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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 1036, 1037, 1066, and 1068

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration 

49 CFR Parts 523 and 535

[EPA–HQ–OAR–2010–0162; NHTSA-2010-0096; FRL-xxxx-x]

RIN 2060-AP61; RIN XXXX-XXXX

Greenhouse Gas Emissions Standards and Fuel Efficiency Standards for HeavyDuty Engines and Vehicles

AGENCIES: Environmental Protection Agency (EPA) and National Highway 

Traffic Safety Administration (NHTSA).

ACTION: Proposed Rules

__________________________________________________________________

SUMMARY: 

The Environmental Protection Agency (EPA) and the National Highway Traffic Safety 

Administration (NHTSA) on behalf of the Department of Transportation, are each 

proposing rules to establish a comprehensive heavy-duty national program (the “HD 

National Program”) that will reduce greenhouse gas (GHG) emissions and increase fuel 

efficiency for on-road heavy-duty vehicles, responding to the President’s directive on 

May 21, 2010, to take coordinated steps to produce a new generation of clean vehicles. 

NHTSA’s proposed fuel consumption standards and EPA’s proposed carbon dioxide 

(CO2) emissions standards would be tailored to each of three regulatory categories of 

heavy-duty vehicles: (1) Combination Tractors; (2) Heavy-duty Pick-up Trucks and 

Vans; and (3) Vocational Trucks, as well as gasoline and diesel heavy-duty engines. 

EPA’s proposed hydrofluorocarbons emissions (from air conditioning) standards would 

apply to tractors, pickup trucks, and vans, and EPA’s proposed nitrous oxide (N2O) and 

methane (CH4) emissions standards would apply to all heavy-duty engines, pickup trucks,

and vans. 

EPA’s proposed GHG emission standards under the Clean Air Act (CAA) would begin 

with model year 2014. NHTSA’s proposed fuel consumption standards under the Energy

Independence and Security Act of 2007 (EISA) would be optional in model years 2014 

and 2015, becoming mandatory with model year 2016 for most regulatory categories. 

Commercial trailers would not be regulated in this phase of the HD National Program, 

although there is a discussion of the possibility of future action for trailers.
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DATES: 

Comments: Comments on all aspects of the heavy-duty greenhouse gas proposed rule 

must be received on or before XX [insert date], XX [insert #] days after publication in 

the Federal Register. Under the Paperwork Reduction Act, comments on the information 

collection provisions must be received by the Office of Management and Budget (OMB) 

on or before [Insert date 30 days after publication in the Federal Register], thirty

days after date of publication in the Federal Register. See the SUPPLEMENTARY 

INFORMATION section on “Public Participation” for more information about written 

comments.

Public Hearings: NHTSA and EPA will jointly hold two public hearings on the following 

dates: [date], 2010 in [location]; and [date], 2010 in [location]. The hearings will start at 9 

a.m. local time and continue until everyone has had a chance to speak. See the 

SUPPLEMENTARY INFORMATION section on “Public Participation” for more 

information about the public hearings.

[NOTE: NHTSA and EPA are continuing to finalize details of the hearings and will 

update this section to ensure the clearest instructions to the public.]

ADDRESSES: Submit your comments, identified by Docket ID No. NHTSA-2010-

0096 and/or EPA-HQ-OAR-2010-0162, by one of the following methods:

• www.regulations.gov: Follow the on-line instructions for submitting comments.

• Email: a-and-r-docket@epa.gov

• Fax: NHTSA: (202) 493-2251; EPA: (202) 566-9744

• Mail: 

NHTSA: Docket Management Facility, M-30, U.S. Department of 

Transportation, West Building, Ground Floor, Rm. W12-140, 1200 New Jersey

Avenue, SE, Washington, DC 20590.

EPA: Air Docket, Environmental Protection Agency, EPA Docket Center, 

Mailcode: 6102T, 1200 Pennsylvania Ave., NW., Washington, DC 20460. In 

addition, please mail a copy of your comments on the information collection 

provisions to the Office of Information and Regulatory Affairs, Office of 

Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th St. NW., 

Washington, DC 20503.

• Hand Delivery:

NHTSA: West Building, Ground Floor, Rm. W12-140, 1200 New Jersey

Avenue, SE, Washington, DC 20590, between 9 a.m. and 5 p.m. Eastern Time, 

Monday through Friday, except Federal Holidays.

EPA: EPA Docket Center, (Air Docket), U.S. Environmental Protection Agency, 

EPA West Building, 1301 Constitution Ave., N.W., Room: 3334, Mail Code 

2822T, Washington DC. Such deliveries are only accepted during the Docket’s 
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normal hours of operation, and special arrangements should be made for 

deliveries of boxed information.

Instructions: Direct your comments to Docket ID No. NHTSA-2010-0096 and/or EPAHQ-OAR-2010-0162. See the SUPPLEMENTARY INFORMATION section on 

“Public Participation” for additional instructions on submitting written comments.

Docket: All documents in the docket are listed in the www.regulations.gov index. 

Although listed in the index, some information is not publicly available, e.g., confidential 

business information (CBI) or other information whose disclosure is restricted by statute. 

Certain other material, such as copyrighted material, will be publicly available only in 

hard copy in EPA’s docket, but may be available electronically in NHTSA’s docket at 

regulations.gov. Publicly available docket materials are available either electronically in 

www.regulations.gov or in hard copy at the following locations: 

NHTSA: Docket Management Facility, M-30, U.S. Department of 

Transportation, West Building, Ground Floor, Rm. W12-140, 1200 New Jersey

Avenue, SE, Washington, DC 20590. The Docket Management Facility is open 

between 9 a.m. and 5 p.m. Eastern Time, Monday through Friday, except Federal 

holidays.

EPA: EPA Docket Center, EPA/DC, EPA West, Room 3334, 1301 Constitution 

Ave., NW, Washington, DC. The Public Reading Room is open from 8:30 a.m. 

to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone 

number for the Air Docket is (202) 566-1742.

FOR FURTHER INFORMATION CONTACT: NHTSA: Rebecca Yoon, Office of 

Chief Counsel, National Highway Traffic Safety Administration, 1200 New Jersey

Avenue, SE, Washington, DC 20590. Telephone: (202) 366-2992. EPA: [insert name], 

Office of Transportation and Air Quality, Assessment and Standards Division (ASD), 

Environmental Protection Agency, 2000 Traverwood Drive, Ann Arbor, MI 48105; 

telephone number: (734) 214-[XXXX]; fax number: (734) 214-[XXXX]; email address:

[insert appropriate email address, e.g., [lastname.firstname]@epa.gov], or 

Assessment and Standards Division Hotline; telephone number; (734) 214-4636; email 

asdinfo@epa.gov. 

SUPPLEMENTARY INFORMATION: 

A. Does this Action Apply to Me

This action would affect companies that manufacture, sell, or import into the United 

States new heavy-duty engines and new Class 2b through 8 trucks, including combination 

tractors, school and transit buses, vocational vehicles such as utility service trucks, as 
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well as 3⁄4-ton and 1-ton pickup trucks and vans.1 The heavy-duty category incorporates 

all motor vehicles rated at a gross vehicle weight of 8,500 pounds, and the engines that 

power them, except for medium-duty passenger vehicles already covered by the GHG 

and CAFE standards issued for model years 2012-2016. This action also includes a 

discussion of the possible future regulation of commercial trailers. Potentially affected 

categories and entities include the following: 

Category NAICS CodeaExamples of Potentially Affected Entities

Industry 336111 Motor Vehicle Manufacturers, Engine and Truck 

336112 Manufacturers

336120

Industry 541514 Commercial Importers of Vehicles and Vehicle 

811112 Components

811198

Industry 336111 Alternative Fuel Vehicle Converters

336112

422720

454312

541514

541690

811198

Industry 336212 Truck Trailer Manufacturersb

Note:

a

 North American Industry Classification System (NAICS)

b This category is included for purposes of advance notice of possible future rulemaking action 

This table is not intended to be exhaustive, but rather provides a guide for readers 

regarding entities likely to be regulated by this proposal. This table lists the types of 

entities that the agencies are 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 activities may be regulated by this action, you should carefully examine the 

applicability criteria in 40 CFR parts 1036, 1037, 49 CFR parts 523 and 535, and the 

proposed regulations. You may direct questions regarding the applicability of this action 

to the persons listed in the preceding FOR FURTHER INFORMATION CONTACT

section.

B. Public Participation

NHTSA and EPA request comment on all aspects of these joint proposed rules. This 

section describes how you can participate in this process.

 

1

For purposes of NHTSA’s fuel consumption regulations, non-commercial recreational vehicles will not be 

covered, even if they would otherwise fall under these categories. See 49 U.S.C. § 32901(a)(7).
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(1) How Do I Prepare and Submit Comments?

In this joint rulemaking, there are many issues common to both EPA’s and NHTSA’s 

proposals. For the convenience of all parties, comments submitted to the EPA docket 

(whether hard copy or electronic) will be considered comments submitted to the NHTSA 

docket, and vice versa. An exception is that comments submitted to the NHTSA docket 

on the Draft Environmental Impact Statement will not be considered submitted to the 

EPA docket. Therefore, the public only needs to submit comments to either one of the 

two agency dockets. Comments that are submitted for consideration by one agency

should be identified as such, and comments that are submitted for consideration by both 

agencies should be identified as such. Absent such identification, each agency will 

exercise its best judgment to determine whether a comment is submitted on its proposal. 

Further instructions for submitting comments to either the EPA or NHTSA docket are 

described below. 

 

NHTSA: Your comments must be written and in English. To ensure that your 

comments are correctly filed in the Docket, please include the Docket I.D No.NHTSA2010-0096 in your comments. By regulation, your comments must not be more than 15 

pages long.2 NHTSA established this limit to encourage you to write your primary

comments in a concise fashion. However, you may attach necessary additional 

documents to your comments. There is no limit on the length of the attachments. If you 

are submitting comments electronically as a PDF (Adobe) file, we ask that the documents 

submitted be scanned using the Optical Character Recognition (OCR) process, thus 

allowing the agencies to search and copy certain portions of your submissions.3 Please 

note that pursuant to the Data Quality Act, in order for the substantive data to be relied 

upon and used by the agencies, it must meet the information quality standards set forth in 

the OMB and Department of Transportation (DOT) Data Quality Act guidelines. 

Accordingly, we encourage you to consult the guidelines in preparing your comments. 

OMB’s guidelines may be accessed at 

http://www.whitehouse.gov/omb/fedreg/reproducible.html. DOT’s guidelines may be 

accessed at http://regs.dot.gov.

EPA: Direct your comments to Docket ID No EPA-HQ-OAR-2010-0162. EPA’s policy

is that all comments received will be included in the public docket without change and 

may be made available online at www.regulations.gov, including any personal 

information provided, unless the comment includes information claimed to be 

Confidential Business Information (CBI) or other information whose disclosure is 

restricted by statute. Do not submit information that you consider to be CBI or otherwise 

protected through www.regulations.gov or e-mail. The www.regulations.gov website is 

an “anonymous access” system, which means EPA will not know your identity or contact 

information unless you provide it in the body of your comment. If you send an e-mail 

 

2

See 49 CFR § 553.21

3 Optical character recognition (OCR) is the process of converting an image of text, such as a scanned 

paper document or electronic fax file, into computer-editable text.
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comment directly to EPA without going through www.regulations.gov your e-mail 

address will be automatically captured and included as part of the comment that is placed 

in the public docket and made available on the Internet. If you submit an electronic 

comment, EPA recommends that you include your name and other contact information in 

the body of your comment and with any disk or CD-ROM you submit. If EPA cannot 

read your comment due to technical difficulties and cannot contact you for clarification, 

EPA may not be able to consider your comment. Electronic files should avoid the use of 

special characters, any form of encryption, and be free of any defects or viruses. For 

additional information about EPA’s public docket visit the EPA Docket Center homepage 

at http://www.epa.gov/epahome/dockets.htm. 

(2) Tips for Preparing Your Comments. 

When submitting comments, remember to:

 Identify the rulemaking by docket number and other identifying information (subject 

heading, Federal Register date and page number).

 Follow directions - The agency may ask you to respond to specific questions or 

organize comments by referencing a Code of Federal Regulations (CFR) part or 

section number.

 Explain why you agree or disagree, suggest alternatives, and substitute language for 

your requested changes.

 Describe any assumptions and provide any technical information and/or data that you 

used.

 If you estimate potential costs or burdens, explain how you arrived at your estimate in 

sufficient detail to allow for it to be reproduced.

 Provide specific examples to illustrate your concerns, and suggest alternatives.

 Explain your views as clearly as possible, avoiding the use of profanity or personal 

threats.

 Make sure to submit your comments by the comment period deadline identified in the 

DATES section above.

(3) How Can I Be Sure That My Comments Were Received?

NHTSA: If you submit your comments by mail and wish Docket Management to notify

you upon its receipt of your comments, enclose a self-addressed, stamped postcard in the 

envelope containing your comments. Upon receiving your comments, Docket 

Management will return the postcard by mail.

(4) How Do I Submit Confidential Business Information?

Any confidential business information (CBI) submitted to one of the agencies will also be 

available to the other agency.

4

 However, as with all public comments, any CBI 

 

4 This statement constitutes notice to commenters pursuant to 40 CFR § 2.209(c) that EPA will share 

confidential business information received with NHTSA unless commenters expressly specify that they 

wish to submit their CBI only to EPA and not to both agencies.
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information only needs to be submitted to either one of the agencies’ dockets and it will 

be available to the other. Following are specific instructions for submitting CBI to either 

agency.

NHTSA: If you wish to submit any information under a claim of confidentiality, you 

should submit three copies of your complete submission, including the information you 

claim to be CBI, to the Chief Counsel, NHTSA, at the address given above under FOR 

FURTHER INFORMATION CONTACT. When you send a comment containing 

CBI, you should include a cover letter setting forth the information specified in our CBI

regulation. In addition, you should submit a copy from which you have deleted the 

claimed CBI to the Docket by one of the methods set forth above.

EPA: Do not submit CBI to EPA through www.regulations.gov or e-mail. Clearly mark 

the part or all of the information that you claim to be CBI. For CBI information in a disk 

or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI and 

then identify electronically within the disk or CD ROM the specific information that is 

claimed as CBI. In addition to one complete version of the comment that includes 

information claimed as CBI, a copy of the comment that does not contain the information 

claimed as CBI must be submitted for inclusion in the public docket. Information so 

marked will not be disclosed except in accordance with procedures set forth in 40 CFR 

Part 2.

(5) Will the Agencies Consider Late Comments?

NHTSA and EPA will consider all comments received before the close of business on the 

comment closing date indicated above under DATES. To the extent practicable, we will 

also consider comments received after that date. If interested persons believe that any

new information the agency places in the docket affects their comments, they may submit 

comments after the closing date concerning how the agency should consider that 

information for the final rule. However, the agencies’ ability to consider any such late 

comments in this rulemaking will be limited due to the time frame for issuing a final rule.

If a comment is received too late for us to practicably consider in developing a final rule, 

we will consider that comment as an informal suggestion for future rulemaking action.

(6) How Can I Read the Comments Submitted by Other People?

You may read the materials placed in the dockets for this document (e.g., the comments 

submitted in response to this document by other interested persons) at any time by going 

to http://www.regulations.gov. Follow the online instructions for accessing the dockets. 

You may also read the materials at the NHTSA Docket Management Facility or the EPA 

Docket Center by going to the street addresses given above under ADDRESSES.

(7) How Do I Participate in the Public Hearings?

EPA and NHTSA will jointly host two public hearings on the dates and locations 

described in the DATES section above. If you would like to present testimony at a

public hearing, we ask that you notify both the NHTSA and EPA contact persons listed 

under FOR FURTHER INFORMATION CONTACT at least ten days before the 

hearing. Once the agencies learn how many people have registered to speak at the public 
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hearing, we will allocate an appropriate amount of time to each participant, allowing time 

for lunch and necessary breaks throughout the day. For planning purposes, each speaker 

should anticipate speaking for approximately ten minutes, although we may need to 

adjust the time for each speaker if there is a large turnout. We request that you bring two 

copies of your statement or other material for the agencies’ panels. To accommodate as 

many speakers as possible, we prefer that speakers not use technological aids (e.g., audiovisuals, computer slideshows). In addition, we will reserve a block of time for anyone 

else in the audience who wants to give testimony.

Each hearing will be held at a site accessible to individuals with disabilities. Individuals 

who require accommodations such as sign language interpreters should contact the 

persons listed under FOR FURTHER INFORMATION CONTACT section above no 

later than ten days before the date of the hearing.

EPA and NHTSA will conduct the hearing informally, and technical rules of evidence 

will not apply. We will arrange for a written transcript of each hearing and keep the 

official records of the hearings open for 30 days to allow you to submit supplementary

information. You may make arrangements for copies of a transcript directly with the 

court reporter.

C. Additional Information about this Rulemaking

EPA’s Advance Notice of Proposed Rulemaking (ANPR) for regulating greenhouse 

gases under the Clean Air Act (see 73 Fed Reg 44353, July 30, 2008) included a 

discussion of possible rulemaking paths for the heavy-duty transportation sector. This 

notice of proposed rulemaking relies in part on information that was obtained from that 

notice, which can be found in Public Docket EPA-HQ-OAR-2008-0318. That docket is 

incorporated into the docket for this action, EPA-HQ-OAR-2010-0162.

Table of Contents

I. Overview

A. Introduction

B. Building Blocks of the Heavy-duty National Program

C. Summary of the Proposed EPA and NHTSA HD National Program

D. Summary of Costs and Benefits of the HD National Program

E. Program Flexibilities

F. EPA and NHTSA Statutory Authorities

G. Future HD GHG and Fuel Consumption Rulemakings

II. Proposed GHG and Fuel Consumption Standards for Heavy Duty Engines and Vehicles

A. What vehicles would be affected?

B. Class 7/8 Combination Tractors

C. Heavy-Duty Pickup Trucks and Vans

D. Class 2b-8 Vocational Trucks

E. EPA’s Proposed N20 and CH4 Standards

III. Feasibility Assessments and Conclusions

A. Class 7-8 Combination Tractors

B. Class 2b and 3 Complete Pickup Trucks and Vans

C. Class 2b-8 Vocational Vehicles

IV. Proposed Regulatory Flexibility Provisions

A. Averaging, Banking, and Trading (ABT) Program
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B. Class 2b/3 Heavy-duty Pickup Trucks and Vans Flexibility Provisions

C. Additional Proposed Flexibility Provisions

V. NHTSA and EPA Proposed Compliance, Certification, and Enforcement Provisions

A. Overview

B. Heavy-duty Pickup Trucks and Vans

C. Heavy-Duty Engines

D. Class 7/8 Combination Trucks

E. Class 2b-8 Vocational Trucks

F. Statutory Prohibited Acts

G. NHTSA Enforcement Penalties

VI. How Would This Proposed Program Impact Fuel Consumption, GHG Emissions, and Climate 

Change?

A. What methodologies did the agencies use to project GHG emissions and fuel consumption impacts?

B. MOVES Analysis

C. What are the projected reductions in fuel consumption and GHG emissions?

D. Overview of Climate Change Impacts from GHG Emissions

E. Changes in Atmospheric CO2 Concentrations, Global Mean Temperature, Sea Level Rise, and Ocean 

pH Associated with the Proposal’s GHG Emissions Reductions

VII. How Would This Proposal Impact Non-GHG Emissions and Their Associated Effects?

A. Emissions Inventory Impacts

B. Health Effects of Non-GHG Pollutants

C. Environmental Effects of Non-GHG Pollutants

D. Air Quality Impacts of Non-GHG Pollutants

VIII. What are the Agencies' Estimated Cost, Economic, and Other Impacts of the Proposed 

Program?

A. Conceptual Framework for Evaluating Impacts

B. Costs Associated with the proposed program

C. Indirect Cost Multipliers

D. Cost per Ton of Emissions Reductions

E. Impacts of Reduction in Fuel Consumption

F. Class Shifting and Fleet Turnover Impacts

G. Benefits of Reducing CO2 Emissions

H. Non-GHG Health and Environmental Impacts

I. Energy Security Impacts

J. Other Impacts

K. Summary of Costs and Benefits

L. Economy-Wide Impacts of the Rule

IX. Analysis of Alternatives

A. What are the alternatives that the agencies considered?

B. How do these alternatives compare in overall GHG emissions reductions and fuel efficiency and cost?

C. How would the agencies include commercial trailers, as described in Alternative 7?

X. Recommendations from the March 2010 NAS Report

A. Overview

B. What were the major findings and recommendations of the March 2010 NAS Report, and how is the 

proposed HD National Program consistent with them?

XI. Statutory and Executive Order Reviews

XII. Statutory Provisions and Legal Authority

A. EPA

B. NHTSA
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I. Overview

A. Introduction

The Environmental Protection Agency (EPA) and the National Highway Traffic 

Safety Administration (NHTSA) (“the agencies”) are announcing a first-ever program to 

reduce greenhouse gas (GHG) emissions and improve fuel efficiency in the heavy-duty 

highway vehicle sector. This broad sector – ranging from large pickups to sleeper-cab

tractors – together represent the second largest contributor to oil consumption and GHG

emissions, after light-duty passenger cars and trucks. 

In a recent memorandum to the Administrators of EPA and NHTSA (and the 

Secretaries of Transportation and Energy), the President stated that “America has the 

opportunity to lead the world in the development of a new generation of clean cars and 

trucks through innovative technologies and manufacturing that will spur economic 

growth and create high-quality domestic jobs, enhance our energy security, and improve 

our environment.” 5 Earlier this year, EPA and NHTSA established for the first time a 

national program to sharply reduce GHG emissions and fuel consumption from passenger 

cars and light trucks. Now, each agency is proposing rules that together would create a 

strong and comprehensive program (the “Heavy-Duty (HD) National Program”) designed 

to address the urgent and closely intertwined challenges of dependence on oil, energy

security, and global climate change. At the same time, the proposed program would 

enhance American competitiveness and job creation, benefit consumers and businesses 

by reducing costs for transporting goods, and spur growth in the clean energy sector. 

A number of major HD truck and engine manufacturers representing the vast 

majority of this industry, and the California Air Resources Board, sent letters to EPA and 

NHTSA supporting a HD National Program based on a common set of principles. In the 

letters, the stakeholders commit to working with the agencies and with other stakeholders 

toward a program consistent with common principles, including:

 Increased use of existing technologies to achieve significant GHG 

emissions and fuel consumption reductions;

 A program that starts in 2014 and is fully phased in by 2018;

 A program that works towards harmonization of methods for determining 

a vehicle’s GHG and fuel efficiency, recognizing the global nature of the 

issues and the industry;

 Standards that recognize the commercial needs of the trucking industry; 

and

 

5

Improving Energy Security, American Competitiveness and Job Creation, and Environmental Protection 

Through a Transformation of Our Nation’s Fleet of Cars And Trucks,” Issued May 21, 2010, published at 

75 FR 29399 (May 26, 2010).
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 Incentives leading to the early introduction of advanced technologies.

The proposed HD National Program builds on many years of heavy-duty engine 

and vehicle technology development to achieve what the agencies believe would be the 

greatest degree of GHG emission and fuel consumption reduction appropriate, feasible, 

and cost-effective for the model years in question. Still, by proposing to take aggressive 

steps that are reasonably possible now, based on the technological opportunities and 

pathways that present themselves during these model years, the agencies and industry

will also continue learning about emerging opportunities for this complex sector to 

further reduce GHG emissions and fuel consumption. For example, NHTSA and EPA 

have stopped short of proposing fuel consumption and GHG standards for trucks based 

on use of hybrid powertrain technology. Similarly, we expect that the agencies will 

participate in efforts to improve our ability to accurately characterize the actual in-use

fuel consumption and emissions of this complex sector. As such opportunities emerge in 

the coming years, we expect that we will propose a second phase of provisions in the 

future to reinforce these developments and maximize the achieved reductions in GHG 

emissions and fuel consumption reduction for the mid- and longer-term time frame.

In the May 21 memorandum, the President requested the Administrators of EPA 

and NHTSA to “immediately begin work on a joint rulemaking under the Clean Air Act 

(CAA) and the Energy Independence and Security Act of 2007 (EISA) to establish fuel 

efficiency and greenhouse gas emissions standards for commercial medium- and heavyduty vehicles beginning with model year 2014, with the aim of issuing a final rule by July

30, 2011.” This proposed rulemaking is consistent with this Presidential Memorandum, 

with each agency proposing rules under its respective authority that together comprise a 

coordinated and comprehensive HD National Program.

Heavy-duty vehicles move much of the nation’s freight and carry out numerous 

other tasks, including utility work, concrete delivery, fire response, refuse collection, and 

many more. Heavy-duty vehicles are primarily powered by diesel engines, although 

about 37 percent of these vehicles are powered by gasoline engines. Heavy-duty trucks6

have always been an important part of the goods movement infrastructure in this country

and have experienced significant growth over the last decase related to increased imports 

and exports of finished goods and increased shipping of finished goods to homes through 

internet purchases.

The heavy-duty sector is extremely diverse in several respects, including types of 

manufacturing companies involved, the range of sizes of trucks and engines they

produce, the types of work the trucks are designed to perform, and the regulatory history 

of different subcategories of vehicles and engines. The current heavy-duty fleet 

encompasses vehicles from the “18-wheeler” combination trucks one sees on the 

 

6

 In this rulemaking, EPA and NHTSA use the term “truck” in a general way, referring to all categories of 

regulated heavy-duty highway vehicles (including buses). As such, the term is generally interchangeable 

with “heavy-duty vehicle.”
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highway to school and transit buses, to vocational vehicles such as utility service trucks, 

as well as the largest pickup trucks and vans.

For purposes of this preamble, the term “heavy-duty” or “HD” is used to apply to 

all highway vehicles and engines that are not within the range of light-duty vehicles, 

light-duty trucks, and medium-duty passenger vehicles (MDPV) covered by the GHG and 

Corporate Average Fuel Economy (CAFE) standards issued for model years (MY) 2012-

2016.7 It also does not include motorcycles. Thus, in this notice, unless specified 

otherwise, the heavy-duty category incorporates all vehicles rated at a gross vehicle 

weight above 8,500 pounds, and the engines that power them, except for MDPVs.8 We 

note that the Energy Independence and Security Act of 2007 requires NHTSA to set 

standards for “commercial medium- and heavy-duty on-highway vehicles and work 

trucks.”

9

 NHTSA interprets this to include all segments of the heavy-duty category

described above, except for recreational vehicles, such as motor homes, since recreational 

vehicles are not commercial. 

Setting GHG emissions standards for the heavy-duty sector will help to address 

climate change, which is widely viewed as a significant long-term threat to the global 

environment. As summarized in the Technical Support Document for EPA’s 

Endangerment and Cause or Contribute Findings under Section 202(a) of the Clean Air 

Act, anthropogenic emissions of GHGs are very likely (a 90 to 99 percent probability) the 

cause of most of the observed global warming over the last 50 years.10 The primary

GHGs of concern are carbon dioxide (CO2), methane, nitrous oxide, hydrofluorocarbons, 

perfluorocarbons, and sulfur hexafluoride. Mobile sources emitted 31 percent of all U.S. 

GHGs in 2007 (transportation sources, which do not include certain off-highway sources, 

account for 28 percent) and have been the fastest-growing source of U.S. GHGs since 

1990.11 Mobile sources addressed in the recent endangerment and contribution findings 

under CAA section 202(a) -- light-duty vehicles, heavy-duty trucks, buses, and 

motorcycles -- accounted for 23 percent of all U.S. GHG emissions in 2007.12 Heavy-

 

7

 Light-Duty Vehicle Greenhouse Gas Emission Standards and Corporate Average Fuel Economy 

Standards; Final Rule 75 FR 25323 (May 7, 2010).

8

 The CAA defines heavy-duty as a truck, bus or other motor vehicles with a gross vehicle weight rating 

exceeding 6,000 pounds (CAA section 202(b)(3)). The term HD as used in this action refers to a subset of 

these vehicles and engines. 

9

49 U.S.C. 32902(k)(2). “Commercial medium- and heavy-duty on-highway vehicles” are defined as onhighway vehicles with a gross vehicle weight rating of 10,000 pounds or more, while “work trucks” are 

defined as vehicles rated between 8,500 and 10,000 pounds gross vehicle weight that are not MDPVs. See

49 U.S.C. 32901(a)(7) and (a)(19).

10 “Technical Support Document for Endangerment and Cause or Contribute Findings for Greenhouse 

Gases Under Section 202(a) of the Clean Air Act” available at Docket: EPA-HQ-OAR-2009-0472-11292, 

and athttp://epa.gov/climatechange/endangerment.html.

11 U.S. Environmental Protection Agency. 2009. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 

1990-2007. EPA 430-R-09-004. Available at 

http://epa.gov/climatechange/emissions/downloads09/GHG2007entire_report-508.pdf 

12 U.S. EPA. 2009 Technical Support Document for Endangerment and Cause or Contribute Findings for 

Greenhouse Gases under Section 202(a) of the Clean Air Act. Washington, DC. pp. 180-194. Available at 

http://epa.gov/climatechange/endangerment/downloads/Endangerment%20TSD.pdf 
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duty vehicles emit CO2, methane, nitrous oxide, and hydrofluorocarbons and are 

responsible for nearly 19 percent of all mobile source GHGs (nearly 6% of all U.S. 

GHGs) and about 25 percent of section 202(a) mobile source GHGs. For heavy-duty

vehicles in 2007, CO2 emissions represented more than 99 percent of all GHG emissions 

(including HFCs).

13

Setting fuel consumption standards for the heavy-duty sector, pursuant to 

NHTSA’s EISA authority, will also improve our energy security by reducing our 

dependence on foreign oil, which has been a national objective since the first oil price 

shocks in the 1970s. Net petroleum imports now account for approximately 60 percent of 

U.S. petroleum consumption. World crude oil production is highly concentrated, 

exacerbating the risks of supply disruptions and price shocks. Tight global oil markets 

led to prices over $100 per barrel in 2008, with gasoline reaching as high as $4 per gallon 

in many parts of the U.S., causing financial hardship for many families and businesses. 

The export of U.S. assets for oil imports continues to be an important component of the 

historically unprecedented U.S. trade deficits. Transportation accounts for about 72 

percent of U.S. petroleum consumption. Heavy-duty vehicles account for about 17

percent of transportation oil use, which means that they alone account for about 12

percent of all U.S. oil consumption.

14

In developing this joint proposal, the agencies have worked with a large and 

diverse group of stakeholders representing truck and engine manufacturers, trucking 

fleets, environmental organizations, and states including the State of California.15 While 

our discussions covered a wide range of issues and viewpoints, one widespread 

recommendation was that the two agencies should develop a common federal program 

with consistent standards of performance regarding fuel consumption and GHG 

emissions. The HD National Program we are proposing today is consistent with that 

goal. Further it is our expectation based on our ongoing work with the State of California 

that the California Air Resources Board (CARB) will be able to adopt regulations 

equivalent in practice to those of this National Program, just as it has done for past EPA 

regulation of heavy-duty trucks and engines. NHTSA and EPA are committed to 

continuing to work with CARB throughout this rulemaking process to help ensure our 

final rules can lead to that outcome.

In light of the industry’s diversity, and consistent with the recommendations of 

the National Academy of Sciences as discussed further below, the agencies are proposing 

a HD National Program that recognizes the different sizes and work requirements of this 

 

13 U.S. Environmental Protection Agency. 2009. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 

1990-2007. EPA 430-R-09-004. Available at 

http://epa.gov/climatechange/emissions/downloads09/GHG2007entire_report-508.pdf

14

 In 2009 Source: EIA Annual Energy Outlook 2010 released May 11, 2010

15 Pursuant to DOT Order 2100.2, NHTSA will place a memorandum recording those meetings that it 

attended and documents submitted by stakeholders which formed a basis for this proposal and which can be 

made publicly available in its docket for this rulemaking. DOT Order 2100.2 is available at 

http://regs.dot.gov.
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wide range of heavy-duty vehicles and their engines. NHTSA’s proposed fuel 

consumption standards and EPA’s proposed GHG standards would apply to 

manufacturers of the following types of heavy-duty vehicles and their engines; the 

proposed provisions for each of these are described in more detail below in this section:

 Heavy-duty Pickup Trucks and Vans

 Combination Tractors

 Vocational Trucks

As in the recent light-duty vehicle rule establishing CAFE and GHG standards 

for MYs 2012-2016 light-duty vehicles, EPA’s and NHTSA’s proposed standards for the 

heavy-duty sector are largely harmonized with one another due to the close and direct 

relationship between improving the fuel efficiency of these vehicles and reducing their 

carbon dioxide (CO2) tailpipe emissions. For all vehicles that consume carbon-based 

fuels, the amount of CO2 emissions is essentially constant per gallon for a given type of 

fuel that is consumed. The more efficient a heavy-duty truck is in completing its work, 

the lower its environmental impact will be, because the less fuel consumed to move cargo 

a given distance, the less CO2 emitted into the air. The technologies available for 

improving fuel efficiency, and therefore for reducing both CO2 emissions and fuel 

consumption, are one and the same.16 Because of this close technical relationship, 

NHTSA and EPA have been able to rely on jointly-developed assumptions, analyses, and 

analytical conclusions to support the standards and other provisions that NHTSA and 

EPA are proposing under our separate legal authorities.

The timelines for the implementation of the proposed NHTSA and EPA standards 

are also closely coordinated. EPA’s proposed GHG emission standards would begin in 

model year 2014. In order to provide for the four full model years of regulatory lead time 

required by EISA, as discussed in Section B.5 below, NHTSA’s proposed fuel 

consumption standards would be optional in model years 2014 and 2015, becoming 

mandatory in model year 2016, except for diesel engine standards which would be 

optional in model years 2014, 2015 and 2016, becoming mandatory in model year 2017. 

A detailed discussion of how the proposed standards are consistent with each agency’s 

respective statutory requirements and authorities is found later in this notice. 

Neither EPA nor NHTSA is proposing standards at this time for GHG emissions 

or fuel consumption, respectively, for heavy-duty commercial trailers. However, the 

agencies are considering proposing such standards in a future rulemaking, and request 

comment on such an action later in this preamble.

 

16 However, as discussed below, in addition to addressing CO2, the EPA’s proposed standards also include 

provisions to address other GHGs (nitrous oxide, methane, and air conditioning refrigerant emissions).), as 

required by the Endangerment Finding under the Clean Air Act. See Section II.
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B. Building Blocks of the Heavy-duty National Program

The standards that are being proposed in this notice represent the first time that 

EPA and NHTSA would regulate the heavy-duty sector for fuel consumption and GHG 

emissions. NHTSA and EPA are proposing standards for heavy-duty vehicles and their 

engines that are rooted in EPA’s prior regulatory history, the SmartWay Partnership 

program, and extensive technical and engineering analyses done at the federal level. This 

section summarizes some of the most important of these precursors and foundations for 

this HD National Program. 

(1) EPA’s Traditional Heavy-duty Regulatory Program

Since the 1980s, EPA has acted several times to address tailpipe emissions of 

criteria pollutants and air toxics from heavy-duty vehicles and engines. During the last 

18 years, these programs have primarily addressed emissions of ozone precursors 

(hydrocarbons and nitrogen oxides (NOX)) and particulate matter (PM). These programs 

have successfully achieved significant and cost-effective reductions in emissions and 

associated health and welfare benefits to the nation. They have been structured in ways 

that account for the varying circumstances of the engine and truck industries. As 

required by the CAA, the emission standards implemented by these programs include 

standards that apply at the time that the vehicle or engine is sold as well as standards that 

apply in actual use. As a result of these programs, new vehicles meeting current emission 

standards will emit 98% less NOX and 99% less PM than new trucks 20 years ago. The 

resulting emission reductions provide significant public health and welfare benefits. The 

most recent EPA regulations which were fully phased-in in 2010 are projected to provide 

greater than $70 billion in health and welfare benefits annually in 2030 alone.17

EPA’s overall program goal has always been to achieve emissions reductions 

from the complete vehicles that operate on our highways. The agency has often 

accomplished this goal for many heavy-duty truck categories through the regulation of 

heavy-duty engine emissions. A key part of this success has been the development over 

many years of a well-established, representative, and robust set of engine test procedures 

that industry and EPA now routinely use to measure emissions and determine compliance 

with emission standards. These test procedures in turn serve the overall compliance 

program that EPA implements to help ensure that emissions reductions are being 

achieved. By isolating the engine from the many variables involved when the engine is 

installed and operated in a HD vehicle, EPA has been able to accurately address the 

contribution of the engine alone to overall emissions. The agencies discuss below how 

the proposed program incorporates the existing engine-based approach used for criteria 

emissions regulations, as well as new vehicle-based approaches. 

 

17 66 FR 5002, January 18, 2001.
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(2) NHTSA’s Responsibilities to Regulate Heavy-Duty Fuel Efficiency 

under EISA

With the passage of the EISA in December 2007, Congress laid out a framework 

developing the first fuel efficiency regulations for HD vehicles. As codified at 49 U.S.C. 

§ 32902(k), EISA requires NHTSA to develop a regulatory system for the fuel economy 

of commercial medium-duty and heavy-duty on-highway vehicles and work trucks in 

three steps: a study by the National Academy of Sciences (NAS), a study by NHTSA, 

and a rulemaking to develop the regulations themselves.18

Specifically, section 102 of EISA, codified at 49 U.S.C. 32902(k)(2), states that 

not later than two years after completion of the NHTSA study, DOT (by delegation, 

NHTSA), in consultation with the Department of Energy and EPA, shall develop a 

regulation to implement a “commercial medium-duty and heavy-duty on-highway vehicle 

and work truck fuel efficiency improvement program designed to achieve the maximum 

feasible improvement.” NHTSA interprets the timing requirements as permitting a 

regulation to be developed earlier, rather than as requiring the agency to wait a specified 

period of time.

Congress specified that as part of the “HD fuel efficiency improvement program 

designed to achieve the maximum feasible improvement,” NHTSA must adopt and 

implement:

 Appropriate test methods;

 Measurement metrics;

 Fuel economy standards;19 and

 Compliance and enforcement protocols.

Congress emphasized that the test methods, measurement metrics, standards, and 

compliance and enforcement protocols must all be appropriate, cost-effective, and 

technologically feasible for commercial medium-duty and heavy-duty on-highway

vehicles and work trucks. NHTSA notes that these criteria are different from the “four 

factors” of § 32902(f)20 that have long governed NHTSA’s setting of fuel economy

standards for passenger cars and light trucks, although many of the same factors are 

considered under each of these provisions.

 

18 The NAS study is described below, and the NHTSA study accompanies this NPRM.

19 In the context of section 32902(k), NHTSA interprets “fuel economy standards” as referring not 

specifically to miles per gallon, as in the light-duty vehicle context, but instead more broadly to account as 

accurately as possible for MD/HD fuel efficiency. While it is a metric that NHTSA considered for setting 

MD/HD fuel efficiency standards, the agency recognizes that miles per gallon may not be an appropriate 

metric given the work that MD/HD vehicles are manufactured to do. NHTSA is thus proposing alternative 

metrics. as discussed further below.

20 49 U.S.C. 32902(f) states that “When deciding maximum feasible average fuel economy under this 

section, [NHTSA] shall consider technological feasibility, economic practicability, the effect of other motor 

vehicle standards of the Government on fuel economy, and the need of the United States to conserve 

energy.”
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Congress also stated that NHTSA may set separate standards for different classes 

of HD vehicles, which the agency interprets broadly to allow regulation of HD engines in 

addition to HD vehicles, and provided requirements new to section 32902 in terms of 

timing of regulations, stating that the standards adopted as a result of the agency’s 

rulemaking shall provide not less than four full model years of regulatory lead time, and 

three full model years of regulatory stability.

(3) National Academy of Sciences Report on Heavy-duty Technology 

As mandated by Congress in EISA, the National Research Council (NRC) of the 

National Academy of Sciences (NAS) recently issued a report to NHTSA and to 

Congress evaluating medium-duty and heavy-duty truck fuel efficiency improvement 

opportunities, titled “Technologies and Approaches to Reducing the Fuel Consumption of 

Medium- and Heavy-duty Vehicles.”

21 This study covers the same universe of heavyduty vehicles that is the focus of this proposed rulemaking – all highway vehicles that are 

not light-duty, MDPVs, or motorcycles. The agencies have carefully evaluated the 

research supporting this report and its conclusions and have incorporated them to the 

extent practicable in the development of this rulemaking. NHTSA’s and EPA’s detailed 

assessments of each of the relevant elements of the NAS report are discussed in section X 

of this preamble and in the NHTSA HD study accompanying this NPRM.

(4) The Recent NHTSA and EPA Light-duty National GHG Program

On April 1, 2010, EPA and NHTSA finalized the first-ever National Program for 

light-duty cars and trucks, which set GHG and fuel economy standards for model years 

2012-2016. The agencies have used the light-duty National Program as a model for this 

proposed HD National Program in many respects. This is most apparent in the case of 

heavy-duty pickups and vans, which are very similar to the light-duty trucks addressed in 

the light-duty National Program both technologically as well as in terms of how they are 

manufactured (i.e., the same company often makes both the vehicle and the engine). For 

these vehicles, there are close parallels to the light-duty program in how the agencies 

have developed our respective proposed standards and compliance structures, although in 

this proposal each agency proposes standards based on attributes other than vehicle 

footprint, as discussed below.

Due to the diversity of the remaining HD vehicles, there are fewer parallels with 

the structure of the light-duty program. However, the agencies have maintained the same 

collaboration and coordination that characterized the development of the light-duty 

program. Most notably, as with the light-duty program, manufacturers will be able to 

 

21 National Academy of Science, Committee to Assess Fuel Economy Technologies for Medium- and 

Heavy-Duty Vehicles, “Technologies and Approaches to Reducing the Fuel Consumption of Medium- and 

Heavy-Duty Vehicles,” March 2010 (hereafter, “March 2010 NAS Report” or “NAS Report”). Available 

at http://www.nap.edu/catalog.php?record_id=12845 (last accessed August 5, 2010).
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design and build to meet a closely coordinated federal program, and avoid unnecessarily 

duplicative testing and compliance burdens. 

(5) EPA’s SmartWay Program

EPA’s voluntary SmartWay Partnership program encourages shipping and 

trucking companies to take actions that reduce fuel consumption and CO2 by working 

with the shipping community and the freight sector to identify low carbon strategies and 

technologies, and by providing technical information, financial incentives, and partner 

recognition to accelerate the adoption of theses strategies. Through the SmartWay

program, EPA has worked closely with truck manufacturers and truck fleets to develop 

test procedures to evaluate vehicle and component performance in reducing fuel 

consumption and has conducted testing and has established test programs to verify

technologies that can achieve these reductions. Over the last six years, EPA has 

developed hands-on experience testing the largest heavy-duty trucks and evaluating 

improvements in tire and vehicle aerodynamic performance. In 2010, according to 

vehicle manufacturers, approximately 5 percent of new combination heavy-duty trucks 

will meet the SmartWay performance criteria demonstrating that they represent the 

pinnacle of current heavy-duty truck reductions in fuel consumption. 

In developing this HD National Program, the agencies have drawn from the 

SmartWay experience, as discussed in detail both in Sections II and III below (e.g., 

developing test procedures to evaluate trucks and truck components) but also in the Draft 

RIA (estimating performance levels from the application of the best available 

technologies identified in the SmartWay program). These technologies provide part of 

the basis for the GHG emission and fuel consumption standards proposed in this 

rulemaking for certain types of new heavy-duty Class 7 and 8 combination tractors. 

In addition to identifying technologies, the SmartWay program includes 

operational approaches that truck fleet owners as well as individual drivers and their 

freight customers can incorporate that the NHTSA and EPA believe will complement the 

proposed standards. These include such approaches as improved logistics and driver 

training, as discussed in the DRIA. This approach is consistent with the one of the three 

alternative approaches that the NAS recommended be considered. The three approaches 

were raising fuel taxes, liberalizing truck size and weight restrictions, and encouraging 

incentives to disseminate information to inform truck drivers about the relationship 

between driving behavior and fuel savings. Taxes and truck size and weight limits are 

mandated by public law; as such, are outside EPA's and NHTSA's authority to 

implement. However, complementary operational measures like driver training, which 

SmartWay does promote, can complement the proposed standards and also provide 

benefits for the existing truck fleet, furthering the public policy objectives of addressing 

energy security and climate change.

(6) Canada’s Department of the Environment

The Government of Canada’s Department of the Environment (Environment 

Canada) assisted EPA’s development of this Proposed Rulemaking, by conducting 
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emissions testing of heavy-duty vehicles at Environment Canada test facilities to gather 

data on a range of possible test cycles.

We expect the technical collaboration with Environment Canada to continue as 

we address issues raised by stakeholders in response to this NPRM, and as we continue to 

develop details of certain testing and compliance verification procedures. We may also 

be able to begin to develop a knowledge base enabling improvement upon this regulatory

framework for model years beyond 2018 (for example, improvements to the means of 

demonstrating compliance). We also expect to continue our collaboration with 

Environment Canada on compliance issues.

C. Summary of the Proposed EPA and NHTSA HD National Program

When EPA first addressed emissions from heavy-duty trucks in the 1980s, it 

established standards for engines, based on the amount of work performed (grams of 

pollutant per unit of work (brake horsepower-hour), or g/bhp-hr). This approach 

recognized the fact that engine characteristics are the dominant determinant of the types 

of emissions generated, and engine-based technologies (including exhaust aftertreatment 

systems) need to be the focus for addressing those emissions. Vehicle-based 

technologies, in contrast, have less influence on overall truck emissions of the pollutants 

that EPA has regulated in the past. The engine testing approach also recognized the 

relatively small number of distinct heavy-duty engine designs, as compared to the 

extremely wide range of truck designs. EPA concluded at that time that any incremental 

gain in conventional emission control that could be achieved through regulation of the 

complete vehicle would be small in comparison to the cost of addressing the many 

variants of complete trucks that make up the heavy-duty sector – smaller and larger 

vocational trucks for dozens of purposes, various designs of combination tractors, and 

many others.

Addressing GHG emissions and fuel consumption from heavy-duty trucks, 

however, requires a different approach. Reducing GHG emissions and fuel consumption 

requires increasing the inherent efficiency of the engine as well as making changes to the 

vehicles to reduce the amount of work that the engine needs to do per mile traveled. This 

thus requires a focus on the entire vehicle. For example, in addition to the basic 

emissions and fuel consumption levels of the engine, the aerodynamics of the vehicle can 

have a major impact on the amount of work that must be performed to transport freight at 

common highway speeds. The March 2010 NAS Report recognized this need and 

recommended a complete-vehicle approach to regulation. As described elsewhere in this 

preamble, the proposed standards that make up the HD National Program aim to address 

the complete vehicle, to the extent practicable and appropriate under the agencies’ 

respective statutory authorities, through complementary engine and vehicle standards, in 

order to reduce the complexity of the regulatory system and achieve the greatest gains as 

soon as possible. 
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(1) Brief Overview of the Heavy-duty Truck Industry

The heavy-duty truck sector spans a wide range of vehicles with often unique 

form and function. A primary indicator of the extreme diversity among heavy-duty 

trucks is the range of load-carrying capability across the industry. The heavy-duty truck 

sector is often subdivided by vehicle weight classifications, as defined by the vehicle’s 

gross vehicle weight rating, or GVWR, which is a measure of the combined curb (empty) 

weight and cargo carrying capacity of the truck. Table I-1 below outlines the vehicle 

weight classifications commonly used for many years for a variety of purposes by several 

federal agencies, including the Department of Transportation, the Department of 

Commerce, and the Internal Revenue Service.

Table I-1 Vehicle Weight Classification

Class 2b 3 4 5 6 7 8

GVWR 

(lb.)

8,501 -

10,000

10,001-

14,000

14,001-

16,000

16,001-

19,500

19,501 -

26,000

26,001-

33,000

> 

33,001

In the framework of these vehicle weight classifications, the heavy-duty truck 

sector refers to Class 2b through Class 8 vehicles and the engines that power those 

vehicles.22 Unlike light-duty vehicles, which are primarily used for transporting 

passengers for personal travel, heavy-duty vehicles fill much more diverse operator 

needs. Heavy-duty pickup trucks and vans (Classes 2b and 3) are used chiefly as work 

truck and vans, and as shuttle vans, as well as for personal transportation, with an average 

annual mileage in the range of 15,000 miles. The rest of the heavy-duty sector is used for 

carrying cargo and/or performing specialized tasks. Commercial “vocational” trucks, 

which may span Classes 2b through 8, vary widely in size, including smaller and larger 

van trucks, utility “bucket” trucks, tank trucks, refuse trucks, urban and over-the-road 

buses, fire trucks, flat-bed trucks, and dump trucks, among others. The annual mileage of 

these trucks is as varied as their uses, but for the most part tends to fall in between heavyduty pickups/vans and the large combination trucks, typically from 15,000 to 150,000 

miles per year, although some travel more and some less. Class 7 and 8 combination 

tractor-trailers – some equipped with sleeper cabs and some not -- are primarily used for 

freight transportation. They are sold as tractors and sometimes run without a trailer in 

between loads, but most of the time they run with one or more trailers that can carry up to 

50,000 pounds or more of payload, consuming significant quantities of fuel and 

producing significant amounts of GHG emissions. The combination tractor/trailers used 

in combination applications can travel more than 150,000 miles per year.

EPA and NHTSA have designed our respective proposed standards in careful 

consideration of the diversity and complexity of the heavy-duty truck industry, as 

discussed next. 

 

22 Class 2b vehicles designed as passenger vehicles (Medium Duty Passenger Vehicles, MDPVs) are 

covered by the light-duty GHG and fuel economy standards and not addressed in this rulemaking.
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(2) Summary of Proposed EPA GHG Emission Standards and 

NHTSA Fuel Consumption Standards

As described above, NHTSA and EPA recognize the importance of addressing the 

entire vehicle in reducing fuel consumption and GHG emissions. At the same time, the 

agencies understand that the complexity of the industry means that we will need to use 

different approaches to achieve this goal, depending on the characteristics of each general 

type of truck. We are therefore proposing to divide the industry into three discrete 

regulatory categories for purposes of setting our respective standards – combination 

tractors, heavy-duty pickups and vans, and vocational trucks -- based on the relative 

degree of homogeneity among trucks within each category. For each regulatory category, 

the agencies are proposing related but distinct program approaches reflecting the specific 

challenges that we see for manufacturers in these segments. In the following paragraphs, 

we discuss EPA’s proposed GHG emission standards and NHTSA’s proposed fuel 

consumption standards for the three regulatory categories of heavy-duty vehicles and 

their engines. 

The agencies are proposing test metrics that express fuel consumption and GHG 

emissions relative to the most important measures of heavy-duty truck utility for each 

segment, consistent with the recommendation of the March 2010 NAS Report that 

metrics should reflect and account for the work performed by various types of HD 

vehicles. Specifically, for heavy-duty pickup trucks and vans, EPA and NHTSA are 

proposing standards on a per-mile basis (g/mile for the EPA standards, gallons/100 miles 

for the NHTSA standards), as explained in Section I.C(2)(a) below. For heavy-duty 

trucks, both combination and vocational, the agencies are proposing standards expressed 

in terms of the key measure of freight movement tons of payload miles or, more simply, 

ton-miles. Hence, for EPA the proposed standards are in the form of the mass of 

emissions from carrying a ton of cargo over a distance of one mile (g/ton-mi)). Similarly, 

the proposed NHTSA standards are in terms of fuel consumed over a set distance (one 

thousand miles), or gal/1000 ton-mile. Finally, for engines, EPA is proposing standards 

in the form of grams of emissions per unit of work (grams per brake-horsepower-hour, or 

g/bhp-hr), the same metric used for non-GHG heavy-duty engine standards today. 

Similarly, NHTSA is proposing standards for heavy-duty engines in the form of fuel 

consumption (in gallons) per 100 units of work (gal/100 bhp-hr).

Section II below discusses the proposed EPA and NHTSA standards in greater 

detail.

(a) Class 7 and 8 Combination Tractors

Class 7 and 8 combination tractors and their engines contribute the largest portion

of the total GHG emissions and fuel consumption of the heavy duty sector, approximately

65%, of today’s GHG emissions and XX% of today’s fuel consumption, due to their large

payloads, their high annual miles traveled, and their major role in national freight 
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transport. 23 These vehicles consist of a cab and engine (tractor or combination tractor) 

and a detachable trailer. In general, reducing GHGs and fuel consumption for these 

vehicles would involve improvements such as aerodynamics and tires and reduction in 

idle operation, as well as engine-based efficiency improvements. 

In general, the heavy-duty combination tractor industry consists of tractor 

manufacturers (which manufacture the tractor and purchase and install the engine) and 

trailer manufacturers. These manufacturers are usually separate from each other. Thus, 

we are not aware of any manufacturer that typically assembles both the finished truck and 

the trailer and introduces the combination into commerce for sale to a buyer, as the 

owners of trucks and trailers are often distinct. A typical truck buyer will purchase only 

the tractor. The trailers are usually purchased and owned by fleets and shippers. This 

occurs in part because trucking fleets on average maintain 3 trailers per tractor and in 

come cases as many as 6 or more trailers per tractor. There are also large differences in 

the kinds of manufacturers involved with producing tractors and trailers. For HD 

highway tractors and their engines, a relatively limited number of manufacturers produce 

the vast majority of them. The trailer manufacturing industry is quite different, and 

includes a large number of companies, many of which are relatively small in size and 

production volume. Setting standards for the products involved -- tractors and trailers --

requires recognition of the large differences between these manufacturing industries, 

which can then warrant consideration of different regulatory approaches. 

Based on these industry characteristics, EPA and NHTSA believe that the most 

straightforward regulatory approach for combination tractors and trailers is to establish 

standards for tractors separately from trailers. As discussed below in Section IX, the 

agencies are proposing standards for the tractors and their engines in this rulemaking, but 

are not proposing standards for trailers in this rulemaking. The agencies are requesting 

comment on potential standards for trailers, but will address standards for trailers in a 

separate rulemaking.

As with the other regulatory categories of heavy-duty vehicles, EPA and NHTSA

have concluded that achieving reductions in GHG emissions and fuel consumption from 

combination tractors requires addressing both the cab and the engine, and EPA and 

NHTSA each are proposing standards that reflect this conclusion. The importance of the 

cab is that its design determines the amount of power that the engine must produce in 

moving the truck down the road. As illustrated in Figure I-1, the loads that require 

additional power from the engine include air resistance (aerodynamics), tire rolling 

resistance, and parasitic losses (including accessory loads and friction in the drivetrain). 

The importance of the engine design is that it determines the basic GHG emissions and 

fuel consumption performance of the engine for the variety of demands placed on the 

engine, regardless of the characteristics of the cab in which it is installed. The agencies 

 

23 The vast majority of combination tractor-trailers is used in highway applications, and these vehicles are 

the focus of this proposed program. A small fraction of combination trucks are used in off-road 

applications and are treated differently, as describe in Section II. 
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intend for the proposed standards to result in the application of improved technologies for 

lower GHG emissions and fuel consumption for both the cab and the engine.

Figure I-1: Combination Tractor and Trailer Loads24

Accordingly, for Class 7 and 8 combination tractors, the agencies are each 

proposing two sets of standards. For vehicle-related emissions and fuel consumption, the 

agencies are proposing that tractor manufacturers meet respective vehicle-based 

standards. Compliance with the vehicle standard would typically be determined based on 

a vehicle simulation model, called [TEST], which is consistent with the NAS Report 

recommendations to require compliance testing for combination tractors using vehicle 

simulation rather than chassis dynamometer testing. This compliance model was 

developed by EPA specifically for this rulemaking. It is an accurate and cost-effective 

alternative to measuring emissions and fuel consumption while operating the vehicle on a 

chassis dynamometer. Instead of using a chassis dynamometer as an indirect way to 

evaluate real-world operation and performance, various characteristics of the vehicle are 

measured and these measurements are used as inputs to the model. These characteristics 

relate to key technologies appropriate for this subcategory of truck – including 

aerodynamic features, weight reductions, tire rolling resistance, the presence of idlereducing technology, and vehicle speed limiters. The model would also assume the use 

of a representative typical engine, rather than a vehicle-specific engine, because engines 

are regulated separately and include an averaging, banking, and trading program separate 

from the vehicle program. The model and appropriate inputs would be used to quantify

the overall performance of the vehicle in terms of CO2 emissions and fuel consumption. 

The model’s development and design, as well as the sources for inputs and the evaluation 

of the model’s accuracy, are discussed in detail in Section II below and in the draft RIA. 

 

24 Adapted from Figure 4.1 Class 8 Truck Energy Audit, Technology Roadmap for the 21st Century Truck 

Program: A Government-Industry Research Partnership, 21CT-001, December, 2000
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EPA and NHTSA also considered developing respective alternative standards 

based on the direct testing of the emissions and fuel consumption of the entire vehicle for 

this subcategory of vehicles, as measured using a chassis test procedure. This would be 

similar to the proposed approach for standards for HD pickups and vans discussed below. 

The agencies believe that such an approach warrants continued consideration. However, 

the agencies are not prepared to propose chassis-test-based standards at this time, 

primarily because of the very small number of chassis-test facilities that currently exist, 

but rather are proposing only the tractor standards and the engine-based standards 

discussed above. The agencies seek comment on the potential benefits and trade-offs of 

chassis-test-based standards for combination tractors. 

(i) Proposed Standards for Class 7 and 8 Combination Tractors

The vehicle standards that EPA and NHTSA are proposing for Class 7 and 8 

combination tractor manufacturers are based on several key attributes related to GHG 

emissions and fuel consumption that we believe reasonably represent the many

differences in utility among these vehicles. The proposed standards differ depending on 

GVWR (i.e., whether the truck is Class 7 or Class 8), the height of the roof of the cab, 

and whether it is a “day cab” or a “sleeper cab.” These later two attributes are important 

because the height of the roof, designed to correspond to the height of the trailer, 

significantly affects air resistance, and a sleeper cab generally corresponds to the 

opportunity for idle emission and fuel consumption improvements. 

Thus, the agencies have created nine subcategories within the Class 7 and 8 

combination tractor category based on the differences in expected emissions and fuel 

consumption associated with the key attributes of GVWR, cab type, and roof 

height. Table I-2 presents the agencies’ respective proposed standards for combination 

tractor manufacturers for the 2017 model year for illustration. 

