 
parameters to any specification within the practically adjustable range 
during any testing, including certification testing, production-line 
testing, or in-use testing. General provisions for adjustable 
parameters apply as specified in 40 CFR 1068.50.
    (f) Prohibited controls. You may not design your engines with 
emission control devices, systems, or elements of design that cause or 
contribute to an unreasonable risk to public health, welfare, or safety 
while operating. For example, an engine may not emit a noxious or toxic 
substance it would otherwise not emit that contributes to such an 
unreasonable risk.
* * * * *

0
179. Amend Sec.  1048.205 by revising paragraph (t) to read as follows:

Sec.  1048.205  What must I include in my application?

* * * * *
    (t) Describe all adjustable operating parameters (see Sec.  
1048.115(e)), including production tolerances. For any operating 
parameters that do not qualify as adjustable parameters, include a 
description supporting your conclusion (see 40 CFR 1068.50(c)). Include 
the following in your description of each adjustable parameter:
    (1) For practically adjustable parameters, include the nominal or 
recommended setting, the intended practically adjustable range, and the 
limits or stops used to establish adjustable ranges. State that the 
limits, stops, or other means of inhibiting adjustment are effective in 
preventing adjustment of parameters on in-use engines to settings 
outside your intended practically adjustable ranges and provide 
information to support this statement.
    (2) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustments on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
* * * * *

0
180. Amend Sec.  1048.240 by adding paragraph (f) to read as follows:

Sec.  1048.240  How do I demonstrate that my engine family complies 
with exhaust emission standards?

* * * * *
    (f) You may alternatively determine and verify deterioration 
factors based on bench-aged aftertreatment as described in 40 CFR 
1036.245 and 1036.246, with the following exceptions:
    (1) The minimum required aging for engines as specified in 40 CFR 
1036.245(c)(2) is 300 hours. Operate the engine for service 
accumulation using the same sequence of duty cycles that would apply 
for determining a deterioration factor under paragraph (c) of this 
section.
    (2) Use good engineering judgment to perform verification testing 
using the procedures of Sec.  1048.515 rather than 40 CFR 1036.555. For 
PEMS testing, measure emissions as the equipment goes through its 
normal operation over the course of the day (or shift-day).

0
181. Amend Sec.  1048.501 by revising paragraph (e)(2) to read as 
follows:

Sec.  1048.501  How do I run a valid emission test?

* * * * *
    (e) * * *
    (2) For engines equipped with carbon canisters that store fuel 
vapors that will be purged for combustion in the engine, precondition 
the canister as specified in 40 CFR 86.132-96(h) and then operate the 
engine for 60 minutes over repeat runs of the duty cycle specified in 
appendix II of this part.
* * * * *

0
182. Amend Sec.  1048.620 by revising paragraphs (a)(3), (d), and (e) 
to read as follows:

Sec.  1048.620  What are the provisions for exempting large engines 
fueled by natural gas or liquefied petroleum gas?

    (a) * * *
    (3) The engine must be in an engine family that has a valid 
certificate of conformity showing that it meets emission standards for 
engines of that power rating under 40 CFR part 1039.
* * * * *
    (d) Engines exempted under this section are subject to all the 
requirements affecting engines under 40 CFR part 1039. The requirements 
and restrictions of 40 CFR part 1039 apply to anyone manufacturing 
engines exempted under this section, anyone manufacturing equipment 
that uses these engines, and all other persons in the same manner as if 
these were nonroad diesel engines.
    (e) You may request an exemption under this section by submitting 
an application for certification for the engines under 40 CFR part 
1039.

0
183. Amend Sec.  1048.801 by revising the definitions of ``Adjustable 
parameter'' and ``Critical emission-related component'' to read as 
follows:

[[Page 4666]]

Sec.  1048.801  What definitions apply to this part?

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *
    Critical emission-related component has the meaning given in 40 CFR 
1068.30.
* * * * *

0
184. Revise Sec.  1048.815 to read as follows:

Sec.  1048.815  What provisions apply to confidential information?

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

PART 1051--CONTROL OF EMISSIONS FROM RECREATIONAL ENGINES AND 
VEHICLES

0
185. The authority citation for part 1051 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

Subpart B [Amended]

0
186. Amend Sec.  1051.115 by revising paragraphs (c), (d) introductory 
text, (d)(1), (d)(2) introductory text, and (e) to read as follows:

Sec.  1051.115  What other requirements apply?

* * * * *
    (c) Adjustable parameters. Vehicles that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range. Note that parameters that control the 
air-fuel ratio may be treated separately under paragraph (d) of this 
section. We may require that you set adjustable parameters to any 
specification within the practically adjustable range during any 
testing, including certification testing, production-line testing, or 
in-use testing. General provisions for adjustable parameters apply as 
specified in 40 CFR 1068.50.
    (d) Other adjustments. The following provisions apply for engines 
with carburetor jets or needles, and for engines with any other 
technology involving service to adjust air-fuel ratio that falls within 
the time and cost specifications of 40 CFR 1068.50(d)(1):
    (1) In your application for certification, specify the practically 
adjustable range of air-fuel ratios you expect to occur in use. You may 
specify it in terms of engine parts (such as the carburetor jet size 
and needle configuration as a function of atmospheric conditions).
    (2) The practically adjustable range specified in paragraph (d)(1) 
of this section must include all air-fuel ratios between the lean limit 
and the rich limit, unless you can show that some air-fuel ratios will 
not occur in use.
* * * * *
    (e) Prohibited controls. You may not design your engines with 
emission control devices, systems, or elements of design that cause or 
contribute to an unreasonable risk to public health, welfare, or safety 
while operating. For example, an engine may not emit a noxious or toxic 
substance it would otherwise not emit that contributes to such an 
unreasonable risk.
* * * * *

0
187. Amend Sec.  1051.205 by revising paragraph (q) to read as follows:

Sec.  1051.205  What must I include in my application?

* * * * *
    (q) Describe all adjustable operating parameters (see Sec.  
1051.115(e)), including production tolerances. For any operating 
parameters that do not qualify as adjustable parameters, include a 
description supporting your conclusion (see 40 CFR 1068.50(c)). Include 
the following in your description of each adjustable parameter:
    (1) For practically adjustable parameters, include the nominal or 
recommended setting, the intended practically adjustable range, and the 
limits or stops used to establish adjustable ranges. State that the 
limits, stops, or other means of inhibiting adjustment are effective in 
preventing adjustment of parameters on in-use engines to settings 
outside your intended practically adjustable ranges and provide 
information to support this statement.
    (2) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustments on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
* * * * *

0
188. Amend Sec.  1051.501 by revising paragraphs (c)(2), (d)(2)(i) and 
(d)(3) to read as follows:

Sec.  1051.501  What procedures must I use to test my vehicles or 
engines?

* * * * *
    (c) * * *
    (2) To measure fuel-line permeation emissions, use the equipment 
and procedures specified in SAE J30 as described in 40 CFR 1060.810. 
Prior to permeation testing, precondition the fuel line by filling it 
with the fuel specified in paragraph (d)(3) of this section, sealing 
the openings, and soaking it for 4 weeks at (23 5) [deg]C. 
Use the fuel specified in paragraph (d)(3) of this section. Perform 
daily measurements for 14 days, except that you may omit up to two 
daily measurements in any seven-day period. Maintain an ambient 
temperature of (23 2) [deg]C throughout the sampling 
period, except for intervals up to 30 minutes for weight measurements.
    (d) * * *
    (2) * * *
    (i) For the preconditioning soak described in Sec.  1051.515(a)(1) 
and fuel slosh durability test described in Sec.  1051.515(d)(3), use 
the fuel specified in 40 CFR 1065.710(b), or the fuel specified in 40 
CFR 1065.710(c) blended with 10 percent ethanol by volume. As an 
alternative, you may use Fuel CE10, which is Fuel C as specified in 
ASTM D471 (see 40 CFR 1060.810) blended with 10 percent ethanol by 
volume.
* * * * *
    (3) Fuel hose permeation. Use the fuel specified in 40 CFR 
1065.710(b), or the fuel specified in 40 CFR 1065.710(c) blended with 
10 percent ethanol by volume for permeation testing of fuel lines. As 
an alternative, you may use Fuel CE10, which is Fuel C as specified in 
ASTM D471 (see 40 CFR 1060.810) blended with 10 percent ethanol by 
volume.
* * * * *

0
189. Amend Sec.  1051.515 by revising paragraph (a)(1) to read as 
follows:

Sec.  1051.515  How do I test my fuel tank for permeation emissions?

* * * * *
    (a) * * *
    (1) Fill the tank with the fuel specified in Sec.  
1051.501(d)(2)(i), seal it, and allow it to soak at 28 5 
[deg]C for 20 weeks or at (43 5) [deg]C for 10 weeks.
* * * * *

0
190. Amend Sec.  1051.740 by revising paragraph (b)(5) to read as 
follows:

Sec.  1051.740  Are there special averaging provisions for snowmobiles?

* * * * *
    (b) * * *
    (5) Credits can also be calculated for Phase 3 using both sets of 
standards. Without regard to the trigger level values, if your net 
emission reduction for the redesignated averaging set exceeds the 
requirements of Phase 3 in Sec.  1051.103 (using both HC and CO in the 
Phase 3 equation in Sec.  1051.103), then your credits are the 
difference between the Phase 3 reduction requirement of that section 
and your calculated value.

[[Page 4667]]

0
191. Amend Sec.  1051.801 by revising the definitions of ``Adjustable 
parameter'' and ``Critical emission-related component'' to read as 
follows:

Sec.  1051.801  What definitions apply to this part?

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *
    Critical emission-related component has the meaning given in 40 CFR 
1068.30.
* * * * *

0
192. Revise Sec.  1051.815 to read as follows:

Sec.  1051.815  What provisions apply to confidential information?

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

PART 1054--CONTROL OF EMISSIONS FROM NEW, SMALL NONROAD SPARK-
IGNITION ENGINES AND EQUIPMENT

0
193. The authority citation for part 1054 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
194. Amend Sec.  1054.115 by revising paragraphs (b) and (d) to read as 
follows:

Sec.  1054.115  What other requirements apply?

* * * * *
    (b) Adjustable parameters. Engines that have adjustable parameters 
must meet all the requirements of this part for any adjustment in the 
practically adjustable range. We may require that you set adjustable 
parameters to any specification within the practically adjustable range 
during any testing, including certification testing, production-line 
testing, or in-use testing. You may ask us to limit idle-speed or 
carburetor adjustments to a smaller range than the practically 
adjustable range if you show us that the engine will not be adjusted 
outside of this smaller range during in-use operation without 
significantly degrading engine performance. General provisions for 
adjustable parameters apply as specified in 40 CFR 1068.50.
* * * * *
    (d) Prohibited controls. You may not design your engines with 
emission control devices, systems, or elements of design that cause or 
contribute to an unreasonable risk to public health, welfare, or safety 
while operating. For example, an engine may not emit a noxious or toxic 
substance it would otherwise not emit that contributes to such an 
unreasonable risk.
* * * * *

0
195. Amend Sec.  1054.205 by revising paragraphs (o)(1) and (q) to read 
as follows:

Sec.  1054.205  What must I include in my application?

* * * * *
    (o) * * *
    (1) Present emission data for hydrocarbon (such as THC, THCE, or 
NMHC, as applicable), NOX, and CO on an emission-data engine 
to show your engines meet the applicable exhaust emission standards as 
specified in Sec.  1054.101. Show emission figures before and after 
applying deterioration factors for each engine. Include test data from 
each applicable duty cycle as specified in Sec.  1054.505(b). If we 
specify more than one grade of any fuel type (for example, low-
temperature and all-season gasoline), you need to submit test data only 
for one grade, unless the regulations of this part specify otherwise 
for your engine.
* * * * *
    (q) Describe all adjustable operating parameters (see Sec.  
1054.115(b)), including production tolerances. For any operating 
parameters that do not qualify as adjustable parameters, include a 
description supporting your conclusion (see 40 CFR 1068.50(c)). Include 
the following in your description of each adjustable parameter:
    (1) For practically adjustable parameters, include the nominal or 
recommended setting, the intended practically adjustable range, and the 
limits or stops used to establish adjustable ranges. State that the 
limits, stops, or other means of inhibiting adjustment are effective in 
preventing adjustment of parameters on in-use engines to settings 
outside your intended practically adjustable ranges and provide 
information to support this statement.
    (2) For programmable operating parameters, state that you have 
restricted access to electronic controls to prevent parameter 
adjustments on in-use engines that would allow operation outside the 
practically adjustable range. Describe how your engines are designed to 
prevent unauthorized adjustments.
* * * * *

0
196. Amend Sec.  1054.230 by revising paragraphs (b)(8) and (9) to read 
as follows:

Sec.  1054.230  How do I select emission families?

* * * * *
    (b) * * *
    (8) Method of control for engine operation, other than governing. 
For example, multi-cylinder engines with port fuel injection may not be 
grouped into an emission family with engines that have a single 
throttle-body injector or carburetor.
    (9) The numerical level of the applicable emission standards. For 
example, an emission family may not include engines certified to 
different family emission limits, though you may change family emission 
limits without recertifying as specified in Sec.  1054.225.
* * * * *

0
197. Amend Sec.  1054.505 by revising paragraphs (a), (b) introductory 
text, (b)(1)(i), (b)(2), and (d)(1) to read as follows:

Sec.  1054.505  How do I test engines?

    (a) This section describes how to test engines under steady-state 
conditions. We may also perform other testing as allowed by the Clean 
Air Act. Sample emissions separately for each mode, then calculate an 
average emission level for the whole cycle using the weighting factors 
specified for each mode. Control engine speed as specified in this 
section. Use one of the following methods for confirming torque values 
for nonhandheld engines:
    (1) Calculate torque-related cycle statistics and compare with the 
established criteria as specified in 40 CFR 1065.514 to confirm that 
the test is valid.
    (2) Evaluate each mode separately to validate the duty cycle. All 
torque feedback values recorded during non-idle sampling periods must 
be within 2 percent of the reference value or within 0.27 N[middot]m of the reference value, whichever is greater. 
Also, the mean torque value during non-idle sampling periods must be 
within 1 percent of the reference value or 0.12 
N[middot]m of the reference value, whichever is greater. Control torque 
during idle as specified in paragraph (c) of this section.
    (b) Measure emissions by testing engines on a dynamometer with the 
test procedures for constant-speed engines in 40 CFR part 1065 while 
using the steady-state duty cycles identified in this paragraph (b) to 
determine whether it meets the exhaust emission standards specified in 
Sec.  1054.101(a). This paragraph (b) applies for all engines, 
including those not meeting the definition of ``constant-speed engine'' 
in 40 CFR 1065.1001.
    (1) * * *
    (i) For ungoverned handheld engines used in fixed-speed 
applications all having approximately the same nominal

[[Page 4668]]

in-use operating speed, hold engine speed within 350 rpm of the nominal 
speed for testing. We may allow you to include in your engine family, 
without additional testing, a small number of engines that will be 
installed such that they have a different nominal speed. If your engine 
family includes a majority of engines with approximately the same 
nominal in-use operating speed and a substantial number of engines with 
different nominal speeds, you must test engines as specified in this 
paragraph (b)(1)(i) and paragraph (b)(1)(ii) of this section.
* * * * *
    (2) For nonhandheld engines designed to idle, use the six-mode duty 
cycle described in paragraph (b)(1) of appendix II of this part; use 
the five-mode duty cycle described in paragraph (b)(2) of appendix II 
of this part for engines that are not designed to idle. If an engine 
family includes engines designed to idle and engines not designed to 
idle, include in the application for certification the test results for 
the duty cycle that will result in worst-case HC+NOX 
emissions based on measured values for that engine family. Control 
engine speed during the full-load operating mode as specified in 
paragraph (d) of this section. For all other modes, control engine 
speed to within 5 percent of the nominal speed specified in paragraph 
(d) of this section or let the installed governor (in the production 
configuration) control engine speed. For all modes except idle, control 
torque as needed to meet the cycle-validation criteria in paragraph (a) 
of this section. The governor may be adjusted before emission sampling 
to target the nominal speed identified in paragraph (d) of this 
section, but the installed governor must control engine speed 
throughout the emission-sampling period whether the governor is 
adjusted or not.
* * * * *
    (d) * * *
    (1) Select an engine speed for testing as follows:
    (i) For engines with a governed speed at full load between 2700 and 
4000 rpm, select appropriate test speeds for the emission family. If 
all the engines in the emission family are used in intermediate-speed 
equipment, select a test speed of 3060 rpm. The test associated with 
intermediate-speed operation is referred to as the A Cycle. If all the 
engines in the emission family are used in rated-speed equipment, 
select a test speed of 3600 rpm. The test associated with rated-speed 
operation is referred to as the B Cycle. If an emission family includes 
engines used in both intermediate-speed equipment and rated-speed 
equipment, measure emissions at test speeds of both 3060 and 3600 rpm. 
In unusual circumstances, you may ask to use a test speed different 
than that specified in this paragraph (d)(1)(i) if it better represents 
in-use operation.
    (ii) For engines with a governed speed below 2700 or above 4000 
rpm, ask us to approve one or more test speeds to represent those 
engines using the provisions for special procedures in 40 CFR 
1065.10(c)(2).
* * * * *

0
198. Amend Sec.  1054.801 by:
0
a. Revising the definitions of ``Adjustable parameter'' and ``Critical 
emission-related component''.
0
b. Removing the definition of ``Discrete mode''.
0
c. Revising the definition of ``Intermediate-speed equipment''.
0
d. Removing the definition of ``Ramped-modal''.
0
e. Revising the definitions of ``Rated-speed equipment'' and ``Steady-
state''.
    The revisions read as follows:

Sec.  1054.801  What definitions apply to this part?

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *
    Critical emission-related component has the meaning given in 40 CFR 
1068.30.
* * * * *
    Intermediate-speed equipment includes all nonhandheld equipment in 
which the installed engine's governed speed at full load is below 3330 
rpm. It may also include nonhandheld equipment in which the installed 
engine's governed speed at full load is as high as 3400 rpm.
* * * * *
    Rated-speed equipment includes all nonhandheld equipment in which 
the installed engine's governed speed at full load is at or above 3400 
rpm. It may also include nonhandheld equipment in which the installed 
engine's governed speed at full load is as low as 3330 rpm.
* * * * *
    Steady-state means relating to emission tests in which engine speed 
and load are held at a finite set of essentially constant values.
* * * * *

0
199. Revise Sec.  1054.815 to read as follows:

Sec.  1054.815  What provisions apply to confidential information?

    The provisions of 40 CFR 1068.10 and 1068.11 apply for information 
you submit under this part.

0
200. Redesignate appendix I to part 1054 as appendix A to part 1054 and 
amend newly redesignated appendix A by revising paragraph (b)(3) 
introductory text to read as follows:

Appendix A to Part 1054--Summary of Previous Emission Standards

* * * * *
    (b) * * *
    (3) Note that engines subject to Phase 1 standards were not 
subject to useful life, deterioration factor, production-line 
testing, or in-use testing provisions. In addition, engines subject 
to Phase 1 standards and engines subject to Phase 2 standards were 
both not subject to the following provisions:
* * * * *

0
201. Redesignate appendix II to part 1054 as appendix B to part 1054 
and revise newly redesignated appendix B to read as follows:

Appendix B to Part 1054--Duty Cycles for Laboratory Testing

    (a) Test handheld engines with the following steady-state duty 
cycle:

         Table 1 to Appendix B--Duty Cycle for Handheld Engines
------------------------------------------------------------------------
                                              Torque         Weighting
      G3 mode No.       Engine speed \a\   (percent) \b\      factors
------------------------------------------------------------------------
1.....................  Rated speed.....             100            0.85
2.....................  Warm idle.......               0            0.15
------------------------------------------------------------------------
\a\ Test engines at the specified speeds as described in Sec.
  1054.505.
\b\ Test engines at 100 percent torque by setting operator demand to
  maximum. Control torque during idle at its warm idle speed as
  described in 40 CFR 1065.510.

[[Page 4669]]

    (b) Test nonhandheld engines with one of the following steady-
state duty cycles:
    (1) The following duty cycle applies for engines designed to 
idle:

   Table 2 to Appendix B--Duty Cycle for Nonhandheld Engines With Idle
------------------------------------------------------------------------
                                              Torque         Weighting
             G2 Mode No.\a\                (percent) \b\      factors
------------------------------------------------------------------------
1.......................................             100            0.09
2.......................................              75            0.20
3.......................................              50            0.29
4.......................................              25            0.30
5.......................................              10            0.07
6.......................................               0            0.05
------------------------------------------------------------------------
\a\ Control engine speed as described in Sec.   1054.505. Control engine
  speed for Mode 6 as described in Sec.   1054.505(c) for idle
  operation.
\b\ The percent torque is relative to the value established for full-
  load torque, as described in Sec.   1054.505.

    (2) The following duty cycle applies for engines that are not 
designed to idle:

 Table 3 to Appendix B--Duty Cycle for Nonhandheld Engines Without Idle
------------------------------------------------------------------------
                                              Torque         Weighting
               Mode No.\a\                 (percent) \b\      factors
------------------------------------------------------------------------
1.......................................             100            0.09
2.......................................              75            0.21
3.......................................              50            0.31
4.......................................              25            0.32
5.......................................              10            0.07
------------------------------------------------------------------------
\a\ Control engine speed as described in Sec.   1054.505.
\b\ The percent torque is relative to the value established for full-
  load torque, as described in Sec.   1054.505.

PART 1060--CONTROL OF EVAPORATIVE EMISSIONS FROM NEW AND IN-USE 
NONROAD AND STATIONARY EQUIPMENT

0
202. The authority citation for part 1060 continues to read as follows:

    Authority:  42 U.S.C. 7401-7671q.

0
203. Amend Sec.  1060.101 by revising paragraph (e)(1) to read as 
follows:

Sec.  1060.101  What evaporative emission requirements apply under this 
part?

* * * * *
    (e) * * *
    (1) Adjustable parameters. Components or equipment with adjustable 
parameters must meet all the requirements of this part for any 
adjustment in the practically adjustable range. See 40 CFR 1068.50.
* * * * *

0
204. Amend Sec.  1060.515 by revising paragraphs (c) and (d) to read as 
follows:

Sec.  1060.515  How do I test EPA Nonroad Fuel Lines and EPA Cold-
Weather Fuel Lines for permeation emissions?

* * * * *
    (c) Except as specified in paragraph (d) of this section, measure 
fuel line permeation emissions using the equipment and procedures for 
weight-loss testing specified in SAE J30 or SAE J1527 (incorporated by 
reference in Sec.  1060.810). Start the measurement procedure within 8 
hours after draining and refilling the fuel line. Perform the emission 
test over a sampling period of 14 days. You may omit up to two daily 
measurements in any seven-day period. Determine your final emission 
result based on the average of measured values over the 14-day period. 
Maintain an ambient temperature of (232) [deg]C throughout 
the sampling period, except for intervals up to 30 minutes for daily 
weight measurements.
    (d) For fuel lines with a nominal inner diameter below 5.0 mm, you 
may alternatively measure fuel line permeation emissions using the 
equipment and procedures for weight-loss testing specified in SAE J2996 
(incorporated by reference in Sec.  1060.810). Determine your final 
emission result based on the average of measured values over the 14-day 
sampling period. Maintain an ambient temperature of (232) 
[deg]C throughout the sampling period, except for intervals up to 30 
minutes for daily weight measurements.
* * * * *

0
205. Amend Sec.  1060.520 by revising paragraph (b)(1) to read as 
follows:

Sec.  1060.520  How do I test fuel tanks for permeation emissions?

* * * * *
    (b) * * *
    (1) Fill the fuel tank to its nominal capacity with the fuel 
specified in paragraph (e) of this section, seal it, and allow it to 
soak at (285) [deg]C for at least 20 weeks. Alternatively, 
the fuel tank may be soaked for at least 10 weeks at (435) 
[deg]C. You may count the time of the preconditioning steps in 
paragraph (a) of this section as part of the preconditioning fuel soak 
as long as the ambient temperature remains within the specified 
temperature range and the fuel tank continues to be at least 40 percent 
full throughout the test; you may add or replace fuel as needed to 
conduct the specified durability procedures. Void the test if you 
determine that the fuel tank has any kind of leak.
* * * * *

0
206. Amend Sec.  1060.801 by revising the definition of ``Adjustable 
parameter'' to read as follows:

Sec.  1060.801  What definitions apply to this part?

* * * * *
    Adjustable parameter has the meaning given in 40 CFR 1068.50.
* * * * *

PART 1065--ENGINE-TESTING PROCEDURES

0
207. The authority citation for part 1065 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
208. Amend Sec.  1065.1 by revising paragraphs (a)(1) through (5) and 
(8) and adding paragraph (i) to read as follows:

Sec.  1065.1  Applicability.

    (a) * * *
    (1) Locomotives we regulate under 40 CFR part 1033.
    (2) Heavy-duty highway engines we regulate under 40 CFR parts 86 
and 1036.
    (3) Nonroad compression-ignition engines we regulate under 40 CFR 
part 1039 and stationary diesel engines that are certified to the 
standards in 40 CFR part 1039 as specified in 40 CFR part 60, subpart 
IIII.
    (4) Marine compression-ignition engines we regulate under 40 CFR 
part 1042.
    (5) Marine spark-ignition engines we regulate under 40 CFR part 
1045.
* * * * *
    (8) Small nonroad spark-ignition engines we regulate under 40 CFR 
part 1054 and stationary engines that are certified to the standards in 
40 CFR part 1054 as specified in 40 CFR part 60, subpart JJJJ.
* * * * *
    (i) The following additional procedures apply as described in 
subpart L of this part:
    (1) Measuring brake-specific emissions of semi-volatile organic 
compounds, which are not subject to separate emission standards.
    (2) Identifying the threshold temperature for vanadium sublimation 
for SCR catalysts.
    (3) Measuring the smoke opacity of engine exhaust.
    (4) Aging aftertreatment devices in support of determining 
deterioration factors for certified compression-ignition engines.

0
209. Amend Sec.  1065.5 by revising paragraphs (a) introductory text 
and (c) to read as follows:

Sec.  1065.5  Overview of this part 1065 and its relationship to the 
standard-setting part.

    (a) This part specifies procedures that apply generally to 
measuring brake-specific emissions from various

[[Page 4670]]

categories of engines. See subpart L of this part for measurement 
procedures for testing related to standards other than brake-specific 
emission standards. See the standard-setting part for directions in 
applying specific provisions in this part for a particular type of 
engine. Before using this part's procedures, read the standard-setting 
part to answer at least the following questions:
* * * * *
    (c) The following table shows how this part divides testing 
specifications into subparts:

       Table 1 of Sec.   1065.5--Description of Part 1065 Subparts
------------------------------------------------------------------------
                                   Describes these specifications or
         This subpart                          procedures
------------------------------------------------------------------------
Subpart A....................  Applicability and general provisions.
Subpart B....................  Equipment for testing.
Subpart C....................  Measurement instruments for testing.
Subpart D....................  Calibration and performance verifications
                                for measurement systems.
Subpart E....................  How to prepare engines for testing,
                                including service accumulation.
Subpart F....................  How to run an emission test over a
                                predetermined duty cycle.
Subpart G....................  Test procedure calculations.
Subpart H....................  Fuels, engine fluids, analytical gases,
                                and other calibration standards.
Subpart I....................  Special procedures related to oxygenated
                                fuels.
Subpart J....................  How to test with portable emission
                                measurement systems (PEMS).
Subpart L....................  How to test for unregulated and special
                                pollutants and to perform additional
                                measurements related to certification.
------------------------------------------------------------------------

0
210. Amend Sec.  1065.10 by revising paragraph (c)(7)(ii) to read as 
follows:

Sec.  1065.10  Other procedures.

* * * * *
    (c) * * *
    (7) * * *
    (ii) Submission. Submit requests in writing to the EPA Program 
Officer.
* * * * *

0
211. Amend Sec.  1065.12 by revising paragraph (a) to read as follows:

Sec.  1065.12  Approval of alternate procedures.

    (a) To get approval for an alternate procedure under Sec.  
1065.10(c), send the EPA Program Officer an initial written request 
describing the alternate procedure and why you believe it is equivalent 
to the specified procedure. Anyone may request alternate procedure 
approval. This means that an individual engine manufacturer may request 
to use an alternate procedure. This also means that an instrument 
manufacturer may request to have an instrument, equipment, or procedure 
approved as an alternate procedure to those specified in this part. We 
may approve your request based on this information alone, whether or 
not it includes all the information specified in this section. Where we 
determine that your original submission does not include enough 
information for us to determine that the alternate procedure is 
equivalent to the specified procedure, we may ask you to submit 
supplemental information showing that your alternate procedure is 
consistently and reliably at least as accurate and repeatable as the 
specified procedure.
* * * * *

0
212. Amend Sec.  1065.140 by revising paragraph (b)(2) introductory 
text, (c)(2), (c)(6) introductory text, and (e)(4) to read as follows:

Sec.  1065.140  Dilution for gaseous and PM constituents.

* * * * *
    (b) * * *
    (2) Measure these background concentrations the same way you 
measure diluted exhaust constituents, or measure them in a way that 
does not affect your ability to demonstrate compliance with the 
applicable standards in this chapter. For example, you may use the 
following simplifications for background sampling:
* * * * *
    (c) * * *
    (2) Pressure control. Maintain static pressure at the location 
where raw exhaust is introduced into the tunnel within 1.2 
kPa of atmospheric pressure. You may use a booster blower to control 
this pressure. If you test using more careful pressure control and you 
show by engineering analysis or by test data that you require this 
level of control to demonstrate compliance at the applicable standards 
in this chapter, we will maintain the same level of static pressure 
control when we test.
* * * * *
    (6) Aqueous condensation. You must address aqueous condensation in 
the CVS as described in this paragraph (c)(6). You may meet these 
requirements by preventing or limiting aqueous condensation in the CVS 
from the exhaust inlet to the last emission sample probe. See paragraph 
(c)(6)(2)(B) of this section for provisions related to the CVS between 
the last emission sample probe and the CVS flow meter. You may heat 
and/or insulate the dilution tunnel walls, as well as the bulk stream 
tubing downstream of the tunnel to prevent or limit aqueous 
condensation. Where we allow aqueous condensation to occur, use good 
engineering judgment to ensure that the condensation does not affect 
your ability to demonstrate that your engines comply with the 
applicable standards in this chapter (see Sec.  1065.10(a)).
* * * * *
    (e) * * *
    (4) Control sample temperature to a (47 5) [deg]C 
tolerance, as measured anywhere within 20 cm upstream or downstream of 
the PM storage media (such as a filter). You may instead measure sample 
temperature up to 30 cm upstream of the filter or other PM storage 
media if it is housed within a chamber with temperature controlled to 
stay within the specified temperature range. Measure sample temperature 
with a bare-wire junction thermocouple with wires that are (0.500 
0.025) mm diameter, or with another suitable instrument 
that has equivalent performance.

0
213. Amend Sec.  1065.145 by revising paragraph (b)(2) to read as 
follows:

Sec.  1065.145  Gaseous and PM probes, transfer lines, and sampling 
system components.

* * * * *
    (b) * * *
    (2) Sample and measure emissions from each stack and calculate 
emissions separately for each stack. Add the mass (or mass rate) 
emissions from each stack to calculate the emissions from the entire 
engine. Testing under this paragraph (b)(2) requires measuring or

[[Page 4671]]

calculating the exhaust molar flow for each stack separately. If the 
exhaust molar flow in each stack cannot be calculated from intake air 
flow(s), fuel flow(s), and measured gaseous emissions, and it is 
impractical to measure the exhaust molar flows directly, you may 
alternatively proportion the engine's calculated total exhaust molar 
flow rate (where the flow is calculated using intake air mass flow(s), 
fuel mass flow(s), and emissions concentrations) based on exhaust molar 
flow measurements in each stack using a less accurate, non-traceable 
method. For example, you may use a total pressure probe and static 
pressure measurement in each stack.
* * * * *

0
214. Amend Sec.  1065.170 by revising paragraphs (a)(1) and (c)(1)(ii) 
and (iii) to read as follows:

Sec.  1065.170  Batch sampling for gaseous and PM constituents.

* * * * *
    (a) * * *
    (1) Verify proportional sampling after an emission test as 
described in Sec.  1065.545. You must exclude from the proportional 
sampling verification any portion of the test where you are not 
sampling emissions because the engine is turned off and the batch 
samplers are not sampling, accounting for exhaust transport delay in 
the sampling system. Use good engineering judgment to select storage 
media that will not significantly change measured emission levels 
(either up or down). For example, do not use sample bags for storing 
emissions if the bags are permeable with respect to emissions or if 
they off gas emissions to the extent that it affects your ability to 
demonstrate compliance with the applicable gaseous emission standards 
in this chapter. As another example, do not use PM filters that 
irreversibly absorb or adsorb gases to the extent that it affects your 
ability to demonstrate compliance with the applicable PM emission 
standards in this chapter.
* * * * *
    (c) * * *
    (1) * * *
    (ii) The filter must be circular, with an overall diameter of 
(46.50 0.60) mm and an exposed diameter of at least 38 mm. 
See the cassette specifications in paragraph (c)(1)(vii) of this 
section.
    (iii) We highly recommend that you use a pure PTFE filter material 
that does not have any flow-through support bonded to the back and has 
an overall thickness of (40 20) [micro]m. An inert polymer 
ring may be bonded to the periphery of the filter material for support 
and for sealing between the filter cassette parts. We consider 
Polymethylpentene (PMP) and PTFE inert materials for a support ring, 
but other inert materials may be used. See the cassette specifications 
in paragraph (c)(1)(vii) of this section. We allow the use of PTFE-
coated glass fiber filter material, as long as this filter media 
selection does not affect your ability to demonstrate compliance with 
the applicable standards in this chapter, which we base on a pure PTFE 
filter material. Note that we will use pure PTFE filter material for 
compliance testing, and we may require you to use pure PTFE filter 
material for any compliance testing we require, such as for selective 
enforcement audits.
* * * * *

Sec.  1065.190  [Amended]

0
215. Amend Sec.  1065.190 by removing paragraphs (g)(5) and (6).

0
216. Amend Sec.  1065.210 by revising paragraph (a) to read as follows:

Sec.  1065.210  Work input and output sensors.

