Document ID: EPA_FRDOC_0001-28943
Agency: epa
Document Type: Notice
Title: Official Release of EMFAC2021 Motor Vehicle Emission Factor Model for Use in the State of California
Posted Date: 2022-11-15T05:00Z

[Federal Register Volume 87, Number 219 (Tuesday, November 15, 2022)]
[Notices]
[Pages 68483-68489]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2022-24790]

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ENVIRONMENTAL PROTECTION AGENCY

[FRL-10366-01-R9]

Official Release of EMFAC2021 Motor Vehicle Emission Factor Model 
for Use in the State of California

AGENCY: Environmental Protection Agency (EPA).

ACTION: Notice of availability.

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SUMMARY: The Environmental Protection Agency (EPA) is approving and 
announcing the availability of the latest version of the California 
EMFAC (short for EMission FACtor) model for use in state implementation 
plan (SIP) development and transportation conformity in California. 
EMFAC2021 is the latest update to the EMFAC model for use by California 
state and local governments to meet Clean Air Act (CAA) requirements. 
The new model, which is based on new and improved data and new and 
amended regulations in California, calculates air pollution emissions 
factors for passenger cars, trucks, motorcycles, motor homes, and 
buses. The EPA is also approving EMFAC2017 adjustment factors, which 
are based on these same new regulations, for those areas that have 
already begun SIP development with EMFAC2017. This notice also sets the 
date after which EMFAC2021, rather than EMFAC2017 or the EMFAC2017 
adjustment factors discussed in this notice, must be used to satisfy 
the requirement that conformity determinations be based on the latest 
emissions model available. Because the EMFAC model is used only in 
California, this notice does not affect the applicability of the Motor 
Vehicle Emissions Simulator (MOVES) model for users in other states.

DATES: The EPA's approval of the EMFAC2021 emissions model and 
EMFAC2017 adjustment factors for SIP, conformity purposes, and 
applicable CAA purposes as described in this notice is effective 
November 15, 2022. EMFAC2021 must be used as described in this notice 
for all new regional emissions analyses for transportation conformity 
purposes that are started on or after November 15, 2024 and for all new 
carbon monoxide (CO) and particulate matter (PM10 and 
PM2.5) hot-spot analyses that are started on or after 
November 15, 2023.

FOR FURTHER INFORMATION CONTACT: Karina O'Connor, 
[email protected], (775) 434-8176, Air Planning Office (AIR-2), 
Air and Radiation Division, EPA Region IX, 75 Hawthorne Street, San 
Francisco, California 94105-3901.

SUPPLEMENTARY INFORMATION: Copies of the official version of the 
EMFAC2021 model and the EMFAC2017 adjustment factors, including 
technical support documents, are available on the California Air 
Resources Board (CARB) website: https://ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory/msei-modeling-tools-emfac-software-and.
    Throughout this document, ``we,'' ``us,'' and ``our'' refer to the 
EPA. This document is organized as follows:

I. Background
    A. What is the EMFAC model?
    B. For what purposes is EMFAC used?
    C. What versions of EMFAC are currently in use in California?
    D. What has CARB submitted to the EPA for approval?
    E. How is EMFAC2021 different from the previous versions of 
EMFAC?
    F. What is included in the EMFAC2017 adjustment factors?
    G. How were stakeholders and the public involved in the EMFAC 
development process?
    H. Future Updates to EMFAC
II. The EPA's Action
    A. What actions are the EPA taking in this notice?
    B. Can EMFAC2021 and EMFAC2017 adjustment factors be used for 
SIP development?
    C. What transportation conformity analyses can EMFAC2021 and 
EMFAC2017 adjustment factors be used for?
    D. Does this notice establish a transportation conformity grace 
period for the use of this model?

[[Page 68484]]

    E. Can areas use EMFAC2017 during the grace period?
III. Summary of the EPA's Actions

I. Background

A. What is the EMFAC model?

    The EMFAC model (``EMFAC'') is a computer model that can estimate 
emissions rates of air pollutants for on-road mobile sources (``motor 
vehicles''), for a range of past and future calendar years, that are 
operating in California. Within the EMFAC model, emissions are 
calculated for a variety of different vehicle classes composed of 
passenger cars, various types of trucks and buses, motorcycles, and 
motor homes.
    EMFAC is used to calculate current and future inventories of motor 
vehicle emissions at the state, air district, air basin, county, and 
project level. EMFAC contains default vehicle activity data, and the 
option of modifying that data, so it can be used to estimate a motor 
vehicle emissions inventory in tons per day for a specific year, month, 
or season, and as a function of ambient temperature, relative humidity, 
vehicle population, mileage accrual, miles of travel, and speed. Thus, 
the model can be used to make decisions about air pollution policies 
and programs at the local or state level.
    The EMFAC model is based on Python and MySQL software. This 
structure was developed to allow CARB to incorporate new and updated 
regulations and emissions data into the model and provide for a 
simplified user experience. The model is operated in either the 
Emissions Mode (total on-road emissions) or the Emissions Rate Mode 
(emission factors) for regional emissions analyses to access emissions 
databases and vehicle activity data for the appropriate geographic 
subarea. EMFAC also includes the Project-Level Assessment (EMFAC2021-
PL) feature, which is available when EMFAC is run in Emissions Rate 
Mode. When using EMFAC2021-PL, emissions rates are estimated based on 
user-specified, project-specific conditions. An updated handbook for 
using EMFAC at the project level is available from CARB.\1\ EMFAC 
allows users to run one model for SIP inventories, regional emissions 
analyses, and project analyses.
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    \1\ https://ww2.arb.ca.gov/sites/default/files/2021-06/emfac2021_volume_2_pl_handbook_ada.pdf.
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B. For what purposes is EMFAC used?