Table I-2: Heavy-duty Combination Tractor EPA Emissions Standards (g CO2/ton-mile) and 

NHTSA Fuel Consumption Standards (gal/1000 ton-mile)

2017 Model Year CO2 Grams per Ton-Mile

Day Cab Sleeper Cab

Class 7 Class 8 Class 8

Low Roof 106 80 65

Mid Roof 106 80 65

High Roof 120 88 72

2017 Model Year Gallons of Fuel per 1000 Ton-Mile

Day Cab Sleeper Cab

Class 7 Class 8 Class 8

Low Roof 10.4 7.9 6.4

Mid Roof 10.4 7.9 6.4

High Roof 11.8 8.6 7.1

In addition, the agencies are proposing separate performance standards for the 

engines manufactured for use in these trucks. EPA’s proposed engine-based CO2
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standards and NHTSA’s proposed engine-based fuel consumption standards would vary

based on the expected weight class and usage of the truck into which the engine would be 

installed. EPA is also proposing engine-based N2O and CH4 standards for manufacturers 

of the engines used in combination tractors. EPA is proposing separate engine-based 

standards for these GHGs because the agency believes that N2O and CH4 emissions are 

technologically related solely to the engine, fuel, and emissions aftertreatment systems, 

and the agency is not aware of any influence of vehicle-based technologies on these 

emissions. EPA expects that manufacturers of current engine technologies would be able 

to comply with the proposed “cap” standards with little or no technological 

improvements; the value of the standards would be to prevent significant increases in 

these emissions as alternative technologies are developed and introduced in the future. 

Compliance with the proposed EPA engine-based CO2 standards and the proposed 

NHTSA fuel consumption standards, as well as the proposed EPA N2O and CH4

standards, would be determined using the appropriate EPA engine test procedure, as 

discussed in Section II below. 

As with the other subcategories of heavy-duty vehicles, EPA and NHTSA are 

proposing respective standards that would apply to Class 7 and 8 trucks both at the time 

of production (as in Table I-2, above). In addition, EPA is proposing separate standards 

that would apply for a specified period of time in use. All of the proposed standards for 

these trucks, as well as details about the proposed provisions for certification and 

implementation of these standards, are discussed in more detail in Sections II, III, IV, and 

V below and in the draft RIA.

(ii) EPA Proposed Air Conditioning Leakage Standard for Class 7 and 8 

Combination Tractors

In addition to the proposed EPA tractor- and engine-based standards for CO2 and 

engine-based standards for N2O, and CH4 emissions, EPA is also proposing a separate 

standard to reduce leakage of HFC refrigerant from cabin air conditioning (A/C) systems 

from combination tractors, to apply to the tractor manufacturer. This standard would be 

independent of the CO2 tractor standard, as discussed below. Because the current 

refrigerant used widely in all these systems has a very high global warming potential 

(GWP), EPA is concerned about leakage of refrigerant over time.25 

Because the interior volume to be cooled of most of these truck cabins is similar 

to that of light-duty trucks, the size and design of current truck A/C systems is also very 

similar. The proposed compliance approach for Class 7 and 8 trucks is therefore similar 

to that in the light-duty rule in that these proposed standards are design-based. 

Manufacturers would choose technologies from a menu of leak-reducing technologies 

sufficient to comply with the standard, as opposed to using a test to measure 

performance. 

 

25 The global warming potential (GWP) for HFC-134a refrigerant of 1430 used in this proposal is

consistent with the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4).
26 of 541

However, the proposed heavy-duty A/C provisions differ in two important ways 

from those established in the light-duty rule. First, the light-duty provisions were 

established as voluntary ways to generate credits towards the CO2 g/mi standard, and 

EPA took into account the expected use of such credits in establishing the CO2 emissions 

standards. In this rule, EPA is proposing that manufacturers actually meet a standard – as 

opposed to having the opportunity to earn a credit -- for A/C refrigerant leakage. Thus, 

for this rule, refrigerant leakage is not accounted for in the development of the proposed 

CO2 standards. We are taking this approach here recognizing that while the per A/C 

system benefits of leakage control are almost identical between light-duty and heavy-duty 

vehicles, the credits based on per mile benefits are much smaller for heavy-duty vehicles 

due to their much higher CO2 emissions rates and higher annual mileage when compared 

to light duty vehicles. Hence a credit based approach as done for light-duty would 

provide almost no motivation for manufacturers to install low leakage systems even 

though such systems represent a highly cost effective means to control GHG emissions. 

The second difference relates the expression of the leakage rate. The light-duty A/C 

leakage standard is expressed in terms of grams per year. For this heavy-duty rule, 

however, because of the wide variety of system designs and arrangements, a one-sizefits-all gram per year standard would likely be much less relevant, so EPA believes it is 

more appropriate to propose a standard in terms of percent of total refrigerant leakage per 

year, This requires the total refrigerant capacity of the A/C system to be taken into 

account in determining compliance. EPA believes that this proposed approach -- a 

standard instead of a credit, and basing the standard on percent leakage over time – is 

more appropriate for heavy-duty tractors than the light-duty approach and that it will 

achieve the desired reductions in refrigerant leakage. Compliance with the standard 

would be determined through a showing by the tractor manufacturer that its A/C system 

incorporated a combination of low-leak technologies sufficient to meet the percent 

leakage of the standard. This proposed “menu” of technologies is very similar to that 

established in the light-duty GHG rule.26 

Finally, EPA is not proposing an A/C system efficiency standard in this heavyduty rulemaking, although an efficiency credit was a part of the light-duty rule. The 

much larger emissions of CO2 from a heavy-duty tractor as compared to those from a 

light duty vehicle mean that the relative amount of CO2 that could be reduced through 

A/C efficiency improvements is very small. We request comment on this decision and 

whether EPA should reflect A/C system efficiency in the final program either as a credit 

or a stand alone standard based on the same technologies and performance levels as the 

light-duty program.

A more detailed discussion of A/C related issues is found in Section II of this 

preamble. 

 

26 At this time, EPA is considering approval of an alternative refrigerant, HFO-1234yf, which has a very 

low GWP. The proposed A/C leakage standard is designed to account for use of an alternative, low-GWP 

refrigerant. If in the future this refrigerant is approved and if it becomes widespread as a substitute for 

HFC-134a in mobile A/C systems, EPA may propose to revise or eliminate the leakage standard. 
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(b) Heavy-Duty Pickup Trucks and Vans (Class 2b and 3)

Heavy-duty vehicles with GVWR between 8,501 and 10,000 lb are classified in 

the industry as Class 2b motor vehicles per the FMCSA definition. As discussed above, 

Class 2b includes medium-duty passenger vehicles (MDPVs) that are regulated by the 

agencies under the light-duty vehicle program, and the agencies are not considering 

additional requirements for MDPVs in this rulemaking. Heavy-duty vehicles with 

GVWR between 10,001 and 14,000 lb are classified as Class 3 motor vehicles. Class 2b 

and Class 3 heavy-duty vehicles (referred to in this proposal as “HD pickups and vans”) 

together emit about 20% of today’s GHG emissions from the heavy-duty vehicle sector. 

About 90 percent of HD pickups and vans are 3⁄4-ton and 1-ton pick-up trucks, 12-

and 15-passenger vans, and large work vans that are sold by the original equipment 

manufacturers (OEMs) as complete vehicles, with no secondary manufacturer making 

substantial modifications prior to registration and use. These OEMs are companies with 

major light-duty markets in the U.S., primarily Ford, General Motors, and Chrysler. 

Furthermore, the technologies available to reduce fuel consumption and GHG emissions 

from this segment are similar to the technologies used on light-duty pickup trucks, 

including both engine efficiency improvements (for gasoline and diesel engines) and 

vehicle efficiency improvements. 

For these reasons, EPA believes it is appropriate to propose GHG standards for 

HD pickups and vans based on the whole vehicle, including the engine, expressed as 

grams per mile, consistent with the way these vehicles are regulated by EPA today for 

criteria pollutants. NHTSA believes it is appropriate to propose corresponding gallons 

per 100 mile fuel consumption standards that are likewise base on the whole vehicle. 

This complete vehicle approach being proposed by both agencies for HD pickups and 

vans is consistent with the recommendations of the NAS Committee in their March 2010 

Report. EPA and NHTSA also believe that the structure and many of the detailed 

provisions of the recently finalized light-duty GHG and fuel economy program, which 

also involves vehicle-based standards, are appropriate for the HD pickup and van GHG 

and fuel consumption standards as well, and this is reflected in the standards each agency

is proposing, as detailed in section II. These proposed commonalities include a new 

vehicle fleet average standard for each manufacturer in each model year and the 

determination of these fleet average standards based on production volume-weighted 

targets for each model, with the targets varying based on a defined vehicle attribute. 

Vehicle testing would be conducted on chassis dynamometers using the drive cycles from 

the EPA Federal Test Procedure (FTP or ‘‘city’’ test) and Highway Fuel Economy Test

(HFET or ‘‘highway’’ test).

For the light-duty GHG and fuel economy standards, the agencies factored in 

vehicle size by basing the emissions and fuel economy targets on vehicle footprint (the 

wheelbase times the average track width).27 For those standards, passenger cars and light 

 

27 EISA requires CAFE standards for passenger cars and light trucks to be attribute-based; see 49 U.S.C. 

32902(b)(3)(A).
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trucks with larger footprints are assigned higher GHG and lower fuel economy target 

levels in acknowledgement of their inherent tendency to consume more fuel and emit 

more GHGs per mile. For HD pickups and vans, the agencies believe that setting 

standards based on vehicle attributes is appropriate, but feel that a weight-based metric 

provides a better attribute than the footprint attribute utilized in the light-duty vehicle 

rulemaking. Weight-based measures such as payload and towing capability are key

among the things that characterize differences in the design of these vehicles, as well as 

differences in how the vehicles will be utilized. Buyers consider these utility-based 

attributes when purchasing a heavy-duty pick-up or van. EPA and NHTSA are therefore 

proposing standards for HD pickups and vans based on a “work factor” that combines 

their payload and towing capabilities, with an added adjustment for 4-wheel drive 

vehicles. 

The agencies are proposing that each manufacturer’s fleet average standard would 

be based on production volume-weighting of target standards for each vehicle that in turn 

are based on the vehicle’s work factor. These target standards would be taken from a set 

of curves (mathematical functions), presented in Section II.C. EPA is also proposing that 

the CO2 standards be phased in gradually starting in the 2014 model year, at 15-20-40-

60-100 percent in model years 2014-2015-2016-2017-2018, respectively. The phase-in 

would take the form of a set of target standard curves, with increasing stringency in each 

model year, as detailed in Section II.C. The EPA standards proposed for 2018 (including 

a separate standard to control air conditioning system leakage) represent an average pervehicle reduction in GHGs of 17 percent for diesel vehicles and 12 percent for gasoline 

vehicles, compared to a common baseline, as described in Sections II and III of this 

preamble. Section II also discusses the rationale behind the proposal of separate targets 

for diesel and gasoline vehicle standards. EPA is also proposing a manufacturer’s 

alternative implementation schedule for model years 2016-2018 that parallels and is 

equivalent to NHTSA’s first alternative described below.

NHTSA is proposing to allow manufacturers to select one of two fuel 

consumption standard alternatives for model years 2016-2018. To meet the EISA 

statutory requirement for three year regulatory stability, the first alternative would define 

individual gasoline vehicle and diesel vehicle fuel consumption target curves that would 

not change over model years 2016 to 2018. The proposed target curves for this alternative 

are presented in Section II. The second alternative would use target curves that are 

equivalent to the EPA program in each model year 2016 to 2018. Stringency for the 

alternatives has been selected to allow a manufacturer, through the use of the credit and 

deficit carry-forward provisions that the agencies are also proposing, to rely on the same 

product plans to satisfy either alternative, and also EPA requirements. NHTSA is also 

proposing that manufacturers may voluntarily opt into the NHTSA HD pickup and van 

program in model years 2014 or 2015. For these model years, NHTSA’s fuel 

consumption target curves are equivalent to EPA’s target curves.

 
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The proposed EPA and NHTSA standard curves are based on a set of vehicle, 

engine, and transmission technologies expected to be used to meet the recently

established GHG and fuel economy standards for model year 2012-2016 light-duty 

vehicles, with full consideration of how these technologies would perform in heavy-duty 

vehicle testing and use. All of these technologies are already in use or have been 

announced for upcoming model years in some light-duty vehicle models, and some are in 

use in a portion of HD pickups and vans as well. The technologies include:

 advanced 8-speed automatic transmissions

 aerodynamic improvements

 electro-hydraulic power steering

 engine friction reductions

 improved accessories

 low friction lubricants in powertrain components

 lower rolling resistance tires

 lightweighting

 gasoline direct injection

 gasoline engine coupled cam phasing

 diesel aftertreatment optimization

 air conditioning system leakage reduction (for EPA program only)

See Section III.xx for a detailed analysis of these and other potential technologies, 

including their feasibility, costs, and effectiveness when employed for reducing fuel 

consumption and CO2 emissions in HD pickups and vans.

A relatively small number of HD pickups and vans are sold by OEMs as 

incomplete vehicles, without the primary load-carrying device or container attached. We 

are proposing that these vehicles generally be regulated as Class 2b through 8 vocational 

trucks, as described in Section I.C(2)(c), because, like other vocational trucks, we have 

little information on baseline aerodynamic performance and expectations for 

improvement. However, a sizeable subset of these incomplete vehicles, often called cabchassis vehicles, are sold by the OEMs in configurations with many of the components 

that affect GHGs and fuel consumption identical to those on complete pickup truck or 

van counterparts — including engines, cabs, frames, transmissions, axles, and wheels. 

We are proposing that these vehicles be included in the chassis-based HD pickup and van 

program. Similarly, some Class 4 complete vehicles are very similar to complete Class 3 

vehicle models, including overall vehicle architecture and use of the same basic engines, 

and we are proposing that these Class 4 vehicles be included in the chassis-based HD 

pickup and van program as well. These proposed provisions are described in Section V.E.

In addition to proposed EPA CO2 emission standards and the proposed NHTSA 

fuel consumption standards for HD pickups and vans, EPA is also proposing standards 

for two additional GHGs, N2O and CH4, as well as standards for air conditioning-related 

HFC emissions. These standards are discussed in more detail in Sections II.xx and II.xx. 
30 of 541

Finally, EPA is proposing standards that would apply to HD pickups and vans in use. All 

of the proposed standards for these HD pickups and vans, as well as details about the 

proposed provisions for certification and implementation of these standards, are 

discussed in Sections II.C.

(c) Class 2b-8 Vocational Trucks

Class 2b-8 vocational trucks consist of a wide variety of truck types. Some of the 

primary applications for trucks in this segment include delivery, refuse, utility, dump, and 

cement trucks; transit, shuttle, and school buses; emergency vehicles, motor homes,28 tow 

trucks, among others. These trucks and their engines contribute approximately 15% of 

today’s heavy-duty truck sector GHG emissions. 

Manufacturing of trucks in this segment of the industry is organized in a more 

complex way than that of the other heavy-duty subcategories. Class 2b-8 vocational 

trucks are often built as a chassis with an installed engine and an installed transmission. 

Both the engine and transmissions are typically manufactured by other manufacturers and 

the chassis manufacturer purchases and installs them. Many of the same companies that 

build Class 7 and 8 tractors are also in the Class 2b-8 chassis manufacturing market. The 

chassis is typically then sent to a body manufacturer, which completes the vehicle by

installing the appropriate feature -- such as dump bed, delivery box, or utility bucket --

onto the chassis. Truck body manufacturers tend to be small businesses that specialize in 

specific types of bodies or specialized features. 

EPA and NHTSA are proposing that in this vocational truck subcategory the 

chassis manufacturers be the focus of the proposed GHG and fuel consumption standards. 

They play a central role in the manufacturing process, and the product they produce – the 

chassis with engine and transmissions – includes the primary technologies that affect 

emissions and fuel consumption. They also constitute a much more limited group of 

manufacturers for purposes of developing a regulatory program. In contrast, a focus on 

the body manufacturers would be much less practical, since they represent a much more 

diverse set of manufacturers, and the part of the vehicle that they add has a very limited 

impact on opportunities to reduce GHG emissions and fuel consumption (given the 

limited role that aerodynamics plays in the types of lower speed operation typically found 

with vocational trucks.) Therefore, the proposed standards in this vocational truck 

category would apply to the chassis manufacturers of all heavy-duty vehicles not 

otherwise covered by the HD pickup and van standards or Class 7 and 8 combination 

tractor standards discussed above. The agencies request comment on our proposed focus 

on chassis manufacturers.

As discussed above, EPA and NHTSA have concluded that reductions in GHG 

emissions and fuel consumption require addressing both the vehicle and the engine. As 

discussed above for Class 7 and 8 combination tractors, the agencies are each proposing 

 

28 Again, we note that NHTSA’s proposed fuel consumption standards would not apply to non-commercial 

vehicles like motor homes.
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two sets of standards for Class 2b-8 vocational trucks. For vehicle-related emissions, the 

agencies are proposing standards for chassis manufacturers: EPA CO2 (g/ton-mile) 

standards and NHTSA fuel consumption (gal/1000 ton-mile) standards). Also as in the 

case of Class 7 and 8 tractors, we propose to use the [TEST] vehicle simulation model to 

determine compliance with the vocational truck standards. The primary manufacturergenerated input into the proposed compliance model for this category of trucks would be 

a measure of tire rolling resistance, as discussed further below, because tire 

improvements are the primary means of vehicle improvement available at this time.. The 

model would also assume the use of a typical representative engine in the simulation, 

resulting in an overall value for CO2 emissions and one for fuel consumption. As is the 

case for combination tractors, the manufacturers of the engines intended for vocational 

trucks would be subject to separate engine-based standards.

(i) Proposed Standards for Class 2b-8 Vocational Trucks

Based on our analysis and research, the agencies believe that the primary

opportunity for reductions in vocational truck GHG emissions and fuel consumption will 

be through improved engine technologies and improved tire rolling resistance. For 

engines, as proposed for combination tractors, EPA and NHTSA are proposing separate 

standards for the manufacturers of engines used in Class 2b-8 vocational trucks. EPA’s 

proposed engine-based CO2 standards and NHTSA’s proposed engine-based fuel 

consumption standards would vary based on the expected weight class and usage of the 

truck into which the engine would be installed. The agencies propose to use the 

groupings EPA currently uses for other heavy-duty engine standards -- light heavy-duty, 

medium heavy-duty, and heavy heavy-duty, as discussed in Section II below.

Tire rolling resistance is closely related to the weight of the vehicle. Therefore, 

we propose that the vehicle-based standards for these trucks vary according to one key

attribute, GVWR. For this initial HD rulemaking, we propose that these standards be 

based on the same groupings of truck weight classes used for the engine standards -- light 

heavy-duty, medium heavy-duty, and heavy heavy-duty. These groupings are 

appropriate for the proposed vehicle-based standards because they parallel the general 

divisions among key engine characteristics, as discussed in Section II.

The agencies intend to monitor the development of and production feasibility of 

new vehicle-related GHG and fuel consumption reduction improving technologies and 

consider including these technologies in future rulemakings. As discussed below, we are 

including provisions to account for and credit the use of hybrid technology as a 

technology that can reduce emissions and fuel consumption. Hybrid technology can 

currently be a cost-effective technology in certain specific vocational applications, and 

the agencies want to recognize and promote the use of this technology. We also are 

proposing a mechanism whereby credits can be generated by use of other technologies 

not included in the compliance model. (See sections I.E and IV below.) 

Table I-3 presents EPA’s proposed CO2 standards and NHTSA’s proposed fuel 

consumption standards for chassis manufacturers of Class 2b through Class 8 vocational 

trucks for the 2017 model year for illustrative purposes. 
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Table I-3: Proposed 2017 Class 2b-8 Vocational Truck EPA CO2 Standards and NHTSA Fuel 

Consumption Standards

EPA CO2 (gram/ton-mile) Standard Effective 2017 Model Year

Light Heavy 

Class 3-5

Medium Heavy

Class 6-7

Heavy Heavy

Class 8

CO2 Emissions 404 240 100

NHTSA Fuel Consumption (gallon per 1000 ton-mile) Standard Effective 2017 Model 

Year

Light Heavy 

Class 3-5

Medium Heavy

Class 6-7

Heavy Heavy

Class 8

Fuel Consumption 39.7 23.6 9.8

At this time, NHTSA and EPA are not prepared to propose alternative standards 

based on a whole-vehicle chassis test for vocational trucks in this initial heavy-duty

rulemaking. As discussed above for combination tractors, the primary reason is the very

small number of chassis-test facilities that currently exist. Thus, the agencies are 

proposing only the compliance-model based standards and engine standards discussed 

above, and seek comment on the appropriateness of chassis-test-based standards for the 

vocational truck subcategory. 

For vocational trucks using hybrid technology, the agencies are proposing two 

specialized approaches to allow manufacturers to gain credit for the emissions and fuel 

consumption reductions associated with hybrid technology. Hybrid applications in

vocational trucks use the secondary hybrid power source as a power take-off (PTO) to 

operate secondary equipment such as a utility bucket or dump bed that would otherwise 

require the use of the truck’s engine. One option to account for the reductions associated 

with vocational trucks using hybrid technology would compare vehicle-based chassis 

tests with and without the hybrid technology. The other option would allow a 

manufacturer to simulate the operation of the hybrid system in an engine-based test. The 

options are further discussed in section IV.

The proposed program also provides for opportunities to generate credits for 

technologies not measured by the [TEST] model, again described more fully in section 

IV.

As mentioned above for Class 7 and 8 combination trucks, EPA believes that N2O 

and CH4 emissions are technologically related solely to the engine, fuel, and emissions 

aftertreatment systems, and the agency is not aware of any influence of vehicle-based 

technologies on these emissions. Therefore, for Class 2b-8 vocational trucks, EPA is not 

proposing separate vehicle-based standards for these GHGs, but is proposing enginebased N2O and CH4 standards for manufacturers of the engines to be used in vocational 

trucks. EPA expects that manufacturers of current engine technologies would be able to 

comply with the proposed “cap” standards with little or no technological improvements; 

the value of the standards would be in that they would prevent significant increases in 

these emissions as alternative technologies are developed and introduced in the future. 

Compliance with the proposed EPA engine-based CO2 standards and the proposed 
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NHTSA fuel consumption standards, as well as the proposed EPA N2O and CH4

standards, would be determined using the appropriate EPA engine test procedure, as 

discussed in Section II below. 

As with the other regulatory categories of heavy-duty vehicles, EPA and NHTSA 

are proposing standards that would apply to Class 2b-8 vocational trucks at the time of 

production, and EPA is proposing standards for a specified period of time in use. All of 

the proposed standards for these trucks, as well as details about the proposed provisions 

for certification and implementation of these standards, are discussed in more detail later 

in this notice and in the Draft RIA.

EPA is not proposing A/C refrigerant leakage standards for Class 2b-8 vocational 

trucks at this time, primarily because of the number of entities involved in their 

manufacture and thus the potential for different entities besides the chassis manufacturer 

to be involved in the A/C system production and installation. EPA requests comment on 

how A/C standards might practically be applied to manufacturers of vocational trucks. 

(d) What Manufacturers Are Not Covered by the Proposed Standards?

EPA and NHTSA are proposing to temporarily defer the proposed greenhouse gas 

emissions and fuel consumption standards for any manufacturers of heavy-duty engines, 

manufacturers of combination tractors, and manufacturers of vocational trucks that meet 

the “small business” size criteria set by the Small Business Administration (SBA). We 

are not aware of any manufacturers of HD pickups and vans that meet these criteria. For 

each of the other subcategories and for engines, we have identified a small number of 

manufacturers that would appear to meet the SBA criteria. The production of these 

companies is small, and we believe that deferring the standards for these companies at 

this time would have a negligible impact on the GHG emission reductions and fuel 

consumption reductions that the program would otherwise achieve. We request comment 

on our assumption that the impact of these exemptions for small businesses will be small 

and further whether it will be possible to circumvent the regulations by creating new 

small businesses to displace existing manufacturers. We discuss the specific deferral 

provisions in more detail in Section II.

The agencies will consider appropriate GHG emissions and fuel consumption 

standards for these entities as part of a future regulatory action. 

D. Summary of Costs and Benefits of the HD National Program

This section summarizes the projected costs and benefits of the proposed NHTSA 

fuel consumption and EPA GHG emissions standards. These projections help to inform 

the agencies’ choices among the alternatives considered and provide further confirmation 

that the proposed standards are an appropriate choice within the spectrum of choices 

allowable under the agencies’ respective statutory criteria. NHTSA and EPA have used 

common projected costs and benefits as the bases for our respective standards.
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The agencies have analyzed in detail the projected costs and benefits of the 

proposed GHG and fuel consumption standards. Table I-4 shows estimated lifetime

discounted costs, benefits and net benefits for all heavy-duty vehicles projected to be sold 

in model years 2014-2018. 

Table I-4: Estimated Lifetime Discounted Costs, Benefits, and Net Benefits for 2014-2018 Model 

Year HD Vehicles assuming the $22/ton SCC Valuea,b (2008 dollars)

3% Discount Rate $billions

Costs $8.2

Benefits $49

Net Benefits $41

7% Discount Rate

Costs $8.2

Benefits $34

Net Benefits $26

Notes:

a Although the agencies estimated the benefits associated with four different values of a 

one ton CO2 reduction (SCC: $5, $22, $36, $66), for the purposes of this overview 

presentation of estimated costs and benefits we are showing the benefits associated with 

the marginal value deemed to be central by the interagency working group on this topic: 

$22 per ton of CO2, in 2008 dollars and 2010 emissions and fuel consumption. As noted 

in Section VIII.F, SCC increases over time.

b Note that net present value of reduced GHG emissions is calculated differently from

other benefits. The same discount rate used to discount the value of damages from future 

emissions (SCC at 5, 3, and 2.5 percent) is used to calculate net present value of SCC for 

internal consistency. Refer to Section VIII.F for more detail.

Table I-5 shows the estimated lifetime reductions in CO2 emissions and fuel 

consumption for all heavy-duty vehicles sold in the model years 2014-2018. The values 

in Table I-5 are projected lifetime totals for each model year and are not discounted. The 

two agencies’ standards together comprise the HD National Program, and the agencies’ 

respective GHG emissions and fuel consumption standards, jointly, are the source of the 

benefits and costs of the HD National Program. 

Table I-5: Estimated Lifetime Reductions in Fuel Consumption and CO2 Emissions for 2014-2018 

Model Year HD Vehicles

2014 2015 2016 2017 2018 Total

All 

HeavyDuty

Vehicles

Fuel (billion gallons) 3.0 3.1 3.5 5.2 5.7 20.4

Fuel (billion barrels) 0.07 0.07 0.08 0.12 0.14 0.5

CO2 (mmt)a37.2 38.7 42.7 63.2 70.0 252

a

Includes upstream and downstream CO2 reductions.

Table I-6 shows the estimated lifetime discounted benefits for all heavy-duty

vehicles sold in model years 2014-2018. Although the agencies estimated the benefits 

associated with four different values of a one ton CO2 reduction ($5, $22, $36, $66), for 
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the purposes of this overview presentation of estimated benefits the agencies are showing

the benefits associated with one of these marginal values, $22 per ton of CO2, in 2008 

dollars and 2010 emissions. Table I-6 presents benefits based on the $22 value. Section 

VIII.F presents the four marginal values used to estimate monetized benefits of CO2

reductions and Section VIII presents the program benefits using each of the four marginal 

values, which represent only a partial accounting of total benefits due to omitted climate 

change impacts and other factors that are not readily monetized. The values in the table 

are discounted values for each model year of vehicles throughout their projected 

lifetimes. The analysis includes other economic impacts such as fuel savings, energy

security, and other externalities such as reduced accidents, congestion and noise. 

However, the analysis supporting the proposal omits other impacts such as benefits 

related to non-GHG emission reductions. The lifetime discounted benefits are shown for 

one of four different social cost of carbon (SCC) values considered by EPA and NHTSA. 

The values in Table I-6 do not include costs associated with new technology required to 

meet the GHG and fuel consumption standards. 

 

Table I-6: Estimated Lifetime Discounted Benefits for 2014-2018 Model Year HD Vehicles Assuming 

the $22/ton SCC Valuea,b (billions of 2008 dollars)

Discount Rate Model Year

2014 2015 2016 2017 2018 Total

3% $7.2 $7.4 $8.2 $12.3 $13.6 $49

7% $5.4 $5.5 $5.9 $8.5 $9.0 $34

Notes:

a The analysis includes impacts such as the economic value of reduced fuel consumption 

and accompanying climate-related economic benefits from reducing emissions of CO2

(but not other GHGs), and reductions in energy security externalities caused by U.S. 

petroleum consumption and imports. The analysis also includes economic impacts

stemming from additional heavy-duty vehicle use, such as the economic damages caused 

by accidents, congestion and noise.

b Note that net present value of reduced CO2 emissions is calculated differently from

other benefits. The same discount rate used to discount the value of damages from future 

emissions (SCC at 5, 3, and 2.5 percent) is used to calculate net present value of SCC for 

internal consistency. Refer to Section VIII.F for more detail. 

c

Table I-7 shows the agencies’ estimated lifetime fuel savings, lifetime CO2

emission reductions, and the monetized net present values of those fuel savings and CO2

emission reductions. The gallons of fuel and CO2 emission reductions are projected 

lifetime values for all vehicles sold in the model years 2014-2018. The estimated fuel 

savings in billions of barrels and the GHG reductions in million metric tons of CO2

shown in Table I-7 are totals for the five model years throughout their projected lifetime 

and are not discounted. The monetized values shown in Table I-7 are the summed values 

of the discounted monetized-fuel consumption and monetized-CO2 reductions for the five 
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model years 2014-2018 throughout their lifetimes. The monetized values in Table I-7

reflect both a 3 percent and a 7 percent discount rate as noted.
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Table I-7: Estimated Lifetime Reductions and Associated Discounted Monetized Benefits for 2014-

2018 Model Year HD Vehicles (monetized values in 2008 dollars)

Amount $ value (billions)

Fuel Consumption Reductions 0.5 billion barrels $42, 3% discount rate

$28, 7% discount rate

CO2 Emission Reductionsa 

Valued assuming $22/ton CO2 in 2010)

252 MMT CO2 $4.3b

Notes:

a

Includes both upstream and downstream CO2e emission reductions.b Note that net 

present value of reduced CO2 emissions is calculated differently form other benefits. The 

same discount rate used to discount the value of damages from future emissions (SCC at 

5, 3, and 2.5 percent) is used to calculate net present value of SCC for internal 

consistency. Refer to Section VIII.F for more detail. 

Table I-8 shows the estimated incremental and total technology outlays for all 

heavy-duty vehicles for each of the model years 2014-2018. The technology outlays

shown in Table I-8 are for the industry as a whole and do not account for fuel savings 

associated with the program.

Table I-8: Estimated Incremental Technology Outlays for 2014-2018 Model Year HD Vehicles

(billions of 2008 dollars)

2014 2015 2016 2017 2018 Total

All HeavyDuty Vehicles$1.4 $1.4 $1.6 $1.7 $2.1 $8.2

Table I-9 shows EPA’s estimated incremental cost increase of the average new 

heavy-duty vehicle for each model year 2014-2018. The values shown are incremental to 

a baseline vehicle and are not cumulative. 

Table I-9: Estimated Incremental Increase in Average Cost for 2014-2018 Model Year HD Vehicles

(2008 dollars per unit)

2014 2015 2016 2017 2018

Combination Tractors $6,828 $6,638 $6,358 $6,668 $6,403

HD Pickups &Vans $233 $302 $587 $887 $1,458

Vocational Trucks $362 $356 $389 $382 $349

E. Program Flexibilities

For each of the heavy-duty vehicle subcategories and heavy-duty engines for 

which we are proposing respective standards, EPA and NHTSA are also proposing 
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provisions designed to give manufacturers a degree of flexibility in complying with the 

standards. These proposed provisions have enabled the agencies to consider overall 

standards that are more stringent and that would become effective sooner than we could 

consider with a more rigid program, one in which all of a manufacturer’s similar vehicles 

or engines would be required to achieve the same emissions or fuel consumption levels, 

and at the same time. 29 We believe that incorporating carefully structured regulatory

flexibility provisions into the overall program is an important way to achieve each 

agency’s goals for the program. 

NHTSA’s and EPA’s proposed flexibility provisions are essentially identical to 

each other in structure and function. For combination tractor and vocational truck 

categories and for heavy-duty engines, we are proposing four primary types of flexibility

– averaging, banking, and trading (ABT) provisions, early credits, advanced technology 

credits, and innovative technology credit provisions. In addition, we are proposing 

special provisions to apply to vocational trucks that incorporate hybrid powertrain 

technologies. The proposed ABT provisions are patterned on existing EPA ABT 

programs and would allow a vehicle manufacturer to reduce CO2 emission and fuel 

consumption levels further than the level of the standard for one or more vehicles to 

generate ABT credits. The manufacturer could then use those credits to offset higher 

emission or fuel consumption levels in other similar vehicles, “bank” the credits for later 

use, or “trade” the credits to another manufacturer. We are proposing similar ABT 

provisions for manufacturers of heavy-duty engines. For HD pickups and vans, we are 

proposing a fleet averaging system very similar to the light-duty GHG and CAFE fleet 

averaging system.

To best ensure that the overall emission and fuel consumption reductions of the 

program would be achieved and to minimize any effect on the ability of the market to 

respond to consumer needs, the agencies propose to restrict the use of averaging to 

limited sets of vehicles and engines expected to have similar emission or fuel 

consumption characteristics. For example, averaging would be allowed among Class 7 

low-roof day cab vehicles, but not among those vehicles and Class 8 sleeper cabs or 

vocational vehicles. Also, we propose that credits generated by vehicles not be 

applicable to engine compliance, and vice versa. For HD pickups and vans, we propose 

that fleet averaging be allowed with minimum restriction within the HD pickup and van 

subcategory.

In addition to ABT, the agencies are proposing that a manufacturer that reduces 

CO2 emissions and fuel consumption below required levels prior to the beginning of the 

program be allowed to generate the same number of credits (“early credits”) that they

would after the program begins. 

 

29 NHTSA notes that it has greater flexibility in the HD program to include consideration of credits and 

other flexibilities in determining appropriate and feasible levels of stringency than it does in the light-duty 

CAFE program. Cf. 49 U.S.C. 32902(h), which applies to light-duty CAFE but not heavy-duty fuel 

efficiency under 32902(k).
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The agencies are also proposing that vocational truck manufacturers that show 

improvements in CO2 emissions and fuel consumptions and incorporate certain 

technologies (including hybrid powertrains, Rankine engines, or electric vehicles) be 

eligible for special “advanced technology” credits. Unlike other credits in this proposal, 

the advanced technology credits could be applied to any heavy duty vehicle or engine, 

and not be limited to the vehicle category generating the credit. 

The technologies eligible for advanced technology credits above lend themselves 

to straightforward methodologies for quantifying the emission or fuel consumption 

reductions. For other technologies which can reduce CO2 and fuel consumption, but for 

which there do not yet exist established methods for quantifying reductions, the agencies

still seek to encourage the development of such innovative technologies, and are 

therefore proposing special “innovative technology” credits. These innovative 

technology credits would apply to technologies that are shown to produce emission and 

fuel consumption reductions that are not adequately recognized on the current test 

procedures and that are not yet in widespread use. Manufacturers would need to quantify

the reductions in fuel consumption and CO2 emissions that the technology could achieve, 

above and beyond those achieved on the existing test procedures. As with ABT, we 

propose that the use of innovative technology credits be only allowed among vehicles and 

engines expected to have similar emissions and fuel consumption characteristics (e.g., 

within each of the nine Class 7 & 8 combination tractor classifications, or within each of 

the three Class 2b-8 vocational truck classifications). 

A detailed discussion of each agency’s ABT and innovative technology

provisions for each regulatory category of heavy-duty vehicles and engines is found in 

Section IV below.

F. EPA and NHTSA Statutory Authorities

(1) EPA Authority

Title II of the Clean Air Act (CAA) provides for comprehensive regulation of 

mobile sources, authorizing EPA to regulate emissions of air pollutants from all mobile 

source categories. When acting under Title II of the CAA, EPA considers such issues as 

technology effectiveness, its cost (both per vehicle, per manufacturer, and per consumer), 

the lead time necessary to implement the technology, and based on this the feasibility and 

practicability of potential standards; the impacts of potential standards on emissions 

reductions of both GHGs and non-GHGs; the impacts of standards on oil conservation 

and energy security; the impacts of standards on fuel savings by customers; the impacts 

of standards on the truck industry; other energy impacts; as well as other relevant factors 

such as impacts on safety. 

This proposal implements a specific provision from Title II, section 202(a).30 

Section 202(a)(1) of the CAA states that “the Administrator shall by regulation prescribe 

 

30 42 U.S.C. 7521 (a)
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(and from time to time revise)...standards applicable to the emission of any air pollutant 

from any class or classes of new motor vehicles ..., which in his judgment cause, or 

contribute to, air pollution which may reasonably be anticipated to endanger public health 

or welfare.” With EPA’s December 2009 final findings for greenhouse gases, section 

202(a) authorizes EPA to issue standards applicable to emissions of those pollutants from 

new motor vehicles.

Any standards under CAA section 202(a)(1) “shall be applicable to such vehicles 

... for their useful life.” Emission standards set by the EPA under CAA section 202(a)(1) 

are technology-based, as the levels chosen must be premised on a finding of 

technological feasibility. Thus, standards promulgated under CAA section 202(a) are to 

take effect only “after providing 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)(2); see also

NRDC v. EPA, 655 F. 2d 318, 322 (D.C. Cir. 1981)). EPA is afforded considerable 

discretion under section 202(a) when assessing issues of technical feasibility and 

availability of lead time to implement new technology. Such determinations are “subject 

to the restraints of reasonableness”, which “does not open the door to ‘crystal ball’

inquiry.” NRDC, 655 F. 2d at 328, quoting International Harvester Co. v. Ruckelshaus, 

478 F. 2d 615, 629 (D.C. Cir. 1973). However, “EPA is not obliged to provide detailed 

solutions to every engineering problem posed in the perfection of the trap-oxidizer. In 

the absence of theoretical objections to the technology, the agency need only identify the 

major steps necessary for development of the device, and give plausible reasons for its 

belief that the industry will be able to solve those problems in the time remaining. The 

EPA is not required to rebut all speculation that unspecified factors may hinder ‘real 

world’ emission control.” NRDC, 655 F. 2d at 333-34. In developing such technologybased standards, EPA has the discretion to consider different standards for appropriate 

groupings of vehicles (“class or classes of new motor vehicles”), or a single standard for 

a larger grouping of motor vehicles (NRDC, 655 F. 2d at 338).

Although standards under CAA section 202(a)(1) are technology-based, they are 

not based exclusively on technological capability. EPA has the discretion to consider and 

weigh various factors along with technological feasibility, such as the cost of compliance 

(see section 202(a) (2)), lead time necessary for compliance (section 202(a)(2)), safety 

(see NRDC, 655 F. 2d at 336 n. 31) and other impacts on consumers, and energy impacts 

associated with use of the technology. See George E. Warren Corp. v. EPA, 159 F.3d 

616, 623-624 (D.C. Cir. 1998) (ordinarily permissible for EPA to consider factors not 

specifically enumerated in the Act). See also Entergy Corp. v. Riverkeeper, Inc., 129 

S.Ct. 1498, 1508-09 (2009) (congressional silence did not bar EPA from employing costbenefit analysis under Clean Water Act absent some other clear indication that such 

analysis was prohibited; rather, silence indicated discretion to use or not use such an 

approach as the agency deems appropriate).

In addition, EPA has clear authority to set standards under CAA section 202(a) 

that are technology forcing when EPA considers that to be appropriate, but is not required 

to do so (as compared to standards set under provisions such as section 202(a)(3) and 
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section 213(a)(3)). EPA has interpreted a similar statutory provision, CAA section 231, 

as follows: 

While the statutory language of section 231 is not identical to other provisions in 

title II of the CAA that direct EPA to establish technology-based standards for various 

types of engines, EPA interprets its authority under section 231 to be somewhat similar to 

those provisions that require us to identify a reasonable balance of specified emissions 

reduction, cost, safety, noise, and other factors. See, e.g., Husqvarna AB v. EPA, 254 

F.3d 195 (DC Cir. 2001) (upholding EPA’s promulgation of technology-based standards 

for small non-road engines under section 213(a)(3) of the CAA). However, EPA is not 

compelled under section 231 to obtain the ‘‘greatest degree of emission reduction 

achievable’’ as per sections 213 and 202 of the CAA, and so EPA does not interpret the 

Act as requiring the agency to give subordinate status to factors such as cost, safety, and 

noise in determining what standards are reasonable for aircraft engines. Rather, EPA has 

greater flexibility under section 231 in determining what standard is most reasonable for 

aircraft engines, and is not required to achieve a ‘‘technology forcing’’ result.31

This interpretation was upheld as reasonable in NACAA v. EPA, 489 F.3d 1221, 

1230 (D.C. Cir. 2007). CAA section 202(a) does not specify the degree of weight to 

apply to each factor, and EPA accordingly has discretion in choosing an appropriate 

balance among factors. See Sierra Club v. EPA, 325 F.3d 374, 378 (D.C. Cir. 2003) 

(even where a provision is technology-forcing, the provision “does not resolve how the 

Administrator should weigh all [the statutory] factors in the process of finding the 

‘greatest emission reduction achievable’”). Also see Husqvarna AB v. EPA, 254 F. 3d 

195, 200 (D.C. Cir. 2001) (great discretion to balance statutory factors in considering 

level of technology-based standard, and statutory requirement “to [give appropriate] 

consideration to the cost of applying ... technology” does not mandate a specific method 

of cost analysis); see also Hercules Inc. v. EPA, 598 F. 2d 91, 106 (D.C. Cir. 1978) (“In 

reviewing a numerical standard the agencies must ask whether the agency’s numbers are 

within a zone of reasonableness, not whether its numbers are precisely right”); Permian 

Basin Area Rate Cases, 390 U.S. 747, 797 (1968) (same); Federal Power Commission v. 

Conway Corp., 426 U.S. 271, 278 (1976) (same); Exxon Mobil Gas Marketing Co. v. 

FERC, 297 F. 3d 1071, 1084 (D.C. Cir. 2002) (same).

(a) EPA Testing Authority

Under section 203 of the CAA, sales of vehicles are prohibited unless the vehicle 

is covered by a certificate of conformity. EPA issues certificates of conformity pursuant 

to section 206 of the Act, based on (necessarily) pre-sale testing conducted either by EPA 

or by the manufacturer. The Heavy Duty Federal Test Procedure (FTP) and the 

Supplemental Engine Test (SET) cycle are used for this purpose. Compliance with 

standards is required not only at certification but throughout a vehicle’s useful life, so 

that testing requirements may continue post-certification. Useful life standards may

 

31

 70 FR 69664, 69676, November 17, 2005.
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apply an adjustment factor to account for vehicle emission control deterioration or 

variability in use (section 206(a)). 

EPA established the FTP for emissions measurement in the early 1970s. In 1976, 

in response to the Energy Policy and Conservation Act (EPCA) statute, EPA extended the 

use of the FTP to fuel economy measurement.32 EPA can determine fuel efficiency of a 

vehicle by measuring the amount of CO2 and all other carbon compounds (e.g. total 

hydrocarbons (THC) and carbon monoxide (CO)), and then, by mass balance, calculating 

the amount of fuel consumed.

(b) EPA Enforcement Authority

Section 207 of the CAA grants EPA broad authority to require manufacturers to 

remedy vehicles if EPA determines there are a substantial number of noncomplying 

vehicles. In addition, section 205 of the CAA authorizes EPA to assess penalties of up to 

$37,500 per vehicle for violations of various prohibited acts specified in the CAA. In 

determining the appropriate penalty, EPA must consider a variety of factors such as the 

gravity of the violation, the economic impact of the violation, the violator’s history of 

compliance, and “such other matters as justice may require.”

(2) NHTSA Authority

49 U.S.C. 32902(k)(2), established by Congress in EISA, authorizes NHTSA to 

create a fuel efficiency improvement program for “commercial medium- and heavy-duty 

on-highway vehicles and work trucks”

33 by rulemaking, to include standards, testing, and 

enforcement. Congress directed that the standards, test methods, measurement metrics, 

and compliance and enforcement protocols be “appropriate, cost-effective, and 

technologically feasible” for the vehicles to be regulated, while achieving the “maximum 

feasible improvement” in fuel efficiency. Since this is the first rulemaking that NHTSA 

has conducted under 32902(k)(2), this is the first opportunity the agency has had to 

interpret these factors in the context of setting standards, choosing metrics, and 

determining test methods and compliance/enforcement systems. Congress also gave 

NHTSA the authority to set separate standards for different classes of these vehicles, but 

required that all standards adopted provide not less than four full model years of 

regulatory lead-time and three full model years of regulatory stability.

(a) NHTSA Testing Authority

49 U.S.C. 32902(k)(2) states that NHTSA must adopt and implement appropriate, 

cost-effective, and technologically feasible test methods and measurement metrics as part 

of the fuel efficiency improvement program. 

 

32 See 49 U.S.C. 32904(c).

33 “Commercial medium- and heavy-duty on-highway vehicles” are defined at 49 U.S.C. § 32901(a)(7), and 

“work trucks” are defined at (a)(19).
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(b) NHTSA Enforcement Authority

49 U.S.C. 32902(k)(2) also states that NHTSA must adopt and implement 

appropriate, cost-effective, and technologically feasible compliance and enforcement 

protocols for the fuel efficiency improvement program. 

G. Future HD GHG and Fuel Consumption Rulemakings

Today’s proposal represents a first regulatory step by NHTSA and EPA to address 

the multi-faceted challenges of reducing fuel use and greenhouse gas emissions from 

these vehicles. By focusing on existing technologies and well-developed regulatory

tools, the agencies are able to propose rules that we believe will produce real and 

important reductions in GHG emissions and fuel consumption within only a few years. 

Within the context of this regulatory timeframe, our proposal is very aggressive - with 

limited leadtime compared to historic heavy-duty regulations - but pragmatic in the 

context of technologies that are available. 

While we are now only proposing this first step, it is worthwhile to consider how 

future regulations that may follow this step may be constructed. Technologies such as 

hybrid drivetrains, advanced bottoming cycle engines, and full electric vehicles are 

promoted in this first step through incentive concepts as discussed in section IV, but we 

believe that these advanced technologies would not be necessary to meet the proposed 

standards, which are premised on the use of existing technologies. When we begin our 

future work to develop a possible next set of regulatory standards, the agencies expect 

these advanced technologies to be an important part of the regulatory program and will 

consider them in setting the stringency of any standards beyond the 2018 model year.

We will not only consider the progress of technology in our future regulatory

efforts, but the agencies are also committed to fully considering a range of regulatory

approaches. To more completely capture the complex interactions of the total vehicle 

and the potential to reduce fuel consumption and GHG emissions through the 

optimization of those interactions may require a more sophisticated approach to vehicle 

testing than we are proposing today for the largest heavy-duty vehicles. In future 

regulations, the agencies expect to fully evaluate the potential to expand the use of 

vehicle compliance models to reflect engine and drivetrain performance. Similarly, we 

intend to consider the potential for complete vehicle testing using a chassis dynamometer, 

not only as a means for compliance, but also as a complementary tool for the 

development of more complex vehicle modeling approaches. In considering these more 

comprehensive regulatory approaches, the agencies will also reevaluate whether separate 

regulation of trucks and engines remains necessary.

In addition to technology and test procedures, vehicle and engine drive cycles are 

an important part of the overall approach to evaluating and improving vehicle 

performance. EPA working through the WP.29 Global Technical Regulation (GTR) 

process has actively participated in the development of a new world harmonized Heavy 

Duty Certification procedure (WHDC) for heavy-duty engines. EPA is committed to 

bringing forward these new procedures as part of our overall comprehensive approach for 
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controlling criteria and GHG emissions. However, we believe the important issues and 

technical work related to setting new criteria emissions standards appropriate for the 

WHDC are significant and beyond the scope of this rulemaking. Therefore, the agencies 

are not proposing to adopt these test procedures in today’s proposal, but we are ready to 

work with interested stakeholders to adopt these procedures in a future action.

As with today’s proposal, our future efforts will be based on collaborative 

outreach with the stakeholder community and will be focused on a program that delivers 

on our energy security and environmental goals without restricting the industry’s ability 

to produce a very diverse range of vehicles serving a wide range of needs.

II. Proposed GHG and Fuel Consumption Standards for

Heavy Duty Engines and Vehicles

This section describes the standards and implementation dates that the agencies 

are proposing for the three categories of heavy duty vehicles. The agencies have 

performed a technology analysis to determine the level of standards that we believe 

would be appropriate, cost-effective, and feasible during the rulemaking timeframe. This 

analysis, described in Section III and in more detail in Draft RIA Chapter 2, considered:

 the level of technology that is incorporated in current new trucks, 

 the available data on corresponding CO2 emissions and fuel consumption for these 

vehicles, 

 technologies that would reduce CO2 emissions and fuel consumption and that are 

judged to be feasible and appropriate for these vehicles through 2018 model year, 

 the effectiveness and cost of these technologies, 

 projections of future U.S. sales for trucks, and 

 forecasts of manufacturers’ product redesign schedules.

A. What vehicles would be affected?

EPA and NHTSA are proposing standards for heavy duty engines and also for 

what we refer to generally as “heavy duty trucks.” As noted in Section I, for purposes of 

this preamble, the term “heavy-duty: or “HD” is used to apply to all highway vehicles 

and engines that are not regulated by the light-duty vehicle, light-duty truck and medium 

duty passenger vehicle greenhouse gas and CAFE standards issued for MYs 2012-2016. 

Thus, in this notice, unless specified otherwise, the heavy-duty category incorporates all 

vehicles rated at a gross vehicle weight greater than 8,500 pounds, and the engines that 

power these vehicles, except for MDPVs. The CAA defines heavy-duty vehicles as 

trucks, buses or other motor vehicles with a gross vehicle weight rating exceeding 6000 

pounds. CAA section 202(b)(3). In the context of the CAA, the term HD as used in 

these proposed rules thus refers to a subset of these vehicles and engines. EISA Section 

103(a)(3) defines a ‘commercial medium- and heavy-duty on-highway vehicle’ as an on-
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highway vehicle with a gross vehicle weight rating (GVWR) of 10,000 pounds or more.34 

EISA Section 103(a)(6) defines a ‘work truck’ as a vehicle that is rated at between 8,500 

and 10,000 pounds gross vehicle weight and is not a medium duty passenger vehicle.35 

Therefore, the term "heavy duty trucks" in this proposal refers to both work trucks and 

commercial medium and heavy duty on-highway vehicles as defined by EISA. Heavy 

duty engines affected by the proposed standards are those that are installed in commercial 

medium and heavy duty trucks, except for the engines installed in vehicles certified to a 

complete vehicle emissions standard based on a chassis test, which would be addressed as 

a part of those complete vehicles, and except for engines used exclusively for stationary

power when the vehicle is parked. The agencies’ scope is the same with the exception of 

recreational vehicles (or motor homes), as discussed above. EPA is proposing to include 

recreational on-highway vehicles within their rulemaking, while NHTSA is limiting their 

scope to commercial trucks which would not include these vehicles.

EPA and NHTSA are proposing standards for each of the following categories, 

which together comprise all heavy duty vehicles and all engines used in such vehicles.36

In order to most appropriately regulate the broad range of heavy duty vehicles, the 

agencies are proposing to set separate engine and vehicle standards for the combination 

tractors and the Class 2b through 8 vocational trucks and the engines installed in them. 

The engine standards and test procedures for engines installed in the tractors and 

vocational trucks are discussed within the applicable vehicle sections. 

 Class 7 and 8 Combination Tractors

 Heavy-Duty Pickup Trucks and Vans

 Class 2b through 8 Vocational Trucks

As discussed in Section IX, the agencies are not proposing GHG emission and 

fuel consumption standards for trailers at this time. In addition, the agencies are 

proposing to not set standards at this time for engine, chassis, and vehicle manufacturers 

which meet the small business definitions. More detailed discussion of each regulatory

category is included in the subsequent sections below.

 

34 Codified at 49 U.S.C. § 32901(a)(7).

35 EISA Section 103(a)(6) is codified at 49 U.S.C. 32901(a)(19). EPA defines medium-duty passenger 

vehicles as any complete vehicle between 8,500 and 10,000 pounds GVWR designed primarily for the 

transportation of persons which meet the criteria outlined in 40 C.F.R. 86.1803-01. The definition 

specifically excludes any vehicle that (1) has a capacity of more than 12 persons total or, (2) is designed to 

accommodate more than 9 persons in seating rearward of the driver’s seat or, (3) has a cargo box (e.g., 

pick-up box or bed) of six feet or more in interior length. (See the Tier 2 final rulemaking, 65 FR 6698, 

February 10, 2000.)

36 Both agencies have authority to develop separate standards for vehicle and engine categories, as 

appropriate. See CAA section 202 (a) (1) (authority to establish standards for “any class or classes of new 

motor vehicles or engines” and 49 USC 32902 (k) (2) (authority to establish standards for HD vehicles 

that are “appropriate, cost-effective, and technologically feasible” that are designed to achive the 

“maximum feasible improvement” in fuel efficiency; authority to establish “separate standards for different 

classes of vehicles under this subsection.” NHTSA interprets 329029k)(2) to include a grant of authority to 

establish engines standards pursuant to the broader statement of authority to establish standards that 

achieve the maximum feasible improvement in fuel efficiency.) 
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B. Class 7/8 Combination Tractors

EPA is proposing CO2 standards and NHTSA is proposing fuel consumption 

standards for new Class 7/8 combination tractors. The standards are for the tractor cab, 

with a separate standard for the engines that are installed in the tractor. Together these 

standards would achieve reductions up to 20 percent from tractor cabs. As discussed 

below, EPA is proposing to adopt the existing useful life definitions for heavy duty 

engines for the Class 7/8 tractors. NHTSA is proposing fuel consumption standards for 

tractors, and engine standards for heavy duty engines for Class 7/8 tractors. The 

agencies' analyses, as discussed briefly below and in more detail later in this preamble 

and in the Draft RIA Chapter 2, show that these standards are appropriate and feasible

under each agency’s respective statutory authorities. 

EPA is also proposing standards to control N2O, CH4, and HFC emissions from 

Class 7/8 combination tractors. The proposed heavy duty engine standards for both N2O 

and CH4 and details of the standard are included in the discussion in II.E. The proposed 

air conditioning leakage standards applying to tractor manufacturers to address HFC 

emissions are included in Section II.E. 

The agencies are proposing CO2 emissions and fuel consumption standards for the 

combination tractors that will focus on reductions that can be achieved through 

improvements in the tractor (such as aerodynamics), tires, and other vehicle systems. 

The agencies are also proposing heavy duty engine standards for CO2 emissions and fuel 

consumption that would focus on potential technological improvements in fuel 

combustion and overall engine efficiency. 

The agencies have analyzed the feasibility of achieving the CO2 and fuel 

consumption standards, based on projections of what actions manufacturers are expected 

to take to reduce emissions and fuel consumption. EPA and NHTSA also present the 

estimated costs and benefits of the standards in Section III. In developing the proposed 

rules, the agencies have evaluated the kinds of technologies that could be utilized by

engine and tractor manufacturers, as well as the associated costs for the industry and fuel 

savings for the consumer and the magnitude of the CO2 and fuel economy savings that 

may be achieved.

EPA and NHTSA are proposing attribute-based standards for the Class 7/8 

combination tractors, or, put another way, we are proposing to set different standards for 

different subcategories of these tractors with the basis for subcategorization being 

particular tractor attributes. Attribute-based standards in general recognize the variety of 

functions performed by vehicles and engines, which in turn can affect the kind of 

technology that is available to control emissions and reduce fuel consumption, or its 

effectiveness. Attributes that characterize differences in the design of vehicles, as well 

as differences in how the vehicles will be employed in-use, can be key factors in 

evaluating technological improvements for reducing CO2 emissions and fuel 

consumption. Developing an appropriate attribute-based standard can also avoid 

interfering with the ability of the market to offer a variety of products to meet consumer 

demand. There are several examples of where the agencies have utilized an attribute-
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based standard. In addition to the example of the recent light-duty vehicle fuel economy 

and GHG rule, in which the standards are based on the attribute of vehicle "footprint," the 

existing non-GHG heavy duty engine criteria pollutant emission standards for many years 

have been based on a vehicle weight attribute (Light Heavy, Medium Heavy, Heavy 

Heavy) with different useful life periods, which is the same approach proposed for the 

engine GHG and fuel consumption standards discussed below. 

Heavy duty combination trucks are built to move freight. The ability of a truck 

to meet a customer's freight transportation requirements depends on three major 

characteristics of the tractor: the gross vehicle weight rating (which along with gross 

combined weight rating (GCWR) establishes the maximum carrying capacity of the 

tractor and trailer), cab type (sleeper cabs provide overnight accommodations for 

drivers), and the tractor roof height (to mate tractors to trailers for the most fuel-efficient 

configuration). Each of these attributes impacts the baseline fuel consumption and GHG 

emissions, as well as the effectiveness of possible technologies, like aerodynamics, and is 

discussed in more detail below. 

The first tractor characteristic to consider is payload which is determined by a 

tractor’s gross vehicle weight rating (GVWR) and gross combined weight rating 

(GCWR) relative to the weight of the tractor, trailer, fuel, driver, and equipment. Class 7 

trucks, which have a GVWR of 26,000-33,000 pounds and a typical GCWR of 65,000 

pounds, have a lesser payload capacity than Class 8 trucks. Class 8 trucks have a GVWR 

of greater than 33,000 pounds and a typical 80,000 pound GCWR. Consistent with the 

recommendation in the National Academy of Sciences March 2010 Report to NHTSA,37

the agencies are proposing a load specific fuel consumption metric (g/ton-mile and 

gal/1000 ton-mile) where the “ton” represents the amount of payload. Generally, higher 

payload capacity trucks have better specific fuel consumption and GHG emissions than 

lower payload capacity trucks. Therefore, since the amount of payload that a Class 7 

truck can carry is less than the Class 8 truck’s payload capacity, the baseline fuel 

consumption and GHG emissions performance per ton-mile differs between the 

categories. It is consequently reasonable to distinguish between these two vehicle 

categories, so that the agencies are proposing separate standards for Class 7 and Class 8 

tractors. 