    (a) Application. Use instruments as specified in this section to 
measure work inputs and outputs during engine operation. We recommend 
that you use sensors, transducers, and meters that meet the 
specifications in Table 1 of Sec.  1065.205. Note that your overall 
systems for measuring work inputs and outputs must meet the linearity 
verifications in Sec.  1065.307. We recommend that you measure work 
inputs and outputs where they cross the system boundary as shown in 
Figure 1 of this section. The system boundary is different for air-
cooled engines than for liquid-cooled engines. If you choose to measure 
work before or after a work conversion, relative to the system 
boundary, use good engineering judgment to estimate any work-conversion 
losses in a way that avoids overestimation of total work. For example, 
if it is impractical to instrument the shaft of an exhaust turbine 
generating electrical work, you may decide to measure its converted 
electrical work. As another example, you may decide to measure the 
tractive (i.e., electrical output) power of a locomotive, rather than 
the brake power of the locomotive engine. In these cases, divide the 
electrical work by accurate values of electrical generator efficiency 
([eta] <1), or assume an efficiency of 1 ([eta] =1), which would over-
estimate brake-specific emissions. For the example of using locomotive 
tractive power with a generator efficiency of 1 ([eta] =1), this means 
using the tractive power as the brake power in emission calculations. 
Do not underestimate any work conversion efficiencies for any 
components outside the system boundary that do not return work into the 
system boundary. And do not overestimate any work conversion 
efficiencies for components outside the system boundary that do return 
work into the system boundary. In all cases, ensure that you are able 
to accurately demonstrate compliance with the applicable standards in 
this chapter. Figure 1 follows:

Figure 1 to Paragraph (a) of Sec.  1065.210: Work Inputs, Outputs, and 
System Boundaries

[[Page 4672]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.103

* * * * *

0
217. Amend Sec.  1065.260 by revising paragraph (a) to read as follows:

Sec.  1065.260  Flame-ionization detector.

    (a) Application. Use a flame-ionization detector (FID) analyzer to 
measure hydrocarbon concentrations in raw or diluted exhaust for either 
batch or continuous sampling. Determine hydrocarbon concentrations on a 
carbon number basis of one, C1. For measuring THC or THCE 
you must use a FID analyzer. For measuring CH4 you must meet 
the requirements of paragraph (g) of this section. See subpart I of 
this part

[[Page 4673]]

for special provisions that apply to measuring hydrocarbons when 
testing with oxygenated fuels.
* * * * *

0
218. Add Sec.  1065.274 under undesignated center heading 
``NOX and N2O Measurements'' to read as follows:

Sec.  1065.274  Zirconium dioxide (ZrO2) NOX analyzer.

    (a) Application. You may use a zirconia oxide (ZrO2) 
analyzer to measure NOX in raw exhaust for field-testing 
engines.
    (b) Component requirements. We recommend that you use a 
ZrO2 analyzer that meets the specifications in Table 1 of 
Sec.  1065.205. Note that your ZrO2-based system must meet 
the linearity verification in Sec.  1065.307.
    (c) Species measured. The ZrO2-based system must be able 
to measure and report NO and NO2 together as NOX. 
If the ZrO2-based system cannot measure all of the 
NO2, you may develop and apply correction factors based on 
good engineering judgment to account for this deficiency.
    (d) Interference. You must account for NH3 interference 
with the NOX measurement.

0
219. Amend Sec.  1065.284 by revising the section heading to read as 
follows:

Sec.  1065.284  Zirconium dioxide (ZrO2) air-fuel ratio and O2 
analyzer.

* * * * *

0
220. Add Sec.  1065.298 to read as follows:

Sec.  1065.298  Correcting real-time PM measurement based on 
gravimetric PM filter measurement for field-testing analysis.

    (a) Application. You may quantify net PM on a sample medium for 
field testing with a continuous PM measurement with correction based on 
gravimetric PM filter measurement.
    (b) Measurement principles. Photoacoustic or electrical aerosol 
instruments used in field-testing typically under-report PM emissions. 
Apply the verifications and corrections described in this section to 
meet accuracy requirements.
    (c) Component requirements. (1) Gravimetric PM measurement must 
meet the laboratory measurement requirements of this part 1065, noting 
that there are specific exceptions to some laboratory requirements and 
specification for field testing given in Sec.  1065.905(d)(2). In 
addition to those exceptions, field testing does not require you to 
verify proportional flow control as specified in Sec.  1065.545. Note 
also that the linearity requirements of Sec.  1065.307 apply only as 
specified in this section.
    (2) Check the calibration and linearity of the photoacoustic and 
electrical aerosol instruments according to the instrument 
manufacturer's instructions and the following recommendations:
    (i) For photoacoustic instruments we recommend one of the 
following:
    (A) Use a reference elemental carbon-based PM source to calibrate 
the instrument Verify the photoacoustic instrument by comparing results 
either to a gravimetric PM measurement collected on the filter or to an 
elemental carbon analysis of collected PM.
    (B) Use a light absorber that has a known amount of laser light 
absorption to periodically verify the instrument's calibration factor. 
Place the light absorber in the path of the laser beam. This 
verification checks the integrity of the microphone sensitivity, the 
power of the laser diode, and the performance of the analog-to-digital 
converter.
    (C) Verify that you meet the linearity requirements in Table 1 of 
Sec.  1065.307 by generating a maximum reference PM mass concentration 
(verified gravimetrically) and then using partial-flow sampling to 
dilute to various evenly distributed concentrations.
    (ii) For electrical aerosol instruments we recommend one of the 
following:
    (A) Use reference monodisperse or polydisperse PM-like particles 
with a mobility diameter or count median diameter greater than 45 nm. 
Use an electrometer or condensation particle counter that has a 
d50 at or below 10 nm to verify the reference values.
    (B) Verify that you meet the linearity requirements in Table 1 of 
Sec.  1065.307 using a maximum reference particle concentration, a 
zero-reference concentration, and at least two other evenly distributed 
points. Use partial-flow dilution to create the additional reference PM 
concentrations. The difference between measured values from the 
electrical aerosol and reference instruments at each point must be no 
greater than 15% of the mean value from the two measurements at that 
point.
    (d) Loss correction. You may use PM loss corrections to account for 
PM loss in the sample handling system.
    (e) Correction. Develop a multiplicative correction factor to 
ensure that total PM measured by photoacoustic or electrical aerosol 
instruments equate to the gravimetric filter-based total PM 
measurement. Calculate the correction factor by dividing the mass of PM 
captured on the gravimetric filter by the quantity represented by the 
total concentration of PM measured by the instrument multiplied by the 
time over the test interval multiplied by the gravimetric filter sample 
flow rate.

0
221. Amend Sec.  1065.301 by revising paragraph (d) to read as follows:

Sec.  1065.301  Overview and general provisions.

* * * * *
    (d) Use NIST-traceable standards to the tolerances we specify for 
calibrations and verifications. Where we specify the need to use NIST-
traceable standards, you may alternatively use international standards 
recognized by the CIPM Mutual Recognition Arrangement that are not 
NIST-traceable.

0
222. Amend Sec.  1065.305 by revising paragraph (d)(10)(ii) to read as 
follows:

Sec.  1065.305  Verifications for accuracy, repeatability, and noise.

* * * * *
    (d) * * *
    (10) * * *
    (ii) The measurement deficiency does not adversely affect your 
ability to demonstrate compliance with the applicable standards in this 
chapter.

0
223. Amend Sec.  1065.307 by revising paragraphs (b), (d) introductory 
text, and (f) to read as follows:

Sec.  1065.307  Linearity verification.

* * * * *
    (b) Performance requirements. If a measurement system does not meet 
the applicable linearity criteria referenced in Table 1 of this 
section, correct the deficiency by re-calibrating, servicing, or 
replacing components as needed. Repeat the linearity verification after 
correcting the deficiency to ensure that the measurement system meets 
the linearity criteria. Before you may use a measurement system that 
does not meet linearity criteria, you must demonstrate to us that the 
deficiency does not adversely affect your ability to demonstrate 
compliance with the applicable standards in this chapter.
* * * * *
    (d) Reference signals. This paragraph (d) describes recommended 
methods for generating reference values for the linearity-verification 
protocol in paragraph (c) of this section. Use reference values that 
simulate actual values, or introduce an actual value and measure it 
with a reference-measurement system. In the latter case, the reference 
value is the value reported by the reference-measurement system. 
Reference values and reference-measurement systems must be NIST-
traceable. We recommend using calibration reference quantities that are 
NIST-traceable within 0.5% uncertainty, if not specified 
elsewhere

[[Page 4674]]

in this part 1065. Use the following recommended methods to generate 
reference values or use good engineering judgment to select a different 
reference:
* * * * *
    (f) Performance criteria for measurement systems. Table 1 follows:

                                   Table 1 of Sec.   1065.307--Measurement Systems That Require Linearity Verification
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                                   Linearity criteria
        Measurement system                   Quantity          -----------------------------------------------------------------------------------------
                                                                   [verbar]xmin(a1-1)+a0[verbar]          a1                 SEE               r \2\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Speed.............................  fn........................  <=0.05% [middot]fnmax.............       0.98-1.02  <=2% [middot]fnmax..         >=0.990
Torque............................  T.........................  <=1% [middot] Tmax................       0.98-1.02  <=2% [middot] Tmax..         >=0.990
Electrical power..................  P.........................  <=1% [middot] Pmax................       0.98-1.02  <=2% [middot] Pmax..         >=0.990
Current...........................  I.........................  <=1% [middot] Imax................       0.98-1.02  <=2% [middot] Imax..         >=0.990
Voltage...........................  U.........................  <=1% [middot] Umax................       0.98-1.02  <=2% [middot] Umax..         >=0.990
Fuel flow rate....................  m.........................  <=1% [middot] mmax................       0.98-1.02  <=2% [middot] mmax..         >=0.990
Fuel mass scale...................  m.........................  <=0.3% [middot] mmax..............     0.996-1.004  <=0.4% [middot] mmax         >=0.999
DEF flow rate.....................  m.........................  <=1% [middot] mmax................       0.98-1.02  <=2% [middot] mmax..         >=0.990
DEF mass scale....................  m.........................  <=0.3% [middot] mmax..............     0.996-1.004  <=0.4% [middot] mmax         >=0.999
Intake-air flow rate \a\..........  n.........................  <=1% [middot] nmax................       0.98-1.02  <=2% [middot] nmax..         >=0.990
Dilution air flow rate \a\........  n.........................  <=1% [middot] nmax................       0.98-1.02  <=2% [middot] nmax..         >=0.990
Diluted exhaust flow rate \a\.....  n.........................  <=1% [middot] nmax................       0.98-1.02  <=2% [middot] nmax..         >=0.990
Raw exhaust flow rate \a\.........  n.........................  <=1% [middot] nmax................       0.98-1.02  <=2% [middot]nmax...         >=0.990
Batch sampler flow rates \a\......  n.........................  <=1% [middot] nmax................       0.98-1.02  <=2% [middot]nmax...         >=0.990
Gas dividers......................  x/xspan...................  <=0.5% [middot] xmax/xspan........       0.98-1.02  <=2% [middot] xmax/          >=0.990
                                                                                                                     xspan.
Gas analyzers for laboratory        x.........................  <=0.5% [middot] xmax..............       0.99-1.01  <=1% [middot] xmax..         >=0.998
 testing.
Gas analyzers for field testing...  x.........................  <=1% [middot] xmax................       0.99-1.01  <=1% [middot] xmax..         >=0.998
Electrical aerosol analyzer for     x.........................  <=5% [middot] xmax................       0.85-1.15  <=10% [middot] xmax.         >=0.950
 field testing.
Photoacoustic analyzer for field    x.........................  <=5% [middot] xmax................       0.90-1.10  <=10% [middot] xmax.         >=0.980
 testing.
PM balance........................  m.........................  <=1% [middot] mmax................       0.99-1.01  <=1% [middot] mmax..         >=0.998
Pressures.........................  p.........................  <=1% [middot] pmax................       0.99-1.01  <=1% [middot] pmax..         >=0.998
Dewpoint for intake air, PM-        Tdew......................  <=0.5% [middot] Tdewmax...........       0.99-1.01  <=0.5%                       >=0.998
 stabilization and balance                                                                                           [middot]Tdewmax.
 environments.
Other dewpoint measurements.......  Tdew......................  <=1% [middot] Tdewmax.............       0.99-1.01  <=1% [middot]                >=0.998
                                                                                                                     Tdewmax.
Analog-to-digital conversion of     T.........................  <=1% [middot] Tmax................       0.99-1.01  <=1% [middot] Tmax..         >=0.998
 temperature signals.
--------------------------------------------------------------------------------------------------------------------------------------------------------
\a\ For flow meters that determine volumetric flow rate, Vstd, you may substitute Vstd for n as the quantity and substitute Vstdmax for nmax.

* * * * *

0
224. Amend Sec.  1065.308 by revising paragraph (e)(3) to read as 
follows:

Sec.  1065.308  Continuous gas analyzer system-response and updating-
recording verification--for gas analyzers not continuously compensated 
for other gas species.

* * * * *
    (e) * * *
    (3) If a measurement system fails the criteria in paragraphs (e)(1) 
and (2) of this section, you may use the measurement system only if the 
deficiency does not adversely affect your ability to show compliance 
with the applicable standards in this chapter.
* * * * *

0
225. Amend Sec.  1065.309 by revising paragraph (e)(3) to read as 
follows:

Sec.  1065.309  Continuous gas analyzer system-response and updating-
recording verification--for gas analyzers continuously compensated for 
other gas species.

* * * * *
    (e) * * *
    (3) If a measurement system fails the criteria in paragraphs (e)(1) 
and (2) of this section, you may use the measurement system only if the 
deficiency does not adversely affect your ability to show compliance 
with the applicable standards in this chapter.
* * * * *

0
226. Amend Sec.  1065.315 by revising paragraphs (a)(1) through (3) and 
(b) to read as follows:

Sec.  1065.315  Pressure, temperature, and dewpoint calibration.

    (a) * * *
    (1) Pressure. We recommend temperature-compensated, digital-
pneumatic, or deadweight pressure calibrators, with data-logging 
capabilities to minimize transcription errors. We recommend using 
calibration reference quantities that are NIST-traceable within 0.5% uncertainty.
    (2) Temperature. We recommend digital dry-block or stirred-liquid 
temperature calibrators, with data logging capabilities to minimize 
transcription errors. We recommend using calibration reference 
quantities that are NIST-traceable within 0.5% uncertainty. 
You may perform linearity verification for temperature measurement 
systems with thermocouples, RTDs, and thermistors by removing the 
sensor from the system and using a simulator in its place. Use a NIST-
traceable simulator that is independently calibrated and, as 
appropriate, cold-junction compensated. The simulator uncertainty 
scaled to absolute temperature must be less than 0.5% of 
Tmax. If you use this option, you must use sensors that the 
supplier states are accurate to better than 0.5% of Tmax 
compared with their standard calibration curve.
    (3) Dewpoint. We recommend a minimum of three different 
temperature-equilibrated and temperature-monitored calibration salt 
solutions in containers that seal completely around the dewpoint 
sensor. We recommend using calibration reference quantities that are 
NIST-traceable within 0.5% uncertainty.
    (b) You may remove system components for off-site calibration. We 
recommend specifying calibration reference quantities that are NIST-
traceable within 0.5% uncertainty.

0
227. Amend Sec.  1065.320 by revising paragraph (c) to read as follows:

Sec.  1065.320  Fuel-flow calibration.

* * * * *
    (c) You may remove system components for off-site calibration. When 
installing a flow meter with an off-site calibration, we recommend that

[[Page 4675]]

you consider the effects of the tubing configuration upstream and 
downstream of the flow meter. We recommend specifying calibration 
reference quantities that are NIST-traceable within 0.5% 
uncertainty.

0
228. Amend Sec.  1065.325 by revising paragraphs (a) and (b) to read as 
follows:

Sec.  1065.325  Intake-flow calibration.

    (a) Calibrate intake-air flow meters upon initial installation. 
Follow the instrument manufacturer's instructions and use good 
engineering judgment to repeat the calibration. We recommend using a 
calibration subsonic venturi, ultrasonic flow meter or laminar flow 
element. We recommend using calibration reference quantities that are 
NIST-traceable within 0.5% uncertainty.
    (b) You may remove system components for off-site calibration. When 
installing a flow meter with an off-site calibration, we recommend that 
you consider the effects of the tubing configuration upstream and 
downstream of the flow meter. We recommend specifying calibration 
reference quantities that are NIST-traceable within 0.5% 
uncertainty.
* * * * *

0
229. Amend Sec.  1065.330 by revising paragraphs (a) and (b) to read as 
follows:

Sec.  1065.330  Exhaust-flow calibration.

    (a) Calibrate exhaust-flow meters upon initial installation. Follow 
the instrument manufacturer's instructions and use good engineering 
judgment to repeat the calibration. We recommend that you use a 
calibration subsonic venturi or ultrasonic flow meter and simulate 
exhaust temperatures by incorporating a heat exchanger between the 
calibration meter and the exhaust-flow meter. If you can demonstrate 
that the flow meter to be calibrated is insensitive to exhaust 
temperatures, you may use other reference meters such as laminar flow 
elements, which are not commonly designed to withstand typical raw 
exhaust temperatures. We recommend using calibration reference 
quantities that are NIST-traceable within 0.5% uncertainty.
    (b) You may remove system components for off-site calibration. When 
installing a flow meter with an off-site calibration, we recommend that 
you consider the effects of the tubing configuration upstream and 
downstream of the flow meter. We recommend specifying calibration 
reference quantities that are NIST-traceable within 0.5% 
uncertainty.
* * * * *

0
230. Amend Sec.  1065.341 by revising paragraph (e)(3) to read as 
follows:

Sec.  1065.341  CVS and PFD flow verification (propane check).

* * * * *
    (e) * * *
    (3) Calculate total C3H8 mass based on your 
CVS and HC data as described in Sec.  1065.650 (40 CFR 1066.605 for 
vehicle testing) and Sec.  1065.660, using the molar mass of 
C3H8, MC3H8, instead of the effective 
molar mass of HC, MHC.
* * * * *

0
231. Amend Sec.  1065.345 by revising paragraph (d) to read as follows:

Sec.  1065.345  Vacuum-side leak verification.

* * * * *
    (d) Dilution-of-span-gas leak test. You may use any gas analyzer 
for this test. If you use a FID for this test, correct for any HC 
contamination in the sampling system according to Sec.  1065.660. If 
you use an O2 analyzer described in Sec.  1065.280 for this 
test, you may use purified N2 to detect a leak. To avoid 
misleading results from this test, we recommend using only analyzers 
that have a repeatability of 0.5% or better at the reference gas 
concentration used for this test. Perform a vacuum-side leak test as 
follows:
    (1) Prepare a gas analyzer as you would for emission testing.
    (2) Supply reference gas to the analyzer span port and record the 
measured value.
    (3) Route overflow reference gas to the inlet of the sample probe 
or at a tee fitting in the transfer line near the exit of the probe. 
You may use a valve upstream of the overflow fitting to prevent 
overflow of reference gas out of the inlet of the probe, but you must 
then provide an overflow vent in the overflow supply line.
    (4) Verify that the measured overflow reference gas concentration 
is within 0.5% of the concentration measured in paragraph 
(d)(2) of this section. A measured value lower than expected indicates 
a leak, but a value higher than expected may indicate a problem with 
the reference gas or the analyzer itself. A measured value higher than 
expected does not indicate a leak.
* * * * *

0
232. Amend Sec.  1065.350 by revising paragraph (e)(1) to read as 
follows:

Sec.  1065.350  H2O interference verification for CO2 NDIR analyzers.

* * * * *
    (e) * * *
    (1) You may omit this verification if you can show by engineering 
analysis that for your CO2 sampling system and your 
emission-calculation procedures, the H2O interference for 
your CO2 NDIR analyzer always affects your brake-specific 
emission results within 0.5% of each of the applicable 
standards in this chapter. This specification also applies for vehicle 
testing, except that it relates to emission results in g/mile or g/
kilometer.
* * * * *

0
233. Amend Sec.  1065.405 by revising paragraph (a) to read as follows:

Sec.  1065.405  Test engine preparation and maintenance.

* * * * *
    (a) If you are testing an emission-data engine for certification, 
make sure it is built to represent production engines, consistent with 
paragraph (f) of this section.
    (1) This includes governors that you normally install on production 
engines. Production engines should also be tested with their installed 
governors. If your engine is equipped with multiple user-selectable 
governor types and if the governor does not manipulate the emission 
control system (i.e., the governor only modulates an ``operator 
demand'' signal such as commanded fuel rate, torque, or power), choose 
the governor type that allows the test cell to most accurately follow 
the duty cycle. If the governor manipulates the emission control 
system, treat it as an adjustable parameter. If you do not install 
governors on production engines, simulate a governor that is 
representative of a governor that others will install on your 
production engines.
    (2) In certain circumstances, you may incorporate test cell 
components to simulate an in-use configuration, consistent with good 
engineering judgment. For example, Sec. Sec.  1065.122 and 1065.125 
allow the use of test cell components to represent engine cooling and 
intake air systems.
    (3) The provisions in Sec.  1065.110(e) also apply to emission-data 
engines for certification.
    (4) For engines using SCR, use any size DEF tank and fuel tank. We 
may require you to give us a production-type DEF tank, including any 
associated sensors, for our testing.
* * * * *

0
234. Amend Sec.  1065.410 by revising paragraph (c) to read as follows:

Sec.  1065.410  Maintenance limits for stabilized test engines.

* * * * *
    (c) If you inspect an engine, keep a record of the inspection and 
update your application for certification to document any changes that 
result. You may use any kind of equipment,

[[Page 4676]]

instrument, or tool that is available at dealerships and other service 
outlets to identify malfunctioning components or perform maintenance. 
You may inspect using electronic tools or internal engine systems to 
monitor engine performance, but only if the information is readable 
without specialized equipment.
* * * * *

0
235. Amend Sec.  1065.501 by revising paragraph (a) introductory text 
to read as follows:

Sec.  1065.501  Overview.

    (a) Use the procedures detailed in this subpart to measure engine 
emissions over a specified duty cycle. Refer to subpart J of this part 
for field test procedures that describe how to measure emissions during 
in-use engine operation. Refer to subpart L of this part for 
measurement procedures for testing related to standards other than 
brake-specific emission standards. This section describes how to--
* * * * *

0
236. Amend Sec.  1065.510 by revising paragraphs (a) introductory text, 
(b) introductory text, (b)(4) through (6), (c)(2), (d) introductory 
text, (d)(4), (d)(5)(iii), and (g)(2) to read as follows:

Sec.  1065.510  Engine mapping.

    (a) Applicability, scope, and frequency. An engine map is a data 
set that consists of a series of paired data points that represent the 
maximum brake torque versus engine speed, measured at the engine's 
primary output shaft. Map your engine if the standard-setting part 
requires engine mapping to generate a duty cycle for your engine 
configuration. Map your engine while it is connected to a dynamometer 
or other device that can absorb work output from the engine's primary 
output shaft according to Sec.  1065.110. Configure any auxiliary work 
inputs and outputs such as hybrid, turbo-compounding, or thermoelectric 
systems to represent their in-use configurations, and use the same 
configuration for emission testing. See Figure 1 of Sec.  1065.210. 
This may involve configuring initial states of charge and rates and 
times of auxiliary-work inputs and outputs. We recommend that you 
contact the EPA Program Officer before testing to determine how you 
should configure any auxiliary-work inputs and outputs. If your engine 
has an auxiliary emission control device to reduce torque output that 
may activate during engine mapping, turn it off before mapping. Use the 
most recent engine map to transform a normalized duty cycle from the 
standard-setting part to a reference duty cycle specific to your 
engine. Normalized duty cycles are specified in the standard-setting 
part. You may update an engine map at any time by repeating the engine-
mapping procedure. You must map or re-map an engine before a test if 
any of the following apply:
* * * * *
    (b) Mapping variable-speed engines. Map variable-speed engines 
using the procedure in this paragraph (b). Note that under Sec.  
1065.10(c) we may allow or require you to use ``other procedures'' if 
the specified procedure results in unrepresentative testing or if your 
engine cannot be tested using the specified procedure. If the engine 
has a user-adjustable idle speed setpoint, you may set it to its 
minimum adjustable value for this mapping procedure and the resulting 
map may be used for any test, regardless of where it is set for running 
each test.
* * * * *
    (4) Operate the engine at the minimum mapped speed. A minimum 
mapped speed equal to (95 1)% of its warm idle speed 
determined in paragraph (b)(3) of this section may be used for any 
engine or test. A higher minimum mapped speed may be used if all the 
duty cycles that the engine is subject to have a minimum reference 
speed higher than the warm idle speed determined in paragraph (b)(3) of 
this section. In this case you may use a minimum mapped speed equal to 
(95 1)% of the lowest minimum reference speed in all the 
duty cycles the engine is subject to. Set operator demand to maximum 
and control engine speed at this minimum mapped speed for at least 15 
seconds. Set operator demand to maximum and control engine speed at (95 
1)% of its warm idle speed determined in paragraph 
(b)(3)(i) of this section for at least 15 seconds.
    (5) Perform a continuous or discrete engine map as described in 
paragraphs (b)(5)(i) or (ii) of this section. A continuous engine map 
may be used for any engine. A discrete engine map may be used for 
engines subject only to steady-state duty cycles. Use linear 
interpolation between the series of points generated by either of these 
maps to determine intermediate torque values. Use the series of points 
generated by either of these maps to generate the power map as 
described in paragraph (e) of this section.
    (i) For continuous engine mapping, begin recording mean feedback 
speed and torque at 1 Hz or more frequently and increase speed at a 
constant rate such that it takes (4 to 6) min to sweep from the minimum 
mapped speed described in paragraphs (b)(4) of this section to the 
check point speed described in paragraph (b)(5)(iii) of this section. 
Use good engineering judgment to determine when to stop recording data 
to ensure that the sweep is complete. In most cases, this means that 
you can stop the sweep at any point after the power falls to 50% of the 
maximum value.
    (ii) For discrete engine mapping, select at least 20 evenly spaced 
setpoints from the minimum mapped speed described in paragraph (b)(4) 
of this section to the check point speed described in paragraph 
(b)(5)(iii) of this section. At each setpoint, stabilize speed and 
allow torque to stabilize. We recommend that you stabilize an engine 
for at least 15 seconds at each setpoint and record the mean feedback 
speed and torque of the last (4 to 6) seconds. Record the mean speed 
and torque at each setpoint.
    (iii) The check point speed of the map is the highest speed above 
maximum power at which 50% of maximum power occurs. If this speed is 
unsafe or unachievable (e.g., for ungoverned engines or engines that do 
not operate at that point), use good engineering judgment to map up to 
the maximum safe speed or maximum achievable speed. For discrete 
mapping, if the engine cannot be mapped to the check point speed, make 
sure the map includes at least 20 points from 95% of warm idle to the 
maximum mapped speed. For continuous mapping, if the engine cannot be 
mapped to the check point speed, verify that the sweep time from 95% of 
warm idle to the maximum mapped speed is (4 to 6) min.
    (iv) Note that under Sec.  1065.10(c)(1) we may allow you to 
disregard portions of the map when selecting maximum test speed if the 
specified procedure would result in a duty cycle that does not 
represent in-use operation.
    (6) Determine warm high-idle speed for engines with a high-speed 
governor. You may skip this if the engine is not subject to transient 
testing with a duty cycle that includes reference speed values above 
100%. You may use a manufacturer-declared warm high-idle speed if the 
engine is electronically governed. For engines with a high-speed 
governor that regulates speed by disabling and enabling fuel or 
ignition at two manufacturer-specified speeds, declare the middle of 
this specified speed range as the warm high-idle speed. You may 
alternatively measure warm high-idle speed using the following 
procedure:
    (i) Run an operating point targeting zero torque.
    (A) Set operator demand to maximum and use the dynamometer to 
target zero

[[Page 4677]]

torque on the engine's primary output shaft.
    (B) Wait for the engine governor and dynamometer to stabilize. We 
recommend that you stabilize for at least 15 seconds.
    (C) Record 1 Hz means of the feedback speed and torque for at least 
30 seconds. You may record means at a higher frequency as long as there 
are no gaps in the recorded data. For engines with a high-speed 
governor that regulates speed by disabling and enabling fuel or 
ignition, you may need to extend this stabilization period to include 
at least one disabling event at the higher speed and one enabling event 
at the lower speed.
    (D) Determine if the feedback speed is stable over the recording 
period. The feedback speed is considered stable if all the recorded 1 
Hz means are within 2% of the mean feedback speed over the 
recording period. If the feedback speed is not stable because of the 
dynamometer, void the results and repeat measurements after making any 
necessary corrections. You may void and repeat the entire map sequence, 
or you may void and replace only the results for establishing warm 
high-idle speed; use good engineering judgment to warm-up the engine 
before repeating measurements.
    (E) If the feedback speed is stable, use the mean feedback speed 
over the recording period as the measured speed for this operating 
point.
    (F) If the feedback speed is not stable because of the engine, 
determine the mean as the value representing the midpoint between the 
observed maximum and minimum recorded feedback speed.
    (G) If the mean feedback torque over the recording period is within 
(0 1)% of Tmaxmapped, use the measured speed for 
this operating point as the warm high-idle speed. Otherwise, continue 
testing as described in paragraph (b)(6)(ii) of this section.
    (ii) Run a second operating point targeting a positive torque. 
Follow the same procedure in paragraphs (b)(6)(i)(A) through (F) of 
this section, except that the dynamometer is set to target a torque 
equal to the mean feedback torque over the recording period from the 
previous operating point plus 20% of Tmax mapped.
    (iii) Use the mean feedback speed and torque values from paragraphs 
(b)(6)(i) and (ii) of this section to determine the warm high-idle 
speed. If the two recorded speed values are the same, use that value as 
the warm high-idle-speed. Otherwise, use a linear equation passing 
through these two speed-torque points and extrapolate to solve for the 
speed at zero torque and use this speed intercept value as the warm 
high-idle speed.
    (iv) You may use a manufacturer-declared Tmax instead of 
the measured Tmax mapped. If you do this, you may also 
measure the warm high-idle speed as described in this paragraph (b)(6) 
before running the operating point and speed sweeps specified in 
paragraphs (b)(4) and (5) of this section.
* * * * *
    (c) * * *
    (2) Map the amount of negative torque required to motor the engine 
by repeating paragraph (b) of this section with minimum operator 
demand, as applicable. You may start the negative torque map at either 
the minimum or maximum speed from paragraph (b) of this section.
* * * * *
    (d) Mapping constant-speed engines. Map constant-speed engines 
using the procedure in this paragraph (d). When testing without a 
motoring dynamometer (e.g., eddy-current or water-brake dynamometer or 
any device that is already installed on a vehicle, equipment, or 
vessel) operate these devices over the no-load operating points in the 
procedure as close to no-load as possible.
* * * * *
    (4) With the governor or simulated governor controlling speed using 
operator demand, operate the engine at the no-load, or minimum 
achievable load, governed speed (at high speed, not low idle) for at 
least 15 seconds.
    (5) * * *
    (iii) For any isochronous governed (0% speed droop) constant-speed 
engine, you may map the engine with two points as described in this 
paragraph (d)(5)(iii). After stabilizing at the no-load, or minimum 
achievable load, governed speed in paragraph (d)(4) of this section, 
record the mean feedback speed and torque. Continue to operate the 
engine with the governor or simulated governor controlling engine speed 
using operator demand, and control the dynamometer to target a speed of 
99.5% of the recorded mean no-load governed speed. Allow speed and 
torque to stabilize. Record the mean feedback speed and torque. Record 
the target speed. The absolute value of the speed error (the mean 
feedback speed minus the target speed) must be no greater than 0.1% of 
the recorded mean no-load governed speed. From this series of two mean 
feedback speed and torque values, use linear interpolation to determine 
intermediate values. Use this series of two mean feedback speeds and 
torques to generate a power map as described in paragraph (e) of this 
section. Note that the measured maximum test torque as determined in 
Sec.  1065.610(b)(1) will be the mean feedback torque recorded on the 
second point.
* * * * *
    (g) * * *
    (2) The purpose of the mapping procedure in this paragraph (g) is 
to determine the maximum torque available at each speed, such as what 
might occur during transient operation with a fully charged RESS. Use 
one of the following methods to generate a hybrid-active map:
    (i) Perform an engine map by using a series of continuous sweeps to 
cover the engine's full range of operating speeds. Prepare the engine 
for hybrid-active mapping by ensuring that the RESS state of charge is 
representative of normal operation. Perform the sweep as specified in 
paragraph (b)(5)(i) of this section, but stop the sweep to charge the 
RESS when the power measured from the RESS drops below the expected 
maximum power from the RESS by more than 2% of total system power 
(including engine and RESS power). Unless good engineering judgment 
indicates otherwise, assume that the expected maximum power from the 
RESS is equal to the measured RESS power at the start of the sweep 
segment. For example, if the 3-second rolling average of total engine-
RESS power is 200 kW and the power from the RESS at the beginning of 
the sweep segment is 50 kW, once the power from the RESS reaches 46 kW, 
stop the sweep to charge the RESS. Note that this assumption is not 
valid where the hybrid motor is torque-limited. Calculate total system 
power as a 3-second rolling average of instantaneous total system 
power. After each charging event, stabilize the engine for 15 seconds 
at the speed at which you ended the previous segment with operator 
demand set to maximum before continuing the sweep from that speed. 
Repeat the cycle of charging, mapping, and recharging until you have 
completed the engine map. You may shut down the system or include other 
operation between segments to be consistent with the intent of this 
paragraph (g)(2)(i). For example, for systems in which continuous 
charging and discharging can overheat batteries to an extent that 
affects performance, you may operate the engine at zero power from the 
RESS for enough time after the system is recharged to allow the 
batteries to cool. Use good engineering judgment to smooth the torque 
curve to eliminate discontinuities between map intervals.

[[Page 4678]]

    (ii) Perform an engine map by using discrete speeds. Select map 
setpoints at intervals defined by the ranges of engine speed being 
mapped. From 95% of warm idle speed to 90% of the expected maximum test 
speed, select setpoints that result in a minimum of 13 equally spaced 
speed setpoints. From 90% to 110% of expected maximum test speed, 
select setpoints in equally spaced intervals that are nominally 2% of 
expected maximum test speed. Above 110% of expected maximum test speed, 
select setpoints based on the same speed intervals used for mapping 
from 95% warm idle speed to 90% maximum test speed. You may stop 
mapping at the highest speed above maximum power at which 50% of 
maximum power occurs. We refer to the speed at 50% power as the check 
point speed as described in paragraph (b)(5)(iii) of this section. 
Stabilize engine speed at each setpoint, targeting a torque value at 
70% of peak torque at that speed without hybrid-assist. Make sure the 
engine is fully warmed up and the RESS state of charge is within the 
normal operating range. Snap the operator demand to maximum, operate 
the engine there for at least 10 seconds, and record the 3-second 
rolling average feedback speed and torque at 1 Hz or higher. Record the 
peak 3-second average torque and 3-second average speed at that point. 
Use linear interpolation to determine intermediate speeds and torques. 
Follow Sec.  1065.610(a) to calculate the maximum test speed. Verify 
that the measured maximum test speed falls in the range from 92 to 108% 
of the estimated maximum test speed. If the measured maximum test speed 
does not fall in this range, repeat the map using the measured value of 
maximum test speed.
* * * * *

0
237. Amend Sec.  1065.512 by revising paragraph (b)(1) to read as 
follows:

Sec.  1065.512  Duty cycle generation.