    The EMFAC model is used in California for modeling emissions of on-
road vehicles. Emissions inventories based on EMFAC are used to meet 
SIP, conformity, and other applicable requirements under the CAA. EMFAC 
is also used for National Environmental Protection Act and California 
Environmental Quality Act analyses in California where the project 
undergoing such analysis includes motor vehicle emissions. In addition, 
EMFAC can be used to model carbon dioxide emissions and energy 
consumption from on-road mobile sources in California, although that 
modeling is not used for transportation conformity and SIP purposes 
under the CAA.
    In this notice, the EPA is addressing the use of EMFAC for CAA 
purposes, mainly SIP development and transportation conformity. The 
latest version of EMFAC should be used in ozone, carbon monoxide (CO), 
particulate matter (PM2.5 and PM10), and nitrogen 
dioxide (NO2) SIP development as expeditiously as possible, 
as there is no grace period for the use of the latest emissions model 
in SIP submissions. The CAA requires that inventories and control 
measures approved into the SIP be based on the most current information 
and applicable models that are available when a SIP revision is 
developed.\2\ Further discussion of the use of EMFAC in SIP revisions 
is found in section II.B of this notice.
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    \2\ CAA section 172(c)(3). Also see the discussion of emissions 
inventory requirements in the ``Fine Particulate Matter National 
Ambient Air Quality Standards: State Implementation Plan 
Requirements'' rule (81 FR 58029, August 24, 2016) and in the 
``Implementation of the 2015 National Ambient Air Quality Standards 
for Ozone: Nonattainment Area State Implementation Plan 
Requirements'' rule (83 FR 63022, December 6, 2018).
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    CAA section 176(c)(1) and 40 CFR 93.111(a) require that the latest 
emissions estimates be used in transportation conformity analyses. The 
EPA approves models that fulfill these requirements. Under 40 CFR 
93.111(a), the EPA must approve new versions of EMFAC for use in the 
preparation or revision of SIPs before they can be used in 
transportation conformity analyses.
    EMFAC is used statewide in all regional emissions analyses and CO, 
PM10, and PM2.5 hot-spot analyses for 
transportation conformity determinations in California. Transportation 
conformity is required under CAA section 176(c) to ensure that 
federally supported transportation plans, transportation improvement 
programs (TIPs), and highway and transit projects are consistent with 
(``conform to'') the purpose of the SIP. Conformity to a SIP means that 
a transportation activity will not cause or contribute to new air 
quality violations, worsen existing violations, or delay timely 
attainment of the national ambient air quality standards (NAAQS) or 
interim milestones. The EPA's transportation conformity regulations 
describe how federally funded and approved highway and transit projects 
meet these statutory requirements.\3\
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    \3\ 40 CFR 51.390 and 40 CFR part 93.
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C. What versions of EMFAC are currently in use in California?

    Most SIP revisions developed in California since 2015 were 
developed using EMFAC2017 (released by CARB in December 2017) or 
EMFAC2014 (released by CARB in December 2014). The EPA approved and 
announced the availability of EMFAC2017 on August 15, 2019,\4\ and 
approved and announced the availability of EMFAC2014 on December 14, 
2015,\5\ for all nonattainment and maintenance areas in California.
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    \4\ 84 FR 41717.
    \5\ 80 FR 77337.
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    EMFAC2017 was considered a major update to EMFAC2014, and most SIP 
revisions in California are being updated with EMFAC2017 in the 2021-
2022 timeframe. Also, California is in the process of developing SIP 
revisions for the 2015 ozone NAAQS using EMFAC2017 with the adjustment 
factors discussed in section I.F and elsewhere in this notice.

D. What has CARB submitted to the EPA for approval?

    In letters dated August 30, 2021 and August 31, 2021, CARB 
initially requested that the EPA approve EMFAC2021 and EMFAC2017 
adjustment factors, respectively, for use in developing SIP revisions 
and in determining conformity in California.\6\ As described in section 
E of this notice, EMFAC2021 is a significant change from previous EMFAC 
models and can calculate motor vehicle emissions for all areas in 
California.
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    \6\ The EMFAC2021 model and supporting information is available 
for downloading at https://ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory/msei-modeling-tools-emfac-software-and. 
Technical documentation explaining the changes to the model and the 
technical foundation for the model is available at https://ww2.arb.ca.gov/sites/default/files/2021-08/emfac2021_technical_documentation_april2021.pdf.
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    On October 14, 2022, CARB sent the EPA a subsequent letter 
(``October 14, 2022 letter'') that noted CARB had found and fixed a 
computational error related to NOX idling emissions from 
heavy-duty trucks. CARB noted this error has been fixed in EMFAC2021 
version 1.0.2 and requested the EPA approve this latest version. CARB's 
October 14, 2022 letter also requested that the EPA approve both the 
desktop and web platform for version 1.02 of the of EMFAC2021 model. To 
create the