The agencies are not proposing to set a single standard for both Class 7 and 8 

tractors based on the payload carrying capabilities and assumed typical payload levels of 

Class 8 tractors alone, as that would quite likely have the perverse impact of increasing 

fuel consumption and greenhouse gas emissions. Such a single standard would penalize 

Class 7 vehicles in favor of Class 8 vehicles, however the greater capabilities of Class 8 

tractors and their related greater efficiency when measured on a per ton-mile basis is only

relevant in the context of operations where that greater capacity is needed. For many

applications such as regional distribution, the trailer payloads dictated by the goods being 

carried are lower than the average Class 8 tractor payload. In those situations, Class 7 

 

37 March 2010 NAS Report, Recommendation 2-1.
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tractors are more efficient than Class 8 tractors when measured on a per ton-mile of 

actual freight carried. This is because the extra capabilities of Class 8 tractors add 

additional weight to vehicle that is only beneficial in the context of its higher capabilities. 

The existing market already selects for vehicle performance based on the projected 

payloads. By setting separate standards the agencies do not advantage or disadvantage 

class 7 or 8 tractors relative to one another and continue to allow trucking fleets to 

purchase the vehicle most appropriate to their business practices.

The second characteristic that affects fuel consumption and GHG emissions is the 

relationship between the tractor cab roof height and the type of trailer used to carry the 

freight. The primary trailer types are box, flat bed, tanker, bulk carrier, chassis, and low 

boys. Tractor manufacturers sell tractors in three roof heights – low, mid, and high. The 

manufacturers do this to obtain the best aerodynamic performance of a tractor-trailer 

combination, resulting in reductions of GHG emissions and fuel consumption, because it 

allows the frontal area of the tractor to be similar in size to the frontal area of the trailer. 

In other words, high roof tractors are designed to be paired with a (relatively tall) box 

trailer while a low roof tractor is designed to pull a (relatively low) flat bed trailer. The 

baseline performance of a high roof, mid roof, and low roof tractor differs due to the 

variation in frontal area which determines the aerodynamic drag. For example, the 

frontal area of a low roof tractor is approximately 6 square meters, while a high roof 

tractor has a frontal area of approximately 9.8 square meters. Therefore, as explained 

below, the agencies are proposing that the roof height of the tractor determine the trailer 

type required to be used to demonstrate compliance of a truck with the fuel consumption 

and CO2 emissions standards. As with vehicle weight classes, setting separate standards 

for each tractor roof height helps ensure that all tractors are regulated to achieve 

appropriate improvements, without inadvertently leading to increased emissions and fuel 

consumption by shifting the mix of vehicle roof heights offered in the market away from 

a level customarily tied to the actual trailers vehicles will haul in-use.

Tractor cabs typically can be divided into two configurations – day cabs and 

sleeper cabs. Line haul operations typically require overnight accommodations due to 

Federal Motor Carrier Safety Administration hours of operation requirements.38 

Therefore, some truck buyers purchase tractor cabs with sleeping accommodations, also 

known as sleeper cabs, because they do not return to their home base nightly. Sleeper 

cabs tend to have a greater empty curb weight than day cabs due to the larger cab volume 

and accommodations, which lead to a higher baseline fuel consumption for sleeper cabs 

when compared to day cabs. In addition, there are specific technologies, such as 

extended idle reduction technologies, which are appropriate only for tractors which hotel 

-- such as sleeper cabs. To respect these differences, the agencies are proposing to create 

separate standards for sleeper cabs and day cabs. 

 

38 FMCSA’s Hours-of-Service regulations put limits in place for when and how long commercial motor 

vehicle (CMV) drivers may drive. They are based on an exhaustive scientific review and are designed to 

ensure truck drivers get the necessary rest to perform safe operations. See 49 CFR Part 395, and see also

http://www.fmcsa.dot.gov/rules-regulations/topics/hos/index.htm (last accessed August 8, 2010).
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To account for the relevant combinations of these attributes, the agencies 

therefore propose to segment combination tractors into the following nine regulatory

subcategories:

 Class 7 Day Cab with Low Roof

 Class 7 Day Cab with Mid Roof

 Class 7 Day Cab with High Roof

 Class 8 Day Cab with Low Roof

 Class 8 Day Cab with Mid Roof

 Class 8 Day Cab with High Roof

 Class 8 Sleeper Cab with Low Roof

 Class 8 Sleeper Cab with Mid Roof

 Class 8 Sleeper Cab with High Roof

The agencies have not identified any Class 7 or Class 8 day cabs with mid roof 

heights in the market today but welcome comments with regard to this market 

characterization.

In addition, the agencies are proposing to classify all vehicles with sleeper cabs as 

tractors. The proposed rules would not allow vehicles with sleeper cabs to be classified 

as vocational vehicles. This provision is intended prevent the initial manufacture of 

straight truck vocational vehicles with sleeper cabs that, soon after introduction into 

commerce, would be converted to line haul tractors, as a means to circumvent the Class 8 

sleeper cab regulations. The agencies welcome comments on the likelihood of 

manufacturers using such an approach to circumvent the regulations and the appropriate 

regulatory provisions the agencies should consider to prevent such actions.

(1) What are the Proposed Class 7/8 Tractor and Engine CO2 Emissions and 

Fuel Consumption standards and their timing?

In developing the proposed tractor and engine standards, the agencies have 

evaluated the current levels of emissions and fuel consumption, the kinds of technologies 

that could be utilized by truck and engine manufacturers to reduce emissions and fuel 

consumption from tractors and engines, the associated lead time, the associated costs for 

the industry, fuel savings for the consumer, and the magnitude of the CO2 and fuel 

economy savings that may be achieved. The technologies that the agencies considered 

while setting the proposed tractor standards include improvements in aerodynamic 

design, lower rolling resistance tires, extended idle reduction technologies, and vehicle 

empty weight reduction. The technologies that the agencies considered while setting the 

engine standards include engine friction reduction, aftertreatment optimization, and 

turbocompounding, among others. The agencies’ evaluation indicates that these 

technologies are available today, but have very low application rates in the market. The 

agencies have analyzed the technical feasibility of achieving the proposed CO2 and fuel 

consumption standards for tractors and engines, based on projections of what actions 

manufacturers would be expected to take to reduce emissions and fuel consumption to 

achieve the standards. EPA and NHTSA also present the estimated costs and benefits of 
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the class 7 and 8 combination tractor and engine standards in Section III and in DRIA 

Chapter 2. 

(a) Tractor Standards

The agencies are proposing the following standards for Class 7/8 combination 

tractors in Table II-1, using the subcategorization approach just explained. As noted, the 

agencies are not aware of any mid roof day cab tractors at this time, but are proposing 

that any Class 7 and 8 day cabs with a mid roof would meet the respective low roof 

standards, based on the similarity in baseline performance and similarity in expected 

improvement of mid roof sleeper cabs relative to low roof sleeper cabs. The agencies are 

aware of low roof tractor cabs which have an adjustable roof fairing allowing the operator 

to adjust the roof height to most appropriately match the trailer. The agencies welcome 

comment on the best approach to handle this type of technology. 

As explained below in Section III, EPA has determined that there is sufficient 

leadtime to introduce the tractor and engine technologies into the fleet starting in the 

2014 model year, and is proposing standards starting for that model year. EPA is 

proposing more stringent tractor standards for the 2017 model year which reflect the CO2

emissions reductions required through the 2017 model year engine standards. (As 

explained in Section II.B.2.o below, engine performance is one of the inputs into the 

compliance model, and that input will change in 2017 to reflect the 2017 MY engine 

standards.) The 2017 MY vehicle standards are not premised on manufacturers installing 

additional vehicle technologies. EPA’s proposed standards apply throughout the useful 

life period as described in Section V. Similar to EPA’s non-GHG standards approach, 

manufacturers may generate and use credits from Class7/8 combination tractors to show 

compliance with the standards. 

NHTSA is proposing Class 7/8 tractor fuel consumption standards that are 

voluntary opt-in standards in the 2014 and 2015 model years and become mandatory

beginning in the 2016 model year, as required by the lead time and stability requirement 

within EISA. NHTSA is also proposing new standards for the 2017 model year which 

reflect additional improvements in the heavy duty engines only. NHTSA proposes to use 

useful life considerations for establishing fuel consumption performance for initial 

compliance and for ABT, NHTSA does not intend to implement an in-use compliance 

program for fuel consumption because it is not currently anticipated there will be notable 

deterioration of fuel consumption over the useful life. NHTSA believes that the vehicle 

and engine standards proposed for combination tractors are appropriate, cost-effective, 

and technologically feasible in the rulemaking timeframe based on our analysis detailed 

below in Section III and in the draft RIA. 

EPA and NHTSA are not proposing to make the 2017 vehicle standards more 

stringent based on the application of additional truck technologies because projected 

application rates of truck technologies used in setting the 2014 truck standard already 

reflect the maximum application rates we believe appropriate for these vehicles given 

their specific use patterns as described in Section III. We considered setting more 

stringent standards for Class 7/8 tractors based on the application of more advanced 
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aerodynamic systems, such as self-compensating side extenders or other advanced 

aerodynamic technologies, but concluded that those technologies would not be fully 

developed in the timeframe of this regulation. We request comment on this decision, 

supported by data as appropriate. 

Table II-1: Heavy Duty Combination Tractor Emissions and Fuel Consumption Standards 

2014 Model Year CO2 Grams per Ton-Mile

Day Cab Sleeper Cab

Class 7 Class 8 Class 8

Low Roof 108 81 65

Mid Roof 108 81 65

High Roof 123 89 73

2014-2016 Model Year Gallons of Fuel per 1000 Ton-Mile39

Day Cab Sleeper Cab

Class 7 Class 8 Class 8

Low Roof 10.6 8.0 6.4

Mid Roof 10.6 8.0 6.4

High Roof 12.1 8.7 7.2

2017 Model Year CO2 Grams per Ton-Mile

Day Cab Sleeper Cab

Class 7 Class 8 Class 8

Low Roof 106 80 65

Mid Roof 106 80 65

High Roof 120 88 72

2017-2018 Model Year Gallons of Fuel per 1000 Ton-Mile

Day Cab Sleeper Cab

Class 7 Class 8 Class 8

Low Roof 10.4 7.9 6.4

Mid Roof 10.4 7.9 6.4

High Roof 11.8 8.6 7.1

Based on our analysis, the 2017 model year standards represent up to a 20 percent 

reduction in CO2 emissions and fuel consumption over a 2010 model year baseline, as 

detailed in Section III.A.2.

(i) Off-Road Tractor Standards

In developing the proposal EPA and NHTSA received comment from 

manufacturers and owners that trucks sometimes have very limited on-road usage. These 

trucks by definition of Title 40, Part 85.1703 are motor vehicles, but will spend the 

 

39 Manufacturers may voluntarily opt-in to the NHTSA fuel consumption program in 2014 or 2015. If a 

manufacturer opts-in, the program becomes mandatory. See Section [add cross reference] below for more 

information about NHTSA’s voluntary opt-in program for MYs 2014 and 2015.
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majority of their operations off-road. Trucks, such as those used in oil fields, will 

experience little benefit from improved aerodynamics and low rolling resistance tires. 

The agencies are therefore proposing to allow a narrow range of these de facto off-road 

trucks to be excluded from the proposed tractor standards because the trucks do not travel 

at speeds high enough to realize aerodynamic improvements and require special off-road 

tires such as lug tires. The trucks must still use a certified engine, which will provide fuel 

consumption and CO2 emission reductions to the truck in all applications. To ensure the 

limited use of these trucks, the agencies are proposing requirements that the vehicles have 

off-road tires, have limited high speed operation, and are designed for specific off-road 

applications. 40 The agencies are proposing that a truck must meet the following 

requirements to qualify for an exemption from the vehicle standards for Class 7/8 

tractors:

 Installed tires which are lug tires or contain a speed rating of less than or 

equal to 60 mph; and

 Include a vehicle speed limiter governed to 55 mph, and

 Contain PTO controls, or have axle configurations other than 4x2, 6x2, or 

6x4 and have GVWR greater than 57,000 pounds; and

 Has a frame Resisting Bending Moment (RBM) greater than 2,000,000 lb. 

in.41

EPA and NHTSA have concluded that the onroad performance losses and 

additional costs to develop a truck which meets these specifications will limit the 

exemption to trucks built for the desired purposes.42 The agencies welcome comment on 

the proposed requirements and exemptions.

(b) Engine Standards

EPA is proposing GHG standards and NHTSA is proposing fuel consumption 

standards for new heavy duty engines. The standards will vary depending on the type of 

vehicle in which they are used, as well as whether the engines are diesel or gasoline 

powered. This section discusses the standards for engines used in Class7/8 combination 

 

40 For purposes of compliance with NHTSA’s safety regulations, such as FMVSS Nos. 119 and 121, a 

manufacturer wishing for their vehicle to classify as “off-road” would still need to work with the relevant 

NHTSA office to declare its vehicle as “off-road” if it uses public roads at any point in its service. 

41 The agencies have found based on standard truck specifications, that vehicles designed for significant 

off-road applications, such as concrete pumper and logging trucks have RRM greater than 2,100,000 lb.in. 

(ranging up to 3,580,000 lb. in.). The typical on highway tractors have RBM of 1,390,000 lb. in.

42 The estimated cost for a lift axle is approximately $10,000. Axles with weight ratings greater than a 

typical on-road axle cost an additional $3000.
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tractors, and also provides some overall background information. More information is 

also provided in the discussion of the standards for engines used in vocational trucks. 

EPA’s existing non-GHG emissions regulations for heavy duty on highway 

engines establish four regulatory classes that represent the engine’s intended and primary

truck application.43 The Light Heavy Duty Diesel (LHDD) engines are intended for 

application in Class 2b through Class 5 trucks (8,501 through 19,500 pounds GVWR). 

The Medium Heavy Duty Diesel (MHDD) engines are intended for Class 6 and Class 7 

trucks (19,501 through 33,000 pounds GVWR). The Heavy Heavy Duty Diesel (HHDD) 

engines are primarily used in Class 8 trucks (33,001 pounds and greater GVWR). Lastly, 

spark ignition engines (primarily gasoline-powered engines) installed in incomplete 

vehicles less than 14,000 pounds GVWR and spark ignition engines that are installed in 

all vehicles (complete or incomplete) greater than 14,000 pounds GVWR are grouped 

into a single engine regulatory class. The engines in these four regulatory classes range 

in size between approximately five liters and sixteen liters.

For the purposes of the GHG engine emissions and engine fuel consumption 

standards that EPA and NHTSA are proposing today, the agencies intend to maintain 

these same four regulatory classes for both sets of standards. This class structure would 

enable the agencies to set standards that appropriately reflect the technology available for 

engines for use in each type of vehicle, and that are therefore technologically feasible for 

these engines. This section discusses the MHDD and HHDD engines used in Class 7 and 

8 combination tractors.

EPA's proposed heavy duty CO2 emission standards for diesel engines installed in 

combination tractors are presented in Table II-2. We should note that this does not cover 

gasoline or LHDD engines as they are not used in 7/8 combination tractors. Similar to 

EPA’s non-GHG standards approach, manufacturers may generate and use credits to 

show compliance with the standards. EPA is proposing to adopt the existing useful life 

definitions for heavy duty engines. The EPA standards would become effective in the 

2014 model year, with more stringent standards becoming effective in model year 2017. 

Recently, EPA’s non-GHG heavy duty engine program provided new emissions 

standards for the industry in three year increments. Largely, the heavy duty engine and 

truck manufacturer product plans have fallen into three year cycles to reflect this 

regulatory environment. The proposed two-step CO2 emission standards recognize the 

opportunity for technology improvements over this timeframe while reflecting the typical 

diesel truck manufacturers’ product plan cycles. 

With respect to the lead time and cost of incorporating technology improvements 

that reduce GHG emissions and fuel consumption, EPA and NHTSA place important 

weight on the fact that during MYs 2014-2017 engine manufacturers are expected to 

redesign and upgrade their products. Over these four model years there will be an 

opportunity for manufacturers to evaluate almost every one of their engine models and 

 

43 Insert cite for LHDD, MHDD, HHDD intended classes
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add technology in a cost-effective way, consistent with existing redesign schedules, to 

control GHG emissions and reduce fuel consumption. The time-frame and levels for the 

standards, as well as the ability to average, bank and trade credits and carry a deficit 

forward for a limited time, are expected to provide manufacturers the time needed to 

incorporate technology that will achieve the proposed GHG and fuel consumption 

reductions, and to do this as part of the normal engine redesign process. This is an 

important aspect of the proposed rules, as it will avoid the much higher costs that would 

occur if manufacturers needed to add or change technology at times other than these 

scheduled redesigns. This time period will also provide manufacturers the opportunity to 

plan for compliance using a multi-year time frame, again in accord with their normal 

business practice. Further details on lead time, redesigns and technical feasibility can be 

found in Section III

NHTSA’s fuel consumption standards, also presented in Table II-2, would contain 

a voluntary opt-in to the engine program starting in 2014 model year, with mandatory

engine standards starting in 2017 model year, harmonized with EPA’s 2017 model year 

standards. A manufacturer may opt-in to NHTSA’s voluntary standards in 2014, 2015 or 

2016. Once a manufacturer opts-in the standards become mandatory for the opt-in and 

subsequent model years, and the manufacturer may not reverse its decision. To opt into 

the program, a manufacture must declare its intent to opt in to the program at the same 

time it submits the Pre-Certification Compliance Report. See Section 49 CFR Part 535.8 

for information related to the Pre-Certification Compliance Report. A manufacturer 

opting into the program would begin tracking credits and debits beginning in the model 

year in which they opt into the program.

Table II-2: Proposed Heavy Duty Diesel Engine Standards for Engines Installed in Tractors

Effective 2014 Model Year

MHDD Engine HHDD Engine

CO2 Standard (g/bhp-hr) 502 475

Optional Fuel Consumption 

Standard (gallon/100 bhp-hr)

4.93 4.67

Effective 2017 Model Year

MHDD Engine HHDD Engine

CO2 Standard (g/bhp-hr) 487 460

Fuel Consumption (gallon/100 

bhp-hr)

4.78 4.52

Combination tractors spend the majority of their operation at steady state 

conditions, and will obtain in-use benefit of technologies such as turbocompounding and 

other waste heat recovery technologies during this kind of typical engine operation. 

Therefore, the engines installed in tractors would be required to meet the standard based 

on the Supplemental Engine Test (SET), which is a steady state test cycle.

The baseline HHDD engine performance in 2010 model year on the SET is 490 g 

CO2/bhp-hr (4.81 gal/100 bhp-hr), as determined from confidential data provided by

manufacturers and the non-GHG emissions certification process. Similarly, the baseline 
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MHDD engine performance on the SET cycle is 518 g CO2/bhp-hr (5.09 gallon/100-bhphr) in the 2010 model year. Further discussion of the derivation of the baseline can be 

found in Section III The diesel engine standards that EPA is proposing and the voluntary 

opt-in standards being proposed by NHTSA for the 2014 model year would require diesel 

engine manufacturers to achieve on average a three percent reduction in fuel consumption 

and CO2 emissions over the baseline 2010 model year performance for the engines. The 

agencies’ assessment of the findings of the March 2010 NAS Report and other literature 

sources indicates that there are technologies available to reduce fuel consumption by this 

level in the proposed timeframe. These technologies include improved turbochargers, 

aftertreatment optimization, low temperature exhaust gas recirculation, and engine 

friction reductions. Additional discussion on technical feasibility is included in Section 

III below and in DRIA Chapter 2.

Furthermore, the agencies are proposing that diesel engines further reduce fuel 

consumption and CO2 emissions from the 2010 model year baseline in 2017 model year. 

The proposed reductions represent on average a six percent reduction for MHDD and 

HHDD engines required to use the SET-based standard. The additional reductions could 

likely be achieved through the increased refinement of the technologies projected to be 

implemented for 2014, plus the addition of turbocompounding or other waste heat 

recovery systems. The agencies’ analysis indicates that this type of advanced engine 

technology would require a longer development time than the 2014 model year, and we 

therefore are proposing to provide additional lead time to allow for its introduction. 

The agencies are aware that some truck and engine manufacturers would prefer to 

align their product development plans for these engine standards with their current plans 

to meet OnBoard Diagnostic (OBD) regulations for EPA and California in 2013 and 

2016. We believe our proposed averaging, banking and trading provisions already 

provide these manufacturers with considerable flexibility to manage their GHG 

compliance plans consistent with the 2013 model year. Nevertheless, we are requesting 

comment on whether EPA and NHTSA should provide additional defined phase-in 

schedules that would more explicitly accommodate this request. For example, we request 

comment on a phase-in schedule with a standard of 485 g/bhp-hr for the years 2013-2015 

followed by a standard of 460 g/bhp-hr for 2016-18 with the associated fuel consumption 

values for the NHTSA program. This phase-in schedule is just one of many potential 

schedules that would provide identical fuel savings and emissions reductions for the 

period from 2013-2018. If commenters wish to discuss a different phase-in schedule than 

the one proposed by the agencies, we request that commenters include a description of 

thei preferred phase-in schedule, including an analysis showing that it would be at least 

as effective (or more) as the primary program for the period through the 2018 model year. 

We also request comment on whether similar provisions should be made for the 

vocational engine standards discussed later in this section.

In proposing this standard for heavy-duty diesel engines used in class7/8 

combination trucks, the agencies have examined the current performance levels of the 

engines across the fleet. EPA and NHTSA found that a large majority of the engines 

were generally relatively close to the average baseline, with some above and some below. 

We recognize, however, that when regulating a category of engines for the first time, 
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there will be individual products that may deviate significantly from this baseline level of 

performance. For the current fleet there is a relatively small group of engines that are 

significantly worse than the average baseline for other engines. In proposing the 

standards, the agencies have looked primarily at the typical performance levels of the 

majority of the engines in the fleet, and the increased performance that would be 

achieved through increased spread of technology. The agencies also recognize that for 

the smaller group of products, the same reduction from the industry baseline may be 

more costly than the agencies have assumed or perhaps even not feasible in the timing of 

these standards. We are therefore proposing a regulatory alternative whereby a 

manufacturer would have the option to comply with a unique standard based on a three 

percent reduction from an individual products own 2011 baseline level. Our assessment 

is that this three percent reduction is appropriate given the same technology packages and 

cost we have estimated for the primary program. We do not believe this alternative needs 

to continue past 2016 since manufacturers will have had ample opportunity to benchmark 

competitive products and make appropriate changes to bring their product performance 

into line with the rest of the industry. However, we are requesting comment on the 

potential to extend this regulatory alternative for one additional year for a single engine 

family with performance measured in that year as six percent beyond the engine’s own 

2011 baseline level. We also request comment on the level of reduction beyond the 

baseline that is appropriate in this alternative. The three percent level reflects the 

aggregate improvement beyond the baseline we are requiring of the entire industry. As 

this provision is intended to address potential issues for legacy products that we would 

expect to be replaced or significantly improved at the manufacturer’s next product 

change, we request comment if a two percent reduction would be more appropriate. We 

would consider two percent rather than three percent if we were convinced that making 

all of the changes we have outlined in our assessment of the technical feasibility of the 

standards was not possible for some engines due to legacy design issues that will change 

in the future. We are proposing that manufacturers making use of these provisions would 

not be able to generate emissions credits from other engines in the same regulatory

category as the engines complying using this alternate approach.

EPA and NHTSA considered setting even more stringent engine standards for the 

2017 model year based on the use of more sophisticated waste heat recovery technologies 

such as bottoming cycle engine designs. We are not today proposing more stringent 

standards because we do not believe this technology can be broadly available by 2017 

model year. We request comment on the technological feasibility and cost-effectiveness 

of more stringent standards in the timeframe of the proposed standards.

(c) In-use Standards

Section 202(a)(1) of the Clean Air Act specifies that EPA is to adopt emissions 

standards that are applicable for the useful life of the vehicle. The in-use standards that 

EPA is proposing would apply to individual vehicles and engines. NHTSA is not 

proposing to adopt in-use. 

EPA is proposing that the in-use standards for heavy duty engines installed in 

tractors be established by adding an adjustment factor to the full useful life emissions and 
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fuel consumption results projected in the EPA certification process. EPA and NHTSA 

are proposing a 2 percent adjustment factor for the in-use standard to provide a 

reasonable margin for production and test-to-test variability that could result in 

differences between the initial emission test results and emission results obtained during 

subsequent in-use testing. 

EPA is also proposing that the useful life for these engine and vehicles with 

respect to GHG emissions be set equal to the respective useful life periods for criteria 

pollutants. The agencies propose that the existing engine useful life periods44, as 

included in Table II-3, be broadened to include CO2 emissions and fuel consumption for 

both engines and tractors.

Table II-3 Tractor and Engine Useful Life Periods

Years Miles

Medium Heavy Duty Diesel 

Engines and Class 7 Tractors

10 185,000

Heavy Heavy Duty Diesel 

Engines and Class 8 Tractors

10 435,000

EPA and NHTSA request comments on the magnitude and need for an in-use 

adjustment factor for the engine standard and the compliance model (TEST) based tractor 

standard.

(2) Test Procedures and Related Issues

The agencies are proposing a complete set of test procedures to evaluate fuel 

consumption and CO2 emissions from Class 7/8 tractors and the engines installed in 

them. The test procedures related to the tractors are all new, while the engine test 

procedures build substantially on EPA’s current non-GHG emissions test procedures, 

except as noted. This section discusses the proposed simulation model developed for 

demonstrating compliance with the tractor standard and the proposed engine test 

procedures.

(a) Truck Simulation Model

We are proposing to set separate engine and vehicle-based emission standards to 

achieve the goal of reducing emissions and fuel consumption for both trucks and engines. 

For the Class 7 and 8 tractors, engine manufacturers would be subject to the engine 

standards, and Class 7 and 8 tractor manufacturers would be required to install engines in 

their tractors certified for use in the tractor. The tractor manufacturer would be subject to 

a separate vehicle-based standard that would use a proposed truck simulation model to 

evaluate the impact of the tractor cab design to determine compliance with the tractor 

standard. 

 

44 40 CFR § 86.004-2
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A simulation model, in general, uses various inputs to characterize a vehicle’s 

properties (such as weight, aerodynamics, and rolling resistance) and predicts how the 

vehicle would behave on the road when it follows a driving cycle (vehicle speed versus 

time). On a second-by-second basis, the model determines how much engine power 

needs to be generated for the vehicle to follow the driving cycle as closely as possible. 

The engine power is then transmitted to the wheels through transmission, driveline, and 

axles to move the vehicle according to the driving cycle. The second-by-second fuel 

consumption of the vehicle, which corresponds to the engine power demand to move the 

vehicle, is then calculated according to a fuel consumption map of the model. Similar to 

a chassis dynamometer test, the second-by-second fuel consumption is aggregated over 

the complete drive cycle to determine a fuel consumption of the vehicle.

NHTSA and EPA are proposing to evaluate fuel consumption and CO2 emissions 

respectively through a simulation of whole-vehicle operation, consistent with the NAS 

recommendation to use a truck model to evaluate truck performance. The agencies 

developed the Truck Efficiency Simulation Tool [TEST] for the specific purpose of this 

proposal to evaluate truck performance. The [TEST] model is similar in concept to a 

number of vehicle simulation tools developed by commercial and government entities. 

The model developed by the agencies and proposed here was designed for the express 

purpose of vehicle compliance demonstration and is therefore simpler and less 

configurable than similar commercial products. This approach gives a compact and 

quicker tool for vehicle compliance without the overhead and costs of a more 

sophisticated model. Details of the model are included in Chapter 4 of the DRIA.

[TEST] is designed to focus on the inputs most closely associated with fuel 

consumption and CO2 emissions - i.e. on those which have the largest impacts such as 

aerodynamics, rolling resistance, weight, and others. 

EPA has validated [TEST] based on the chassis test results from three SmartWay

certified tractors tested at Southwest Research Institute. The validation work conducted 

on these three vehicles is representative of the other Class 7 and 8 tractors. Many aspects 

of one tractor configuration (such as the engine, transmission, axle configuration, tire 

sizes, and control systems) are similar to those used on the manufacturer’s sister models. 

For example, the powertrain configuration of a sleeper cab with any roof height is similar 

to the one used on a day cab with any roof height. Details are included in DRIA Chapter 

4. Overall, the [TEST] model predicted the fuel consumption and CO2 emissions within 

4% of the chassis test procedure results for three test cycles – the ARB Transient cycle, 

ARB High Speed Cruise cycle, and the Low Speed Cruise cycle. These cycles are very

similar to the ones the agencies are proposing to utilize in compliance testing. Test to test 

variation for heavy-duty vehicle chassis testing can be higher than 4 percent based on 

driver variation. The proposed simulation model is described in greater detail in Chapter 

4 of the DRIA and is available for download by interested parties at 

(www.epa.gov/xxxxx). We request comment on all aspects of this approach to 

compliance determination in general and to the use of the [TEST] model in particular. 

The agencies are proposing that for demonstrating compliance, a Class 7 and 8 

tractor manufacturer would measure the performance of specified tractor systems (such 
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as aerodynamics and tire rolling resistance), input the values into [TEST], and compare 

the model’s output to the standard. The agencies propose that a tractor manufacturer 

would provide the inputs for each of following factors for each of the tractors it wished to 

certify under CO2 standards and for establishing fuel consumption values: Coefficient of 

Drag, Tire Rolling Resistance Coefficient, Weight Reduction, Vehicle Speed Limiter, and 

Extended Idle Reduction Technology. These are the technologies on which the agencies’ 

own feasibility analysis for these vehicles is predicated. An example of the [TEST] input 

screen is included in Figure II-1. The input values for the simulation model would be 

derived by the manufacturer from test procedures proposed by the agencies in this 

proposal. The agencies are proposing several testing alternatives for aerodynamic 

assessment, a single procedure for tire rolling resistance coefficient determination, and a 

prescribed method to determine tractor weight reduction. The agencies are proposing 

defined model inputs for determining vehicle speed limiter and extended idle reduction 

technology benefits. The other aspects of vehicle performance are fixed within the model 

as defined by the agencies and are not varied for the purpose of compliance.

Figure II-1: Example [TEST] Input Screen

(b) Metric

Test metrics which are quantifiable and meaningful are critical for a regulatory

program. The CO2 and fuel consumption metric should reflect what we wish to control 

(CO2 or fuel consumption) relative to the clearest value of its use: in this case, carrying 
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freight. It should encourage efficiency improvements that will lead to reductions in 

emissions and fuel consumption during real world operation. The agencies are proposing 

standards for Class 7 and 8 combination tractors that would be expressed in terms of 

moving a ton (2000 pounds) of freight over one mile. Thus, NHTSA's proposed fuel 

consumption standards for these trucks would be represented as gallons of fuel used to 

move one ton of freight 1000 miles, or gal/1000 ton-mile. EPA's proposed CO2 vehicle 

standards would be represented as grams of CO2 per ton-mile. 

The NAS panel reached the same conclusion in their report. The panel spent 

considerable time explaining the advantages of and recommending a load-specific fuel 

consumption approach to regulating the fuel efficiency of heavy duty trucks. See NAS 

Report Chapter 2 pages 2-14 through 2-21 of the report. The panel first points out that 

the nonlinear relationship between fuel economy and fuel consumption has led 

consumers of light-duty vehicles to have difficulty in judging the benefits of replacing the 

most inefficient vehicles. The panel describes an example where a light-duty vehicle can 

save the same 107 gallons per year (assuming 12,000 miles travelled per year) by 

improving one vehicle’s fuel efficiency from 14 to 16 mpg or improving another 

vehicle’s fuel efficiency from 35 to 50.8 mpg. The use of miles per gallon leads 

consumers to undervalue the importance of small mpg improvements in vehicles with 

lower fuel economy. Therefore, the NAS panel recommends the use of a fuel 

consumption metric over a fuel economy metric. The panel also describes the primary

purpose of most heavy duty vehicles as moving freight or passengers (the payload). 

Therefore, they concluded that the most appropriate way to represent an attribute-based 

fuel consumption metric is to normalize the fuel consumption to the payload.

With the approach to compliance NHTSA and EPA are proposing today, a default 

payload is specified for each of the tractor categories suggesting that a gram per mile 

metric with a specified payload and a gram per ton-mile metric would be effectively 

equivalent. The primary difference between the metrics and approaches relates to our 

treatment of mass reductions as a means to reduce fuel consumption and greenhouse gas 

emissions. In the case of a gram per mile metric, mass reductions are reflected only in 

the calculation of the work necessary to move the vehicle mass through the drive cycle. 

As such it directly reduces the gram emissions in the numerator since a vehicle with less 

mass will require less energy to move through the drive cycle leading to lower CO2

emissions. In the case of Class 7 and 8 tractors and our proposed gram/ton-mile metric, 

reductions in mass are reflected both in less mass moved through the drive cycle (the 

numerator) and greater payload (the denominator). We adjust the payload based on 

vehicle mass reductions because we estimate that approximately one third of the time the 

amount of freight loaded in a trailer is limited not by volume in the trailer but by the total 

gross vehicle weight rating of the tractor. By reducing the mass of the tractor the mass of 

the freight loaded in the tractor can go up. Based on this general approach, it can be 

estimated that for every 1200 pounds in mass reduction total truck vehicle miles traveled 

and therefore trucks on the road could be reduced by one percent. Without the use of a 

per ton-mile metric it would not be clear or straightforward for the agencies to reflect the 

benefits of mass reduction from large freight carrying vehicles that are often limited in 

the freight they carry by the gross vehicle weight rating of the truck. The agencies seek 
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comment on the use of a per ton-mile metric and also whether other metrics such as per 

cube-mile should be considered instead.

(c) Truck Aerodynamic Assessment

The aerodynamic drag of a vehicle is determined by the vehicle’s coefficient of 

drag (Cd), frontal area, air density and speed. The agencies are proposing to establish 

and use pre-defined values for the input parameters to [TEST] which represent the frontal 

area and air density, while the speed of the vehicle would be determined in [TEST] 

through the proposed drive cycles. The agencies are proposing that the manufacturer 

would determine a truck’s Cd, a dimensionless measure of a vehicle’s aerodynamics, for 

input into the model through a combination of vehicle testing and vehicle design 

characteristics. Quantifying truck aerodynamics as an input to the [TEST] presents 

technical challenges because of the proliferation of truck configurations, the lack of a 

clearly preferable standardized test method, and subtle variations in measured Cd values 

among various test procedures. Class 7/8 tractor aerodynamics are currently developed 

by manufacturers using a range of techniques, including vehicle coast down testing, wind 

tunnel testing, and computational fluid dynamics, as further discussed below. Reflecting 

that each of these approaches has limitations and no one approach appears to be superior 

to others, the agencies are proposing to allow all three aerodynamic evaluation methods

to be used in demonstrating a vehicle’s aerodynamic performance. The agencies 

welcome comments on each of these methods.

The agencies are proposing that the coefficient of drag assessment be a product of 

test data and vehicle characteristics using good engineering judgment. The primary tool 

the agencies expect to use in our own evaluation of aerodynamic performance is the coast 

down procedure described in SAE J2263. Allowing manufacturers to use multiple test 

procedures and modeling coupled with good engineering judgment to determine 

aerodynamic performance is consistent with the current approach used in determining 

representative road load forces for light-duty vehicle testing.45 The agencies anticipate 

that as we and the industry gain experience with assessing aerodynamic performance of 

HD vehicles for purposes of compliance a test-only approach may have advantages.

We believe this broad approach allowing manufacturers to use multiple different 

test procedures to demonstrate aerodynamic performance is appropriate given that no 

single test procedure is superior in all aspects to other approaches. However, we also 

recognize the need for consistency and a level playing field in evaluating aerodynamic 

performance. To accomplish this, the agencies propose to use a two-part approach that 

evaluates aerodynamic performance not only through testing but through the application 

of good engineering judgment and a technical description of the vehicles aerodynamic 

characteristics. The first part of the proposed evaluation approach uses a bin structure 

characterizing the expected aerodynamic performance of tractors based on definable 

vehicle attributes. This bin approach is described further below. The second proposed 

 

45See CFR Title 40, Part 86, Section.129-00 (e)(1).
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evaluation element uses aerodynamic testing to measure the vehicles aerodynamic 

performance under standardized conditions. The agencies expect that the SAE J2263 

coast down procedures or a constant speed vehicle test will be the primary aerodynamic 

testing tool but are interested in working with the regulated industry and other interested 

stakeholders to develop a primary test approach. Additionally, the agencies propose to 

have a process that would allow manufacturers to demonstrate that another aerodynamic 

test procedure should also be permitted for purposes of compliance with the aerodynamic 

requirements of today’s proposed rules. We are requesting comment on methods that 

should form the primary aerodynamic testing tool, methods that may be appropriate as 

alternatives, and the mechanism (including standards, practices, and unique criteria) for 

the agencies to consider allowing alternative aerodynamic test methods.

NHTSA and EPA are proposing that manufacturers use a two part screening 

approach for determining the aerodynamic inputs to the TEST model. The first part 

would require the manufacturers to assign each vehicle aerodynamic configuration to one 

of five aerodynamics bins created by EPA and NHTSA as described below. The 

assignment by bin reflects the aerodynamic characteristics of the vehicle. For each bin, 

EPA and NHTSA have already defined a nominal Cd that will be used in the TEST 

model and a range of Cd values that would be expected from testing of vehicles meeting 

this bin description. The second part would require the manufacturer to then compare its 

own test results of aerodynamic performance (as conducted in accordance with the 

agencies’requirements) for the vehicle to confirm the actual aerodynamic performance 

was consistent with the agencies’ expectations for vehicles within this bin. If the 

predicted performance and actual observed performance match, the Cd value as an input 

for the TEST model is the nominal Cd value defined for the bin. If however, a 

manufacturer’s test data demonstrates performance that is better than projected for the 

assigned bin a manufacturer may use the test data and good engineering judgment to 

demonstrate to the agencies that this particular vehicle’s performance is in keeping with 

the performance level of a more aerodynamic bin and with the agencies’ permission may

use the Cd value of the more aerodynamic bin. Conversely, if the test data demonstrates 

that the performance is worse than the projected bin, then the manufacturer would use the

Cd value from the less aerodynamic bin. Using this approach, the bin structure can be 

seen as the agencies’ first effort to create a common measure of aerodynamic 

performance to benchmark the various test methods manufacturers may use to 

demonstrate aerodynamic performance. For example, if a manufacturers test methods 

consistently produce Cd values that are better than projected by the agencies, EPA and 

NHTSA can use this information to further scrutinize the manufacturer’s test procedure, 

helping to ensure that all manufacturers are competing on a level playing field. 

The agencies are proposing aerodynamic technology bins which divide the wide 

spectrum of tractor aerodynamics into five categories. The first category, “Classic,” 

represents tractor bodies which prioritize appearance or special duty capabilities over 

aerodynamics. The Classic trucks incorporate few, if any, aerodynamic features and may 

have several features which detract from aerodynamics, such as bug deflectors, custom 

sunshades, b-pillar exhaust stacks, and others. The second category for aerodynamics is 

the “Conventional” tractor body. The agencies consider Conventional tractors to be the 

average new tractor today which capitalizes on a generally aerodynamic shape and avoids 
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classic features which increase drag. Tractors within the “SmartWay” category build on 

Conventional tractors with added components to reduce drag in the most significant areas 

on the tractor, such as fully enclosed roof fairings, side extending gap reducers, fuel tank 

fairings, and streamlined grill/hood/mirrors/bumpers. The “Advanced SmartWay” 

aerodynamic category builds upon the SmartWay tractor body with additional 

aerodynamic treatments such as underbody airflow treatment, down exhaust, and lowered 

ride height. And finally, “Advanced SmartWay II” tractors incorporate advanced 

technologies which are currently in the prototype stage of development, such as advanced 

gap reduction, rearview cameras to replace mirrors, wheel system streamlining, and 

advanced body designs. The agencies recognize that these proposed aerodynamic bins 

are static and referential and that there may be other technologies that may provide 

similar aerodynamic benefit. In addition, it is expected that aerodynamic equipment will 

advance over time and the agencies may find it appropriate and necessary to revise the 

bin descriptions.

Under this proposal, the manufacturer would then input into [TEST] the Cd value 

specified for each bin as also defined in Table II-4Error! Reference source not 

found.Error! Reference source not found.. For example, if a manufacturer tests a 

Class 8 sleeper cab high roof tractor with features which are similar to a SmartWay

tractor and the test produces a Cd value of 0.59, then the manufacturer would assign this 

tractor to the Class 8 Sleeper Cab High Roof SmartWay bin. The manufacturer would 

then use the Cd value of 0.60 as the input to [TEST]. 

Table II-4: Aerodynamic Input Definitions to [TEST]

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low 

Roof

High 

Roof

Low 

Roof

High 

Roof

Low 

Roof

Mid 

Roof

High 

Roof

Aerodynamics Test Results (Cd)

Classic ≥0.83 ≥0.73 ≥0.83 ≥0.73 ≥0.83 ≥0.78 ≥0.73

Conventional 0.78-

0.82

0.63-

0.72

0.78-

0.82

0.63-

0.72

0.78-

0.82

0.73-

0.77

0.63-

0.72

SmartWay 0.73-

0.77

0.58-

0.62

0.73-

0.77

0.58-

0.62

0.73-

0.77

0.68-

0.72

0.58-

0.62

Advanced SmartWay 0.68-

0.72

0.53-

0.57

0.68-

0.72

0.53-

0.57

0.68-

0.72

0.63-

0.67

0.53-

0.57

Advanced SmartWay

II

≤0.67 ≤0.52 ≤0.67 ≤0.52 ≤0.67 ≤0.62 ≤0.52

Aerodynamic Input to [TEST] (Cd)

Frontal Area (m2) 6.0 9.8 6.0 9.8 6.0 6.6 9.8

Classic 0.85 0.75 0.85 0.75 0.85 0.80 0.75

Conventional 0.80 0.68 0.80 0.68 0.80 0.75 0.68

SmartWay 0.75 0.60 0.75 0.60 0.75 0.70 0.60

Advanced SmartWay 0.70 0.55 0.70 0.55 0.70 0.65 0.55
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Advanced SmartWay

II

0.65 0.50 0.65 0.50 0.65 0.60 0.50

Coefficient of drag (Cd) and frontal area of the tractor-trailer combination go 

hand-in-hand to determine the force required to overcome aerodynamic drag. As 

explained above, the agencies are proposing that the Cd value is one of the [TEST] inputs 

which will be derived by the manufacturer. However, the agencies are proposing to 

specify the truck’s frontal area for each regulatory category (i.e. each of the seven 

subcategories which are proposed and listed in Table II-4Error! Reference source not 

found.Error! Reference source not found. under the Aerodynamic Input to [TEST]). 

The frontal area of a high roof tractor pulling a box trailer will be determined primarily

by the box trailer’s dimensions and the ground clearance of the tractor. The frontal area 

of low and mid roof tractors will be determined by the tractor itself. An alternate 

approach to the proposed frontal area specification is to create the aerodynamic input 

table (as shown in Table II-4Error! Reference source not found.Error! Reference 

source not found.) with values that represent the Cd multiplied by the frontal area. This 

approach will provide the same aerodynamic load, but it will not allow the comparison of 

aerodynamic efficiency across regulatory categories that can be done with the Cd values 

alone. The agencies are interested in comments regarding the frontal area of trucks, 

specifically whether the specified frontal areas are appropriate and whether the use of 

standard frontal areas may have unanticipated consequences.

EPA and NHTSA recognize that wind conditions, most notably wind direction, 

have a greater impact on real world CO2 emissions and fuel consumption of heavy duty 

trucks than of light-duty vehicles. As noted in the NAS report46, the wind average drag 

coefficient is about 15 percent higher than the zero degree coefficient of drag (Cd). The 

agencies considered proposing the use of a wind averaged drag coefficient in this 

regulatory program, but ultimately decided to propose using coefficient of drag values 

which represent zero yaw (i.e., representing wind from directly in front of the vehicle, not 

from the side) instead. We are taking this approach recognizing that wind tunnels are 

currently the only tool to accurately assess the influence of wind speed and direction on a 

truck’s aerodynamic performance. The agencies recognize, as NAS did, that the results 

of using the zero yaw approach may result in fuel consumption predictions that are offset 

slightly from real world performance levels, not unlike the offset we see today between 

fuel economy test results in the CAFE program and actual fuel economy performance 

observed in-use. We believe this approach will not impact technology effectiveness or 

change the kinds of technology decisions made by the tractor manufacturers in 

developing equipment to meet our proposed standards. However, the agencies are 

interested in receiving comment on approaches to develop wind averaged coefficient of 

drag values including CFD, coast down, and constant speed test procedures.

The methodologies the agencies are considering for aerodynamic assessment 

include coast down testing, wind tunnel testing, and computational fluid dynamics. The 

 

46 See 2010 NAS Report, Finding 2-4 on page 2-40.
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agencies welcome information on a constant speed test procedure and how it could be 

applied to determine aerodynamic drag.

(i) Coast Down Testing

The coast down test procedure has been used extensively in the light-duty

industry to capture the road load force by coasting a vehicle along a flat straightaway

under a set of prescribed conditions. Coast down testing has been used less extensively

to obtain road load forces for medium- and heavy-duty vehicles. EPA has conducted a 

significant amount of test work to demonstrate that coast down testing per SAE J2263 

produces reasonably repeatable test results for Class 7 and 8 tractor / trailer pairings, as 

described in DRIA Chapter 3. The agencies propose that a manufacturer which chooses 

this method would determine a tractor’s Cd value through analysis of the road load force 

equation derived from SAE J2263 Revised 2008-12 test results, as proposed in 40 CFR 

1066.210. 

(ii) Wind Tunnel Testing

A wind tunnel provides a stable environment yielding a more repeatable test than 

coast down. This allows the manufacturer to run multiple baseline vehicle tests and 

explore configuration modifications for nearly the same effort (e.g., time and cost) as 

conducting the coast down procedure. In addition, wind tunnels provide testers with the 

ability to yaw the vehicle at positive and negative angles relative to the original centerline 

of the vehicle to accurately capture the influence of non-uniform wind direction on the 

Cd (e.g., wind averaged Cd). 

The agencies propose to allow the use of existing SAE wind tunnel procedures 

with some minor modifications as discussed in Section V of this proposal. The agencies 

seek comments on the appropriateness of using the existing SAE wind tunnel procedures, 

and the modifications to these procedures, for this regulatory purpose.

(iii) Computational Fluid Dynamics

Computational Fluid Dynamics, or CFD, capitalizes on today’s computing power 

by modeling a full size vehicle and simulating the flows around this model to examine 

the fluid dynamic properties, in a virtual environment. CFD tools are used to solve the 

Navier-Stokes equations that follow physical law of conservation of momentum and 

govern fluid dynamics and flow relationship around a body in motion or a static body 

with fluid in motion around it. CFD analysis involves several steps: defining the model 

structure or geometry based on provided specifications to define the basic model shape, 

applying a closed surface around the structure to define the external model shape 

(wrapping or surface meshing), dividing the control volume, including the model and the 

surrounding environment, up into smaller, discreet shapes (gridding), defining the flow 

conditions in and out of the control volume and the flow relationships within the grid 

(including eddies and turbulence), and solving the flow equations based on the prescribed 

flow conditions and relationships.
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This approach can be beneficial to manufacturers since they can rapidly prototype 

(e.g., design, research, and model) an entire vehicle without investing in material costs; 

they can modify and investigate changes easily; and the data files can be re-used and 

shared within the company or with corporate partners. 

The accuracy of the outputs from CFD analysis is highly dependent on the inputs. 

The CFD modeler decides what method to use for wrapping, how fine the mesh cell and 

grid size should be, and the physical and flow relationships within the environment. A 

balance must be achieved between the number of cells, which defines how fine the mesh 

is, and the computational times for a result (i.e., solution-time-efficiency). All of these 

decisions affect the results of the CFD aerodynamic assessment.

Because CFD modeling is dependent on the quality of the data input and the 

design of the model, the agencies seek comment on a minimum set of criteria applicable 

to using CFD for aerodynamic assessment in Section V. Further, we are proposing a 

requirement to correlate CFD aerodynamic assessments with experimental results from 

either or both the coast down procedure and wind tunnel testing. This will allow the use 

of CFD and the design freedom that it offers while ensuring that, regardless of the 

decisions made during the process, the CFD aerodynamic assessment accurately

simulates real-world aerodynamics.

(d) Tire Rolling Resistance Assessment

NHTSA and EPA are proposing that the tractor’s tire rolling resistance input to 

the [TEST] model be determined using the ISO 28580:2009 test method.47 The agencies 

believe the ISO test procedure is appropriate to propose for this program because the 

procedure is the same one used by NHTSA in its fuel efficiency tire labeling program48

and is consistent with the direction being taken by the tire industry both in the United 

States and Europe. The rolling resistance from this test would be used to specify the 

rolling resistance of each tire on the steer and drive axle of the vehicle. The results would 

be expressed as a rolling resistance coefficient and measured as kilogram per metric ton 

(kg/metric ton). The agencies are proposing that three tire samples within each tire 

model be tested to account for some of the production variability and the average of the 

three tests would be the rolling resistance coefficient for the tire. The [TEST] model 

would use a combined tire rolling resistance, where 15 percent of the gross weight of the 

truck and trailer would be distributed to the steer axle, 42.5 percent to the drive axles, and 

42.5 percent to the trailer axles.49 The trailer tires’ rolling resistance would be prescribed 

by the agencies as part of the standardized trailer used for demonstrating compliance at 6 

 

47 ISO, 2009, Passenger Car, Truck, and Bus Tyres – Methods of Measuring Rolling Resistance – Single 

Point Test and Correlation of Measurement Results: ISO 28580:2009(E), First Edition, 2009-07-01

48 NHTSA, 2009. “NHTSA Tire Fuel Efficiency Consumer Information Program Development: Phase 1 –

Evaluation of Laboratory Test Protocols.” DOT HS 811 119. June. (www.regulations.gov, Docket ID: 

NHTSA-2008-0121-0019).

49 This distribution is equivalent to the federal over-axle weight limits for an 80,000 GVWR 5-axle tractortrailer: 12,000 pounds over the steer axle, 34,000 pounds over the tandem drive axles (17,000 pounds per 

axle) and 34,000 pounds over the tandem trailer axles (17,000 pounds per axle). 
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kg/metric ton, which was the average trailer tire rolling resistance measured during the 

SmartWay tire testing.50 

We acknowledge that the useful life of original equipment tires used on tractors is 

shorter than the tractor’s useful life. In this proposal, we are treating the tires as if the 

owner replaces the tire with tires that match the original equipment. Some owners opt for 

the original tires under the assumption that this is the best product. However, tractor tires 

are often retreaded or replaced. Steer tires on a highway tractor might need replacement 

after 75,000 to 150,000 miles. Drive tires might need retreading or replacement after 

150,000 to 300,000 miles. Of course, tire removal miles can be much higher or lower, 

depending upon a number of factors that affect tire removal miles. These include the 

original tread depth; desired tread depth at removal to maintain casing integrity; tire 

material and construction; typical load; tire “scrub” due to urban driving and set back 

axles; and, tire underinflation. Since it is common for both medium and heavy duty truck 

tires to be replaced and retreaded, we welcome comments in this area. We are 

specifically seeking data for the rolling resistance of retread and replacement heavy duty

tires and the typical useful life of tractor tires. 

(e) Weight Reduction Assessment

EPA and NHTSA are seeking to account for the emissions and fuel consumption 

benefits of weight reduction as a control technology in heavy duty trucks. Weight 

reduction impacts the emissions and fuel consumption performance of tractors in 

different ways depending on the truck’s operation. For trucks that cube-out, the weight 

reduction will show a small reduction in grams of CO2 emitted or fuel consumed per mile 

travelled. The benefit is small because the weight reduction is minor compared to the 

overall weight of the combination truck and payload. However, a weight reduction in 

tractors which operate at maximum gross vehicle weight rating would result in an 

increase in payload capacity. Increased vehicle payload without increased GVWR 

significantly reduces fuel consumption and CO2 emissions per ton mile of freight 

delivered. It also leads to fewer vehicle miles driven with a proportional reduction in 

traffic accidents. 

The empty curb weight of tractors varies significantly today. Items as common as 

fuel tanks can vary between 50 and 300 gallons each for a given truck model. 

Information provided by truck manufacturers indicates that there may be as much as a 

5,000 to 17,000 pound difference in curb weight between the lightest and heaviest 

tractors within a regulatory subcategory (such as Class 8 sleeper cab with a high roof). 

Because there is such a large variation in the baseline weight among trucks that perform 

roughly similar functions with roughly similar configurations, there is not an effective 

way to quantify the exact CO2 and fuel consumption benefit of mass reduction using 

[TEST] because of the difficulty in establishing a baseline. However, if the weight 

reduction is limited to tires and wheels, then both the baseline and weight differentials for 

 

50 US Environmental Protection Agency. SmartWay Transport Partnership July 2010 e-update accessed 

July 16, 2010, from http://www.epa.gov/smartwaylogistics/newsroom/documents/e-update-july-10.pdf
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these are readily quantifiable and well-understood. Therefore, the agencies are proposing 

that the mass reduction that would be simulated be limited only to reductions in wheel 

and tire weight. The agencies of course still encourage each OEM to reduce tractor curb 

weight generally in as many other ways as possible, which would reduce fuel 

consumption and GHG emissions independent of the degree to which such improvements 

are recognized for fuel consumption and CO2 compliance purposes. In the context of this 

heavy duty vehicle program with only changes to tires and wheels, the agencies do not 

foresee any related impact on safety.

51

 The agencies welcome comments regarding this 

approach and detailed data to further improve the robustness of the agencies’ assumed 

baseline truck curb weights for each regulatory category used within the model, as 

outlined in DRIA Chapter 3. 

EPA and NHTSA are proposing to specify the baseline vehicle weight for each 

regulatory category (including the tires and wheels), but allow manufacturers to quantify

weight reductions based on the wheel material selection and single wide versus dual tires 

per Table II-5. The agencies assume the baseline wheel and tire configuration contains 

dual tires with steel wheels because these represent the vast majority of new vehicle 

configurations today. The proposed weight reduction due to the wheels and tires would 

be reflected in the payload tons by increasing the specified payload by the weight 

reduction amount discounted by two thirds to recognize that approximately one third of 

the truck miles are travelled at maximum payload, as discussed above in the payload 

discussion. 

Table II-5: Proposed Weight Reduction Values

Weight Reduction Technology Weight Reduction 

(kg per tire/wheel)

Single Wide Drive

Tire with ...

Steel Wheel 38

Aluminum Wheel 63

Light Weight Aluminum 

Wheel

67

Steer Tire or Dual 

Wide Drive Tire with 

...

High Strength Steel Wheel 4

Aluminum Wheel 10

Light Weight Aluminum 

Wheel

14

(f) Extended Idle Reduction Technology Assessment

Extended idling from Class 8 heavy duty line haul trucks contributes to significant 

CO2 emissions and fuel consumption in the United States. The Federal Motor Carrier 

Safety Administration regulations require a certain amount of driver rest for a 

 

51 For more information on the estimated safety effects of this proposed rule, see Chapter 9 of the draft 

RIA.
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corresponding period of driving hours.

52

 Extended idle occurs when Class 8 long haul 

drivers rest in the sleeper cab compartment during rest periods as drivers find it both 

convenient and less expensive to rest in the truck cab itself than to pull off the road and 

find accommodations. During this rest period a driver will idle the truck in order to 

provide heating or cooling or run on-board appliances. In some cases the engine can idle 

in excess of 10 hours. During this period, the truck will consume approximately 0.8 

gallons of fuel and emit over 8,000 grams of CO2 per hour. An average truck can 

consume 8 gallons of fuel and emit over 80,000 grams of CO2 during overnight idling in 

such a case. 

Idling reduction technologies are available to allow for driver comfort while 

reducing fuel consumptions and CO2 emissions. Auxiliary power units, fuel operated 

heaters, battery supplied air conditioning, and thermal storage systems are among the 

technologies available today. The agencies are proposing to include extended idle 

reduction technology as an input to the [TEST] model for Class 8 sleeper cabs. The 

manufacturer would input the value based on the idle reduction technology installed on 

the truck. As discussed further in Section III, if a manufacturer chooses to use idle 

reduction technology to meet the standard, then it would require an automatic main 

engine shutoff after 5 minutes to help ensure the idle reductions are realized in-use. As 

with all of the technology inputs discussed in this section, the agencies are not mandating 

the use of idle reductions or idle shutdown, but rather allowing their use as one part of a 

suite of technologies feasible for reducing fuel consumption and meeting the proposed 

standards. The proposed value (5 g CO2/ton-mile or 0.5 gal/1000 ton-mile) for the idle 

reduction technologies was determined using an assumption of 1,800 idling hours per 

year, 125,000 miles travelled, and a baseline idle fuel consumption of 0.8 gallons per 

hour. Additional detail on the emission and fuel consumption reduction values are 

included in DRIA Chapter 2.

(g) Vehicle Speed Limiters

Fuel consumption and CO2 emissions increase proportional to the square of 

vehicle speed.53 Therefore, lowering vehicle speeds can significantly reduce fuel 

consumption and GHG emissions. A vehicle speed limiter, which limits the vehicle's 

maximum speed, is a simple technology that is utilized today. The feature is 

electronically programmed and controlled. Manufacturers today sell trucks with vehicle 

speed limiters and allow the customers to set the limit. However, as proposed the [TEST] 

model will not provide a fuel consumption reduction for a limiter that can be overridden. 

In order to obtain a benefit for the program, the manufacturer must preset the limiter in 

such a way that the setting will not be capable of being easily overridden by the fleet or 

the owner. As with other engine calibration aspects of emission controls, tampering with 

a calibration would be considered unlawful by EPA. If the manufacturer installs a 

 

52 Federal Motor Carrier Safety Administration. Hours of Service Regulations. Last accessed on August 2, 

2010 at http://www.fmcsa.dot.gov/rules-regulations/topics/hos/

53 NAS Report. Page 2-22. Road Load Force Equation defines the aerodynamic portion of the road load as 

1⁄2 * Coefficient of Drag * Frontal Area * air density * vehicle speed squared.
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vehicle speed limiter into a truck that is not easily overridden, then the manufacturer 

would input the vehicle speed limit setpoint into [TEST] model. 

(h) Defined Vehicle Configurations in the [TEST] model

As discussed above, the agencies are proposing methodologies that manufacturers 

would use to quantify the values to be input into the [TEST] for these factors affecting 

truck efficiency: Coefficient of Drag, Tire Rolling Resistance Coefficient, Weight 

Reduction, Vehicle Speed Limiter, and Extended Idle Reduction Technology. The other 

aspects of vehicle performance are fixed within the model and are not varied for the 

purpose of compliance. The defined inputs being proposed include the drive cycle, 

tractor-trailer combination curb weight, payload, engine characteristics, and drivetrain for 

each vehicle type, and others. We are seeking comments accompanied with data on the 

defined model inputs as described in draft RIA Chapter 3.