* * * * *
    (b) * * *
    (1) Engine speed for variable-speed engines. For variable-speed 
engines, normalized speed may be expressed as a percentage between warm 
idle speed, fnidle, and maximum test speed, 
fntest, or speed may be expressed by referring to a defined 
speed by name, such as ``warm idle,'' ``intermediate speed,'' or ``A,'' 
``B,'' or ``C'' speed. Section 1065.610 describes how to transform 
these normalized values into a sequence of reference speeds, 
fnref. Running duty cycles with negative or small normalized 
speed values near warm idle speed may cause low-speed idle governors to 
activate and the engine torque to exceed the reference torque even 
though the operator demand is at a minimum. In such cases, we recommend 
controlling the dynamometer so it gives priority to follow the 
reference torque instead of the reference speed and let the engine 
govern the speed. Note that the cycle-validation criteria in Sec.  
1065.514 allow an engine to govern itself. This allowance permits you 
to test engines with enhanced-idle devices and to simulate the effects 
of transmissions such as automatic transmissions. For example, an 
enhanced-idle device might be an idle speed value that is normally 
commanded only under cold-start conditions to quickly warm up the 
engine and aftertreatment devices. In this case, negative and very low 
normalized speeds will generate reference speeds below this higher 
enhanced-idle speed. You may do either of the following when using 
enhanced-idle devices:
    (i) Control the dynamometer so it gives priority to follow the 
reference torque, controlling the operator demand so it gives priority 
to follow reference speed and let the engine govern the speed when the 
operator demand is at minimum.
    (ii) While running an engine where the ECM broadcasts an enhanced-
idle speed that is above the denormalized speed, use the broadcast 
speed as the reference speed. Use these new reference points for duty-
cycle validation. This does not affect how you determine denormalized 
reference torque in paragraph (b)(2) of this section.
    (iii) If an ECM broadcast signal is not available, perform one or 
more practice cycles to determine the enhanced-idle speed as a function 
of cycle time. Generate the reference cycle as you normally would but 
replace any reference speed that is lower than the enhanced-idle speed 
with the enhanced-idle speed. This does not affect how you determine 
denormalized reference torque in paragraph (b)(2) of this section.
* * * * *

0
238. Amend Sec.  1065.514 by revising paragraph (d) to read as follows

Sec.  1065.514  Cycle-validation criteria for operation over specified 
duty cycles.

* * * * *
    (d) Omitting additional points. Besides engine cranking, you may 
omit additional points from cycle-validation statistics as described in 
the following table:

Table 1 to Paragraph (d) of Sec.   1065.514--Permissible Criteria for Omitting Points From Duty-Cycle Regression
                                                   Statistics
----------------------------------------------------------------------------------------------------------------
 When operator demand is at its . .
                 .                        you may omit . . .                         if . . .
----------------------------------------------------------------------------------------------------------------
                For reference duty cycles that are specified in terms of speed and torque (f, T)
----------------------------------------------------------------------------------------------------------------
minimum............................  power and torque...........  Tref < 0% (motoring).
minimum............................  power and speed............  fnref = 0% (idle speed) and Tref = 0% (idle
                                                                   torque) and Tref-(2% [middot] Tmax mapped) <
                                                                   T < Tref + (2% [middot] Tmax mapped).
minimum............................  power and speed............  fnref < enhanced-idle speed \a\ and Tref > 0%.
minimum............................  power and either torque or   fn > fnref or T > Tref but not if fn > (fnref
                                      speed.                       [middot] 102%) and T > Tref + (2% [middot]
                                                                   Tmax mapped).
maximum............................  power and either torque or   fn < fnref or T < Tref but not if fn < (fnref
                                      speed.                       [middot] 98%) and T < Tref-(2% [middot] Tmax
                                                                   mapped).
----------------------------------------------------------------------------------------------------------------
                 For reference duty cycles that are specified in terms of speed and power (f, P)
----------------------------------------------------------------------------------------------------------------
minimum............................  power and torque...........  Pref < 0% (motoring).
minimum............................  power and speed............  fnref = 0% (idle speed) and Pref = 0% (idle
                                                                   power) and Pref-(2% [middot] Pmax mapped) < P
                                                                   < Pref + (2% [middot] Pmax mapped).
minimum............................  power and either torque or   fn > fnref or P > Pref but not if fn > (fnref
                                      speed.                       [middot] 102%) and P > Pref + (2% [middot]
                                                                   Pmax mapped).
maximum............................  power and either torque or   fn < fnref or P < Pref but not if fn < (fnref
                                      speed.                       [middot] 98%) and P < Pref-(2% [middot] Pmax
                                                                   mapped).
----------------------------------------------------------------------------------------------------------------
\a\ Determine enhanced-idle speed from ECM broadcast or a practice cycle.

[[Page 4679]]

* * * * *

0
239. Amend Sec.  1065.530 by revising paragraph (g)(5) introductory 
text to read as follows:

Sec.  1065.530  Emission test sequence.

* * * * *
    (g) * * *
    (5) If you perform the optional carbon balance error verification, 
verify carbon balance error as specified in the standard-setting part 
and Sec.  1065.543. Calculate and report the three carbon balance error 
quantities for each test interval; carbon mass absolute error for a 
test interval, [epsi]aC, carbon mass rate 
absolute error for a test interval, [epsi]aCrate, 
and carbon mass relative error for a test interval, 
[epsi]rC. For duty cycles with multiple test 
intervals, you may calculate and report the composite carbon mass 
relative error, [epsi]rCcomp, for the whole duty 
cycle. If you report [epsi]rCcomp, you must still 
calculate and report [epsi]aC, 
[epsi]aCrate, and [epsi]rC 
for each test interval.
* * * * *

0
240. Amend Sec.  1065.543 by revising paragraphs (a) and (b) to read as 
follows:

Sec.  1065.543  Carbon balance error verification.

    (a) This optional carbon balance error verification compares 
independently calculated quantities of carbon flowing into and out of 
an engine system. The engine system includes aftertreatment devices as 
applicable. Calculating carbon intake considers carbon-carrying streams 
flowing into the system, including intake air, fuel, and optionally DEF 
or other fluids. Carbon flow out of the system comes from exhaust 
emission calculations. Note that this verification is not valid if you 
calculate exhaust molar flow rate using fuel rate and chemical balance 
as described in Sec.  1065.655(f)(3) because carbon flows into and out 
of the system are not independent. Use good engineering judgment to 
ensure that carbon mass in and carbon mass out data signals align.
    (b) Perform the carbon balance error verification after emission 
sampling is complete for a test sequence as described in Sec.  
1065.530(g)(5). Testing must include measured values as needed to 
determine intake air, fuel flow, and carbon-related gaseous exhaust 
emissions. You may optionally account for the flow of carbon-carrying 
fluids other than intake air and fuel into the system. Perform carbon 
balance error verification as follows:
    (1) Calculate carbon balance error quantities as described in Sec.  
1065.643. The three quantities for individual test intervals are carbon 
mass absolute error, [epsi]aC, carbon mass rate 
absolute error, [epsi]aCrate, and carbon mass 
relative error, [epsi]rC. Determine 
[epsi]aC, [epsi]aCrate, and 
[epsi]rC for all test intervals. You may 
determine composite carbon mass relative error, 
[epsi]rCcomp, as a fourth quantity that 
optionally applies for duty cycles with multiple test intervals.
    (2) You meet the carbon balance error verification for a test 
sequence if all test intervals pass the test-interval criteria. A test 
interval passes if at least one of the absolute values of the three 
carbon balance error quantities for test intervals, 
[epsi]aC, [epsi]aCrate, and 
[epsi]rC, is at or below its respective limit 
value in paragraphs (b)(2)(i) through (iii) of this section. You meet 
the carbon balance error verification for a duty cycle with multiple 
test intervals if the duty cycle passes the duty-cycle criterion. A 
duty cycle passes if the absolute value of the composite carbon mass 
relative error quantity, [epsi]rCcomp, is at or 
below the limit value in paragraph (b)(2)(iii) of this section. Unless 
specified otherwise in the standard-setting part, if verification fails 
for a test sequence, you may repeat the entire test sequence or repeat 
individual test intervals as described in Sec.  1065.526.
    (i) Calculate the carbon mass absolute error limit, 
L[egr]aC, in grams to three decimal places for comparison to 
the absolute value of [epsi]aC, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.104

Where:

c = power-specific carbon mass absolute error coefficient = 0.007 g/
kW.
Pmax = maximum power from the engine map generated 
according to Sec.  1065.510. If measured Pmax is not 
available, use a manufacturer-declared value for Pmax.

Example:

c = 0.007 g/kW
Pmax = 230.0 kW
L[egr]aC = 0.007 [middot] 230.0
L[egr]aC = 1.610 g

    (ii) Calculate the carbon mass rate absolute error limit, 
L[egr]aCrate, in grams per hour to three decimal places for comparison 
to the absolute value of [epsi]aCrate, using the 
following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.105

Where:

d = power-specific carbon mass rate absolute error coefficient = 
0.31 g/(kW[middot]hr).
Pmax = maximum power from the engine map generated 
according to Sec.  1065.510. If measured Pmax is not 
available, use a manufacturer-declared value for Pmax.

Example:

d = 0.31 g/(kW[middot]hr)
Pmax = 230.0 kW
L[egr]aCrate = 0.31.230.0
L[egr]aCrate = 71.300 g/hr

    (iii) The carbon mass relative error limit, L[epsi]rC, 
is 0.020 for comparison to the absolute value of 
[epsi]rC, and to the absolute value of 
[epsi]rCcomp.
* * * * *

0
241. Amend Sec.  1065.545 by revising paragraphs (a) and (b) 
introductory text to read as follows:

Sec.  1065.545  Verification of proportional flow control for batch 
sampling.

* * * * *
    (a) For any pair of sample and total flow rates, use continuous 
recorded data or 1 Hz means. Total flow rate means the raw exhaust flow 
rate for raw exhaust sampling and the dilute exhaust flow rate for CVS 
sampling. For each test interval, determine the standard error of the 
estimate, SEE, of the sample flow rate versus the total flow rate as 
described in Sec.  1065.602, forcing the intercept to zero. Determine 
the mean sample flow rate over each test interval as described in Sec.  
1065.602. For each test interval, demonstrate that SEE is at or below 
3.5% of the mean sample flow rate.
    (b) For any pair of sample and total flow rates, use continuous 
recorded data or 1 Hz means. Total flow rate means the raw exhaust flow 
rate for raw exhaust sampling and the dilute exhaust flow rate for CVS 
sampling. For each test interval, demonstrate that each flow rate is 
constant within 2.5% of its respective mean or target flow 
rate. You may use the following options instead of recording the 
respective flow rate of each type of meter:
* * * * *

0
242. Amend Sec.  1065.610 by:
0
a. Revising the introductory text, paragraphs (a) introductory text, 
(a)(1) introductory text, and (a)(3).
0
b. Removing paragraph (a)(4).
0
c. Revising paragraphs (b) introductory text, (b)(1) introductory text, 
(b)(2) and (3), and (c)(2).

    The revisions read as follows:

Sec.  1065.610  Duty cycle generation.

    This section describes how to generate duty cycles that are 
specific to your engine, based on the normalized duty cycles in the 
standard-setting part. During an emission test, use a duty cycle that 
is specific to your engine to command engine speed, torque, and power, 
as applicable, using an engine dynamometer and an engine operator 
demand. Paragraphs (a) and (b) of this section describe how to 
``normalize'' your engine's map to determine the maximum test speed or 
torque for your

[[Page 4680]]

engine. The rest of this section describes how to use these values to 
``denormalize'' the duty cycles in the standard-setting parts, which 
are all published on a normalized basis. Thus, the term ``normalized'' 
in paragraphs (a) and (b) of this section refers to different values 
than it does in the rest of the section.
    (a) Maximum test speed, [fnof]ntest. For variable-speed engines, 
determine [fnof]ntest from the torque and power maps, 
generated according to Sec.  1065.510, as follows:
    (1) Determine a measured value for [fnof]ntest as 
follows:
* * * * *
    (3) Transform normalized speeds to reference speeds according to 
paragraph (c) of this section by using the measured maximum test speed 
determined according to paragraphs (a)(1) and (2) of this section--or 
use your declared maximum test speed, as allowed in Sec.  1065.510.
    (b) Maximum test torque, Ttest. For constant-speed engines, 
determine Ttest from the torque and power-versus-speed maps, 
generated according to Sec.  1065.510, as follows:
    (1) For constant speed engines mapped using the methods in Sec.  
1065.510(d)(5)(i) or (ii), determine a measured value for 
Ttest as follows:
* * * * *
    (2) For constant speed engines using the two-point mapping method 
in Sec.  1065.510(d)(5)(iii), you may follow paragraph (a)(1) of this 
section to determine the measured Ttest, or you may use the 
measured torque of the second point as the measured Ttest 
directly.
    (3) Transform normalized torques to reference torques according to 
paragraph (d) of this section by using the measured maximum test torque 
determined according to paragraph (b)(1) or (2) of this section--or use 
your declared maximum test torque, as allowed in Sec.  1065.510.
    (c) * * *
    (2) A, B, C, and D speeds. If your normalized duty cycle specifies 
speeds as A, B, C, or D values, use your power-versus-speed curve to 
determine the lowest speed below maximum power at which 50% of maximum 
power occurs. Denote this value as nlo. Take nlo 
to be warm idle speed if all power points at speeds below the maximum 
power speed are higher than 50% of maximum power. Also determine the 
highest speed above maximum power at which 70% of maximum power occurs. 
Denote this value as nhi. If all power points at speeds 
above the maximum power speed are higher than 70% of maximum power, 
take nhi to be the declared maximum safe engine speed or the 
declared maximum representative engine speed, whichever is lower. Use 
nhi and nlo to calculate reference values for A, 
B, C, or D speeds as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.106

Example:

nlo = 1005 r/min
nhi = 2385 r/min
[fnof]nrefA = 0.25 [middot] (2385 - 1005) + 1005
[fnof]nrefB = 0.50 [middot] (2385 - 1005) + 1005
[fnof]nrefC = 0.75 [middot] (2385 - 1005) + 1005
[fnof]nrefD = 0.15 [middot] (2385 - 1005) + 1005
[fnof]nrefA = 1350 r/min
[fnof]nrefB = 1695 r/min
[fnof]nrefC = 2040 r/min
[fnof]nrefD = 1212 r/min
* * * * *

0
243. Amend Sec.  1065.630 by revising paragraphs (a) and (b) 
introductory text to read as follows:

Sec.  1065.630  Local acceleration of gravity.

    (a) The acceleration of Earth's gravity, ag, varies 
depending on the test location. Determine ag at your 
location by entering latitude, longitude, and elevation data into the 
U.S. National Oceanographic and Atmospheric Administration's surface 
gravity prediction website at https://geodesy.noaa.gov/cgi-bin/grav_pdx.prl.
    (b) If the website specified in paragraph (a) of this section is 
unavailable, or the test location is outside of the continental United 
States, you may calculate ag for your latitude as follows:
* * * * *

0
244. Amend Sec.  1065.643 by revising paragraph (d) to read as follows:

Sec.  1065.643  Carbon balance error verification calculations.

* * * * *
    (d) Carbon balance error quantities. Calculate carbon balance error 
quantities as follows:
    (1) Calculate carbon mass absolute error, [epsi]aC, for 
a test interval as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.107

Where:

mCexh = mass of carbon in exhaust emissions over the test 
interval as determined in paragraph (d) of this section.
mCfluid = mass of carbon in all the carbon-carrying fluid 
streams flowing into the system over the test interval as determined 
in paragraph (a) of this section.
mCair = mass of carbon in the intake air flowing into the 
system over the test interval as determined in paragraph (b) of this 
section.

Example:

mCexh = 1247.2 g
mCfluid = 975.3 g
mCair = 278.6 g
[epsi]aC = 1247.2 - 975.3 - 278.6
[epsi]aC = -6.7 g

    (2) Calculate carbon mass rate absolute error, 
[epsi]aCrate, for a test interval as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.108

Where:

t = duration of the test interval.

Example:

[epsi]aC = -6.7 g
    t = 1202.2 s = 0.3339 hr
    [GRAPHIC] [TIFF OMITTED] TR24JA23.109
    
[epsi]aCrate = -20.065 g/hr

    (3) Calculate carbon mass relative error, [epsi]rC, for 
a test interval as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.110

Example:

[epsi]aC = -6.7 g
mCfluid = 975.3 g
mCair = 278.6 g
[GRAPHIC] [TIFF OMITTED] TR24JA23.111

[epsi]rC = -0.0053

    (4) Calculate composite carbon mass relative error, 
[epsi]rCcomp, for a duty cycle with multiple test intervals 
as follows:
    (i) Calculate [epsi]rCcomp using the following equation:

[[Page 4681]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.112

Where:

i = an indexing variable that represents one test interval.
N = number of test intervals.
WF = weighting factor for the test interval as defined in the 
standard-setting part.
mCexh = mass of carbon in exhaust emissions over the test 
interval as determined in paragraph (c) of this section.
mCfluid = mass of carbon in all the carbon-carrying fluid 
streams that flowed into the system over the test interval as 
determined in paragraph (a) of this section.
mCair = mass of carbon in the intake air that flowed into 
the system over the test interval as determined in paragraph (b) of 
this section.
t = duration of the test interval. For duty cycles with multiple 
test intervals of a prescribed duration, such as cold-start and hot-
start transient cycles, set t = 1 for all test intervals. For 
discrete-mode steady-state duty cycles with multiple test intervals 
of varying duration, set t equal to the actual duration of each test 
interval.

    (ii) The following example illustrates calculation of 
[epsi]rCcomp, for cold-start and hot-start transient cycles:

N = 2
WF1 = \1/7\
WF2 = \6/7\
mCexh1 = 1255.3 g
mCexh2 = 1247.2 g
mCfluid1 = 977.8 g
mCfluid2 = 975.3 g
mCair1 = 280.2 g
mCair2 = 278.6 g
[GRAPHIC] [TIFF OMITTED] TR24JA23.113

[epsi]rCcomp = -0.0049

    (iii) The following example illustrates calculation of 
[epsi]rCcomp for multiple test intervals with varying 
duration, such as discrete-mode steady-state duty cycles:

N = 2
WF1 = 0.85
WF2 = 0.15
mCexh1 = 2.873 g
mCexh2 = 0.125 g
mCfluid1 = 2.864 g
mCfluid2 = 0.095 g
mCair1 = 0.023 g
mCair2 = 0.024 g
t1 = 123 s
t2 = 306 s
[GRAPHIC] [TIFF OMITTED] TR24JA23.114

[epsi]rCcomp = -0.0047

0
245. Amend Sec.  1065.650 by revising paragraphs (a), (c)(2)(i), 
(c)(3), (c)(4)(i), (c)(6), (d)(7), (e)(1) and (2), (f)(1) and (2), and 
(g)(1) and (2) to read as follows:

Sec.  1065.650  Emission calculations.

    (a) General. Calculate brake-specific emissions over each 
applicable duty cycle or test interval. For test intervals with zero 
work (or power), calculate the emission mass (or mass rate), but do not 
calculate brake-specific emissions. Unless specified otherwise, for the 
purposes of calculating and reporting emission mass (or mass rate), do 
not alter any negative values of measured or calculated quantities. You 
may truncate negative values in chemical balance quantities listed in 
Sec.  1065.655(c) to facilitate convergence. For duty cycles with 
multiple test intervals, refer to the standard-setting part for 
calculations you need to determine a composite result, such as a 
calculation that weights and sums the results of individual test 
intervals in a duty cycle. If the standard-setting part does not 
include those calculations, use the equations in paragraph (g) of this 
section. This section is written based on rectangular integration, 
where each indexed value (i.e., ``i'') represents (or 
approximates) the mean value of the parameter for its respective time 
interval, delta-t. You may also integrate continuous signals using 
trapezoidal integration consistent with good engineering judgment.
* * * * *
    (c) * * *
    (2) * * *
    (i) Varying flow rate. If you continuously sample from a varying 
exhaust flow rate, time align and then multiply concentration 
measurements by the flow rate from which you extracted it. We consider 
the following to be examples of varying flows that require a continuous 
multiplication of concentration times molar flow rate: raw exhaust, 
exhaust diluted with a constant flow rate of dilution air, and CVS 
dilution with a CVS flow meter that does not have an upstream heat 
exchanger or electronic flow control. This multiplication results in 
the flow rate of the emission itself. Integrate the emission flow rate 
over a test interval to determine the total emission. If the total 
emission is a molar quantity, convert this quantity to a mass by 
multiplying it by its molar mass, M. The result is the mass of the 
emission, m. Calculate m for continuous sampling with variable flow 
using the following equations:
[GRAPHIC] [TIFF OMITTED] TR24JA23.115

Where:

[[Page 4682]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.116

Example:

MNMHC = 13.875389 g/mol
N = 1200
xNMHC1 = 84.5 [micro]mol/mol = 84.5 [middot] 
10-\6\ mol/mol
xNMHC2 = 86.0 [micro]mol/mol = 86.0 [middot] 
10-\6\ mol/mol
nexh1 = 2.876 mol/s
nexh2 = 2.224 mol/s
[fnof]record = 1 Hz

    Using Eq. 1065.650-5,

[Delta]t = 1/1 = 1 s
mNMHC = 13.875389 [middot] (84.5 [middot] 10-\6\ 
[middot] 2.876 + 86.0 [middot] 10-\6\ [middot] 2.224 + . . . 
+ xNMHC1200 [middot] nexh) [middot] 1
mNMHC = 25.23 g
* * * * *
    (3) Batch sampling. For batch sampling, the concentration is a 
single value from a proportionally extracted batch sample (such as a 
bag, filter, impinger, or cartridge). In this case, multiply the mean 
concentration of the batch sample by the total flow from which the 
sample was extracted. You may calculate total flow by integrating a 
varying flow rate or by determining the mean of a constant flow rate, 
as follows:
    (i) Varying flow rate. If you collect a batch sample from a varying 
exhaust flow rate, extract a sample proportional to the varying exhaust 
flow rate. We consider the following to be examples of varying flows 
that require proportional sampling: raw exhaust, exhaust diluted with a 
constant flow rate of dilution air, and CVS dilution with a CVS flow 
meter that does not have an upstream heat exchanger or electronic flow 
control. Integrate the flow rate over a test interval to determine the 
total flow from which you extracted the proportional sample. Multiply 
the mean concentration of the batch sample by the total flow from which 
the sample was extracted to determine the total emission. If the total 
emission is a molar quantity, convert this quantity to a mass by 
multiplying it by its molar mass, M. The result is the total emission 
mass, m. In the case of PM emissions, where the mean PM concentration 
is already in units of mass per mole of exhaust, simply multiply it by 
the total flow. The result is the total mass of PM, mPM. 
Calculate m for each constituent as follows:
    (A) Calculate m for measuring gaseous emission constituents with 
sampling that results in a molar concentration, x, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.117

Example:

MNOX = 46.0055 g/mol
N = 9000
x = 85.6 [micro]mol/mol = 85.6 [middot] 10-\6\ mol/mol
ndexh1 = 25.534 mol/s
ndexh2 = 26.950 mol/s
[fnof]record = 5 Hz

    Using Eq. 1065.650-5:

[Delta]t = 1/5 = 0.2 s
mNOX 46.0055 [middot] 85.6 [middot] 10-\6\ 
[middot] (25.534 + 26.950+ . . . +
nexh9000) [middot] 0.2
mNOX = 4.201 g
    (B) Calculate m for sampling PM or any other analysis of a batch 
sample that yields a mass per mole of exhaust, M, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.118

    (ii) Proportional or constant flow rate. If you batch sample from a 
constant exhaust flow rate, extract a sample at a proportional or 
constant flow rate. We consider the following to be examples of 
constant exhaust flows: CVS diluted exhaust with a CVS flow meter that 
has either an upstream heat exchanger, electronic flow control, or 
both. Determine the mean molar flow rate from which you extracted the 
sample. Multiply the mean concentration of the batch sample by the mean 
molar flow rate of the exhaust from which the sample was extracted to 
determine the total emission and multiply the result by the time of the 
test interval. If the total emission is a molar quantity, convert this 
quantity to a mass by multiplying it by its molar mass, M. The result 
is the total emission mass, m. In the case of PM emissions, where the 
mean PM concentration is already in units of mass per mole of exhaust, 
simply multiply it by the total flow, and the result is the total mass 
of PM, mPM. Calculate m for each constituent as follows:
    (A) Calculate m for measuring gaseous emission constituents with 
sampling that results in a molar concentration, x, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.119

    (B) Calculate m for sampling PM or any other analysis of a batch 
sample that yields a mass per mole of exhaust, M, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.120

    (C) The following example illustrates a calculation of 
mPM:

MPM = 144.0 [micro]g/mol = 144.0 [middot] 10-\6\ 
g/mol
nidexh = 57.692 mol/s
[Delta]t = 1200 s
mPM = 144.0 [middot] 10-\6\ [middot] 57.692 
[middot] 1200
mPM = 9.9692 g

    (4) * * *
    (i) For sampling with a constant dilution ratio, DR, of diluted 
exhaust versus exhaust flow (e.g., secondary dilution for PM sampling), 
calculate m using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.121

Example:

mPMdil = 6.853 g
DR = 6:1
mPM = 6.853 [middot] 6
mPM = 41.118 g
* * * * *
    (6) Mass of NMNEHC. Determine the mass of NMNEHC using one of the 
following methods:
    (i) If the test fuel has less than 0.010 mol/mol of ethane and you 
omit the NMNEHC calculations as described in Sec.  1065.660(c)(1), take 
the corrected mass of NMNEHC to be 0.95 times the corrected mass of 
NMHC.
    (ii) If the test fuel has at least 0.010 mol/mol of ethane and you 
omit the NMNEHC calculations as described in Sec.  1065.660(c)(1), take 
the corrected mass of NMNEHC to be 1.0 times the corrected mass of 
NMHC.
    (d) * * *
    (7) Integrate the resulting values for power over the test 
interval. Calculate total work as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.122

Where:

W = total work from the primary output shaft.
Pi = instantaneous power from the primary output shaft over an 
interval i.
[GRAPHIC] [TIFF OMITTED] TR24JA23.123

Example:

N = 9000
[fnof]n1 = 1800.2 r/min
[fnof]n2 = 1805.8 r/min
T1 = 177.23 N[middot]m

[[Page 4683]]

T2 = 175.00 N[middot]m
Crev = 2[middot][pi] rad/r
Ct1 = 60 s/min
Cp = 1000 (N[middot]m[middot]rad/s)/kW
[fnof]record = 5 Hz
Ct2 = 3600 s/hr
[GRAPHIC] [TIFF OMITTED] TR24JA23.124

P1 = 33.41 kW
P2 = 33.09 kW

    Using Eq. 1065.650-5:

[Delta]t = 1/5 = 0.2 s
[GRAPHIC] [TIFF OMITTED] TR24JA23.125

W = 16.875 kW[middot]hr

* * * * *
    (e) * * *
    (1) To calculate, mi, multiply its mean concentration, x, by its 
corresponding mean molar flow rate, ni. If the result is a molar flow 
rate, convert this quantity to a mass rate by multiplying it by its 
molar mass, M. The result is the mean mass rate of the emission, mi. In 
the case of PM emissions, where the mean PM concentration is already in 
units of mass per mole of exhaust, simply multiply it by the mean molar 
flow rate, ni. The result is the mass rate of PM, mPM. 
Calculate mi using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.126

    (2) To calculate an engine's mean steady-state total power, P, add 
the mean steady-state power from all the work paths described in Sec.  
1065.210 that cross the system boundary including electrical power, 
mechanical shaft power, and fluid pumping power. For all work paths, 
except the engine's primary output shaft (crankshaft), the mean steady-
state power over the test interval is the integration of the net work 
flow rate (power) out of the system boundary divided by the period of 
the test interval. When power flows into the system boundary, the 
power/work flow rate signal becomes negative; in this case, include 
these negative power/work rate values in the integration to calculate 
the mean power from that work path. Some work paths may result in a 
negative mean power. Include negative mean power values from any work 
path in the mean total power from the engine rather than setting these 
values to zero. The rest of this paragraph (e)(2) describes how to 
calculate the mean power from the engine's primary output shaft. 
Calculate P using Eq. 1065.650-13, noting that P, fn, and T 
refer to mean power, mean rotational shaft frequency, and mean torque 
from the primary output shaft. Account for the power of simulated 
accessories according to Sec.  1065.110 (reducing the mean primary 
output shaft power or torque by the accessory power or torque). Set the 
power to zero during actual motoring operation (negative feedback 
torques), unless the engine was connected to one or more energy storage 
devices. Examples of such energy storage devices include hybrid 
powertrain batteries and hydraulic accumulators, like the ones denoted 
``Acc.'' and ``Batt.'' as illustrated in Figure 1 of Sec.  1065.210. 
Set the power to zero for modes with a zero reference load (0 
N[middot]m reference torque or 0 kW reference power). Include power 
during idle modes with simulated minimum torque or power.
[GRAPHIC] [TIFF OMITTED] TR24JA23.127

* * * * *
    (f) * * *
    (1) Total mass. To determine a value proportional to the total mass 
of an emission, determine total mass as described in paragraph (c) of 
this section, except substitute for the molar flow rate, n, or the 
total flow, n, with a signal that is linearly proportional to molar 
flow rate, n, or linearly proportional to total flow, n, as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.128

    (2) Total work. To calculate a value proportional to total work 
over a test interval, integrate a value that is proportional to power. 
Use information about the brake-specific fuel consumption of your 
engine, efuel, to convert a signal proportional to fuel flow 
rate to a signal proportional to power. To determine a signal 
proportional to fuel flow rate, divide a signal that is proportional to 
the mass rate of carbon products by the fraction of carbon in your 
fuel, wC. You may use a measured wC or you may 
use default values for a given fuel as described in Sec.  1065.655(e). 
Calculate the mass rate of carbon from the amount of carbon and water 
in the exhaust, which you determine with a chemical balance of fuel, 
DEF, intake air, and exhaust as described in Sec.  1065.655. In the 
chemical balance, you must use concentrations from the flow that 
generated the signal proportional to molar flow rate, ni, in paragraph 
(e)(1) of this section. Calculate a value proportional to total work as 
follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.129

Where:
[GRAPHIC] [TIFF OMITTED] TR24JA23.130

* * * * *
    (g) * * *
    (1) Use the following equation to calculate composite brake-
specific emissions for duty cycles with multiple test intervals all 
with prescribed durations, such as cold-start and hot-start transient 
cycles:
[GRAPHIC] [TIFF OMITTED] TR24JA23.131

Where:

i = test interval number.
N = number of test intervals.
WF = weighting factor for the test interval as defined in the 
standard-setting part.

[[Page 4684]]

m = mass of emissions over the test interval as determined in 
paragraph (c) of this section.
W = total work from the engine over the test interval as determined 
in paragraph (d) of this section.

Example:

N = 2
WF1 = 0.1428
WF2 = 0.8572
m1 = 70.125 g
m2 = 64.975 g
W1 = 25.783 kW[middot]hr
W2 = 25.783 kW[middot]hr
[GRAPHIC] [TIFF OMITTED] TR24JA23.132

eNOxcomp = 2.548 g/kW[middot]hr

    (2) Calculate composite brake-specific emissions for duty cycles 
with multiple test intervals that allow use of varying duration, such 
as discrete-mode steady-state duty cycles, as follows:
    (i) Use the following equation if you calculate brake-specific 
emissions over test intervals based on total mass and total work as 
described in paragraph (b)(1) of this section:
[GRAPHIC] [TIFF OMITTED] TR24JA23.133

Where:

i = test interval number.
N = number of test intervals.
WF = weighting factor for the test interval as defined in the 
standard-setting part.
m = mass of emissions over the test interval as determined in 
paragraph (c) of this section.
W = total work from the engine over the test interval as determined 
in paragraph (d) of this section.
t = duration of the test interval.

Example:

N = 2
WF1 = 0.85
WF2 = 0.15
m1 = 1.3753 g
m2 = 0.4135 g
t1 = 120 s
t2 = 200 s
W1 = 2.8375 kW [middot] hr
W2 = 0.0 kW [middot] hr
[GRAPHIC] [TIFF OMITTED] TR24JA23.134

eNOxcomp = 0.5001 g/kW[middot]hr

    (ii) Use the following equation if you calculate brake-specific 
emissions over test intervals based on the ratio of mass rate to power 
as described in paragraph (b)(2) of this section:
[GRAPHIC] [TIFF OMITTED] TR24JA23.135

Where:

i = test interval number.
N = number of test intervals.
WF = weighting factor for the test interval as defined in the 
standard-setting part.
mi = mean steady-state mass rate of emissions over the test interval 
as determined in paragraph (e) of this section.
p = mean steady-state power over the test interval as described in 
paragraph (e) of this section.

Example:

N = 2
WF1 = 0.85
WF2 = 0.15
mi1 = 2.25842 g/hr
mi2 = 0.063443 g/hr
P1 = 4.5383 kW
P2 = 0.0 kW
[GRAPHIC] [TIFF OMITTED] TR24JA23.136

eNOxcomp = 0.5001 g/kW[middot]hr
* * * * *

0
246. Amend Sec.  1065.655 by revising paragraphs (c) introductory text, 
(e)(1)(i), (e)(4), and (f)(3) to read as follows:

Sec.  1065.655  Chemical balances of fuel, DEF, intake air, and 
exhaust.