[[Page 68485]]

web platform, CARB runs the model for all areas and uploads the results 
to a database on the web that allows users to retrieve the needed 
information based on what they are modeling. The web platform database 
is based on the corrected version of EMFAC2021.
    Finally, CARB submitted revised EMFAC2017 adjustment factors in the 
October 14, 2022 letter and noted that these adjustment factors have 
also been revised to correct the NOX computational error and 
include factors by vehicle category in addition to by calendar year. In 
the October 14, 2022 letter, CARB requested that the EPA approve the 
EMFAC2017 adjustment factors for both SIP and conformity purposes.
    CARB's August 30, 2021, August 31, 2021, and October 14, 2022 
letters to the EPA are available on our website.\7\
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    \7\ https://www.epa.gov/state-and-local-transportation/policy-and-technical-guidance-state-and-local-transportation#emission.
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E. How is EMFAC2021 different from the previous versions of EMFAC?

    The EMFAC2021 model interface and overall design has not changed 
significantly as compared to EMFAC2017. However, EMFAC2021 emissions 
estimates have changed significantly because the model includes new 
data, new features, significant changes to the methodologies regarding 
calculation of motor vehicle emissions, the effect of new emission 
regulations, and revisions to implementation data for control measures. 
For example, EMFAC2021 includes updates to modules, pollutants, 
emissions factors and data on car and truck activities, and emissions 
reductions associated with new and amended regulations reducing 
emissions from heavy-duty diesel trucks and buses.\8\
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    \8\ Regulations include the Advanced Clean Truck, Innovative 
Clean Transit, Heavy-duty Omnibus, Heavy-Duty Emission Warranty 
Phase 1, Heavy-duty Vehicle Inspection, and Periodic Smoke 
Inspection Programs. Requests for waivers of CAA section 209(a) 
preemption, which prohibits states and political subdivisions from 
adopting and enforcing emission standards for new motor vehicles and 
engines, have been submitted by CARB to the EPA for the new 
regulations that require such a waiver, i.e., the Advanced Clean 
Truck and the Heavy-duty Omnibus regulations. CARB has submitted a 
request that the EPA confirm that the Heavy-Duty Emission Warranty 
Phase 1 regulation falls within the scope of an existing waiver, or 
in the alternative that a waiver be granted.
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    New features in EMFAC2021 include the addition of plug-in hybrid 
and natural gas-powered vehicles, the addition of ammonia emissions, 
and new forecasting approaches for heavy-duty and light-duty vehicles. 
New methodologies for brake and tire wear and evaporative emissions are 
included; and new emissions factor data have been developed based on 
CARB's Vehicle, Truck and Bus Surveillance Programs, the EPA's In-Use 
Vehicle Program, dynamometer and Portable Emission Measurement Systems 
data, and transit bus testing. Motor vehicle fleet age, vehicle types, 
and vehicle populations have also been updated based on 2013-2019 
California Department of Motor Vehicle data, International Registration 
Plan data, Port Vehicle Identification Number data, California Highway 
Patrol School Bus Inspections data, and National Transit Database 
information. Each of these changes affect emissions factors for each 
area in California. CARB's website describes these and other model 
changes.\9\
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    \9\ https://ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory/msei-modeling-tools-emfac-software-and.
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F. What is included in the EMFAC2017 adjustment factors?

    CARB has developed adjustment factors for EMFAC2017 that account 
for the emissions reductions associated with the same regulations 
included in EMFAC2021. When EMFAC2017 was developed and submitted to 
the EPA for approval, the model included regulations adopted by CARB as 
of December 2017.\10\ From 2018-2021, CARB adopted new regulations and 
amended existing regulations that will reduce emissions from heavy-duty 
diesel trucks and buses, including the Advanced Clean Truck, Innovative 
Clean Transit, Heavy-duty Omnibus, Heavy-duty Warranty Phase 1, Heavy-
duty Vehicle Inspection, and Periodic Smoke Inspection Programs. The 
EMFAC2017 adjustment factors would be applied to the emission output of 
the EMFAC2017 model for all vehicle categories by calendar year to 
account for the benefits of these new regulations in motor vehicle 
emission budgets (``budgets'') and in conformity analyses to such 
budgets.
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    \10\ For further information, see the EPA's Notice of 
Availability for EMFAC2017 (84 FR 41717, August 15, 2019).
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G. How were stakeholders and the public involved in the EMFAC 
development process?