(i) Vehicle Drive Cycles

As noted by the March 2010 NAS Report,54 the choice of a drive cycle used in 

compliance testing has significant consequences on the technology that will be employed 

to achieve a standard as well as the ability of the technology to achieve real world 

reductions in emissions and improvements in fuel consumption. Manufacturers naturally 

will design vehicles to ensure they satisfy regulatory standards. If the agencies propose 

an ill-suited drive cycle for a regulatory category, it may encourage GHG emissions and 

fuel consumption technologies which satisfy the test but do not achieve the same benefits 

in use. For example, requiring all trucks to use a constant speed highway drive cycle will 

drive significant aerodynamic improvements. However, in the real world a combination 

tractor used for local delivery may spend little time on the highway, reducing the benefits 

that would be achieved by this technology. In addition, the extra weight of the 

aerodynamic fairings will actually penalize the GHG and fuel consumption performance 

in urban driving and may reduce the freight carrying capability. The unique nature of the 

kinds of CO2 emissions control and fuel consumption technology means that the same 

technology can be of benefit during some operation but cause a reduced benefit under 

other operation.55 To maximize the GHG emissions and fuel consumption benefits and 

avoid unintended reductions in benefits, the drive cycle should focus on promoting 

technology that produces benefits during the primary operation modes of the application. 

Consequently, drive cycles used in GHG emissions and fuel consumption compliance 

testing should reasonably represent the primary actual use, notwithstanding that every

truck has a different drive cycle in-use. 

 

54 March 2010 NAS Report, Chapters 4 and 8.

55

 This situation does not typically occur for heavy-duty emission control technology designed to control 

criteria pollutants such as PM and NOx.
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The agencies are proposing a modified version of the California Air Resource 

Board (ARB) Heavy Heavy Duty Truck 5 Mode Cycle56, using the basis of three of the 

cycles which best mirror Class 7 and 8 combination truck driving patterns, based on 

information from MOVES.57 The key advantage of ARB 5 mode cycle is that it provides 

the flexibility to use several different modes and weight the modes to fit specific truck 

application usage patterns. EPA analyzed the five cycles and found that some 

modifications to the modes appear to be needed to allow sufficient flexibility in 

weightings. The agencies are proposing the use of the Transient mode, as defined by 

ARB, because it broadly covers urban driving. The agencies are also proposing altered 

versions of the High Speed Cruise and Low Speed Cruise modes which would reflect 

only constant speed cycles at 65 mph and 55 mph respectively. EPA and NHTSA relied 

on the EPA MOVES analysis of Federal Highway Administration data to develop the 

proposed mode weightings to characterize typical operations of heavy duty trucks, per 

Table II-6 below.58 A detailed discussion of drive cycles is included in DRIA Chapter 

4.59

Table II-6: Drive Cycle Mode Weightings

Transient 55 mph Cruise 65 mph Cruise

Day Cabs 19% 17% 64%

Sleeper Cabs 5% 9% 86%

(ii) Empty Weight and Payload

The total weight of the tractor-trailer combination is the sum of the tractor curb 

weight, the trailer curb weight, and the payload. The total weight of a truck is important 

because it in part determines the impact of technologies, such as rolling resistance, on 

GHG emissions and fuel consumption. The agencies are proposing to specify each of 

these aspects of the vehicle. The agencies developed the proposed tractor curb weight 

inputs from actual tractors weights measured in two of EPA’s test programs and based on 

 

56 California Air Resources Board. Heavy Heavy Duty Diesel Truck chassis dynamometer schedule, 

Transient Mode. Last accessed on August 2, 2010 at 

http://www.dieselnet.com/standards/cycles/hhddt.html

57 EPA’s MOVES (Motor Vehicle Emission Simulator). See 

http://www.epa.gov/otaq/models/moves/index.htm for additional information.

58 The Environmental Protection Agency. Draft MOVES2009 Highway Vehicle Population and Activity 

Data. EPA-420-P-09-001, August 2009 http://www.epa.gov/otaq/models/moves/techdocs/420p09001.pdf

59 In the light-duty vehicle rule, EPA and NHTSA based compliance with tailpipe standards on use of the 

FTP and HFET, and declined to use alternative tests. See 75 FR at 25407. NHTSA is mandated to use the 

FTP and HFET tests for CAFE standards, and all relevant data was obtained by FTP and HFET testing in 

any case. Id. Neither of these constraints exist for class 7-8 tractors. The little data which exist on current 

performance are principally measured by the ARB Heavy Heavy Duty Truck 5 Mode Cycle testing, and 

NHTSA is not mandated to use the FTP to establish heavy duty fuel economy standards. See 49 USC 

section 32902 (k)(2) authorizing NHTSA, among other things, to adopt and implement appropriate “test 

methods, measurement metrics, ... and compliance , protocols”.
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information from the manufacturers. The proposed trailer curb weight inputs were 

derived from actual trailer weight measurements conducted by EPA and weight data 

provided to ICF by the trailer manufacturers.60 The proposed payloads, as described 

above, are 25,000 pound for a Class 7 tractor and 38,000 pounds for a Class 8 tractor. 

Details of the individual weight inputs by regulatory category are included in DRIA 

Chapter 4.

There are several methods that the agencies have considered for evaluating the 

GHG emissions and fuel consumption of tractors used to carry freight. A key factor in 

these methods is the weight of the truck that is assumed for purposes of the evaluation. 

In use, trucks operate at different weights at different times during their operations. The 

greatest freight transport efficiency (the amount of fuel required to move a ton of 

payload) would be achieved by operating trucks at the maximum load for which they are 

designed all of the time. However, logistics such as delivery demands which require that 

trucks travel without full loads, the density of payload, and the availability of full loads of 

freight limit the ability of trucks to operate at their highest efficiency all the time. M.J. 

Bradley analyzed the Truck Inventory and Use Survey and found that approximately 9 

percent of combination truck miles travelled empty, 61 percent are “cubed-out” (the 

trailer is full before the weight limit is reached), and 30 percent are “weighed out” 

(operating weight equal 80,000 pounds which is the gross vehicle weight limit on the 

Federal Interstate Highway System or greater than 80,000 pounds for vehicles traveling 

on roads outside of the interstate system).61 The Federal Highway Administration 

developed Truck Payload Equivalent Factors to inform the development of highway

system strategies using Vehicle Inventory and Use Survey (VIUS) and Vehicle Travel 

Information System (VTRIS) data. Their results found that the average payload of a 

Class 8 truck ranged from 36,247 to 40,089 pounds, depending on the average distance 

travelled per day.

62

 The same results found that Class 7 trucks carried between 18,674 

and 34,210 pounds of payload also depending on average distance travelled per day. 

As described above, the amount of payload that a tractor can carry depends on the 

category (or GVWR) of the vehicle. For example, a typical Class 7 tractor can carry less 

payload than a Class 8 tractor. The agencies are proposing to prescribe a fixed payload 

of 25,000 pounds for Class 7 tractors and 38,000 pounds for Class 8 tractors for their 

respective test procedures. The agencies are proposing a common payload for Class 8 day

cabs and sleeper cabs because the data available does not distinguish based on type of 

Class 8 tractor. These payload values represent a heavily loaded trailer, but not 

 

60 ICF International. Investigation of Costs for Strategies to Reduce Greenhouse Gas Emissions for HeavyDuty On-road Vehicles. July 2010. Pages 4-15.

61 M.J. Bradley & Associates. Setting the Stage for Regulation of Heavy-Duty Vehicle Fuel Economy and 

GHG Emissions: Issues and Opportunities. February 2009. Page 35. Analysis based on 1992 Truck 

Inventory and Use Survey data, where the survey data allowed developing the distribution of loads instead 

of merely the average loads.

62 The U.S. Federal Highway Administration. Development of Truck Payload Equivalent Factor. Table 11. 

Last viewed on March 9, 2010 at 

http://ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports9/s510_11_12_tables.htm
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maximum GVWR, since as described above the majority of tractors "cube-out" rather 

than "weigh-out.” The proposed payloads are based on the average payload developed 

by the Federal Highway Administration Truck Payload Equivalent Factor for Class 7 and 

Class 8 trucks.63 Additional details on proposed payloads are included in DRIA Chapter 

3.

(iii) Standardized Trailers

NHTSA and EPA are proposing that the tractor performance in the [TEST] model 

will be judged by assuming it is pulling a standardized trailer. The agencies believe that 

an assessment of the tractor aerodynamics should be conducted using a tractor-trailer 

combination to reflect the impact of aerodynamic technologies in actual use, where 

tractors are designed and used with a trailer. Assessing the tractor aerodynamics using 

only the tractor would not be a reasonable way to assess in-use impacts. For example, the 

in-use aerodynamic drag while pulling a trailer is different than without the trailer and the 

full impact of an aerodynamic technology on reducing emissions and fuel consumption 

would not be reflected if the assessment is performed on a tractor without a trailer.

In addition to assessing the tractor with a trailer, it is appropriate to adopt a 

standardized trailer used for testing, and to vary the standardized trailer by the regulatory

category. This is similar to the standardization of payload discussed above, as a way to 

reasonably reflect in-use operating conditions. High roof tractors are optimally designed 

to pull box trailers. The roof fairing on a tractor is the feature designed to minimize the 

height differential between the tractor and typical trailer to reduce the air flow disruption. 

Low roof tractors are designed to carry flat bed or low-boy trailers. Mid roof tractors are 

designed to carry tanker and bulk carrier trailers. The agencies conducted a survey of 

tractor-trailer pairing in-use to evaluate the representativeness of this premise. The 

survey of over 3,000 tractor-trailer combinations found that in 95 percent of the 

combination trucks the tractor’s roof height was paired appropriately for the type of 

trailer that it was pulling.64 The agencies also have evaluated the impact of pairing a low 

roof tractor with a box trailer in coast down testing and found that the aerodynamic force 

increases by 50 percent over a high roof tractor pulling the same box trailer.65 Therefore, 

drivers have a large incentive to use the appropriate matching to reduce their fuel costs. 

However, the agencies recognize that in operation tractors sometimes pull trailers other 

than the type that it was designed to carry. The agencies are proposing the matching of 

trailers to roof height for the test procedure. To do otherwise would necessarily result in a 

standard reflecting substandard aerodynamic performance, and thereby result in standards 

which are less stringent than would be appropriate based on the reasonable assumption 

that tractors will generally pair with trailer of appropriate roof height. The other aspects 

 

63 The U.S. Federal Highway Administration. Development of Truck Payload Equivalent Factor. Table 11. 

Last viewed on March 9, 2010 at 

http://ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports9/s510_11_12_tables.htm

64 U.S. EPA. Truck and Trailer Roof Height Match Analysis Memo to Docket. Docket #

65 See DRIA Chapter 2 for additional detail.
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of the test procedure such as empty trailer weight, location of payload, and tractor-trailer 

gap are being proposed for each regulatory category to provide consistent test procedures.

(iv) Standardized Drivetrain

The agencies’ assessment of the current vehicle configuration process at the truck 

dealer’s level is that the truck companies provide tools to specify the proper drivetrain 

matched to the buyer’s specific circumstances. These dealer tools allow a significant 

amount of customization for drive cycle and payload to provide the best specification for 

the customer. The agencies are not seeking to disrupt this process. Optimal drivetrain 

selection is dependent on the engine, drive cycle (including vehicle speed and road 

grade), and payload. Each combination of engine, drive cycle, and payload has a single 

optimal transmission and final drive ratio. The agencies are proposing to specify the 

engine’s fuel consumption map, drive cycle, and payload; therefore, it makes sense to 

also specify the drivetrain that matches. 

(v) Engine Input to [TEST]

As the agencies are proposing separate engine and tractor standards, the [TEST] 

model will be used to assess the compliance of the tractor with the tractor standard. To 

maintain the separate assessments, the agencies are proposing to define the engine 

characteristics used in [TEST], including the fuel consumption map which provides the 

fuel consumption at hundreds of engine speed and torque points. If the agencies did not 

standardize the fuel map, then a tractor that uses an engine with emissions and fuel 

consumption better than the standards would require fewer vehicle reductions than those 

technically feasible reductions being proposed. The agencies are proposing two distinct 

fuel consumption maps for use in [TEST]. EPA proposes the first fuel consumption map 

would be used in [TEST] for the 2014 through 2016 model years and represent an 

average engine which meets the 2014 model year engine CO2 emissions standards. 

NHTSA proposes to use the same fuel map for its voluntary opt-in in the 2014 and 2015 

model years, as well as its mandatory program in the 2016 model year. The agencies are 

proposing two distinct fuel consumption maps for use in [TEST]. The first fuel 

consumption map would be used in [TEST] for the 2014 through 2016 model years and 

represent an engine which meets the 2014 model year engine CO2 emissions standards.

A second fuel consumption map would be used beginning in 2017 model year and 

represents an engine which meets the 2017 model year CO2 emissions and fuel 

consumption standards and accounts for the increased stringency in the proposed MY 

2017 standard. Effectively there is no change in stringency of the tractor vehicle (not 

including the engine) and there is stability in the tractor vehicle (not including engine) 

standards for the full rulemaking period.66 These inputs are appropriate given the 

separate proposed regulatory requirement that Class 7/8 combination tractor 

manufacturers use only certified engines.

 

66 As noted earlier, use of the 2017 model year fuel consumption map as a [TEST] input results in 

numerically more stringent proposed vehicle standards for MY 2017.
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(i) Engine Test Procedure

The NAS panel did not specifically discuss or recommend a metric to evaluate the 

fuel consumption of heavy duty engines. However, as noted above they did recommend 

the use of a load specific fuel consumption metric for the evaluation of vehicles.67 An 

analogous metric for engines would be the amount of fuel consumed per unit of work. 

Thus, EPA is proposing that GHG emission standards for engines under the CAA would 

be expressed as grams of emissions per brake horsepower-hour (g/bhp-hr); NHTSA's 

proposed fuel consumption standards under EISA, in turn, would be represented as 

gallons of fuel per 100 horsepower-hour (gal/100 bhp-hr). This metric is also consistent 

with EPA’s current standards for non-GHG emissions for these engines.

EPA’s criteria pollutant standards for engines require that manufacturers 

demonstrate compliance over a transient test cycle, the FTP; a steady-state test cycle, the 

SET or supplemental emissions test; and the not-to-exceed, or NTE test. EPA created 

this multi-layered approach to criteria emissions control in response to engine designs 

that optimized operation for lowest fuel consumption at the expense of very high criteria 

emissions when operated off the regulatory cycle. EPA’s use of multiple test procedures 

for criteria pollutants helps to ensure that manufacturers calibrate engine systems for 

compliance under all operating conditions. With regard to GHG and fuel consumption 

control, the agencies believe it is more appropriate to set standards based on a single test 

procedure, either the FTP or SET, depending on the primary expected use of the engine. 

For engines used primarily in line-haul combination tractor trailer operations, we believe 

the steady-state SET procedure more appropriately reflects in-use engine operation. By

setting standards based on the most representative test cycle, we can have confidence that 

OEMs will design engines for the best GHG and fuel consumption performance relative 

to the most common type of expected engine operation. There is no incentive to design 

the engines to give worse fuel consumption under other types of operation, relative to the 

most common type of operation, and we are not concerned if manufacturers further 

calibrate these designs to give better in-use fuel consumption during other operation,

while maintaining compliance with the criteria emissions standards as such calibration is 

entirely consistent with the goals of our joint program.

Further, we are concerned that setting standards based on both transient and 

steady-state operating conditions for all engines could lead to undesirable outcomes. For 

example, turbocompounding is one technology that the agencies have identified as a 

likely approach for compliance against our proposed HHD SET standard described 

below. Turbocompounding is a very effective approach to lower fuel consumption under 

steady driving conditions typified by combination tractor trailer operation and is well 

reflected in testing over the SET test procedure. However, when used in driving typified 

by transient operation as we expect for vocational trucks and as is represented by the 

FTP, turbocompounding shows very little benefit. Setting an FTP-based standard only 

for engines intended for use in combination tractor trailers could lead manufacturers to 

 

67 See NAS Report, Note (#), at page 2-40.
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not apply turbocompounding because the full benefits are not demonstrated on the FTP 

even though it can be a highly cost-effective means to reduce GHG emissions and lower 

fuel consumption in more steady state applications. 

The current non-GHG emissions engine test procedures also require the 

development of regeneration emission rates and frequency factors to account for the 

emission changes during a regeneration event.68 EPA and NHTSA are proposing to 

exclude the CO2 emissions and fuel consumption increases due to regeneration from the 

calculation of the compliance levels over the defined test procedures. We considered 

including regeneration in the estimate of fuel consumption and GHG emissions and have 

decided not to do so for two reasons. First, EPA’s existing criteria emission regulations 

already provide a strong motivation to engine manufacturers to reduce the frequency and 

duration of infrequent regeneration events. The very stringent 2010 NOx emission 

standards cannot be met by engine designs that lead to frequent and extend regeneration 

events. Hence, we believe engine manufacturers are already reducing regeneration 

emissions to the greatest degree possible. 

In addition to believing that regenerations are already controlled to the extent 

technologically possible, we believe that attempting to include regeneration emissions in 

the standard setting could lead to an inadvertently lax emissions standard. In order to 

include regeneration and set appropriate standards, EPA and NHTSA would have needed 

to project the regeneration frequency and duration of future engine designs in the 

timeframe of this proposal. Such a projection would be inherently difficult to make and 

quite likely would underestimate the progress engine manufacturers will make in 

reducing infrequent regenerations. If we underestimated that progress, we would 

effectively be setting a more lax set of standards than otherwise would be expected. 

Hence in setting a standard including regeneration emissions we faced the real possibility

that we would achieve less effective CO2 emissions control and fuel consumption 

reductions than we will achieve by not including regeneration emissions. We are seeking 

comments regarding regeneration emissions and what approach if any the agencies 

should use in reflecting regeneration emissions in this program. 

In conclusion, for Class 7 or 8 tractors, compliance with the vehicle standard 

would be determined by establishing values for the variable inputs and using the 

prescribed inputs in [TEST] and compliance against the engine standard using the SET 

engine cycle. The model would produce CO2 and fuel consumption results that would be 

compared against EPA's and NHTSA's respective standards. 

(j) Chassis-based Test Procedure

 The agencies also considered proposing a chassis-based vehicle test to evaluate 

Class 7/8 tractors based on a laboratory test of the engine and vehicle together. A 

"chassis dynamometer test" for heavy duty vehicles would be similar to the Federal Test 

Procedure used today for light-duty vehicles. 

 

68 40 CFR § 86.004-28
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However, the agencies decided not to propose the use of a chassis test procedure 

to demonstrate compliance for tractor standards due to the significant technical hurdles to 

implementing such a program by the 2014 model year. The agencies recognize that such 

testing requires expensive, specialized equipment that is not yet widespread within the 

industry. The agencies have only identified approximately 11 heavy duty chassis sites in 

the United States today and rapid installation of new facilities to comply with model year 

2014 is not possible.69 

In addition, and of equal if not greater importance, because of the enormous 

numbers of truck configurations that have an impact on fuel consumption, we do not 

believe that it would be reasonable to require testing of many combinations of tractor 

model configurations on a chassis dynamometer. The agencies evaluated the options 

available for one tractor model (provided as confidential business information from a 

truck manufacturer) and found that the company offered three cab configurations, six 

axle configurations, five front axles, 12 rear axles, 19 axle ratios, eight engines, 17 

transmissions, and six tire sizes – where each of these options could impact the fuel 

consumption and CO2 emissions of the tractor. Even using representative grouping of 

tractors for purposes of certification, this presents the potential for many different 

combinations that would need to be tested if a standard was adopted based on a chassis 

test procedure. 

While the agencies are not today proposing the use of a complete chassis based 

test procedure for Class 7/8 tractors, we believe such an approach could be appropriate in 

the future, if more testing facilities become available and if the agencies are able to 

address the complexity of tractor configurations issue described above. We request 

comments on the potential use of chassis based test procedures in the future whether to 

augment or replace the model based approach we are proposing today.

(3) Summary of proposed flexibility and credit provisions

EPA and NHTSA are proposing two flexibility provisions specifically for heavy

duty tractor and engine manufacturers, as discussed in Section IV below. These are an 

averaging, banking and trading program for emissions and fuel consumption credits, as 

well as provision for credits for innovative vehicle or engine technologies which are not 

included as inputs to the [TEST] model or are not demonstrated on the engine SET test 

cycle. 

The agencies are proposing that credits earned by manufacturers under this ABT 

program be restricted for use to only within the same regulatory subcategory. First, 

relating credits between categories is tenuous because of the differences in regulatory

useful lives. We want to avoid having credits from longer useful life categories flooding 

shorter useful life categories, adversely impacting compliance with CO2 or fuel 

consumption standards in the shorter useful life category, and we have not based the level 

 

69 For comparison, engine manufacturers typically own a large number of engine dynamometer test cells for 

engine development and durability (up to 100 engine dynamometers per manufacturer).
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of the standard on such impact on compliance. In addition, extending the use of credits 

beyond these designated categories could inadvertently have major impacts on the 

competitive market place, and we want to avoid such results. For example, a 

manufacturer which has multiple engine offerings over several regulatory categories 

could mix credits across engine categories and shift the burden between them, possibly

impacting the competitive market place. Similarly, integrated manufacturers which 

produce both engines and trucks could shift credits between engines and trucks and have 

a similar effect. We would like to ensure that this proposal reduces the CO2 emissions 

and fuel consumption but does not inadvertently have such impacts on the market place. 

However, we welcome comments on the extension of credits beyond the limitations we 

are proposing. 

The agencies are also proposing to provide credit provisions to manufacturers for 

the use of innovative technologies. These would include technologies resulting in 

demonstrable reductions in CO2 emissions and fuel consumption which are not accounted 

for in the [TEST] model or the engine test procedure. Innovative technology credits are 

being proposed but would be limited for use in averaging within the category in which it 

was generated.

(4) Deferral of standards for tractor and engine manufacturing companies 

that are small businesses

EPA and NHTSA are proposing to defer greenhouse gas emissions and fuel 

consumption standards for small tractor or engine manufacturers meeting the Small 

Business Administration (SBA) size criteria of a small business as described in 13 CFR 

121.201.70 The agencies will instead consider appropriate GHG and fuel consumption 

standards for these entities as part of a future regulatory action. This includes both U.S.-

based and foreign small volume heavy duty tractor or engine manufacturers.

The agencies have identified two entities that fit the Small Business 

Administration (SBA) size criterion of a small business.71 The agencies estimate that 

these small entities comprise less than 0.5 percent of the total heavy-duty combination 

tractors in the U.S. based on Polk Registration Data from 2003 through 2007,72 and 

therefore that the exemption will have a negligible impact on the GHG emissions and fuel 

consumption improvements from the proposed standards. 

To ensure that the agencies are aware of which companies would be exempt, we 

propose to require that such entities submit a declaration to EPA and NHTSA containing 

a detailed written description of how that manufacturer qualifies as a small entity under 

the provisions of 13 CFR 121.201. 

 

70 See §1036.150 and §1037.150 

71 The agencies have identified Ottawa Truck, Inc. and Kalmar Industries USA as two potential small 

tractor manufacturers.

72 M.J. Bradley. Heavy Duty Vehicle Market Analysis. May 2009.
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C. Heavy-Duty Pickup Trucks and Vans

The primary elements of the EPA and NHTSA programs being proposed for 

complete HD pickups and vans are presented in this section. These provisions also cover 

incomplete HD pickups and vans that are sold by OEMs as cab-chassis (chassis-cab, boxdelete, bed-delete, cut-away van) vehicles, and complete Class 4 pickups trucks and vans 

that are very similar to complete Class 3 vehicles, as discussed in detail in Section V.E. 

Section II.C(1) explains the proposed form of the CO2 and fuel consumption standards, 

the proposed numerical levels for those standards, and the proposed approach to phasing 

in the standards over time. The proposed measurement procedure for determining 

compliance is discussed in Section II.C(2), and the proposed EPA and NHTSA 

compliance programs are discussed in Section II.C(3). Sections II.C(4) discusses 

proposed implementation flexibility provisions. Sections II.xx and II.xx. discuss 

additional standards and provisions for N2O and CH4 emissions and for impacts from 

vehicle air conditioning.

(1) What are the proposed levels and timing of HD pickup and van standards?

(a) Vehicle-Based Standards

About 90 percent of Class 2b and 3 vehicles are pick-up trucks, passenger vans, 

and work vans that are sold by the original equipment manufacturers (OEMs) as 

complete vehicles, ready for use on the road. In addition, most of these complete HD 

pickups and vans are covered by Clean Air Act vehicle emissions standards for criteria 

pollutants today (i.e., they are chassis tested similar to light-duty), expressed in grams per 

mile. This distinguishes this category from other, larger heavy-duty vehicles that 

typically have only the engines covered by Clean Air Act engine emission standards, 

expressed in grams per brake horsepower-hour.73 As a result, Class 2b/3 complete 

vehicles share much more in common with light-duty trucks than with other heavy-duty 

vehicles.

Three of these commonalities are especially significant: (1) over 95 percent of the 

HD pickups and vans sold in the U.S. are produced by Ford, General Motors, and 

Chrysler – three companies with large light-duty vehicle (LDV) and light-duty truck 

(LDT) sales in the United States, (2) these companies typically base their HD pickup and 

van designs on higher sales volume LDT platforms and technologies, often incorporating 

new LDT design features into HD pickups and vans at their next design cycle, and (3) at 

this time most complete HD pickups and vans are certified to vehicle-based rather than 

engine-based EPA standards. There is also the potential for substantial GHG and fuel 

consumption reductions from vehicle design improvements beyond engine changes (such 

as through optimizing aerodynamics, weight, tires, and brakes), and the OEM is generally 

responsible for both engine and vehicle design. All of these factors together suggest that 

it is appropriate and reasonable to set standards for the vehicle as a whole, rather than to 

 

73 As discussed briefly in Section I and in more detail in Section V, this regulatory category also covers 

some incomplete Class 2b/3 vehicles and some complete Class 4 vehicles. 
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establish separate engine and vehicle GHG and fuel consumption standards, as is 

proposed for the other heavy-duty categories. This approach for complete vehicles is 

consistent with Recommendation 8-1 of the March 2010 NAS Report, which encourages 

the regulation of “the final stage vehicle manufacturers since they have the greatest 

control over the design of the vehicle and its major subsystems that affect fuel 

consumption.” 

(b) Weight-Based Attributes

In setting heavy-duty vehicle standards it is important to take into account the 

great diversity of vehicle sizes, applications, and features. That diversity reflects the 

variety of functions performed by heavy-duty vehicles, and this in turn can affect the kind 

of technology that is available to control emissions and reduce fuel consumption, and its 

effectiveness. EPA has dealt with this diversity in the past by making weight-based 

distinctions where necessary, for example in setting HDV standards that are different for 

vehicles above and below 10,000 lb GVWR, and in defining different standards and 

useful life requirements for light-, medium-, and heavy-heavy duty engines. Where 

appropriate, distinctions based on fuel type have also been made, though with an overall 

goal of remaining fuel-neutral. 

The joint EPA GHG and NHTSA fuel economy rules for light-duty vehicles 

accounted for vehicle diversity in that segment by basing standards on vehicle footprint 

(the wheelbase times the average track width). Passenger cars and light trucks with 

larger footprints are assigned numerically higher target levels for GHGs and numerically 

lower target levels for fuel economy in acknowledgement of the differences in 

technology as footprint gets larger, such that vehicles with larger footprints have an 

inherent tendency to burn more fuel and emit more GHGs per mile of travel. Using a 

footprint-based attribute to assign targets also avoids interfering with the ability of the 

market to offer a variety of products to maintain consumer choice. 

In developing this proposal, the agencies emphasized creating a program structure 

that would achieve reductions in fuel consumption and GHGs based on how vehicles are 

used and on the work they perform in the real world, consistent with the March 2010 

NAS report recommendations to be mindful of HD vehicles’ unique purposes. Despite 

the HD pickup and van similarities to light-duty vehicles, we believe that the past 

practice in EPA’s heavy-duty program of using weight-based distinctions in dealing with 

the diversity of HD pickup and van products is more appropriate than using vehicle 

footprint. Weight-based measures such as payload and towing capability are key among 

the things that characterize differences in the design of vehicles, as well as differences in 

how the vehicles will be used. Vehicles in this category have a wide range of payload and 

towing capacities. These weight-based differences in design and in-use operation are the 

key factors in evaluating technological improvements for reducing CO2 emissions and 

fuel consumption. Payload has a particularly important impact on the test results for HD 

pickup and van emissions and fuel consumption, because testing under existing EPA 
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procedures for criteria pollutants is conducted with the vehicle loaded to half of its 

payload capacity (rather than to a flat 300 lb as in the light-duty program), and the 

correlation between test weight and fuel use is strong. 74 

Towing, on the other hand, does not directly factor into test weight as nothing is 

towed during the test. Hence only the higher curb weight caused by heavier truck 

components would play a role in affecting measured test results. However towing 

capacity can be a significant factor to consider because HD pickup truck towing 

capacities can be quite large, with a correspondingly large effect on design.

We note too that, from a purchaser perspective, payload and towing capability

typically play a greater role than physical dimensions in influencing purchaser decisions 

on which heavy-duty vehicle to buy. For passenger vans, seating capacity is of course a 

major consideration, but this correlates closely with payload weight.

Although heavy-duty vehicles are traditionally classified by their GVWR, we do 

not believe that GVWR is the best weight-based attribute on which to base GHG and fuel 

consumption standards for this group of vehicles. GVWR is a function of not only

payload capacity but of vehicle curb weight as well; in fact, it is the simple sum of the 

two. Allowing more GHG emissions from vehicles with higher curb weight tends to 

penalize lightweighted vehicles with comparable payload capabilities by making them 

meet more stringent standards than they would have had to meet without the weight 

reduction. The same would be true for another common weight-based measure, the gross 

vehicle combined weight (GCWR), which adds the maximum combined towing and 

payload weight to the curb weight. 

Similar concerns about using weight-based attributes that include vehicle curb 

weight were raised in the EPA/NHTSA proposal for light-duty GHG and fuel economy 

standards: “footprint-based standards provide an incentive to use advanced lightweight 

materials and structures that would be discouraged by weight-based standards”, and

“there is less risk of ‘gaming’ (artificial manipulation of the attribute(s) to achieve a more 

favorable target) by increasing footprint under footprint-based standards than by

increasing vehicle mass under weight-based standards—it is relatively easy for a 

manufacturer to add enough weight to a vehicle to decrease its applicable fuel economy 

target a significant amount, as compared to increasing vehicle footprint.”75 The agencies 

believe that using payload and towing capacities as the weight-based attributes would 

avoid the above-mentioned disincentive for the use of lightweighting technology by

taking vehicle curb weight out of the standards determination. 

After taking these considerations into account, EPA and NHTSA have decided to 

propose standards for HD pickups and vans based on a “work factor” attribute that 

combines vehicle payload capacity and vehicle towing capacity, in pounds, with an 

 

74 Section II.C(2) discusses our decision to propose that GHGs and fuel consumption for HD pickups and 

vans be measured using the same test conditions as in the existing EPA program for criteria pollutants.

75 74 FR 49685, September 28, 2009.
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additional fixed adjustment for four-wheel drive (4wd) vehicles. This adjustment would 

account for the fact that 4wd, critical to enabling the many off-road heavy-duty work 

applications, adds roughly 500 lb to the vehicle weight. Under our proposal, target GHG 

and fuel consumption standards would be determined for each vehicle with a unique 

work factor. These targets would then be production weighted and summed to derive a 

manufacturer’s annual fleet average standards. 

To ensure consistency and help preclude gaming, we are proposing that payload 

capacity be defined as GVWR minus curb weight, and towing capacity as GCWR minus 

GVWR. We are proposing that, for purposes of determining the work factor, GCWR be 

defined according to SAE Recommended Practice J2807 APR2008, GVWR be defined 

consistent with EPA’s criteria pollutants program, and curb weight be defined as in 40 

CFR § 86.1803-01. We request comment on the need to establish additional regulations 

or guidance to ensure that these terms are determined and applied consistently across the 

HD pickup and van industry for the purpose of determining standards. 

Based on analysis of how CO2 emissions and fuel consumption correlate to work 

factor (see memorandum to the docket, xx), we believe that a straight line correlation is 

appropriate across the spectrum of possible HD pickups and vans, and that vehicle 

distinctions such as Class 2b vs. Class 3 need not be made in setting standards levels for 

these vehicles. We request comment on this proposed approach.

We note that payload/towing-dependent gram per mile and gallon per 100 mile 

standards for HD pickups and vans parallel the gram per ton-mile and gallon per 1000 

ton-mile standards being proposed for Class 7/8 combination tractors and for vocational 

trucks. Both approaches account for the fact that more work is done, more fuel is burned, 

and more CO2 is emitted in moving heavier loads than in moving lighter loads. Both of 

these load-based approaches avoid penalizing truck designers wishing to reduce GHG 

emissions and fuel consumption by reducing the weight of their trucks. However, the 

sizeable diversity in HD work truck and van applications, which go well beyond simply

transporting freight, and the fact that the curb weights of these vehicles are on the order 

of their payload capacities, suggest that setting simple gram/ton-mile and gallon/ton-mile 

standards for them are not appropriate. Even so, we believe that our proposal of payloadbased standards for HD pickups and vans is consistent with the NAS Report’s 

recommendation in favor of load-specific fuel consumption standards.

These attribute-based CO2 and fuel consumption standards are meant to be 

relatively consistent from a stringency perspective. Vehicles across the entire range of 

the HD pickup and van segment have their respective target values for CO2 emissions and 

fuel consumption, and therefore all HD pickups and vans would be affected by the 

standard. With the proposed attribute-based standards approach, EPA and NHTSA 

believe there should be no significant effect on the relative distribution of vehicles with 

differing capabilities in the fleet, which means that buyers should still be able to purchase 

the vehicle that meets their needs.
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(c) Proposed Standards

The agencies are proposing standards based on a technology analysis performed 

by EPA to determine the appropriate HD pickup and van standards. This analysis, 

described in detail in Draft RIA Chapter 2, considered:

 the level of technology that is incorporated in current new HD pickups and vans, 

 the available data on corresponding CO2 emissions and fuel consumption for these 

vehicles, 

 technologies that would reduce CO2 emissions and fuel consumption and that are 

judged to be feasible and appropriate for these vehicles through the 2018 model year, 

 the effectiveness and cost of these technologies for HD pickup and vans, 

 projections of future U.S. sales for HD pickup and vans, and 

 forecasts of manufacturers’ product redesign schedules.

Based on this analysis, EPA is proposing the CO2 attribute-based target standards

shown in Figure II-2 and II-3, and NHTSA is proposing the equivalent attribute-based 

fuel consumption target standards, also shown in Figure II-2, applicable in model year 

2018. These figures also shows phase-in standards for model years before 2018, and 

their derivation is explained below, along with alternative implementation schedules to 

ensure equivalency between the EPA and NHTSA programs while meeting statutory

obligations. Also, for reasons discussed below, separate targets are being established 

for gasoline-fueled (and any other Otto-cycle) vehicles and diesel-fueled (and any other 

Diesel-cycle) vehicles. The targets would be used to determine the production-weighted 

standards that apply to the combined diesel and gasoline fleet of HD pickups and vans

produced by a manufacturer in each model year.
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300

350

400

450

500

550

600

650

700

750

800

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Work Factor (pounds)

CO2 (grams per mile)

2.95

3.95

4.95

5.95

6.95

Fuel Consumption (gallons per 100 miles)

Diesel Vehicles

2015

2014

2018

2016

2017

Figure II-2: Proposed EPA CO2 Target Standards and NHTSA Fuel Consumption Target Standards 

for Diesel HD Pickups and Vans76

 

76 The NHTSA proposal provides a voluntary opt-in for model years 2014 and 2015. Target line functions 

for 2016-2018 are for the second NHTSA alternative described in Section II.C(d)(ii).
Draft Joint EPA/NHTSA NPRM Preamble HD GHG/FC Standards (8/11/2010)

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300

350

400

450

500

550

600

650

700

750

800

0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000

Work Factor (pounds)

CO2 (grams per mile)

3.38

4.38

5.38

6.38

7.38

8.38

Fuel Consumption (gallons per 100 miles)

Gasoline Vehicles

2018

2017

2015

2014

2016

Figure II-3: Proposed EPA CO2 Target Standards and NHTSA Fuel Consumption Target Standards 

for Gasoline HD Pickups and Vans77

Described mathematically, EPA’s and NHTSA’s proposed functions are defined 

by the following formulae:

EPA CO2 Target (g/mile) = [a x WF] + b

NHTSA Fuel Consumption Target (gallons/100 miles) = [c x WF] + d

Where:

WF = Work Factor = [0.75 x (Payload Capacity + xwd)] + [0.25 x Towing 

Capacity]

Payload Capacity = GVWR (lbs) – Curb Weight (lbs)

xwd = 500 lbs if the vehicle is equipped with 4wd, otherwise equals 0 lbs

Towing Capacity = GCWR (lbs) – GVWR (lbs)

 

77 The NHTSA proposal provides a voluntary opt-in for model years 2014 and 2015. Target line functions 

for 2016-2018 are for the second NHTSA alternative described in Section II.C(d)(ii).
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Coefficients a, b, c, and d are taken from Table II-7 or Table II-8.

Table II-7: Coefficients for Proposed HD Pickup and Van Target Standards 78

Diesel Vehicles

model yr a b c d

2014 0.

0478

36

8

0.00047

0

3.6

2

2015 0.

0474

36

6

0.00046

6

3.5

9

2016 0.

0460

35

4

0.00045

2

3.4

8

2017 0.

0445

34

3

0.00043

7

3.3

7

2018 0.

0416

32

0

0.00040

8

3.1

5

Gasoline Vehicles

model yr a b c d

2014 0.

0482

37

1

0.00047

3

3.6

5

2015 0.

0479

36

9

0.00047

1

3.6

3

2016 0.

0469

36

2

0.00046

1

3.5

5

2017 0.

0460

35

4

0.00045

2

3.4

8

2018 0.

0440

33

9

0.00043

2

3.3

3

Table II-8: Coefficients Proposed for NHTSA’s First Alternative and EPA’s Alternative 

HD Pickup and Van Target Standards

 

78 The NHTSA proposal provides a voluntary opt-in for model years 2014 and 2015. Target line functions 

for 2016-2018 are for the second NHTSA alternative described in Section II.C(d)(ii).
Draft Joint EPA/NHTSA NPRM Preamble HD GHG/FC Standards (8/11/2010)

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Diesel Vehicles

model yr a b c d

2014(a) 0.047

8

36

8

0.00047

0

3.6

2

2015(a) 0.047

4

36

6

0.00046

6

3.5

9

2016-2018 0.044

0

33

9

0.00043

2

3.3

3

2019 (b) 0.041

6

32

0

-- --

Gasoline Vehicles

model yr a b c d

2014(a) 0.048

2

37

1

0.00047

3

3.6

5

2015(a) 0.047

9

36

9

0.00047

1

3.6

3

2016-2018 0.045

6

35

2

0.00044

8

3.4

5

2019 (b) 0.044

0

33

9

-- --

(a) NHTSA standards would be voluntary in 2014 and 2015

(b) There are no proposed NHTSA standards in 2019

These targets are based on a set of vehicle, engine, and transmission technologies 

assessed by the agencies and determined to be feasible and appropriate for HD pickups 

and vans in the 2014-2018 timeframe. Much of the information used to make this 

technology assessment was developed for the recent 2012-2016 light-duty GHG and fuel 

economy rulemaking. See Section III.A for a detailed analysis of these vehicle, engine 

and transmission technologies, including their feasibility, costs, and effectiveness in HD 

pickups and vans.

To calculate a manufacturer’s HD pickup and van fleet average standard, the 

agencies are proposing that separate target curves be used for gasoline and diesel 

vehicles. The agencies estimate that in 2018 the target curves will achieve 15 and 10 

percent reductions in CO2 and fuel consumption for diesel and gasoline vehicles, 

respectively, relative to a common baseline for current (model year 2010) vehicles. An 

additional two percent reduction in GHGs would be achieved by the EPA program from a 

proposed direct air conditioning leakage standard. These reductions are based on the 

agencies’ assessment of the feasibility of incorporating technologies (which differ 

significantly for gasoline and diesel powertrains) in the 2014-2018 model years, and on 

the differences in relative efficiency in the current gasoline and diesel vehicles. The 

resulting reductions represent roughly equivalent stringency levels for gasoline and diesel 
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vehicles, which is important in ensuring our proposed program maintains product choices 

available to vehicle buyers.

The NHTSA fuel consumption target curves and the EPA GHG target curves are 

equivalent. The agencies established the target curves using the direct relationship 

between fuel consumption and CO2 using conversion factors of 8887 g CO2/gallon for 

gasoline and 10,180 g CO2/gallon for diesel fuel.

It is expected that measured performance values for CO2 would generally be 

equivalent to fuel consumption. However, as explained in section II.xx ,EPA is 

proposing an alternative for manufacturers to demonstrate compliance with N2O and CH4

emissions standards through the calculation of a CO2-equivalent emissions level that 

would be compared to the CO2-based standards, similar to the recently promulgated lightduty GHG standards for model years 2012-2016. For test families that do not use this 

compliance alternative, the measured performance values for CO2 and fuel consumption 

would be equivalent because the same test runs and measurement data would be used to 

determine both values, and calculated fuel consumption would be based on the same 

conversion factors that are used to establish the relationship between the CO2 and fuel 

consumption target curves (8887 g CO2/gallon for gasoline and 10,180 g CO2/gallon for 

diesel fuel). In this case, for example, if a manufacturer’s fleet average measured 

compliance value exactly meets the fleet average CO2 standard, it will also exactly meet 

the fuel consumption standard. The proposed NHTSA fuel consumption program will 

not use a CO2 -equivalent metric. Measured performance to standards would be based on 

the measurement of CO2 with no adjustment for N2O and CH4. For manufacturers that 

choose to use the EPA CO2-equivalent approach, compliance with the CO2 standard 

would not be directly equivalent to compliance with the NHTSA fuel consumption 

standard. 

(d) Proposed Implementation Plan

(i) EPA Program Phase-in 2014-2018

EPA is proposing that the GHG standards be phased in gradually over the 2014-

2018 model years, with full implementation effective in the 2018 model year. Therefore,

100 percent of a manufacturer’s vehicle fleet would need to meet a fleet-average standard 

that would become increasingly more stringent each year of the phase-in period. For 

both gasoline and diesel vehicles, this phase-in would be 15-20-40-60-100 percent in 

model years 2014-2015-2016-2017-2018, respectively. These percentages reflect 

stringency increases from a baseline performance level for model year 2010, determined 

by the agencies based on EPA and manufacturer data. Because these vehicles are not 

currently regulated for GHG emissions, this phase-in takes the form of target line 

functions for gasoline and diesel vehicles that become increasingly stringent over the 

phase-in model years. These year-by-year functions have been derived in the same way

as the 2018 function, by taking a percent reduction in CO2 from a common unregulated 

baseline. For example, in 2014 the reduction for both diesel and gasoline vehicles would 

be 15% of the fully-phased-in reductions (15% of 10%). Figures II-2 and II-3, and Table 

II-7, reflect this phase-in approach.
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EPA is also proposing to provide manufacturers with an optional alternative 

implementation schedule in model years 2016 through 2018, equivalent to NHTSA’s 

proposed first alternative for standards that do not change over these model years,

described below. Under this option the phase-in would be 15-20-67-67-67-100 percent in 

model years 2014-2015-2016-2017-2018-2019, respectively. Table II-8 provides the 

coefficients, a and b, for this manufacturer’s alternative. As explained below, the 

stringency of this alternative was established by NHTSA such that a manufacturer with a 

stable production volume and mix over the model year 2016-2018 period could use 

Averaging, Banking and Trading to comply with either alternative and have a similar 

credit balance at the end of model year 2018.

Under the above-described alternatives, each manufacturer would need to 

demonstrate compliance with the applicable fleet average standard using that year’s 

target function over all of its HD pickups and vans starting in 2014. EPA also request 

comment on different regulatory approach to the phase-in, intended to reduce the testing 

and certification burden on manufacturers during the 2014-2017 phase-in years, while 

achieving GHG reductions on the same schedule as the proposed phase-in. In this 

alternative approach, each manufacturer would be required to demonstrate compliance 

with the final 2018 targets, but only over a predefined percentage of its HD pickup and 

van production. The remaining vehicles produced each year would not be regulated for 

GHGs. Thus this approach would have the effect of setting final standards in 2014 that 

do not vary over time, but with an annually increasing set of regulated vehicles. The 

percentage of regulated vehicles would increase each year, to 100 percent in 2018. We 

think it likely that manufacturers would leave the highest emitting vehicles unregulated 

for as long as possible under this approach, because these vehicles would tend to be the 

costliest to redesign or may simply be phasing out of production. We therefore expect 

that, to be equivalent, the percentage penetration each year would be higher than the 15-

20-40-60 percent penetrations required under the proposed approach. EPA requests 

comment on this regulatory alternative, and on what percentage penetrations are 

appropriate to achieve equivalent program benefits.

(ii) NHTSA Program Phase-in 2016-2018

NHTSA is proposing to allow manufacturers to select one of two fuel 

consumption standard alternatives fuel consumption standards for model years 2016-

2018, as well as a manufacturer’s phase-in alternative, involving voluntary standards in 

2014-2015. Manufacturers would select an alternative at the same time they submit the 

model year 2016 Pre-Certification Compliance Report; and, once selected, the alternative 

would apply for model years 2016 – 2018, and could not be reversed. To meet the EISA 

statutory requirement for three years of regulatory stability, the first alternative would 

define a fuel consumption target line function for gasoline vehicles and a target line 

function for diesel vehicles that would not change over model years 2016 and 2018. The 

proposed target line function coefficients are provided in Table II-7. 

The second alternative would be equivalent to the EPA target line functions in 

each model year 2016 to 2018. Stringency of fuel consumption standards would increase 

gradually over the 2016-2018 model years. Relative to a model year 2010 unregulated 
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baseline, for both gasoline and diesel vehicles, stringency would be 40-60-100 percent of 

the 2018 target line function in model years 2016-2017-2018, respectively. 

The stringency of the target line functions in the first alternative is 67 percent of 

the 2018 stringency in the second alternative. The stringency of the first alternative was 

established so that a manufacturer with a stable production volume and mix over the 

model year 2016-2018 period, could use Averaging, Banking and Trading to comply with 

either alternative and have a similar credit balance at the end of model year 2018.

NHTSA also requests comment on a different regulatory approach that would 

parallel the above-described EPA regulatory alternative involving certification of a predefined percentage of a manufacturer’s HD pickup and van production.

(iii) NHTSA Voluntary Standards Period

NHTSA is proposing that manufacturers may voluntarily opt into the NHTSA HD 

pickup and van program in model years 2014 or 2015. If a manufacturer elects to opt 

into the program, the program would become mandatory and the manufacturer would not 

be allowed to reverse this decision. To opt into the program, a manufacturer must declare 

its intent to opt in to the program at the same time it submits the Pre-Certification 

Compliance Report. See proposed regulatory text for 49 CFR Part 535.8 for information 

related to the Pre-Certification Compliance Report. If a manufacturer elects to opt into 

the program in 2014, the program would be mandatory for 2014 and 2015. A 

manufacturer would begin tracking credits and debits beginning in the model year in 

which they opt into the program. The handling of credits and debits would be the same 

as fort the mandatory program and would continue through 2018.

For manufacturers that opt into NHTSA’s HD pickup and van fuel consumption 

program in 2014 or 2015, the stringency would increase gradually each model year. 

Relative to a model year 2010 unregulated baseline, for both gasoline and diesel vehicles, 

stringency would be 15-20 percent of the model year 2018 target line function (under the 

NHTSA second alternative) in model years 2014-2015, respectively. The corresponding 

absolute standards targets levels are provided in Figure II-2, and the accompanying 

equations. 

NHTSA also requests comment on a different regulatory approach that would 

parallel the above-described EPA regulatory alternative involving certification of a predefined percentage of a manufacturer’s HD pickup and van production.

(2) What are the proposed HD pickup and van test cycles and procedures?

EPA and NHTSA are proposing that HD pickup and van testing be conducted 

using the same heavy-duty chassis test procedures currently used by EPA for measuring 

criteria pollutant emissions from these vehicles, but with the addition of the highway fuel 

economy test cycle (HFET) currently required only for light-duty vehicle GHG emissions 

and fuel economy testing. Although the highway cycle driving pattern would be identical 

to that of the light-duty test, other test parameters for running the HFET, such as test 
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vehicle loaded weight, would be identical to those used in running the current EPA 

Federal Test Procedure for complete heavy-duty vehicles.

The GHG and fuel consumption results from vehicle testing on the FTP and the 

HFET would be weighted by 55 percent and 45 percent, respectively, and then averaged 

in calculating a combined cycle result. This result corresponds with the data used to 

develop the proposed work factor-based CO2 and fuel consumption standards, since the 

data on the baseline and technology efficiency was also developed in the context of these 

test procedures. The addition of the HFET and the 55/45 cycle weightings are the same 

as for the light-duty CO2 and CAFE programs, as we believe the real world driving 

patterns for HD pickups and vans are not too unlike those of light-duty trucks, and we are 

not aware of data specifically on these patterns that would lead to a different choice of 

cycles and weightings. More importantly, we believe that the 55/45 weightings will 

provide for effective reductions of GHG emissions and fuel consumption from these 

vehicles, and that other weightings, even if they were to more precisely match real world 

patterns, are not likely to significantly improve the program results.

Another important parameter in ensuring a robust test program is vehicle test 

weight. Current EPA testing for HD pickup and van criteria pollutants is conducted with 

the vehicle loaded to its Adjusted Loaded Vehicle Weight (ALVW), that is, its curb 

weight plus 1⁄2 of the payload capacity. This is substantially more challenging than 

loading to the light-duty vehicle test condition of curb weight plus 300 pounds, but we 

believe that this loading for HD pickups and vans to 1⁄2 payload better fits their usage in 

the real world and would help ensure that technologies meeting the standards do in fact 

provide real world reductions. The choice is likewise consistent with use of an attribute 

based in considerable part on payload for the standard. We see no reason to set test load 

conditions differently for GHGs and fuel consumption than for criteria pollutants, and we 

are not aware of any new information (such as real world load patterns) since the ALVW 

was originally set this way that would support a change in test loading conditions. We 

are therefore proposing to use ALVW for test vehicle loading in GHG and fuel 

consumption testing.

EPA and NHTSA request comment on the proposed test cycles, weighting 

factors, test loading conditions, and other factors that are important for establishing an 

effective GHG and fuel consumption test program. Additional provisions for our 

proposed testing and compliance program are provided in Section V.E.

(3) How are the HD pickup and van standards structured?

EPA and NHTSA are proposing fleet average standards for new HD pickups and 

vans, based on a manufacturer’s new vehicle fleet makeup. In addition, EPA is 

proposing in-use standards that would apply to the individual vehicles in this fleet over 

their useful lives. The compliance provisions for these proposed fleet average and in-use 

standards for HD pickups and vans are largely based on the recently promulgated lightduty GHG and fuel economy program, as described below and in greater detail in Section 

V.E.
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(a) Fleet Average Standards

In this proposal we outline how each manufacturer would have a GHG standard 

and a fuel consumption standard unique to its new HD pickup and van fleet in each 

model year, depending on the load capacities of the vehicle models produced by that 

manufacturer, and on the U.S.-directed production volume of each of those models in that 

model year. Vehicle models with larger payload/towing capacities would have individual 

targets at numerically higher CO2 and fuel consumption levels than lower payload/towing 

vehicles would, as discussed in Section II.C(1). The fleet average standard for a 

manufacturer would be a production-weighted average of the work factor-based targets 

assigned to unique vehicle configurations within each each model type produced by the 

manufacturer in a model year.

The fleet average standard with which the manufacturer must comply would be 

based on its final production figures for the model year, and thus a final assessment of 

compliance would occur after production for the model year ended. Because compliance 

with the fleet average standards depends on actual test group production volumes, it is 

not possible to determine compliance at the time the manufacturer applies for and 

receives an EPA certificate of conformity for a test group. Instead, at certification the 

manufacturer would demonstrate a level of performance for vehicles in the test group, 

and make a good faith demonstration that its fleet, regrouped by unique vehicle 

configurations within each model type, is expected to comply with its fleet average 

standard when the model year is over. EPA would issue a certificate for the vehicles 

covered by the test group based on this demonstration, and would include a condition in 

the certificate that if the manufacturer does not comply with the fleet average, then 

production vehicles from that test group will be treated as not covered by the certificate 

to the extent needed to bring the manufacturer’s fleet average into compliance. As in the 

light-duty program, additional “model type” testing would be conducted by the 

manufacturer over the course of the model year to supplement the initial test group data. 

The emissions and fuel consumption levels of the test vehicles would be used to calculate 

the production-weighted fleet averages for the manufacturer, after application of the 

appropriate deterioration factor to each result to obtain a full useful life value. See 

generally 75 FR at 25470-72.

EPA and NHTSA do not currently anticipate notable deterioration of CO2

emissions and fuel consumption performance, and are therefore proposing that an 

assigned deterioration factor be applied at the time of certification: an additive assigned 

deterioration factor of zero, or a multiplicative factor of one would be used. EPA and 

NHTSA anticipate that the deterioration factor would be updated from time to time, as 

new data regarding emissions deterioration for CO2 are obtained and analyzed. 

Additionally, EPA and NHTSA may consider technology-specific deterioration factors, 

should data indicate that certain control technologies deteriorate differently than others. 

See also 75 FR at 25474.
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(b) In-Use Standards

Section 202(a)(1) of the Clean Air Act specifies that EPA set emissions standards 

that are applicable for the useful life of the vehicle. The in-use standards that EPA is 

proposing would apply to individual vehicles. NHTSA is not proposing to adopt in-use 

standards because it is not required under EISA, and because it is not currently

anticipated that there will be any notable deterioration of fuel consumption. For the EPA 

proposal, compliance with the in-use standard for individual vehicles and vehicle models 

will not impact compliance with the fleet average standard, which will be based on the 

production weighted average of the new vehicles.

EPA is proposing that the in-use standards for HD pickups and vans be 

established by adding an adjustment factor to the full useful life emissions and fuel 

consumption results used to calculate the fleet average. EPA is also proposing that the 

useful life for these vehicles with respect to GHG emissions be set equal to their useful 

life for criteria pollutants: 11 years or 120,000 miles, whichever occurs first (40 CFR 

86.1805-04(a)).

As discussed above, we are proposing that certification test results obtained 

before and during the model year be used directly to calculate the fleet average emissions 

for assessing compliance with the fleet average standard. Therefore this assessment and 

the fleet average standard itself do not take into account test-to-test variability and 

production variability that can affect measured in-use levels. For this reason is proposing 

an adjustment factor for the in-use standard to provide some margin for production and 

test-to-test variability that could result in differences between the initial emission test 

results used to calculate the fleet average and emission results obtained during subsequent 

in-use testing. EPA is proposing that each model’s in-use CO2 standard would be the 

model-specific level used in calculating the fleet average, plus 10 percent. This is the 

same as the approach taken for light-duty vehicle GHG in-use standards.79 NHTSA is 

proposing that the same 10 percent margin be applied to the model-specific fuel 

consumption levels used in calculating the fleet average fuel consumption.

As it does now for heavy-duty vehicle criteria pollutants, EPA would use a variety 

of mechanisms to conduct assessments of compliance with the proposed in-use standards, 

including pre-production certification and in-use monitoring once vehicles enter customer 

service. The full useful life in-use standards would apply to vehicles that had entered 

customer service. The same standards would apply to vehicles used in pre-production 

and production line testing, except that deterioration factors would not be applied.

(4) What HD pickup and van flexibility provisions are being proposed?

This proposal contains substantial flexibility in how manufacturers can choose to 

implement the EPA and NHTSA standards while preserving their timely benefits for the 

environment and energy security. Primary among these flexibilities are the gradual 

 

79 75 FR at 25473-74. 
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phase-in schedule, alternative compliance paths, and corporate fleet average approach 

described above. Additional flexibility provisions are described briefly here and in more 

detail in Section IV.

As explained in Section II.C(3), we are proposing that at the end of each model 

year, when production for the model year is complete, a manufacturer calculate its 

production-weighted fleet average CO2 and fuel consumption. Under this proposed 

approach, a manufacturer’s HD pickup and van fleet that achieves a fleet average CO2 or 

fuel consumption level better than its standard would be allowed to generate credits. 

Conversely, if the fleet average CO2 or fuel consumption level does not meet its standard, 

the fleet would incur debits (also referred to as a shortfall).

A manufacturer whose fleet generates credits in a given model year would have 

several options for using those credits to offset emissions from other HD pickups and 

vans. These options include credit carry-back, credit carry-forward, and credit trading. 

These provisions exist in the 2012-2016 light-duty vehicle National Program, and similar 

provisions are part of EPA’s Tier 2 program for light-duty vehicle criteria pollutant 

emissions, as well as many other mobile source standards issued by EPA under the Clean 

Air Act. The manufacturer would be able to carry back credits to offset a deficit that had 

accrued in a prior model year and was subsequently carried over to the current model 

year, with a limitation on the carry-back of credits to three years, consistent with the 

light-duty program. We are proposing that, after satisfying any need to offset preexisting deficits, a manufacturer may bank remaining credits for use in future years. This 

averaging, banking, and trading program for HD pickups and vans is discussed in more 

detail in Section IV.D. We are not proposing any credit transferability to or from other 

credit programs, such as the light-duty GHG and fuel consumption programs or the 

proposed heavy-duty engine ABT program.

Consistent with the President’s May 21, 2010 directive to promote advanced 

technology vehicles, we are also proposing two other flexibility provisions that parallel 

similar provisions adopted in the light-duty program. (1) Advanced technology credits 

(detailed in Section IV.D) for electric vehicles, plug-in electric vehicles, and fuel cell 

vehicles would be made available in the 2014 through 2018 model years. (2) Off-cycle 

technology credits (also detailed in Section IV.D) would be provided starting in the 2014 

model year for innovative technologies shown by the manufacturer to provide GHG and 

fuel consumption reductions in real world driving, but not on the test.