* * * * *
    (c) Chemical balance procedure. The calculations for a chemical 
balance involve a system of equations that require iteration. We 
recommend using a computer to solve this system of equations. You must 
guess the initial values of up to three quantities: the amount of water 
in the measured flow, xH2Oexh, fraction of dilution air in 
diluted exhaust, xdil/exh, and the amount of products on a 
C1 basis per dry mole of dry measured flow, 
xCcombdry. You may use time-weighted mean values of intake 
air humidity and dilution air humidity in the chemical balance; as long 
as your intake air and dilution air humidities remain within tolerances 
of 0.0025 mol/mol of their respective mean values over the 
test interval. For each emission concentration, x, and amount of water, 
xH2Oexh, you must determine their completely dry 
concentrations, xdry and xH2Oexhdry. You must 
also use your fuel mixture's atomic hydrogen-to-carbon ratio, [alpha], 
oxygen-to-carbon ratio, [beta], sulfur-to-carbon ratio, [gamma], and 
nitrogen-to-carbon ratio, [delta]; you may optionally account for 
diesel exhaust fluid (or other fluids injected into the exhaust), if 
applicable. You may calculate [alpha], [beta], [gamma], and [delta] 
based on measured fuel composition or based on measured fuel and diesel 
exhaust fluid (or other fluids injected into the exhaust) composition 
together, as

[[Page 4685]]

described in paragraph (e) of this section. You may alternatively use 
any combination of default values and measured values as described in 
paragraph (e) of this section. Use the following steps to complete a 
chemical balance:
* * * * *
    (e) * * *
    (1) * * *
    (i) Determine the carbon and hydrogen mass fractions according to 
ASTM D5291 (incorporated by reference in Sec.  1065.1010). When using 
ASTM D5291 to determine carbon and hydrogen mass fractions of gasoline 
(with or without blended ethanol), use good engineering judgment to 
adapt the method as appropriate. This may include consulting with the 
instrument manufacturer on how to test high-volatility fuels. Allow the 
weight of volatile fuel samples to stabilize for 20 minutes before 
starting the analysis; if the weight still drifts after 20 minutes, 
prepare a new sample). Retest the sample if the carbon, hydrogen, 
oxygen, sulfur, and nitrogen mass fractions do not add up to a total 
mass of 100 0.5%; you may assume oxygen has a zero mass 
contribution for this specification for diesel fuel and neat (E0) 
gasoline. You may also assume that sulfur and nitrogen have a zero mass 
contribution for this specification for all fuels except residual fuel 
blends.
* * * * *
    (4) Calculate [alpha], [beta], [gamma], and [delta] using the 
following equations:
[GRAPHIC] [TIFF OMITTED] TR24JA23.137

Where:

N = total number of fuels and injected fluids over the duty cycle.
j = an indexing variable that represents one fuel or injected fluid, 
starting with j = 1.
mj = the mass flow rate of the fuel or any injected fluid j. For 
applications using a single fuel and no DEF fluid, set this value to 
1. For batch measurements, divide the total mass of fuel over the 
test interval duration to determine a mass rate.
wHj = hydrogen mass fraction of fuel or any injected 
fluid j.
wCj = carbon mass fraction of fuel or any injected fluid 
j.
wOj = oxygen mass fraction of fuel or any injected fluid 
j.
wSj = sulfur mass fraction of fuel or any injected fluid 
j.
wNj = nitrogen mass fraction of fuel or any injected 
fluid j.

Example:

N = 1
j = 1
m1 = 1
wH1 = 0.1239
wC1 = 0.8206
    wO1 = 0.0547
    wS1 = 0.00066
    wN1 = 0.000095
    MC = 12.0107 g/mol
    MH = 1.00794 g/mol
    MO = 15.9994 g/mol
    MS = 32.065 g/mol
    MN = 14.0067
    [GRAPHIC] [TIFF OMITTED] TR24JA23.138
    
[alpha] = 1.799
[beta] = 0.05004
[gamma] = 0.0003012
[delta] = 0.0001003
* * * * *
    (f) * * *
    (3) Fluid mass flow rate calculation. This calculation may be used 
only for steady-state laboratory testing. You may not use this 
calculation if the standard-setting part requires carbon balance error 
verification as described in Sec.  1065.543. See Sec.  
1065.915(d)(5)(iv) for application to field testing. Calculate 
nexh based on mj using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.139

[[Page 4686]]

Where:

nexh = raw exhaust molar flow rate from which you 
measured emissions.
j = an indexing variable that represents one fuel or injected fluid, 
starting with j = 1.
N = total number of fuels and injected fluids over the duty cycle.
mj = the mass flow rate of the fuel or any injected fluid j.
wCj = carbon mass fraction of the fuel and any injected 
fluid j.

Example:

N = 1
j = 1
m1 = 7.559 g/s
wC1 = 0.869 g/g
MC = 12.0107 g/mol
xCcombdry1 = 99.87 mmol/mol = 0.09987 mol/mol
xH20exhdry1 = 107.64 mmol/mol = 0.10764 mol/mol
[GRAPHIC] [TIFF OMITTED] TR24JA23.140

nexh = 6.066 mol/s
* * * * *

0
247. Amend Sec.  1065.660 by revising paragraphs (b)(2)(i) introductory 
text, (c)(1), and (d)(1)(i) introductory text to read as follows:

Sec.  1065.660  THC, NMHC, NMNEHC, CH4, and C2H6 determination.

* * * * *
    (b) * * *
    (2) * * *
    (i) If you need to account for penetration fractions determined as 
a function of molar water concentration, use Eq. 1065.660-4. Otherwise, 
use the following equation for penetration fractions determined using 
an NMC configuration as outlined in Sec.  1065.365(d):
* * * * *
    (c) * * *
    (1) Calculate xNMNEHC based on the test fuel's ethane 
content as follows:
    (i) If the content of your test fuel contains less than 0.010 mol/
mol of ethane, you may omit the calculation of NMNEHC concentration and 
calculate the mass of NMNEHC as described in Sec.  1065.650(c)(6)(i).
    (ii) If the content of your fuel test contains at least 0.010 mol/
mol of ethane, you may omit the calculation of NMNEHC concentration and 
calculate the mass of NMNEHC as described in Sec.  1065.650(c)(6)(ii).
* * * * *
    (d) * * *
    (1) * * *
    (i) If you need to account for penetration fractions determined as 
a function of molar water concentration, use Eq. 1065.660-11. 
Otherwise, use the following equation for penetration fractions 
determined using an NMC configuration as outlined in Sec.  1065.365(d):
* * * * *

0
248. Amend Sec.  1065.667 by revising paragraph (a) to read as follows:

Sec.  1065.667  Dilution air background emission correction.

    (a) To determine the mass of background emissions to subtract from 
a diluted exhaust sample, first determine the total flow of dilution 
air, ndil, over the test interval. This may be a measured 
quantity or a calculated quantity. Multiply the total flow of dilution 
air by the mean mole fraction (i.e., concentration) of a background 
emission. This may be a time-weighted mean or a flow-weighted mean 
(e.g., a proportionally sampled background). Finally, multiply by the 
molar mass, M, of the associated gaseous emission constituent. The 
product of ndil and the mean molar concentration of a 
background emission and its molar mass, M, is the total background 
emission mass, m. In the case of PM, where the mean PM concentration is 
already in units of mass per mole of exhaust, multiply it by the total 
amount of dilution air flow, and the result is the total background 
mass of PM, mPM. Subtract total background mass from total 
mass to correct for background emissions.
* * * * *

0
249. Amend Sec.  1065.670 by revising the introductory text to read as 
follows:

Sec.  1065.670  NOX intake-air humidity and temperature corrections.

    See the standard-setting part to determine if you may correct 
NOX emissions for the effects of intake-air humidity or 
temperature. Use the NOX intake-air humidity and temperature 
corrections specified in the standard-setting part instead of the 
NOX intake-air humidity correction specified in this part 
1065. If the standard-setting part does not prohibit correcting 
NOX emissions for intake-air humidity according to this part 
1065, correct NOX concentrations for intake-air humidity as 
described in this section. See Sec.  1065.650(c)(1) for the proper 
sequence for applying the NOX intake-air humidity and 
temperature corrections. You may use a time-weighted mean intake air 
humidity to calculate this correction if your intake air humidity 
remains within a tolerance of 0.0025 mol/mol of the mean 
value over the test interval. For intake-air humidity correction, use 
one of the following approaches:
* * * * *

0
250. Amend Sec.  1065.672 by revising paragraphs (d)(3) and (4) to read 
as follows:

Sec.  1065.672  Drift correction.

* * * * *
    (d) * * *
    (3) For any pre-test interval concentrations, use the last 
concentration determined before the test interval. For some test 
intervals, the last pre-zero or pre-span might have occurred before one 
or more earlier test intervals.
    (4) For any post-test interval concentrations, use the first 
concentration determined after the test interval. For some test 
intervals, the first post-zero or post-span might occur after one or 
more later test intervals.
* * * * *

0
251. Amend Sec.  1065.675 by revising paragraph (b) to read as follows:

Sec.  1065.675  CLD quench verification calculations.

* * * * *
    (b) Estimate the maximum expected mole fraction of water during 
emission testing, xH2Oexp. Make this estimate where the 
humidified NO span gas was introduced in Sec.  1065.370(e)(6). When 
estimating the maximum expected mole fraction of water, consider the 
maximum expected water content in intake air, fuel combustion products, 
and dilution air (if applicable). If you introduced the humidified NO 
span gas into the sample system upstream of a sample dryer during the 
verification test, you need not estimate the maximum expected mole 
fraction of water and you must set xH2Oexp equal to 
xH2Omeas.
* * * * *

0
252. Amend Sec.  1065.680 by revising the introductory text to read as 
follows:

[[Page 4687]]

Sec.  1065.680  Adjusting emission levels to account for infrequently 
regenerating aftertreatment devices.

    This section describes how to calculate and apply emission 
adjustment factors for engines using aftertreatment technology with 
infrequent regeneration events that may occur during testing. These 
adjustment factors are typically calculated based on measurements 
conducted for the purposes of engine certification, and then used to 
adjust the results of testing related to demonstrating compliance with 
emission standards. For this section, ``regeneration'' means an 
intended event during which emission levels change while the system 
restores aftertreatment performance. For example, exhaust gas 
temperatures may increase temporarily to remove sulfur from an adsorber 
or SCR catalyst or to oxidize accumulated particulate matter in a trap. 
The duration of this event extends until the aftertreatment performance 
and emission levels have returned to normal baseline levels. Also, 
``infrequent'' refers to regeneration events that are expected to occur 
on average less than once over a transient or ramped-modal duty cycle, 
or on average less than once per mode in a discrete-mode test.
* * * * *

0
253. Amend Sec.  1065.695 by revising paragraphs (a) and (c)(12)(ix) to 
read as follows:

Sec.  1065.695  Data requirements.

    (a) To determine the information we require from engine tests, 
refer to the standard-setting part and request from your EPA Program 
Officer the format used to apply for certification or demonstrate 
compliance. We may require different information for different 
purposes, such as for certification applications, approval requests for 
alternate procedures, selective enforcement audits, laboratory audits, 
production-line test reports, and field-test reports.
* * * * *
    (c) * * *
    (12) * * *
    (ix) Warm idle speed value, any enhanced-idle speed value.
* * * * *

0
254. Amend Sec.  1065.715 by revising paragraph (b)(3) to read as 
follows:

Sec.  1065.715  Natural gas.

* * * * *
    (b) * * *
    (3) You may ask for approval to use fuel that does not meet the 
specifications in paragraph (a) of this section, but only if using the 
fuel would not adversely affect your ability to demonstrate compliance 
with the applicable standards in this chapter.
* * * * *

0
255. Amend Sec.  1065.720 by revising paragraphs (a) and (b)(3) to read 
as follows:

Sec.  1065.720  Liquefied petroleum gas.

    (a) Except as specified in paragraph (b) of this section, liquefied 
petroleum gas for testing must meet the specifications in the following 
table:

  Table 1 to Paragraph (a) of Sec.   1065.720--Test Fuel Specifications
                       for Liquefied Petroleum Gas
------------------------------------------------------------------------
                                                           Reference
            Property                     Value           procedure \a\
------------------------------------------------------------------------
Propane, CH.....................  Minimum, 0.85 m\3\/ ASTM D2163.
                                   m\3\.
Vapor pressure at 38[deg]C......  Maximum, 1400 kPa.  ASTM D1267 or
                                                      ASTM D2598 \b\.
Butanes.........................  Maximum, 0.05 m\3\/ ASTM D2163.
                                   m\3\.
Butenes.........................  Maximum, 0.02 m     ASTM D2163.
                                   \3\/m \3\.
Pentenes and heavier............  Maximum, 0.005 m    ASTM D2163.
                                   \3\/m\3\.
Propene.........................  Maximum, 0.1 m \3\/ ASTM D2163.
                                   m\3\.
Residual matter (residue on       Maximum, 0.05 ml    ASTM D2158.
 evaporation of 100 ml oil stain   pass \c\.
 observation).
Corrosion, copper strip.........  Maximum, No. 1....  ASTM D1838.
Sulfur..........................  Maximum, 80 mg/kg.  ASTM D6667.
Moisture content................  pass..............  ASTM D2713.
------------------------------------------------------------------------
\a\ Incorporated by reference; see Sec.   1065.1010. See Sec.
  1065.701(d) for other allowed procedures.
\b\ If these two test methods yield different results, use the results
  from ASTM D1267.
\c\ The test fuel must not yield a persistent oil ring when you add 0.3
  ml of solvent residue mixture to a filter paper in 0.1 ml increments
  and examine it in daylight after two minutes.

    (b) * * *
    (3) You may ask for approval to use fuel that does not meet the 
specifications in paragraph (a) of this section, but only if using the 
fuel would not adversely affect your ability to demonstrate compliance 
with the applicable standards in this chapter.
* * * * *

0
256. Revise Sec.  1065.790 to read as follows:

Sec.  1065.790  Mass standards.

    (a) PM balance calibration weights. Use PM balance calibration 
weights that are certified as NIST-traceable within 0.1% 
uncertainty. Make sure your highest calibration weight has no more than 
ten times the mass of an unused PM-sample medium.
    (b) Dynamometer, fuel mass scale, and DEF mass scale calibration 
weights. Use dynamometer and mass scale calibration weights that are 
certified as NIST-traceable within 0.1% uncertainty.

0
257. Amend Sec.  1065.901 by revising paragraphs (a) and (b)(3) to read 
as follows:

Sec.  1065.901  Applicability.

    (a) Field testing. This subpart specifies procedures for field-
testing engines to determine brake-specific emissions and mass rate 
emissions using portable emission measurement systems (PEMS). These 
procedures are designed primarily for in-field measurements of engines 
that remain installed in vehicles or equipment the field. Field-test 
procedures apply to your engines only as specified in the standard-
setting part.
    (b) * * *
    (3) Do not use PEMS for laboratory measurements if it prevents you 
from demonstrating compliance with the applicable standards in this 
chapter. Some of the PEMS requirements in this part 1065 are less 
stringent than the corresponding laboratory requirements. Depending on 
actual PEMS performance, you might therefore need to account for some 
additional measurement uncertainty when using PEMS for laboratory 
testing. If we ask, you must show us by engineering analysis that any 
additional measurement uncertainty due to your use of PEMS for 
laboratory testing is

[[Page 4688]]

offset by the extent to which your engine's emissions are below the 
applicable standards in this chapter. For example, you might show that 
PEMS versus laboratory uncertainty represents 5% of the standard, but 
your engine's deteriorated emissions are at least 20% below the 
standard for each pollutant.

0
258. Amend Sec.  1065.910 by revising paragraphs (b) and (d)(2) to read 
as follows:

Sec.  1065.910  PEMS auxiliary equipment for field testing.

* * * * *
    (b) Locate the PEMS to minimize the effects of the following 
parameters or place the PEMS in an environmental enclosure that 
minimizes the effect of these parameters on the emission measurement:
    (1) Ambient temperature changes.
    (2) Electromagnetic radiation.
    (3) Mechanical shock and vibration.
* * * * *
    (d) * * *
    (2) You may install your own portable power supply. For example, 
you may use batteries, fuel cells, a portable generator, or any other 
power supply to supplement or replace your use of vehicle power. You 
may connect an external power source directly to the vehicle's, 
vessel's, or equipment's power system; however, you must not supply 
power to the vehicle's power system in excess of 1% of the engine's 
maximum power.

0
259. Amend Sec.  1065.915 by revising paragraph (d)(6) to read as 
follows:

Sec.  1065.915  PEMS instruments.

* * * * *
    (d) * * *
    (6) Permissible deviations. ECM signals may deviate from the 
specifications of this part 1065, but the expected deviation must not 
prevent you from demonstrating that you meet the applicable standards 
in this chapter. For example, your emission results may be sufficiently 
below an applicable standard, such that the deviation would not 
significantly change the result. As another example, a very low engine-
coolant temperature may define a logical statement that determines when 
a test interval may start. In this case, even if the ECM's sensor for 
detecting coolant temperature was not very accurate or repeatable, its 
output would never deviate so far as to significantly affect when a 
test interval may start.

0
260. Amend Sec.  1065.920 by:
0
a. Revising paragraphs (b)(2), (b)(4) introductory text, and 
(b)(4)(iii).
0
b. Removing paragraph (b)(5).
0
c. Redesignating paragraphs (b)(6) and (7) as (b)(5) and (6), 
respectively.
0
d. Revising newly redesignated paragraph (b)(6)(ii).

    The revisions read as follows:

Sec.  1065.920  PEMS calibrations and verifications.

* * * * *
    (b) * * *
    (2) Select or create a duty cycle that has all the following 
characteristics:
    (i) Engine operation that represents normal in-use speeds, loads, 
and degree of transient activity. Consider using data from previous 
field tests to generate a cycle.
    (ii) A duration of (6 to 9) hours.
* * * * *
    (4) Determine the brake-specific emissions and mass rate emissions, 
as applicable, for each test interval for both laboratory and the PEMS 
measurements, as follows:
* * * * *
    (iii) If the standard-setting part specifies the use of a 
measurement allowance for field testing, also apply the measurement 
allowance during calibration using good engineering judgment. If the 
measurement allowance is normally added to the standard, this means you 
must subtract the measurement allowance from measured PEMS emission 
results.
* * * * *
    (6) * * *
    (ii) The entire set of test-interval results passes the 95% 
confidence alternate-procedure statistics for field testing (t-test and 
F-test) specified in Sec.  1065.12.

0
261. Amend Sec.  1065.935 by revising paragraphs (d)(4) and (g) to read 
as follows:

Sec.  1065.935  Emission test sequence for field testing.

* * * * *
    (d) * * *
    (4) Conduct periodic verifications such as zero and span 
verifications on PEMS gas analyzers and use these to correct for drift 
according to paragraph (g) of this section. Do not include data 
recorded during verifications in emission calculations. Conduct the 
verifications as follows:
    (i) For PEMS gas analyzers used to determine NTE emission values, 
perform verifications as recommended by the PEMS manufacturer or as 
indicated by good engineering judgment.
    (ii) For PEMS gas analyzers used to determine bin emission values, 
perform zero verifications at least hourly using purified air. Perform 
span verification at the end of the shift-day or more frequently as 
recommended by the PEMS manufacturer or as indicated by good 
engineering judgment.
* * * * *
    (g) Take the following steps after emission sampling is complete:
    (1) As soon as practical after emission sampling, analyze any 
gaseous batch samples.
    (2) If you used dilution air, either analyze background samples or 
assume that background emissions were zero. Refer to Sec.  1065.140 for 
dilution-air specifications.
    (3) After quantifying all exhaust gases, record mean analyzer 
values after stabilizing a zero gas to each analyzer, then record mean 
analyzer values after stabilizing the span gas to the analyzer. 
Stabilization may include time to purge an analyzer of any sample gas 
and any additional time to account for analyzer response. Use these 
recorded values, including pre-test verifications and any zero 
verifications during testing, to correct for drift as described in 
Sec.  1065.550.
    (4) Verify PEMS gas analyzers used to determine NTE emission values 
as follows:
    (i) Invalidate any data that does not meet the range criteria in 
Sec.  1065.550. Note that it is acceptable that analyzers exceed 100% 
of their ranges when measuring emissions between test intervals, but 
not during test intervals. You do not have to retest an engine if the 
range criteria are not met.
    (ii) Invalidate any data that does not meet the drift criterion in 
Sec.  1065.550. For HC, invalidate any data if the difference between 
the uncorrected and the corrected brake-specific HC emission values are 
not within 10% of the uncorrected results or the applicable 
standard, whichever is greater. For data that does meet the drift 
criterion, correct those test intervals for drift according to Sec.  
1065.672 and use the drift corrected results in emissions calculations.
    (5) Verify PEMS gas analyzers used to determine bin emission values 
as follows:
    (i) Invalidate data from a whole shift-day if more than 1% of 
recorded 1 Hz data exceeds 100% of the selected gas analyzer range. For 
analyzer outputs exceeding 100% of range, calculate emission results 
using the reported value. You must retest an engine if the range 
criteria are not met.
    (ii) Invalidate any data for periods in which the CO and 
CO2 gas analyzers do not meet the drift criterion in Sec.  
1065.550. For HC, invalidate data if the difference between the 
uncorrected and the corrected brake-specific HC emission values are not 
within 10% of the uncorrected results or the applicable

[[Page 4689]]

standard, whichever is greater. For data that do meet the drift 
criterion, correct the data for drift according to Sec.  1065.672 and 
use the drift-corrected results in emissions calculations.
    (iii) For PEMS NOX analyzers used to determine bin 
emission values, invalidate data for the engine over the entire shift-
day if any data do not meet the following drift limits instead of 
meeting the drift criteria specified in Sec.  1065.550:
    (A) The allowable analyzer zero-drift between successive zero 
verifications is 2.5 ppm. The analyzer zero-drift limit 
over the shift-day is 10 ppm.
    (B) The allowable analyzer span-drift limit is 4% of 
the measured span value between successive span verifications.
    (6) Unless you weighed PM in-situ, such as by using an inertial PM 
balance, place any used PM samples into covered or sealed containers 
and return them to the PM-stabilization environment and weigh them as 
described in Sec.  1065.595.

0
262. Amend Sec.  1065.1001 by:
0
a. Removing the definition of ``Designated Compliance Officer''.
0
b. Adding definitions of ``Dual-fuel'', ``EPA Program Officer'', and 
``Flexible-fuel'' in alphabetical order.
0
c. Removing the definition of ``Intermediate test speed''.
0
d. Adding a definition of ``Intermediate speed'' in alphabetical order.
0
e. Revising the definition of ``NIST-traceable''.
0
f. Adding definitions of ``No-load'' and ``Rechargeable Energy Storage 
System (RESS)'' in alphabetical order.
0
g. Revising the definition of ``Steady-state''.

    The additions and revisions read as follows:

Sec.  1065.1001  Definitions.

* * * * *
    Dual-fuel has the meaning given in the standard-setting part.
* * * * *
    EPA Program Officer means the Director, Compliance Division, U.S. 
Environmental Protection Agency, 2000 Traverwood Dr., Ann Arbor, MI 
48105.
* * * * *
    Flexible-fuel has the meaning given in the standard-setting part.
* * * * *
    Intermediate speed has the meaning given in Sec.  1065.610.
* * * * *
    NIST-traceable means relating to a standard value that can be 
related to NIST-stated references through an unbroken chain of 
comparisons, all having stated uncertainties, as specified in NIST 
Technical Note 1297 (incorporated by reference in Sec.  1065.1010). 
Allowable uncertainty limits specified for NIST-traceability refer to 
the propagated uncertainty specified by NIST.
* * * * *
    No-load means a dynamometer setting of zero torque.
* * * * *
    Rechargeable Energy Storage System (RESS) means the components of a 
hybrid engine or vehicle that store recovered energy for later use, 
such as the battery system in a hybrid electric vehicle.
* * * * *
    Steady-state means relating to emission tests in which engine speed 
and load are held at a finite set of nominally constant values. Steady-
state tests are generally either discrete-mode tests or ramped-modal 
tests.
* * * * *

0
263. Amend Sec.  1065.1005 by adding an entry in Table 1 in paragraph 
(a) for ``[kappa]'' in alphanumeric order and revising paragraphs (b) 
and (f)(1), (3), and (4) to read as follows:

Sec.  1065.1005  Symbols, abbreviations, acronyms, and units of 
measure.

* * * * *
    (a) * * *

                               Table 1 of Sec.   1065.1005--Symbols for Quantities
----------------------------------------------------------------------------------------------------------------
                                                                                               Units in terms of
             Symbol                    Quantity              Unit             Unit Symbol        SI base units
----------------------------------------------------------------------------------------------------------------
 
                                                  * * * * * * *
[kappa].........................  opacity
 
                                                  * * * * * * *
----------------------------------------------------------------------------------------------------------------

* * * * *
    (b) Symbols for chemical species. This part uses the following 
symbols for chemical species and exhaust constituents:

  Table 2 of Sec.   1065.1005--Symbols for Chemical Species and Exhaust
                              Constituents
------------------------------------------------------------------------
                 Symbol                              Species
------------------------------------------------------------------------
Ar.....................................  argon.
C......................................  carbon.
CH2O...................................  formaldehyde.
CH2O2..................................  formic acid.
CH3OH..................................  methanol.
CH4....................................  methane.
C2H4O..................................  acetaldehyde.
C2H5OH.................................  ethanol.
C2H6...................................  ethane.
C3H7OH.................................  propanol.
C3H8...................................  propane.
C4H10..................................  butane.
C5H12..................................  pentane.
CO.....................................  carbon monoxide.
CO2....................................  carbon dioxide.

[[Page 4690]]

 
H......................................  atomic hydrogen.
H2.....................................  molecular hydrogen.
H2O....................................  water.
H2SO4..................................  sulfuric acid.
HC.....................................  hydrocarbon.
He.....................................  helium.
\85\Kr.................................  krypton 85.
N2.....................................  molecular nitrogen.
NH3....................................  ammonia.
NMHC...................................  nonmethane hydrocarbon.
NMHCE..................................  nonmethane hydrocarbon
                                          equivalent.
NMNEHC.................................  nonmethane-nonethane
                                          hydrocarbon.
NO.....................................  nitric oxide.
NO2....................................  nitrogen dioxide.
NOX....................................  oxides of nitrogen.
N2O....................................  nitrous oxide.
NMOG...................................  nonmethane organic gases.
NONMHC.................................  non-oxygenated nonmethane
                                          hydrocarbon.
NOTHC..................................  non-oxygenated total
                                          hydrocarbon.
O2.....................................  molecular oxygen.
OHC....................................  oxygenated hydrocarbon.
\210\Po................................  polonium 210.
PM.....................................  particulate matter.
S......................................  sulfur.
SVOC...................................  semi-volatile organic compound.
THC....................................  total hydrocarbon.
THCE...................................  total hydrocarbon equivalent.
ZrO2...................................  zirconium dioxide.
------------------------------------------------------------------------

* * * * *
    (f) * * *
    (1) This part uses the following constants for the composition of 
dry air:

                 Table 6 of Sec.   1065.1005--Constants
------------------------------------------------------------------------
           Symbol                    Quantity               mol/mol
------------------------------------------------------------------------
[gamma]Arair...............  amount of argon in dry              0.00934
                              air.
[gamma]CO2air..............  amount of carbon                   0.000375
                              dioxide in dry air.
[gamma]N2air...............  amount of nitrogen in               0.78084
                              dry air.
[gamma]O2air...............  amount of oxygen in dry            0.209445
                              air.
------------------------------------------------------------------------

* * * * *
    (3) This part uses the following molar gas constant for ideal 
gases:

     Table 8 of Sec.   1065.1005--Molar Gas Constant for Ideal Gases
------------------------------------------------------------------------
                                                    J/(mol[middot]K)
                                               (m\2\[middot]kg[middot]s-
         Symbol                Quantity             \2\[middot]mol-
                                                   \1\[middot]K-\1\)
------------------------------------------------------------------------
R......................  molar gas constant..                8.314472
------------------------------------------------------------------------

    (4) This part uses the following ratios of specific heats for 
dilution air and diluted exhaust:

 Table 9 of Sec.   1065.1005--Ratios of Specific Heats for Dilution Air
                           and Diluted Exhaust
------------------------------------------------------------------------
                                                      [J/(kg[middot]K)]/
           Symbol                    Quantity          [J/(kg[middot]K)]
------------------------------------------------------------------------
[gamma]air.................  ratio of specific heats               1.399
                              for intake air or
                              dilution air.
[gamma]dil.................  ratio of specific heats               1.399
                              for diluted exhaust.
[gamma]exh.................  ratio of specific heats               1.385
                              for raw exhaust.
------------------------------------------------------------------------

* * * * *

0
264. Amend Sec.  1065.1010 by:
0
a. Adding introductory text;

[[Page 4691]]

0
b. Removing paragraph (a); and
0
c. Redesignating paragraphs (b) through (g) as paragraphs (a) through 
(f).

    The addition reads as follows:

Sec.  1065.1010  Incorporation by reference.

    Certain material is incorporated by reference into this part with 
the approval of the Director of the Federal Register under 5 U.S.C. 
552(a) and 1 CFR part 51. To enforce any edition other than that 
specified in this section, EPA must publish a document in the Federal 
Register and the material must be available to the public. All approved 
incorporation by reference (IBR) material is available for inspection 
at EPA and at the National Archives and Records Administration (NARA). 
Contact EPA at: U.S. EPA, Air and Radiation Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004; 
www.epa.gov/dockets; (202) 202-1744. For information on inspecting this 
material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be 
obtained from the following sources:
* * * * *

0
265. Revise the heading for subpart L to read as follows:

Subpart L--Methods for Unregulated and Special Pollutants and 
Additional Procedures

0
266. Amend subpart L by adding a new center header ``VANADIUM 
SUBLIMATION IN SCR CATALYSTS'' after Sec.  1065.1111 and adding 
Sec. Sec.  1065.1113, 1065.1115, 1065.1117, 1065.1119, and 1065.1121 
under the new center header to read as follows:

Vanadium Sublimation In SCR Catalysts

Sec.  1065.1113  General provisions related to vanadium sublimation 
temperatures in SCR catalysts.

    Sections 1065.1113 through 1065.1121 specify procedures for 
determining vanadium emissions from a catalyst based on catalyst 
temperature. Vanadium can be emitted from the surface of SCR catalysts 
at temperatures above 550[deg]C, dependent on the catalyst formulation. 
These procedures are appropriate for measuring the vanadium sublimation 
product from a reactor by sampling onto an equivalent mass of alumina 
and performing analysis by Inductively Coupled Plasma--Optical Emission 
Spectroscopy (ICP-OES). Follow standard analytic chemistry methods for 
any aspects of the analysis that are not specified.
    (a) The procedure is adapted from ``Behavior of Titania-supported 
Vanadia and Tungsta SCR Catalysts at High Temperatures in Reactant 
Streams: Tungsten and Vanadium Oxide and Hydroxide Vapor Pressure 
Reduction by Surficial Stabilization'' (Chapman, D.M., Applied 
Catalysis A: General, 2011, 392, 143-150) with modifications to the 
acid digestion method from ``Measuring the trace elemental composition 
of size-resolved airborne particles'' (Herner, J.D. et al, 
Environmental Science and Technology, 2006, 40, 1925-1933).
    (b) Laboratory cleanliness is especially important throughout 
vanadium testing. Thoroughly clean all sampling system components and 
glassware before testing to avoid sample contamination.

Sec.  1065.1115  Reactor design and setup.

    Vanadium measurements rely on a reactor that adsorbs sublimation 
vapors of vanadium onto an alumina capture bed with high surface area.
    (a) Configure the reactor with the alumina capture bed downstream 
of the catalyst in the reactor's hot zone to adsorb vanadium vapors at 
high temperature. You may use quartz beads upstream of the catalyst to 
help stabilize reactor gas temperatures. Select an alumina material and 
design the reactor to minimize sintering of the alumina. For a 1-inch 
diameter reactor, use 4 to 5 g of \1/8\ inch extrudates or -14/+24 mesh 
(approximately 0.7 to 1.4 mm) gamma alumina (such as Alfa Aesar, 
aluminum oxide, gamma, catalyst support, high surface area, bimodal). 
Position the alumina downstream from either an equivalent amount of -
14/+24 mesh catalyst sample or an approximately 1-inch diameter by 1 to 
3-inch long catalyst-coated monolith sample cored from the production-
intent vanadium catalyst substrate. Separate the alumina from the 
catalyst with a 0.2 to 0.4 g plug of quartz wool. Place a short 4 g 
plug of quartz wool downstream of the alumina to maintain the position 
of that bed. Use good engineering judgment to adjust as appropriate for 
reactors of different sizes.
    (b) Include the quartz wool with the capture bed to measure 
vanadium content. We recommend analyzing the downstream quartz wool 
separately from the alumina to see if the alumina fails to capture some 
residual vanadium.
    (c) Configure the reactor such that both the sample and capture 
beds are in the reactor's hot zone. Design the reactor to maintain 
similar temperatures in the capture bed and catalyst. Monitor the 
catalyst and alumina temperatures with Type K thermocouples inserted 
into a thermocouple well that is in contact with the catalyst sample 
bed.
    (d) If there is a risk that the quartz wool and capture bed are not 
able to collect all the vanadium, configure the reactor with an 
additional capture bed and quartz wool plug just outside the hot zone 
and analyze the additional capture bed and quartz wool separately.
    (e) An example of a catalyst-coated monolith and capture bed 
arrangement in the reactor tube are shown in the following figure:

Figure 1 to paragraph (e) of Sec.  1065.1115-- Example of Reactor Setup

[[Page 4692]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.141

    (f) You may need to account for vanadium-loaded particles 
contaminating catalyst-coated monoliths as a result of physical 
abrasion. To do this, determine how much titanium is in the capture bed 
and compare to an alumina blank. Using these values and available 
information about the ratio of vanadium to titanium in the catalyst, 
subtract the mass of vanadium catalyst material associated with the 
catalyst particles from the total measured vanadium on the capture bed 
to determine the vanadium recovered due to sublimation.

Sec.  1065.1117  Reactor aging cycle for determination of vanadium 
sublimation temperature.