    Since 2019, CARB has held a series of public workshops to discuss 
emissions inventory updates and EMFAC updates, and to receive comments 
on the resulting changes in the emissions inventory and models.\11\ 
CARB also conducted beta testing of interim versions of the model with 
air districts and metropolitan planning organizations (MPOs). 
Stakeholders and other members of the public had the opportunity to 
request briefings with CARB staff and provide them with comments and 
suggestions to improve the model. CARB also developed and posted 
training materials for EMFAC2021 and supports a mobile source emissions 
inventory email listserv to announce updates and changes to the EMFAC 
supporting material.\12\
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    \11\ https://ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory/msei-meetings-workshops.
    \12\ To subscribe to CARB's listserv for Mobile Source Emission 
Inventory development, click ``Subscribe'' at https://ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory.
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    CARB also made available to the public a technical document that 
describes updates to the model and public presentations that summarize 
the changes from earlier versions of the model. The technical 
documentation is available on CARB's website.\13\ CARB provided 
information on specific changes incorporated into the EMFAC2021 model 
and included all presentations from the public workshops on the CARB 
website.\14\
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    \13\ https://ww2.arb.ca.gov/our-work/programs/mobile-source-emissions-inventory/msei-modeling-tools-emfac-software-and.
    \14\ See https://ww2.arb.ca.gov/sites/default/files/2021-08/emfac2021_technical_documentation_april2021.pdf and https://www.arb.ca.gov/msei/workshop-meetings.htm.
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H. Future Updates to EMFAC

    On January 31, 2006, CARB submitted a letter to the EPA and to the 
California Division of the Federal Highway Administration (FHWA) 
indicating the State's intention to make future revisions to update 
EMFAC. These EMFAC updates would reflect, among other new information, 
updated vehicle fleet data every three years. In California, MPOs and 
air districts cannot update vehicle fleet data embedded within EMFAC, 
only CARB can update the fleet data with each new EMFAC update because 
of the model design. The EPA's July 2004 final rule \15\ states that 
new vehicle registration data must be used when available, prior to the 
start of new conformity analyses, and that states and MPOs are strongly 
encouraged to update the data at least every five years as described in 
guidance issued December 2008 by the EPA and U.S. Department of 
Transportation (DOT).\16\ CARB's next

[[Page 68486]]

update to the planning assumptions in EMFAC is expected in 2024.
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    \15\ 69 FR 40004 (July 1, 2004).
    \16\ For more information, see the EPA and DOT's joint 
``Guidance for The Use of Latest Planning Assumptions in 
Transportation Conformity Determinations'' (EPA420-B-08-901, 
December 2008).
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II. The EPA's Action

A. What actions are the EPA taking in this notice?

    In this notice, the EPA is approving and announcing that EMFAC2021 
\17\ is available for use in statewide California SIP development, and 
for transportation conformity regional emissions analyses, and CO, 
PM10, and PM2.5 hot-spot analyses. The EPA is 
approving both the desktop computer and web platform for version 1.02 
of the EMFAC2021 model. CARB has provided documentation that these two 
forms of EMFAC2021 would be identical for criteria pollutant analyses 
for SIP and conformity purposes.
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    \17\ EMFAC2021, v1.0.2 (October 14, 2022 release).
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    The EPA is also approving the EMFAC2017 adjustment factors and 
announcing that the factors are available for use in statewide 
California SIP development and in regional conformity emissions 
analyses where SIPs are based on EMFAC2017 with adjustment factors. 
However, EMFAC2017 adjustment factors are not approved for CO, 
PM10, or PM2.5 hot-spot analyses for 
transportation conformity.
    Because the EMFAC model is used only in California, the EPA's 
statewide approval of the model does not affect the applicability of 
the MOVES emissions factor model for users in other states. The EPA 
also notes that this approval action does not affect the methodology 
required for calculating re-entrained road dust for PM10 and 
PM2.5 SIP revisions and transportation conformity analyses. 
Estimates for PM10 and PM2.5 in EMFAC2021 do not 
include such emissions. When applicable, PM10 and 
PM2.5 nonattainment and maintenance areas are required to 
use the EPA's AP-42 road dust method for calculating road dust 
emissions, unless a local method is approved in advance by the EPA.\18\
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    \18\ For further information, see the EPA's notice of 
availability for the January 2011 AP-42 Method for Estimating Re-
entrained Road Dust from Paved Roads (76 FR 6328, February 4, 2011). 
Also, for using AP-42 for unpaved roads, see the EPA's memorandum 
dated August 2, 2007, ``Policy Guidance on the Use of the November 
1, 2006, Update to AP-42 for Re-entrained Road Dust for SIP 
Development and Transportation Conformity.''
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    Use of these EMFAC models in SIP revisions is covered further in 
section II.B, and use of these EMFAC models for conformity is covered 
further in section II.C. The grace period for conformity is covered in 
section II.D.