Our proposed approach to recognizing the benefits of flexible-fueled vehicles 

(FFVs) and dedicated alternative-fueled vehicles is also based on the approach taken by

EPA in the light-duty vehicle rule for later models years, but, unlike in that rule, we are 

not referring to it as a credits provision because it does not include the incentives 

mandated in EISA for light-duty vehicles only. In fact, since heavy duty vehicles were 

not included in the EISA incentives for FFVs, manufacturers did not produce FFV heavy

duty vehicles. These provisions are discussed in detail in Section V.E. We are also not 

referring to our proposed treatment of air conditioning improvements as credits 

provisions for reasons explained in Section II.xx. 
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D. Class 2b-8 Vocational Trucks

Class 2b-8 vocational trucks (i.e. vehicles) consist of a very wide variety of 

configurations including delivery, refuse, utility, dump, cement, transit bus, shuttle bus, 

school bus, emergency vehicle, motor homes,80 and tow trucks, among others. The 

agencies are defining that Class 2b-8 vocational vehicles are all heavy-duty vehicles 

which are not included in the Heavy Duty Pickup Truck and Van or the Class 7/8 Tractor 

segments, with the exception of vehicles for which the agencies are deferring setting of 

standards, such as small business manufacturers. In addition, recreational vehicles are 

included under EPA’s proposed standards but are not included under NHTSA’s proposed 

standards.

As mentioned in Section I, vocational trucks undergo a complex build process. 

Often an incomplete chassis is built by a chassis manufacturer with an engine purchased 

from an engine manufacturer and a transmission purchased from another manufacturer. 

A body manufacturer purchases an incomplete chassis which is then completed by

attaching the appropriate features to the chassis. 

The agencies face difficulties in establishing the baseline CO2 and fuel 

consumption performance for the wide variety of vocational trucks which makes it 

difficult to try and set different standards for a large number of potential regulatory

categories. The diversity in the vocational vehicle segment can be primarily attributed to 

the variety of vehicle bodies rather than the chassis. For example, a body builder can 

build either a Class 6 bucket truck or a Class 6 delivery truck from the same Class 6 

chassis. The aerodynamic difference between these two vehicles due to their bodies will 

lead to different baseline fuel consumption and GHG emissions. However, the baseline 

fuel consumption and emissions due to the components included in the common chassis 

(such as the engine, drivetrain, frame, and tires) will be the same between these two types 

of complete vehicles. Furthermore, the agencies evaluated the aerodynamic improvement 

opportunities for vocational vehicles. For example, the aerodynamics of a fire truck are 

impacted significantly by the equipment such as ladders located on the exterior of the 

truck. The agencies found little opportunity to improve the aerodynamics of the 

equipment on the truck. The agencies also evaluated the aerodynamic opportunities 

discussed in the NAS report. The panel found that there was no fuel consumption 

reduction opportunity through aerodynamic technologies for bucket trucks, transit buses, 

and refuse trucks81 primarily due to the low vehicle speed in normal operation. The panel 

did report that there are opportunities to reduce the fuel consumption of straight trucks by 

approximately 1 percent for trucks which operate at the average speed typical of a pickup 

and delivery truck (30 mph), although the opportunity is greater for trucks which operate 

at higher speeds.82 To overcome the lack of baseline information from the different 

vehicle applications without sacrificing much fuel consumption or GHG emission 

 

80 See above for discussion of applicability of NHTSA’s standards to non-commercial vehicles.

81 NAS Report. Page 6-3.

82 NAS Report, Page 5-29.
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reduction potential, the agencies propose to set standards for the chassis manufacturers of 

vocational vehicles (instead of the body builders) and the engine manufacturers. 

EPA is proposing CO2 standards and NHTSA is proposing fuel consumption 

standards for manufacturers of chassis for new vocational vehicles and for manufacturers 

of heavy duty engines installed in these vehicles. The proposed heavy duty engine 

standards for CO2 emissions and fuel consumption would focus on potential 

technological improvements in fuel combustion and overall engine efficiency and those 

proposed controls would achieve most of the emission reductions. Further reductions 

from the class 2b-8 vocational vehicle itself are possible within the timeframe of these 

proposed regulations. Therefore, the agencies are also proposing separate standards for 

vocational vehicles that will focus on additional reductions that can be achieved through 

improvements in vehicle tires. The agencies' analyses, as discussed briefly below and in 

more detail later in this preamble and in the Draft RIA Chapter 2, show that these 

standards are appropriate under each agency’s respective statutory authorities. Together 

these standards are estimated to achieve reductions up to 11 percent from vocational 

trucks.

EPA is also proposing standards to control N2O and CH4 emissions from Class 

2b-8 vocational trucks. The proposed heavy duty engine standards for both N2O and CH4

and details of the standard are included in the discussion in II.E. EPA is not proposing air 

conditioning leakage standards applying to chassis manufacturers to address HFC 

emissions. 

As discussed further below, the agencies propose to set CO2 and fuel consumption 

standards for these chassis based on tire rolling resistance improvements and for the 

engines based on engine technologies. The fuel consumption and GHG emissions impact 

of tire rolling resistance is impacted by the mass of the vehicle. However the impact of 

mass on rolling resistance is relatively small so the agencies propose to aggregate several 

vehicle weight categories under a single category for setting the standards. The agencies 

propose to divide the vocational vehicle segment into three broad regulatory categories -

Light Heavy (Class 2b through 5), Medium Heavy (Class 6 and 7), and Heavy Heavy 

(Class 8) which is consistent with the nomenclature used in the diesel engine 

classification. The agencies are interested in comment on this segmentation strategy

(subcategorization). As the agencies move towards future heavy duty fuel consumption 

and GHG regulations for post-2017 model years, we intend to gather GHG and fuel 

consumption data for specific vocational applications which could be used to establish 

application-specific standards in the future.

(1) What are the proposed CO2 and Fuel Consumption standards and their 

timing?

In developing the proposed standards, the agencies have evaluated the current 

levels of emissions and fuel consumption, the kinds of technologies that could be utilized 

by manufacturers to reduce emissions and fuel consumption and the associated lead time, 

the associated costs for the industry, fuel savings for the consumer, and the magnitude of 

the CO2 and fuel economy savings that may be achieved. The technologies that the 
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agencies considered while setting the proposed vehicle-level standards include 

improvements in lower rolling resistance tires. The technologies that the agencies 

considered while setting the engine standards include engine friction reduction, 

aftertreatment optimization, among others. The agencies’ evaluation indicates that these 

technologies are available today in the heavy duty tractor and light-duty vehicle markets, 

but have very low application rates in the vocational market. The agencies have analyzed 

the technical feasibility of achieving the proposed CO2 and fuel consumption standards, 

based on projections of what actions manufacturers would be expected to take to reduce 

emissions and fuel consumption to achieve the standards, and believe that the proposed 

standards are appropriate, cost-effective, and technologically feasible within the 

rulemaking time frame. EPA and NHTSA also present the estimated costs and benefits 

of the proposed vocational truck standards in Section III. 

(a) Proposed Chassis Standards

EPA is proposing the following CO2 standards for the 2014 model year for the 

Class 2b through Class 8 vocational truck chassis. Similarly, NHTSA is proposing the 

following fuel consumption standards for the 2016 model year, with a voluntary opt-in 

program offered beginning in the 2014 model year. For the EPA GHG program, the 

proposed standard applies throughout the useful life of the vehicle. 

EPA and NHTSA proposing more stringent vehicle standards for the 2017 model 

year which reflect the CO2 emissions reductions required through the 2017 model year 

engine standards. (As explained in Section B. (2) (h)(v) above, engine performance is 

one of the inputs into the compliance model, and that input will change in 2017 to reflect 

the 2017 MY engine standards.) The 2017 MY vehicle standards are not premised on 

manufacturers installing additional vehicle technologies. 
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Table II-8: Proposed Class 2b-8 Vocational Truck CO2 and Fuel Consumption Standards 

EPA CO2 (gram/ton-mile) Standard Effective 2014 Model Year

Light Heavy 

Class 3-5

Medium Heavy 

Class 6-7

Heavy Heavy 

Class 8

CO2 Emissions 420 249 101

NHTSA Fuel Consumption (gallon per 1000 ton-mile) Standard Effective 2016 Model 

Year83

Light Heavy 

Class 3-5

Medium Heavy 

Class 6-7

Heavy Heavy 

Class 8

Fuel Consumption 41.3 24.5 9.9

EPA CO2 (gram/ton-mile) Standard Effective 2017 Model Year

Light Heavy 

Class 3-5

Medium Heavy 

Class 6-7

Heavy Heavy 

Class 8

CO2 Emissions 404 240 100

NHTSA Fuel Consumption (gallon per ton-mile) Standard Effective 2017-18 Model Year

Light Heavy 

Class 3-5

Medium Heavy 

Class 6-7

Heavy Heavy 

Class 8

Fuel Consumption 39.7 23.6 9.8

(i) Off-Road Vocational Truck Standards

In developing the proposal EPA and NHSTA received comment from 

manufacturers and owners that trucks sometimes have very limited on-road usage. These 

trucks by definition of Title 40, Part 85.1703 are motor vehicles, but will spend the 

majority of their operations off-road. Trucks, such as those used in oil fields, will 

experience little benefit from low rolling resistance tires. The agencies are therefore 

proposing to allow a narrow range of these de facto off-road trucks to be excluded from 

the proposed vocational truck standards because the trucks require special off-road tires 

such as lug tires. The trucks must still use a certified engine, which will provide fuel 

consumption and CO2 emission reductions to the truck in all applications. To insure the 

limited use of these trucks, the agencies are proposing requirements that the vehicles have 

off-road tires, have limited high speed operation, and are designed for specific off-road 

applications. The agencies are proposing that a truck must meet the following 

requirements to qualify for an exemption from the vehicle standards for vocational 

trucks:

 Installed tires which are lug tires or contain a speed rating of less than or 

equal to 60 mph; and

 Include a vehicle speed limiter governed to 55 mph.

 

83 Manufacturers may voluntarily opt-in to the NHTSA fuel consumption program in 2014 or 2015. If a 

manufacturer opts-in, the program becomes mandatory.
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EPA and NHTSA have concluded that the onroad performance losses and 

additional costs to develop a truck which meets these specifications will limit the 

exemption to trucks built for the desired purposes. The agencies welcome comment on 

the proposed requirements and exemptions.

(b) Proposed Heavy Duty Engine Standards

EPA is proposing GHG standards84 and NHTSA is proposing fuel consumption 

standards for new heavy duty engines installed in vocational trucks. The standards will 

vary depending on whether the engines are diesel or gasoline powered. The agencies' 

analyses, as discussed briefly below and in more detail later in this preamble and in the 

Draft RIA Chapter 2, show that these standards are appropriate and feasible under each 

agency’s respective statutory authorities. 

The agencies have analyzed the feasibility of achieving the GHG and fuel 

consumption standards, based on projections of what actions manufacturers are expected 

to take to reduce emissions and fuel consumption. EPA and NHTSA also present the 

estimated costs and benefits of the heavy duty engine standards in Section III. In 

developing the proposed rules, the agencies have evaluated the kinds of technologies that 

could be utilized by engine manufacturers compared to a baseline engine, as well as the 

associated costs for the industry and fuel savings for the consumer and the magnitude of 

the GHG and fuel consumption savings that may be achieved.

With respect to the lead time and cost of incorporating technology improvements 

that reduce GHG emissions and fuel consumption, the agencies place important weight 

on the fact that during MYs 2014-2017 engine manufacturers are expected to redesign 

and upgrade their products only once. Over these four model years there will be an 

opportunity for manufacturers to evaluate almost every one of their engine models and 

add technology in a cost-effective way to control GHG emissions and reduce fuel 

consumption. The time-frame and levels for the standards, as well as the ability to 

average, bank and trade credits and carry a deficit forward for a limited time, are 

expected to provide manufacturers the time needed to incorporate technology that will 

achieve the proposed GHG and fuel consumption reductions, and to do this as part of the 

normal engine redesign process. This is an important aspect of the proposed rules, as it 

will avoid the much higher costs that would occur if manufacturers needed to add or 

change technology at times other than these scheduled redesigns. This time period will 

also provide manufacturers the opportunity to plan for compliance using a multi-year 

time frame, again in accord with their normal business practice. Further details on lead 

time, redesigns and technical feasibility can be found in Section III.

EPA’s existing non-GHG emissions regulations for heavy duty on highway 

engines establish four regulatory categories (three for compression-ignition or diesel 

engines and one for spark ignition or gasoline engines) that represent the engine’s 

 

84 Specifically, EPA is proposing CO2, N2O, and CH4 emissions standards for new heavy duty engines over 

an EPA specified useful life period (see Section II.II. E. for the N2O, and CH4 standards).
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intended and primary truck application, as shown in Table II-9.

85

 All heavy duty engines 

are covered either under the heavy duty pickup truck and van category or under the heavy 

duty engine standards. 

Table II-9: Engine Regulatory Subcategories

Engine Category Intended Application

Light Heavy Duty Diesel (LHDD) Class 2b through Class 5 trucks (8,501 

through 19,500 pounds GVWR)

Medium Heavy Duty Diesel (MHDD) Class 6 and Class 7 trucks (19,501 through 

33,000 pounds GVWR)

Heavy Heavy Duty Diesel (HHDD) Class 8 trucks (33,001 pounds and greater 

GVWR

Gasoline Incomplete vehicles less than 14,000 

pounds GVWR and all vehicles (complete 

or incomplete) greater than 14,000 pounds 

GVWR

For the purposes of the GHG engine emissions and engine fuel consumption 

standards that EPA and NHTSA are proposing today, the agencies intend to maintain 

these same four regulatory subcategories for GHG engine emissions standards and fuel 

consumption standards. This category structure would enable the agencies to set 

standards that appropriately reflect the technology available for engines for use in each 

type of vehicle.

(i) Diesel Engine Standards

EPA's proposed heavy duty diesel engine CO2 emission standards are presented in 

Table II-10. Similar to EPA’s non-GHG standards approach, manufacturers may

generate and use credits to show compliance with the standards. The EPA standards 

become effective in 2014, with more stringent standards becoming effective in model 

year 2017. Recently, EPA’s non-GHG heavy duty engine program provided new 

emissions standards for the industry in three year increments. Largely, the heavy duty 

engine and truck manufacturer product plans have fallen into three year cycles to reflect 

this environment. The proposed two-step CO2 emission standards recognize the 

opportunity for technology improvements over this timeframe while reflecting the typical 

diesel truck manufacturer product plan cycles.

NHTSA’s fuel consumption standards, also presented in Table II-10, would 

contain a voluntary opt-in to the engine program starting in 2014 model year, with 

mandatory engine standards starting in 2017 model year, synchronizing with EPA’s 2017 

model year standards. A manufacturer may opt-in to NHTSA’s voluntary standards in 

2014, 2015 or 2016. Once a manufacturer opts-in the standards become mandatory for 

the opt-in and subsequent model years, and the manufacturer may not reverse its 

 

85 See § 1036.140 LHDD, MHDD, HHDD intended categories
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decision. To opt into the program, a manufacture must declare its intent to opt in to the 

program with documented communication of the intent, at the same time it submits the 

Pre-Certification Compliance Report. See draft regulatory text for 49 CFR 535.8 for 

information related to the Pre-Certification Compliance Report. A manufacturer opting 

into the program would begin tracking credits and debits beginning in the model year in 

which they opt into the program.

The agencies are proposing the same standard level for the Light Heavy and 

Medium Heavy diesel engine categories. The agencies found that there is an overlap in 

the displacement of engines which are currently certified as LHDD or MHDD. The 

agencies developed the baseline 2010 model year CO2 emissions from data provided to 

EPA by the manufacturers during the non-GHG certification process. Analysis of CO2

emissions from 2010 model year LHDD and MHDDD engines showed little difference 

between LHDD and MHDD baseline CO2 performance, which overall averaged 630 g 

CO2/bhp-hr (6.19 gal/100 bhp-hr),

86 in the 2010 model year. Furthermore, the 

technologies available to reduce fuel consumption and CO2 emissions from these two 

categories of engines are similar. The agencies are proposing to maintain these two 

separate engine categories with the same standard level (instead of combining into a 

single category) to respect the different useful life periods associated with each category. 

The agencies are proposing to evaluate compliance with the LHD/MHD standards based 

on the heavy duty FTP engine cycle. 

The agencies found a difference in the baseline 2010 model year CO2 and fuel 

consumption performance between the LHDD/MHDD engines, which averaged 630 g 

CO2/bhp-hr (6.19 gal/100 bhp-hr)87, and the HHDD engines, which averaged 584 g 

CO2/bhp-hr (5.74 gal/100 bhp-hr). The HHDD data is also based on manufacturer 

submitted CO2 data for non-GHG emissions certification process. In addition, the 

agencies believe that there may be some technologies available to reduce fuel 

consumption and CO2 emissions that may not be appropriate for both the LHDD/MHDD 

and the HHDD engines, such as turbocompounding. Therefore, the agencies are 

proposing a standard level for HHDD engines which differs from the LHDD/MHDD 

standard level.

We are proposing standards based on the FTP procedure for vocational truck 

engines reflecting their primary use in transient operating conditions typified by both 

frequent accelerations and decelerations as well as some steady cruise conditions as 

represented on the FTP. The primary reason the agencies are proposing to set two 

separate HHDD engine standards is to encourage engine manufacturers to install 

technologies appropriate to the intended use of the engine with the vehicle. Tractors 

spend the majority of their operation at steady state conditions, and will obtain in-use 

benefit of technologies such as turbocompounding and other waste heat recovery

 

86 Calculated using the conversion 8887 g CO2/gallon for gasoline and 10,180 g CO2/gallon for diesel fuel. 

[site source]

87 Calculated using the conversion 8887 g CO2/gallon for gasoline and 10,180 g CO2/gallon for diesel fuel. 

[site source]
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technologies during this kind of typical engine operation. Therefore, the engines installed 

in line haul tractors would be required to meet the standard based on the SET, which is a 

steady state test cycle. On the other hand, vocational vehicles such as urban delivery

trucks spend more time operating in transient conditions and may not realize the benefit 

of this type of technology in-use. The use of an FTP test procedure for these engines will 

focus engine design on technologies that realize in-use benefits during the kind of 

operation typical for these engines. Therefore, we are proposing that engines installed in 

vocational vehicles be required to meet the standard and demonstrate compliance over the 

engine FTP cycle, which uses a transient test cycle. The levels of the standards reflect 

the difference in baseline emissions for the different test procedures. 

The engine standards that EPA is proposing and the voluntary opt-in standards 

being proposed by NHTSA for the 2014 model year would require diesel engine 

manufacturers to achieve on average a three percent reduction in fuel consumption and 

CO2 emissions over the baseline 2010 model year performance for the HHDD engines 

and a five percent reduction for the LHDD and MHDD engines. The agencies’ 

assessment of the NAS report and other literature sources indicates that there are 

technologies available to reduce fuel consumption by this level in the proposed timeframe 

in a cost-effective manner. These technologies include improved turbochargers, 

aftertreatment optimization, low temperature exhaust gas recirculation, and engine 

friction reductions. Additional discussion on technical feasibility is included in Section 

III below and in DRIA Chapter 2.

Additionally, the agencies are proposing that diesel engines further reduce fuel 

consumption and CO2 emissions from the 2010 model year baseline in 2017 model year. 

The proposed 2017 model year standards for the LHDD and MHDD engines represent a 

9 percent reduction from the 2010 model year. The proposed reductions represent on 

average a five percent decrease over the 2010 baseline for HHDD engines required to use 

the FTP standard. The additional reductions may be achieved through the increased 

development of the technologies evaluated for 2014 model year. The agencies’ analysis 

indicates that this type of advanced engine development will require a longer 

development time than the 2014 model year and therefore are proposing to provide 

additional lead time to allow for its introduction. 

Similar to EPA’s non-GHG standards approach, manufacturers may generate and 

use credits by the same engine category to show compliance with both agencies’ 

standards.
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Table II-10: Proposed Diesel Engine Standards

Effective 2014 Model Year

Light Heavy 

Diesel - FTP

Medium Heavy 

Diesel - FTP

Heavy Heavy 

Diesel - FTP

CO2 Standard 

(g/bhp-hr)

600 600 567

Optional Fuel 

Consumption 

Standard 

(gallon/100 bhphr)

5.89 5.89 5.57

Effective 2017 Model Year

Light Heavy 

Diesel - FTP

Medium Heavy 

Diesel - FTP

Heavy Heavy 

Diesel - FTP

CO2 Standard 

(g/bhp-hr)

576 576 555

Fuel 

Consumption 

(gallon/100 bhphr)

5.57 5.57 5.45

In proposing these standards for diesel engines used in vocational trucks, the 

agencies have looked primarily at the typical performance levels of the majority of 

engines in the fleet. We recognize however that when regulating a category of products 

for the first time, there will be individual products that may deviate from this baseline 

level of performance. Recognizing that for these products a reduction from the industry

baseline may be more costly than the agencies have assumed or perhaps even not feasible 

in the timing of these standards, EPA and NHTSA are proposing a regulatory alternative 

whereby a manufacturer could comply with a unique standard based on a five percent 

reduction from the products own 2011 baseline level. Our assessment is that this five

percent reduction is appropriate and technologically feasible given the same technology

packages and cost we have estimated for the primary program. We do not believe this 

alternative needs to continue past 2016 since manufacturers will have had ample 

opportunity to benchmark competitive products and make appropriate changes to bring 

their product performance into line with the rest of the industry. However, we are 

requesting comment on the potential to extend this regulatory alternative for one 

additional year for a single engine family with performance measured in that year as nine

percent beyond the engine’s own 2011 baseline level. We also request comment on the 

level of reduction beyond the baseline that is appropriate in this alternative. The five

percent level reflects the aggregate improvement beyond the baseline we are requiring of 

the entire industry. As this provision is intended to address potential issues for legacy

products that we would expect to be replaced or significantly improved at the 

manufacturer’s next product change, we request comment if a two percent reduction 

would be more appropriate. We would consider two percent rather than five percent if 

we were convinced that making all of the changes we have outlined in our assessment of 

the technical feasibility of the standards was not possible for some engines due to legacy
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design issues that will change in the future. We are proposing that manufacturers making 

use of these provisions would not be able to generate emissions credits from other 

engines in the same regulatory category as the engines complying using this alternate 

approach.

(ii) Gasoline Engine Standard

Heavy duty gasoline engines are typically used in vocational truck applications. 

The number of engines certified in the past for this segment of vehicles is very limited 

and has ranged between three and five engine models. Unlike the purpose built heavyduty diesel engines typical of this segment, these gasoline engines are developed for 

heavy duty pickup trucks and vans primarily, but are also sold as loose engines to 

vocational truck manufacturers. Therefore, the agencies evaluated these engines in 

parallel with the heavy duty pickup truck and van standard development. As with the 

pickup truck and van segment, the agencies anticipate that the manufacturers will have 

only one engine re-design within the 2014-18 model years under consideration within this 

proposal. In our meetings with all three of the major manufacturers in this segment, 

confidential future product plans were shared with the agencies. Reflecting those plans 

and our estimates for when engine changes will be made in alignment with those product 

plans, we have concluded that the 2016 model year reflects the most logical model year 

start date for the heavy-duty gasoline engine standards. In order to meet the standards we 

are proposing for heavy-duty pickups and vans, we project that all of the OEMs will have 

redesigned their gasoline engine offerings by the start of the 2016 model year. Given the 

small volume of loose gasoline engine sales relative to complete heavy-duty pickup sales, 

we think it is appropriate to set the timing for the heavy-duty gasoline engine standard 

inline with our projections for engine redesigns to meet the heavy-duty pickup truck 

standards. Therefore, NHTSA’s proposed fuel consumption standard and EPA’s 

proposed CO2 standard for heavy duty gasoline engines are first effective in the 2016 

model year. 

The baseline 2010 model year CO2 performance of these heavy duty gasoline 

engines over the FTP cycle is 660 g CO2/bhp-hr (6.48 gal/100 bhp-hr) in 2010 based on 

non-GHG certification data provided to EPA by the manufacturers. The agencies 

propose that manufacturers achieve a 5 percent reduction in CO2 in the 2016 model year 

over the 2010 MY baseline through technologies such as coupled cam phasing, engine 

friction reduction, and stoichiometric direct injection. Additional detail on technology

feasibility is included in Section III and in the DRIA Chapter 2.

NHTSA is proposing a 7.05 gallon/100 bhp-hr standard for fuel consumption 

while EPA is proposing a 627 g CO2/bhp-hr standard tested over the FTP effective in 

2016 model year. Similar to EPA’s non-GHG standards approach, manufacturers may

generate and use credits by the same engine category to show compliance with both 

agencies' standards.

In the preceding section on diesel engines, we describe an alternative compliance 

approach for diesel engines based on improvements from an engine’s own baseline of 

performance. We are not making a similar proposal for gasoline engines, but we request 
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comment on the need for and appropriateness of such an approach. Comments 

suggesting the need for a similar approach should include specific recommendations on 

how the approach would work and the technical reasons why such an approach would be 

necessary in order to make the gasoline engine standards feasible.

(c) In-Use Standards

Section 202(a)(1) of the Clean Air Act specifies that emissions standards are to be 

applicable for the useful life of the vehicle. The in-use standards that EPA is proposing 

would apply to individual vehicles and engines. NHTSA is not proposing to adopt in-use 

standards that would apply to the vehicles and engines in a similar fashion. 

EPA is proposing that the in-use standards for heavy duty engines installed in 

vocational trucks be established by adding an adjustment factor to the full useful life 

emissions and fuel consumption results. EPA is proposing a 2 percent adjustment factor 

for the in-use standard to provide some margin for production and test-to-test variability

that could result in differences between the initial emission test results and emission 

results obtained during subsequent in-use testing. 

EPA is proposing that the useful life for these engine and vehicles with respect to 

GHG emissions be set equal to the respective useful life periods for criteria pollutants. 

EPA proposes that the existing engine useful life periods88, as included in Table II-11, be 

broadened to include CO2 emissions and fuel consumption for both engines and tractors.

While NHTSA proposes to use useful life considerations for establishing fuel 

consumption performance for initial compliance and for ABT, NHTSA does not intend to 

implement an in-use compliance program for fuel consumption, because it is not required 

under EISA and because it is not currently anticipated there will be notable deterioration 

of fuel consumption over the engines’ useful life. 

Table II-11: Proposed Useful Life Periods

Years Miles

Class 2b-5 Trucks, Spark Ignited (SI), 

and Light Heavy Duty Diesel Engines

10 110,000

Class 6-7 Trucks and Medium Heavy 

Duty Diesel Engines

10 185,000

Class 8 Trucks and Heavy Heavy

Duty Diesel Engines

10 435,000

EPA requests comments on the magnitude and need for an in-use adjustment 

factor for the engine standard and the compliance model [TEST] based chassis standard.

 

88 40 CFR § 86.004-2
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(2) Test Procedures and Related Issues

The agencies are proposing test procedures to evaluate fuel consumption and CO2

emissions of vocational trucks in a manner very similar to Class 7 and Class 8 

combination tractors. This section describes a simulation model for demonstrating 

compliance, engine test procedures, and a test procedure for evaluating hybrid 

powertrains (a potential means of generating credits, although not part of the technology

on which the proposed standard is premised).

(a) Computer Simulation Model

As previously mentioned, to achieve the goal of reducing emissions and fuel 

consumption for both trucks and engines, we are proposing to set separate engine and 

vehicle-based emission standards. For the vocational trucks, engine manufacturers would 

be subject to the engine standards, and chassis manufacturers would be required to install 

certified engines in their chassis. The chassis manufacturer would be subject to a 

separate vehicle-based standard that would use the proposed truck simulation model to 

evaluate the impact of the tire design to determine compliance with the truck standard. 

A simulation model, in general, uses various inputs to characterize a vehicle’s 

properties (such as weight, aerodynamics, and rolling resistance) and predicts how the 

vehicle would behave on the road when it follows a driving cycle (vehicle speed versus 

time). On a second-by-second basis, the model determines how much engine power 

needs to be generated for the vehicle to follow the driving cycle as closely as possible. 

The engine power is then transmitted to the wheels through transmission, driveline, and 

axles to move the vehicle according to the driving cycle. The second-by-second fuel 

consumption of the vehicle, which corresponds to the engine power demand to move the 

vehicle, is then calculated according to the fuel consumption map embedded in the 

compliance model. Similar to a chassis dynamometer test, the second-by-second fuel 

consumption is aggregated over the complete drive cycle to determine a fuel consumption 

of the vehicle.

NHTSA and EPA are proposing to evaluate fuel consumption and CO2 emissions 

respectively through a simulation of whole-vehicle operation, consistent with NAS 

recommendation to use a truck model to evaluate truck performance. The agencies 

developed the Truck Efficiency Simulation Tool [TEST] for the specific purpose of this 

proposal to evaluate truck performance. The [TEST] model is similar in concept to a 

number of vehicle simulation tools developed by commercial and government entities. 

The model developed by the agencies and proposed here was designed for the express 

purpose of vehicle compliance demonstration and is therefore simpler and less 

configurable than similar commercial products. This approach gives a compact and 

quicker tool for vehicle compliance without the overhead and costs of a more 

sophisticated model. Details of the model are included in Chapter 4 of the DRIA.

[TEST] is designed to focus on the inputs most closely associated with fuel 

consumption and CO2 emissions - i.e. on those which have the largest impacts such as 

aerodynamics, rolling resistance, weight, and others. 
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EPA and NHTSA have validated [TEST] based on the chassis test results from 

three SmartWay certified tractors tested at Southwest Research Institute. The validation 

work conducted on these three vehicles is representative of the other Class 7 and 8 

tractors. Many aspects of one tractor configuration (such as the engine, transmission, 

axle configuration, tire sizes, and control systems) are similar to those used on the 

manufacturer’s sister models. For example, the powertrain configuration of a sleeper cab 

is similar to the one used on a straight truck. Details are included in DRIA Chapter 4. 

Overall, the [TEST] model predicted the fuel consumption and CO2 emissions within 4% 

of the chassis test procedure results for three test cycles – the ARB Transient cycle, ARB 

High Speed Cruise cycle, and the Low Speed Cruise cycle. These cycles are very similar 

to the ones the agencies are proposing to utilize in compliance testing. Test to test 

variation for heavy-duty vehicle chassis testing can be higher than 4 percent based on 

driver variation. The proposed simulation model is described in greater detail in DRIA 

Chapter 4 and is available for download by interested parts at (www.epa.gov/xxxxx). We 

request comment on all aspects of this approach to compliance determination in general 

and to the use of the [TEST] model in particular. 

The agencies are proposing that for demonstrating compliance, a chassis 

manufacturer would measure the performance of tires, input the values into [TEST], and 

compare the model’s output to the standard. Tires are the only technology on which the 

agencies’ own feasibility analysis for these vehicles is predicated. An example of the 

[TEST] input screen is included in Figure II-4. The input values for the simulation 

model would be derived by the manufacturer from tire test procedure proposed by the 

agencies in this proposal. The agencies are proposing that the remaining model inputs 

would be fixed values that are pre-defined by the agencies and are detailed in the draft 

RIA Chapter 3, including the engine fuel consumption map to be used in the simulation.
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Figure II-4: Example [TEST] Input Screen

(b) Tire Rolling Resistance Assessment

As with the Class 7/8 combination tractors, NHTSA and EPA are proposing that 

the vocational truck’s tire rolling resistance input to the [TEST] model be determined 

using the ISO 28580:2009 test method.89 The agencies believe the ISO test procedure is 

appropriate to propose for this program because the procedure is the same one used by

the NHTSA tire fuel efficiency labeling program90 and is consistent with the direction 

being taken by the tire industry both in the United States and Europe, and with the EPA 

SmartWay program. The rolling resistance from this test would be used to specify the 

rolling resistance of each tire on the steer and drive axle of the vehicle. The results would 

be expressed as a rolling resistance coefficient and measured as kilogram per ton 

(kg/metric ton). The agencies are proposing that three tire samples within each tire 

model be tested to account for some of the production variability and the average of the 

three tests would be the rolling resistance coefficient for the tire. 

(c) Defined Vehicle Configurations in the [TEST] model

As discussed above, the agencies are proposing a methodology that chassis 

manufacturers would use to quantify the tire rolling resistance values to be input into the 

[TEST]. Moreover, the agencies are proposing to define the remaining [TEST] model 

inputs (i.e. specify them by rule), which may differ by the regulatory category (for 

reasons described in the DRIA). The defined inputs being proposed include the drive 

cycle, aerodynamics, truck curb weight, payload, engine characteristics, and drivetrain 

for each vehicle type, among others.

(i) Metric

Based on NAS’s recommendation and feedback from the heavy duty truck 

industry, NHTSA and EPA are proposing standards for vocational trucks that would be 

expressed in terms of moving a ton of payload over one mile. Thus, NHTSA's proposed 

fuel consumption standards for these trucks would be represented as gallons of fuel used 

to move one ton of payload thousand miles, or gal/1000 ton-mile. EPA's proposed CO2

vehicle standards would be represented as grams of CO2 per ton-mile. 

(ii) Drive cycle

The drive cycle being proposed for the vocational trucks consists of the same 

three modes proposed for the Class 7-8 combination tractors. The agencies are thus 

proposing the use of the Transient mode, as defined by ARB in the HHDDT cycle, a 

 

89 ISO, 2009, Passenger Car, Truck, and Bus Tyres – Methods of Measuring Rolling Resistance – Single 

Point Test and Correlation of Measurement Results: ISO 28580:2009(E), First Edition, 2009-07-01

90 NHTSA, 2009. “NHTSA Tire Fuel Efficiency Consumer Information Program Development: Phase 1 –

Evaluation of Laboratory Test Protocols.” DOT HS 811 119. June. (www.regulations.gov, Docket ID: 

NHTSA-2008-0121-0019).
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constant speed cycle at 65 mph and a 55 mph constant speed mode. However, we are 

proposing different weightings for each mode than proposed for Class 7/8 combination 

tractors, given the known difference in driving patterns between these two categories of 

vehicles. 

The variety of vocational vehicle applications makes it challenging to establish a 

single cycle which is representative of all such trucks. However, in aggregate, the 

vocational vehicles typically operate over shorter distances and spend less time cruising 

at highway speeds than combination tractors. The agencies evaluated two sources for 

mode weightings, as detailed in DRIA Chapter 3. The agencies are proposing the mode 

weightings based on the vehicle speed characteristics of single unit trucks used in EPA’s 

MOVES model which were developed using Federal Highway Administration data to 

distribute vehicle miles traveled by road type.91 The proposed weighted CO2 and fuel 

consumption value consists of 37 percent of 65 mph Cruise, 21 percent of 55 mph Cruise, 

and 42 percent of Transient performance, which are reflected in the [TEST] model.

(iii) Empty Weight and Payload

The total weight of the truck is the sum of the tractor curb weight and the payload. 

The agencies are proposing to specify each of these aspects of the vehicle. The agencies 

developed the truck curb weight inputs based on industry information developed by

ICF.92 The proposed curb weights are 10,300 pounds for the LH trucks, 13,950 pounds 

for the MH trucks, and 29,000 pounds for the HH trucks. 

NHTSA and EPA are also proposing the following payload requirement for each 

regulatory category. The payloads were developed from Federal Highway statistics 

based on averaging the payloads for the weight categories represented within each 

vehicle category.

93

 The proposed payload requirement is 5,700 pounds for the Light 

Heavy trucks, 11,200 pounds for Medium Heavy trucks, and 38,000 pounds for Heavy

Heavy trucks. Additional information is available in DRIA Chapter 3.

(iv) Engine

As the agencies are proposing separate engine and truck standards, the [TEST] 

model will be used to assess the compliance of the chassis with the truck standard. To 

maintain the separate assessments, the agencies are proposing to use fixed values that are 

pre-defined by the agencies for the engine characteristics used in [TEST], including the 

fuel consumption map which provides the fuel consumption at hundreds of engine speed 

and torque points. If the agencies did not standardize the fuel map, then a truck that uses 

an engine with emissions and fuel consumption better than the standards would require 

 

91The Environmental Protection Agency. Draft MOVES2009 Highway Vehicle Population and Activity 

Data. EPA-420-P-09-001, August 2009 http://www.epa.gov/otaq/models/moves/techdocs/420p09001.pdf

92 ICF Cost Report. Need cite and docket #.

93 The U.S. Federal Highway Administration. Development of Truck Payload Equivalent Factor. Table 11. 

Last viewed on March 9, 2010 at 

http://ops.fhwa.dot.gov/freight/freight_analysis/faf/faf2_reports/reports9/s510_11_12_tables.htm
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fewer vehicle reductions than that being proposed. The agencies are proposing that the 

engine characteristics used in [TEST] be representative of a diesel engine, because it 

represents the largest fraction of engines in this market. 

The agencies are proposing two distinct sets fuel consumption maps for use in 

[TEST]. The first fuel consumption map would be used in [TEST] for the 2014 through 

2016 model years and represent a diesel engine which meets the 2014 model year engine 

CO2 emissions standards. A second fuel consumption map would be used beginning in 

the 2017 model year and represents a diesel engine which meets the 2017 model year 

CO2 emissions and fuel consumption standards and accounts for the increased stringency 

in the proposed MY 2017 standard). Effectively there is no change in stringency of the 

vocational vehicle (not including the engine) and there is stability in the vocational 

vehicle (not including engine) standards for the full rulemaking period. These inputs are 

reasonable given the separate proposed regulatory requirement that vocational truck 

chassis manufacturers use only certified engines. 

(v) Drivetrain

The agencies’ assessment of the current vehicle configuration process at the truck 

dealer’s level is that the truck companies provide software tools to specify the proper 

drivetrain matched to the buyer’s specific circumstances. These dealer tools allow a 

significant amount of customization for drive cycle and payload to provide the best 

specification for the customer. The agencies are not seeking to disrupt this process. 

Optimal drivetrain selection is dependent on the engine, drive cycle (including vehicle 

speed and road grade), and payload. Each combination of engine, drive cycle, and 

payload has a single optimal transmission and final drive ratio. The agencies are 

proposing to specify the engine’s fuel consumption map, drive cycle, and payload; 

therefore, it makes sense to specify the drivetrain that matches. 

In conclusion, for vocational trucks, compliance would be determined by

establishing values for the tire rolling resistance and using the prescribed inputs in 

[TEST]. The model would produce CO2 and fuel consumption results that would be 

compared against EPA's and NHTSA's respective standards. 

(d) Engine Test Procedures

The NAS panel did not specifically discuss or recommend a metric to evaluate the 

fuel consumption of heavy duty engines. However, as noted above they did recommend 

the use of a load specific fuel consumption metric for the evaluation of vehicles.94 An 

analogous metric for engines would be the amount of fuel consumed per unit of work. 

Thus, EPA is proposing that GHG emission standards for engines under the CAA would 

be expressed as grams of emissions per brake horsepower-hour (g/bhp-hr): similarly, 

NHTSA's proposed fuel consumption standards under EISA would be represented as 

 

94 March 2010 NAS Report. Page 2-40.
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gallons of fuel per 100 horsepower-hour (gal/100 bhp-hr). EPA’s metric is also 

consistent with EPA’s current standards for non-GHG emissions for these engines.

EPA’s criteria pollutant standards for engines currently require that manufacturers 

demonstrate compliance over a transient test cycle, the FTP; a steady-state test cycle, the 

SET or supplemental emissions test; and the not-to-exceed, or NTE test. EPA created 

this multi-layered approach to criteria emissions control in response to engine designs 

that optimized operation for lowest fuel consumption at the expense of very high criteria 

emissions when operated off the regulatory cycle. EPA’s use of multiple test procedures 

for criteria pollutants helps to ensure that manufacturers calibrate engine systems for 

compliance under all operating conditions. With regard to GHG and fuel consumption 

control, the agencies believe it is more appropriate to set standards based on a single test 

procedure, either the FTP or SET, depending on the primary expected use of the engine. 

For engines used primarily in combination tractor trailer operations, we believe 

the steady-state SET procedure more appropriately reflects in-use engine operation. By

setting standards based on the most representative test cycle, we can have confidence 

OEMs will design engines for best GHG and fuel consumption performance relative to 

the most common type of expected engine operation. We are not concerned if off-cycle, 

manufacturers further calibrate these designs to give better in-use fuel consumption while 

maintaining compliance with the criteria emissions standards as such calibration is 

entirely consistent with the goals of our joint program. Further, we believe that setting 

standards based on both transient and steady-state operating conditions for all engines 

could lead to undesirable outcomes. For example, turbocompounding is one technology

that the agencies have identified as a likely approach for compliance against our proposed 

HHD SET standard described below. Turbocompounding is a very effective approach to 

lower fuel consumption under steady driving conditions typified by combination tractor 

trailer operation and is well reflected in testing over the SET test procedure. However, 

when used in driving typified by transient operation as we expect for vocational trucks 

and as is represented by the FTP, turbocompounding shows very little benefit. Setting an 

FTP based standard for engines intended for use in combination tractor trailers could lead 

manufacturers to not apply turbocompounding even though it can be a highly cost 

effective means to reduce GHG emissions and lower fuel consumption. 

The current non-GHG emissions engine test procedures also require the 

development of regeneration emission rates and frequency factors to account for the 

emission changes during a regeneration event.95 EPA and NHTSA are proposing to 

exclude the CO2 emissions and fuel consumption increases due to regeneration from the 

calculation of the compliance levels over the defined test procedures. We considered 

including regeneration in the estimate of fuel consumption and GHG emissions and have 

decided not to do so for two reasons. First, EPA’s existing criteria emission regulations 

already provide a strong motivation to engine manufacturers to reduce the frequency and 

duration of infrequent regeneration events. The very stringent 2010 NOx emission 

 

95 40 CFR § 86.004-28
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standards cannot be met by engine designs that lead to frequent and extend regeneration 

events. Hence, we believe engine manufacturers are already reducing regeneration 

emissions to the greatest degree possible. In addition to believing that regenerations are 

already controlled to the extent technologically possible, we believe that attempting to 

include regeneration emissions in the standard setting could lead to an inadvertently lax 

emissions standard. In order to include regeneration and set appropriate standards, EPA 

and NHTSA would have needed to project the regeneration frequency and duration of 

future engine designs in the timeframe of this proposal. Such a projection would be 

inherently difficult to make and quite likely would underestimate the progress engine 

manufacturers will make in reducing infrequent regenerations. If we underestimated that 

progress, we would effectively be setting a more lax set of standards than otherwise 

would be expected. Hence in setting a standard including regeneration emissions we 

faced the real possibility that we would achieve less effective CO2 emissions control and 

fuel consumption reductions than we will achieve by not including regeneration 

emissions. We are seeking comments regarding regeneration emissions and what 

approach if any the agencies should use in reflecting regeneration emissions in this 

program. 

(e) Hybrid Powertrain Technology

Although the proposed vocational vehicle standards are not premised on use of 

hybrid powertrains, certain vocational truck applications may be suitable candidates for 

use of hybrids due to the greater frequency of stop-and-go urban operation and their use 

of power take-off systems. Examples are vocational vehicles used predominantly in stopstart urban driving (e.g. delivery trucks). As an incentive, the agencies are proposing to 

provide credits for the use of hybrid powertrain technology as described in Section IV. 

The agencies are proposing that any credits generated using such technologies could be 

applied to any heavy duty vehicle or engine, and not be limited to the vehicle category

generating the credit. Section IV below also details the proposed approach to account for 

the use of a hybrid powertrain when evaluating compliance with the truck standard. In 

general, manufacturers can derive the fuel consumption and CO2 emissions reductions 

based on comparative test results using the proposed chassis testing procedures. We are 

proposing the same three drive cycles and cycle weightings discussed for the vocational 

vehicles to evaluate trucks that use hybrid powertrains to power the vehicle during 

motive operation (such as pickup and delivery trucks and transit buses). However, we are 

proposing an additional power take-off (PTO) test cycle for trucks which use a PTO to 

power equipment while the vehicle is either idling or moving (such as bucket or refuse 

trucks). The reductions due to the hybrid technology would be calculated relative to the 

same type of vehicle with a conventional powertrain tested using the same protocol.

(3) Summary of proposed flexibility and credit provisions

EPA and NHTSA are proposing a number of flexibility provisions for vocational 

truck chassis manufacturers and engine manufacturers, as discussed in Section IV below. 

These provisions are all based on an averaging, banking and trading program for 

emissions and fuel consumption credits. They include provisions to encourage the 

introduction of advanced technologies such as hybrid drivetrains, provisions to 
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incentivize early compliance with the proposed standards, and provisions to allow 

compliance using innovative technologies unanticipated by the agencies in developing 

this proposal. 

(4) Deferral of standards for small chassis manufacturing and small engine 

companies

EPA and NHTSA are proposing to defer greenhouse gas emissions and fuel 

consumption standards from small truck chassis manufacturers meeting the Small 

Business Administration (SBA) size criteria of a small business as described in 13 CFR 

121.201.96 The agencies will instead consider appropriate GHG and fuel consumption 

standards for these entities as part of a future regulatory action. This includes both U.S.-

based and foreign small volume heavy duty tractor manufacturers.

The agencies have identified ten chassis entities that appear to fit the Small 

Business Administration (SBA) size criterion of a small business.97 The agencies estimate 

that these small entities comprise less than 0.5 percent of the total heavy-duty vocational 

truck market in the U.S. based on Polk Registration Data from 2003 through 2007,98 and 

therefore that the exemption will have a negligible impact on the GHG emissions and fuel 

consumption improvements from the proposed standards. 

EPA and NHTSA have also identified three entities that appear to fit the Small 

Business Administration (SBA) size criteria of a small business based on company

information included in Hoover’s.99 Based on 2008 and 2009 model year engine 

certification data submitted to EPA for non-GHG emissions standards, the agencies 

estimate that these small entities comprise less than 0.1 percent of the total heavy-duty 

engine sales in the U.S. The proposed exemption from the standards established under 

this proposal would have a negligible impact on the GHG emissions and fuel 

consumption reductions otherwise due to the standards. 

E. EPA’s Proposed N20 and CH4 Standards

In addition to proposing CO2 emission standards for heavy duty vehicles and 

engines, EPA is also proposing separate standards for nitrous oxide (N2O) and methane 

(CH4) emissions.100 NHTSA is not proposing comparable separate standards for these 

GHGs because they are not directly related to fuel consumption in the same way that 

CO2 is, and NHTSA’s authority under EISA relates to fuel efficiency. N2O and CH4 are 

 

9640 CFR §§ 1036.150 and 10367.150

97 The agencies have identified Lodal, Indiana Phoenix, Autocar LLC, HME, Giradin, Azure Dynamics, 

DesignLine International, Ebus, Krystal Koach, and Millenium Transit Services LLC as potential small 

business chassis manufacturers.

98 M.J. Bradley. Heavy Duty Vehicle Market Analysis. May 2009.

99 The agencies have identified Baytech Corporation, Clean Fuels USA, and BAF Technologies, Inc. as 

three potential small businesses.

100 NHTSA's statutory responsibilities relating to reducing fuel consumption are directly related to reducing 

CO2 emissions, but not to the control of other GHGs.
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important GHGs that contribute to global warming, more so than CO2 for the same 

amount of emissions due to their high Global Warming Potential (GWP).101 EPA is 

proposing N2O and CH4 standards which apply to HD pickup trucks and vans as well as 

all heavy duty engines. EPA is not proposing N2O and CH4 standards for the Class 7/8 

tractor or Class 2b-8 chassis manufacturers because they are being controlled through the 

engine program.

Almost universally across current engine designs, both gasoline- and dieselfueled, N2O and CH4 emissions are relatively low today and EPA does not believe it 

would be appropriate or feasible to require reductions from the levels of current gasoline 

and diesel engines because current heavy duty criteria pollutant emission standards 

indirectly result in control of N2O and CH4. Additionally, unlike criteria pollutants, 

specific technologies beyond those presently implemented in heavy duty vehicles to meet 

existing emission requirements have not surfaced that target reductions in N2O or CH4. 

Because of this, reductions in N2O or CH4 beyond current levels would likely result in an 

increase in the overall stringency of the criteria emission standards. Nevertheless, it is 

important that future engine technologies or fuels not currently researched do not result in 

increases in these emissions, and this is the intent of the proposed “cap” standards. The 

proposed standards would act to cap emissions at today’s levels to ensure that 

manufacturers do not allow the N2O and CH4 emissions of their future engines to rise 

above current levels if they choose a different technology path from currently used and 

largely successful methods for controlling N2O and CH4. As discussed below, some 

technologies that manufacturers may adopt for reasons other than reducing fuel 

consumption or GHG emissions could increase N2O and CH4 emissions if manufacturers 

do not address these emissions in their overall engine and aftertreatment design and 

development plans. Manufacturers will be able to design and develop the engines and 

aftertreatment to avoid such emissions increases through appropriate emission control 

technology selections like those already used and available today. Because EPA believes 

that these standards can be capped at the same level, regardless of type of HD engine 

involved, the following discussion relates to all types of HD engines regardless of the 

vehicles in which such engines are ultimately used. In addition, since these standards are 

designed to cap current emissions, EPA is proposing the same standards for all of the 

model years to which the rules apply.

EPA believes that the proposed N2O and CH4 cap standards would accomplish the 

primary goal of preventing increases in these emissions as engine and aftertreatment 

technologies evolve because manufacturers will continue to target current or lower N2O 

and CH4 levels in order to maintain typical compliance margins. However, we also 

believe that an alternative compliance approach that allows manufacturers to convert 

these emissions to CO2-equivalent emission values and combine them with CO2 into a 

single compliance value would also be appropriate, so long as it did not undermine the 

stringency of the CO2 standard. As described below, EPA is proposing that such an 

 

101 N2O has a GWP of 298 and CH4 has a GWP of 25 according to the IPCC Fourth Assessment Report 

(AR4).
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alternative compliance approach be available to manufacturers to provide certain 

flexibilities for different technologies.

EPA requests comments on the approach to regulating N2O and CH4 emissions 

including the appropriateness of “cap” standards, the technical bases for the levels of the 

proposed N2O and CH4 standards, the proposed test procedures, and the proposed timing 

for the standards. In addition, EPA seeks any additional emissions data on N2O and CH4

from current technology engines.

(1) What is EPA’s proposed approach to controlling N2O?

N2O is a global warming gas with a global warming potential (GWP) of 310. It 

accounts for about 0.3% of the current greenhouse gas emissions from heavy duty 

trucks.102 

N2O is emitted from gasoline and diesel vehicles mainly during specific catalyst 

temperature conditions conducive to N2O formation. Specifically, N2O can be generated 

during periods of emission hardware warm-up when rising catalyst temperatures pass 

through the temperature window when N2O formation potential is possible. For current 

heavy duty gasoline engines with conventional three-way catalyst technology, N2O is not 

generally produced in significant amounts because the time the catalyst spends at the

critical temperatures during warm-up is short. This is largely due to the need to quickly

reach the higher temperatures necessary for high catalyst efficiency to achieve emission 

compliance of criteria pollutants. N2O is a more significant concern with diesel vehicles, 

and potentially with future gasoline lean-burn engines, equipped with advanced catalytic 

NOx emissions control systems. These systems can but need not be designed in a way

that emphasizes efficient NOx control while allowing the formation of significant 

quantities of N2O. Excess oxygen present in the exhaust during lean-burn conditions in 

diesel or lean-burn gasoline engines equipped with these advanced systems can favor 

N2O formation if catalyst temperatures are not carefully controlled. To prevent this 

trade-off, future designs and controls at reducing criteria emissions would need to take 

into account the balance of reducing these emissions while also preventing N2O 

formation much like the path taken in current heavy duty compliant engines and vehicles. 

Without specific attention to controlling N2O emissions in the development of such new 

NOx control systems, vehicles could have N2O emissions many times greater than are 

emitted by current gasoline vehicles. 

EPA is proposing an N2O emission standard that we believe would be met by

current-technology gasoline and diesel vehicles at essentially no cost. EPA believes that 

heavy duty emission standards since 2008 model year, specifically the very stringent 

NOX standards for both engine and chassis certified engines, directly result in stringent 

N2O control. It is believed that the current emission control technologies used to meet the 

stringent NOX standards achieve the maximum feasible reductions and that no additional 

technologies are recognized that would result in additional N2O reductions. As noted, 

 

102 Value adapted from “Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007. April 2009.
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N2O formation in current catalyst systems occurs, but their emission levels are inherently 

low, because the time the catalyst spends at the critical temperatures during warm-up 

when N2O can form is short. At the same time, we believe that the proposed standard 

would ensure that the design of advanced NOx control systems for future diesel and leanburn gasoline vehicles would control N2O emission levels. While current NOx control 

approaches used on current heavy duty diesel vehicles do not compromise N2O emissions 

and actually result in N2O control, we believe that the proposed standards would 

discourage any new emission control designs for diesels or lean-burn gasoline vehicles 

that achieve criteria emissions compliance at the cost of increased N2O emissions. Thus, 

the proposed standard would cap N2O emission levels, with the expectation that current 

gasoline and diesel vehicle control approaches that comply with heavy duty vehicle 

emission standards for NOx would not increase their emission levels, and that the cap 

would ensure that future diesel and lean-burn gasoline vehicles with advanced NOx 

controls would appropriately control their emissions of N2O. 

(a) Heavy-Duty Pickup Truck and Van Nitrous Oxide (N2O) Exhaust Emission 

Standard

EPA is proposing a per-vehicle N2O emission standard of 0.03 g/mi, measured 

over the combined-cycle FTP vehicle laboratory test. Similar to the CO2 standard 

approach, the N2O emission level of a vehicle would be a composite of the FTP city and 

highway cycles with the same 55% city weighting and 45% highway weighting. The 

standard would become effective in model year 2014 for all HD pickups and vans that are 

subject to the proposed CO2 emission requirements. Averaging between vehicles would 

not be allowed. The standard is designed to prevent increases in N2O emissions from 

current levels, i.e. a no-backsliding standard. 

The proposed N2O level is approximately two times the average N2O level of 

current gasoline and diesel heavy duty trucks that meet the NOx standards effective since 

2008 model year.103 Manufacturers typically use design targets for NOx emission levels 

at approximately 50% of the standard, to account for in-use emissions deterioration and 

normal testing and production variability, and we expect manufacturers to utilize a 

similar approach for N2O emission compliance. We are not proposing a more stringent 

standard for current gasoline and diesel vehicles because the stringent heavy duty NOx 

standards already result in significant N2O control, and we do not expect current N2O

levels to rise for these vehicles particularly with expected manufacturer compliance 

margins. 

Diesel heavy duty pickup trucks and vans with advanced emission control 

technology are in the early stages of development and commercialization. As this 

segment of the vehicle market develops, the proposed N2O standard would require 

manufacturers to incorporate control strategies that minimize N2O formation. Available 

approaches include using electronic controls to limit catalyst conditions that might favor 

 

103 Need to get this from MOVES and other test data.
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N2O formation and considering different catalyst formulations. While some of these 

approaches may have associated costs, EPA believes that they will be small compared to 

the overall costs of the advanced NOx control technologies already required to meet 

heavy duty standards.

The light-duty GHG rule requires that manufacturers begin testing for N2O by

2015 model year. The manufacturers of complete pickup trucks and vans (Ford, General 

Motors, and Chrysler) are already impacted by the light-duty GHG rule and will therefore 

have this equipment and capability in place for the timing of this proposal. 

Overall, we believe that manufacturers of HD pickups and vans (both gasoline 

and diesel) would meet the proposed standard without implementing any significantly

new technologies, only further refinement of their existing controls, and we do not expect 

there to be any significant costs associated with this standard. 

(b) Heavy Duty Engine Nitrous Oxide (N2O) Exhaust Emission Standard

EPA is also proposing a per engine N2O emissions standard of 0.05 g/bhp-hr for 

heavy duty engines which become effective in 2014 model year. These standards remain 

the same over the useful life of the engine. The N2O emissions would be measured over 

the heavy duty engine FTP cycle because it is believed that this cycle poses the highest 

risk for N2O formation versus the additional heavy duty compliance cycles. Averaging 

between vehicles would not be allowed. The standard is designed to prevent increases in 

N2O emissions from current levels, i.e. a no-backsliding standard.

The proposed N2O level is twice the average N2O level of current diesel engines 

as demonstrated in the ACES Study and in EPA’s testing of two additional engines with 

SCR aftertreatement systems.104 Manufacturers typically use design targets for NOX 

emission levels of about 50% of the standard, to account for in-use emissions 

deterioration and normal testing and production variability, and manufacturers are 

expected to utilize a similar approach for N2O emission compliance. EPA requests 

comment on the agency's technical assessment of current and potential future N2O 

formation in heavy duty engines, as presented here. 

Engine emissions regulations do not currently require testing for N2O. The 

Mandatory GHG Reporting final rule (MRR)105 requires reporting of N2O and requires 

that manufacturers either measure N2O or use a compliance statement based on good 

engineering judgment in lieu of direct N2O measurement. The light-duty GHG final 

rule106 allows manufacturers to provide a compliance statement based on good 

engineering judgment through the 2014 model year, but requires measurement beginning 

 

104 CRC Report: ACES Phase 1 of the Advanced Collaborative Emissions Study, 2009.(This study included 

detailed chemical characterization of exhaust species emitted from four 2007 model year heavy heavy 

diesel engines)

105 74 FR 56260, October 30, 2009

106 75 FR 25324 (May 7, 2010).
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in 2015 model year. EPA is proposing a consistent approach for heavy duty engine 

manufacturers which allows them to start direct measurement of N2O in the 2015 model 

year. EPA welcomes comments on whether there are differences in the heavy duty 

market which would warrant a different approach.

Manufacturers without the capability to measure N2O by the 2015 model year 

would need to acquire and install appropriate measurement equipment in response to this 

proposed program. EPA has established four separate N2O measurement methods, all of 

which are commercially available today. EPA expects that most manufacturers would 

use photo-acoustic measurement equipment, which EPA estimates would result in a onetime cost of about $50,000 for each test cell that would need to be upgraded. 

Overall, EPA believes that manufacturers of heavy duty engines, both gasoline 

and diesel, would meet the proposed standard without implementing any new 

technologies, and beyond relatively small facilities costs for any companies that still need 

to acquire and install N2O measurement equipment, EPA does not project that 

manufacturers would incur significant costs associated with this proposed N2O standard. 

EPA is not proposing any vehicle-level N2O standards for heavy duty trucks 

(combination and vocational) in this proposal. The N2O emissions would be controlled 

through the heavy duty engine portion of the program. The only requirement of those 

truck manufacturers to comply with the N2O requirements is to install a certified engine.

(2) What is EPA’s proposed approach to controlling Methane (CH4)?