    This section describes the conditions and process required to 
operate the reactor described in Sec.  1065.1115 for collection of the 
vanadium sublimation samples for determination of vanadium sublimation 
temperature. The reactor aging cycle constitutes the process of testing 
the catalyst sample over all the test conditions described in paragraph 
(b) of this section.
    (a) Set up the reactor to flow gases with a space velocity of at 
least 35,000/hr with a pressure drop across the catalyst and capture 
beds less than 35 kPa. Use test gases meeting the following 
specifications, noting that not all gases will be used at the same 
time:
    (1) 5 vol% O2, balance N2.
    (2) NO, balance N2. Use an NO concentration of (200 to 
500) ppm.
    (3) NH3, balance N2. Use an NH3 
concentration of (200 to 500) ppm.
    (b) Perform testing as follows:
    (1) Add a new catalyst sample and capture bed into the reactor as 
described in Sec.  1065.1113. Heat the reactor to 550[deg]C while 
flowing the oxygen blend specified in paragraph (a)(1) of this section 
as a pretest gas mixture. Ensure that no H2O is added to the 
pretest gas mixture to reduce the risk of sintering and vanadium 
sublimation.
    (2) Start testing at a temperature that is lower than the point at 
which vanadium starts to sublime. Start testing when the reactor 
reaches 550[deg]C unless testing supports a lower starting temperature. 
Once the reactor reaches the starting temperature and the catalyst has 
been equilibrated to the reactor temperature, flow NO and 
NH3 test gases for 18 hours with a nominal H2O 
content of 5 volume percent. If an initial starting temperature of 
550[deg]C results in vanadium sublimation, you may retest using a new 
catalyst sample and a lower initial starting temperature.
    (3) After 18 hours of exposure, flow the pretest oxygen blend as 
specified in paragraph (b)(1) of this section and allow the reactor to 
cool down to room temperature.
    (4) Analyze the sample as described in Sec.  1065.1121.
    (5) Repeat the testing in paragraphs (b)(1) through (4) of this 
section by raising the reactor temperature in increments of 50[deg]C up 
to the temperature at which vanadium sublimation begins.
    (6) Once sublimation has been detected, repeat the testing in 
paragraphs (b)(1) through (4) of this section by decreasing the reactor 
temperature in increments of 25 [deg]C until the vanadium concentration 
falls below the sublimation threshold.
    (7) Repeat the testing in paragraphs (b)(1) through (6) of this 
section with a nominal H2O concentration of 10 volume 
percent or the maximum water concentration expected at the standard.
    (8) You may optionally test in a manner other than testing a single 
catalyst formulation in series across all test temperatures. For 
example, you may test additional samples at the same reactor 
temperature before moving on to the next temperature.
    (c) The effective sublimation temperature for the tested catalyst 
is the lowest reactor temperature determined in paragraph (b) of this 
section below which vanadium emissions are less than the method 
detection limit.

Sec.  1065.1119  Blank testing.

    This section describes the process for analyzing blanks. Use blanks 
to determine the background effects and the potential for contamination 
from the sampling process.
    (a) Take blanks from the same batch of alumina used for the capture 
bed.
    (b) Media blanks are used to determine if there is any 
contamination in the sample media. Analyze at least one media blank for 
each reactor aging cycle or round of testing performed under Sec.  
1065.1117. If your sample media is taken from the same lot, you may 
analyze media blanks less frequently consistent with good engineering 
judgment.
    (c) Field blanks are used to determine if there is any 
contamination from environmental exposure of the sample media. Analyze 
at least one field blank for each reactor aging cycle or round of 
testing performed under Sec.  1065.1117. Field blanks must be contained 
in a sealed environment and accompany the reactor sampling system 
throughout the course of a test, including reactor disassembly, sample 
packaging, and

[[Page 4693]]

storage. Use good engineering judgment to determine how frequently to 
generate field blanks. Keep the field blank sample close to the reactor 
during testing.
    (d) Reactor blanks are used to determine if there is any 
contamination from the sampling system. Analyze at least one reactor 
blank for each reactor aging cycle or round of testing performed under 
Sec.  1065.1117.
    (1) Test reactor blanks with the reactor on and operated 
identically to that of a catalyst test in Sec.  1065.1117 with the 
exception that when loading the reactor, only the alumina capture bed 
will be loaded (no catalyst sample is loaded for the reactor blank). We 
recommend acquiring reactor blanks with the reactor operating at 
average test temperature you used when acquiring your test samples 
under Sec.  1065.1117.
    (2) You must run at least three reactor blanks if the result from 
the initial blank analysis is above the detection limit of the method, 
with additional blank runs based on the uncertainty of the reactor 
blank measurements, consistent with good engineering judgment.

Sec.  1065.1121  Vanadium sample dissolution and analysis in alumina 
capture beds.

    This section describes the process for dissolution of vanadium from 
the vanadium sublimation samples collect in Sec.  1065.1117 and any 
blanks collected in Sec.  1065.1119 as well as the analysis of the 
digestates to determine the mass of vanadium emitted and the associated 
sublimation temperature threshold based on the results of all the 
samples taken during the reactor aging cycle.
    (a) Digest the samples using the following procedure, or an 
equivalent procedure:
    (1) Place the recovered alumina, a portion of the ground quartz 
tube from the reactor, and the quartz wool in a Teflon pressure vessel 
with a mixture made from 1.5 mL of 16 N HNO3, 0.5 mL of 28 N 
HF, and 0.2 mL of 12 N HCl. Note that the amount of ground quartz tube 
from the reactor included in the digestion can influence the vanadium 
concentration of both the volatilized vanadium from the sample and the 
method detection limit. You must be consistent with the amount ground 
quartz tube included in the sample analysis for your testing. You must 
limit the amount of quartz tube to include only portions of the tube 
that would be likely to encounter volatilized vanadium.
    (2) Program a microwave oven to heat the sample to 180 [deg]C over 
9 minutes, followed by a 10-minute hold at that temperature, and 1 hour 
of ventilation/cooling.
    (3) After cooling, dilute the digests to 30 mL with high purity 
18M[Omega] water prior to ICP-MS (or ICP-OES) analysis. Note that this 
digestion technique requires adequate safety measures when working with 
HF at high temperature and pressure. To avoid ``carry-over'' 
contamination, rigorously clean the vessels between samples as 
described in ``Microwave digestion procedures for environmental 
matrixes'' (Lough, G.C. et al, Analyst. 1998, 123 (7), 103R-133R).
    (b) Analyze the digestates for vanadium as follows:
    (1) Perform the analysis using ICP-OES (or ICP-MS) using standard 
plasma conditions (1350 W forward power) and a desolvating 
microconcentric nebulizer, which will significantly reduce oxide- and 
chloride-based interferences.
    (2) We recommend that you digest and analyze a minimum of three 
solid vanadium NIST Standard Reference Materials in duplicate with 
every batch of 25 vanadium alumina capture bed samples that you analyze 
in this section, as described in ``Emissions of metals associated with 
motor vehicle roadways'' (Herner, J.D. et al, Environmental Science and 
Technology. 2005, 39, 826-836). This will serve as a quality assurance 
check to help gauge the relative uncertainties in each measurement, 
specifically if the measurement errors are normally distributed and 
independent.
    (3) Use the 3-sigma approach to determine the analytical method 
detection limits for vanadium and the 10-sigma approach if you 
determine the reporting limit. This process involves analyzing at least 
seven replicates of a reactor blank using the analytical method 
described in paragraphs (a) and (b)(1) of this section, converting the 
responses into concentration units, and calculating the standard 
deviation. Determine the detection limit by multiplying the standard 
deviation by 3 and adding it to the average. Determine the reporting 
limit by multiplying the standard deviation by 10 and adding it to the 
average. Determine the following analytical method detection limits:
    (i) Determine the ICP-MS (or ICP-OES) instrumental detection limit 
(ng/L) by measuring at least seven blank samples made up of the 
reagents from paragraph (a) of this section.
    (ii) Determine the method detection limit ([micro]g/m\3\ of flow) 
by measuring at least seven reactor blank samples taken as described in 
Sec.  1065.1119(d).
    (iii) We recommend that your method detection limit determined 
under paragraph (b)(3)(ii) of this section is at or below 15 [micro]g/
m\3\. You must report your detection limits determined in this 
paragraph (b)(3) and reporting limits (if determined) with your test 
results.
    (4) If you account for vanadium-loaded particles contaminating 
catalyst-coated monoliths as a result of physical abrasion as allowed 
in Sec.  1065.1115(f), use the 3-sigma approach to determine the 
analytical method detection limits for titanium and the 10-sigma 
approach if you determine the reporting limit. This process involves 
analyzing at least seven replicates of a blank using the analytical 
method described in paragraphs (a) and (b)(1) of this section, 
converting the responses into concentration units, and calculating the 
standard deviation. Determine the detection limit by multiplying the 
standard deviation by 3 and subtracting it from the average. Determine 
the reporting limit by multiplying the standard deviation by 10 and 
subtracting it from the average.
    (i) Determine the ICP-MS (or ICP-OES) instrumental detection limit 
(ng/L) by measuring at least seven blank samples made up of the 
reagents from paragraph (a) of this section.
    (ii) Determine the method detection limit ([micro]g/m\3\ of flow) 
by measuring at least seven reactor blank samples taken as described in 
Sec.  1065.1119(d).

0
267. Amend subpart L by adding a new center header ``SMOKE OPACITY'' 
after the newly added Sec.  1065.1121 and adding Sec. Sec.  1065.1123, 
1065.1125, and 1065.1127 under the new center header to read as 
follows:

Smoke Opacity

Sec.  1065.1123  General provisions for determining exhaust opacity.

    The provisions of Sec.  1065.1125 describe system specifications 
for measuring percent opacity of exhaust for all types of engines. The 
provisions of Sec.  1065.1127 describe how to use such a system to 
determine percent opacity of engine exhaust for applications other than 
locomotives. See 40 CFR 1033.525 for measurement procedures for 
locomotives.

Sec.  1065.1125  Exhaust opacity measurement system.

    Smokemeters measure exhaust opacity using full-flow open-path light 
extinction with a built-in light beam across the exhaust stack or 
plume. Prepare and install a smokemeter system as follows:
    (a) Except as specified in paragraph (d) of this section, use a 
smokemeter capable of providing continuous measurement that meets the 
following specifications:
    (1) Use an incandescent lamp with a color temperature between (2800 
and 3250) K or a different light source with

[[Page 4694]]

a spectral peak between (550 and 570) nm.
    (2) Collimate the light beam to a nominal diameter of 3 centimeters 
and maximum divergence angle of 6 degrees.
    (3) Include a photocell or photodiode as a detector. The detector 
must have a maximum spectral response between (550 and 570) nm, with 
less than 4 percent of that maximum response below 430 nm and above 680 
nm. These specifications correspond to visual perception with the human 
eye.
    (4) Use a collimating tube with an aperture that matches the 
diameter of the light beam. Restrict the detector to viewing within a 
16 degree included angle.
    (5) Optionally use an air curtain across the light source and 
detector window to minimize deposition of smoke particles, as long as 
it does not measurably affect the opacity of the sample.
    (6) The diagram in the following figure illustrates the smokemeter 
configuration:

Figure 1 to paragraph (a)(6) of Sec.  1065.1125--Smokemeter Diagram
[GRAPHIC] [TIFF OMITTED] TR24JA23.142

    (b) Smokemeters for locomotive applications must have a full-scale 
response time of 0.5 seconds or less. Smokemeters for locomotive 
applications may attenuate signal responses with frequencies higher 
than 10 Hz with a separate low-pass electronic filter that has the 
following performance characteristics:
    (1) Three decibel point: 10 Hz.
    (2) Insertion loss: (0.0 0.5) dB.
    (3) Selectivity: 12 dB down at 40 Hz minimum.
    (4) Attenuation: 27 dB down at 40 Hz minimum.
    (c) Configure exhaust systems as follows for measuring exhaust 
opacity:
    (1) For locomotive applications:
    (i) Optionally add a stack extension to the locomotive muffler.
    (ii) For in-line measurements, the smokemeter is integral to the 
stack extension.
    (iii) For end-of-line measurements, mount the smokemeter directly 
at the end of the stack extension or muffler.
    (iv) For all testing, minimize distance from the optical centerline 
to the muffler outlet; in no case may it be more than 300 cm. The 
maximum allowable distance of unducted space upstream of the optical 
centerline is 50 cm, whether the unducted portion is upstream or 
downstream of the stack extensions.
    (2) Meet the following specifications for all other applications:
    (i) For in-line measurements, install the smokemeter in an exhaust 
pipe segment downstream of all engine components. This will typically 
be part of a laboratory configuration to route the exhaust to an 
analyzer. The exhaust pipe diameter must be constant within 3 exhaust 
pipe diameters before and after the smokemeter's optical centerline. 
The exhaust pipe diameter may not change by more than a 12-degree half-
angle within 6 exhaust pipe diameters upstream of the smokemeter's 
optical centerline.
    (ii) For end-of-line measurements with systems that vent exhaust to 
the ambient, add a stack extension and position the smokemeter such 
that its optical centerline is (2.5 0.625) cm upstream of 
the stack extension's exit. Configure the exhaust stack and extension 
such that at least the last 60 cm is a straight pipe with a circular 
cross section with an approximate inside diameter as specified in the 
following table:

Table 1 to Paragraph (c)(2)(ii) of Sec.   1065.1125--Approximate Exhaust
                   Pipe Diameter Based on Engine Power
------------------------------------------------------------------------
                                                            Approximate
                   Maximum rated power                     exhaust pipe
                                                          diameter  (mm)
------------------------------------------------------------------------
kW<40...................................................              38
40<=kW<75...............................................              50
75<=kW<150..............................................              76
150<=kW<225.............................................             102
225<=kW<375.............................................             127
kW= 375......................................             152
------------------------------------------------------------------------

    (iii) For both in-line and end-of-line measurements, install the 
smokemeter so its optical centerline is (3 to 10) meters further 
downstream than the point in the exhaust stream that is farthest 
downstream considering all the following components: exhaust manifolds, 
turbocharger outlets, exhaust aftertreatment devices, and junction 
points for combining exhaust flow from multiple exhaust manifolds.
    (3) Orient the light beam perpendicular to the direction of exhaust 
flow. Install the smokemeter so it does not influence exhaust flow 
distribution or the shape of the exhaust plume. Set up the smokemeter's 
optical path length as follows:
    (i) For locomotive applications, the optical path length must be at 
least as wide as the exhaust plume.
    (ii) For all other applications, the optical path length must be 
the same as the diameter of the exhaust flow. For noncircular exhaust 
configurations, set up the smokemeter such that the light beam's path 
length is across the longest

[[Page 4695]]

axis with an optical path length equal to the hydraulic diameter of the 
exhaust flow.
    (4) The smokemeter must not interfere with the engine's ability to 
meet the exhaust backpressure requirements in Sec.  1065.130(h).
    (5) For engines with multiple exhaust outlets, measure opacity 
using one of the following methods:
    (i) Join the exhaust outlets together to form a single flow path 
and install the smokemeter (3 to 10) m downstream of the point where 
the exhaust streams converge or the last exhaust aftertreatment device, 
whichever is farthest downstream.
    (ii) Install a smokemeter in each of the exhaust flow paths. Report 
all measured values. All measured values must comply with standards.
    (6) The smokemeter may use purge air or a different method to 
prevent carbon or other exhaust deposits on the light source and 
detector. Such a method used with end-of-line measurements may not 
cause the smoke plume to change by more than 0.5 cm at the smokemeter. 
If such a method affects the smokemeter's optical path length, follow 
the smokemeter manufacturer's instructions to properly account for that 
effect.
    (d) You may use smokemeters meeting alternative specifications as 
follows:
    (1) You may use smokemeters that use other electronic or optical 
techniques if they employ substantially identical measurement 
principles and produce substantially equivalent results.
    (2) You may ask us to approve the use of a smokemeter that relies 
on partial flow sampling. Follow the instrument manufacturer's 
installation, calibration, operation, and maintenance procedures if we 
approve your request. These procedures must include correcting for any 
change in the path length of the exhaust plume relative to the diameter 
of the engine's exhaust outlet.

Sec.  1065.1127  Test procedure for determining percent opacity.

    The test procedure described in this section applies for everything 
other than locomotives. The test consists of a sequence of engine 
operating points on an engine dynamometer to measure exhaust opacity 
during specific engine operating modes to represent in-use operation. 
Measure opacity using the following procedure:
    (a) Use the equipment and procedures specified in this part 1065.
    (b) Calibrate the smokemeter as follows:
    (1) Calibrate using neutral density filters with approximately 10, 
20, and 40 percent opacity. Confirm that the opacity values for each of 
these reference filters are NIST-traceable within 185 days of testing, 
or within 370 days of testing if you consistently protect the reference 
filters from light exposure between tests.
    (2) Before each test and optionally during engine idle modes, 
remove the smokemeter from the exhaust stream, if applicable, and 
calibrate as follows:
    (i) Zero. Adjust the smokemeter to give a zero response when there 
is no detectable smoke.
    (ii) Linearity. Insert each of the qualified reference filters in 
the light path perpendicular to the axis of the light beam and adjust 
the smokemeter to give a result within 1 percentage point of the named 
value for each reference filter.
    (c) Prepare the engine, dynamometer, and smokemeter for testing as 
follows:
    (1) Set up the engine to run in a configuration that represents in-
use operation.
    (2) Determine the smokemeter's optical path length to the nearest 
mm.
    (3) If the smokemeter uses purge air or another method to prevent 
deposits on the light source and detector, adjust the system according 
to the system manufacturer's instructions and activate the system 
before starting the engine.
    (4) Program the dynamometer to operate in torque-control mode 
throughout testing. Determine the dynamometer load needed to meet the 
cycle requirements in paragraphs (d)(4)(ii) and (iv) of this section.
    (5) You may program the dynamometer to apply motoring assist with 
negative flywheel torque, but only during the first 0.5 seconds of the 
acceleration events in paragraphs (d)(4)(i) and (ii) of this section. 
Negative flywheel torque may not exceed 13.6 N[middot]m.
    (d) Operate the engine and dynamometer over repeated test runs of 
the duty cycle illustrated in Figure 1 of this appendix. As noted in 
the figure, the test run includes an acceleration mode from points A 
through F in the figure, followed by a lugging mode from points I to J. 
Detailed specifications for testing apply as follows:
    (1) Continuously record opacity, engine speed, engine torque, and 
operator demand over the course of the entire test at 10 Hz; however, 
you may interrupt measurements to recalibrate during each idle mode.
    (2) Precondition the engine by operating it for 10 minutes at 
maximum mapped power.
    (3) Operate the engine for (5.0 to 5.5) minutes at warm idle speed, 
[fnof]nidle, with load set to Curb Idle Transmission Torque.
    (4) Operate the engine and dynamometer as follows during the 
acceleration mode:
    (i) First acceleration event--AB. Partially increase and hold 
operator demand to stabilize engine speed briefly at (200 50) r/min above [fnof]nidle. The start of this 
acceleration is the start of the test (t = 0 s).
    (ii) Second acceleration event--CD. As soon as measured engine 
speed is within the range specified in paragraph (d)(4)(i) of this 
section, but not more than 3 seconds after the start of the test, 
rapidly set and hold operator demand at maximum. Operate the 
dynamometer using a preselected load to accelerate engine speed to 85 
percent of maximum test speed, [fnof]ntest, in (5 1.5) seconds. The engine speed throughout the acceleration must 
be within 100 r/min of a target represented by a linear 
transition between the low and high engine speed targets.
    (iii) Transition--DEF. As soon as measured engine speed reaches 85 
percent of [fnof]ntest, rapidly set and hold operator demand 
at minimum and simultaneously apply a load to decelerate to 
intermediate speed in (0.5 to 3.5) seconds. Use the same load 
identified for the acceleration event in paragraph (d)(4)(iv) of this 
section.
    (iv) Third acceleration event--FGH. Rapidly set and hold operator 
demand at maximum when the engine is within 50 r/min of 
intermediate speed. Operate the dynamometer using a preselected load to 
accelerate engine speed to at least 95 percent of 
[fnof]ntest in (10 2) seconds.
    (5) Operate the engine and dynamometer as follows during the 
lugging mode:
    (i) Transition--HI. When the engine reaches 95 percent of 
[fnof]ntest, keep operator demand at maximum and immediately 
set dynamometer load to control the engine at maximum mapped power. 
Continue the transition segment for (50 to 60) seconds. For at least 
the last 10 seconds of the transition segment, hold engine speed within 
50 r/min of [fnof]ntest and power at or above 95 
percent of maximum mapped power. Conclude the transition by increasing 
dynamometer load to reduce engine speed as specified in paragraph 
(d)(4)(iii) of this section, keeping operator demand at maximum.
    (ii) Lugging--IJ. Apply dynamometer loading as needed to decrease 
engine speed from 50 r/min below fntest to intermediate 
speed in (35 5) seconds. The engine speed must remain 
within 100 r/min of a target represented by a

[[Page 4696]]

linear transition between the low and high engine speed targets.
    (6) Return the dynamometer and engine controls to the idle position 
described in paragraph (d)(3) of this section within 60 seconds of 
completing the lugging mode.
    (7) Repeat the procedures in paragraphs (d)(3) through (6) of this 
section as needed to complete three valid test runs. If you fail to 
meet the specifications during a test run, continue to follow the 
specified duty cycle before starting the next test run.
    (8) Shut down the engine or remove the smokemeter from the exhaust 
stream to verify zero and linearity. Void the test if the smokemeter 
reports more than 2 percent opacity for the zero verification, or if 
the smokemeter's error for any of the linearity checks specified in 
paragraph (b)(2) of this section is more than 2 percent.
    (e) Analyze and validate the test data as follows:
    (1) Divide each test run into test segments. Each successive test 
segment starts when the preceding segment ends. Identify the test 
segments based on the following criteria:
    (i) The idle mode specified in paragraph (d)(3) of this section for 
the first test run starts immediately after engine preconditioning is 
complete. The idle mode for later test runs must start within 60 
seconds after the end of the previous test run as specified in 
paragraph (d)(6) of this section. The idle mode ends when operator 
demand increases for the first acceleration event (Points A and B).
    (ii) The first acceleration event in paragraph (d)(4)(i) of this 
section ends when operator demand is set to maximum for the second 
acceleration event (Point C).
    (iii) The second acceleration event in paragraph (d)(4)(ii) of this 
section ends when the engine reaches 85 percent of maximum test speed, 
[fnof]ntest, (Point D) and operator demand is set to minimum 
(Point E).
    (iv) The transition period in paragraph (d)(4)(iii) of this section 
ends when operator demand is set to maximum (Point F).
    (v) The third acceleration event in paragraph (d)(4)(iv) of this 
section ends when engine speed reaches 95 percent of 
[fnof]ntest (Point H).
    (vi) The transition period in paragraph (d)(5)(i) of this section 
ends when engine speed first decreases to a point more than 50 r/min 
below [fnof]ntest (Point I).
    (vii) The lugging mode in paragraph (d)(5)(ii) of this section ends 
when the engine reaches intermediate speed (Point J).
    (2) Convert measured instantaneous values to standard opacity 
values, [kappa]std, based on the appropriate optical path 
length specified in Table 1 of Sec.  1065.1125 using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.143

Where:

[kappa]std = standard instantaneous percent opacity.
[kappa]meas = measured instantaneous percent opacity.
lstd = standard optical path length corresponding with 
engine power, in millimeters.
lmeas = the smokemeter's optical path length, in 
millimeters.

Example for an engine < 40 kW:

[kappa]meas = 14.1%
lstd = 38 mm
lmeas = 41 mm
[GRAPHIC] [TIFF OMITTED] TR24JA23.144

    (3) Select opacity results from corrected measurements collected 
across test segments as follows:
    (i) Divide measurements from acceleration and lugging modes into 
half-second intervals. Determine average opacity values during each 
half-second interval.
    (ii) Identify the 15 highest half-second values during the 
acceleration mode of each test run.
    (iii) Identify the five highest half-second values during the 
lugging mode of each test run.
    (iv) Identify the three overall highest values from paragraphs 
(e)(3)(ii) and (iii) of this section for each test run.
    (f) Determine percent opacity as follows:
    (1) Acceleration. Determine the percent opacity for the 
acceleration mode by calculating the average of the 45 readings from 
paragraph (e)(3)(ii) of this section.
    (2) Lugging. Determine the percent opacity for the lugging mode by 
calculating the average of the 15 readings from paragraph (e)(3)(iii) 
of this section.
    (3) Peak. Determine the percent opacity for the peaks in either 
acceleration or lugging mode by calculating the average of the 9 
readings from paragraph (e)(3)(iv) of this section.
    (g) Submit the following information in addition to what is 
required by Sec.  1065.695:
    (1) Exhaust pipe diameter(s).
    (2) Measured maximum exhaust system backpressure over the entire 
test.
    (3) Most recent date for establishing that each of the reference 
filters from paragraph (b) of this section are NIST-traceable.
    (4) Measured smokemeter zero and linearity values after testing.
    (5) 10 Hz data from all valid test runs.
    (h) The following figure illustrates the dynamometer controls and 
engine speeds for exhaust opacity testing:

Figure 1 to paragraph (h) of Sec.  1065.1127--Schemati of Smoke Opacity 
Duty Cycle

[[Page 4697]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.145

0
268. Amend subpart L by adding a new center header ``ACCELERATED 
AFTERTREATMENT AGING'' after the newly added Sec.  1065.1127 and adding 
Sec. Sec.  1065.1131 through 1065.1145 under

[[Page 4698]]

the new center header to read as follows:

Accelerated Aftertreatment Aging

Sec.  1065.1131  General provisions related to accelerated aging of 
compression-ignition aftertreatment for deterioration factor 
determination.

    Sections 1065.1131 through 1065.1145 specify procedures for aging 
compression-ignition engine aftertreatment systems in an accelerated 
fashion to produce an aged aftertreatment system for durability 
demonstration. Determine the target number of hours that represents 
useful life for an engine family as described in the standard setting 
part. The method described is a procedure for translating field data 
that represents a given application into an accelerated aging cycle for 
that specific application, as well as methods for carrying out aging 
using that cycle. The procedure is intended to be representative of 
field aging, includes exposure to elements of both thermal and chemical 
aging, and is designed to achieve an acceleration of aging that is ten 
times a dynamometer or field test (1,000 hours of accelerated aging is 
equivalent to 10,000 hours of standard aging).
    (a) Development of an application-specific accelerated aging cycle 
generally consists of the following steps:
    (1) Gathering and analysis of input field data.
    (2) Determination of key components for aging.
    (3) Determination of a thermal deactivation coefficient for each 
key component.
    (4) Determination of potential aging modes using clustering 
analysis.
    (5) Down-selection of final aging modes.
    (6) Incorporation of regeneration modes (if necessary).
    (7) Cycle generation.
    (8) Calculation of thermal deactivation.
    (9) Cycle scaling to reach thermal deactivation.
    (10) Determination of oil exposure rates.
    (11) Determination of sulfur exposure rates.
    (b) There are two methods for using field data to develop aging 
cycles, as described in Sec.  1065.1139(b)(1) and (2). Method selection 
depends on the type of field data available. Method 1 directly uses 
field data to generate aging modes, while Method 2 uses field data to 
weight appropriate regulatory duty cycles that are used for emissions 
certification.
    (c) Carry out accelerated aging on either a modified engine 
platform or a reactor-based burner platform. The requirements for these 
platforms are described in Sec.  1065.1141 for engine bench aging and 
Sec.  1065.1143 for burner-based bench aging.

Sec.  1065.1133  Application selection, data gathering, and analysis.

    This section describes the gathering and analysis of the field 
generated data that is required for generation of the data cycle. 
Gather data for the determination of aftertreatment exposure to 
thermal, lubricating oil, and sulfur related aging factors. You are not 
required to submit this data as part of your application, but you must 
make this data available if we request it.
    (a) Field data target selection. Use good engineering judgment to 
select one or more target applications for gathering of input field 
data for the accelerated aging cycle generation that represent a 
greater than average exposure to potential field aging factors. It 
should be noted that the same application may not necessarily represent 
the worst case for all aging factors. If sufficient data is not 
available to make this determination with multiple applications, you 
may select the application that is expected to have the highest sales 
volume for a given engine family.
    (1) Thermal exposure. We recommend that you select applications for 
a given engine family that represent the 90th percentile of exposure to 
thermal aging. For example, if a given engine family incorporates a 
periodic infrequent regeneration event that involves exposure to higher 
temperatures than are observed during normal (non-regeneration) 
operation, we recommend that you select an application wherein the 
total duration of the cumulative regeneration events is at the 90th 
percentile of expected applications for that family. For an engine that 
does not incorporate a distinct regeneration event, we recommend 
selecting an application that represents the 90th percentile in terms 
of the overall average temperature.
    (2) Oil exposure. Use a combination of field and laboratory 
measurements to determine an average rate of oil consumption in grams 
per hour that reaches the exhaust. You may use the average total oil 
consumption rate of the engine if you are unable to determine what 
portion of the oil consumed reaches the exhaust aftertreatment.
    (3) Sulfur exposure. The total sulfur exposure is the sum of fuel- 
and oil-related sulfur. Oil-related sulfur will be accounted for in the 
acceleration of oil exposure directly. We recommend that you determine 
fuel-related sulfur exposure by selecting an application that 
represents the 90th percentile of fuel consumption. Use good 
engineering judgment to determine that average rate of fuel consumption 
for the target application. You may use a combination of field and 
laboratory measurements to make this determination. Calculate the 
average rate of fuel-related sulfur exposure in grams per hour from the 
average rate of fuel consumption assuming a fuel sulfur level of 10 ppm 
by weight.
    (b) Application data gathering. Use good engineering judgment to 
gather data from one or more field vehicles to support the accelerated 
aging cycle generation. We recommend that you gather data at a 
recording frequency of 1 Hz. The type of data that you gather will 
depend on the method you plan to use for cycle generation. Record both 
the data and the number of engine operating hours which that data 
represents regardless of method, as this information will be used to 
scale the cycle calculations. Use good engineering judgment to ensure 
that the amount of data recorded provides an accurate representation of 
field operation for the target application. If your application 
includes a periodic regeneration event, you must record multiple events 
to ensure that you have accurately captured the variation of those 
events. We recommend that you record at least 300 hours of field 
operation, and at least 3 different regeneration events if applicable.
    (1) When using Method 1, direct field data use, as described in 
Sec.  1065.1139(b)(1), record data for exhaust flow rate and at least 
one representative inlet temperature for each major aftertreatment 
system catalyst component, such as a diesel oxidation catalyst (DOC), 
diesel particulate filter (DPF), or selective catalytic reduction (SCR) 
catalyst. If a given catalyst component has multiple substrates 
installed directly in sequence, it is sufficient to record only the 
inlet temperature for the first catalyst substrate in the sequence. It 
is not necessary to record separate temperatures for substrates that 
are ``zone-coated'' with multiple catalyst functions. Record a 
representative outlet temperature for any major catalyst component that 
is used to elevate the temperature of downstream components. This could 
be the inlet of the next major component if that would be 
representative. We recommend that you record engine fuel rate to assist 
in the determination of sulfur exposure rates, but you may use other 
data for this purpose.
    (2) When using Method 2, weighting of certification cycles, as 
described

[[Page 4699]]

Sec.  1065.1139(b)(2), record data for engine speed and engine load. 
Record sufficient ECM load parameters to determine a torque value that 
can be compared directly to engine torque as measured in the 
laboratory. You may optionally use ECM fuel rate measurements to 
determine load, but only if the same measurements can also be performed 
during laboratory testing on certification test cycles using sensors 
with comparable response characteristics. For example, you could use 
ECM fuel consumption rates for both field data and during laboratory 
tests.
    (i) Optionally, as an alternative to the parameters required in 
this paragraph (b)(2), you may use a system exhaust temperature 
measurement to represent load. This requires one recorded temperature 
that represents the aftertreatment system. We recommend that you use a 
temperature recorded at the outlet of the first major catalyst 
component. If you choose to use this option, you must use the same 
temperature sensor for both field and laboratory measurements. Do not 
compare measurements between on-engine production temperature sensors 
with laboratory temperature sensors.
    (ii) Optionally, as an alternative to the parameters required in 
this paragraph (b)(2), you may use exhaust flow and temperature 
measurements recorded in the field to support Method 2 calculations. 
Only one recorded temperature that represents the aftertreatment system 
is needed in this case. We recommend that you use a temperature 
recorded at the outlet of the first major catalyst component. Do not 
compare measurements between on-engine production temperature sensors 
with laboratory temperature sensors.
    (3) If you have an aftertreatment system which involves periodic 
regeneration events where the temperature is raised above levels 
observed during normal operation, you must record data to characterize 
each such event. Data must be recorded at a frequency of at least 1 Hz, 
and you must record the exhaust flow rate and inlet temperature of each 
key catalyst component that will experience elevated temperatures 
during the regeneration. In addition, record a flag or variable that 
can be used to determine the beginning and end of a regeneration event. 
You must record at least three such events to allow determination of 
the average regeneration profile. If you have multiple types of 
regeneration events which influence different catalyst components in 
the system, you must record this data for each type of event 
separately. Use good engineering judgment to determine the average 
duration of each type of regeneration event, and the average interval 
of time between successive regeneration events of that type. You may 
use the data recorded for this cycle determination, or any other 
representative data to determine average regeneration duration or 
regeneration interval. These values may be determined from the analysis 
used to determine emission adjustments to account for infrequent 
regeneration of aftertreatment devices in Sec.  1065.680.

Sec.  1065.1135  Determination of key aftertreatment system components.

    Most compression-ignition engine aftertreatment systems contain 
multiple catalysts, each with their own aging characteristics. However, 
in the accelerated aging protocol the system will be aged as a whole. 
Therefore, it is necessary to determine which catalyst components are 
the key components that will be used for deriving and scaling the aging 
cycle.
    (a) The primary aging catalyst in an aftertreatment system is the 
catalyst that is directly responsible for the majority of 
NOX reduction, such as a urea SCR catalyst in a compression 
ignition aftertreatment system. This catalyst will be used as the basis 
for cycle generation. If a system contains multiple SCR catalysts that 
are separated by other heat generating components that would result in 
a different rate of heat exposure, then each SCR catalyst must be 
tracked separately. Use good engineering judgment to determine when 
there are multiple primary catalyst components. An example of this 
would be a light-off SCR catalyst placed upstream of a DOC which is 
used to generate heat for regeneration and is followed by a DPF and a 
second downstream SCR catalyst. In this case, both the light-off SCR 
and the downstream SCR would have very different thermal history, and 
therefore must be tracked separately. In applications where there is no 
SCR catalyst in the aftertreatment system, the primary catalyst is the 
first oxidizing catalyst component in the system which is typically a 
DOC or catalyzed DPF.
    (b) The secondary aging catalyst in an aftertreatment system is the 
catalyst that is intended to either alter exhaust characteristics or 
generate elevated temperature upstream of the primary catalyst. An 
example of a secondary component catalyst would be a DOC placed 
upstream of an SCR catalyst, with or without a DPF in between.

Sec.  1065.1137  Determination of thermal reactivity coefficient.

    This section describes the method for determining the thermal 
reactivity coefficient(s) used for thermal heat load calculation in the 
accelerated aging protocol.
    (a) The calculations for thermal degradation are based on the use 
of an Arrhenius rate law function to model cumulative thermal 
degradation due to heat exposure. Under this model, the thermal aging 
rate constant, k, is an exponential function of temperature which takes 
the form shown in the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.146

Where:

A = frequency factor or pre-exponential factor.
Ea = thermal reactivity coefficient in kJ/mol.
R = molar gas constant.
T = catalyst temperature in K.