B. Can EMFAC2021 and EMFAC2017 adjustment factors be used for SIP 
development?

    The EPA is approving EMFAC2021 and EMFAC2017 adjustment factors for 
areas in California to use for SIP development. The EPA has previously 
articulated its policy with respect to how new emissions models are 
used in SIPs in earlier EMFAC approval notices as well as in MOVES 
policy guidance and Federal Register announcements. This notice 
describes how this policy applies for EMFAC2021 and EMFAC2017 
adjustment factors.
    EMFAC2021 should be used to estimate emissions of hydrocarbon (HC), 
CO, NOX, PM10, PM2.5, ammonia, and 
sulfur oxides in SIP revisions that are being developed for individual 
nonattainment and maintenance areas in California as expeditiously as 
possible. The CAA requires that SIP inventories and control measures be 
based on the most current information and applicable models that are 
available when a SIP revision is developed and thus there is no grace 
period for use of EMFAC2021 in SIP revisions. However, the EPA also 
recognizes the time and level of effort that air quality planning 
agencies may have already undertaken in SIP development using 
EMFAC2017. Agencies should consult with EPA Region IX if they have 
questions about how EMFAC2021 affects SIP revisions under development 
in specific nonattainment or maintenance areas. Early consultation can 
facilitate the EPA's adequacy finding for motor vehicle emissions 
budgets for transportation conformity purposes or the EPA's action on 
SIP revisions.
    Agencies should use the latest version of EMFAC that is available 
at the time that a SIP is developed. EMFAC2021 should be used for SIP 
revisions that will be submitted in the future so that they are based 
on the most accurate estimates of emissions possible. However, agencies 
that have already completed significant work on a SIP revision using 
EMFAC2017 (e.g., attainment modeling has already been completed with 
EMFAC2017) may continue to rely on this earlier version of EMFAC 
because significant work has already occurred based on the latest 
information available at the time the SIP revision was developed.
    The CAA does not require agencies that have already submitted SIP 
revisions or will submit SIP revisions shortly after the release of a 
new model to revise these SIP revisions simply because a new motor 
vehicle emissions model is now available.
    CARB's request for the EPA to approve EMFAC2017 adjustment factors 
helps in this regard because these adjustment factors address a gap for 
those agencies that have been diligently working towards meeting SIP 
submission deadlines with the latest emissions model available at the 
time. The adjustment factors allow the emissions benefits of the latest 
CARB rules that are included in EMFAC2021 to be included in these SIP 
revisions as well, which will help these areas demonstrate attainment 
of the NAAQS. Note that EMFAC2017 adjustment factors are approved for 
use in nonattainment and maintenance area SIP revisions only where 
agencies have already completed significant SIP work with EMFAC2017. In 
all other cases, agencies should use EMFAC2021, particularly in 
instances where SIP development is in its initial stages or has not 
progressed far enough along that switching from a previous model 
version would create a significant adverse impact on state and local 
resources.
    Incorporating EMFAC2021 into an individual area's nonattainment and 
maintenance SIP revisions now could assist areas in mitigating possible 
transportation conformity difficulties in the future after the 
EMFAC2021 transportation conformity grace period ends.\19\ New regional 
emissions analyses using the emissions model that are started after the 
grace period is over must be based on EMFAC2021,\20\ so having 
EMFAC2021-based budgets in place at that time could provide more 
consistency with transportation conformity determinations.
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    \19\ Transportation conformity grace periods are discussed later 
in this notice in section II.D.
    \20\ 40 CFR 93.111.
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    When individual area SIP revisions based on either EMFAC2021 or 
EMFAC2017 with adjustment factors are submitted to the EPA, we will 
begin the adequacy process for the motor vehicle emissions budgets 
according to the process in 40 CFR 93.118(f) and find them adequate if 
they meet the criteria in 40 CFR 93.118(e). However, we will not be 
able to approve SIP revisions based on EMFAC2021 or EMFAC2017 
adjustment factors unless applicable regulations preempted by section 
209(a) of the CAA, that are included in EMFAC2021 and EMFAC2017 
adjustment factors, have been granted a waiver by the EPA under section 
209(b) of the CAA. California's new motor vehicle emissions standards 
are preempted under section 209(a) of the CAA and therefore, California 
can only enforce such standards upon the EPA's

[[Page 68487]]

waiver of this preemption under section 209(b) of the CAA. The new 
regulations that CARB adopted that will require waiver actions include 
the Advanced Clean Truck, Heavy-duty Emission Warranty Phase 1, and the 
Heavy-duty Omnibus regulations.\21\ Based on a court decision, these 
regulations must also be approved into the California SIP before we can 
approve the SIP submissions for individual California areas that 
incorporate the associated emissions reductions to meet CAA 
requirements.\22\
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    \21\ CARB has submitted requests that the EPA grant California 
waivers of CAA section 209(a) preemption for the Advanced Clean 
Truck and the Heavy-Duty Omnibus regulations, and that the EPA 
confirm the Heavy-Duty Emission Warranty Phase 1 regulation falls 
within the scope of an existing waiver, or in the alternative that a 
waiver be granted. See footnote 8.
    \22\ Committee for a Better Arvin v. EPA, 786 F.3d 1169 (9th 
Cir. 2015). section 110(a) requires these standards to be 
enforceable before they are approved into a SIP.
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C. What transportation conformity analyses can EMFAC2021 and EMFAC2017 
adjustment factors be used for?