CH4 (or methane) is greenhouse gas with a GWP of 23. It accounts for about 

0.03% of the greenhouse gases from heavy-duty trucks.107

EPA is proposing a standard that would cap CH4 emission levels, with the 

expectation that current heavy duty vehicles and engines meeting the heavy duty

emission standards would not increase their levels, and that it would ensure that 

emissions would be addressed if in the future there are increases in the use of natural gas 

or any other alternative fuel. EPA believes that current heavy duty emission standards, 

specifically the NMHC standards for both engine and chassis certified engines directly 

result in stringent CH4 control. It is believed that the current emission control 

technologies used to meet the stringent NMHC standards achieve the maximum feasible 

reductions and that no additional technologies are recognized that would result in 

additional CH4 reductions. The level of the standard would generally be achievable 

through normal emission control methods already required to meet heavy duty emission 

standards for hydrocarbons and EPA is therefore not attributing any cost to this part of 

today’s proposal. Since CH4 is produced in gasoline and diesel engines similar to other 

hydrocarbon components, controls targeted at reducing overall NMOG levels generally 

also work at reducing CH4 emissions. Therefore, for gasoline and diesel vehicles, the 

heavy duty hydrocarbon standards will generally prevent increases in CH4 emissions 

 

107 Value adapted from “Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2007. April 2009.
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levels from today. CH4 from heavy duty vehicles is relatively low compared to other 

GHGs largely due to the high effectiveness of the current heavy duty standards in 

controlling overall HC emissions. 

Since CH4 is produced in gasoline and diesel engines similar to other hydrocarbon 

components, CH4 emission levels are already low due to controls targeted at reducing 

overall NMHC levels. Therefore, for gasoline and diesel vehicles, the 2008 NMHC 

standards will generally prevent increases in CH4 emissions levels from today.

EPA believes that this level for the standard would be met by current gasoline and 

diesel trucks and vans, and would prevent increases in future CH4 emissions in the event 

that alternative fueled vehicles with high methane emissions, like some past dedicated 

compressed natural gas (CNG) vehicles, become a significant part of the vehicle fleet. 

Currently EPA does not have separate CH4 standards because, unlike other hydrocarbons, 

CH4 does not contribute significantly to ozone formation.108 However, CH4 emissions 

levels in the gasoline and diesel heavy duty truck fleet have nevertheless generally been 

controlled by the heavy duty hydrocarbon (HC) emission standards. Even so, without an 

emission standard for CH4, future emission levels of CH4 cannot be guaranteed to remain 

at current levels as vehicle technologies and fuels evolve.

In recent model years, a small number of heavy duty trucks and engines were sold 

that were designed for dedicated use of compressed natural gas (CNG). While emission 

control designs on these recent dedicated CNG-fueled vehicles demonstrate CH4 control 

as effective as gasoline or diesel equivalent vehicles, CNG-fueled vehicles have 

historically produced significantly higher CH4 emissions than gasoline or diesel vehicles. 

This is because their CNG fuel is essentially methane, and any unburned fuel that escapes 

combustion and is not oxidized by the catalyst is emitted as methane. However, even if 

these vehicles meet the heavy duty hydrocarbon standard and appear to have effective 

CH4 control by nature of the hydrocarbon controls, heavy duty standards do not require 

CH4 control. While the proposed CH4 cap standard should not require any different 

emission control designs (i.e., feedback controlled 3-way catalyst) beyond what is already 

required to meet heavy duty hydrocarbon standards on a dedicated CNG vehicle, the cap 

will ensure that systems maintain the current level of CH4 control. We are not proposing 

more stringent CH4 standards because we believe that the same controls that are used to 

meet current heavy duty hydrocarbon standards should result in effective CH4 control. 

Since CH4 is already measured under the current heavy duty emissions regulations (so 

that it may be subtracted to calculate non-methane hydrocarbons), the proposed standard 

would not result in additional testing costs. EPA requests comment on whether the 

proposed cap standard would result in any significant technological challenges for 

makers of CNG vehicles.

 

108 But see Ford Motor Co. v. EPA, 604 F. 2d 685 (D.C. Cir. 1979) (permissible for EPA to regulate CH4 

under CAA section 202 (b)).
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(a) Heavy-duty Pickup Truck and Van CH4 Standard

EPA is proposing a CH4 emission standard of 0. 05 g/mi as measured on the 

combined cycle FTP, to apply beginning with model year 2014 for HD pickups and vans 

subject to the proposed CO2 standards. Similar to the CO2 standard approach, the CH4

emission level of a vehicle would be a composite of the FTP city and highway cycles 

with the same 55% city weighting and 45% highway weighting. 

The level of the proposed standard is approximately two times the average heavy 

duty gasoline and diesel truck and van levels.109 As with N2O, this proposed level 

recognizes that manufacturers typically set emissions design targets with a compliance 

margin of approximately 50% of the standard. Thus, we believe that the proposed 

standard should be met by current gasoline vehicles with no increase from today’s CH4

levels. Similarly, since current diesel vehicles generally have even lower CH4 emissions 

than gasoline vehicles, we believe that diesels would also meet the proposed standard 

with a larger compliance margin resulting in no change in today’s CH4 levels. 

(b) Heavy Duty Engine Methane (CH4) Exhaust Emission Standard

EPA is proposing a heavy duty engine CH4 emission standard of 0.02 g/hp-hr as 

measured on the heavy duty engine FTP, to apply beginning in model year 2014. The 

proposed standard would cap CH4 emissions at a level currently achieved by diesel and 

gasoline heavy duty engines. The level of the standard would generally be achievable 

through normal emission control methods already required to meet 2007 emission 

standards for NMHC110 and EPA is therefore not attributing any cost to this part of this 

proposal. 

The level of the proposed CH4 standard is twice the average CH4 emissions from 

the four diesel engines in the ACES study.

111

 As with N2O, this proposed level 

recognizes that manufacturers typically set emission design targets at about 50% of the 

standard. Thus, EPA believes the proposed standard would be met by current diesel and 

gasoline engines with little if any technological improvements. The agency believes a 

more stringent CH4 standard would not be timely, since, as discussed above for N2O, 

EPA believes that the challenge of complying with the CO2 standards should be the 

primary focus of the manufacturers

CH4 is measured under the current 2007 regulations so that it may be subtracted to 

calculate non-methane hydrocarbons. Therefore EPA expects that the proposed standard 

would not result in additional testing costs. 

 

109 Need to get this number from MOVES and test data.

110 40 CFR § 86.007-11

111 CRC Report: ACES Phase 1 of the Advanced Collaborative Emissions Study, 2009.
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EPA is not proposing any vehicle-level CH4 standards for heavy duty trucks 

(combination or vocational) in this proposal. The CH4 emissions would be controlled 

through the heavy duty engine portion of the program. The only requirement of these 

truck manufacturers to comply with the CH4 requirements is to install a certified engine.

(3) Alternative CO2 Equivalent Standard

In lieu of complying with the separate N2O and CH4 cap standards, EPA is 

proposing that a manufacturer could choose to comply with a single CO2-equivalent 

standard. Under this option, a manufacturer would convert its N2O and CH4 test results 

into CO2-equivalent values and add this sum to its CO2 emissions. This CO2-equivalent 

value as well as straight CO2 value would both still need to comply with the applicable 

CO2 standard. In other words, a manufacturer could offset any N2O emissions or any 

CH4 emissions by taking steps to further reduce CO2. A manufacturer choosing this 

option for an engine would need to apply this approach to all of the engines in that engine 

family. If a manufacturer chose this option, the result would be more environmentally

protective overall than the cap standard approach, since the manufacturer would need to 

reduce its CO2 emissions to offset any N2O or CH4 levels, but would not be allowed to 

increase CO2 above the standard by reducing N2O or CH4.

EPA proposes that the compliance level for the optional CO2-equivalent approach 

be calculated using the Global Warming Potential of each GHG, such that the CO2-

equivalent equals CO2 + (298 x N2O) + (25 x CH4). The N2O and CH4 values would be 

the measured emission values for these GHGs. Finally, for manufacturers using this 

option, the CO2-equivalent emission level would also become the basis for any engine 

emission debits or credits that the manufacturer might generate.

The proposed NHTSA fuel consumption program will not use CO2-equivalent, as 

suggested above. Measured performance to the NHTSA fuel consumption standards will 

be based on the measurement of CO2 with no adjustment for N2O and/or CH4. For 

manufacturers that use the EPA alternative and a CO2-equivalent performance value, 

compliance to the EPA CO2 standard will not be directly equivalent to compliance to the 

NHTSA fuel consumption standard.

(4) EPA’s proposed standards for direct emissions from air conditioning

Air conditioning (A/C) systems contribute to GHG emissions in two ways – direct 

emissions through refrigerant leakage and indirect exhaust emissions due to the extra load 

on the vehicle’s engine to provide power to the air conditioning system. 

Hydrofluorocarbon (HFC) refrigerants, which are powerful GHG pollutants, can leak 

from the A/C system. This includes the direct leakage of refrigerant as well as the 

subsequent leakage associate with maintenance and servicing, and with disposal at the 

end of the vehicle’s life. The most commonly used refrigerant in automotive applications
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– R134a, has a high global warming potential (GWP) of 1430. 112 Due to the high GWP 

of R134a, a small leakage of the refrigerant has a much greater global warming impact 

than a similar amount of emissions of CO2 or other mobile source GHGs. 

Heavy duty air conditioning systems today are similar to those used in light-duty

applications. However, differences may exist in terms of cooling capacity (such that 

sleeper cabs have larger cabin volumes than day cabs), system layout (such as the number 

of evaporators), and the durability requirements due to longer truck life. However, the 

component technologies and costs to reduce direct HFC emissions are similar between 

the two types of vehicles. 

The quantity of GHG emissions from heavy duty trucks relative to the CO2

emissions from driving the vehicle and moving freight is very small. Therefore, a credit 

approach is not appropriate for this segment of vehicles because the value of the credit is 

too small to provide sufficient incentive to utilize feasible and cost-effective air 

conditioning leakage improvements. For the same reason, including air conditioning 

leakage improvements within the main standard would in many instances result in lost 

control opportunities. Therefore, EPA is proposing that truck manufacturers be required

to meet a low leakage requirement for all air conditioning systems installed in 2014 

model year and later trucks, with one exception. The agency is not proposing leakage 

standards for Class 2b-8 Vocational Vehicles at this time due to the complexity in the 

build process and the potential for different entities besides the chassis manufacturer to 

be involved in the air conditioning system production and installation, with consequent 

difficulties in developing a regulatory system. 

EPA is proposing a leakage standard which is a “percent refrigerant leakage per 

year” to assure that high-quality, low-leakage components are used in each air 

conditioning system design. The agency believes that a single “gram of refrigerant 

leakage per year” would not fairly address the variety of air conditioning system designs 

and layouts found in the heavy duty truck sector. EPA is proposing a standard of 1.50 

percent leakage per year for Heavy Duty Pickup Trucks and Vans and Class 7/8 Tractors. 

The proposed standard was derived from the vehicles with the largest system refrigerant 

capacity based on the Minnesota GHG Reporting database.113 The average percent 

leakage per year of the 2010 model year vehicles is 2.7 percent. This proposed level of 

reduction is roughly comparable to that necessary to generate credits under the light-duty 

vehicle program. See 75 FR at 25426-247. Since refrigerant leakage past the compressor 

shaft seal is the dominant source of leakage in belt-driven air conditioning systems, the 

 

112 The global warming potentials (GWP) used in the NPRM analysis are consistent with Intergovernmental 

Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). At this time, the IPCC Second 

Assessment Report (SAR) global warming potential values have been agreed upon as the official U.S. 

framework for addressing climate change. The IPCC SAR GWP values are used in the official U.S. 

greenhouse gas inventory submission to the climate change framework. When inventories are recalculated 

for the final rule, changes in GWP used may lead to adjustments. 

113 The Minnesota refrigerant leakage data can be found at 

http://www.pca.state.mn.us/climatechange/mobileair.html#leakdata.
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agency is seeking comment on whether the stringency of a single “percent refrigerant 

leakage per year” standard fairly addresses the range of system refrigerant capacities 

likely to be used in heavy duty trucks.114 Since systems with less refrigerant may have a 

larger percentage of their annual leakage from the compressor shaft seal than systems 

with more refrigerant capacity, their relative percent refrigerant leakage per year could be 

higher, and a more extensive application of leakage reducing technologies could be 

needed to meet the standard). EPA welcomes comments relative to the stringency of the 

standard.

Manufacturers can choose to reduce A/C leakage emissions in two ways. First, 

they can utilize leak-tight components. Second, manufacturers can largely eliminate the 

global warming impact of leakage emissions by adopting systems that use an alternative, 

low-GWP refrigerant. EPA believes that reducing A/C system leakage is both highly

cost-effective and technologically feasible. The availability of low leakage components 

is being driven by the air conditioning program in the light-duty GHG rule which apply 

to 2012 model year and later vehicles. The cooperative industry and government 

Improved Mobile Air Conditioning (IMAC) program has demonstrated that new-vehicle

leakage emissions can be reduced by 50% by reducing the number and improving the 

quality of the components, fittings, seals, and hoses of the A/C system.115 All of these 

technologies are already in commercial use and exist on some of today’s systems, and 

EPA does not anticipate any significant improvements in sealing technologies for model 

years beyond 2014. However, EPA does anticipate that updates to the SAE J2727 

standard will be forthcoming (to address new materials and components which perform 

better than those originally used in the SAE analysis), and that it will be appropriate to 

include these updates in the regulations concerning refrigerant leakage. 

Consistent with the 2012-2016 light-duty GHG rule, we are estimating costs for 

leakage control at $18 (2008$) in direct manufacturing costs. Including a low complexity

ICM of 1.14 results in costs of $21 in the 2014 model year. Time based learning is 

considered appropriate for A/C leakage control, so costs in the 2017 model year would be 

$19. These costs are applied to all heavy duty pickups and vans, and to all combination 

tractors.

EPA proposes that manufacturers demonstrate improvements in their A/C system 

designs and components through a design-based method. The proposed method for 

calculating A/C leakage is based closely on an industry-consensus leakage scoring 

method, described below. This leakage scoring method is correlated to experimentallymeasured leakage rates from a number of vehicles using the different available A/C 

components. Under the proposed approach, manufacturers would choose from a menu of 

A/C equipment and components used in their vehicles in order to establish leakage 

scores, which would characterize their A/C system leakage performance and calculate the 

percent leakage per year as this score divided by the system refrigerant capacity. 

 

114 Society of Automotive Engineers Surface Vehicle Standard J2727, issued August 2008, 

http://www.sae.org

115 Team 1-Refrigerant Leakage Reduction: Final Report to Sponsors, SAE, 2007.
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Consistent with the light-duty GHG rule, EPA is proposing that a manufacturer 

would compare the components of its A/C system with a set of leakage-reduction 

technologies and actions that is based closely on that being developed through IMAC and 

the Society of Automotive Engineers (as SAE Surface Vehicle Standard J2727, August 

2008 version). See generally 75 FR at 25426. The J2727 approach was developed from 

laboratory testing of a variety of A/C related components, and EPA believes that the 

J2727 leakage scoring system generally represents a reasonable correlation with average 

real-world leakage in new vehicles. Like the IMAC approach, our proposed approach 

would associate each component with a specific leakage rate in grams per year identical 

to the values in J2727 and then sum together the component leakage values to develop 

the total A/C system leakage. However, in the heavy duty truck program, the total A/C 

leakage score would then be divided by the value by the total refrigerant system capacity 

to develop a percent leakage per year.

EPA believes that the design-based approach would result in estimates of likely

leakage emissions reductions that would be comparable to those that would eventually 

result from performance-based testing. At the same time, comments are encouraged on 

all developments that may lead to a robust, practical, performance-based test for 

measuring A/C refrigerant leakage emissions.

CO2 emissions are also associated with air conditioner efficiency, since air 

conditioners create load on the engine. See 74 FR at 49529. However, EPA is not 

proposing to set air conditioning efficiency standards for vocational and combination 

trucks. The CO2 emissions due to air conditioning systems in these heavy duty trucks are 

minimal compared to their overall emissions of CO2. For example, EPA conducted 

modeling of a Class 8 sleeper cab using [TEST] to evaluate the impact of air conditioning 

and found that it leads to approximately 1 gram of CO2/ton- mile. Therefore, a projected 

24% improvement of the air conditioning system (the level projected in the light-duty

GHG rulemaking), would only reduce CO2 emissions by less than 0.3 g CO2/ton-mile, or 

approximately 0.3 percent of the baseline Class 8 sleeper cab CO2 emissions.

EPA is not specifying a specific in-use standard for leakage, as neither test 

procedures nor facilities exist to measure refrigerant leakage from a vehicle’s air 

conditioning system. However, consistent with the light-duty GHG rule, where we 

require that manufacturers attest to the durability of components and systems used to 

meet the CO2 standards (see 75 FR at 25689), we will require that manufacturers of 

heavy-duty vehicles attest to the durability of these systems, and provide an engineering 

analysis which demonstrates component and system durability. 

(5) EPA’s proposed credits for indirect emissions from air conditioning

As described above, in addition to direct emissions from refrigerant leakage, air 

conditioning systems also create indirect exhaust emissions due to the extra load on the 

vehicle’s engine to provide power to the air conditioning system. These indirect 

emissions are in the form of the additional CO2 emitted from the engine when A/C is 

being used due to the added loads. Unlike direct emissions which tend to be a set annual 

leak rate not directly tied to usage, indirect emissions are fully a function of A/C usage. 
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Due to the complexity of the heavy duty market, it is difficult to estimate with any 

degree of precision what the actual impact of indirect emissions are across the vastly

different applications and duty cycles of heavy duty trucks. Depending on application, 

geographic location and even seasonal usage relationships, A/C systems usage will vary 

differently across the heavy duty fleet and therefore efficiency improvements will also 

result in different indirect emission reductions . For this reason, EPA is not proposing an 

indirect emission standard like we have proposed for direct emissions in heavy duty 

vehicles.

Instead, EPA is seeking comment on the applicability of an indirect emissions 

credit for A/C system efficiency improvements specifically in the heavy duty pickup 

trucks and vans (i.e., 2b/3). These vehicles are most closely related to their light duty

counterparts that have an indirect emissions credit program established under the light 

duty GHG rule. It is likely that the light duty and heavy duty vehicles can share 

components used to improve the A/C system efficiency and reduce indirect emissions. 

EPA also seeks comment on the level of the credit and if the fleet CO2 target standards 

should be adjusted accordingly to reflect expected A/C efficiency improvements similar 

to approach used in the light duty rule, 

III. Feasibility Assessments and Conclusions

In this section, NHTSA and EPA discuss several aspects of our joint technical 

analyses. These analyses are common to the development of each agency’s proposed

standards. Specifically we discuss: the development of the baseline used by each agency

for assessing costs, benefits, and other impacts of the standards, the technologies the 

agencies evaluated and their costs and effectiveness, and the development of the 

proposed standards based on application of technology in light of the attribute based 

distinctions and related compliance measurement procedures. We also discuss 

consideration of standards that are either more or less stringent than those proposed. 

This proposal is based on the need to obtain significant oil savings and GHG 

emissions reductions from the transportation sector, and the recognition that there are 

appropriate and cost-effective technologies to achieve such reductions feasibly. The 

decision on what standard to set is guided by each agency’s statutory requirements, and is 

largely based on the need for reductions, the effectiveness of the emissions control 

technology, the cost and other impacts of implementing the technology, and the lead time 

needed for manufacturers to employ the control technology. The availability of 

technology to achieve reductions and the cost and other aspects of this technology are 

therefore a central focus of this proposed rulemaking.

Here, the focus of the standards is on applying fuel efficiency and emissions 

control technology to reduce fuel consumption, CO2 and other greenhouse gases. 

Vehicles combust fuel to generate power that is used to perform two basic functions: 1) 

transport the truck and its payload, and 2) operate various accessories during the 

operation of the truck such as the power take-off units. Engine-based technology can 

reduce fuel consumption and CO2 emissions by improving engine efficiency, which 

increases the amount of power produced per unit of fuel consumed. Vehicle-based 
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technology can reduce fuel consumption and CO2 emissions by increasing the vehicle 

efficiency, which reduces the amount of power demanded from the engine to perform the 

truck’s primary functions.

Our technical work has therefore focused on both engine efficiency improvements 

and vehicle efficiency improvements. In addition to fuel delivery, combustion, and 

aftertreatment technology, any aspect of the truck that affects the need for the engine to 

produce power must also be considered. For example, the drag due to aerodynamics and 

the resistance of the tires to rolling both have major impacts on the amount of power 

demanded of the engine while operating the vehicle. 

The large number of possible technologies to consider and the breadth of vehicle 

systems that are affected mean that consideration of the manufacturer’s design and 

production process plays a major role in developing the proposed standards. Engine and 

vehicle manufacturers typically develop many different models based on a limited 

number of platforms. The platform typically consists of a common engine or truck model 

architecture. For example, a common engine platform may contain the same 

configuration (such as inline), number of cylinders, valvetrain architecture (such as 

overhead valve), cylinder head design, piston design, among other attributes. An engine 

platform may have different calibrations (such as different power ratings) and different 

aftertreatment control strategies (such as EGR or SCR). On the other hand, a common 

vehicle platform has different meanings depending on the market. In the heavy duty 

pickup truck market, each truck manufacturer usually has only a single pickup truck 

platform (for example the F series by Ford) with common chassis designs and shared 

body panels, but with variations on load capacity of the axles, the cab configuration, tire 

offerings, and powertrain options. Lastly, the combination tractor market has several 

different platforms and the trucks within each platform (such as LoneStar by Navistar) 

have less commonality. Tractor manufacturers will offer several different options for 

bumpers, mirrors, aerodynamic fairing, wheels, and tires, among others. However, some 

areas such as the overall basic aerodynamic design (such as the grill, hood, windshield, 

and doors) of the tractor are tied to tractor platform.

The platform approach allows for efficient use of design and manufacturing 

resources. Given the very large investment put into designing and producing each truck 

model, manufacturers of heavy-duty pickup trucks and vans typically plan on a major 

redesign for the models every 5 years or more. Recently, EPA’s non-GHG heavy duty 

engine program provided new emissions standards every three model years. Heavy duty 

engine and truck manufacturer product plans typically have fallen into three year cycles 

to reflect this environment. While the recent non-GHG emissions standards can be 

handled generally with redesigns of engines and trucks, a complete redesign of a new 

heavy-duty engine or truck typically occurs on a slower cycle and often does not align in 

time due to the fact that the manufacturer of engines differs from the truck manufacturer. 

At the redesign stage, the manufacturer will upgrade or add all of the technology and 

make most other changes supporting the manufacturer’s plans for the next several years, 

including plans related to emissions, fuel economy, and safety regulations.
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A redesign of either engines or truck platforms often involves a package of 

changes designed to work together to meet the various requirements and plans for the 

model for several model years after the redesign. This often involves significant 

engineering, development, manufacturing, and marketing resources to create a new 

product with multiple new features. In order to leverage this significant upfront 

investment, manufacturers plan vehicle redesigns with several model years of production 

in mind. Vehicle models are not completely static between redesigns as limited changes 

are often incorporated for each model year. This interim process is called a refresh of the 

vehicle and it generally does not allow for major technology changes although more 

minor ones can be done (e.g., small aerodynamic improvements, etc). More major 

technology upgrades that affect multiple systems of the vehicle thus occur at the vehicle 

redesign stage and not in the time period between redesigns.

As discussed below, there are a wide variety of CO2 and fuel consumption 

reducing technologies involving several different systems in the engine and vehicle that 

are available for consideration. Many can involve major changes to the engine or 

vehicle, such as changes to the engine block and cylinder heads or changes in vehicle 

shape to improve aerodynamic efficiency. Incorporation of such technologies during the 

periodic engine, transmission or vehicle redesign process would allow manufacturers to 

develop appropriate packages of technology upgrades that combine technologies in ways 

that work together and fit with the overall goals of the redesign. By synchronizing with 

their multi-year planning process, manufacturers can avoid the large increase in resources 

and costs that would occur if technology had to be added outside of the redesign process. 

We considered redesign cycles both in our costing and in assessing the lead time 

required.

As described below, the vast majority of technology required by this proposal is 

commercially available and already being employed to a limited extent across the fleet. 

Therefore the majority of the emission and fuel consumption reductions which would 

result from these proposed rules would result from the increased use of these 

technologies. EPA and NHTSA also believe that these proposed rules would encourage 

the development and limited use of more advanced technologies, such as advanced 

aerodynamics and hybrid powertrains in some vocational truck applications. 

In evaluating truck efficiency, NHTSA and EPA have excluded fundamental 

changes in the engine or trucks’ performance. For example, the agencies did not consider 

approaches that would require reductions in engine power or otherwise limit truck 

performance. The agencies have limited the assessment of technical feasibility and 

resultant vehicle cost to technologies which maintain freight utility. 

The agencies worked together to determine component costs for each of the 

technologies and build up the costs accordingly. For costs, the agencies considered both 

the direct or ‘‘piece’’ costs and indirect costs of individual components of technologies. 

For the direct costs, the agencies followed a bill of materials (BOM) approach utilized by

the agencies in the light-duty fuel economy and GHG final rule. A bill of materials, in a 

general sense, is a list of components or sub-systems that make up a system— in this 

case, an item of technology which reduces GHG emissions and fuel consumption. In 
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order to determine what a system costs, one of the first steps is to determine its 

components and what they cost. NHTSA and EPA estimated these components and their 

costs based on a number of sources for cost-related information. In general, the direct 

costs of fuel consumption-improving technologies for heavy-duty pickups and vans are 

consistent with those used in the 2012-2016 light-duty rule, except that the agencies have 

scaled up certain costs where appropriate to accommodate the larger size and/or loads 

placed on parts and systems in the heavy-duty classes relative to the light-duty classes. 

For loose heavy-duty engines, the agencies have consulted various studies and have 

exercised engineering judgment when estimating direct costs. For technologies expected 

to be added to vocational and combination trucks, the agencies have again consulted 

various studies and have used engineering judgment to arrive at direct cost estimates. 

Once costs were determined, they were adjusted to ensure that they were all expressed in 

2008 dollars using a ratio of GDP deflators for the associated calendar years. 

Indirect costs were accounted for using the ICM (indirect cost multiplier) 

approach explained in Chapter 2 of the DRIA, rather than using the traditional Retail 

Price Equivalent (RPE) multiplier approach. For the heavy duty pickup truck and van 

cost projections in this proposal, the agencies have used ICMs developed for light-duty 

vehicles (with the exception that here return on capital has been incorporated into the 

ICMs, where it had not been in the light-duty rule) primarily because the manufacturers 

involved in this segment of the heavy duty market are the same manufacturers that build 

light duty trucks. For the Class 7/8 tractor, vocational truck, and heavy duty engine cost 

projections in this proposal, EPA contracted with RTI International to update EPA’s 

methodology for accounting for indirect costs associated with changes in direct 

manufacturing costs for heavy duty engine and truck manufacturers.116 In addition to the 

indirect cost multipliers varying by complexity and time frame, there is no reason to 

expect that the multipliers would be the same for engine manufacturers as for truck 

manufacturers. The report from RTI provides a description of the methodology, as well 

as calculations of new indirect cost multipliers. The multipliers used here include a 

factor of 5% of direct costs representing the return on capital for heavy duty engines and 

truck manufacturers. These indirect cost multipliers are intended to be used, along with 

calculations of direct manufacturing costs, to provide improved estimates of the full 

additional costs associated with new technologies. 

Details of the direct and indirect costs, and all applicable ICMs, are presented in 

Section VIII of this preamble and Chapter 2 of the draft DRIA. In addition, for details on 

the ICMs, please refer to the RTI report that has been placed in the docket. The agencies 

request comment on all aspects of the cost analysis, including the adjustment factors used 

in the RTI analysis -- the levels associated with R&D, warranty, etc. -- and whether those 

are appropriate or should be revised. If commenters suggest revisions, the agencies 

request supporting arguments and/or documentation. 

 

116 RTI International. Heavy Duty Truck Retail Price Equivalent and Indirect Cost Multipliers. July 2010.
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EPA and NHTSA believe that the emissions reductions called for by the proposed 

standards are technologically feasible at reasonable costs, reflecting our projections of 

widespread use of commercially available technology. Manufacturers may also find 

additional means to reduce emissions and lower fuel consumption beyond the technical 

approaches we describe here. We encourage such innovation through provisions in our 

flexibility program as discussed in Section IV.

The remainder of this section describes the technical feasibility and cost analysis 

in greater detail. Further detail on all of these issues can be found in the joint DRIA 

Chapter 2.

A. Class 7-8 Combination Tractors

Class 7 and 8 tractors are used in combination with trailers to transport freight. 

The variation in the design of these tractors and their typical uses drive different 

technology solutions for each regulatory class.

EPA and NHTSA collected information on the cost and effectiveness of fuel 

consumption and CO2 emission reducing technologies from several sources. The primary 

sources of information were the recent National Academy of Sciences report of 

Technologies and Approaches to Reducing the Fuel Consumption of Medium- and 

Heavy-Duty Vehicles (NAS)117, TIAX’s assessment of technologies to support the NAS 

panel report (TIAX)118, EPA’s Heavy-duty Lumped Parameter Model119, the analysis 

conducted by NESCCAF, ICCT, Southwest Research Institute and TIAX for reducing 

fuel consumption of heavy-duty long haul combination trucks (NESCCAF/ICCT)120, and 

the technology cost analysis conducted by ICF for EPA (ICF).121 Following on the 

Energy Independence and Security Act of 2007, the National Research Council appointed 

a NAS committee to assess technologies for improving fuel efficiency of heavy-duty

vehicles to support NHTSA’s rulemaking. The NAS report assessed current and future 

technologies for reducing fuel consumption, how the technologies could be implemented, 

and identified the potential cost of such technologies. The NAS panel contracted TIAX 

to perform an assessment of technologies and their associated capital costs which provide 

potential fuel consumption reductions in heavy-duty trucks and engines. Similar to the 

Lumped Parameter model which EPA developed to assess the impact and interactions of 

GHG and fuel consumption reducing technologies for light-duty vehicles, EPA 

developed a new version to specifically address the effectiveness and interactions of the 

proposed pickup truck and light heavy-duty engine technologies. The NESCAFF/ICCT 

 

117 National Academy of Science. Technologies and Approaches to Reducing the Fuel Consumption of 

Medium- and Heavy-Duty Vehicles. March 31, 2010.

118 TIAX, LLC. Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles. 

November 2009.

119 U.S. EPA. Heavy-duty Lumped Parameter Model. NEED DOCKET #.

120 NESCCAF, ICCT, Southwest Research Institute, and TIAX. Reducing Heavy-Duty Long Haul 

Combination Truck Fuel Consumption and CO2 Emissions. October 2009.

121 ICF International. Investigation of Costs for Strategies to Reduce Greenhouse Gas Emissions for 

Heavy-Duty On-Road Vehicles. June 2010. 
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study assessed technologies available in the 2012 through 2017 to reduce CO2 emissions 

and fuel consumption of line haul combination tractors and trailers. Lastly, the ICF 

report focused on the capital, maintenance, and operating costs of technologies currently 

available to reduce CO2 emissions and fuel consumption in heavy-duty engines, 

combination tractors, and vocational vehicles.

(1) What technologies did the agencies consider to reduce the CO2 emissions 

and fuel consumption of tractors?

Manufacturers can reduce CO2 emissions and fuel consumption of combination 

tractors through engine, aerodynamic, tire, extended idle, and weight reduction 

technologies. The agencies note that SmartWay trucks are available today which 

incorporate the technologies that the agencies are considering as the basis for the 

standards in this proposal. . The standards are premised on use of these technologies. 

We will also discuss other technologies that could potentially be used, such as vehicle 

speed limiters, although we are not basing the proposed standards on their use for the 

model years covered by this proposal, for various reasons discussed below. 

In this section we discuss the baseline tractor and engine technologies for the 

2010 model year, and then discuss the kinds of technologies that could be used to 

improve performance relative to this baseline.

(a) Baseline Tractor & Tractor Technologies

Baseline tractor: The agencies developed the baseline tractor to represent the 

average 2010 model year tractor. Today there is a large spread in aerodynamics in the 

new tractor fleet. Trucks sold may reflect classic styling, or may be sold with 

conventional or SmartWay aerodynamic packages. Based on our review of current truck 

model configurations and Polk data provided through MJ Bradley,

122 we believe the 

baseline new truck fleet aerodynamics represent approximately 25 percent classic, 70 

percent conventional, and 5 percent SmartWay. The baseline Class 7/8 day cab tractor 

consists of an aerodynamic package which closely resembles the “conventional” package 

described in Section II, baseline tire rolling resistance of 7.8 kg/metric ton for the steer 

tire and 8.2 kg/ metric ton, dual tires with steel wheels on the drive axles, and no vehicle 

speed limiter. The baseline tractor for the Class 8 sleeper cabs contains the same 

aerodynamic and tire rolling resistance technologies as the baseline day cab, does not 

include vehicle speed limiters, and does not include an idle reduction technology. The 

agencies assume the baseline transmission is a 10 speed manual.

Aerodynamic technologies: There are opportunities to reduce aerodynamic drag 

from the tractor, but it is difficult to assess the benefit of individual aerodynamic features. 

Therefore, it requires optimizing it as a system. The potential areas to reduce drag 

include all sides of the truck – front, sides, top, rear and bottom. The grill, bumper, and 

hood can be designed to minimize the pressure created by the front of the truck. 

 

122 MJ Bradley. Heavy Duty Market Analysis. May 2009. Page 10.
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Technologies such as aerodynamic mirrors and fuel tank fairings can reduce the surface 

area perpendicular to the wind and provide a smooth surface to minimize disruptions of 

the air flow. Roof fairings provide a transition to move the air smoothly over the tractor 

and trailer. Side extenders can minimize the air entrapped in the gap between the tractor 

and trailer. Lastly, underbelly treatments can manage the flow of air underneath the 

tractor. As discussed in the TIAX report, the coefficient of drag (Cd) of a SmartWay

sleeper cab high roof tractor is approximately 0.60, which is a significant improvement 

over a truck with no aerodynamic features which has a Cd value of approximately 0.80. 

The [TEST] model demonstrates that an aerodynamic improvement of a Class 8 high roof 

sleeper cab with a Cd value from 0.60 (which represents a SmartWay tractor) provides a 

5% reduction in fuel consumption and CO2 emissions over a truck with a Cd of 0.68.

Lower Rolling Resistance Tires: A tire’s rolling resistance results from the tread 

compound material, the architecture and materials of the casing, tread design, the tire 

manufacturing process, and its operating conditions (surface, inflation pressure, speed, 

temperature, etc.). Differences in rolling resistance of up to 50% have been identified for 

tires designed to equip the same vehicle. The baseline rolling resistance coefficient for 

today’s fleet is 7.8 kg/metric ton for the steer tire and 8.2 kg/metric ton for the drive tire, 

based on sales weighting of the top three manufacturers based on market share. Since 

2007 SmartWay has steer tires with rolling resistance coefficients of less than 6.6 

kg/metric ton for the steer tire and less than 7.0 kg/metric ton for the drive tire. Low 

rolling resistance drive tires are currently offered in both dual assembly and single widebase configurations. Single wide tires can offer both the rolling resistance reduction 

along with improved aerodynamics and weight reduction. The [TEST] model 

demonstrates that replacing baseline tractor tires with tires which meet the SmartWay

level provides a 4% reduction in fuel consumption and CO2 emissions over the prescribed 

test cycle.

Weight Reduction: The agencies’ baseline tire and wheel package consists of 

dual tires with steel wheels. A tractor’s empty curb weight can be reduced from the 

replacement of dual tires with single wide tires and with the replacement of steel wheels 

with high strength steel or aluminum. Analysis of literature indicates that there is 

opportunity to reduce typical tractor curb weights by 80 to 670 pounds, or up to roughly 3 

percent, through the use of lighter weight wheels and single wide tires.123 High strength 

steel, aluminum, and light weight aluminum alloys provide opportunities to reduce the 

truck’s mass relative to steel wheels. In addition, single wide tires (a single wide-based 

tire which replaces two standard tires in each wheel position) provide the opportunity to 

reduce the overall mass of wheels and tires due to the replacement of dual tires with 

singles. On average, these technologies together can reduce weight by over 400 pounds. 

A weight reduction of this magnitude applied to a truck which travels at 70,000 pounds 

will have a minimal impact on fuel consumption. However, for trucks which operate at 

the maximum GVWR which occurs approximately for one third of truck miles travelled, 

a reduced tare weight will allow for additional payload to be carried. The [TEST] model 

 

123 NEED CITATION
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demonstrates that a weight reduction of 400 pounds applied to the payload tons for one 

third of the trips provides a 0.3% reduction in fuel consumption and CO2 emissions over 

the prescribed test cycle.

Extended Idle Reduction: Auxiliary power units, fuel operated heaters, battery

supplied air conditioning, and thermal storage systems are among the technologies 

available today to reduce main engine extended idling from sleeper cabs. Each of these 

technologies reduces the baseline fuel consumption during idling from a truck without 

this equipment (the baseline) from approximately 0.8 gallons per hour (main engine 

idling fuel consumption rate) to approximately 0.2 gallons per hour for an APU. EPA 

and NHTSA agree with the NAS assessment of a 6 percent reduction in overall fuel 

consumption reduction. 

Vehicle Speed Limiters: Fuel consumption and GHG emissions increase 

proportional to the square of vehicle speed. Therefore, lowering vehicle speeds can 

significantly reduce fuel consumption and GHG emissions. A vehicle speed limiter, 

which limits the vehicle's maximum speed, is a simple technology that is utilized today

by some fleets (though the typical maximum speed setting is often higher than 65 mph). 

The [TEST] model shows that using a vehicle speed limiter set at 62 mph will provide a 

4% reduction in fuel consumption and CO2 emissions over the prescribed test cycles over 

a baseline vehicle without a VSL or one set above 65 mph.

Transmission: As discussed in the NAS report, automatic and automated manual 

transmissions may offer the ability to improve vehicle fuel consumption by optimizing 

gear selection compared to an average driver. However, as also noted in the report the 

improvement is very dependent on the driver of the truck, such that reductions ranged 

from 0 to 8 percent. Well-trained drivers would be expected to perform as well or even 

better than an automatic transmission since the driver can see the road ahead and 

anticipate a changing stoplight or other road condition that an automatic transmission can 

not anticipate. However, poorly-trained drivers that shift too frequently or not frequently 

enough to maintain optimum engine operating conditions could be expected to realize 

improved in-use fuel consumption by switching from a manual transmission to an 

automatic or automated manual transmission. While we believe there may be real 

benefits in reduced fuel consumption and GHG emissions through the application of 

automatic transmission technology, we are not proposing to reflect that potential 

improvement in our standard setting nor in our compliance model. We have taken this 

approach because we cannot say with confidence what level of performance 

improvement to expect. However, we welcome comments on this decision supported 

where possible with data. If a clear measure of performance improvement can be defined 

for the use of automatic transmission technologies, we will consider reflecting the 

technology in setting the stringency of the standards and in determining compliance with 

the standards.

Low Friction Transmission, Axle, and Wheel Bearing Lubricants: The NAS 

report assessed low friction lubricants for the drivetrain as a 1 percent improvement in 

fuel consumption based on fleet testing. The light-duty fuel economy and GHG final rule 

and the pickup truck portion of this program estimate that low friction lubricants can have 
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an effectiveness value between 0 and 1 percent compared to traditional lubricants. 

However, it is not clear if in many heavy duty applications these low friction lubricants 

could have competing requirements like component durability issues requiring specific 

lubricants with different properties than low friction. The agencies are interested in 

comments on whether low friction lubricants should be included in the technologies 

available in [TEST] to set the fuel consumption and CO2 emissions standards and how 

manufacturers could ensure the use of these lubricants for the full useful life of the truck.

Hybrid: Hybrid powertrain development in Class 7/8 tractors has been limited to 

a few manufacturer demonstration vehicles to date. One of the key benefit opportunities 

for fuel consumption reduction with hybrids is less fuel consumption when a vehicle is 

idling, which are already included as a separate technology in the agencies’ technology

assessment. NAS estimated that hybrid systems would cost approximately $25,000 per 

truck in the 2015 through 2020 timeframe and provide a potential fuel consumption 

reduction of 10 percent, of which 6 percent is idle reduction which can be achieved 

through other idle reduction technologies.124 The limited reduction potential outside of 

idle reduction for Class 8 sleeper cab tractors is due to the mostly highway operation and 

limited start-stop operation. Due to the high cost and limited benefit during the model 

years at issue in this proposal, the agencies are not including hybrids in assessing 

standard stringency (or as an input to [TEST]). However as discussed in Section IV, the 

agencies are providing incentives to encourage the introduction of advanced technologies 

including hybrid powertrains in appropriate applications.

Management: The NAS report noted many operational opportunities to reduce 

fuel consumption, such as driver training and route optimization. The agencies have 

included discussion of several of these strategies in the DRIA, but are not using these 

approaches or technologies in the standard setting process. The agencies are looking to 

other resources, such as EPA’s SmartWay Transport Partnership and regulations that 

could potentially be promulgated by the Federal Highway Administration and the Federal 

Motor Carrier Safety Administration, to continue to encourage the development and 

utilization of these approaches. 

(b) Baseline Engine & Engine Technologies

The baseline engine for the Class 8 tractors is a Heavy Heavy-Duty Diesel engine 

with 15 liters of displacement which produces 455 horsepower. The agencies are using a 

smaller baseline engine for the Class 7 tractors because of the lower combined weights of 

this class of vehicles require less power, thus the baseline is an 11L engine with 350 

horsepower. The agencies developed the baseline diesel engine as a 2010 model year 

engine with an aftertreatment system which meets EPA’s 0.2 grams of NOx/bhp-hr 

standard with a selective catalytic reduction (SCR) system along with EGR and meets the 

PM emissions standard with a diesel particulate filter (DPF) with active regeneration. 

The baseline engine is turbocharged with a variable geometry turbocharger. The 

 

124 See page 6-28 of NAS report.
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following discussion of technologies describes improvements over the 2010 model year 

baseline engine performance, unless otherwise noted. Further discussion of the baseline 

engine and its performance can be found in section III.A.2.6 below. 

Turbochargers: Improved efficiency of a turbocharger compressor or turbine 

could reduce fuel consumption by approximately 1 to 2 percent over variable geometry

turbochargers in the market today. The NAS report identified technologies such as 

higher pressure ratio radial compressors, axial compressors, and dual stage turbochargers 

as design paths to improve turbocharger efficiency.

Low Temperature Exhaust Gas Recirculation: Most medium- and heavy-duty

vehicle diesel engines sold in the U.S. market today use cooled EGR, in which part of the 

exhaust gas is routed through a cooler (rejecting energy to the engine coolant) before 

being returned to the engine intake manifold. EGR is a technology employed to reduce 

peak combustion temperatures and thus NOx. Low-temperature EGR uses a larger or 

secondary EGR cooler to achieve lower intake charge temperatures, which tend to further 

reduce NOx formation. If the NOx requirement is unchanged, low-temperature EGR can 

allow changes such as more advanced injection timing that will increase engine 

efficiency slightly more than 1 percent. Because low-temperature EGR reduces the 

engine’s exhaust temperature, it may not be compatible with exhaust energy recovery

systems such as turbocompound or a bottoming cycle.

Engine Friction Reduction: Reduced friction in bearings, valve trains, and the 

piston-to-liner interface will improve efficiency. Any friction reduction must be carefully

developed to avoid issues with durability or performance capability. Estimates of fuel 

consumption improvements due to reduced friction range from 0.5% to 1.5%.125

Selective catalytic reduction (SCR): This technology is common on 2010 the 

medium- and heavy-duty diesel engines used in Class 7/8 tractors. Because SCR is a 

highly effective NOx aftertreatment approach, it enables engines to be optimized to 

maximize fuel efficiency, rather than minimize engine-out NOx. 2010 SCR systems are 

estimated to result in improved engine efficiency of approximately 4 to 5 percent 

compared to a 2007 in-cylinder EGR-based emissions system and by an even greater 

percentage compared to 2010 in-cylinder approaches.126 As more effective lowtemperature catalysts are developed, the NOx conversion efficiency of the SCR system 

will increase. Next-generation SCR systems could then enable additional efficiency

improvements; alternatively, these advances could be used to maintain efficiency while 

down-sizing the aftertreatment. We estimate that continued optimization of the catalyst 

 

125 TIAX, Assessment of Fuel Economy Technologies for Medium- and Heavy- Duty Vehicles, Final 

Report, Nov. 19, 2009, pg 4-15

126 Stanton, D. “Advanced Diesel Engine Technology Development for High Efficiency, Clean 

Combustion.” Cummins, Inc. Annual Progress Report 2008 Vehicle Technologies Program: Advanced 

Combustion Engine Technologies, US Department of Energy. Pp 113-116. December 2008.
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could offer 1 to 2 percent additional reduction in fuel use over 2010 model year 

systems.127

Improved Combustion Process: Fuel consumption reductions in the range of 1 to 

3 percent over the baseline diesel engine are identified in the NAS report through 

improved combustion chamber design, higher fuel injection pressure, improved injection 

shaping and timing, and higher peak cylinder pressures.

Reduced Parasitic Loads: Accessories that are traditionally gear or belt driven by

a vehicle’s engine can be optimized and/or converted to electric power. Examples include 

the engine water pump, oil pump, fuel injection pump, air compressor, power-steering 

pump, cooling fans, and the vehicle’s air-conditioning system. Optimization and 

improved pressure regulation may significantly reduce the parasitic load of the water, air 

and fuel pumps. Electrification may result in a reduction in power demand, because 

electrically powered accessories (such as the air compressor or power steering) operate 

only when needed if they are electrically powered, but they impose a parasitic demand all 

the time if they are engine driven. In other cases, such as cooling fans or an engine’s 

water pump, electric power allows the accessory to run at speeds independent of engine 

speed, which can reduce power consumption. The TIAX [2009, pg. 3-5] study used 2 to 4 

percent fuel consumption improvement for accessory electrification, with the 

understanding that electrification of accessories will have more effect in short-haul/urban 

applications and less benefit in line-haul applications.

Mechanical Turbocompounding: Mechanical turbocompounding adds a low 

pressure power turbine to the exhaust stream in order to extract additional energy, which 

is then delivered to the crankshaft. Published information on the fuel consumption 

reduction from mechanical turbocompounding varies between 2.5 and 5 percent.128 Some 

of these differences may depend on the operating condition or duty cycle that was 

considered by the different researchers. The performance of a turbocompounding system 

tends to be highest at full load and much less or even zero at light load. 

Electric Turbocompounding: This approach is similar in concept to mechanical 

turbocompounding, except that the power turbine drives an electrical generator. The 

electricity produced can be used to power an electrical motor supplementing the engine 

output, to power electrified accessories, or to charge a hybrid system battery. None of 

these systems have been demonstrated commercially, but modeled results by industry and 

DOE have shown improvements of 3 to 5 percent.129

Bottoming Cycle: An engine with bottoming cycle uses exhaust or other heat 

energy from the engine to create power without the use of additional fuel. The sources of 

 

127 TIAX Assessment of Fuel Economy Technologies for Medium and Heavy-duty Vehicles, Report to 

National Academy of Sciences, Nov 19, 2009, pg. 4-9

128 NESCCAF/ICCT study (p. 54) and TIAX (2009, pp. 3-5)

129 K. G. Duleep of Energy and Environmental Analysis, R. Kruiswyk, 2008, pp. 212-214, 

NESCCAF/ICCT, 2009, p. 54
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energy include the exhaust, EGR, charge air, and coolant. The estimates for fuel 

consumption reduction range up to 10 percent as documented in the NAS report.

(2) Projected Technology Package Effectiveness and Cost

(a) Class 7/8 Combination Tractors

EPA and NHTSA project that CO2 emissions and fuel consumption reductions 

can be achieved through the increased application of aerodynamic technologies, low 

rolling resistance tires, weight reduction, extended idle reduction technologies, vehicle 

speed limiters, and engine improvements. As discussed above, the agencies believe that 

hybrid powertrains in tractors will not be cost-effective in the time frame of the rules. 

The agencies also are not proposing to include drivetrain technologies in the standard 

setting process, as discussed in Section II. 

The agencies evaluated each technology and estimated the most appropriate 

application rate of technology into each tractor regulatory class based on our 

understanding of the industry sectors into which the trucks would be applied. The next 

sections describe the effectiveness of the individual technologies, the costs of the 

technologies, the projected application rates of the technologies into the regulatory

classes, and finally the derivation of the proposed standards.

(i) Baseline Tractor Performance

The agencies developed the baseline tractor for each subcategory to represent an 

average 2010 model year tractor configured as noted earlier. The approach taken by the 

agencies was to define the individual inputs to [TEST]. For example, the agencies 

evaluated the industry’s tractor offerings and concluded that the average tractor contains

a generally aerodynamic shape (such as roof fairings) and avoids classic features such as 

exhaust stacks at the b-pillar which increase drag. The agencies consider a baseline truck 

as having “conventional” aerodynamic package, though today there is a large spread in 

aerodynamics in the new tractor fleet. As noted earlier, our assessment of the baseline 

new truck fleet aerodynamics represents approximately 25 percent classic, 65 percent 

conventional, and 10 percent SmartWay. This mix of vehicle aerodynamics provides a 

Cd performance level slightly greater than the “conventional aerodynamic package” Cd 

value (for example the baseline high roof tractor has a Cd of 0.69 while the same tractor 

category with a conventional aerodynamic package has a Cd of 0.68). The baseline 

rolling resistance coefficient for today’s fleet is 7.8 kg/metric ton for the steer tire and 8.2 

kg/metric ton for the drive tire, based on sales weighting of the top three manufacturers 

based on market share.130 

 

130 US Environmental Protection Agency. SmartWay Transport Partnership July 2010 e-update accessed 

July 16, 2010, from http://www.epa.gov/smartwaylogistics/newsroom/documents/e-update-july-10.pdf.
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Table III-1: Baseline Tractor Definitions

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low/Mid 

Roof

High Roof Low/Mid 

Roof

High Roof Low 

Roof

Mid 

Roof

High Roof

Aerodynamics (Cd)

Frontal Area 

(m2)

6.0 9.8 6.0 9.8 6.0 6.6 9.8

Baseline 0.81 0.69 0.81 0.69 0.81 0.76 0.69

Steer Tires (Crr kg/metric ton)

Baseline 7.8 7.8 7.8 7.8 7.8 7.8 7.8

Drive Tires (Crr kg/metric ton)

Baseline 8.2 8.2 8.2 8.2 8.2 8.2 8.2

Weight Reduction (lbs.)

Baseline 0 0 0 0 0 0 0

Extended Idle Reduction (gram CO2/ton-mile reduction)

Baseline N/A N/A N/A N/A 0 0 0

Vehicle Speed Limiter

Baseline -- -- -- -- -- -- --

Engine

Baseline 2010 MY 

11 L 

Engine

2010 MY 

11 L 

Engine

2010 MY 

15 L 

Engine

2010 MY 

15 L 

Engine

2010 MY 

15 L 

Engine

2010 MY 

15 L 

Engine

2010 MY 

15 L 

Engine

The agencies use the inputs described in Table III-1 in [TEST] to derive the 

baseline CO2 emissions and fuel consumption of Class 7/8 tractors. The results are 

included in Table III-2.

Table III-2: Class 7/8 Tractor Baseline CO2 Emissions and Fuel Consumption

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low Roof High Roof Low Roof High Roof Low Roof Mid Roof High Roof

CO2 (grams 

CO2/ton-mile)

115 135 86 98 76 77 89

Fuel 

Consumption 

(gal/1000 tonmile)

11.3 13.3 8.4 9.6 7.5 7.6 8.7

(ii) Tractor Technology Package Effectiveness

The agencies’ assessment of the proposed technology effectiveness was 

developed through the use of the [TEST] Model in coordination with chassis testing of 

three SmartWay certified Class 8 sleeper cabs. The agencies developed technology
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performance characteristics for each subcategory, described below. Each technology

consists of an input parameter which is in turn modeled in [TEST]. Table III-3 describes 

our proposed model inputs for the range of Class 7 and 8 tractor aerodynamic packages 

and vehicle technologies. This was combined with a projected technology application

rate to determine the stringency of the proposed standard. 

The aerodynamic packages are categorized as Classic, Conventional, SmartWay, 

Advanced SmartWay, and Advanced SmartWay II. The Classic aerodynamic package 

refers to traditional styling such as a flat front, exposed air cleaners and exhaust stacks, 

among others. The conventional package refers to an overall aerodynamic appearance 

and best represents the aerodynamics of the majority of new tractor sales. The SmartWay

aerodynamic package includes technologies such as roof fairings, aerodynamic hoods, 

aerodynamic mirrors, chassis fairings, and cab extenders. The Advanced SmartWay and 

Advanced SmartWay II packages reflect different degrees of new aerodynamic 

technology development such as active air management. A more complete description of 

these aerodynamic packages is included in Chapter 2 of the draft RIA. In general, the 

coefficient of drag values for each package and tractor subcategory were developed from 

EPA’s coast down testing of tractor-trailer combinations, the NAS report, and SAE 

papers. 

The rolling resistance coefficient for the tires was developed from SmartWay’s 

tire testing to develop the SmartWay certification. The benefits for the extended idle 

reductions were developed from literature, SmartWay work, and the NAS report. The 

weight reductions were developed from manufacturer information. 
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Table III-3 Class 7-8 Tractor Technology Values

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low 

Roof

High 

Roof

Low 

Roof

High 

Roof

Low 

Roof

Mid 

Roof

High 

Roof

Aerodynamics (Cd)

Frontal Area (m2) 6.0 9.8 6.0 9.8 6.0 6.6 9.8

Classic 0.85 0.75 0.85 0.75 0.85 0.80 0.75

Conventional 0.80 0.68 0.80 0.68 0.80 0.75 0.68

SmartWay 0.75 0.60 0.75 0.60 0.75 0.70 0.60

Advanced SmartWay 0.70 0.55 0.70 0.55 0.70 0.65 0.55

Advanced SmartWay 

II

0.65 0.50 0.65 0.50 0.65 0.60 0.50

Steer Tires (Crr kg/metric ton)

Baseline 7.8 7.8 7.8 7.8 7.8 7.8 7.8

SmartWay 6.6 6.6 6.6 6.6 6.6 6.6 6.6

Advanced SmartWay 5.7 5.7 5.7 5.7 5.7 5.7 5.7

Drive Tires (Crr kg/metric ton)

Baseline 8.2 8.2 8.2 8.2 8.2 8.2 8.2

SmartWay 7.0 7.0 7.0 7.0 7.0 7.0 7.0

Advanced SmartWay 6.0 6.0 6.0 6.0 6.0 6.0 6.0

Weight Reduction (lbs.)

Baseline 0 0 0 0 0 0 0

Control 400 400 400 400 400 400 400

Extended Idle Reduction (gram CO2/ton-mile reduction)

Baseline N/A N/A N/A N/A 0 0 0

Control N/A N/A N/A N/A 5 5 5

Vehicle Speed Limiter131

Baseline N/A N/A N/A N/A N/A N/A N/A

Control N/A N/A N/A N/A N/A N/A N/A

(iii) Tractor Technology Application Rates

Vehicle manufacturers often introduce major product changes together, as a 

package. In this manner the manufacturers can optimize their available resources, 

including engineering, development, manufacturing and marketing activities to create a 

product with multiple new features. In addition, manufacturers recognize that a truck 

design will need to remain competitive over the intended life of the design and meet 

future regulatory requirements. In some limited cases, manufacturers may implement an 

individual technology outside of a vehicle’s redesign cycle. In keeping with these 

 

131 Vehicle speed limiters are an applicable technology for all Class 7/8 tractors, however the standards are 

not premised on the use of this technology.
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industry practices, the agencies have created a set of vehicle technology packages for 

each regulatory class of Class 7/8 combination tractors.

With respect to the levels of technology application used to develop the proposed 

standards, NHTSA and EPA established technology application constraints. The first type 

of constraint was established based on the application of fuel consumption and CO2

emission reduction technologies into the different types of tractors. For example, idle 

reduction technologies are limited to Class 8 sleeper cabs using the assumption that day

cabs are not used for overnight hoteling. A second type of constraint was applied to most 

other technologies and limited their application based on factors reflecting the real world 

operating conditions that some combination tractors encounter. This second type of 

constraint was applied to the aerodynamic, tire, and vehicle speed limiter technologies. 

Table III-4 specifies the application rates that EPA and NHTSA used to develop the 

proposed standards.

The impact of aerodynamics on a truck’s efficiency increases with vehicle speed. 

Therefore, the usage pattern of the truck will determine the benefit of various 

aerodynamic technologies. Sleeper cabs are often used in line haul applications and drive 

the majority of their miles on the highway travelling at speeds greater than 55 mph. The 

industry has focused aerodynamic technology development, including SmartWay

tractors, on these types of trucks. Therefore the agencies are proposing the most 

aggressive aerodynamic technology application to this regulatory class. All of the major 

manufacturers today offer at least one SmartWay truck model. The NAS Report on 

heavy-duty truck found that manufacturers indicated that aerodynamic improvements 

which yield 3 to 4 percent fuel consumption reduction or 6 to 8 percent reduction in Cd 

values, beyond technologies used in today’s SmartWay trucks are achievable.132 EPA 

and NHTSA are proposing that the aerodynamic application rate for Class 8 sleeper cab 

high roof cabs to consist of 20 percent of Advanced SmartWay, 70 percent SmartWay, 

and 10 percent conventional reflecting our assessment of the fraction of tractors in this 

segment that can successfully apply these aerodynamic packages. The small percentage 

of conventional truck aerodynamics reflects applications including tractors serving as 

refuse haulers which spend a portion of their time off-road at the land fill and generally 

operate at lower speeds with frequent stops further reducing the benefit of aggressive 

aerodynamic technologies. Features such as chassis skirts are prone to damage in offroad applications; therefore we are not proposing to require that all trucks have chassis 

skirts or achieve GHG reductions premised on use of such technology. The 90 percent of 

tractors that we project can either be SmartWay or Advanced SmartWay equipped reflect 

the bulk of Class 8 high roof sleeper cab applications. We are not projecting a higher 

fraction of Advanced SmartWay aerodynamic systems because of the limited lead time 

for the program and the need for these more advanced technologies to be developed and 

demonstrated before being carried across a wider fraction of the fleet. Our averaging, 

banking and trading provisions provide manufacturers with the flexibility to implement 

 

132 TIAX. Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles. November 

2009. Page 4-40.
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these technologies over time even though the standard changes in a single step. We 

request comment on our assessment of the potential for use of Advanced SmartWay

technologies and the need for a fraction of these vehicles to continue to remain

configured as conventional cabs due to their occasional use off-road.