    (b) The process of determining Ea begins with 
determining what catalyst characteristic will be tracked as the basis 
for measuring thermal deactivation. This metric varies for each type of 
catalyst and may be determined from the experimental data using good 
engineering judgment. We recommend the following metrics; however, you 
may also use a different metric based on good engineering judgment:
    (1) Copper-based zeolite SCR. Total ammonia storage capacity is a 
key aging metric for copper-zeolite SCR catalysts, and they typically 
contain multiple types of storage sites. It is typical to model these 
catalysts using two different storage sites, one of which is more 
active for NOX reduction, as this has been shown to be an 
effective metric for tracking thermal aging. In this case, the 
recommended aging metric is the ratio between the storage capacity of 
the two sites, with more active site being in the denominator.
    (2) Iron-based zeolite SCR. Total ammonia storage capacity is a key 
aging metric for iron-zeolite SCR catalysts using a single storage site 
at 250 [deg]C for tracking thermal aging.
    (3) Vanadium SCR. Vanadium-based SCR catalysts do not feature a 
high level of ammonia storage like zeolites, therefore NOX 
reduction efficiency at lower temperatures in the range of 250 [deg]C 
is the recommended metric for tracking thermal aging.
    (4) Diesel oxidation catalysts. Conversion rate of NO to 
NO2 at 200 [deg]C is the key aging metric for tracking 
thermal aging for DOCs which are used to optimize exhaust 
characteristics for a

[[Page 4700]]

downstream SCR system. HC reduction efficiency (as measured using 
ethylene) at 200 [deg]C is the key aging metric for DOCs which are part 
of a system that does not contain an SCR catalyst for NOX 
reduction. This same guidance applies to an oxidation catalyst coated 
onto the surface of a DPF, if there is no other DOC in the system.
    (c)(1) Use good engineering judgment to select at least three 
different temperatures to run the degradation experiments at. We 
recommend selecting these temperatures to accelerated thermal 
deactivation such that measurable changes in the aging metric can be 
observed at multiple time points over the course of no more than 50 
hours. Avoid temperatures that are too high to prevent rapid catalyst 
failure by a mechanism that does not represent normal aging. An example 
of temperatures to run the degradation experiment at for a small-pore 
copper zeolite SCR catalyst is 600 [deg]C, 650 [deg]C, and 725 [deg]C.
    (2) For each temperature selected, perform testing to assess the 
aging metric at different times. These time intervals do not need to be 
evenly spaced and it is typical to run these experiments using 
increasing time intervals (e.g., after 2, 4, 8, 16, and 32 hours). Use 
good engineering judgment to stop each temperature experiment after 
sufficient data has been generated to characterize the shape of the 
deactivation behavior at a given temperature.
    (d) Generate a fit of the deactivation data generated in paragraph 
(b) of this section at each temperature using the generalized 
deactivation equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.147

Where:

[Omega] = aging metric.
k = thermal aging rate constant for a given temperature.
[Omega]EQ = aging metric at equilibrium (set to 0 unless 
there is a known activity minimum).
m = model order (the model order should be set at the lowest value 
that best fits the data at all temperatures, minimum = 1).

    (e) Using the data pairs of temperature and thermal aging rate 
constant, k, from paragraph (c)(2) of this section, determine the 
thermal reactivity coefficient, Ea, by performing a 
regression analysis of the natural log of k versus the inverse of 
temperature, T, in Kelvin. Determine Ea from the slope of 
the resulting line using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.148

Where:

m = the slope of the regression line of ln(k) versus 1/T.
R = molar gas constant.

Sec.  1065.1139  Aging cycle generation.

    Generation of the accelerated aging cycle for a given application 
involves analysis of the field data to determine a set of aging modes 
that will represent that field operation. There are two methods of 
cycle generation, each of which is described separately below. Method 1 
involves the direct application of field data and is used when the 
recorded data includes sufficient exhaust flow and temperature data to 
allow for determination of aging conditions directly from the field 
data set and must be available for all of the key components. Method 2 
is meant to be used when insufficient flow and temperature data is 
available from the field data. In Method 2, the field data is used to 
weight a set of modes derived from the laboratory certification cycles 
for a given application. These weighted modes are then combined with 
laboratory recorded flow and temperatures on the certification cycles 
to derive aging modes. There are two different cases to consider for 
aging cycle generation, depending on whether or not a given 
aftertreatment system incorporates the use of a periodic regeneration 
event. For the purposes of this section, a ``regeneration'' is any 
event where the operating temperature of some part of the 
aftertreatment system is raised beyond levels that are observed during 
normal (non-regeneration) operation. The analysis of regeneration data 
is considered separately from normal operating data.
    (a) Cycle generation process overview. The process of cycle 
generation begins with the determination of the number of bench aging 
hours. The input into this calculation is the number of real or field 
hours that represent the useful life for the target application. This 
could be given as a number of hours or miles, and for miles, the 
manufacturer must use field data and good engineering judgment to 
translate this to an equivalent number of operating hours for the 
target application. The target for the accelerated aging protocol is a 
10-time acceleration of the aging process, therefore the total number 
of aging hours is always set at useful life hours divided by 10. For 
example, if an on-highway heavy duty engine has a full useful life of 
750,000 miles and this is determined to be represented by 24,150 field 
hours, the target duration for the DAAAC protocol for this application 
would be 2,415 bench-aging hours. The 2,415 hours will then be divided 
among different operating modes that will be arranged to result in 
repetitive temperature cycling over that period. For systems that 
incorporate periodic regeneration, the total duration will be split 
between regeneration and normal (non-regeneration) operation. The 
analysis of normal operation data is given in paragraph (b) of this 
section. The analysis of regeneration data is given in paragraph (c) of 
this section.
    (b) Analysis of normal (non-regeneration) operating data. This 
analysis develops a reduced set of aging modes that represent normal 
operation. As noted earlier, there are two methods for conducting this 
analysis, based on the data available.
    (1) Method 1--Direct clustering. Use Method 1 when sufficient 
exhaust flow and temperature data are available directly from the field 
data. The data requirements for Method 1 are described in Sec.  
1065.1133(b)(1). The method involves three steps: clustering analysis, 
mode consolidation, and cycle building.
    (i) The primary method for determining modes from a field data set 
involves the use of k-means clustering. K-means clustering is a method 
where a series of observations is partitioned into set of clusters of 
``similar'' data points, where every observation is a member of a 
cluster with the nearest mean, which is referred to as the centroid of 
that cluster. The number of clusters is a parameter of the analysis, 
and the k-means algorithm generally seeks an optimal number of clusters 
to minimize the least-squares distance of all points to their 
respective centroids. There are a number of different commercially 
available software programs to perform k-means clustering, as well as 
freely available algorithm codes. K-means clustering can arrive at many 
different solutions, and we are providing the following guidance to 
help select the optimal solution for use in accelerated aging cycle 
generation. The process involves analyzing the data multiple time using 
an increasing number of clusters for each analysis. Use at least 5 
clusters, and we recommend developing solutions for the range between 5 
and 8 clusters, although you may use more if desired. Each cluster is a 
potential aging mode with a temperature and flow rate defined by the 
centroid. More clusters result in more aging modes, although this 
number may be reduced later via model consolidation.
    (ii) The cubic clustering criteria (CCC) is a metric calculated for 
each solution having a different number of clusters.

[[Page 4701]]

The computation of CCC is complex and described in more detail in the 
following reference. The CCC computation is normally available as one 
of the metrics in commercially available software packages that can be 
used for k-means clustering. The optimal solution is typically the one 
with the number of clusters corresponding to the highest CCC.
    (iii) Check each solution, starting with the one with the highest 
CCC to determine if it satisfies the following requirements:
    (A) No more than one cluster contains fewer than 3% of the data 
points.
    (B) The temperature ratio between the centroid with the maximum 
temperature and the centroid with the minimum temperature is at least 
1.6 for clusters containing more than 3% of the data points.
    (C) If that solution does not satisfy these requirements move to 
the solution with the next highest CCC.
    (iv) The process described in paragraph (c)(1)(iii) of this section 
generally works well for most data sets, but if you have difficulty 
with the CCC metric in a particular data set, use good engineering 
judgment to leverage additional criteria to help the down-selection 
process. Examples of alternate clustering metrics include a Davies-
Bouldin Index (optimizing on the minimum value) or a Calinski-Harabasz 
Index (optimize on the maximum value).
    (v) The initial candidate mode conditions are temperature and flow 
rate combinations that are the centroids for each cluster from the 
analysis in paragraph (c)(1)(iii) of this section. As part of the 
analysis, you must also determine the 10th percentile and 90th 
percentile temperatures for each cluster. These additional values may 
be needed later for the cycle heat load tuning process described in 
Sec.  1065.1143.
    (vi) The mode weight factor for a given cluster is the fraction 
data points contained within that cluster.
    (2) Method 2--Cluster-based weighting of certification cycle modes. 
Use Method 2 if there is insufficient exhaust flow and temperature data 
from the field at the time the cycle is being developed. The data 
requirements for Method 2 are described in Sec.  1065.1133(b)(2). You 
also need laboratory data recorded in the form of 1 Hz data sets for 
the regulatory duty cycles you are certifying to for your application 
as described in the standard setting part. Include exhaust flow rate 
and the inlet temperature for each key catalyst component in the 
laboratory data sets, as described in paragraph (e) of this section. 
The laboratory data sets must also include parameters that match the 
field data as described in Sec.  1065.1133(b)(2), which will be used to 
facilitate the clustering analysis.
    (i) Perform k-means clustering is described in Sec.  
1065.1133(b)(1) but using data sets containing the two parameters 
recorded in the field data sets. For example, you might use speed and 
torque, as recorded both in the field and the laboratory for Method 2 
clustering.
    (ii) Determine the fraction of points from each of the regulatory 
laboratory duty-cycles that are within each cluster, in addition to the 
overall fraction of points from the entire data set.
    (iii) For each cycle, calculate a square sum error, SSE, as 
follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.149

Where:

i = an indexing variable that represents one cluster.
N = total number of clusters.
Cycleprob = the fraction of points in a given cluster, i, 
for the regulatory duty-cycle of interest.
RefDataprob = the fraction of points in a given cluster, 
i, for the full data set.

    (iv) For each cycle, calculate a dissimilarity index as follows:
    [GRAPHIC] [TIFF OMITTED] TR24JA23.150
    
Where:

SSE = sum square error from Eq. 1065.1139-2.
Ng = total number of clusters.

    (v) If you have more than one regulatory duty cycle, weight the 
regulatory cycles.
    (A) Determine the weighting factors for a given regulatory cycle, 
wi, by solving a system of equations:
[GRAPHIC] [TIFF OMITTED] TR24JA23.151

Where:

di = dissimilarity for a given regulatory cycle, i.
dj = dissimilarity for a given regulatory cycle, j.

    (B) For example, for three duty cycles, calculate w1 as 
follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.152

    (C) Calculate subsequent wi values after calculating 
w1 as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.153

    (D) Calculate the sum of the weighting factors to verify that they 
are equal to one.
[GRAPHIC] [TIFF OMITTED] TR24JA23.154

Where:

n = number of regulatory cycles for the application.

    (vi) For each regulatory cycle determine the average exhaust flow 
and the average inlet temperature for each key catalyst. Determine the 
25th and 90th percentile inlet temperatures for the primary catalyst 
and the respective associated exhaust flow rate for each data point.
    (vii) Use the cycle weights from paragraph (b)(2)(v) of this 
section and the mode conditions from paragraph (b)(2)(vi) of this 
section to generate a set of candidate aging modes by multiplying the 
cycle weight factor, w[cycle] by 0.25 for the 25th 
percentile temperature mode, 0.65 for the 50th percentile temperature 
mode, and by 0.10 for the 90th percentile temperature mode. This will 
generate a weighted set of mode numbers three times the number of 
regulatory cycles for the target application. Each mode will have a 
target temperature and exhaust flow rate.

[[Page 4702]]

    (viii) If you have only one regulatory cycle for your application, 
use the cycle modes and weighting factors as they are given in the 
standard setting part.
    (3) Determination of mode total durations. The output for either 
method will be a set of mode exhaust conditions, with an associated 
weighting factor for each mode. Multiply the mode weight factors by the 
total number of normal operating (non-regenerating) hours, to get a 
target mode duration for each mode. This will be used in the heat load 
calculations.
    (c) Mode consolidation. Sometimes the clustering analysis process 
will generate multiple modes that are very similar to each other in 
temperature, such that although they are distinct modes they will not 
have a significantly different impact on aftertreatment aging. To 
reduce the complexity of the aging cycle, you may consolidate modes 
that are similar into a single mode as described below.
    (1) Consolidate any two or more modes which have a target 
temperature within 10 [deg]C into a single mode. If you choose to do 
this, the target temperature of the single consolidated mode is the 
temperature associated with the highest weight factor mode before 
consolidation. If the modes being consolidated all have weighting 
factors within 0.05 of each other, use the highest temperature among 
the modes.
    (2) Use the highest exhaust flow target among the modes being 
combined as the target exhaust flow for new consolidate mode.
    (3) Use the combined sum of the weighting factors for all modes 
being consolidate as the weighting factor for the new consolidated 
mode. Similarly, the total duration of the new consolidated mode is the 
sum of the durations of the modes being consolidated.
    (d) Analysis of regeneration data. Regeneration data is treated 
separately from the normal operating mode data. Generally, the target 
for accelerated aging cycle operation is to run all of the 
regenerations that would be expected over the course of useful life. If 
multiple types of regeneration are conducted on different system 
components, each type of regeneration must be analyzed separately using 
the steps in this paragraph (d). The data requirements for input into 
this process are described in Sec.  1065.1133(b)(3). The process 
described below is meant to determine a representative regeneration 
profile that will be used during aging. You may also ask us to allow 
the use of other engineering data or analysis to determine a 
representative regeneration profile.
    (1) The total number of regenerations that will be run during the 
accelerated aging process will be the same as the total number of 
regenerations over useful life. Calculate this number by dividing the 
total number of useful life hours by the interval between regenerations 
as determined in Sec.  1065.1133(b)(3).
    (2) Use the 1 Hz regeneration data to determine an appropriate 
regeneration profile. The recorded regeneration event begins when the 
engine indicates it has started regeneration using the recorded 
regeneration indicator and ends when the aftertreatment has returned 
back to the normal operating temperature after the flag indicates the 
regeneration is complete.
    (3) For each recorded regeneration, calculate the cumulative 
deactivation, Dt, using the equations in paragraph (e) of 
this section.
    (4) If you have a large number of recorded regenerations in your 
data set, select a regeneration event with a cumulative deactivation 
representing the 75th percentile of the distribution of heat loads in 
your recorded data set. If you have a smaller number of recorded 
regenerations, such that you cannot clearly identify the real 
distribution, select the recorded regeneration with the highest 
recorded cumulative deactivation.
    (5) This regeneration event will be used as the regeneration 
profile for that type of event during aging. The profile should include 
the entire event, include the temperature ramp and cool-down period.
    (6) The regeneration must be conducted in the same manner as it is 
run in the field. For instance, if the regeneration temperature is 
generated from an exothermic reaction by injecting fuel in front of a 
DOC, this methodology should also be used during bench aging.
    (7) If part of the system is at a lower temperature during 
regeneration because it is upstream of the temperature generating 
component, the set the target temperature for the aftertreatment system 
inlet to be equivalent to the system inlet temperature used during the 
highest duration non-regeneration mode, or 350 [deg]C, whichever is 
lower.
    (e) Heat load calculation and tuning for systems that have 
regeneration events. Perform this procedure after the preliminary 
cycles are completed for both normal and regeneration operation. The 
target cumulative deactivation is determined from the input field data, 
and then a similar calculation is performed for the preliminary aging 
cycle. If the cumulative deactivation for the preliminary cycle does 
not match cumulative deactivation from the field data, then the cycle 
is tuned over a series of steps until the target is matched.
    (1) The deactivation for a given catalyst is calculated for each 
time step as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.155

Where:

Di = incremental deactivation for time step i.
Ea = thermal reactivity coefficient for the catalyst as 
determined in Sec.  1065.1137.
R = molar gas constant in kJ/mol[middot]K.
Tstd = standard temperature = 293.15 K.
T = catalyst temperature in K.

    (2) Calculate the cumulative deactivation, Dt, for a 
given catalyst over a series of time steps, N, using the following 
equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.156

Where:

i = an indexing variable that represents one time step.
N = total number of cumulative deactivation time steps in the data 
set.
Di = incremental deactivation for each time step.

    (3) Calculate the cumulative deactivation, Dt, for the 
input field data set. The time step for the calculations should be 1 
second for 1-Hz input data.
    (i) First calculate Dt for the non-regeneration portion 
of the field data set. For Method 2 use the 1-Hz data from the 
regulatory cycles as the field data set.
    (ii) Divide the calculate field Dt by the number of 
hours represented in the field data set.
    (iii) Multiply the hourly Dt by the number of hours 
required to reach full useful life. This is the target 
Dt,field-normi.
    (iv) Multiply the total number of regenerations for full useful 
life by the cumulative deactivation Dt for the target 
regeneration profile determined in paragraph (d)(4) of this section. 
This is the target Dt,field-regen.
    (v) The total target cumulative deactivation for the field data, 
Dt,field, is the sum of Dt,field-normi and 
Dt,field-regen.
    (4) Calculate the cumulative deactivation for the candidate aging 
cycle generated under paragraphs (c) and (d) of this section as 
follows:
    (i) Using the modes and mode durations for normal operation 
generated in paragraph (c) of this section, calculate the cumulative 
deactivation, Dt,cycle-norm, using the

[[Page 4703]]

method given in paragraph (e)(2) of this section.
    (ii) The total cumulative deactivation for the candidate aging 
cycle, Dt, is the sum of Dt,cycle-norm and 
Dt,field-regen.
    (5) If Dt,cycle is within 1% of 
Dt,field, the candidate cycle is deemed representative and 
may be used for aging.
    (6) If Dt,cycle is not within 1% of 
Dt,field, the candidate cycle must be adjusted to meet this 
criterion using the following steps. It should be noted that if the 
Dt,cycle is outside of the criteria it will usually be lower 
than the Dt,field.
    (i) Increase the duration of the stable portion of the regeneration 
profile, which is defined as the portion of the regeneration profile 
where the temperature has completed ramping and is being controlled to 
a stationary target temperature. Note that this will increase the 
number of hours of regeneration time. You must compensate for this by 
decreasing the total number of normal operation (non-regeneration) 
hours in the cycle. Recalculate the duration of all the normal 
operation modes. You may not increase the duration of the stable 
portion of the regeneration profile by more than a factor of 2. If you 
reach this limit and you still do not meet the criteria in paragraph 
(e)(5) of this section, proceed to the next step.
    (ii) Increase the target temperature of the stable portion of the 
regeneration profile by the amount necessary to reach the target 
criteria. You may not increase this temperature higher than the 
temperature observed in the regeneration profile with the highest 
Dt observed in the field. If you reach this limit and you 
still do not meet the criteria in paragraph (e)(5) of this section, 
proceed to the next step.
    (iii) Increase the target temperature of the highest temperature 
normal operation mode. You may not increase this temperature above the 
90th percentile determined in paragraph (b)(1)(v) of this section for 
Method 1, or above the maximum temperature for the regulatory cycle 
from which the mode was derived for Method 2. If you reach this limit 
and you still do not meet the criteria in paragraph (e)(5) of this 
section, you may repeat this step using the next highest temperature 
mode, until you reach the target, or all modes have been adjusted.
    (iv) If you are unable to reach the target deactivation by 
following paragraphs (e)(6)(i) through (iii) of this section, use good 
engineering judgment to increase the number of regenerations to meet 
the criteria in paragraph (e)(5) of this section. Note that this will 
increase the total regeneration hours, therefore you must decrease the 
number of normal operation hours and re-calculate mode durations for 
the normal operation modes.
    (f) Heat load calculation and tuning for systems that do not have 
regeneration events. Follow the steps described for systems with 
regeneration events to calculate Dt,field and 
Dt,cycle, omitting the steps related to regeneration events. 
The Dt,cycle will be well below the Dt,field. 
Follow the steps given below to adjust the cycle until you meet the 
criteria in paragraph (e)(5) of this section.
    (1) Increase the temperature of the highest temperature mode. Use 
good engineering judgment to ensure that this temperature does not 
exceed the limits of the catalyst in a way that might cause rapid 
deactivation or failure via a mechanism that is not considered normal 
degradation.
    (2) Increase the duration of the highest temperature mode and 
decrease the duration of the other modes in proportion. You may not 
increase the duration highest temperature mode by more than a factor of 
2.
    (g) Final aging cycle assembly. The final step of aging cycle 
development is the assembly of the actual cycle based on the mode data 
from either paragraph (e) of this section for systems with infrequent 
regeneration, or paragraph (f) of this section for systems that do not 
incorporate infrequent regeneration. This cycle will repeat a number of 
times until the total target aging duration has been reached.
    (1) Cycle assembly with infrequent regenerations. For systems that 
use infrequent regenerations, the number of cycle repeats is equal to 
the number of regeneration events that happen over full useful life. 
The infrequent regenerations are placed at the end of the cycle. The 
total cycle duration of the aging cycle is calculated as the total 
aging duration in hours divided by the number of infrequent 
regeneration events. In the case of systems with multiple types of 
infrequent regenerations, use the regeneration with the lowest 
frequency to calculate the cycle duration.
    (i) If you have multiple types of infrequent regenerations, arrange 
the more frequent regenerations such that they are spaced evenly 
throughout the cycle.
    (ii) Determine the length of the normal (non-regeneration) part of 
the cycle by subtracting the regeneration duration, including any 
regeneration extension determined as part of cycle tuning from 
paragraph (e) of this section, from the total cycle duration. If you 
have multiple types of regeneration, then the combined total duration 
of regeneration events performed in the cycle must be subtracted from 
the total. For example, if you have one type of regeneration that is 
performed for 30 minutes every 30 cycle hours, and a second type that 
is performed for 30 minutes every 10 cycle hours (such that 3 of these 
secondary events will happen during each cycle), then you would 
subtract a total of 2 hours of regeneration time from the total cycle 
duration considering all 4 of these events.
    (iii) Divide the duration of the normal part of the cycle into 
modes based on the final weighting factors determined in paragraph (c) 
of this section following any mode consolidation.
    (iv) Place the mode with the lowest temperature first, then move to 
the highest temperature mode, followed by the next lowest temperature 
mode, and then the next highest mode, continuing in this alternating 
pattern until all modes are included.
    (v) Transition between normal modes within (60 to 300) seconds. The 
transition period is considered complete when you are within 5 [deg]C of the target temperature for the primary key component. 
Transitions may follow any pattern of flow and temperature to reach 
this target within the required 300 seconds.
    (vi) For normal modes longer than 30 minutes, you may count the 
transition time as time in mode. Account for the transition time for 
modes shorter than 30 minutes by shortening the duration of the longest 
mode by an equivalent amount of time.
    (vii) If the shortest normal operating mode is longer than 60 
minutes, you must divide the normal cycle into shorter sub-cycles with 
the same pattern in paragraph (g)(1)(iii) of this section, but with 
shorter durations, so that the pattern repeats two or more times. You 
must divide the cycle into sub-cycles until the duration of the 
shortest mode in each sub-cycle is no longer than 30 minutes. No mode 
may have a duration shorter than 15 minutes, not including transition 
time.
    (viii) If a regeneration event is scheduled to occur during a 
normal mode, shift the start of regeneration to the end of the nearest 
normal mode.
    (2) Cycle assembly without infrequent regenerations. For systems 
that do not use infrequent regenerations, the cycle will be arranged to 
achieve as much thermal cycling as possible using the following steps.
    (i) Assign a duration of 15 minutes to the mode with the lowest 
weight factor. Calculate the duration of the remaining modes in 
proportion to the final weight factors after mode durations have been

[[Page 4704]]

adjusted during heat load tuning in paragraph (f) of this section.
    (ii) Place the mode with the lowest temperature first, then move to 
the highest temperature mode, followed by the next lowest temperature 
mode, and then the next highest mode, continuing in this alternating 
pattern until all modes are included.
    (iii) Transition between normal modes within (60 to 300) seconds. 
The transition period is considered complete when you are within 5 [deg]C of the target temperature for the primary key component. 
Transitions may follow any pattern of flow and temperature to reach 
this target within the required 300 seconds.
    (iv) For normal modes longer than 30 minutes, you may count the 
transition time as time in mode. Account for the transition time for 
modes shorter than 30 minutes by shortening the duration of the longest 
mode by an equivalent amount of time.
    (v) This cycle will be repeated the number of times necessary to 
reach the target aging duration.
    (h) Determination of accelerated oil exposure targets. The target 
oil exposure rate during accelerated aging is 10 times the field 
average oil consumption rate determined in Sec.  1065.1133(a)(2). You 
must achieve this target exposure rate on a cycle average basis during 
aging. Use good engineering judgment to determine the oil exposure 
rates for individual operating modes that will achieve this cycle 
average target. For engine-based aging stands you will likely have 
different oil consumption rates for different modes depending on the 
speed and load conditions you set. For burner-based aging stands, you 
may find that you have to limit oil exposure rates at low exhaust flow 
or low temperature modes to ensure good atomization of injected oil. On 
a cycle average basis, the portion of oil exposure from the volatile 
introduction pathway (i.e., oil doped in the burner or engine fuel) 
must be between (10 to 30)% of the total. The remainder of oil exposure 
must be introduced through bulk pathway.
    (1) Determination of accelerated fuel sulfur exposure targets. The 
target sulfur exposure rate for fuel-related sulfur is determined by 
utilizing the field mean fuel rate data for the engine determined in 
Sec.  1065.1133(a)(3). Calculate the total sulfur exposure mass using 
this mean fuel rate, the total number of non-accelerated hours to reach 
full useful life, and a fuel sulfur level of 10 ppmw.
    (i) For an engine-based aging stand, if you perform accelerated 
sulfur exposure by additizing engine fuel to a higher sulfur level, 
determine the accelerated aging target additized fuel sulfur mass 
fraction, wS, as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.157

Where:

mifuel,field = field mean fuel flow rate.
mifuel,cycle = accelerated aging cycle mean fuel flow 
rate.
mSfuel,ref = reference mass of sulfur per mass of fuel = 
0.00001 kg/kg
Sacc,rate = sulfur acceleration rate = 10

Example:

mifuel,field = 54.3 kg/hr
mifuel,cycle = 34.1 kg/hr
mSfuel,ref = 0.00001 kg/kg.
Sacc,rate = 10.
[GRAPHIC] [TIFF OMITTED] TR24JA23.158

wS,target = 0.000159

    (ii) If you use gaseous SO2 to perform accelerated 
sulfur exposure, such as on a burner-based stand, calculate the target 
SO2 concentration to be introduced, xSO2,target, 
as follows:
[GRAPHIC] [TIFF OMITTED] TR24JA23.159

Where:

mifuel,field = field mean fuel flow rate.
miexhaust,cycle = mean exhaust flow rate during the 
burner aging cycle.
xSfuel,ref = reference mol fraction of sulfur in fuel = 
10 [micro]mol/mol.
Sacc,rate = sulfur acceleration rate = 10.
Mexh = molar mass of exhaust = molar mass of air.
MS = molar mass of sulfur.

Example:

mifuel,field = 54.3 kg/hr
miexhaust,cycle = 1000.8 kg/hr
xSfuel,ref = 10 [micro]mol/mol
Sacc,rate = 10
Mexh = 28.96559 g/mol
MS = 32.065 g/mol
[GRAPHIC] [TIFF OMITTED] TR24JA23.160

xSO2,target = 4.90 [micro]mol/mol

    (iii) You may choose to turn off gaseous sulfur injection during 
infrequent regeneration modes, but if you do you must increase the 
target SO2 concentration by the ratio of total aging time to 
total normal (non-regeneration) aging time.
    (2) [Reserved]

Sec.  1065.1141  Facility requirements for engine-based aging stands.

    An engine-based accelerated aging platform is built around the use 
of a compression-ignition engine for generation of heat and flow. You 
are not

[[Page 4705]]

required to use the same engine as the target application that is being 
aged. You may use any compression-ignition engine as a bench aging 
engine, and the engine may be modified as needed to support meeting the 
aging procedure requirements. You may use the same bench aging engine 
for deterioration factor determination from multiple engine families. 
The engine must be capable of reaching the combination of temperature, 
flow, NOX, and oil consumption targets required. We 
recommend using an engine platform larger than the target application 
for a given aftertreatment system to provide more flexibility to 
achieve the target conditions and oil consumption rates. You may modify 
the bench aging engine controls in any manner necessary to help reach 
aging conditions. You may bypass some of the bench aging engine exhaust 
around the aftertreatment system being aged to reach targets, but you 
must account for this in all calculations and monitoring to ensure that 
the correct amount of oil and sulfur are reaching the aftertreatment 
system. If you bypass some of the engine exhaust around the 
aftertreatment system, you must directly measure exhaust flow rate 
through the aftertreatment system. You may dilute bench aging engine 
exhaust prior to introduction to the aftertreatment system, but you 
must account for this in all calculations and monitoring to ensure that 
the correct engine conditions and the correct amount of oil and sulfur 
are reaching the aftertreatment system. Your engine-based aging stand 
must incorporate the following capabilities:
    (a) Use good engineering judgment to incorporate a means of 
controlling temperature independent of the engine. An example of such a 
temperature control would be an air-to-air heat exchanger. The 
temperature control system must be designed to prevent condensation in 
the exhaust upstream of the aftertreatment system. This independent 
temperature control is necessary to provide the flexibility required to 
reach temperature, flow, oil consumption targets, and NOX 
targets.
    (b) Use good engineering judgment to modify the engine to increase 
oil consumption rates to levels required for accelerated aging. These 
increased oil consumption levels must be sufficient to reach the bulk 
pathway exposure targets determined in Sec.  1065.1139(h). A 
combination of engine modifications and careful operating mode 
selection will be used to reach the final bulk pathway oil exposure 
target on a cycle average. You must modify the engine in a fashion that 
will increase oil consumption in a manner such that the oil consumption 
is still generally representative of oil passing the piston rings into 
the cylinder. Use good engineering judgment to break in the modified 
engine to stabilize oil consumption rates. We recommend the following 
methods of modification (in order of preference):
    (1) Install the top compression rings inverted (upside down) on all 
the cylinders of the bench aging engine.
    (2) If the approach in paragraph (b)(1) of the section is 
insufficient to reach the targets, modify the oil control rings in one 
or more cylinders to create small notches or gaps (usually no more than 
2 per cylinder) in the top portion of the oil control rings that 
contact the cylinder liner (care must be taken to avoid compromising 
the structural integrity of the ring itself).
    (c) We recommend that the engine-aging stand include a constant 
volume oil system with a sufficiently large oil reservoir to avoid oil 
``top-offs'' between oil change intervals.
    (d) If the engine-aging stand will be used for aging of systems 
that perform infrequent regenerations, the aging stand must incorporate 
a means of increasing temperature representative of the target 
application. For example, if the target application increases 
temperature for regeneration by introducing fuel into the exhaust 
upstream of an oxidation catalyst, the aging stand must incorporate a 
similar method of introducing fuel into the exhaust.
    (e) If the engine-aging stand will be used for aging systems that 
incorporate SCR-based NOX reduction, the aging stand must 
incorporate a representative means of introducing DEF at the 
appropriate location(s).
    (f) Use good engineering judgment to incorporate a means of 
monitoring oil consumption on at least a periodic basis. You may use a 
periodic drain and weigh approach to quantify oil consumption. You must 
validate that the aging stand reaches oil consumption targets prior to 
the start of aging. You must verify oil consumption during aging prior 
to each emission testing point, and at each oil change interval. 
Validate or verify oil consumption over a running period of at least 72 
hours to obtain a valid measurement. If you do not include the constant 
volume oil system recommended in paragraph (c) of this section, you 
must account for all oil additions.
    (g) Use good engineering judgment to establish an oil change 
interval that allows you to maintain relatively stable oil consumption 
rates over the aging process. Note that this interval may be shorter 
than the normal recommended interval for the engine due to the 
modifications that have been made.
    (h) If the engine-aging stand will be used for aging of systems 
that incorporate a diesel particulate filter (DPF), we recommend you 
perform secondary tracking of oil exposure by using clean (soot free) 
DPF weights to track ash loading and compare this mass of ash to the 
amount predicted using the measured oil consumption mass and the oil 
ash concentration. The mass of ash found by DPF weight should fall 
within (55 to 70)% of the of mass predicted from oil consumption 
measurements.
    (i) Incorporate a means of introducing lubricating oil into the 
engine fuel to enable the volatile pathway of oil exposure. You must 
introduce sufficient oil to reach the volatile pathway oil exposure 
targets determined in paragraph (h) of this section. You must measure 
the rate of volatile pathway oil introduction on a continuous basis.
    (j) If you perform sulfur acceleration by increasing the sulfur 
level of the engine fuel, you must meet the target sulfur level within 
5 ppmw. Verify the sulfur level of the fuel prior to 
starting aging, or whenever a new batch of aging fuel is acquired.
    (k) If you use gaseous SO2 for sulfur acceleration, you 
must incorporate a means to introduce the gaseous SO2 
upstream of the aftertreatment system. Use good engineering judgment to 
ensure that gaseous SO2 is well mixed prior to entering the 
aftertreatment system. You must monitor the rate of gaseous 
SO2 introduction on a continuous basis.

Sec.  1065.1143  Requirements for burner-based aging stands.

    A burner-based aging platform is built using a fuel-fired burner as 
the primary heat generation mechanism. The burner must utilize diesel 
fuel and it must produce a lean exhaust gas mixture. You must configure 
the burner system to be capable of controlling temperature, exhaust 
flow rate, NOX, oxygen, and water to produce a 
representative exhaust mixture that meets the accelerated aging cycle 
targets for the aftertreatment system to be aged. You may bypass some 
of the bench aging exhaust around the aftertreatment system being aged 
to reach targets, but you must account for this in all calculations and 
monitoring to ensure that the correct amount of oil and sulfur are 
reaching the aftertreatment system. The burner system must incorporate 
the following capabilities:
    (a) Directly measure the exhaust flow through the aftertreatment 
system being aged.