    The EPA is approving EMFAC2021 to estimate emissions of HC, CO, 
NOX, PM10, PM2.5, ammonia, and sulfur 
oxides in regional emissions analyses or transportation conformity 
determinations.\23\ The EPA is also approving the use of EMFAC2017 
adjustment factors to estimate regional emissions of these same 
pollutants for transportation conformity only in areas that have 
adequate SIP-approved budgets that are based on EMFAC2017 with 
adjustment factors. EMFAC2017 adjustment factors can be used only for 
regional conformity emissions analyses that are started before the end 
of the conformity grace period (as discussed in section II.E). For any 
regional emissions analyses that begin on or after that date, EMFAC2021 
must be used.
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    \23\ The EPA notes that EMFAC2021 can be used for CO2 
emissions analyses as well, but these analyses are not being used 
for SIP or transportation conformity purposes. In addition, although 
sulfur dioxide and ammonia are listed as potential precursors for 
PM2.5 formation in 40 CFR 93.102(b)(2)(v), these 
precursors have not been considered significant for the on-road 
mobile sources covered by transportation conformity in California to 
date.
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    The EPA is also approving EMFAC2021 to estimate CO, 
PM10, and PM2.5 emissions for conformity hot-spot 
analyses involving individual transportation projects. A hot-spot 
analysis is defined in 40 CFR 93.101 as an estimation of likely future 
localized pollutant concentrations and a comparison of those 
concentrations to the relevant NAAQS. This analysis is conducted on a 
smaller scale than a nonattainment or maintenance area, e.g., for a 
congested roadway intersection. Hot-spot analyses are completed for 
only certain types of transportation projects; see 40 CFR 93.123(a) and 
(b) for further information.
    However, note that EMFAC2017 adjustment factors are not approved 
for estimating CO, PM10, and PM2.5 emissions for 
conformity hot-spot analyses involving individual transportation 
projects. Because hot-spot analyses are not compared to SIP-approved 
budgets, there is no reason to use EMFAC2017 with adjustment factors 
for hot-spot analyses even in areas with budgets based on EMFAC2017 
with adjustment factors; EMFAC2021 can and should be used instead. 
(Note that during the conformity grace period (discussed in section 
II.D), EMFAC2017 without the adjustment factors could be used for hot-
spot analyses as well.) Furthermore, we believe project sponsors would 
want to use EMFAC2021 rather than EMFAC2017 for hot-spot analyses of 
transportation projects, such as PM hot-spot analyses on highway or 
terminal expansions involving significant new levels of diesel trucks 
(per 40 CFR 93.116 and 93.123), as it would allow them to incorporate 
the latest planning assumptions included in EMFAC2021 (per 40 CFR 
93.110).
    The EPA is approving EMFAC2021 and EMFAC2017 adjustment factors for 
transportation conformity purposes as described in this notice. The 
regulations included in these models have already been adopted by CARB, 
the State has completed its regulatory process, and CARB has submitted 
to the EPA the requests for waivers on the previously mentioned 
regulations. Thus, any regional emissions analyses that are based on 
these models meet the transportation conformity rule's requirement in 
40 CFR 93.122(a)(3)(i). The emission benefits from these regulations 
can be included in regional emissions analyses, even before the EPA 
approves the regulations into the statewide SIP.

D. Does this notice establish a transportation conformity grace period 
for the use of this model?

    The EPA is establishing a two-year grace period before EMFAC2021 is 
required for all new HC, NOX, PM10, 
PM2.5, and CO regional emissions analyses (e.g., supporting 
transportation plan and TIP conformity determinations) and a one-year 
grace period before EMFAC2021 is required in conformity analyses for 
all new CO, PM10, and PM2.5 hot-spot analyses 
supporting project-level conformity determinations. The grace period 
for regional emissions analyses begins on November 15, 2022 and ends on 
November 15, 2024. Areas have the option of using the new model for 
regional emissions analyses prior to the end of the grace period.
    The transportation conformity rule \24\ requires that conformity 
determinations be based on the latest motor vehicle emissions model 
approved by the EPA for SIP purposes for a state or area. Section 
176(c)(1) of the CAA states that ``. . . [t]he determination of 
conformity shall be based on the most recent estimates of emissions, 
and such estimates shall be determined from the most recent population, 
employment, travel, and congestion estimates. . . .''
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    \24\ 40 CFR 93.111.
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    When the EPA approves and announces the availability of a new 
emissions model such as EMFAC2021, the EPA will consult with DOT to 
establish a grace period before the model is required for conformity 
analyses.\25\ The conformity rule provides for a grace period for new 
emissions models of between 3 and 24 months after notice of 
availability is published in the Federal Register.\26\
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    \25\ 40 CFR 93.111(b).
    \26\ 40 CFR 93.111(b)(1).
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    The EPA articulated its intentions for establishing the length of a 
conformity grace period in the preamble to the 1993 transportation 
conformity rule: \27\
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    \27\ 58 FR 62211 (November 24, 1993).

    EPA and DOT will consider extending the grace period if the 
effects of the new emissions model are so significant that previous 
SIP demonstrations of what emission levels are consistent with 
attainment would be substantially affected. In such cases, States 
should have an opportunity to revise their SIPs before MPOs must use 
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the model's new emissions factors.