The proposed aerodynamic application for the other tractor regulatory categories 

is less aggressive than for the Class 8 sleeper cab high roof. The agencies recognize that 

there are truck applications which require on/off-road capability and other truck functions 

which restrict the type of aerodynamic equipment applicable. We also recognize that 

these types of trucks spend less time at highway speeds where aerodynamic technologies 

have the greatest benefit. The 2002 VIUS data ranks trucks by major use.133 The heavy 

trucks usage indicates that up to 35 percent of the trucks may be used in on/off-road 

applications or heavier applications. The uses include construction (16%), agriculture 

(12%), waste management (5%), and mining (2%). Therefore, the agencies analyzed the 

technologies to evaluate the potential restrictions that would prevent 100 percent 

application of SmartWay technologies for all of the tractor regulatory classes.

Trucks designed for on/off-road application may be restricted in the ability to 

improve the aerodynamic design of the bumper, chassis skirts, air cleaners, and other 

aspects of the truck which would typically be needed to move a conventional truck into 

the SmartWay bin. First, off-road applications may require the use of steel bumpers 

which tend to be less aerodynamic than plastic designs. Second, ground clearance may

be an issue for some off road applications due to poor road surface quality. This may

pose a greater likelihood that those items such as chassis skirts would incur damage in 

use and therefore would not be a technology desirable in these applications. Third, the 

trucks used in off-road applications may also experience dust which requires an 

additional air cleaner to manage the dirt. Fourth, some trucks are used in applications 

which require heavier load capacity, such as those with gross combined weights of 

greater than 80,000 pounds, which is today’s federal highway limit. Often these trucks 

are configured with different axle combinations than those traditionally used on-road. 

These trucks may contain either a lift axle or spread axle which allows for greater 

carrying capability. Both of these configurations limit the design and effectiveness of 

chassis skirts. Lastly, some work trucks require the use of power take off (PTO) 

operation or access to equipment which may limit the application of side extenders and 

chassis skirts. 

The agencies considered the on/off-road restriction to aerodynamic technology

application, used VIUS estimate of approximately 35 percent of tractors may be used in 

this type of application, and used confidential data provided by truck manufacturers 

regarding the fraction of their current sales which go into the various applications, to 

project the aerodynamic application rates for each tractor category. For example, the 

agencies project that day cabs with low roofs will be used more often in these on/off-road 

applications than day cabs with high roof. Therefore, the agencies project technology

 

133 U.S. Department of Energy. Transportation Energy Data Book, Edition 28-2009. Table 5.7.
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application rate for conventional aerodynamics in day cab low roof as 40 percent while it 

would be 30 percent in day cab high roofs tractors. The agencies have also estimated that 

the development of advanced aerodynamic technologies would be applied first to high 

roof sleeper cabs and then follow with the other tractor categories. Therefore, the 

agencies propose a 10 percent application rate of the Advanced SmartWay aerodynamic 

technology package to the other tractor categories. The agencies welcome comment on 

our assessment of application rates and are interested in data which provides estimates on 

truck sales to the various applications where aerodynamics are less effective or restricted.

At least one low rolling resistance tire model is available today which meet the 

rolling resistance requirements of the SmartWay and Advanced SmartWay tire packages, 

therefore EPA believes the 2014 model year provides sufficient lead time for tractor 

manufacturers for purposes of the proposed CO2 regulations. However, tire rolling 

resistance is only one of several performance criteria that affect tire selection. The 

characteristics of a tire also influence durability, traction control, vehicle handling, 

comfort, and retreadability. A single performance parameter can easily be enhanced, but 

an optimal balance of all the criteria must be maintained. Tire design requires balancing 

performance, since changes in design may change different performance characteristics 

in opposing directions. Similar to the discussion regarding lesser aerodynamic 

technology application in tractor segments other than sleeper cab high roof, the agencies 

believe that low rolling resistance tires should not be applied to 100% of all tractor 

segments. The agencies are proposing application rates that vary by category and match 

the application rates used for the aerodynamic packages to reflect the on/off-road 

application of some tractors which require a different balancing of traction versus rolling 

resistance. We are seeking comment on our assessment.

Weight reductions can be achieved through single wide tires replacing dual tires 

and lighter weight wheel material. Single wide tires can reduce weight by over 160 

pounds per axle. Aluminum wheels used in lieu of steel wheels will reduce weight by 

over 80 pounds for a dual wheel axle. Light weight aluminum steer wheels and 

aluminum single wide drive wheels and tires package available today would provide a 

670 pound weight reduction over the baseline steel steer and dual drive wheels. The 

agencies are proposing 100% application of a technology package which reduces vehicle 

weight by 400 pounds which takes into account that not all tractors can or will use single 

wide tires. The agencies are unaware of reasons why a combination of lower weight 

wheels or tires cannot be applied to all trucks, but welcome comments. 

Idle reduction technologies provide significant reductions in fuel consumption 

and CO2 emissions for Class 8 sleeper cabs and are available on the market today, and 

therefore will be available in the 2014 model year. There are several different 

technologies available to reduce idling. These include auxiliary power units, diesel fired 

heaters, and battery powered units. Our discussions with manufacturers indicate that idle 

technologies are sometimes installed in the factory, but it is also a common practice to 

have the units installed after the sale of the truck. We would like to continue to 

incentivize this practice while providing certainty that the overnight idle operations will 

be eliminated. Therefore, we are allowing the installation of only an automatic engine 

shutoff, without override capability, to qualify for idle emission reductions in [TEST] to 
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allow for aftermarket installations of idle reduction technology. We are proposing a 100 

percent application rate for this technology for Class 8 sleeper cabs. The agencies are 

unaware of reasons why extended idle reduction technologies could not be applied to all 

tractors with a sleeper cab, but welcome comments. 

Vehicle speed limiters may be used as a technology to meet the standard, but in 

setting the standard we assumed a 0 percent application rate of vehicles speed limiters. 

While we believe vehicles speed limiters are a simple, easy to implement, and 

inexpensive technology, we want to leave the use of vehicles speed limiters to the truck 

purchaser. Since truck fleets purchase trucks today with owner set vehicle speed limiters, 

we considered not including VSLs in our compliance model. However, we have 

concluded that we should allow the use of VSLs that cannot be overridden by the 

operator as a means of compliance for truck OEMs that wish to offer it and truck 

purchasers that wish to purchase the technology. In doing so, we are providing another 

means of meeting that standard that can lower compliance cost and provide a more 

optimal vehicle solution for some truck fleets. For example, a local beverage distributor 

may operate trucks in a distribution network of primarily local roads. Under those 

conditions, aerodynamic fairings used to reduce aerodynamic drag provide little benefit 

due to the low vehicle speed while adding additional mass to the vehicle. An OEM could 

choose to install a VSL set a 55 mph for this customer. The resulting truck modeled in

[TEST] could meet our proposed emission standard without the use of any specialized 

aerodynamic fairings. The resulting truck would be optimized for its intended 

application and would be fully compliant with our program all at a lower cost to the 

ultimate truck purchaser. We are seeking comment on the use of VSLs that cannot be 

overridden by the end-user as a means of compliance with our proposed standards. 

We have chosen not to assume the use of a mandatory vehicle speed limiter in our 

proposal because of concerns about how to set a realistic application rate that avoids 

unintended adverse impacts. While we expect there will be some use of VSL, currently it 

is used when the fleet involved decides it is feasible and practicable and increases the 

overall efficiency of the freight system for that fleet operator. However at this point in 

time the agencies are not in a position to determine how many additional situations would 

be able to use a VSL with similar benefits to overall efficiency. Setting a mandatory

expected use of such VSL carries the risk of requiring VSL in situations that are not 

appropriate from an efficiency perspective. To avoid such error, the agencies are not 

using a specified application rate for VSL, and instead will rely on the industry to select 

VSL when circumstances are appropriate for its use. Implementation of this program 

may provide greater information for using this technology in standard setting in the 

future. Many stakeholders including the American Trucking Association have advocated 

for more widespread use of vehicle speed limits to address fuel efficiency and greenhouse 

gas emissions. We welcome comments on our decision not to premise the emission 

standards on the use of VSLs. 

Table III-4 provides the proposed application rates of each technology broken 

down by weight class, cab configuration, and roof height.
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Table III-4 – Proposed Technology Application Rates for Class 7 and 8 Tractors

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low Roof High Roof Low Roof High Roof Low 

Roof

Mid Roof High 

Roof

Aerodynamics (Cd)

Classic 0% 0% 0% 0% 0% 10% 0%

Conventional 40% 30% 40% 30% 30% 20% 10%

SmartWay 50% 60% 50% 60% 60% 60% 70%

Advanced SmartWay 10% 10% 10% 10% 10% 10% 20%

Advanced SmartWay 

II

0% 0% 0% 0% 0% 0% 0%

Steer Tires (Crr kg/metric ton)

Baseline 40% 30% 40% 30% 30% 30% 10%

SmartWay 50% 60% 50% 60% 60% 60% 70%

Advanced SmartWay 10% 10% 10% 10% 10% 10% 20%

Drive Tires (Crr kg/metric ton)

Baseline 40% 30% 40% 30% 30% 30% 10%

SmartWay 50% 60% 50% 60% 60% 60% 70%

Advanced SmartWay 10% 10% 10% 10% 10% 10% 20%

Weight Reduction (lbs.)

Baseline 0% 0% 0% 0% 0% 0% 0%

Control 100% 100% 100% 100% 100% 100% 100%

Extended Idle Reduction (gram CO2/ton-mile reduction)

Baseline Not 

Applicabl

e

Not 

Applicable

Not 

Applicabl

e

Not 

Applicabl

e

0% 0% 0%

Control Not 

Applicabl

e

Not 

Applicable

Not 

Applicabl

e

Not 

Applicabl

e

100% 100% 100%

Vehicle Speed Limiter

Baseline 0% 0% 0% 0% 0% 0% 0%

Control 0% 0% 0% 0% 0% 0% 0%

(iv) Derivation of the Proposed Tractor Standards

The agencies used the technology inputs and proposed technology application 

rates in [TEST] to develop the fuel consumption and CO2 emissions standards for each 

subcategory of Class 7/8 combination tractors. The agencies derived a scenario truck for 

each subcategory by weighting the individual [TEST] input parameters included in Table 

III-3 by the application rates in Table III-4. For example, the Cd value for a Class 8 

Sleeper Cab High Roof scenario case was derived as 10 percent times 0.68 plus 70 
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percent times 0.60 plus 20 percent times 0.55, which is equal to a Cd of 0.60. Similar 

calculations were done for tire rolling resistance, weight reduction, idle reduction, and 

vehicle speed limiters. To account for the two proposed engine standards, EPA is 

proposing the use of a 2014 model year fuel consumption map in [TEST] to derive the 

2014 model year tractor standard and a 2017 model year fuel consumption map to derive 

the 2017 model year tractor standard. The agencies then ran [TEST] with a single set of 

vehicle inputs, as shown in Table III-5, to derive the standards for each subcategory. 

Additional detail is provided in the draft RIA Chapter 2. 

Table III-5: [TEST] Inputs for the Class 7/8 Tractor Standard Setting

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low Roof High Roof Low Roof High Roof Low Roof Mid Roof High Roof

Aerodynamics (Cd) 0.77 0.62 0.77 0.62 0.76 0.69 0.620

Steer Tire CRR 

(kg/metric ton)

6.99 6.87 6.99 6.87 6.87 6.87 6.54

Drive Tire CRR 

(kg/metric ton)

7.38 7.26 7.38 7.26 7.26 7.26 6.92

Weight Reduction (lbs.) 400 400 400 400 400 400 400

Extended Idle Reduction 

(g/ton-mile)

-- -- -- -- 5 5 5

Vehicle Speed Limiter -- -- -- -- -- -- --

2014 MY Standard

Engine 2014 MY 

11L

2014 MY 

11L

2014 MY 

15L

2014 MY 

15L

2014 MY 

15L

2014 MY 

15L

2014 MY 

15L

2017 MY Standard

Engine 2017 MY 

11L

2017 MY 

11L

2017 MY 

15L

2017 MY 

15L

2017 MY 

15L

2017 MY 

15L

2017 MY 

15L

The level of the 2017 model year standard and percent reduction over the baseline 

for each class is included in Table III-6.

Table III-6: Proposed 2017 Model Year Tractor Reductions

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low Roof High Roof Low Roof High Roof Low Roof Mid Roof High Roof

Fuel Consumption 

Standard (gallon/1000 tonmile)

10.4 11.8 7.9 8.6 6.4 6.4 7.1

CO2 Standard (grams 

CO2/ton-mile)

106 120 80 88 65 65 72

Percent Reduction 9% 12% 7% 10% 15% 16% 19%

A summary of the proposed technology package costs is included in Table III-7

with additional details available in the draft RIA Chapter 2.
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Table III-7: Class 7-8 Tractor Technology Costs inclusive of Indirect Cost Markups in the 2014 

Model Yeara(2008$)

Class 7 Class 8

Day Cab Day Cab Sleeper Cab

Low 

Roof

High 

Roof

Low 

Roof

High 

Roof

Low 

Roof

Mid 

Roof

High 

Roof

Aerodynamics $975 $1,216 $647 $1,215 $1,025 $1,152 $1,527

Steer Tires $65 $65 $65 $65 $65 $65 $65

Drive Tires $60 $60 $121 $121 $121 $121 $121

Weight 

Reduction

$1,472 $1,472 $2,421 $2,421 $2,421 $2,421 $2,421

Auxiliary Power 

Unit

N/A N/A N/A N/A $5,228 $5,228 $5,228

Air Conditioning $21 $21 $21 $21 $21 $21 $21

Total $2,593 $2,835 $3,275 $3,842 $8,881 $9.007 $9,382

a Costs shown are for the 2014 model year so do not reflect learning impacts which would result in lower costs 

for later model years. For a description of the learning impacts considered in this analysis and how it impacts 

technology costs for other years, refer to Chapter 2 of the draft RIA.

b

Note that values in this table include penetration rates. Therefore, the technology costs shown reflect the 

average cost expected for each of the indicated classes. To see the actual estimated technology costs exclusive of 

penetration rates, refer to Chapter 2 of the draft RIA.

(v) Alternative Tractor Standards Considered

The agencies are not proposing tractor standards less stringent than the proposed 

standards because the agencies believe these standards are appropriate, highly cost 

effective, and technologically feasible within the rulemaking time frame.

The agencies considered proposing tractor standards which are more stringent 

than the proposed reflecting either the increased application rates of the technologies 

discussed or the inclusion of hybrid powertrains in tractors. The agencies have proposed 

the maximum application rates feasible for the various tractor categories and their 

associated use. However, the agencies welcome comment on the application rates for 

each type of technology and for each tractor category. 
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The agencies are not proposing a level of stringency premised on the use of 

hybrid technologies because our assessment is that the high cost of hybrids134 with the 

relatively low improvement is not cost effective for inclusion the 2017 model year. The 

agencies welcome comments on whether hybrid technologies are appropriate to consider 

for the 2017 model year standard, or if not, then when would they be appropriate.

(b) Tractor Engines

(i) Baseline Engine Performance

EPA and NHTSA developed the reference medium and heavy heavy-duty diesel 

engine to represent a 2010 model year engine compliant with the 0.2 g/bhp-hr NOx 

standard for on-highway heavy duty engines. 

The agencies developed baseline SET values for medium and heavy heavy-duty

diesel engines based on 2009 model year confidential manufacturer data and from testing 

conducted by EPA. The agencies adjusted the pre-2010 data to represent 2010 model 

year engine maps by using predefined technologies including SCR and other systems that 

are being used in current 2010 model year production. If an engine utilized did not meet 

the 0.2 g/bhp-hr NOx level, then the individual engine’s CO2 result was adjusted to 

accommodate aftertreatment strategies that would result in a 0.2 g/bhp-hr NOx emission 

level as described in DRIA Chapter 2. The engine CO2 results were then sales weighted 

within each regulatory class to develop an industry average 2010 model year reference 

engine. While most of the engines fell within a few percent of this baseline at least one 

engine was more than six percent above this average baseline.

Table III-8: 2010 Model Year Baseline Diesel Engine Performance

CO2 Emissions 

(g/bhp-hr)

Fuel Consumption 

(gallon/100 bhp-hr)

Medium Heavy Diesel - SET 518 5.09

Heavy Heavy Diesel - SET 490 4.81

(ii) Engine Technology Package Effectiveness 

The MHDD and HHDD engine technology package for the 2014 model year 

includes engine friction reduction, improved aftertreatment effectiveness, improved 

combustion processes, and low temperature EGR system optimization. The agencies 

 

134 The NAS Report estimated that hybrid powertrains for tractors would cost $25,000 and provide a 10 

percent reduction, though 6 percent of that reduction is already achievable through the extended idle 

reduction technologies included in the proposal (NAS Report, page 6-28).
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considered improvements in parasitic and friction losses through piston designs to reduce 

friction, improved lubrication, and improved water pump and oil pump designs to reduce 

parasitic losses. The aftertreatment improvements are available through lower 

backpressure of the systems and optimization of the engine-out NOx levels. 

Improvements to the EGR system and air flow through the intake and exhaust systems, 

along with turbochargers can also produce engine efficiency improvements. We note that 

individual technology improvements are not additive to each other due to the interaction 

of technologies. The agencies assessed the impact of each technology over each of the 13 

SET modes to project an overall weighted SET cycle improvement in the 2014 model 

year of 3 percent, as detailed in DRIA Chapter 2. The agencies proposal reflects a 100 

percent application rate of this technology package. 

Recently, EPA’s non-GHG heavy duty engine program provided new criteria 

pollutant emissions standards for the industry in three year increments. The heavy duty 

engine manufacturer product plans have fallen into three year cycles to reflect these 

requirements. The agencies are proposing set fuel consumption and CO2 emission 

standards recognizing the opportunity for technology improvements over this timeframe 

while reflecting the typical heavy duty engine manufacturer product plan cycles. Thus, 

the agencies are proposing to set a more stringent standard for heavy duty engines 

beginning in the 2017 model year.

The MHDD and HHDD engine technology package for the 2017 model year 

includes the continued development of the 2014 model year technology package plus 

turbocompounding. A similar approach to evaluating the impact of individual 

technologies as taken to develop the overall reduction of the 2014 model year package 

was taken with the 2017 model year package. The weighted SET cycle improvements 

lead to a 6 percent reduction on the SET cycle, as detailed in DRIA Chapter 2. The 

agencies proposal is premised on a 100 percent application rate of this technology

package. The agencies believe that bottom cycling technologies are still in the 

development phase and will not be ready for production by the 2017 model year.135

Therefore, these technologies were not included in determining the stringency of the 

proposed standards. However, we do believe the bottoming cycle approach represents a 

significant opportunity to reduce fuel consumption and GHG emissions in the future. 

EPA and NHTSA are therefore both proposing provisions described in Section IV to 

create incentives for manufacturers to continue to invest to develop this technology.

(iii) Derivation of Engine Standards 

EPA developed the proposed 2014 model year CO2 emissions standards for diesel 

engines by applying the three percent reduction from the technology package to the 2010 

model year baseline values. EPA developed the 2017 model year CO2 emissions 

standards for diesel engines while NHTSA similarly developed the 2017 model year 

 

135 TIAX noted in their report to the NAS commitee that the engine improvements beyond 2015 model year 

included in their report are highly uncertain, though they include waste heat recovery in the engine package 

for 2016 through 2020 (page 4-29).
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diesel engine fuel consumption standards by applying the 6 percent reduction from the 

2017 model year technology package (reflecting performance of turbocompounding) to 

the 2010 model year baseline values. The proposed standards are included in Table III-9.

Table III-9: Proposed Diesel Engine Standards

Effective 2014 Model Year

MHDD - SET HHDD - SET

CO2 Standard (g/bhp-hr) 502 475

Optional Fuel Consumption 

Standard (gallon/100 bhp-hr)

4.93 4.67

Effective 2017 Model Year

MHDD - SET HHDD - SET

CO2 Standard (g/bhp-hr) 487 460

Fuel Consumption (gallon/100 

bhp-hr)

4.78 4.52

(iv) Engine Technology Package Costs

EPA has historically used two different approaches to estimate the indirect costs 

(sometimes called fixed costs) of regulations including costs for product development, 

machine tooling, new capital investments and other general forms of overhead that do not 

change with incremental changes in manufacturing volumes. Where the Agency could 

reasonably make a specific estimate of individual components of these indirect costs, 

EPA has done so. Where EPA could not readily make such an estimate, EPA has instead 

relied on the use of markup factors referred to as Indirect Cost Multipliers (ICMs) to 

estimate these indirect costs as a ratio of direct manufacturing costs. In general, EPA has 

used whichever approach it believed could provide the most accurate assessment of cost 

on a case by case basis. The agencies’ general approach used elsewhere in this proposal 

(for HD pickup trucks, gasoline engines, Class 7/8 tractors, and Class 2b-8 vocational 

trucks) estimates indirect costs based on the use of ICMS. See also 75 FR at 25376. We 

have used this approach generally because these standards are based on installing new 

parts and systems purchased from a supplier. In such a case, the supplier is conducting 

the bulk of the research and development on the new parts and systems and including 

those costs in the purchase price paid by the original equipment manufacturer. In this 

situation, we believe that the ICM approach provides an accurate and clear estimate of 

the additional indirect costs borne by the manufacturer. 

For the heavy-duty diesel engine segment, however, the agencies do not consider 

this model to be the most appropriate because the primary cost is not expected to be the 

purchase of parts or systems from suppliers or even the production of the parts and 

systems, but rather the development of the new technology by the original equipment 

manufacturer itself. Most of the technologies the agencies are projecting the heavy-duty 

engine manufacturers will use for compliance reflect modifications to existing engine 

systems rather than wholesale addition of technology (e.g., improved turbochargers rather 
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than adding a turbocharger where it did not exist before as was done in our light-duty

joint rulemaking in the case of turbo-downsizing). When the bulk of the costs come from 

refining an existing technology rather than a wholesale addition of technology, a specific 

estimate of indirect costs may be more appropriate. For example, combustion 

optimization may significantly reduce emissions and cost a manufacturer millions of 

dollars to develop but will lead to an engine that is no more expensive to produce. Using 

a bill of materials approach would suggest that the cost of the emissions control was zero 

reflecting no new hardware and ignoring the millions of dollars spent to develop the 

improved combustion system. Details of the cost analysis are included in the DRIA 

Chapter 2.

The agencies developed the engineering costs for the research and development of 

diesel engines with lower fuel consumption and CO2 emissions. The aggregate costs for 

engineering hours, technician support, dynamometer cell time, and fabrication of 

prototype parts are estimated at $6,750,000 per manufacturer per year over the five years 

covering 2012 through 2016. In aggregate, this average out to $530 per engine during 

2012 through 2016 using an annual sales value of 280,000 medium-HD and heavy-HD 

engines. The agencies also are estimating costs of $100,000 per engine manufacturer per 

engine class (medium-HD and heavy-HD) to cover the cost of purchasing photo-acoustic 

measurement equipment for two engine test cells. This would be a one-time cost incurred 

in the year prior to implementation of the standard (i.e., the cost would be incurred in 

2013). In aggregate, this averages out to $4 per engine in 2013 using an annual sales 

value of 280,000 medium-HD and heavy-HD engines.

Where we projected that additional new hardware was needed to the meet the 

proposed standards, we developed the incremental costs for those technologies and 

marked them up using the ICM approach. Table III-10 below summarizes those estimates 

of cost on a per item basis. All costs shown in Table III-18 include a low complexity

ICM of 1.11 and time based learning is considered applicable to each technology.

Table III-10: Heavy-duty Diesel Engine Component Costs for Tractors (2008$)
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2014 Model 

Year

2017 Model 

Year

Cylinder Head (flow optimized, increased firing 

pressure, improved thermal management)

$6 $6

Exhaust Manifold (flow optimized, improved 

thermal management)

$0 $0

Turbocharger (improved efficiency) $17 $16

EGR Cooler (improved efficiency) $3 $3

Water Pump (optimized, variable vane, variable 

speed)

$87 $79

Oil Pump (optimized) $4 $4

Fuel Pump (higher working pressure, increased 

efficiency, improved pressure regulation)

$4 $4

Fuel Rail (higher working pressure) $10 $9

Fuel Injector (optimized, improved multiple event 

control, higher working pressure)

$10 $9

Piston (reduced friction skirt, ring and pin) $3 $2

Aftertreatment system (improved effectiveness 

SCR, dosing, dpf)a

$0 $0

Valve Train (reduced friction, roller tappet) $78 $71

Mechanical Turbocompounding $0 $823

a Note that costs for aftertreatment improvements for MH and HH diesel engines are covered via the 

engineering costs (see text). For LH diesel engines, we have included the cost of aftertreatment 

improvements as a technology cost.

The overall diesel engine technology package cost for a medium HD engine is 

$223 in the 2014 model year and $203 in the 2017 model year; for a heavy HD engine 

these costs are $145 and $132, respectively; and for a heavy HD engine placed in a Class 

8 sleeper cab these costs are $145 and $955, respectively. The differences for the medium 

HD engines are the valve train friction reduction costs of $78 in 2014 ($71 in 2017) that 

are not applied to heavy HD engines, and for Class 8 sleeper cab engines the difference is 

the turbocompounding cost of $823 in 2017 which is not applied to other engines. 

(v) Alternative Engine Standards Considered

The agencies are not proposing engine standards less stringent than the proposed 

standards because the agencies believe these proposed standards are appropriate, highly 

cost effective, and technologically feasible, as described in Section VIII.

The agencies considered proposing engine standards which are more stringent 

reflecting the inclusion of advanced heat recovery systems, such as Rankine or bottoming 

cycles. However, the agencies are not proposing this level of stringency because our 

assessment is that these technologies would not be available for production by the 2017 

model year. The agencies welcome comments on whether waste heat recovery

technologies are appropriate to consider for the 2017 model year standard, or if not, then 

when would they be appropriate.
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B. Class 2b and 3 Complete Pickup Trucks and Vans

The process used to determine the standards the agencies are proposing for HD 

pickups and vans is described here. We started by gathering available information about 

the fuel consumption and CO2 emissions from recent model year vehicles. The core 

portion of this information comes primarily from EPA’s certification databases, CFEIS 

and VERIFY, which maintain the publicly available data136 regarding emission and fuel 

economy results. This information is not extensive because manufacturers have not been 

required to chassis test HD diesel vehicles for EPA’s criteria pollutant emissions 

standards, nor have they been required to conduct any testing of heavy-duty vehicles on 

the highway cycle. Nevertheless, enough certification activity has occurred for diesels 

under EPA’s optional chassis-based program, and due to a California NOx requirement 

for the highway test cycle, enough test results have been voluntarily reported for both 

diesel and gasoline vehicles using the highway test cycle, to yield a reasonably robust 

data set. To supplement this data set, for purposes of this rulemaking EPA initiated its 

own testing program using in-use vehicles. This program and the results from it thus far 

are described in a memorandum to the docket for this rulemaking.137

Heavy-duty pickup trucks and vans are sold in a variety of configurations to meet 

market demands. Among the differences in these configurations that affect CO2

emissions and fuel consumption are curb weight, GVWR, axle ratio, and drive wheels 

(2wd or 4wd). Because the currently-available test data set does not capture all of these 

configurations, it is necessary to extend that data set across the product mix using 

adjustment factors. In this way a test result from, say a truck with 2wd, 3.73:1 axle ratio, 

and 8000 lb test weight, can be used to model emissions and fuel consumption from a 

truck of the same basic body design, but with 4wd, a 4.10:1 axle ratio, and 8500 lb test 

weight. The adjustment factors are based on data from testing in which only that 

parameter is varied. These parameterized adjustments and their basis are also described 

in a memorandum to the docket for this rulemaking.138

The agencies requested and received from each of the three major manufacturers 

confidential information for each model and configuration, indicating the values of each 

of these key parameters as well as the annual production (for the U.S. market). 

Production figures are useful because, under our proposed standards for HD pickups and 

vans, compliance is judged on the basis of production-weighted (corporate average) 

emissions or fuel consumption level, not individual vehicle levels. For consistency and 

to avoid confounding the analysis with data from unusual market conditions in 2009, the 

production and vehicle specification data is from the 2008 model year. We made the 

simplifying assumption that these sales figures reasonably approximate future sales for 

purposes of this analysis.

 

136 http://www.epa.gov/otaq/certdata.htm

137 Xx CJ memo cite

138 (xx cite TF memo to docket)
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One additional assessment was needed to make the data set useful as a baseline 

for the standards selection. Because the appropriate standards are determined by

applying efficiency-improving technologies to the baseline fleet, it is necessary to know 

the level of penetration of these technologies in the latest model year (2010) already. 

This information was also provided confidentially by the manufacturers. Generally, the 

agencies found that the HD pickup and van fleet was at a roughly consistent level of 

technology application, with (1) the transition from 4-speed to 5- or 6-speed automatic 

transmissions mostly accomplished, (2) coupled cam phasing to achieve variable valve 

control on gasoline engines likewise mostly in place, and (3) substantial remaining 

potential for optimizing catalytic diesel NOx after treatment to improve fuel economy 

(the new heavy duty NOx standards having taken effect in the 2010 model year).

Taking this 2010 baseline fleet, and applying the technologies determined to be 

feasible and appropriate by the 2018 model year, along with their effectiveness levels, the 

agencies could then make a determination of appropriate standards. The assessment of 

feasibility, described in Section III.xx, took into account the projected costs of these 

technologies. The derivation of these costs, largely based on analyses developed in the 

light-duty GHG and fuel economy rulemaking, are described at the beginning of Section 

II and in Section III.xx.

Our assessment concluded that the technologies that the agencies considered 

feasible and appropriate for HD pickups and vans could be consistently applied to all 

vehicles across this sector by the 2018 model year. Therefore we did not apply varying 

penetration rates across vehicle types and models in developing and evaluating the 

standards. The reader should remember, as explained in Section II.xx, that our decision 

to set standards that vary linearly according to a weight-based attribute (work factor) was 

appropriate, not to limitations in the application of technologies across the HD pickup 

and van fleet, but rather to the impact that increasing test weight driven by the work

factor attribute has on CO2 emissions and fuel consumption, and on the correlation of 

HD vehicle utility to the work factor. 

Since the manufacturers of HD pickups and vans generally only have one basic 

pick-up truck and van with different versions ((i.e., different wheel bases, cab sizes, 2wd, 

4wd, etc.) and do not have the flexibility of the light-duty like fleet to coordinate model 

improvements over several years, changes to the HD pickups and vans to meet new 

standards must be carefully planned with the redesign cycle taken into account. The 

opportunities for large-scale changes (e.g., new engines, transmission, vehicle body and 

mass) occur less frequently than in the light duty fleet, typically at spans of 8 or more 

years. However, opportunities for gradual improvements not necessarily linked to large 

scale changes can occur between the redesign cycles like upgrades to existing vehicle’s 

engine, transmission and aftertreatment systems. Given this long redesign cycle and our 

understanding with respect to where the different manufactures are in that cycle, the 

agencies determined that the full implementation of the new standards would be feasible 

and appropriate by the 2018 model year. 

Although we did not determine that it was necessarily for feasibility to apply

varying technology levels to different vehicles, we did decide that a phased 
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implementation schedule would be appropriate to accommodate manufacturers’ redesign 

workload and product schedules, especially in light of this sector’s relatively low sales 

volumes and long product cycles. We did not determine a specific cost of implementing 

the final standards immediately in 2014 without a phase-in, but we assessed it to be much 

higher than the cost of the phase-in we are proposing, due to the workload and product 

cycle disruptions it would cause, and also due to manufacturers’ resulting need it would 

entail to develop some of these technologies for heavy-duty applications sooner than or 

simultaneously with light-duty development efforts. On the other hand, waiting until 

2018 before applying any new standards could miss the opportunity to achieve 

meaningful and cost-effective early reductions not requiring a major product redesign 

cycle when the largest changes and reductions are expected to occur.

The proposed phase-in schedule, 15-20-40-60-100 percent in 2014-2015-2016-

2017-2018, respectively, was chosen to strike a balance between meaningful reductions 

in the early years (15 and 20 percent) and providing manufacturers with needed time via 

a gradually accelerating ramp-up. 139 By expressing the proposed phase-in in terms of 

increasing fleet wide stringency for each manufacturer, while also providing for credit 

generation and use (including averaging, carry-forward, and carry-back), we believe we 

have afforded manufacturers substantial flexibility to satisfy the phase-in through a 

variety of pathways: the gradual application of technologies across the fleet, greater 

application levels on only a portion of the fleet, or a mix of the two. 

We considered setting more stringent standards that would require the application 

of additional technologies by 2018. We expect, in fact, that some of these technologies 

may well prove feasible and cost-effective in this timeframe, and may even become 

technologies of choice for individual manufacturers. This dynamic has played out in 

EPA programs before and highlights the value of setting performance-based standards 

that leave engineers the freedom to find the most cost-effective solutions. 

However, the agencies do believe that at this stage there is not enough 

information to conclude that the additional technologies provide an appropriate basis for 

standard-setting. For example, we believe that 42V stop-start systems can be applied to 

gasoline vehicles with significant GHG and fuel consumption benefits, but we recognize 

that there is uncertainty at this time over the cost-effectiveness of these systems in heavyduty applications, and over customer acceptance of vehicles towing large loads that 

would routinely stop running at idle. Hybrid electric technology too could be applied to 

heavy-duty vehicles, and in fact has already been so applied on a limited basis. However, 

the development, design, and tooling effort needed to apply this technology to a vehicle 

model is quite large, and seems less likely to prove cost-effective in this timeframe, due 

to the small sales volumes relative to the light-duty sector. Here again, potential 

customer acceptance would need to be better understood because the smaller engines that 

facilitate much of a hybrid’s benefit are typically at odds with the importance pickup 

 

139 The NHTSA proposal,provides a voluntary opt-in for model years 2014 and 2015. NHTSA also 

provides an alternative standard that meets EISA’s requirement for three years of regulatory stability. See 

Section II.C.d.ii for a more detailed discussion.
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trucks buyers place on engine horsepower and torque, whatever the vehicle’s real 

performance.

We also considered setting less stringent standards calling for a more limited set 

of applied technologies. However, our assessment concluded with a high degree of 

confidence that the technologies chosen as the basis for our proposal are clearly feasible 

in the 2014-2018 timeframe, and that the phase-in and other flexibility provisions allow 

for their application in a very cost-effective manner.

More difficult to characterize is the degree to which more or less stringent 

standards might be appropriate because of under- or over-estimating effectiveness for 

technologies we are applying. Our basis for these estimates is described in Section III.xx. 

Because for the most part these technologies have not yet been applied to HD pickups 

and vans, even on a limited basis, we are relying to some degree on engineering 

judgment. Even so, we believe that we have applied this judgment using the best 

information available, primarily from our recent rulemaking on light-duty vehicle GHGs 

and fuel economy, and have generated a robust set of effectiveness values. 

We solicit comment and new information that would aid the agencies in 

establishing the appropriate level of stringency for the HD pickup and van standards, and 

on all facets of the assessment described above and elsewhere in these rulemaking 

proposals.

(1) What technologies did the agencies consider?

The agencies considered over 35 vehicle technologies that manufacturers could 

use to improve the fuel consumption and reduce CO2 emissions of their vehicles during 

MYs 2014-2018. The majority of the technologies described in this section are readily 

available, well known, and could be incorporated into vehicles once production decisions 

are made. Other technologies considered may not currently be in production, but are 

beyond the research phase and under development, and are expected to be in production 

in the next few years. These are technologies which are capable of achieving significant 

improvements in fuel economy and reductions in CO2 emissions, at reasonable costs. 

The agencies did not consider technologies in the research stage because the lead time 

available for this proposal is not sufficient to move such technologies from research to 

production.

The technologies considered in the agencies’ analysis are briefly described below. 

They fall into five broad categories: engine technologies, transmission technologies, 

vehicle technologies, electrification/accessory technologies, and hybrid technologies.

In this class of trucks and vans, diesel engines are installed in about half of all 

vehicles. The ratio between gasoline and diesel engine purchases by consumers has 

tended to track changes in the overall cost of oil and the relative cost of gasoline and 

diesel fuels. When oil prices are higher, diesel sales tend to increase. This trend has 

reversed when oil prices fall or when diesel fuel prices are significantly higher than 

gasoline. In the context of our technology discussion for heavy-duty pickups and vans, 
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we are treating gasoline and diesel engines separately so each has a set of baseline 

technology. We discuss performance improvements in terms of changes to those baseline 

engines. Our cost and inventory estimates contained elsewhere reflect the current fleet 

baseline with an appropriate mix of gasoline and diesel engines. Types of engine 

technologies that improve fuel efficiency and reduce CO2 emissions include the 

following:

 Low-friction lubricants – low viscosity and advanced low friction lubricants oils 

are now available with improved performance and better lubrication. If 

manufacturers choose to make use of these lubricants, they would need to make 

engine changes and possibly conduct durability testing to accommodate the lowfriction lubricants. 

 Reduction of engine friction losses – can be achieved through low-tension piston 

rings, roller cam followers, improved material coatings, more optimal thermal 

management, piston surface treatments, and other improvements in the design of 

engine components and subsystems that improve engine operation.

 Cylinder deactivation – deactivates the intake and exhaust valves and prevents 

fuel injection into some cylinders during light-load operation. The engine runs 

temporarily as though it were a smaller engine which substantially reduces 

pumping losses. 

 Variable valve timing – alters the timing of the intake valve, exhaust valve, or 

both, primarily to reduce pumping losses, increase specific power, and control 

residual gases.

 Stoichiometric gasoline direct-injection technology – injects fuel at high pressure 

directly into the combustion chamber to improve cooling of the air/fuel charge 

within the cylinder, which allows for higher compression ratios and increased 

thermodynamic efficiency. 

 Diesel engine improvements and diesel aftertreatment improvements – improved 

EGR systems and advanced timing can provide more efficient combustion and, 

hence, lower fuel consumption. Aftertreatment systems are a relatively new 

technology on diesel vehicles and, as such, improvements are expected in coming 

years that allow the effectiveness of these systems to improve while reducing the 

fuel and reductant demands of current systems. 

Types of transmission technologies considered include:

 Improved automatic transmission controls – optimizes shift schedule to maximize 

fuel efficiency under wide ranging conditions, and minimizes losses associated 

with torque converter slip through lock-up or modulation.
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 Six-, seven-, and eight-speed automatic transmissions – the gear ratio spacing and 

transmission ratio are optimized for a broader range of engine operating 

conditions. 

Types of vehicle technologies considered include:

 Low-rolling-resistance tires – have characteristics that reduce frictional losses 

associated with the energy dissipated in the deformation of the tires under load, 

therefore improving fuel efficiency and reducing CO2 emissions.

 Aerodynamic drag reduction – is achieved by changing vehicle shape or reducing 

frontal area, including skirts, air dams, underbody covers, and more aerodynamic 

side view mirrors.

 Mass reduction and material substitution – Mass reduction encompasses a variety 

of techniques ranging from improved design and better component integration to 

application of lighter and higher-strength materials. Mass reduction is further 

compounded by reductions in engine power and ancillary systems (transmission, 

steering, brakes, suspension, etc.). The agencies recognize there is a range of 

diversity and complexity for mass reduction and material substitution 

technologies and there are many techniques that automotive suppliers and 

manufacturers are using to achieve the levels of this technology that the agencies 

have modeled in our analysis for this proposal. 

Types of electrification/accessory and hybrid technologies considered include:

 Electric power steering (EPS) and Electro-Hydraulic power steering (EHPS) –

are electrically-assisted steering systems that have advantages over traditional 

hydraulic power steering because it replaces a continuously operated hydraulic 

pump, thereby reducing parasitic losses from the accessory drive.

 Improved accessories (IACC) – may include high efficiency alternators, 

electrically driven (i.e., on-demand) water pumps and cooling fans. This excludes 

other electrical accessories such as electric oil pumps and electrically driven air 

conditioner compressors.

 Air Conditioner Systems – These technologies include improved hoses, 

connectors and seals for leakage control. They also include improved 

compressors, expansion valves, heat exchangers and the control of these 

components for the purposes of improving tailpipe CO2 emissions as a result of 

A/C use. 
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(2) How did the agencies determine the costs and effectiveness of each of these 

technologies?

Building on the technical analysis underlying the 2012-2016 light-duty final rule, 

the agencies took a fresh look at technology cost and effectiveness values for purposes of 

this proposal. For costs, the agencies reconsidered both the direct or “piece” costs and 

indirect costs of individual components of technologies. For the direct costs, the agencies 

followed a bill of materials (BOM) approach employed by NHTSA and EPA in the 2012-

2016 light-duty rule. 

For two technologies (stoichiometric gasoline direct injection and turbocharging 

with engine downsizing), the agencies relied, to the extent possible, on the tear down data 

available and scaling methodologies used in EPA’s ongoing study with FEV. This study

consists of complete system tear-down to evaluate technologies down to the nuts and 

bolts to arrive at very detailed estimates of the costs associated with manufacturing 

them.140 

For the other technologies, considering all sources of information and using the 

BOM approach, the agencies worked together intensively to determine component costs 

for each of the technologies and build up the costs accordingly. Where estimates differ 

between sources, we have used engineering judgment to arrive at what we believe to be 

the best cost estimate available today, and explained the basis for that exercise of 

judgment.

Once costs were determined, they were adjusted to ensure that they were all 

expressed in 2008 dollars using a ratio of GDP values for the associated calendar 

years,141 and indirect costs were accounted for using the new approach developed by EPA 

and used in the 2012-2016 light-duty rule. NHTSA and EPA also reconsidered how costs 

should be adjusted by modifying or scaling content assumptions to account for 

differences across the range of vehicle sizes and functional requirements, and adjusted 

the associated material cost impacts to account for the revised content, although some of 

these adjustments may be different for each agency due to the different vehicle subclasses 

used in their respective models. 

Regarding estimates for technology effectiveness, NHTSA and EPA used the 

estimates from the 2012-2016 light-duty rule as a baseline but adjusted them as 

appropriate, taking into account the unique requirement of the heavy duty test cycles to 

test at curb weight plus half payload versus the light-duty requirement of curb plus 300

lbs. The adjustments were made on an individual technology basis by assessing the 

specific impact of the added load on each technology when compared to the use of the 

 

140 U.S. Environmental Protection Agency, “Draft Report – Light-Duty Technology Cost Analysis Pilot 

Study,” Contract No. EP-C-07-069, Work Assignment 1-3, September 3, 2009.

141 NHTSA examined the use of the CPI multiplier instead of GDP for adjusting these dollar values, but 

found the difference to be exceedingly small – only $0.14 over $100.
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technology on a light-duty vehicle. The agencies also considered other sources such as

the March 2010 NAS Report, recent CAFE compliance data, and confidential 

manufacturer estimates of technology effectiveness. NHTSA and EPA engineers 

reviewed effectiveness information from the multiple sources for each technology and 

ensured that such effectiveness estimates were based on technology hardware consistent 

with the BOM components used to estimate costs. Together, the agencies compared the 

multiple estimates and assessed their validity, taking care to ensure that common BOM 

definitions and other vehicle attributes such as performance and drivability were taken 

into account. 

The agencies note that the effectiveness values estimated for the technologies may

represent average values applied to the baseline fleet described earlier, and do not reflect 

the potentially-limitless spectrum of possible values that could result from adding the 

technology to different vehicles. For example, while the agencies have estimated an 

effectiveness of 0.5 percent for low friction lubricants, each vehicle could have a unique 

effectiveness estimate depending on the baseline vehicle’s oil viscosity rating. Similarly, 

the reduction in rolling resistance (and thus the improvement in fuel economy and the 

reduction in CO2 emissions) due to the application of low rolling resistance tires depends 

not only on the unique characteristics of the tires originally on the vehicle, but on the 

unique characteristics of the tires being applied, characteristics which must be balanced 

between fuel efficiency, safety, and performance. Aerodynamic drag reduction is much 

the same—it can improve fuel economy and reduce CO2 emissions, but it is also highly 

dependent on vehicle-specific functional objectives. For purposes of this NPRM, 

NHTSA and EPA believe that employing average values for technology effectiveness 

estimates is an appropriate way of recognizing the potential variation in the specific 

benefits that individual manufacturers (and individual vehicles) might obtain from adding 

a fuel-saving technology. However, the agencies seek comment on whether additional 

levels of specificity beyond that already provided would improve the analysis for the 

final rules, and if so, how those levels of specificity should be analyzed.

The following section contains a detailed description of our assessment of vehicle 

technology cost and effectiveness estimates. The agencies note that the technology costs 

included in this NPRM take into account only those associated with the initial build of 

the vehicle. The agencies seek comment on the additional lifetime costs, if any, 

associated with the implementation of advanced technologies including maintenance and 

replacement costs. Based on comments, the agencies may decide to conduct additional 

analysis for the final rules regarding operating, maintenance and replacement costs.

(a) Engine Technologies

NHTSA and EPA have reviewed the engine technology estimates used in the 

2012-2016 light-duty rule. In doing so NHTSA and EPA reconsidered all available 

sources and updated the estimates as appropriate. The section below describes both 

diesel and gasoline engine technologies considered for this proposal.
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(i) Low Friction Lubricants (LUB)

One of the most basic methods of reducing fuel consumption in both gasoline and 

diesel engines is the use of lower viscosity engine lubricants. More advanced multiviscosity engine oils are available today with improved performance in a wider 

temperature band and with better lubricating properties. This can be accomplished by

changes to the oil base stock (e.g., switching engine lubricants from a Group I base oils to 

lower-friction, lower viscosity Group III synthetic) and through changes to lubricant 

additive packages (e.g., friction modifiers and viscosity improvers). The use of 5W-30 

motor oil is now widespread and auto manufacturers are introducing the use of even 

lower viscosity oils, such as 5W-20 and 0W-20, to improve cold-flow properties and 

reduce cold start friction. However, in some cases, changes to the crankshaft, rod and 

main bearings and changes to the mechanical tolerances of engine components may be 

required. In all cases, durability testing would be required to ensure that durability is not 

compromised. The shift to lower viscosity and lower friction lubricants will also improve 

the effectiveness of valvetrain technologies such as cylinder deactivation, which rely on a 

minimum oil temperature (viscosity) for operation.

Based on the 2012-2016 light-duty final rule, and previously-received confidential 

manufacturer data, NHTSA and EPA estimated the effectiveness of low friction 

lubricants to be between 0 to 1 percent. 

In the 2012-2016 light-duty final rule, the agencies estimated the cost of moving 

to low friction lubricants at $3 per vehicle (2007$). That estimate included a markup of 

1.11 for a low complexity technology. For class 2b and 3, we are using the same base 

estimate but have marked it up to 2008 dollars using the GDP price deflator and have 

used a markup of 1.17 for a low complexity technology to arrive at a value of $4 per 

vehicle. As in the light-duty rule, learning effects are not applied to costs for this 

technology and, as such, this estimate applies to all model years.142,143

(ii) Engine Friction Reduction (EFR)

In addition to low friction lubricants, manufacturers can also reduce friction and 

improve fuel consumption by improving the design of both diesel and gasoline engine 

components and subsystems. Approximately 10 percent of the energy consumed by a 

vehicle is lost to friction, and just over half is due to frictional losses within the engine.144 

 

142 Note that throughout the cost estimates for this HD analysis, the agencies have used slightly higher 

markups than those used in the 2010-2016 light-duty FRM. The new, slightly higher ICMs include return 

on capital of roughly 6%, a factor that was not included in the light-duty analysis. 

143

 Note that the costs developed for low friction lubes for this analysis reflect the costs associated with any 

engine changes that would be required as well as any durability testing that may be required. 

144 “Impact of Friction Reduction Technologies on Fuel Economy,” Fenske, G. Presented at the March 

2009 Chicago Chapter Meeting of the ‘Society of Tribologists and Lubricated Engineers’ Meeting, March 

18th, 2009. Available at: http://www.chicagostle.org/program/2008-

2009/Impact%20of%20Friction%20Reduction%20Technologies%20on%20Fuel%20Economy%20-

%20with%20VGs%20removed.pdf (last accessed July 9, 2009).
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Examples include improvements in low-tension piston rings, piston skirt design, roller 

cam followers, improved crankshaft design and bearings, material coatings, material 

substitution, more optimal thermal management, and piston and cylinder surface 

treatments. Additionally, as computer-aided modeling software continues to improve, 

more opportunities for evolutionary friction reductions may become available.

All reciprocating and rotating components in the engine are potential candidates 

for friction reduction, and minute improvements in several components can add up to a 

measurable fuel economy improvement. The 2012- light-duty final rule, the March 2010 

NAS Report, and, NESCCAF and EEA reports as well as confidential manufacturer data 

suggested a range of effectiveness for engine friction reduction to be between 1 to 3 

percent. NHTSA and EPA continue to believe that this range is accurate.

Consistent with the 2012-2016 light-duty final rule, the agencies estimate the cost 

of this technology at $14 per cylinder compliance cost (2008$), including the low 

complexity ICM markup value of 1.17. Learning impacts are not applied to the costs of 

this technology and, as such, this estimate applies to all model years. This cost is 

multiplied by the number of engine cylinders.

(iii) Coupled Cam Phasing (CCP)

Valvetrains with coupled (or coordinated) cam phasing can modify the timing of 

both the inlet valves and the exhaust valves an equal amount by phasing the camshaft of 

an overhead valve (OHV) engine.145 For overhead valve (OHV) engines, which have 

only one camshaft to actuate both inlet and exhaust valves, CCP is the only VVT 

implementation option available and requires only one cam phaser.146

Based on the 2012-2016 light-duty final rule, previously-received confidential 

manufacturer data, and the NESCCAF report, NHTSA and EPA estimated the 

effectiveness of CCP to be between 1 to 4 percent. NHTSA and EPA reviewed this 

estimate for purposes of the NPRM, and continue to find it accurate.

In the 2012-2016 Light-duty final rule, the agencies estimated a $41 cost per cam 

phaser not including any markup (2007$). NHTSA and EPA believe that this estimate 

remains accurate. Using the new indirect cost multiplier of 1.17, for a low complexity

technology, the compliance cost per cam phaser would be $46 (2008$) in the 2014 model 

year. Time-based learning is applied to this technology. This technology was considered 

for gasoline engines only. 

 

145 Although CCP appears only in the SOHC and OHV branches of the decision tree, it is noted that a 

single phaser with a secondary chain drive would allow CCP to be applied to DOHC engines. Since this 

would potentially be adopted on a limited number of DOHC engines NHTSA did not include it in that 

branch of the decision tree.

146 It is also noted that coaxial camshaft developments would allow other VVT options to be applied to 

OHV engines. However, since they would potentially be adopted on a limited number of OHV engines 

NHTSA did not include them in the decision tree.
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(iv) Cylinder Deactivation (DEAC)

In conventional spark-ignited engines throttling the airflow controls engine torque 

output. At partial loads, efficiency can be improved by using cylinder deactivation 

instead of throttling. Cylinder deactivation (DEAC) can improve engine efficiency by

disabling or deactivating (usually) half of the cylinders when the load is less than half of 

the engine’s total torque capability – the valves are kept closed, and no fuel is injected –

as a result, the trapped air within the deactivated cylinders is simply compressed and 

expanded as an air spring, with reduced friction and heat losses. The active cylinders 

combust at almost double the load required if all of the cylinders were operating. 

Pumping losses are significantly reduced as long as the engine is operated in this “partcylinder” mode.

Cylinder deactivation control strategy relies on setting maximum manifold 

absolute pressures or predicted torque within which it can deactivate the cylinders. Noise 

and vibration issues reduce the operating range to which cylinder deactivation is allowed, 

although manufacturers are exploring vehicle changes that enable increasing the amount 

of time that cylinder deactivation might be suitable. Some manufacturers may choose to 

adopt active engine mounts and/or active noise cancellations systems to address NVH 

concerns and to allow a greater operating range of activation. 

Cylinder deactivation has seen a recent resurgence thanks to better valvetrain 

designs and engine controls. General Motors and Chrysler Group have incorporated 

cylinder deactivation across a substantial portion of their V8-powered lineups.

Effectiveness improvements scale roughly with engine displacement-to-vehicle 

weight ratio: the higher displacement-to-weight vehicles, operating at lower relative loads 

for normal driving, have the potential to operate in part-cylinder mode more frequently.

NHTSA and EPA adjusted the 2012-2016 light-duty final rule estimates using 

updated power to weight ratings of heavy-duty trucks and confidential business 

information and confirmed a range of 3 to 4 percent for these vehicles.

NHTSA and EPA consider the costs for this technology to be identical to that for 

V8 engines on light-duty trucks. As such, the agencies have used the cost used in the 

2012-2016 light-duty final rule. Using the new markup of 1.17 for a low complexity

technology results in an estimate of $193 (2008$) in the 2014 model year Time based 

learning is applied to this technology. This technology was considered for gasoline 

engines only.

(v) Stoichiometric Gasoline Direct Injection (SGDI)

Stoichiometric gasoline direct injection (SGDI) engines inject fuel at high 

pressure directly into the combustion chamber (rather than the intake port in port fuel 

injection). SGDI requires changes to the injector design, an additional high pressure fuel 

pump, new fuel rails to handle the higher fuel pressures and changes to the cylinder head 

and piston crown design. Direct injection of the fuel into the cylinder improves cooling 

of the air/fuel charge within the cylinder, which allows for higher compression ratios and 
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increased thermodynamic efficiency without the onset of combustion knock. Recent 

injector design advances, improved electronic engine management systems and the 

introduction of multiple injection events per cylinder firing cycle promote better mixing 

of the air and fuel, enhance combustion rates, increase residual exhaust gas tolerance and 

improve cold start emissions. SGDI engines achieve higher power density and match 

well with other technologies, such as boosting and variable valvetrain designs.

Several manufacturers have recently introduced vehicles with SGDI engines, 

including GM and Ford and have announced their plans to increase dramatically the 

number of SGDI engines in their portfolios.

The 2012-2016 light-duty final rule estimated the range of 1 to 2 percent for 

SGDI. NHTSA and EPA reviewed this estimate for purposes of the NPRM, and continue 

to find it accurate. 

Consistent with the 2012-2016 light-duty final rule, NHTSA and EPA cost 

estimates for SGDI take into account the changes required to the engine hardware, engine 

electronic controls, ancillary and Noise Vibration and Harshness (NVH) mitigation 

systems. Through contacts with industry NVH suppliers, and manufacturer press 

releases, the agencies believe that the NVH treatments will be limited to the mitigation of 

fuel system noise, specifically from the injectors and the fuel lines. For this analysis, the 

agencies have estimated the costs at $395 (2008$) in the 2014 model year. Time based 

learning is applied to this technology. This technology was considered for gasoline 

engines only, as diesel engines already employ direct injection.

(b) Diesel Engine Technologies 

Diesel engines have several characteristics that give them superior fuel efficiency 

compared to conventional gasoline, spark-ignited engines. Pumping losses are much 

lower due to lack of (or greatly reduced) throttling. The diesel combustion cycle operates 

at a higher compression ratio, with a very lean air/fuel mixture, and turbocharged lightduty diesels typically achieve much higher torque levels at lower engine speeds than 

equivalent-displacement naturally-aspirated gasoline engines. Additionally, diesel fuel 

has a higher energy content per gallon.147 However, diesel fuel also has a higher carbon 

to hydrogen ratio, which increases the amount of CO2 emitted per gallon of fuel used by 

approximately 15 percent over a gallon of gasoline.

Based on confidential business information and the March 2010 NAS Report, two 

major areas of Diesel engine design will be improved during the 2014-2018 timeframe. 

These areas include aftertreatment improvements and a broad range of engine 

improvements.

 

147 Burning one gallon of diesel fuel produces about 15 percent more carbon dioxide than gasoline due to 

the higher density and carbon to hydrogen ratio.
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(i) Aftertreatment Improvements

Based on confidential product plans and published information, all vehicles in the 

class 2b and 3 class will be moving (or have already moved) to the SCR type of 

aftertreatment system. As the experience base for SCR expands over the next few years, 

many improvements in this aftertreatment system such as construction of the catalyst, 

thermal management, and reductant optimization will result in a significant reduction in 

the amount of fuel used in the process. This technology was not considered in the 2012-

2016 Light-duty final rule. Based on confidential business information, EPA and 

NHTSA estimate the reduction in CO2 as a result of these improvements at 4%.

The agencies have estimated the cost of this technology at $25 for each 

percentage improvement in fuel consumption. This estimate is based on the agencies’ 

belief that this technology is, in fact, a very cost effective approach to improving fuel 

consumption. As such, $25 per percent improvement is considered a reasonable cost. 

This cost would cover the engineering and test cell related costs necessary to develop and 

implement the improved control strategies that would allow for the improvements in fuel 

consumption. Importantly, the engineering work involved would be expected to result in 

cost savings to the aftertreatment and control hardware (lower platinum group metal 

(PGM) loadings, lower reductant dosing rates, etc.). Those savings are considered to be 

included in the $25 per percent estimate described here. Given the 4% expected 

improvement in fuel consumption results in an estimated cost of $110 (2008$) for a 2014 

model year truck or van. This estimate includes a low complexity ICM of 1.17 and time 

based learning from 2012 forward.

(ii) Engine Improvements

Diesel engines in the Class 2b and 3 segment are expected to have several 

improvements in their base design in the 2014 – 2018 timeframe. These improvements 

include items such as improved combustion management, optimal turbocharger design, 

and improved thermal management. This technology was not considered in the 2012-

2016 light-duty final rule. Based on confidential business information, EPA and NHTSA 

estimate the reduction in CO2 as a result of these improvements at 5%.

The cost for this technology includes costs associated with low temperature 

exhaust gas recirculation and improved turbochargers. These costs are considered 

collectively in our costing analysis and termed “diesel engine improvements.” The 

agencies have estimated the cost of diesel engine improvements based on the TIAX 

report which estimated the retail price equivalent at $500 using a 2 times multiplier. 

Dividing that value gives a direct manufacturing cost of $250. Applying a low 

complexity ICM and time based learning from 2012 forward results in the agencies’ 

estimate of $275 (2008$) in the 2014 model year.

(c) Transmission Technologies 

NHTSA and EPA have also reviewed the transmission technology estimates used 

in the 2012-2016 light-duty final rule. In doing so, NHTSA and EPA considered or 
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reconsidered all available sources and updated the estimates as appropriate. The section 

below describes each of the transmission technologies considered for this proposal.