[[Page 4706]]

    (b) Ensure transient response of the system is sufficient to meet 
the cycle transition time targets for all parameters.
    (c) Incorporate a means of oxygen and water control such that the 
burner system is able to generate oxygen and water levels 
representative of compression-ignition engine exhaust.
    (d) Incorporate a means of oil introduction for the bulk pathway. 
You must implement a method that introduces lubricating oil in a region 
of the burner that does not result in complete combustion of the oil, 
but at the same time is hot enough to oxidize oil and oil additives in 
a manner similar to what occurs when oil enters the cylinder of an 
engine past the piston rings. Care must be taken to ensure the oil is 
properly atomized and mixed into the post-combustion burner gases 
before they have cooled to normal exhaust temperatures, to insure 
proper digestion and oxidation of the oil constituents. You must 
measure the bulk pathway oil injection rate on a continuous basis. You 
must validate that this method produces representative oil products 
using the secondary method in Sec.  1065.1141(h) regardless of whether 
you will use the burner-based aging stand to age systems which include 
a DPF. Use good engineering judgment to select a DPF for the initial 
validation of the system. Perform this validation when the burner-based 
aging stand is first commissioned or if any system modifications are 
made that affect the oil consumption introduction method. We also 
recommend that you examine ash distribution on the validation DPF in 
comparison to a representative engine aged DPF.
    (e) Incorporate a means of introducing lubricating oil into the 
burner fuel to enable the volatile pathway of oil exposure. You must 
introduce sufficient oil to reach the volatile pathway oil exposure 
targets determined in Sec.  1065.1139(h). You must measure the rate of 
volatile pathway oil introduction on a continuous basis.
    (f) If the burner-based aging stand will be used for aging of 
systems that perform infrequent regenerations, the aging stand must 
incorporate a means of increasing temperature representative of the 
target application. For example, if the target application increases 
temperature for regeneration by introducing fuel into the exhaust 
upstream of an oxidation catalyst, the aging stand must incorporate a 
similar method of introducing fuel into the exhaust.
    (g) If the burner-based aging stand will be used for aging of 
systems that incorporate SCR-based NOX reduction, the aging 
stand must incorporate a representative means of introducing DEF at the 
appropriate location(s).
    (h) If the burner-based aging stand will be used for aging of 
systems that incorporate a diesel particulate filter (DPF), we 
recommend you perform secondary tracking of oil exposure by using clean 
(soot free) DPF weights to track ash loading and compare this mass of 
ash to the amount predicted using the measured oil consumption mass and 
the oil ash concentration. The mass of ash found by DPF weight should 
fall within (55 to 70)% of the of mass predicted from oil consumption 
measurements.
    (i) You must incorporate a means to introduce the gaseous 
SO2 upstream of the aftertreatment system. Use good 
engineering judgment to ensure that gaseous SO2 is well 
mixed prior to entering the aftertreatment system. You must monitor the 
rate of gaseous SO2 introduction on a continuous basis.

Sec.  1065.1145  Execution of accelerated aging, cycle tracking, and 
cycle validation criteria.

    The aging cycle generally consists first of practice runs to 
validate and tune the final cycle, followed by the actual running of 
the repeat cycles needed to accumulate field equivalent hours to reach 
full useful life. During the course of the aging run, various aging 
parameters are tracked to allow verification of proper cycle execution, 
as well as to allow for correction of the aging parameters to stay 
within the target limits.
    (a) Preliminary cycle validation runs. Prior to the start of aging, 
conduct a number of practice runs to tune the cycle parameters. It is 
recommended that initial practice runs be conducted without the 
aftertreatment installed, but with the backpressure of the 
aftertreatment simulated to help ensure that the tuned cycle is 
representative. For final cycle tuning, including regenerations, it is 
recommended to use a duplicate or spare aftertreatment system of 
similar design to the target system, to avoid damage or excessive 
initial aging during the tuning. However, it is permissible to conduct 
final tuning using the target system being aged, but you must limit the 
total duration to no more than 100 field equivalent hours (10 hours of 
accelerated aging), including both thermal and chemical components. The 
process followed for these initial runs will vary depending on whether 
you are using an engine-based platform or a burner-based platform.
    (1) Engine-based platform. (i) Initial cycle development. It will 
be necessary to determine a set of engine modes that will generate the 
required combinations of temperature, exhaust flow, oil consumption, 
and NOX to meet the target aging requirements. The 
development of these modes will be an iterative process using the 
engine and independent temperature control features of the aging stand. 
This process assumes that you have already implemented the oil 
consumption increase modifications, and that these have already been 
stabilized and validated to reach the necessary levels of bulk oil 
exposure. In general, we recommend the use of higher engine speeds and 
loads to generate the desired oil consumption, leveraging the 
temperature controls as needed to lower temperature to the targets. 
Several iterations will likely be needed to reach all targets. Note 
that during transitions you may utilize any combination of conditions 
necessary to help primary component catalysts reach the target 
temperature and flow conditions within no more than 5 minutes. For 
example, you may use a higher exhaust flow rate and lower temperature 
to rapidly cool the aftertreatment system to the next temperature. 
NOX targets do not need to be met during transitions. It is 
permissible to deviate from engine-out NOX emission targets 
if needed to reach the temperature, exhaust flow, and oil consumption 
targets. We recommend that you maintain a NOX level that is 
at the target level or higher, but you may lower NOX by up 
to 25%, if necessary, on some modes. Note that validation of oil 
consumption requires at least 72 hours of operation. Tune the 
parameters for infrequent regeneration towards then end of this initial 
development process (such as hydrocarbon injection schedules and 
temperature ramp rates).
    (ii) Final cycle validation. Once the cycle is tuned, conduct a 
final run using the target aftertreatment system to verify conditions 
and log temperatures for heat load calculation. Using the recorded 
cycle data, calculate Dt for all primary component catalysts 
to ensure that you are matching the desired Dt,cycle 
targets. If you are not within 3% of the target 
Dt,cycle, adjust the cycle accordingly. Calculate 
Dt for any secondary catalyst components to verify that they 
are within 3% of either the target Dt or the 
target aging metric. Note that the accelerated aging methodology 
assumes that the relationship between the temperature of the primary 
and secondary catalyst components will the be same as the field 
observations. If this relationship deviates in the lab by having more 
or less heat transfer through the system, it may be necessary to modify 
that relationship on the aging stand. You may need to take measures

[[Page 4707]]

such as adding or removing insulation or utilize external cooling fans 
to help these parameters match more closely.
    (2) Burner-based platform. (i) Cycle development. The burner-based 
platform will be able to meet the exhaust flow, temperature, 
NOX, and oil consumption targets directly without the need 
for additional cycle development. This process assumes that you have 
already implemented and validated your oil consumption exposure methods 
to reach the necessary levels of bulk oil exposure. In addition, you 
must meet the oxygen and water targets during aging modes within 2% for oxygen and 2% for water. Note that during 
transitions you may utilize any combination of conditions necessary to 
help primary component catalysts reach the target temperature and flow 
conditions within no more than 5 minutes. For example, you may use a 
higher exhaust flow rate and lower temperature to rapidly cool the 
aftertreatment system to the next temperature. NOX, oxygen, 
and water targets do not need to be met during transitions.
    (ii) Final cycle validation. Once the cycle is tuned, conduct a 
final run using the target aftertreatment system to verify conditions 
and log temperatures for heat load calculation. Using the recorded 
cycle data, calculate Dt for all primary components 
catalysts to ensure that you are matching the desired 
Dt,cycle targets. If you are not within 3% of 
the target Dt,cycle, adjust the cycle accordingly. Calculate 
Dt for any secondary catalyst components to check that they 
are within 3% of either the target Dt or the 
target aging metric. Note that the accelerated aging methodology 
assumes that the relationship between the temperature of the primary 
and secondary catalyst components will the be same as that observed in 
the field. If this relationship deviates in the lab by having more or 
less heat transfer through the system, it may be necessary to modify 
that relationship on the aging stand. You may need to take measures 
such as adding or removing insulation or utilize external cooling fans 
to help these parameters match more closely.
    (b) Aftertreatment break in. Break in the emission-data engine and 
aftertreatment prior to the initial zero-hour test by running both on 
an engine dynamometer as described in subpart E of this part. Use good 
engineering judgment to develop a representative cycle that represents 
the field data. You may use the same data used for accelerated aging 
cycle development or other data. If your system utilizes infrequent 
regeneration, include at least one complete regeneration event, but we 
recommend that you include at least two such events to stabilize 
emissions performance. Your break in process must include at least 125 
hours of engine operation with the aftertreatment system. You may ask 
to use a longer break in duration based on good engineering judgment, 
to ensure that emission performance is stabilized prior to the zero-
hour testing.
    (c) Initial emission testing. Prior to the start of accelerated 
aging conduct the initial zero-hour emission test and any required 
engine dynamometer aging following the requirements of the standard 
setting part for your engine. Dynaometer aging hours count toward the 
total aging hours.
    (d) Accelerated aging. Following zero-hour emission testing and any 
engine dynamometer aging, perform accelerated aging using the cycle 
validated in either paragraph (a)(1) or (2) of this section. Repeat the 
cycle the number of times required to reach full useful life equivalent 
aging. Interrupt the aging cycle as needed to conduct any scheduled 
intermediate emission tests, clean the DPF of accumulated ash, and for 
any facility releated reasons. We recommended you interrupt aging at 
the end of a given aging cycle, following the completion of any 
scheduled infrequent regeneration event.
    (e) QA tracking and validation. During aging, track a number of 
aging parameters to ensure that fall within the required limits. 
Correct aging parameters as need to remain within the required control 
limits.
    (1) Thermal load tracking. For each primary catalyst component, 
generate a target line which describes the relationship between aging 
hours on the cycle and cumulative deactivation, Dt. Generate 
control limit lines that are 3% of the target line. You 
must remain within these control limits over the course of aging. 
Adjust aging parameters as needed to remain within these limits for the 
primary catalyst components. For each secondary catalyst component, 
generate both a target Dt line and a line describing the 
target behavior of the aging metric directly. You must remain within 
either 10% of either the Dt line or 3% of the aging metric target line for any secondary catalyst 
component. Adjust aging parameters as needed to remain within these 
limits noting that you must remain within limits for the primary 
components. Adjusting the secondary catalyst aging may require altering 
heat transfer through the system to make it more representative of the 
field aging.
    (2) Oil consumption tracking. Generate a target oil consumption 
line for both the bulk and volatile pathway which describes the 
relationship between oil exposure and aging hours on the cycle. For the 
engine-based stand the control limits are 10% for total oil 
consumption, noting that the volatile pathway must not exceed 30% of 
the total. For the burner-based stand, the controls limits are 5% for both pathways, which are tracked separately.
    (i) Changing engine oil. For an engine-based platform, periodically 
change engine oil to maintain stable oil consumption rates and maintain 
the health of the aging engine. Interrupt aging as needed to perform 
oil changes. Perform a drain-and-weigh measurement. Following an oil 
change you must run at least 4 hours with the exhaust bypassing the 
aftertreatment system to stabilize the new oil. If you see a sudden 
change in oil consumption it may be necessary to stop aging and either 
change oil or correct an issue with the accelerated oil consumption. If 
the aging engine requires repairs to correct an oil consumption issue 
in the middle of aging, you must re-validate the oil consumption rate 
for 72 hours before you continue aging. The engine exhaust should be 
left bypassing the aftertreatment system until the repaired engine has 
been validated.
    (ii) Secondary oil consumption validation. If your aftertreatment 
includes a diesel particulate filter, we recommend that you perform 
secondary validation of oil consumption by using clean (soot free) DPF 
weights to track ash loading and compare this mass of ash to the amount 
predicted using the measured oil consumption mass and the oil ash 
concentration. The mass of ash found by DPF weight should fall within a 
range of (55 to 70)% of the of mass predicted from oil consumption 
measurements. Perform this validation at the end of aging, at any 
intermediate emission test points, and at any point where you need to 
clean the DPF of accumulated ash in according with recommended 
maintenance.
    (iii) Sulfur tracking. Generate a fuel sulfur exposure line 
describing the relationship between aging hours and cumulative target 
sulfur exposure mass. The control limits for sulfur exposure are 3%. Log actual fuel consumption and the measured fuel sulfur 
level of the current batch of fuel (if you are doping fuel to 
accelerate sulfur exposure) for engine stand aging. Use these 
measurements to ensure that sulfur exposure remains within the control 
limits. Adjust sulfur doping levels in the fuel from batch to batch as 
needed to stay within limits. If you use gaseous SO2 for 
sulfur acceleration, monitor the mass flow rate of the gaseous sulfur. 
Use these measurements to calculate total

[[Page 4708]]

sulfur mass exposure, and correct SO2 gas flow rates as 
needed to stay within the control limits.
    (f) Emission testing at intermediate and final test points. Conduct 
emission testing at the end of aging and at any intermediate emission 
test points as described in the standard setting part. Following 
installation of the aged aftertreatment system on the emission-data 
engine at intermediate or final test points, prior to the start of 
emission testing, use good engineering judgment to operate the engine 
and aftertreatment system for a number of hours to stabilize emission 
controls and to allow any adaptive controls to update. Declare the 
number of stabilization hours prior to the start of the accelerated 
aging program.

PART 1066--VEHICLE-TESTING PROCEDURES

0
269. The authority citation for part 1066 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
270. Amend Sec.  1066.110 by revising paragraphs (b)(1)(vi), (b)(2)(i) 
and (b)(2)(v) introductory text to read as follows:

Sec.  1066.110  Equipment specifications for emission sampling systems.

* * * * *
    (b) * * *
    (1) * * *
    (vi) You must seal your system to the extent necessary to ensure 
that any remaining leaks do not affect your ability to demonstrate 
compliance with the applicable standards in this chapter. We recommend 
that you seal all known leaks.
* * * * *
    (2) * * *
    (i) For PM background measurement, the following provisions apply 
in addition to the provisions in 40 CFR 1065.140(b):
* * * * *
    (v) If you choose to dilute the exhaust by using a remote mix tee, 
which dilutes the exhaust at the tailpipe, you may use the following 
provisions consistent with good engineering judgment, as long as they 
do not affect your ability to demonstrate compliance with the 
applicable standards in this chapter:
* * * * *

0
271. Amend Sec.  1066.220 by revising paragraph (b) to read as follows:

Sec.  1066.220  Linearity verification for chassis dynamometer systems.

* * * * *
    (b) Performance requirements. If a measurement system does not meet 
the applicable linearity criteria in Table 1 of this section, correct 
the deficiency by re-calibrating, servicing, or replacing components as 
needed. Repeat the linearity verification after correcting the 
deficiency to ensure that the measurement system meets the linearity 
criteria. Before you may use a measurement system that does not meet 
linearity criteria, you must demonstrate to us that the deficiency does 
not adversely affect your ability to demonstrate compliance with the 
applicable standards in this chapter.
* * * * *

0
272. Amend Sec.  1066.301 by revising paragraph (b) to read as follows:

Sec.  1066.301  Overview of road-load determination procedures.

* * * * *
    (b) The general procedure for determining road-load force is 
performing coastdown tests and calculating road-load coefficients. This 
procedure is described in SAE J1263 and SAE J2263 (incorporated by 
reference in Sec.  1066.1010). Continued testing based on the 2008 
version of SAE J2263 is optional, except that it is no longer available 
for testing starting with model year 2026. This subpart specifies 
certain deviations from those procedures for certain applications.
* * * * *

0
273. Amend Sec.  1066.415 by revising paragraph (e)(2) to read as 
follows:

Sec.  1066.415  Vehicle operation.

* * * * *
    (e) * * *
    (2) If vehicles have features that preclude dynamometer testing, 
you may modify these features as necessary to allow testing, consistent 
with good engineering judgment, as long as it does not affect your 
ability to demonstrate that your vehicles comply with the applicable 
standards in this chapter. Send us written notification describing 
these changes along with supporting rationale.
* * * * *

0
274. Amend Sec.  1066.420 by revising paragraph (b) to read as follows:

Sec.  1066.420  Test preparation.

* * * * *
    (b) Minimize the effect of nonmethane hydrocarbon contamination in 
the hydrocarbon sampling system for vehicles with compression-ignition 
engines as follows:
    (1) For vehicles at or below 14,000 pounds GVWR, account for 
contamination using one of the following methods:
    (i) Introduce zero and span gas during analyzer calibration using 
one of the following methods, noting that the hydrocarbon analyzer flow 
rate and pressure during zero and span calibration (and background bag 
reading) must be exactly the same as that used during testing to 
minimize measurement errors:
    (A) Close off the hydrocarbon sampling system sample probe and 
introduce gases downstream of the probe making sure that you do not 
pressurize the system.
    (B) Introduce zero and span gas directly at the hydrocarbon 
sampling system probe at a flow rate greater than 125% of the 
hydrocarbon analyzer flow rate allowing some gas to exit probe inlet.
    (ii) Perform the contamination verification in paragraph (b)(2) of 
this section, except use 0.5 [mu]mol/mol in 40 CFR 1065.520(f)(8)(iii).
    (2) For vehicles above 14,000 pounds GVWR, verify the amount of 
nonmethane hydrocarbon contamination as described in 40 CFR 
1065.520(f).
* * * * *

0
275. Amend Sec.  1066.710 by revising the introductory text and 
paragraph (b)(1), removing Figure 1 of Sec.  1066.710, and adding 
paragraph (f) to read as follows:

Sec.  1066.710  Cold temperature testing procedures for measuring CO 
and NMHC emissions and determining fuel economy.

    This section describes procedures for measuring carbon monoxide 
(CO) and nonmethane hydrocarbon (NMHC) emissions and determining fuel 
economy on a cold day using the FTP test cycle (see Sec.  1066.801).
* * * * *
    (b) * * *
    (1) Ambient temperature for emission tests. Measure and record 
ambient temperature in the test cell at least once every 60 seconds 
during the sampling period. The temperature must be (-7.0 1.7)[deg]C at the start of the test and average temperature must 
be (-7.0 2.8)[deg]C during the test. Instantaneous 
temperature values may be above -4.0[deg]C or below -9.0[deg]C, but not 
for more than 3 minutes at a time during the test. At no time may the 
ambient temperatures be below -12.0[deg]C or above -1.0[deg]C.
* * * * *
    (f) The following figure illustrates the cold temperature testing 
sequence for measuring CO and NMHC emissions and determining fuel 
economy:

Figure 1 to paragraph (f) Sec.  1066.710--Cold Temperature Testing 
Sequence for Measuring CO and NMHC Emissions and Determining Fuel 
Economy

[[Page 4709]]

[GRAPHIC] [TIFF OMITTED] TR24JA23.161

0
276. Amend Sec.  1066.815 by revising paragraph (d)(1)(ii) to read as 
follows:

Sec.  1066.815  Exhaust emission test procedures for FTP testing.

* * * * *
    (d) * * *
    (1) * * *
    (ii) Simultaneously start any electronic integrating devices, 
continuous data recording, and batch sampling before attempting to 
start the engine. Initiate the sequence of points in the test cycle 
when the engine starts. Place the vehicle in gear 15 seconds after 
engine starting, which is 5 seconds before the first acceleration.
* * * * *

0
277. Amend Sec.  1066.831 by revising paragraph (d) to read as follows:

Sec.  1066.831  Exhaust emission test procedures for aggressive 
driving.

* * * * *
    (d) For diesel-fueled vehicles, measure THC emissions on a 
continuous basis. For separate measurement of the city and highway test 
intervals as described in paragraph (c) of this section, perform 
separate calculations for each portion of the test cycle.
* * * * *

0
278. Amend Sec.  1066.835 by revising paragraphs (f)(1), (2), and 
(f)(3)(iii) to read as follows:

Sec.  1066.835  Exhaust emission test procedure for SC03 emissions.

* * * * *
    (f) * * *
    (1) Ambient temperature and humidity. Measure and record ambient 
temperature and humidity in the test cell at least once every 30 
seconds during the sampling period. Alternatively, if you collect data 
of at least once every 12 seconds, you may use a moving average of up 
to 30 second intervals to measure and record ambient temperature and 
humidity. Control ambient temperature throughout the test sequence to 
(35.0  3.0)[deg]C. Control ambient temperature during 
emission sampling to (33.6 to 36.4)[deg]C on average. Control ambient 
humidity during emission sampling as described in Sec.  1066.420(d).
    (2) Conditions before testing. Use good engineering judgment to 
demonstrate that you meet the specified temperature and humidity 
tolerances in paragraph (f)(1) of this section during the 
preconditioning cycle and during the vehicle soak period in paragraph 
(c)(6) of this section.
    (3) * * *
    (iii) Determine radiant energy intensity experienced by the vehicle 
as the average value between two measurements along the vehicle's 
centerline, one at the base of the windshield and the other at the 
bottom of the rear window (or equivalent location for vehicles without 
a rear window). This value must be (850  45)

[[Page 4710]]

W/m\2\. Instruments for measuring radiant energy intensity must meet 
the following minimum specifications:
* * * * *

0
279. Amend Sec.  1066.845 by revising paragraphs (c), (f)(3) and (g) 
and adding paragraph (h) to read as follows:

Sec.  1066.845  AC17 air conditioning efficiency test procedure.

* * * * *
    (c) Ambient conditions. Measure and control ambient conditions as 
specified in Sec.  1066.835(f), except that you must control ambient 
temperature during emission sampling to (22.0 to 28.0)[deg]C throughout 
the test and (23.5 to 26.5)[deg]C on average. These tolerances apply to 
the combined SC03 and HFET drive cycles during emission sampling. Note 
that you must set the same ambient temperature target for both the air 
conditioning on and off portions of emission sampling. Control ambient 
temperature during the preconditioning cycle and 30 minute soak to 
(25.0  5.0)[deg]C. For these same modes with no emission 
sampling, target the specified ambient humidity levels, but you do not 
need to meet the humidity tolerances. Note that solar heating is 
disabled for certain test intervals as described in this section.
* * * * *
    (f) * * *
    (3) Turn on solar heating within one minute after turning off the 
engine. Once the solar energy intensity reaches 805 W/m\2\, let the 
vehicle soak for (30  1) minutes. You may alternatively 
rely on prior measurements to start the soak period after a defined 
period of warming up to the specified solar heat load. Close the 
vehicle's windows at the start of the soak period; ensure that the 
windows are adequately closed where instrumentation and wiring pass 
through to the interior.
* * * * *
    (g) Calculations. (1) Determine the mass of CO2 
emissions for each of the two test intervals as described in Sec.  
1066.605.
    (2) Calculate separate composite mass-weighted emissions of 
CO2, eCO2-AC17compAC[status], representing the 
average of the SC03 and HFET emissions, in grams per mile for operation 
with the vehicle's air conditioner and the solar heating on and off 
using the following equation:
[GRAPHIC] [TIFF OMITTED] TR24JA23.162

Where:

mSC03 = mass emissions from the SC03 test interval, in 
grams.
DSC03 = measured driving distance during the SC03 test 
interval, in miles.
mHFET = mass emissions from the HFET test interval, in 
grams.
DHFET = measured driving distance during the HFET test 
interval, in miles.

    (3) Calculate the incremental CO2 emissions due to air 
conditioning operation by subtracting the composite mass-weighted 
emissions of CO2 with the vehicle's air conditioner and the 
solar heating on, eCO2-AC17compACon, from the composite 
mass-weighted emissions of CO2 with the vehicle's air 
conditioner and the solar heating off, eCO2-AC17compACoff.
    (h) Record information for each test as specified in Sec.  
1066.695. Emission results and the results of all calculations must be 
reported for each phase of the test. The manufacturer must also report 
the following information for each vehicle tested: interior volume, 
climate control system type and characteristics, refrigerant used, 
compressor type, and evaporator/condenser characteristics.

0
280. Amend Sec.  1066.1001 by adding definitions of ``Charge-
depleting'' and ``Charge-sustaining'' in alphabetical order and 
revising the definition of ``Test interval'' to read as follows:

Sec.  1066.1001  Definitions.

* * * * *
    Charge-depleting means relating to the test interval of a plug-in 
hybrid engine or powertrain in which the engine or powertrain consumes 
electric energy from the RESS that has been charged from an external 
power source until the RESS is depleted to the point that a test 
interval qualifies as charge-sustaining. The engine might consume fuel 
to produce power during a charge-depleting test interval.
    Charge-sustaining means relating to the test interval of a plug-in 
hybrid engine or powertrain in which the engine or powertrain consumes 
fuel to produce power such that the battery's net-energy change meets 
the end-of-test criterion of SAE J1711 or SAE J2711, as applicable 
(incorporated by reference in Sec.  1066.1010).
* * * * *
    Test interval means a period over which a vehicle's emission rates 
are determined separately. For many standards, compliance with the 
standard is based on a weighted average of the mass emissions from 
multiple test intervals. For example, the standard-setting part may 
specify a complete duty cycle as a cold-start test interval and a hot-
start test interval. In cases where multiple test intervals occur over 
a duty cycle, the standard-setting part may specify additional 
calculations that weight and combine results to arrive at composite 
values for comparison against the applicable standards in this chapter.
* * * * *

0
281. Amend Sec.  1066.1005 by revising paragraphs (b), (g), and (h) to 
read as follows:

Sec.  1066.1005  Symbols, abbreviations, acronyms, and units of 
measure.

* * * * *
    (b) Symbols for chemical species. This part uses the following 
symbols for chemical species and exhaust constituents:

   Table 2 to Paragraph (b) of Sec.   1066.1005--Symbols for Chemical
                    Species and Exhaust Constituents
------------------------------------------------------------------------
                 Symbol                              Species
------------------------------------------------------------------------
CH4....................................  methane.
CH3OH..................................  methanol.
CH2O...................................  formaldehyde.
C2H4O..................................  acetaldehyde.
C2H5OH.................................  ethanol.
C2H6...................................  ethane.
C3H7OH.................................  propanol.

[[Page 4711]]

 
C3H8...................................  propane.
C4H10..................................  butane.
C5H12..................................  pentane.
CO.....................................  carbon monoxide.
CO2....................................  carbon dioxide.
H2O....................................  water.
HC.....................................  hydrocarbon.
N2.....................................  molecular nitrogen.
NMHC...................................  nonmethane hydrocarbon.
NMHCE..................................  nonmethane hydrocarbon
                                          equivalent.
NMOG...................................  nonmethane organic gas.
NO.....................................  nitric oxide.
NO2....................................  nitrogen dioxide.
NOX....................................  oxides of nitrogen.
N2O....................................  nitrous oxide.
O2.....................................  molecular oxygen.
OHC....................................  oxygenated hydrocarbon.
PM.....................................  particulate matter.
THC....................................  total hydrocarbon.
THCE...................................  total hydrocarbon equivalent.
------------------------------------------------------------------------

* * * * *
    (g) Constants. (1) This part uses the following constants for the 
composition of dry air:

   Table 7 to Paragraph (g)(1) of Sec.   1066.1005--Constants for the
                         Composition of Dry Air
------------------------------------------------------------------------
              Symbol                      Quantity            mol/mol
------------------------------------------------------------------------
xArair............................  amount of argon in           0.00934
                                     dry air.
xCO2air...........................  amount of carbon            0.000375
                                     dioxide in dry air.
xN2air............................  amount of nitrogen           0.78084
                                     in dry air.
xO2air............................  amount of oxygen in         0.209445
                                     dry air.
------------------------------------------------------------------------

    (2) This part uses the following molar masses or effective molar 
masses of chemical species:

    Table 8 to Paragraph (g)(2) of Sec.   1066.1005--Molar Masses or
               Effective Molar Masses of Chemical Species
------------------------------------------------------------------------
                                                       g/mol (10-
           Symbol                 Quantity     \3\[middot]kg[middot]mol-
                                                          \1\)
------------------------------------------------------------------------
Mair........................  molar mass of                28.96559
                               dry air \1\.
MH2O........................  molar mass of                18.01528
                               water.
------------------------------------------------------------------------
\1\ See paragraph (g)(1) of this section for the composition of dry air.

    (3) This part uses the following molar gas constant for ideal 
gases:

               Table 9 to Paragraph (g)(3) of Sec.   1066.1005--Molar Gas Constant for Ideal Gases
----------------------------------------------------------------------------------------------------------------
                                                                                            J/(mol[middot]K)
                                                                                       (m\2\[middot]kg[middot]s-
                        Symbol                                     Quantity                 \2\[middot]mol-
                                                                                           \1\[middot]K-\1\)
----------------------------------------------------------------------------------------------------------------
R.....................................................            molar gas constant              8.314472
----------------------------------------------------------------------------------------------------------------

    (h) Prefixes. This part uses the following prefixes to define a 
quantity:

   Table 10 to Paragraph (h) of Sec.   1066.1005--Prefixes to Define a
                                Quantity
------------------------------------------------------------------------
              Symbol                      Quantity             Value
------------------------------------------------------------------------
n.................................  nano................          10-\9\
[mu]..............................  micro...............          10-\6\
m.................................  milli...............          10-\3\
c.................................  centi...............          10-\2\
k.................................  kilo................           10\3\
M.................................  mega................           10\6\
------------------------------------------------------------------------

0
282. Revise Sec.  1066.1010 to read as follows:

Sec.  1066.1010  Incorporation by reference.

    Certain material is incorporated by reference into this part with 
the approval of the Director of the Federal Register under 5 U.S.C. 
552(a) and 1 CFR part 51. To enforce any edition other than that 
specified in this section, EPA must publish a document in the Federal 
Register and the material must be available to the public. All approved 
incorporation by reference (IBR) material is available for inspection 
at EPA and at the National Archives and Records Administration (NARA). 
Contact EPA at: U.S. EPA, Air and Radiation Docket Center, WJC West 
Building, Room 3334, 1301 Constitution Ave. NW, Washington, DC 20004; 
www.epa.gov/dockets; (202) 202-1744. For information on inspecting this 
material at NARA, visit www.archives.gov/federal-register/cfr/ibr-locations.html or email [email protected]. The material may be 
obtained from the following sources:

[[Page 4712]]

    (a) National Institute of Standards and Technology (NIST), 100 
Bureau Drive, Stop 1070, Gaithersburg, MD 20899-1070; (301) 975-6478; 
www.nist.gov.
    (1) NIST Special Publication 811, 2008 Edition, Guide for the Use 
of the International System of Units (SI), Physics Laboratory, March 
2008; IBR approved for Sec. Sec.  1066.20(a); 1066.1005.
    (2) [Reserved]
    (b) SAE International, 400 Commonwealth Dr., Warrendale, PA 15096-
0001; (877) 606-7323 (U.S. and Canada) or (724) 776-4970 (outside the 
U.S. and Canada); www.sae.org.
    (1) SAE J1263 MAR2010, Road Load Measurement and Dynamometer 
Simulation Using Coastdown Techniques, Revised March 2010, (``SAE 
J1263''); IBR approved for Sec. Sec.  1066.301(b); 1066.305(a); 
1066.310(b).
    (2) SAE J1634 JUL2017, Battery Electric Vehicle Energy Consumption 
and Range Test Procedure, Revised July 2017, (``SAE J1634''); IBR 
approved for Sec.  1066.501(a).
    (3) SAE J1711 JUN2010, Recommended Practice for Measuring the 
Exhaust Emissions and Fuel Economy of Hybrid-Electric Vehicles, 
Including Plug-In Hybrid Vehicles, Revised June 2010, (``SAE J1711''); 
IBR approved for Sec. Sec.  1066.501(a); 1066.1001.
    (4) SAE J2263 DEC2008, Road Load Measurement Using Onboard 
Anemometry and Coastdown Techniques, Revised December 2008; IBR 
approved for Sec. Sec.  1066.301(b); 1066.305; 1066.310(b).
    (5) SAE J2263 MAY2020, (R) Road Load Measurement Using Onboard 
Anemometry and Coastdown Techniques, Revised May 2020, (``SAE J2263''); 
IBR approved for Sec. Sec.  1066.301(b); 1066.305; 1066.310(b).
    (6) SAE J2264 JAN2014, Chassis Dynamometer Simulation of Road Load 
Using Coastdown Techniques, Revised January 2014, (``SAE J2264''); IBR 
approved for Sec.  1066.315.
    (7) SAE J2711 MAY2020, (R) Recommended Practice for Measuring Fuel 
Economy and Emissions of Hybrid-Electric and Conventional Heavy-Duty 
Vehicles, Revised May 2020, (``SAE J2711''); IBR approved for 
Sec. Sec.  1066.501(a); 1066.1001.
    (8) SAE J2951 JAN2014, Drive Quality Evaluation for Chassis 
Dynamometer Testing, Revised January 2014, (``SAE J2951''); IBR 
approved for Sec.  1066.425(j).

PART 1068--GENERAL COMPLIANCE PROVISIONS FOR HIGHWAY, STATIONARY, 
AND NONROAD PROGRAMS

0
283. The authority citation for part 1068 continues to read as follows:

    Authority: 42 U.S.C. 7401-7671q.

0
284. Amend Sec.  1068.1 by revising paragraphs (a)(2), (4), (5), (6), 
(8), (9), and (13) and adding paragraph (a)(15) to read as follows:

Sec.  1068.1  Does this part apply to me?

    (a) * * *
    (2) This part 1068 applies for heavy-duty motor vehicles and motor 
vehicle engines we regulate under 40 CFR parts 1036 and 1037. This 
includes trailers. This part 1068 applies to heavy-duty motor vehicles 
and motor vehicle engines certified under 40 CFR part 86 to the extent 
and in the manner specified in 40 CFR parts 85, 86, and 1036.
* * * * *
    (4) This part applies to aircraft and aircraft engines we regulate 
under 40 CFR parts 1030 and 1031 to the extent and in the manner 
specified in 40 CFR parts 1030 and 1031.
    (5) This part 1068 applies for locomotives that are subject to the 
provisions of 40 CFR part 1033.
    (6) This part 1068 applies for land-based nonroad compression-
ignition engines that are subject to the provisions of 40 CFR part 
1039. This part 1068 applies for engines certified under 40 CFR part 89 
to the extent and in the manner specified in 40 CFR part 1039.
* * * * *
    (8) This part 1068 applies for marine compression-ignition engines 
that are subject to the provisions of 40 CFR part 1042. This part 1068 
applies for marine compression-ignition engines certified under 40 CFR 
part 94 to the extent and in the manner specified in 40 CFR part 1042.
    (9) This part 1068 applies for marine spark-ignition engines that 
are subject to the provisions of 40 CFR part 1045. This part 1068 
applies for marine spark-ignition engines certified under 40 CFR part 
91 to the extent and in the manner specified in 40 CFR part 1045.
* * * * *
    (13) This part applies for small nonroad spark-ignition engines 
that are subject to the provisions of 40 CFR part 1054. This part 1068 
applies for nonroad spark-ignition engines certified under 40 CFR part 
90 to the extent and in the manner specified in 40 CFR part 1054.
* * * * *
    (15) This part 1068 applies to portable fuel containers we regulate 
under 40 CFR part 59 to the extent and in the manner specified in 40 
CFR part 59, subpart F.
* * * * *

0
285. Revise Sec.  1068.10 to read as follows:

Sec.  1068.10  Practices for handling confidential business 
information.