    In consultation with FHWA and the Federal Transit Administration, 
the EPA considers ``the degree of change in the model and the scope of 
re-planning likely to be necessary by MPOs in order to assure 
conformity'' in establishing the length of the grace period.\28\
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    \28\ 40 CFR 93.111(b)(2).
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    The EPA considered the time it will take state and local 
transportation and air quality agencies to conduct and provide 
technical support for analyses. State and local agencies will need to 
become familiar with the EMFAC2021 emissions model. Since 1993, the 
purpose of section 93.111(b) of the transportation conformity rule has 
been to provide a sufficient amount of time for MPOs and other state 
and local agencies to learn and employ new emissions models. The 
transition to a new emissions model for conformity

[[Page 68488]]

involves more than learning to use the new model and preparing input 
data and model output.
    In addition to incorporating the new EMFAC2021 emissions rate and 
fleet data, state and local agencies also need to consider how the 
model affects regional conformity analysis results and whether SIP and/
or transportation plan/TIP changes are necessary to assure future 
conformity determinations. As stated earlier in the notice, the changes 
to EMFAC affect emissions factors for each area in California. CARB has 
requested a 24-month grace period for regional emissions analyses to 
allow them to update SIP revisions previously developed using EMFAC2014 
or EMFAC2017 with the updated emissions from EMFAC2021, as necessary. 
The EPA agrees that a two-year regional emissions analysis grace period 
provides time for CARB to revise previously approved SIP revisions with 
EMFAC2021 if needed so that MPOs can incorporate revised SIP-approved 
motor vehicle emission budgets into the transportation conformity 
process.
    When the regional emissions analysis grace period ends on November 
15, 2024, EMFAC2021 will become the only approved motor vehicle 
emissions model for all new regional transportation conformity analyses 
in California for meeting the requirement to use the latest emissions 
information in conformity analyses. In general, this means that all new 
HC, NOX, PM10, PM2.5, and CO regional 
conformity analyses started after the end of the two-year grace period 
must be based on EMFAC2021, even if the SIP is based on an earlier 
version of the EMFAC model, such as EMFAC2014, EMFAC2017, or EMFAC2017 
with adjustment factors.
    In addition, in most cases, if an area revises previously approved 
EMFAC2014 or EMFAC2017-based SIP-approved budgets using EMFAC2021, the 
revised EMFAC2021 budgets would be used for conformity purposes once 
the EPA approves the SIP revision. In general, the EPA will not make 
adequacy findings for these SIP revisions because submitted SIPs cannot 
supersede approved budgets until they are approved. However, 40 CFR 
93.118(e)(1) allows an approved budget to be replaced by an adequate 
budget if the EPA's approval of the initial budgets specifies that the 
budgets being approved may be replaced in the future by new adequate 
budgets. This flexibility has been used in limited situations in the 
past, such as during the transition from EMFAC7F and EMFAC7G to 
EMFAC2002.\29\ In such cases, the EMFAC2021-based budgets would be used 
for conformity purposes once they have been found adequate. California 
air agencies should consult with the EPA as needed to determine if this 
flexibility applies.
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    \29\ 67 FR 46618 (July 16, 2002), 67 FR 69139 (November 15, 
2002), and 68 FR 15720 (April 1, 2003).
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    Upon consideration of the transportation conformity rule's factors, 
the EPA is also establishing a one-year grace period before EMFAC2021 
is required in conformity analyses for all new CO, PM10 and 
PM2.5 hot-spot analyses supporting project-level conformity 
determinations. The grace period for hot-spot analyses begins on 
November 15, 2022 and ends on November 15, 2023. Areas have the option 
of using the new model for hot-spot analyses prior to the end of the 
grace period.
    For application of EMFAC2021 at the project level, the application 
of EMFAC2021 and the model's overall design and interface are similar 
to EMFAC2017. As a result, project sponsors developing future hot-spot 
analyses for projects that require such analyses in CO and PM 
nonattainment and maintenance areas that have already used EMFAC2021 
should not need significant time to familiarize themselves with this 
model.\30\ In addition, the fact that time may be needed for revising 
SIPs or transportation plans/TIPs due to the emissions factor changes 
in EMFAC2021 is irrelevant for hot-spot analyses because hot-spot 
analyses do not rely upon such planning documents. But while 
EMFAC2021's model design and interface has not significantly changed 
from EMFAC2017, project sponsors may still need some time to 
familiarize themselves with CARB's updated EMFAC2021-PL handbook and 
consider technical resource allocation issues to incorporate EMFAC2021 
into any future hot-spot analyses in multiple CO, PM10, and 
PM2.5 nonattainment and maintenance areas across California.
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    \30\ The EPA's PM Hot-Spot Guidance, found on the EPA's website 
at: https://www.epa.gov/state-and-local-transportation/project-level-conformity-and-hot-spot-analyses, continues to apply for PM 
hot-spot analyses along with CARB's PL handbook for EMFAC2021.
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    Therefore, it is appropriate to set a one-year grace period to 
allow all areas in California to incorporate EMFAC2021 in conformity 
hot-spot analyses for required project types and apply the updated 
planning assumptions incorporated in EMFAC2021 in a timely manner. In 
the interim, new PM and CO hot-spot analyses that are started prior to 
the end of the EMFAC2021 grace period can be based on EMFAC2017.\31\
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    \31\ 40 CFR 93.111(c); see also the EPA's website: https://www.epa.gov/state-and-local-transportation/project-level-conformity-and-hot-spot-analyses for the latest guidance documents and 
information.
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    When the hot-spot analysis grace period ends on November 15, 2023, 
EMFAC2021 will become the only approved motor vehicle emissions model 
for all new hot-spot transportation conformity analyses for required 
project types across California for meeting the requirement to use the 
latest emissions information in conformity. In general, this means that 
all new CO, PM10, and PM2.5 hot-spot analyses 
started after the end of the one-year grace period must be based on 
EMFAC2021 rather than EMFAC2017.

E. Can areas use EMFAC2017 during the grace period?

    The conformity rule provides some flexibility for regional 
emissions analyses that are started before the end of the grace 
period.\32\ Analyses that begin before or during the grace period may 
continue to rely on EMFAC2017. Also note that these regional emissions 
analysis results, when compared to an EMFAC2017-based motor vehicle 
emissions budget, can include the EMFAC2017 adjustment factors only if 
those adjustment factors were used in the motor vehicle emissions 
budget. This is the one case where a regional emissions analysis would 
need to use either EMFAC2017 with adjustment factors (or EMFAC2021) to 
show that conformity with the SIP is demonstrated. The interagency 
consultation process should be used if it is unclear if an EMFAC2017-
based analysis was begun before the end of the 24-month grace period. 
When the grace period ends, EMFAC2021 will become the EPA-approved 
motor vehicle emissions model for regional emissions analyses for 
transportation conformity in California.
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    \32\ 40 CFR 93.111(c).
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    CO, PM10, and PM2.5 hot-spot analyses for 
project-level conformity determinations can be based on EMFAC2017 if 
the analysis was started before the end of the 12-month grace period, 
and if the final environmental document for the project is issued no 
more than three years after the issuance of the draft environmental 
document.\33\ Quantitative analysis already underway that was started 
before the end of the grace period using EMFAC2017 can be completed as 
long as 40 CFR 93.111(c) is satisfied. The interagency consultation 
process should be used if

[[Page 68489]]

it is unclear whether an EMFAC2017-based analysis is covered by the 
circumstances described in the transportation conformity rule.
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    \33\ Id.
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III. Summary of the EPA's Actions

    As described in this notice, the EPA is approving and announcing 
the availability of EMFAC2021 and EMFAC2017 adjustment factors as 
submitted by CARB on October 14, 2022, for SIP, conformity, and 
applicable CAA purposes with the following limitations and conditions:
    (1) The approval is limited to California,
    (2) The approval is statewide and applies to estimation of 
emissions of HC, CO, NOX, PM10, PM2.5, 
ammonia and sulfur oxides. In addition, EMFAC2021 will be used for 
pollutants and precursors that are applicable in a given nonattainment 
or maintenance area. The EPA is approving the emissions factor elements 
of EMFAC2021, but not the associated default travel activity (e.g., 
vehicle miles traveled).
    (3) The approval of EMFAC2021 and EMFAC2017 adjustment factors is 
for the development of individual nonattainment and maintenance area 
SIPs. The EPA will not be able to approve these SIPs unless applicable 
regulations preempted by section 209(a) of the CAA included in 
EMFAC2021 and EMFAC2017 adjustment factors have been granted a waiver 
by the EPA under section 209(b) of the CAA. These regulations must also 
be approved into the California state SIP before we can approve SIP 
submissions for individual California areas.
    (4) A 24-month statewide transportation conformity grace period for 
regional emissions analyses will be established beginning November 15, 
2022 and ending November 15, 2024 for the transportation conformity 
uses described in (2) above.
    (5) The EPA is also approving EMFAC2021's Emission Rate Mode that 
allows the model to estimate project-level emissions for CO, 
PM10, and PM2.5 conformity hot-spot analyses.
    (6) The EPA is also approving EMFAC2017 adjustment factors that 
account for the emission reductions consistent with the CARB 
regulations incorporated into EMFAC2021 for use in SIP development and 
in regional emissions analyses for pollutants and precursors that are 
applicable in a given nonattainment or maintenance area that has SIP-
approved motor vehicle emissions budgets based on EMFAC2017 with 
adjustment factors. These adjustment factors can be used in regional 
emissions analyses for transportation conformity only until November 
15, 2024 and cannot be used in transportation conformity hot-spot 
analyses.
    (7) A 12-month statewide transportation conformity grace period for 
hot-spot analyses will be established beginning November 15, 2022 and 
ending November 15, 2023 for the transportation conformity uses 
described in (4) above.

    Dated: November 8, 2022.
Martha Guzman Aceves,
Regional Administrator, EPA Region IX.
[FR Doc. 2022-24790 Filed 11-14-22; 8:45 am]
BILLING CODE 6560-50-P