    The provisions of this section apply both to any information you 
send us and to any information we collect from inspections, audits, or 
other site visits.
    (a) When you submit information to us, if you claim any of that 
information as confidential, you may identify what you claim to be 
confidential by marking, circling, bracketing, stamping, or some other 
method; however, we will not consider any claims of confidentiality 
over information we have determined to be not entitled to confidential 
treatment under Sec.  1068.11 or other applicable provisions.
    (b) If you send us information without claiming it is confidential, 
we may make it available to the public without further notice to you, 
as described in 40 CFR 2.301(j).
    (c) For submissions that include information that may be entitled 
to confidential treatment, we may require that you send a ``public'' 
copy of the report that does not include the confidential information. 
We may require that you substantiate your claim to confidential 
treatment for any items not contained in the public version. We will 
release additional information from the complete version of such a 
submission only as allowed under 40 CFR 2.301(j) and as described in 
this subpart and the standard-setting part.
    (d) We will safeguard your confidential business information (CBI) 
as described in 40 CFR 2.301(j). Also, we will treat certain 
information as confidential and will only disclose this information if 
it has been determined to be not entitled to confidential treatment as 
specified in Sec.  1068.11(c). The following general provisions 
describe how we will process requests for making information publicly 
available:
    (1) Certification information. We will treat information submitted 
in an application for certification as confidential until the 
introduction-into-commerce date you identify in your application for 
certification consistent with 40 CFR 2.301(a)(2)(ii)(B). If you do not 
identify an introduction-into-commerce date or if we issue the 
certificate after your specified date, we will treat information 
submitted in an application for certification as described in Sec.  
1068.11 after the date we issue the certificate.
    (2) Preliminary and superseded information. Preliminary and 
superseded versions of information you submit are covered by 
confidentiality determinations in the same manner as

[[Page 4713]]

final documents. However, we will generally not disclose preliminary or 
superseded information unless we receive a request under 5 U.S.C. 552 
that specifically asks for all versions of a document, including 
preliminary and superseded versions. We will consider a document 
preliminary if we have not reviewed it to verify its accuracy or if the 
reporting deadline has not yet passed. We will consider information 
superseded if you submit a new document or a revised application for 
certification to replace the earlier version.
    (3) Authorizing CBI disclosure. The provisions of this section do 
not prevent us from disclosing protected information if you 
specifically authorize it.
    (4) Relationship to the standard-setting part. The standard-setting 
part may identify additional provisions related to confidentiality 
determinations. Note that the standard-setting part identifies 
information requirements that apply for each type of engine/equipment. 
If this section identifies information that is not required for a given 
engine, that does not create a requirement to submit the information.
    (5) Changes in law. The confidentiality determinations in this 
section and in the standard-setting parts may be changed through the 
processes described in 40 CFR 2.301(j)(4).

0
286. Add Sec.  1068.11 to subpart A to read as follows:

Sec.  1068.11  Confidentiality determinations and related procedures.

    This section characterizes various categories of information for 
purposes of making confidentiality determinations, as follows:
    (a) This paragraph (a) applies the definition of ``Emission data'' 
in 40 CFR 2.301(a) for information related to engines/equipment subject 
to this part. ``Emission data'' cannot be treated as confidential 
business information and shall be available to be disclosed to the 
public except as specified in Sec.  1068.10(d)(1). The following 
categories of information qualify as emission data, except as specified 
in paragraph (c) of this section:
    (1) Certification and compliance information, including information 
submitted in an application for a certificate of conformity that is 
used to assess compliance.
    (2) Fleet value information, including information submitted for 
compliance with fleet average emission standards and emissions related 
ABT credit information, including the information used to generate 
credits.
    (3) Source family information. For example, engine family 
information or test group information would identify the regulated 
emission source.
    (4) Test information and results, including emission test results 
and other data from emission testing that are submitted in an 
application for a certificate of conformity, test results from in-use 
testing, production-line testing, and any other testing to demonstrate 
emissions. The information in this category includes all related 
information to characterize test results, document the measurement 
procedure, and modeling inputs and outputs where the compliance 
demonstration is based on computer modeling.
    (5) ABT credit information, including information submitted for 
current and future compliance demonstrations using credits under an ABT 
program.
    (6) Production volume, including information submitted for 
compliance with fleet average emission standards, compliance with 
requirements to test production engines/equipment, or compliance 
through ABT programs.
    (7) Defect and recall information, including all information 
submitted in relation to a defect or recall except the remedial steps 
you identify in Sec.  1068.510(a)(2).
    (8) Selective enforcement audit compliance information.
    (b) The following categories of information are not eligible for 
confidential treatment, except as specified in Sec.  1068.10(d)(1):
    (1) Published information, including information that is made 
available in annual and quarterly filings submitted to the U.S. 
Securities and Exchanges Commission, on company websites, or otherwise 
made publicly available by the information submitter.
    (2) Observable information available to the public after the 
introduction to commerce date.
    (c) The following categories of information are subject to the 
process for confidentiality determinations in 40 CFR part 2 as 
described in 40 CFR 2.301(j)(5):
    (1) Projected sales volume and projected production volume.
    (2) Production start and end dates.
    (3) Detailed description of emission control operation and 
function.
    (4) Design specifications related to aftertreatment devices.
    (5) Description of auxiliary emission control devices (AECDs).
    (6) Plans for meeting regulatory requirements. For example, this 
applies for any projections of emission credits for the coming model 
year or determinations of the number of required repair facilities that 
are based on projected production volumes.
    (7) The following information related to deterioration factors and 
other adjustment factors:
    (i) Procedures to determine deterioration factors and other 
emission adjustment factors.
    (ii) Any information used to justify those procedures.
    (iii) Emission measurements you use to compare procedures or 
demonstrate that the procedures are appropriate.
    (8) Financial information related to the following items:
    (i) ABT credit transactions, including dollar amount, identity of 
parties, and contract information.
    (ii) Meeting bond requirements, including aggregate U.S. asset 
holdings, financial details regarding specific assets, whether the 
manufacturer or importer obtains a bond, and copies of bond policies.
    (9) Serial numbers or other information to identify specific 
engines or equipment selected for testing.
    (10) Procedures that apply based on your request to test engines/
equipment differently than we specify in the regulation. This applies 
for special and alternative test procedures. This also applies, for 
example, if we approve a broader or narrower zone of engine operation 
for not-to-exceed testing.
    (11) Information related to testing vanadium catalysts in 40 CFR 
part 1065, subpart L.
    (12) GPS data identifying the location for in-use emission 
measurements.
    (13) Information related to possible defects that are subject to 
further investigation (not confirmed defects).
    (14) Information submitted in support of a requested exemption.
    (d) If you submit information that is not addressed in paragraphs 
(a) through (c) of this section, you may claim the information as 
confidential. We may require you to provide us with information to 
substantiate your claims. If claimed, we may consider this 
substantiating information to be confidential to the same degree as the 
information for which you are requesting confidential treatment. We 
will make our determination based on your statements to us, the 
supporting information you send us, and any other available 
information. However, we may determine that your information is not 
subject to confidential treatment consistent with 40 CFR part 2 and 5 
U.S.C. 552(b)(4).
    (e) Applications for certification and submitted reports typically 
rely on software or templates to identify specific categories of 
information. If you submit information in a comment field

[[Page 4714]]

designated for users to add general information, we will respond to 
requests for disclosing that information consistent with paragraphs (a) 
through (d) of this section.

0
287. Amend Sec.  1068.30 by adding a definition of ``Critical emission-
related component'' in alphabetical order and revising the definition 
of ``Designated Compliance Officer'' to read as follows:

Sec.  1068.30  Definitions.

* * * * *
    Critical emission-related component means a part or system whose 
primary purpose is to reduce emissions or whose failure would commonly 
increase emissions without significantly degrading engine/equipment 
performance.
* * * * *
    Designated Compliance Officer means one of the following:
    (1) For motor vehicles regulated under 40 CFR part 86, subpart S: 
Director, Light-Duty Vehicle Center, U.S. Environmental Protection 
Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 
[email protected]; www.epa.gov/ve-certification.
    (2) For compression-ignition engines used in heavy-duty highway 
vehicles regulated under 40 CFR part 86, subpart A, and 40 CFR parts 
1036 and 1037, and for nonroad and stationary compression-ignition 
engines or equipment regulated under 40 CFR parts 60, 1033, 1039, and 
1042: Director, Diesel Engine Compliance Center, U.S. Environmental 
Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 
[email protected]; www.epa.gov/ve-certification.
    (3) Director, Gasoline Engine Compliance Center, U.S. Environmental 
Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 
[email protected]; www.epa.gov/ve-certification, for all the 
following engines and vehicles:
    (i) For spark-ignition engines used in heavy-duty highway vehicles 
regulated under 40 CFR part 86, subpart A, and 40 CFR parts 1036 and 
1037,
    (ii) For highway motorcycles regulated under 40 CFR part 86, 
subpart E.
    (iii) For nonroad and stationary spark-ignition engines or 
equipment regulated under 40 CFR parts 60, 1045, 1048, 1051, 1054, and 
1060.

0
288. Add Sec.  1068.50 to subpart A to read as follows:

Sec.  1068.50  Adjustable parameters.

    (a) The standard-setting part requires as a condition of 
certification that engines with adjustable parameters meet all the 
requirements of the standard-setting part for any setting in the 
practically adjustable range. This section defines these terms and 
describes general provisions that apply broadly across sectors. This 
section refers to engines, because most adjustable parameters are 
integral to the engine even in the case of equipment-based standards; 
this section also applies for equipment-based adjustable parameters. 
The provisions of this section apply starting with model year 2027 and 
are optional for earlier model years.
    (b) You must use good engineering judgment for all decisions 
related to adjustable parameters. We recommend that you ask for 
preliminary approval for decisions related to new technologies, 
substantially changed engine designs, or new methods for limiting 
adjustability. The standard-setting part describes the information you 
must include in the application for certification related to adjustable 
parameters. Decisions related to adjustable parameters include the 
following:
    (1) Determining which engine operating parameters qualify as 
adjustable parameters.
    (2) Establishing the adequacy of the limits, stops, seals, 
programming limits, inducements, or other means used to limit 
adjustment, limit reprogramming, or ensure replenishment.
    (3) Defining the practically adjustable range for each such 
parameter.
    (c) For purposes of this section, ``operating parameter'' means any 
feature that can, by the nature of its design, be adjusted to affect 
engine performance. For example, while bolts used to assemble the 
engine are practically adjustable (can be loosened or tightened), they 
are not adjustable parameters because they are not operating 
parameters. Consider all programmable parameters not involving user-
selectable controls to be a single, collective operating parameter.
    (d) Operating parameters are considered adjustable parameters if 
they are practically adjustable by a user or other person by physical 
adjustment, programmable adjustment, or regular replenishment of a 
fluid or other consumable material. However, an operating parameter is 
not an adjustable parameter if--
    (1) We determine it is permanently sealed or it is not practically 
adjustable using available tools, as described in paragraph (e) of this 
section; or
    (2) We determine that engine operation over the full range of 
adjustment does not affect emissions without also degrading engine 
performance to the extent that operators will be aware of the problem.
    (e) An operating parameter is considered practically adjustable as 
follows:
    (1) Physically adjustable parameters are considered practically 
adjustable if the adjustment is accessible and can be performed by an 
experienced mechanic using appropriate tools within the following time 
and cost thresholds, excluding extraordinary measures:
    (i) For engines at or below 30 kW, physically adjustable parameters 
are considered practically adjustable if a typical user can make 
adjustments with ordinary tools within 15 minutes using service parts 
that cost no more than $30.
    (ii) For 30-560 kW engines, physically adjustable parameters are 
considered practically adjustable if a qualified mechanic can make 
adjustments with ordinary tools within 60 minutes using service parts 
that cost no more than $60.
    (iii) For engines above 560 kW, physically adjustable parameters 
are considered practically adjustable if a qualified mechanic can make 
adjustments with any available supplies and tools within 60 minutes.
    (iv) Cost thresholds in this section are expressed in 2020 dollars. 
Adjust these values for certification by comparing most recently 
available Consumer Price Index for All Urban Consumers (CPI-U) value 
published by the Bureau of Labor Statistics at www.bls.gov/data/inflation_calculator.htm.
    (v) Cost thresholds do not include the cost of labor or the cost of 
any necessary tools or nonconsumable supplies. Time thresholds refer to 
the time required to access and adjust the parameter, excluding any 
time necessary to purchase parts, tools, or supplies, or to perform 
testing.
    (vi) The term ``ordinary tools'' has the following meanings for 
different sizes of engines:
    (A) Ordinary tools consist of slotted and Phillips head 
screwdrivers, pliers, hammers, awls, wrenches, electric screwdrivers, 
electric drills, and any tools supplied by the manufacturer, where 
those tools are used for their intended purpose.
    (B) For 30-560 kW engines, ordinary tools includes the tools 
identified in paragraph (e)(1)(vi)(A) of this section and any other 
hand tools, solvents, or other supplies sold at hardware stores, 
automotive parts supply stores or on the internet.
    (vii) The following extraordinary measures are not included when 
determining whether a physically adjustable parameter is considered

[[Page 4715]]

``practically adjustable'' according to the specified time and cost 
thresholds:
    (A) Removing the cylinder head(s) from the engine block.
    (B) Fully or partially removing a carburetor.
    (C) Drilling or grinding through caps or plugs.
    (D) Causing damage to engine or equipment if the associated repair 
would exceed the time or cost thresholds in this paragraph (e)(1).
    (E) Making special tools to override design features that prevent 
adjustment. Note that extraordinary measures do not include purchase of 
such special tools if they become available as described in paragraph 
(e)(1)(vi)(B) of this section.
    (2) A programmable operating parameter is considered ``practically 
adjustable'' if an experienced mechanic can adjust the parameter using 
any available tools (including devices that are used to alter computer 
code). Conversely, such parameters are not practically adjustable if 
you limit access to electronic control modules with password or 
encryption protection. You must have adequate protections in place to 
prevent distribution and use of passwords or encryption keys. This 
paragraph (e)(2) applies for engines with any degree of programmable 
control. Programmable settings are considered practically adjustable if 
any of the following apply:
    (i) The user can make the adjustment by following instructions in 
the owners manual.
    (ii) An experienced mechanic can make the adjustment using ordinary 
digital interface tools for selecting available settings or options as 
described in this paragraph (e)(2).
    (f) The practically adjustable range for physically adjustable 
operating parameters is based on design features to create physical 
limits or stops to limit adjustment. A physical limit or stop is 
adequate for defining the limits of the practically adjustable range if 
it has the following characteristics:
    (1) In the case of a threaded adjustment, the head is sheared off 
after adjustment at the factory or the threads are terminated, pinned, 
or crimped to prevent additional travel without causing damage for 
which the repair would exceed the time or cost thresholds in paragraph 
(e)(1) of this section.
    (2) In the case of fasteners, bimetal springs, or other mechanical 
devices used to limit adjustment, those devices are recessed within a 
larger, permanent body and sealed with a plug, cap, or cover plate that 
limits access to the device consistent with the time and cost 
thresholds in paragraph (e)(1) of this section.
    (3) Operators cannot exceed the travel or rotation limits using 
appropriate tools without causing damage for which the repairs would 
exceed the time or cost thresholds specified in paragraph (e)(1) of 
this section. For example, if a vehicle has a shim, bushing, or other 
device to limit flow rates, range of travel, or other parameters to 
prevent operating outside of a specified range of engine or vehicle 
speeds, you must take steps to prevent operators or mechanics from 
removing, replacing, or altering those parts to operate at a wider 
range of engine or vehicle speeds.
    (g) Apply the following provisions to determine the practically 
adjustable range for programmable parameters that can be adjusted by 
changing software or operating parameters (``reflashed''):
    (1) If an engine includes multiple operating modes or other 
algorithms that can be selected or are easily accessible, consider each 
of the selectable or accessible modes or settings to be within the 
practically adjustable range.
    (2) If you sell or offer to sell software or other tools that an 
experienced mechanic not affiliated with the manufacturer could use to 
reflash or otherwise modify the electronic control module, consider all 
those settings to be within the practically adjustable range.
    (3) The following systems and features illustrate examples of the 
types of programmable settings for which this paragraph (g) applies:
    (i) Air-fuel setpoints for closed-loop fuel systems.
    (ii) Reductant flow systems.
    (iii) Base maps for fuel injection or spark timing.
    (iv) Exhaust gas recirculation maps.
    (h) The following provisions apply for adjustable parameters 
related to elements of design involving consumption and replenishment, 
such as DEF tank fill level and hybrid battery state of charge:
    (1) We will determine the range of adjustability based on the 
likelihood of in-use operation at a given point in the physically 
adjustable range. We may determine that operation in certain subranges 
within the physically adjustable range is sufficiently unlikely that 
the subranges should be excluded from the allowable adjustable range 
for testing. In such cases, the engines/equipment are not required to 
meet the emission standards for operation in an excluded subrange.
    (2) Shipping new engines/equipment in a state or configuration 
requiring replenishment to be within the range of adjustability for a 
certified configuration does not cause a violation of the prohibition 
in Sec.  1068.101(a)(1).
    (i) We will make determinations regarding in-use adjustments of 
adjustable parameters under this section for certifying engines as 
follows:
    (1) Our determinations will depend on in-use maintenance practices 
conforming to the maintenance and service information you provide. For 
example, if your published maintenance instructions describe routine 
procedures for adjusting engines or if you or your dealers make 
specialized tools available to operators, we will conclude that such 
adjustments are likely to occur. Also, your maintenance and service 
information may not specify adjustable ranges that are broader than 
those that you specify in your application for certification.
    (2) We may review manufacturer statements under this section for 
certifying engines for a later model year if we learn from observation 
of in-use engines or other information that a parameter was in fact 
practically adjustable or that the specified operating range was in 
fact not correct. We may require you to include a new adjustable 
parameter or to revise your specified operating range for an adjustable 
parameter.
    (j) We may inspect your engines at any time to determine whether 
they meet the specifications of this section. We may purchase engines 
for testing, or we may ask you to supply engines for such inspections. 
We will inspect using appropriate tools and time limits and using any 
available devices that alter computer code, as specified in paragraph 
(e)(2) of this section. The inspection will determine the following:
    (1) If the adjustable parameter is limited to the adjustable range 
specified in the manufacturer's certification application.
    (2) If physical stops for physically adjustable parameters can be 
bypassed using methods outlined in paragraph (f) of this section.
    (k) Except as provided in the standard-setting part and this 
paragraph (k), engines are not in the certified configuration if you 
produce them with adjustable parameters set outside the range specified 
in your application for certification. Similarly, engines are not in 
the certified configuration if you produce them with other operating 
parameters that do not conform to the certified configuration. Where we 
determine that you failed to identify something that should be 
considered an adjustable parameter, we may require you to treat the 
parameter as defective under Sec.  1068.501. If we determine you 
deliberately misrepresented the

[[Page 4716]]

accessibility of the parameter or that you did not act in good faith, 
we may take action regarding your certificate as described in the 
standard-setting part (see, for example, 40 CFR 1054.255).
    (l) Nothing in this section limits the tampering prohibition of 
Sec.  1068.101(b)(1) or the defeat device prohibition of Sec.  
1068.101(b)(2).

0
289. Amend Sec.  1068.101 by revising paragraphs (a) introductory text 
and (b)(5) to read as follows:

Sec.  1068.101  What general actions does this regulation prohibit?

* * * * *
    (a) The following prohibitions and requirements apply to 
manufacturers of new engines, manufacturers of equipment containing 
these engines, manufacturers of new equipment, and other persons as 
provided by Sec.  1068.1(a), except as described in subparts C and D of 
this part:
* * * * *
    (b) * * *
    (5) Importation. You may not import an uncertified engine or piece 
of equipment if it is defined to be new in the standard-setting part 
with a model year for which emission standards applied. Anyone 
violating this paragraph (b)(5) is deemed to be a manufacturer in 
violation of paragraph (a)(1) of this section. We may assess a civil 
penalty up to $44,539 for each engine or piece of equipment in 
violation. Note the following:
* * * * *

0
290. Amend Sec.  1068.210 by revising paragraph (c) introductory text 
to read as follows:

Sec.  1068.210  Exempting test engines/equipment.

* * * * *
    (c) If you are a certificate holder, you may request an exemption 
for engines/equipment you intend to include in a test program.
* * * * *

0
291. Amend Sec.  1068.220 by revising paragraph (b) to read as follows:

Sec.  1068.220  Exempting display engines/equipment.

* * * * *
    (b) Nonconforming display engines/equipment will be exempted if 
they are used for displays in the interest of a business or the general 
public. The exemption in this section does not apply to engines/
equipment displayed for any purpose we determine is inappropriate for a 
display exemption.
* * * * *

0
292. Amend Sec.  1068.240 by revising paragraphs (a)(1), (b)(3), and 
(c)(3)(ii) to read as follows:

Sec.  1068.240  Exempting new replacement engines.

* * * * *
    (a) * * *
    (1) Paragraphs (b) and (c) of this section describe different 
approaches for exempting new replacement engines where the engines are 
specially built to correspond to an engine model from an earlier model 
year that was subject to less stringent standards than those that apply 
for current production (or is no longer covered by a certificate of 
conformity). You must comply with the requirements of paragraph (b) of 
this section for any number of replacement engines you produce in 
excess of what we allow under paragraph (c) of this section. You must 
designate engines you produce under this section as tracked engines 
under paragraph (b) of this section or untracked engines under 
paragraph (c) of this section by the deadline for the report specified 
in paragraph (c)(3) of this section.
* * * * *
    (b) * * *
    (3) An old engine block replaced by a new engine exempted under 
this paragraph (b) may be reintroduced into U.S. commerce as part of an 
engine that meets either the current standards for new engines, the 
provisions for new replacement engines in this section, or another 
valid exemption. Otherwise, you must destroy the old engine block (or 
confirm that it has been destroyed), or export the engine block without 
its emission label. Note that this paragraph (b)(3) does not require 
engine manufacturers to take possession of the engine being replaced. 
Owners may arrange to keep the old engine if they demonstrate that the 
engine block has been destroyed. An engine block is destroyed under 
this paragraph (b)(3) if it can never be restored to a running 
configuration.
* * * * *
    (c) * * *
    (3) * * *
    (ii) Count exempt engines as tracked under paragraph (b) of this 
section only if you meet all the requirements and conditions that apply 
under paragraph (b)(2) of this section by the due date for the annual 
report. In the annual report you must identify any replaced engines 
from the previous year whose final disposition is not resolved by the 
due date for the annual report. Continue to report those engines in 
later reports until the final disposition is resolved. If the final 
disposition of any replaced engine is not resolved for the fifth annual 
report following the production report, treat this as an untracked 
replacement in the fifth annual report for the preceding year.
* * * * *

0
293. Amend Sec.  1068.261 by revising paragraphs (b), (c) introductory 
text, and (d) introductory text to read as follows:

Sec.  1068.261  Delegated assembly and other provisions related to 
engines not yet in the certified configuration.

* * * * *
    (b) If you manufacture engines and install them in equipment you or 
an affiliated company also produce, you must take steps to ensure that 
your facilities, procedures, and production records are set up to 
ensure that equipment and engines are assembled in their proper 
certified configurations. For example, you may demonstrate compliance 
with the requirements of this section by maintaining a database showing 
how you pair aftertreatment components with the appropriate engines 
such that the final product is in its certified configuration.
    (c) If you manufacture engines and ship them to an unaffiliated 
company for installation in equipment and you include the price of all 
aftertreatment components in the price of the engine (whether or not 
you ship the aftertreatment components directly to the equipment 
manufacturer), all the following conditions apply:
* * * * *
    (d) If you manufacture engines and ship them to an unaffiliated 
company for installation in equipment, but you do not include the price 
of all aftertreatment components in the price of the engine, you must 
meet all the conditions described in paragraphs (c)(1) through (9) of 
this section, with the following additional provisions:
* * * * *

0
294. Amend Sec.  1068.301 by revising paragraph (b) to read as follows:

Sec.  1068.301  General provisions for importing engines/equipment.

* * * * *
    (b) In general, engines/equipment that you import must be covered 
by a certificate of conformity unless they were built before emission 
standards started to apply. This subpart describes the limited cases 
where we allow importation of exempt or excluded engines/equipment. If 
an engine has an exemption from exhaust emission standards, you may 
import the equipment under the same exemption. Imported engines/
equipment that are exempt or excluded must have a label as described in 
the specific exemption

[[Page 4717]]

or exclusion. If the regulation does not include specific labeling 
requirements, apply a label meeting the requirements of Sec.  1068.45 
that identifies your corporate name and describes the basis for the 
exemption or exclusion.
* * * * *

0
295. Amend Sec.  1068.310 by revising the introductory text and 
paragraph (e)(4) to read as follows:

Sec.  1068.310  Exclusions for imported engines/equipment.

    If you show us that your engines/equipment qualify under one of the 
paragraphs of this section, we will approve your request to import such 
excluded engines/equipment. You must have our approval before importing 
engines/equipment under paragraph (a) of this section. You may, but are 
not required, to request our approval to import the engines/equipment 
under paragraph (b) through (d) of this section. Qualifying engines/
equipment are excluded as follows:
* * * * *
    (e) * * *
    (4) State: ``THIS ENGINE IS EXEMPT FROM THE REQUIREMENTS OF 
[identify the part referenced in Sec.  1068.1(a) that would otherwise 
apply], AS PROVIDED IN [identify the paragraph authorizing the 
exemption (for example, ``40 CFR 1068.310(a)'')]. INSTALLING THIS 
ENGINE IN ANY DIFFERENT APPLICATION MAY BE A VIOLATION OF FEDERAL LAW 
SUBJECT TO CIVIL PENALTY.''

0
296. Amend Sec.  1068.315 by revising paragraphs (a) and (h) and 
removing paragraph (i) to read as follows:

Sec.  1068.315  Permanent exemptions for imported engines/equipment.

* * * * *
    (a) National security exemption. You may import an engine or piece 
of equipment under the national security exemption in Sec.  1068.225.
* * * * *
    (h) Identical configuration exemption. Unless specified otherwise 
in the standard-setting part, you may import nonconforming engines/
equipment if they are identical in all material respects to certified 
engines/equipment produced by the same manufacturer, subject to the 
following provisions:
    (1) You must meet all the following criteria:
    (i) You have owned the engines/equipment for at least six months.
    (ii) You agree not to sell, lease, donate, trade, or otherwise 
transfer ownership of the engines/equipment for at least five years. 
The only acceptable way to dispose of the engines/equipment during this 
five-year period is to destroy or export them.
    (iii) You use data or evidence sufficient to show that the engines/
equipment are in a configuration that is identical in all material 
respects to engines/equipment the original manufacturer has certified 
to meet emission standards that apply at the time the manufacturer 
finished assembling or modifying the engines/equipment in question. If 
you modify the engines/equipment to make them identical, you must 
completely follow the original manufacturer's written instructions.
    (2) We will tell you in writing if we find the information 
insufficient to show that the engines/equipment are eligible for the 
identical configuration exemption. We will then not consider your 
request further until you address our concerns.

0
297. Amend Sec.  1068.325 by revising the introductory text, paragraphs 
(a) through (c), (e), and (g) to read as follows:

Sec.  1068.325  Temporary exemptions for imported engines/equipment.

    You may import engines/equipment under certain temporary 
exemptions, subject to the conditions in this section. We may ask U.S. 
Customs and Border Protection to require a specific bond amount to make 
sure you comply with the requirements of this subpart. You may not sell 
or lease one of these exempted engines/equipment while it is in the 
United States except as specified in this section or Sec.  1068.201(i). 
You must eventually export the engine/equipment as we describe in this 
section unless it conforms to a certificate of conformity or it 
qualifies for one of the permanent exemptions in Sec.  1068.315 or the 
standard-setting part.
    (a) Exemption for repairs or alterations. You may temporarily 
import nonconforming engines/equipment solely for repair or alteration, 
subject to our advance approval as described in paragraph (j) of this 
section. You may operate the engine/equipment in the United States only 
as necessary to repair it, alter it, or ship it to or from the service 
location. Export the engine/equipment directly after servicing is 
complete, or confirm that it has been destroyed.
    (b) Testing exemption. You may temporarily import nonconforming 
engines/equipment for testing if you follow the requirements of Sec.  
1068.210, subject to our advance approval as described in paragraph (j) 
of this section. You may operate the engines/equipment in the United 
States only as needed to perform tests. The testing exemption expires 
one year after you import the engine/equipment unless we approve an 
extension. The engine/equipment must be exported before the exemption 
expires. You may sell or lease the engines/equipment consistent with 
the provisions of Sec.  1068.210.
    (c) Display exemption. You may temporarily import nonconforming 
engines/equipment for display if you follow the requirements of Sec.  
1068.220, subject to our advance approval as described in paragraph (j) 
of this section. The display exemption expires one year after you 
import the engine/equipment, unless we approve your request for an 
extension. The engine/equipment must be exported (or destroyed) by the 
time the exemption expires or directly after the display concludes, 
whichever comes first.
* * * * *
    (e) Diplomatic or military exemption. You may temporarily import 
nonconforming engines/equipment if you represent a foreign government 
in a diplomatic or military capacity. U.S Customs and Border Protection 
may require that you show your written confirmation from the U.S. State 
Department that you qualify for the diplomatic or military exemption or 
a copy of your orders for military duty in the United States. We will 
rely on the State Department or your military orders to determine when 
your diplomatic or military status expires, at which time you must 
export your exempt engines/equipment.
* * * * *
    (g) Exemption for partially complete engines. The following 
provisions apply for importing partially complete engines and used 
engines that become new as a result of importation:
    (1) You may import a partially complete engine by shipping it from 
one of your facilities to another under the provisions of Sec.  
1068.260(c) if you also apply a removable label meeting the 
requirements of Sec.  1068.45 that identifies your corporate name and 
states that the engine is exempt under the provisions of Sec.  
1068.325(g).
    (2) You may import an engine if another company already has a 
certificate of conformity and will be modifying the engine to be in its 
final certified configuration or a final exempt configuration if you 
meet the labeling and other requirements of Sec.  1068.262. If you are 
importing a used engine that becomes new as a result of importation, 
you must meet all the requirements that apply to original engine 
manufacturers under Sec.  1068.262. You may sell or lease

[[Page 4718]]

the engines consistent with the provisions of Sec.  1068.262.
* * * * *

0
298. Amend Sec.  1068.450 by revising paragraph (e) to read as follows:

Sec.  1068.450  What records must I send to EPA?

* * * * *
    (e) We may post test results on publicly accessible databases and 
we will send copies of your reports to anyone from the public who asks 
for them, consistent with Sec.  1068.11.

0
299. Amend Sec.  1068.601 by revising the introductory text and 
paragraph (b) to read as follows:

Sec.  1068.601  Overview.

    The regulations of this chapter involve numerous provisions that 
may result in EPA making a decision or judgment that you may consider 
adverse to your interests. For example, our decisions might require you 
to pay penalties, or you might consider that our decisions will limit 
your business activities or put you at a competitive disadvantage. As 
specified in the regulations in this chapter, this might involve an 
opportunity for an informal hearing or a formal hearing that follows 
specific procedures and is directed by a Presiding Officer. The 
regulations in this chapter generally specify when we would hold a 
hearing. In limited circumstances, we may grant a request for a hearing 
related to adverse decisions regarding regulatory provisions for which 
we do not specifically describe the possibility of asking for a 
hearing.
* * * * *
    (b) For other issues where the regulation allows for a hearing in 
response to an adverse decision, you may request an informal hearing as 
described in Sec.  1068.650. Sections 1068.610 through 1068.630 
describe when and how to request an informal hearing under various 
circumstances.
* * * * *

0
300. Add Sec.  1068.630 to read as follows:

Sec.  1068.630  Request for hearing--allowable maintenance.

    (a) Any manufacturer may request an informal hearing as described 
in Sec.  1068.650 in response to our decision to identify allowable 
maintenance associated with new technology as part of the certification 
process.
    (b) You must send your hearing request in writing to the Designated 
Compliance Officer no later than 30 days after we publish our decision 
in the Federal Register. If the deadline passes, we may nevertheless 
grant you a hearing at our discretion.
    (c) Your hearing request must include the information specified in 
Sec.  1068.610(d).
    (d) We will approve your request for an informal hearing if we find 
that your request raises a substantial factual issue in the decision we 
made that, if addressed differently, could alter the outcome of that 
decision.

0
301. Redesignate appendix I to part 1068 as appendix A to part 1068 and 
amend newly redesignated appendix A by revising the introductory text 
and paragraph IV to read as follows:

Appendix A to Part 1068--Emission-Related Components

    This appendix specifies emission-related components that we 
refer to for describing such things as emission-related warranty or 
maintenance or requirements related to rebuilding engines. Note that 
inclusion of a component in Section III of this Appendix does not 
make it an emission-related component for engines/equipment that are 
not subject to evaporative emission standards.
* * * * *
    IV. Any other part or system that meets the definition of critical 
emission-related component.

Appendix II to Part 1068 [Redesignated as Appendix B to Part 1068]

0
302. Redesignate appendix II to part 1068 as appendix B to part 1068.

Appendix III to Part 1068 [Redesignated as Appendix C to Part 1068]

0
303. Redesignate appendix III to part 1068 as appendix C to part 1068.

PART 1090--REGULATION OF FUELS, FUEL ADDITIVES, AND REGULATED 
BLENDSTOCKS

0
304. The authority citation for part 1090 continues to read as follows:

    Authority: 42 U.S.C. 7414, 7521, 7522-7525, 7541, 7542, 7543, 
7545, 7547, 7550, and 7601.

Subpart P [Amended]

0
305. Revise Sec.  1090.1550 to read as follows:

Sec.  1090.1550  Requirements for gasoline dispensing nozzles used with 
motor vehicles.

    The following requirements apply for any nozzle installation used 
for dispensing gasoline into motor vehicles:
    (a) Nozzles must meet the following hardware specifications:
    (1) The outside diameter of the terminal end must not be greater 
than 21.3 mm.
    (2) The terminal end must have a straight section of at least 63 
mm.
    (3) The retaining spring must terminate at least 76 mm from the 
terminal end.
    (b) The dispensing flow rate must not exceed a maximum value of 10 
gallons per minute. The flow rate may be controlled through any means 
in the pump/dispenser system, as long as it does not exceed the 
specified maximum value.

[FR Doc. 2022-27957 Filed 1-11-23; 4:15 pm]
 BILLING CODE 6560-50-P