(i) Improved Automatic Transmission Control (IATC) (Aggressive Shift Logic and 

Early Torque Converter Lockup)

Calibrating the transmission shift schedule to upshift earlier and quicker, and to 

lock-up or partially lock-up the torque converter under a broader range of operating 

conditions can reduce fuel consumption and CO2 emissions. However, this operation can 

result in a perceptible degradation in NVH. The degree to which NVH can be degraded 

before it becomes noticeable to the driver is strongly influenced by characteristics of the 

vehicle, and although it is somewhat subjective, it always places a limit on how much 

fuel consumption can be improved by transmission control changes. Given that the 

Aggressive Shift Logic and Early Torque Converter Lockup are best optimized 

simultaneously due to the fact that adding both of them primarily requires only minor 

modifications to the transmission or calibration software, these two technologies are 

combined in the modeling. We consider these technologies to be present in the baseline, 

6-speed automatic transmissions in the majority of class 2b and 3 trucks in the 2010 

model year timeframe.

(ii) Automatic 6- and 8-Speed Transmissions (NAUTO)

Manufacturers can also choose to replace 4- 5- and 6-speed automatic

transmissions with 8-speed automatic transmissions. Additional ratios allow for further 

optimization of engine operation over a wider range of conditions, but this is subject to 

diminishing returns as the number of speeds increases. As additional planetary gear sets 

are added (which may be necessary in some cases to achieve the higher number of ratios), 

additional weight and friction are introduced. Also, the additional shifting of such a 

transmission can be perceived as bothersome to some consumers, so manufacturers need 

to develop strategies for smooth shifts. Some manufacturers are replacing 4- and 5-speed 

automatics with 6-speed automatics already, and 7- and 8-speed automatics have entered 

production in light-duty vehicles, albeit in lower-volume applications in luxury and 

performance oriented cars.

As discussed in the 2010 light-duty final rule, confidential manufacturer data 

projected that 6-speed transmissions could incrementally reduce fuel consumption by 0 to 

5 percent from a 4-speed automatic transmission, while an 8-speed transmission could 

incrementally reduce fuel consumption by up to 6 percent from a 4-speed automatic 

transmission. GM has publicly claimed a fuel economy improvement of up to 4 percent 

for its new 6-speed automatic transmissions.148 

 

148 General Motors, news release, “From Hybrids to Six-Speeds, Direct Injection And More, GM’s 2008 

Global Powertrain Lineup Provides More Miles with Less Fuel” (released Mar. 6, 2007). Available at 

http://www.gm.com/experience/fuel_economy/news/2007/adv_engines/2008-powertrain-lineup-082707.jsp 

(last accessed Sept. 18, 2008).
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NHTSA and EPA reviewed and revised these effectiveness estimates based on 

actual usage statistics and testing methods for these vehicles along with confidential 

business information. When combined with IATC, the agencies estimate the 

effectiveness for a conversion from a 4 to a 6-speed transmission to be 5.3% and a 

conversion from a 6 to 8-speed transmission to be 1.7%. While 8-speed transmissions 

were not considered in the 2012-2016 Light-duty final rule, they are considered as a 

technology of choice for this analysis in that manufacturers are expected to upgrade the 

6-speed automatic transmissions being implemented today with 8-speed automatic 

transmissions in the 2014-2018 timeframe. For this proposal, we are estimating the cost 

of an 8-speed automatic transmission at $231 (2008$) relative to a 6-speed automatic 

transmission in the 2014 model year. This estimate is based from the March 2010 NAS 

Report and we have applied a low complexity ICM of 1.17 and time based learning. This 

technology applies to both gasoline and diesel trucks and vans.

(d) Electrification/Accessory Technologies

(i) Electrical Power Steering (EPS) or Electrohydraulic Power Steering (EHPS)

Electric power steering (EPS) or Electrohydraulic power steering (EHPS) 

provides a potential reduction in CO2 emissions and fuel consumption over hydraulic 

power steering because of reduced overall accessory loads. This eliminates the parasitic 

losses associated with belt-driven power steering pumps which consistently draw load 

from the engine to pump hydraulic fluid through the steering actuation systems even 

when the wheels are not being turned. EPS is an enabler for all vehicle hybridization 

technologies since it provides power steering when the engine is off. EPS may be 

implemented on most vehicles with a standard 12V system. Some heavier vehicles may

require a higher voltage system which may add cost and complexity.

The 2012012-2016 light-duty final rule estimated a 1 to 2 percent effectiveness 

based on the 2002 NAS report for light-duty vehicle technologies, a Sierra Research 

report, and confidential manufacturer data. NHTSA and EPA reviewed these 

effectiveness estimates and found them to be accurate, thus they have been retained for 

purposes of this NPRM.

NHTSA and EPA adjusted the EPS cost for the current rulemaking based on a 

review of the specification of the system. Adjustments were made to include potentially

higher voltage or heavier duty system operation for class 2b and 3. Accordingly, higher 

costs were estimated for systems with higher capability. After accounting for the 

differences in system capability and applying the ICM markup of low complexity

technology of 1.17, the estimated costs for this proposal are $108 for a MY 2014 truck or 

van (2008$). As EPS systems are in widespread usage today, time-based learning is 

deemed applicable. EHPS systems are considered to be of equal cost and both are 

considered applicable to gasoline and diesel engines.
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(ii) Improved Accessories (IACC)

The accessories on an engine, including the alternator, coolant and oil pumps are 

traditionally mechanically-driven. A reduction in CO2 emissions and fuel consumption 

can be realized by driving them electrically, and only when needed (“on-demand”). 

Electric water pumps and electric fans can provide better control of engine 

cooling. For example, coolant flow from an electric water pump can be reduced and the 

radiator fan can be shut off during engine warm-up or cold ambient temperature 

conditions which will reduce warm-up time, reduce warm-up fuel enrichment, and reduce 

parasitic losses.

Indirect benefit may be obtained by reducing the flow from the water pump 

electrically during the engine warm-up period, allowing the engine to heat more rapidly 

and thereby reducing the fuel enrichment needed during cold starting of the engine. 

Further benefit may be obtained when electrification is combined with an improved, 

higher efficiency engine alternator. Intelligent cooling can more easily be applied to 

vehicles that do not typically carry heavy payloads, so larger vehicles with towing 

capacity present a challenge, as these vehicles have high cooling fan loads.149

The agencies considered whether to include electric oil pump technology for the 

rulemaking. Because it is necessary to operate the oil pump any time the engine is 

running, electric oil pump technology has insignificant effect on efficiency. Therefore, 

the agencies decided to not include electric oil pump technology for this proposal.

NHTSA and EPA jointly reviewed the estimates of 1 to 2 percent effectiveness 

estimates used in the 2012-2016 light-duty final rule and found them to be accurate for 

Improved Electrical Accessories. Consistent with the 2012-2016 light-duty final rule, the 

agencies have estimated the cost of this technology at $88 (2008$) including a low 

complexity ICM of 1.17. This cost is applicable in the 2014 model year. Improved 

accessory systems are in production currently and thus time-based learning is applied. 

This technology was considered for diesel trucks and vans only.

(e) Vehicle Technologies

(i) Mass Reduction

Reducing a vehicle’s mass, or down-weighting the vehicle, decreases fuel 

consumption by reducing the energy demand needed to overcome forces resisting motion, 

and rolling resistance. Manufacturers employ a systematic approach to mass reduction, 

where the net mass reduction is the addition of a direct component or system mass 

reduction plus the additional mass reduction taken from indirect ancillary systems and 

components, as a result of full vehicle optimization, effectively compounding or 

 

149 In the CAFE model, IACC refers solely to improved engine cooling. However, EPA has included a 

high efficiency alternator in this category, as well as improvements to the cooling system.
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obtaining a secondary mass reduction from a primary mass reduction. For example, use 

of a smaller, lighter engine with lower torque-output subsequently allows the use of a 

smaller, lighter-weight transmission and drive line components. Likewise, the 

compounded weight reductions of the body, engine and drivetrain reduce stresses on the 

suspension components, steering components, wheels, tires and brakes, allowing further 

reductions in the mass of these subsystems. The reductions in unsprung masses such as 

brakes, control arms, wheels and tires further reduce stresses in the suspension mounting 

points. This produces a compounding effect of mass reductions.

Estimates of the synergistic effects of mass reduction and the compounding effect 

that occurs along with it can vary significantly from one report to another. For example, 

in discussing its estimate, an Auto-Steel Partnership report states that “These secondary

mass changes can be considerable—estimated at an additional 0.7 to 1.8 times the initial 

mass change.”150 This means for each one pound reduction in a primary component, up to 

1.8 pounds can be reduced from other structures in the vehicle (i.e., a 180 percent factor). 

The report also discusses that a primary variable in the realized secondary weight 

reduction is whether or not the powertrain components can be included in the mass 

reduction effort, with the lower end estimates being applicable when powertrain elements 

are unavailable for mass reduction. However, another report by the Aluminum 

Association, which primarily focuses on the use of aluminum as an alternative material 

for steel, estimated a factor of 64 percent for secondary mass reduction even though some 

powertrain elements were considered in the analysis.151 That report also notes that 

typical values for this factor vary from 50 to 100 percent. Although there is a wide 

variation in stated estimates, synergistic mass reductions do exist, and the effects result in 

tangible mass reductions. Mass reductions in a single vehicle component, for example a 

door side impact/intrusion system, may actually result in a significantly higher weight 

savings in the total vehicle, depending on how well the manufacturer integrates the 

modification into the overall vehicle design. Accordingly, care must be taken when 

reviewing reports on weight reduction methods and practices to ascertain if compounding 

effects have been considered or not.

Mass reduction is broadly applicable across all vehicle subsystems including the 

engine, exhaust system, transmission, chassis, suspension, brakes, body, closure panels, 

glazing, seats and other interior components, engine cooling systems and HVAC systems. 

It is estimated that up to 1.25 kilograms of secondary weight savings can be achieved for 

 

150 “Preliminary Vehicle Mass Estimation Using Empirical Subsystem Influence Coefficients,” Malen, 

D.E., Reddy, K. Auto-Steel Partnership Report, May 2007, Docket EPA-HQ-OAR-2009-0472-0169. 

Accessed on the Internet on May 30, 2009 at: http://www.asp.org/database/custom/Mass%20Compounding%20-%20Final%20Report.pdf

151

 “Benefit Analysis: Use of Aluminum Structures in Conjunction with Alternative Powertrain 

Technologies in Automobiles,” Bull, M. Chavali, R., Mascarin, A., Aluminum Association Research 

Report, May 2008, Docket EPA-HQ-OAR-2009-0472-0168. Accessed on the Internet on April 30, 2009 

at: http://www.autoaluminum.org/downloads/IBIS-Powertrain-Study.pdf
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every kilogram of weight saved on a vehicle when all subsystems are redesigned to take 

into account the initial primary weight savings.152,153 

Mass reduction can be accomplished by proven methods such as:

 Smart Design: Computer aided engineering (CAE) tools can be used to better 

optimize load paths within structures by reducing stresses and bending moments 

applied to structures. This allows better optimization of the sectional thicknesses 

of structural components to reduce mass while maintaining or improving the 

function of the component. Smart designs also integrate separate parts in a 

manner that reduces mass by combining functions or the reduced use of separate 

fasteners. In addition, some “body on frame” vehicles are redesigned with a 

lighter “unibody” construction. 

 Material Substitution: Substitution of lower density and/or higher strength 

materials into a design in a manner that preserves or improves the function of the 

component. This includes substitution of high-strength steels, aluminum, 

magnesium or composite materials for components currently fabricated from mild 

steel. 

 Reduced Powertrain Requirements: Reducing vehicle weight sufficiently allows 

for the use of a smaller, lighter and more efficient engine while maintaining or 

increasing performance. Approximately half of the reduction is due to these 

reduced powertrain output requirements from reduced engine power output and/or 

displacement, changes to transmission and final drive gear ratios. The subsequent 

reduced rotating mass (e.g., transmission, driveshafts/halfshafts, wheels and tires) 

via weight and/or size reduction of components are made possible by reduced 

torque output requirements.

 Automotive companies have largely used weight savings in some vehicle 

subsystems to offset or mitigate weight gains in other subsystems from increased 

feature content (sound insulation, entertainment systems, improved climate 

control, panoramic roof, etc.). 

 Lightweight designs have also been used to improve vehicle performance 

parameters by increased acceleration performance or superior vehicle handling 

and braking.

 

152 “Future Generation Passenger Compartment-Validation (ASP 241)” Villano, P.J., Shaw, J.R., 

Polewarczyk, J., Morgans, S., Carpenter, J.A., Yocum, A.D., in “Lightweighting Materials – FY 2008 

Progress Report,” U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Vehicle 

Technologies Program, May 2009, Docket EPA-HQ-OAR-2009-0472-0190.

153 “Preliminary Vehicle Mass Estimation Using Empirical Subsystem Influence Coefficients,” Malen, 

D.E., Reddy, K. Auto-Steel Partnership Report, May 2007, Docket EPA-HQ-OAR-2009-0472-0169. 

Accessed on the Internet on May 30, 2009 at: http://www.asp.org/database/custom/Mass%20Compounding%20-%20Final%20Report.pdf
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Many manufacturers have already announced proposed future products plans 

reducing the weight of a vehicle body through the use of high strength steel body-inwhite, composite body panels, magnesium alloy front and rear energy absorbing 

structures reducing vehicle weight sufficiently to allow a smaller, lighter and more 

efficient engine. Nissan will be reducing average vehicle curb weight by 15% by

2015.154 Ford has identified weight reductions of 250 to 750 lbs per vehicle as part of its 

implementation of known technology within its sustainability strategy between 2011 and 

2020.155 Mazda plans to reduce vehicle weight by 220 pounds per vehicle or more as 

models are redesigned.156,157 Ducker International estimates that the average curb weight 

of light-duty vehicle fleet will decrease approximately 2.8% from 2009 to 2015 and 

approximately 6.5% from 2009 to 2020 via changes in automotive materials and 

increased change-over from previously used body-on-frame automobile and light-truck 

designs to newer unibody designs.154 While the opportunity for mass reductions available 

to the light-duty fleet may not in all cases be applied directly to the heavy-duty fleet due 

to the different designs for the expected duty cycles of a “work” vehicle, mass reductions 

are still available particularly to areas unrelated to the components necessary for the work 

vehicle aspects. 

Due to the payload and towing requirements of these heavy-duty vehicles, engine 

downsizing was not considered in the estimates for CO2 reduction in the area of mass 

reduction/material substitution. NHTSA and EPA estimate that a 3 percent mass 

reduction with no engine downsizing results in a 1 percent reduction in fuel consumption. 

In addition, a 5 and 10 percent mass reduction with no engine downsizing result in an 

estimated CO2 reduction of 1.6 and 3.2 percent respectively. These effectiveness values 

are 50% of the 2012-2016 Light-duty final rule values due to the elimination of engine 

downsizing for this class of vehicle.

Consistent with the 2012-2016 light-duty final rule, the agencies have estimated 

the cost of mass reduction at $1.32 per pound (2008$). For this analysis, the agencies are 

estimating a 5% mass reduction or, given the baseline weight of current trucks and vans, 

are estimating costs of $462, $544, $513, and $576 for Class 2b gasoline, 2b diesel, 3 

gasoline, 3 diesel trucks and vans, respectively. All values are in 2008 dollars, are 

applicable in the 2014 model year and include a low complexity ICM of 1.17. Time 

based learning is considered applicable to mass reduction technologies. 

 

154 “Lighten Up!,” Brooke, L., Evans, H. Automive Engineering International, Vol. 117, No. 3, March 

2009.

155 “2008/9 Blueprint for Sustainability,” Ford Motor Company. Available at: http:// 

www.ford.com/go/sustainability (last accessed February 8, 2010).

156 “Mazda to cut vehicle fuel consumption 30 percent by 2015,” Mazda press release, June 23, 2009. 

Available at: http://www.mazda.com/publicity/release/2008/200806/080623.html (last accessed February 

8, 2010).

157 “Mazda: Don’t believe hot air being emitted by hybrid hype,” Greimel, H. Automotive News, March 30, 

2009.
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(ii) Low Rolling Resistance Tires (ROLL)

Tire rolling resistance is the frictional loss associated mainly with the energy

dissipated in the deformation of the tires under load and thus influences fuel economy

and CO2 emissions. Other tire design characteristics (e.g., materials, construction, and 

tread design) influence durability, traction (both wet and dry grip), vehicle handling, and 

ride comfort in addition to rolling resistance. A typical low rolling resistance tire’s 

attributes would include: increased tire inflation pressure, material changes, and tire 

construction with less hysteresis, geometry changes (e.g., reduced aspect ratios), and 

reduction in sidewall and tread deflection. These changes would generally be 

accompanied with additional changes to suspension tuning and/or suspension design.

EPA and NHTSA estimated a 1 to 2 percent increase in effectiveness with a 10 

percent reduction in rolling resistance, which was based on the March 2010 NAS Report 

findings and consistent with the 2012-2016 Light-duty final rule. 

Based on the 2012-2016 light-duty final rule and the March 2010 NAS Report, 

the agencies have estimated the cost for low rolling resistance tires to be $6 per Class 2b 

truck or van, and $9 per Class 3 truck or van.158 The higher cost for the Class 3 trucks 

and vans is due to the predominant use of dual rear tires and, thus, 6 tires per truck. Due 

to the commodity-based nature of this technology, cost learning is not applied. This 

technology is consider applicable to both gasoline and diesel.

(iii) Aerodynamic Drag Reduction (AERO)

Many factors affect a vehicle’s aerodynamic drag and the resulting power 

required to move it through the air. While these factors change with air density and the 

square and cube of vehicle speed, respectively, the overall drag effect is determined by 

the product of its frontal area and drag coefficient. Reductions in these quantities can 

therefore reduce fuel consumption and CO2 emissions. Although frontal areas tend to be 

relatively similar within a vehicle class (mostly due to market-competitive size 

requirements), significant variations in drag coefficient can be observed. Significant 

changes to a vehicle’s aerodynamic performance may need to be implemented during a 

redesign (e.g., changes in vehicle shape). However, shorter-term aerodynamic 

reductions, with a somewhat lower effectiveness, may be achieved through the use of

revised exterior components (typically at a model refresh in mid-cycle) and add-on 

devices that currently being applied. The latter list would include revised front and rear 

fascias, modified front air dams and rear valances, addition of rear deck lips and 

underbody panels, and lower aerodynamic drag exterior mirrors.

The 2012-2016 light-duty final rule estimated that a fleet average of 10 to 20 

percent total aerodynamic drag reduction is attainable which equates to incremental 

reductions in fuel consumption and CO2 emissions of 2 to 3 percent for both cars and 

 

158 “Tires and Passenger Vehicle Fuel Economy,” Transportation Research Board Special Report 286, 

National Research Council of the National Academies, 2006, Docket EPA-HQ-OAR-2009-0472-0146.
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trucks. These numbers are generally supported by confidential manufacturer data and 

public technical literature. For the heavy-duty truck category, a 5 to 10 percent total 

aerodynamic drag reduction was considered due to the different structure and use of these 

vehicles equating to incremental reductions in fuel consumption and CO2 emissions of 1 

to 2 percent.

Consistent with the 2012-2016 light-duty final rule, the agencies have estimated 

the cost for this technology at $54 (2008$) including a low complexity ICM of 1.17. This 

cost is applicable in the 2014 model year to both gasoline and diesel trucks and vans.

(3) What are the projected technology package effectiveness and cost?

The assessment of the proposed technology effectiveness was developed through 

the use of the EPA Lumped Parameter model developed for the light duty rule. Many of 

the technologies were common with the light duty assessment but the effectiveness of 

individual technologies was appropriately adjusted to match the expected effectiveness 

when implemented in a heavy duty application. The model then uses the individual 

technology effectiveness levels but then takes into account technology synergies. The 

model is also designed to prevent double counting from technologies that may directly or 

indirectly impact the same physical attribute (e.g., pumping loss reductions). 

To achieve the levels of the proposed standards for gasoline and diesel powered 

heavy duty vehicles, the technologies packages were determined to generally require the 

full list of feasible technologies previously discussed respective to unique gasoline and 

diesel technologies. Some of the technologies may already be implemented in select 

heavy duty vehicles however none of the technologies discussed are considered 

ubiquitous in the heavy duty fleet. Further, many technologies can be further improved 

(e.g., aerodynamic improvements) from today’s levels. 
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Table III-11: Technology Costs Inclusive of Indirect Costs Markups for the 2014 MY (2008$)

Technology Class 2b 

Gasoline

Class 2b 

Diesel

Class 3 

Gasoline

Class 3 

Diesel

Low friction lubes $4 $4 $4 $4

Engine friction reduction $108 N/A $108 N/A

Coupled cam phasing $46 N/A $46 N/A

Cylinder deactivation $193 N/A $193 N/A

Stoichiometric gasoline direct 

injection

$395 N/A $395 N/A

Engine improvements N/A $275 N/A $275

8s automatic transmission 

(increment to 6s automatic 

transmission)

$231 $231 $231 $231

Improved accessories N/A $88 N/A $88

Low rolling resistance tires $6 $6 $9 $9

Aerodynamic improvements $54 $54 $54 $54

Electric (or electro/hydraulic) 

power steering

$108 $108 $108 $108

Aftertreatment improvements N/A $110 N/A $110

Mass reduction (5%) $462 $544 $513 $576

Air conditioning $21 $21 $21 $21

Total $1,628 $1,441 $1,679 $1,473

At 15% phase-in in 2014 $244 $216 $252 $221

C. Class 2b-8 Vocational Vehicles

Vocational vehicles cover a wide variety of applications which influence both the 

body style and usage patterns. They also are built using a complex process, which 

includes additional parties such as body builders. These factors have led the agencies to 

propose a vehicle standard for vocational trucks for the first phase of the program that 

relies on less extensive addition of technology as well as focusing on the chassis 

manufacturer as the manufacturer subject to the standard. We believe that future 

rulemakings will consider increased stringency and possibly more application-specific 

standards. The agencies are proposing standards for the diesel and gasoline engines used 

in vocational vehicles, similar to those discussed above for class 7/8 tractors. 

(1) What technologies did the agencies consider to reduce the CO2 emissions 

and fuel consumption of vocational trucks?

Similar to the approach taken with tractors, the agencies evaluated aerodynamic, 

tire, idle reduction, weight reduction, hybrid powertrain, and engine technologies and 

their impact on reducing fuel consumption and GHG emissions. The engines used in 

vocational trucks include both gasoline and diesel engines, thus, each type is discussed 

separately below. As explained in section II.D.1.b, the proposed regulatory structure for 

heavy-duty engines separates the compression ignition (or “diesel”) engines into three 

regulatory classes - light heavy, medium heavy, and heavy heavy diesel engines -- while 
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spark ignition (or “gasoline”) engines are a single regulatory class. Therefore, the 

subsequent discussion will assess each type of engine separately.

(a) Truck Technologies

Vocational trucks typically travel fewer miles than combination tractors. They 

also tend to be used in more urban locations (with consequent stop and start drive cycles). 

Therefore the average speed of vocational trucks is significantly lower than tractors. . 

This has a significant effect on the types of technologies that are appropriate to consider 

for reducing CO2 emissions and fuel consumption. 

The agencies considered the type of technologies for vocational trucks based on

the energy losses of a typical vocational vehicle. The technologies are similar to the ones 

considered for tractors. Argonne National Lab conducted an energy audit using 

simulation tools to evaluate the energy losses of vocational trucks, such as a Class 6 pick 

up and delivery truck. Argonne found that 74 percent of the energy losses are attributed 

to the engine, 13 percent to tires, 9 percent to aerodynamics, 2 percent to transmission 

losses, and the remaining 4 percent of losses to axles and accessories for a medium duty

truck traveling at 30 mph.159 

Low Rolling Resistance Tires: Tires are the second largest contributor to energy

losses of vocational vehicles, as found in the energy audit conducted by Argonne 

National Lab. The range of rolling resistance of tires used on vocational trucks today is 

large. This is in part due to the fact that the competitive pressure to improve rolling 

resistance of vocational truck tires has been less than that found in the line haul tire 

market. In addition, the drive cycles typical for these applications often lead truck buyers 

to value tire traction and durability more heavily than rolling resistance. Therefore, the 

agencies concluded that a regulatory program that seeks to optimize tire rolling resistance 

in addition to traction and durability can bring about fuel consumption and CO2 emission 

reductions from this segment. The NAS report states that rolling resistance impact on 

fuel consumption reduces with mass of the vehicle and with drive cycles with more 

frequent starts and stops. The report found that the fuel consumption reduction 

opportunity for reduced rolling resistance ranged between 1 and 3 percent in the 2010 

through 2020 timeframe. The agencies estimate that average rolling resistance from tires 

in 2010 model year can be reduced by 10 percent by 2014 model year based on the tire 

development achievements over the last several years in the line haul truck market which 

would lead to a 2 percent reduction in fuel consumption based on [TEST].

Aerodynamics: As shown above, aerodynamics have less of an impact on 

vocational truck energy losses than engines or tires. In addition, the aerodynamic 

performance of a complete vehicle is significantly influenced by the body of the truck. 

The agencies are not proposing to regulate body builders in this phase of regulations for 

the reasons discussed in Section II. Therefore, we are not basing any of the proposed 

 

159 Argonne National Lab. Evaluation of Fuel Consumption Potential of Medium and Heavy-duty Vehicles 

through Modeling and Simulation. October 2009. Page 89.
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standards for vocational trucks on aerodynamic improvements. Nor would aerodynamic 

performance be input into the TEST model to demonstrate compliance. 

Weight Reduction: NHTSA and EPA are also not basing any of the proposed 

standards on use of vehicle weight reduction. Thus, vehicle mass reductions would not 

be input into the [TEST] model. The vocational truck models are not designed to be 

application-specific. Therefore weight reductions are difficult to quantify. 

Drivetrain: The agencies recognize that approximately 6 percent of the total 

vehicle losses are attributed to the axles, accessories, and transmission. The NAS report 

found that the opportunities to reduce fuel consumption in vocational vehicles due to 

transmission and driveline technologies in the 2015 timeframe ranged between 1.2 and 2 

percent. The agencies welcome comment on transmission and driveline technologies 

specific to the vocational vehicle market that can achieve fuel consumption and GHG 

emissions reductions.

Idle Reduction: Episodic idling by vocational trucks occurs during the workday, 

unlike the overnight idling of line haul combination trucks. Vocational truck idling can 

be divided into two typical types. The first type is idling while waiting – such as during a 

pickup or delivery. This type of idling can be reduced through automatic engine shutoffs. The second type of idling is to accomplish power take off operation (PTO), such as 

compacting garbage or operating a bucket. The agencies have found only one study that 

quantifies the emissions due to idling conducted by Argonne National Lab based on 2002 

VIUS data.160 EPA conducted a work assignment to assist in characterizing PTO 

operations. The study of a utility truck used in two different environments (rural and 

urban) and a refuse hauler found that the PTO operated on average 28 percent of time 

relative to the total time spent driving and idling. The use of hybrid powertrains to 

reduce idling is discussed below.

Hybrid Powertrains: Several types of vocational vehicles are well suited for 

hybrid powertrains. Vehicles such as utility or bucket trucks, delivery vehicles, refuse 

haulers, and buses have operational usage patterns with either a significant amount of 

stop-and-go activity or spend a large portion of their operating hours idling the main 

engine to operate a PTO unit. The industry is currently developing three types of hybrid 

powertrain systems – hydraulic, electric, and plug-in electric. The hybrids developed to 

date have seen fuel consumption and CO2 emissions reductions between 20 and 50 

percent in the field. However, there are still some key issues that are restricting the 

penetration of hybrids, including overall system cost, battery technology, and lack of 

cost-effective electrified accessories. The agencies are proposing to include hybrid 

powertrains as a technology to meet the vocational truck standard, as described in Section 

IV. However, the agencies are not proposing a vocational truck standard predicated on 

using a specific penetration of hybrids. We have not predicated the standards based on 

the use of hybrids reflecting the still nascent level of technology development and the 

 

160 Gaines, Linda, A. Vyas, J. Anderson (Argonne National Laboratory). Estimation of Fuel Use by Idling 

Commercial Trucks. January 2006.
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very small fraction of vehicle sales they would be expected to account for in this 

timeframe on the order of only a percent or two. Where we to overestimate the number 

of hybrids that could be produced, we would set a standard that is not feasible. We 

believe that it is more appropriate given the status of technology development and our 

high hopes for future advancements in hybrid technologies to encourage their production 

through incentives. The agencies welcome comments on this approach. 

(b) Gasoline engine technologies

The gasoline (or spark ignited) engines certified and sold as loose engines into the 

heavy-duty truck market are typically large V8 and V10 engines produced by General 

Motors and Ford. The basic engine architecture of these engines is the same as the 

versions used in the heavy-duty pickup trucks and vans. Therefore, the technologies 

analyzed by the agencies mirror the gasoline engine technologies used in the heavy-duty 

pickup truck analysis. 

Building on the technical analysis underlying the 2010 light-duty FRM, the 

agencies took a fresh look at technology effectiveness values for purposes of this 

proposal. NHTSA and EPA used the estimates from the 2012-2016 LD rule as a 

baseline. The agencies then considered the impact of test procedures (such as higher test 

weight of HD pickup trucks and vans) on the effectiveness estimates. The agencies also 

considered other sources such as the 2010 NAS Report, recent CAFE compliance data, 

and confidential manufacturer estimates of technology effectiveness. NHTSA and EPA 

engineers reviewed effectiveness information from the multiple sources for each 

technology and ensured that such effectiveness estimates were based on technology

hardware consistent with the BOM components used to estimate costs. 

The agencies note that the effectiveness values estimated for the technologies may

represent average values, and do not reflect the potentially-limitless spectrum of possible 

values that could result from adding the technology to different vehicles. For example, 

while the agencies have estimated an effectiveness of 0.5 percent for low friction 

lubricants, each vehicle could have a unique effectiveness estimate depending on the 

baseline vehicle’s oil viscosity rating. For purposes of this NPRM, NHTSA and EPA 

believe that employing average values for technology effectiveness estimates is an 

appropriate way of recognizing the potential variation in the specific benefits that 

individual manufacturers (and individual engines) might obtain from adding a fuel-saving 

technology. However, the agencies seek comment on whether additional levels of 

specificity beyond that already provided would improve the analysis for the final rules, 

and if so, how those levels of specificity should be analyzed.

Baseline Engine: Similar to the gasoline engine used as the baseline in the Lightduty GHG rule, the agencies assumed the baseline engine in this segment to be a 

naturally aspirated, overhead valve V8 engine. The following discussion of effectiveness 

is generally in comparison to 2010 baseline engine performance.

The technologies the agencies considered include the following:
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Engine Friction Reduction: In addition to low friction lubricants, manufacturers 

can also reduce friction and improve fuel consumption by improving the design of engine 

components and subsystems. Examples include improvements in low-tension piston 

rings, piston skirt design, roller cam followers, improved crankshaft design and bearings, 

material coatings, material substitution, more optimal thermal management, and piston 

and cylinder surface treatments. The 2010 NAS, NESCCAF and EEA reports as well as 

confidential manufacturer data used in the Light-duty GHG rulemaking suggested a range 

of effectiveness for engine friction reduction to be between 1 to 3 percent. NHTSA and 

EPA continue to believe that this range is accurate.

Coupled Cam Phasing: Valvetrains with coupled (or coordinated) cam phasing 

can modify the timing of both the inlet valves and the exhaust valves an equal amount by

phasing the camshaft of a single overhead cam (SOHC) engine or an overhead valve 

(OHV) engine. Based on 2010 Light-duty final rule, previously-received confidential 

manufacturer data, and the NESCCAF report, NHTSA and EPA estimated the 

effectiveness of CCP to be between 1 to 4 percent. NHTSA and EPA reviewed this 

estimate for purposes of the NPRM, and continue to find it accurate. 

Cylinder Deactivation: In conventional spark-ignited engines throttling the 

airflow controls engine torque output. At partial loads, efficiency can be improved by

using cylinder deactivation instead of throttling. Cylinder deactivation can improve 

engine efficiency by disabling or deactivating (usually) half of the cylinders when the 

load is less than half of the engine’s total torque capability – the valves are kept closed, 

and no fuel is injected – as a result, the trapped air within the deactivated cylinders is 

simply compressed and expanded as an air spring, with reduced friction and heat losses. 

The active cylinders combust at almost double the load required if all of the cylinders 

were operating. Pumping losses are significantly reduced as long as the engine is 

operated in this “part cylinder” mode. Effectiveness improvements scale roughly with 

engine displacement-to-vehicle weight ratio - the higher displacement-to-weight vehicles, 

operating at lower relative loads for normal driving, have the potential to operate in partcylinder mode more frequently. Therefore, the agencies reduced the effectiveness 

assumed from this technology for trucks because of the lower displacement-to-weight 

ratio relative to light-duty vehicles. NHTSA and EPA adjusted the 2010 Light-duty final 

rule estimates using updated power to weight ratings of heavy-duty trucks and 

confidential business information and confirmed a range of 3 to 4 percent for these 

vehicles.

Stoichiometric gasoline direct injection (SGDI): Stoichiometric gasoline direct 

injection or Spark Ignition Direct injection engines inject fuel at high pressure directly 

into the combustion chamber (rather than the intake port in port fuel injection). Direct 

injection of the fuel into the cylinder improves cooling of the air/fuel charge within the 

cylinder, which allows for higher compression ratios and increased thermodynamic 

efficiency without the onset of combustion knock. Recent injector design advances, 

improved electronic engine management systems and the introduction of multiple 

injection events per cylinder firing cycle promote better mixing of the air and fuel, 

enhance combustion rates, increase residual exhaust gas tolerance and improve cold start 

emissions. SGDI engines achieve higher power density and match well with other 
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technologies, such as boosting and variable valvetrain designs. The 2010 light-duty final 

rule estimated the effectiveness of SGDI to be between 2 and 3 percent. NHTSA and 

EPA revised these estimated accounting for the use and testing methods for these 

vehicles along with confidential business information estimates received from 

manufacturers while developing the proposal. Based on these revisions, NHTSA and 

EPA estimate the range of 1 to 2 percent for SGDI. 

(c) Diesel engine technologies

Different types of diesel engines are used in vocational trucks, depending on the 

application. They fall into the categories of Light, Medium, and Heavy Heavy-duty

Diesel engines. The Light Heavy-duty Diesel engines typically range between 4.7 and 

6.7 liters displacement. The Medium Heavy-duty Diesel engines typically have some 

overlap in displacement with the Light Heavy-duty Diesel engines and range between 6.7 

and 9.3 liters. The Heavy Heavy-duty Diesel engines typically are represented by

engines between 10.8 and 16 liters. 

Baseline Engine: There are three baseline diesel engines, a Light, Medium, and a 

Heavy Heavy-duty Diesel engine. The agencies developed the baseline diesel engine as a 

2010 model year engine with an aftertreatment system which meets EPA’s 0.2 grams of 

NOx/bhp-hr standard with a selective catalytic reduction (SCR) system along with EGR 

and meets the PM emissions standard with a diesel particulate filter (DPF) with active 

regeneration. The engine is turbocharged with a variable geometry turbocharger. The 

following discussion of technologies describes improvements over the 2010 model year 

baseline engine performance, unless otherwise noted. Further discussion of the baseline 

engine and its performance can be found in section III.C.2.6 below. The following 

discussion of effectiveness is generally in comparison to 2010 baseline engine

performance, and is in reference to performance in terms of the FTP test procedure that 

would be used for compliance for these engine standards. This is in comparison to the 

steady state SET test procedure that would be used for compliance purposes for the 

engines used in Class 7/8 tractors.

Turbochargers: Improved efficiency of a turbocharger compressor or turbine 

could reduce fuel consumption by approximately 1 to 2 percent over today’s variable 

geometry turbochargers in the market today. The NAS report identified technologies 

such as higher pressure ratio radial compressors, axial compressors, and dual stage 

turbochargers as design paths to improve turbocharger efficiency.

Low Temperature Exhaust Gas Recirculation: Most LHDD, MHDD, and HHDD 

engines sold in the U.S. market today use cooled EGR, in which part of the exhaust gas is 

routed through a cooler (rejecting energy to the engine coolant) before being returned to 

the engine intake manifold. EGR is a technology employed to reduce peak combustion 

temperatures and thus NOx. Low-temperature EGR uses a larger or secondary EGR 

cooler to achieve lower intake charge temperatures, which tend to further reduce NOx 

formation. If the NOx requirement is unchanged, low-temperature EGR can allow 

changes such as more advanced injection timing that will increase engine efficiency

slightly more than 1 percent. Because low-temperature EGR reduces the engine’s 
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exhaust temperature, it may not be compatible with exhaust energy recovery systems 

such as turbocompound or a bottoming cycle.

Engine Friction Reduction: Reduced friction in bearings, valve trains, and the 

piston-to-liner interface will improve efficiency. Any friction reduction must be carefully

developed to avoid issues with durability or performance capability. Estimates of fuel 

consumption improvements due to reduced friction range from 0.5% to 1.5%.161

Selective catalytic reduction (SCR): This technology is common on 2010 heavyduty diesel engines. Because SCR is a highly effective NOx aftertreatment approach, it 

enables engines to be optimized to maximize fuel efficiency, rather than minimize 

engine-out NOx. 2010 SCR systems are estimated to result in improved engine 

efficiency of approximately 4 to 5 percent compared to a 2007 in-cylinder EGR-based 

emissions system and by an even greater percentage compared to 2010 in-cylinder 

approaches.162 As more effective low-temperature catalysts are developed, the NOx 

conversion efficiency of the SCR system will increase. Next-generation SCR systems 

could then enable still further efficiency improvements; alternatively, these advances 

could be used to maintain efficiency while down-sizing the aftertreatment. We estimate 

that continued optimization of the catalyst could offer 1 to 2 percent additional reduction 

in fuel use over 2010 model year systems.163

Improved Combustion Process: Fuel consumption reductions in the range of 1 to 

3 percent are identified in the NAS report through improved combustion chamber design, 

higher fuel injection pressure, improved injection shaping and timing, and higher peak 

cylinder pressures.

Reduced Parasitic Loads: Accessories that are traditionally gear or belt driven by

a vehicle’s engine can be optimized and/or converted to electric power. Examples include 

the engine water pump, oil pump, fuel injection pump, air compressor, power-steering 

pump, cooling fans, and the vehicle’s air-conditioning system. Optimization and 

improved pressure regulation may significantly reduce the parasitic load of the water, air 

and fuel pumps. Electrification may result in a reduction in power demand, because 

electrically powered accessories (such as the air compressor or power steering) operate 

only when needed if they are electrically powered, but they impose a parasitic demand all 

the time if they are engine driven. In other cases, such as cooling fans or an engine’s 

water pump, electric power allows the accessory to run at speeds independent of engine 

speed, which can reduce power consumption. The TIAX [2009, pg. 3-5] study used 2 to 4 

percent fuel consumption improvement for accessory electrification, with the 

 

161 TIAX, Assessment of Fuel Economy Technologies for Medium- and Heavy- Duty Vehicles, Final 

Report, Nov. 19, 2009, pg 4-15

162 Stanton, D. “Advanced Diesel Engine Technology Development for High Efficiency, Clean 

Combustion.” Cummins, Inc. Annual Progress Report 2008 Vehicle Technologies Program: Advanced 

Combustion Engine Technologies, US Department of Energy. Pp 113-116. December 2008.

163 TIAX Assessment of Fuel Economy Technologies for Medium and Heavy-duty Vehicles, Report to 

National Academy of Sciences, Nov 19, 2009, pg. 4-9
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understanding that electrification of accessories will have more effect in short-haul/urban 

applications and less benefit in line-haul applications.

(2) What are the projected technology package effectiveness and cost?

(a) Vocational Trucks

(i) Baseline Vocational Truck Performance

The baseline vocational truck model is defined in [TEST], as described in DRIA 

Chapter 4. The agencies used a baseline rolling resistance coefficient for today’s 

vocational truck fleet of 9 kg/metric ton.164 Further truck technology is not included, as 

discussed below in the discussion of the baseline vocational truck. The baseline engine 

fuel consumption represents a 2010 model year diesel engine, as described in DRIA 

Chapter 4. Using these values, the baseline performance of these vehicles is included in 

Table III-12.

Table III-12: Baseline Vocational Truck Performance

Vocational Truck

Light 

Heavy

Medium 

Heavy

Heavy 

Heavy

Fuel Consumption Baseline (gallon/1000 

ton-mile)

44.6 26.7 10.3

CO2 Baseline (grams CO2/ton-mile) 454 272 105

(ii) Vocational Truck Technology Package

The proposed program for vocational trucks for this phase of regulatory standards 

is limited to tire and engine technologies. Aerodynamics technology, weight reduction, 

drive train improvement, and hybrid power trains are not included for the reasons 

discussed above. The agencies are seeking comment on the appropriateness of this 

approach.

The assessment of the proposed technology effectiveness was developed through 

the use of the [TEST] model. To account for the two proposed engine standards, EPA is 

proposing the use of a 2014 model year fuel consumption map in [TEST] to derive the 

2014 model year truck standard and a 2017 model year fuel consumption map to derive 

the 2017 model year truck standard. EPA estimates that the rolling resistance of tires 

 

164 The baseline tire rolling resistance for this segment of vehicles was derived for the proposal based on the 

current baseline tractor and passenger car tires. The baseline tractor drive tire has a rolling resistance of 8.2 

kg/metric ton based on SmartWay testing. The average passenger car has a tire rolling resistance of 9.75 

kg/metric ton based on a presentation made to CARB by the Rubber Manufacturer’s Association. 

Additional details are available in the DRIA Chapter 2. 
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can be reduced by 10 percent in the 2014 model year. The vocational truck standards for 

all three regulatory classes were determined using a tire rolling resistance coefficient of 

8.1 kg/metric ton with a 100 percent application rate by 2014 model year. The set of 

input parameters which are modeled in [TEST] are described in Table III-13. 

Table III-13: TEST Inputs for Vocational Truck Standards

Vocational Truck

2014 MY 2017 MY

Fuel Map 2014 MY 7L for 

LH/MH and 15L for 

HH Trucks 

2017 MY 7L for 

LH/MH and 15L for 

HH Trucks

Tire Rolling Resistance (kg/metric 

ton)

8.1 8.1

The agencies developed the proposed standards by using the engine and tire 

rolling resistance inputs in the [TEST] model, as shown in Table III-13. The percent 

reductions shown in Table III-14 reflect improvements over the 2010 model year baseline 

truck with a 2010 model year baseline engine.

Table III-14: Proposed Vocational Truck Standards and Percent Reductions

Vocational Truck

Light 

Heavy

Medium 

Heavy

Heavy 

Heavy

2016 Fuel Consumption Standard 

(gallon/1000 ton-mile)

41.3 24.5 9.9

2017 Fuel Consumption Standard 

(gallon/1000 ton-mile)

39.7 23.6 9.8

2014 CO2 Standard (grams CO2/ton-mile) 420 249 101

2017 CO2 Standard (grams CO2/ton-mile) 404 240 100

Percent Reduction in 2014 8% 8% 4%

Percent Reduction in 2017 11% 12% 5%

(iii) Technology Package Cost

EPA and NHTSA developed the costs of low rolling resistance tires based on the 

ICF report. The estimated cost per truck is $155 (2008$) for LHD and MHD trucks and 

$186 (2008$) for HHD trucks. These costs include a low complexity ICM of 1.14 and 

are applicable in the 2014 model year

(iv) Alternative Truck Standards Considered

The agencies are not proposing truck standards less stringent than the proposed 

standards because the agencies believe these standards are highly cost effective, as 

described in Section VIII.
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The agencies considered proposing truck standards which are more stringent 

reflecting the inclusion of hybrid powertrains in vocational trucks. However, the 

agencies are not proposing this level of stringency because our assessment is that these 

technologies would not be broadly available for production by the 2017 model year. The 

agencies welcome comments on whether hybrid powertrain technologies are appropriate 

to consider for the 2017 model year standard, or if not, then when would they be 

appropriate.

(b) Gasoline Engines

(i) Baseline Gasoline Engine Performance

EPA and NHTSA developed the reference heavy-duty gasoline engines to 

represent a 2010 model year engine compliant with the 0.2 g/bhp-hr NOx standard for 

on-highway heavy duty engines. 

NHTSA and EPA developed the baseline fuel consumption and CO2 emissions 

for the gasoline engines from manufacturer reported CO2 values used in the certification 

of non-GHG pollutants. The baseline engine for the analysis was developed to represent 

a 2011 model year engine, because this is the most current information available. The 

average CO2 performance of the heavy duty gasoline engines was 660 g/bhp-hour, which 

will be used as a baseline. The baseline gasoline engines are all stoichiometric port fuel 

injected V-8 engines without cam phasers or other variable valve timing technologies. 

While they may reflect some degree of static valve timing optimization for fuel economy 

they do not reflect the potential to adjust timing with engine speed.

(ii) Gasoline Engine Technology Package Effectiveness

The gasoline engine technology package includes engine friction reduction, 

coupled cam phasing, and stoichiometric gasoline direct injection to produce an overall 5 

percent reduction from the reference engine based on the Heavy-duty Lumped Parameter 

model. The agencies are projecting a 100% application rate of this technology package 

to the heavy duty gasoline engines, which results in a CO2 standard of 627 g/bhp-hr and a 

fuel consumption standard of 7.05 gallon/100 bhp-hr. As discussed in Section II.D.b.ii, 

the agencies propose the gasoline engine standards begin in the 2016 model year based 

on the agencies’ projection of the engine redesign schedules of the small number of 

engines in this category.

(iii) Gasoline Engine Technology Package Cost

For costs, the agencies reconsidered both the direct or “piece” costs and indirect 

costs of individual components of technologies. For the direct costs, the agencies 

followed a bill of materials (BOM) approach employed by NHTSA and EPA in the 2012-

2016 LD rule. NHTSA and EPA are proposing to use the marked up gasoline engine 

technology costs developed for the HD Pickup Truck and Van segment because they are 

made by the same manufacturers (primarily by Ford and GM) and, therefore, the indirect 

cost markups used there are more appropriate here. The costs are summarized in Table 

III-15. The costs shown in Table III-15 include a low complexity ICM of 1.17 and are 
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applicable in the 2016 model year. No learning effects are applied to engine friction 

reduction costs, while time based learning is considered applicable to both coupled cam 

phasing and stoichiometric GDI.

Table III-15: Heavy Duty Gasoline Engine Technology Costs (2008$)

2016MY

Engine Friction Reduction $88

Coupled Cam Phasing $43

Stoichiometric Gas Direct Injection $372

Total $504

(iv) Alternative Gasoline Engine Standards Considered

The agencies are not proposing gasoline standards less stringent than the proposed 

standards because the agencies believe these standards are highly cost effective.

The agencies considered proposing gasoline standards which are more stringent 

reflecting the inclusion of cylinder deactivation and other advanced technologies. 

However, the agencies are not proposing this level of stringency because our assessment 

is that these technologies would not be available for production by the 2017 model year. 

The agencies welcome comments on whether other gasoline technologies are appropriate 

to consider for the 2017 model year standard, or if not, then when would they be 

appropriate.

(c) Diesel Engines

(i) Baseline Diesel Engine Performance

EPA and NHTSA developed the baseline heavy-duty diesel engines to represent a 

2010 model year engine compliant with the 0.2 g/bhp-hr NOx standard for on-highway

heavy duty engines. 

The agencies utilized 2007 through 2011 model year CO2 certification levels from 

the FTP cycle as the basis for the reference engine CO2 performance. The pre-2010 data

are subsequently adjusted to represent 2010 model year engine maps by using predefined 

technologies including SCR and other systems that are being used in current 2010 

production. . The engine CO2 results were then sales weighted within each regulatory

class to develop an industry average 2010 model year reference engine, as shown in 

Table III-16. The level of CO2 emissions and fuel consumption of these engines varies 

significantly, where the engine with the highest CO2 emissions is estimated to be 20 

percent greater than the sales weighted average. Details of this analysis are included in 

DRIA Chapter 2.
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Table III-16: 2010 Model Year Reference Diesel Engine Performance

CO2 Emissions 

(g/bhp-hr)

Fuel Consumption 

(gallon/100 bhp-hr)

Light Heavy Diesel - FTP 630 6.19

Medium Heavy Diesel - FTP 630 6.19

Heavy Heavy Diesel - FTP 584 5.74

(ii) Diesel Engine Packages

The diesel engine technology packages for the 2014 model year include engine 

friction reduction, improved aftertreatment effectiveness, improved combustion 

processes, and low temperature EGR system optimization. The improvements in 

parasitic and friction losses come through piston designs to reduce friction, improved 

lubrication, and improved water pump and oil pump designs to reduce parasitic losses. 

The aftertreatment improvements are available through lower backpressure of the 

systems and optimization of the engine-out NOx levels. Improvements to the EGR 

system and air flow through the intake and exhaust systems, along with turbochargers can 

also produce engine efficiency improvements. It should be pointed out that individual 

technology improvements are not additive to each other due to the interaction of 

technologies. The agencies assessed the impact of each technology over the FTP and 

project an overall cycle improvement in the 2014 model year of 3 percent for HHDD and 

5 percent for LHDD and MHDD engines, as detailed in DRIA Chapter 2. EPA used a 

100 percent application rate of this technology package to determine the proposed 2014 

MY standards

Recently, EPA’s non-GHG heavy duty engine program provided new emissions 

standards for the industry in three year increments. The heavy duty engine manufacturer 

product plans have fallen into three year cycles to reflect this environment. EPA is 

proposing set CO2 emission standards recognizing the opportunity for technology

improvements over this timeframe while reflecting the typical heavy duty engine 

manufacturer product plan cycles. Thus, the agency is setting initial standards for the 

2014 model year and a more stringent standard for heavy duty engines beginning in the 

2017 model year.

The 2017 model year technology package for LHDD and MHDD engine includes 

continued development and refinement of the 2014 model year technology package. This 

package leads to a projected 9 percent reduction for LHDD and MHDD engines in the 

2017 model year. The HHDD engine technology packages for the 2017 model year 

include the continued development of the 2014 model year technology package plus 

turbocompounding. A similar approach to evaluating the impact of individual 

technologies as taken to develop the overall reduction of the 2014 model year package 

was taken with the 2017 model year package. The FTP cycle improvements lead to a 5 

percent reduction on the cycle for HHDD, as detailed in DRIA Chapter 2. The agencies 
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used a 100 percent application rate of the technology package to determine the proposed 

2017 MY standards. The agencies believe that bottom cycling technologies are still in 

the development phase and will not be ready for production by the 2017 model year.165 

Therefore, these technologies were not included in determining the stringency of the 

proposed standards. However, we do believe the bottoming cycle approach represents a 

significant opportunity to reduce fuel consumption and GHG emissions in the future. 

EPA and NHTSA are therefore both proposing provisions described in Section IV to 

create incentives for manufacturers to continue to invest to develop this technology.

The overall projected improvements in CO2 emissions and fuel consumption over 

the baseline are included in Table III-17

Table III-17: Percent Fuel Consumption and CO2 Emission Reductions

2014 2017

Light Heavy Diesel - FTP 5% 9%

Medium Heavy Diesel - FTP 5% 9%

Heavy Heavy Diesel - FTP 3% 5%

(iii) Technology Package Costs

NHTSA and EPA jointly developed costs associated with the engine technologies 

to assess an overall package cost for each regulatory class. The agencies are taking a 

slightly different approach to assess the overall costs of the MHD and HHD diesel engine 

program than the BOM approach used for the other regulatory groups. The engine costs 

in this analysis are proposed to include separate analysis of the incremental part costs, 

research and development activities, and additional equipment, such as emissions 

equipment to measure N2O emissions. The agencies are taking a different approach to 

cost estimation in this case because we estimate that the indirect costs including those 

related to research and development are the primary determinant in the cost to the 

manufacturers. Our general approach used elsewhere in this proposal (for HD pickup 

trucks, gasoline engines, Class 7/8 tractors, and Class 2b-8 vocational trucks) estimates a 

direct manufacturing cost for a part and marks it up based on a factor to account for 

indirect costs. See also 75 FR at 25376. We believe that approach is appropriate when 

compliance with proposed standards is achieved generally by installing new parts and 

systems purchased from a supplier. In such a case, the supplier is conducting the bulk of 

the research and development on the new parts and systems and including those costs in 

 

165 TIAX noted in their report to the NAS panel that the engine improvements beyond 2015 model year 

included in their report are highly uncertain, though they include waste heat recovery in the engine package 

for 2016 through 2020 (page 4-29).
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the purchase price paid by the original equipment manufacturer. The indirect costs 

incurred by the original equipment manufacturer need not include much cost to cover 

research and development since the bulk of that effort is already done. For the MHD 

and HHD diesel engine segment, however, the agencies do not consider this model to be 

the most appropriate because the primary cost is not expected to be the purchase of parts 

or systems from suppliers or even the production of the parts and systems, but rather the 

development of the new technology by the original equipment manufacturer itself. 

Therefore, the agencies believe it more accurate to directly estimate the indirect costs. 

EPA commonly uses this approach in cases where significant investments in research and 

development can lead to an emission control approach that requires no new hardware. 

For example, combustion optimization may significantly reduce emissions and cost a 

manufacturer millions of dollars to develop but will lead to an engine that is no more 

expensive to produce. Using a bill of materials approach would suggest that the cost of 

the emissions control was zero reflecting no new hardware and ignoring the millions of 

dollars spent to develop the improved combustion system. Details of the cost analysis are 

included in the DRIA Chapter 2. To reiterate, we have used this different approach 

because the MHD and HHD diesel engines are expected to comply in large part via 

technology changes that are not reflected in new hardware but rather knowledge gained 

through laboratory and real world testing that allows for improvements in control system 

calibrations – changes that cannot be reflected well through direct costs with indirect cost 

multipliers.

The agencies developed the engineering costs for the research and development of 

diesel engines with lower fuel consumption and CO2 emissions. The aggregate costs for 

engineering hours, technician support, dynamometer cell time, and fabrication of 

prototype parts are estimated at $6,750,000 per manufacturer per year over the five years 

covering 2012 through 2016. In aggregate, this average out to $530 per engine during 

2012 through 2016 using a very rough annual sales value of 280,000 medium-HD and 

heavy-HD engines. The agencies also are estimating costs of $100,000 per engine 

manufacturer per engine class (medium-HD and heavy-HD) to cover the cost of 

purchasing photo-acoustic measurement equipment for two engine test cells. This would 

be a one-time cost incurred in the year prior to implementation of the standard (i.e., the 

cost would be incurred in 2013). In aggregate, this averages out to $4 per engine in 2013 

using a very rough annual sales value of 280,000 medium-HD and heavy-HD engines.

EPA also developed the incremental piece cost for the components to meet each 

the 2014 and 2017 standards. Indirect Cost Multipliers and learning are applied to each 

technology to develop the piece costs included in Table III-18. All costs shown in Table 

III-18 include a low complexity ICM of 1.11 and time based learning is considered 

applicable to each technology.
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Table III-18: Heavy-duty Diesel Engine Component Costs (2008$)

2014 Model 

Year

2017 Model 

Year

Cylinder Head (flow optimized, increased firing 

pressure, improved thermal management)

$6 $6

Exhaust Manifold (flow optimized, improved 

thermal management)

$0 $0

Turbocharger (improved efficiency) $17 $16

EGR Cooler (improved efficiency) $3 $3

Water Pump (optimized, variable vane, variable 

speed)

$87 $79

Oil Pump (optimized) $4 $4

Fuel Pump (higher working pressure, increased 

efficiency, improved pressure regulation)

$4 $4

Fuel Rail (higher working pressure) $10 $9

Fuel Injector (optimized, improved multiple event 

control, higher working pressure)

$10 $9

Piston (reduced friction skirt, ring and pin) $3 $2

Aftertreatment system (improved effectiveness 

SCR, dosing, dpf)a

$0 (MH & 

HH)

$111 (LH)

$0 (MH & HH)

$101 (LH)

Valve Train (reduced friction, roller tappet) $78 $71

a Note that costs for aftertreatment improvements for MH and HH diesel engines are covered via the 

engineering costs (see text). For LH diesel engines, we have included the cost of aftertreatment 

improvements as a technology cost.

The overall costs for each diesel engine regulatory class are included in Table 

III-19.

Table III-19: Diesel Engine Technology Costs per Engine (2008$)

2014 2017

LHD Diesel $328 $299

MHD Diesel $223 $203

HHD Diesel $145 $132

(iv) Alternative Diesel Engine Standards Considered

The agencies are not proposing diesel engine standards less stringent than the 

proposed standards because the agencies believe these standards are highly cost effective.
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The agencies considered proposing diesel engine standards which are more 

stringent reflecting the inclusion of other advanced technologies. However, the agencies 

are not proposing this level of stringency because our assessment is that these 

technologies would not be available for production by the 2017 model year. The 

agencies welcome comments on whether other diesel engine technologies are appropriate 

to consider for the 2017 model year standard, or if not, then when would they be 

appropriate.

IV. Proposed Regulatory Flexibility Provisions

This section discusses proposed flexibility provisions intended to achieve the 

goals of the overall GHG program while providing alternate pathways to achieve those 

goals. The primary flexibility provisions the agencies are proposing for combination 

tractors and vocational trucks relate to a program of Averaging, Banking, and Trading of 

credits (ABT) that EPA and NHTSA are proposing in association with each agency’s 

respective standards (see Section II above). For HD pickups and vans, the primary

flexibility provision is the fleet averaging program patterned after the LD GHG and 

CAFE rule. In addition, this section also describes proposed flexibility provisions that 

would apply in specific circumstances.

A. Averaging, Banking, and Trading (ABT) Program

Averaging, Banking, and Trading (ABT) of emissions credits have been an 

important part of many EPA mobile source programs under CAA Title II, including 

engine and vehicle programs. ABT programs can be important because they can help to 

address many issues of technological feasibility and lead-time, as well as considerations 

of cost. ABT programs are not just add-on provisions included to help reduce costs, but 

are usually an integral part of the standard setting itself. An ABT program is important

because it provides manufacturers flexibilities that assist the development and 

implementation of new technologies efficiently, and therefore enables new technologies 

to be implemented more quickly than without ABT. A well-designed ABT programs can 

provide important environmental benefits and at the same time increase flexibility and 

reduce costs for the regulated industry. 

Section II above describes EPA’s proposed GHG emission standards and 

NHTSA’s proposed fuel consumption standards. For each of these respective sets of 

standards, the agencies are also proposing ABT provisions consistent with each agency’s 

statutory authority. The agencies have worked closely together to design these proposed 

provisions to be essentially identical to each other in form and function. Because of this 

fundamental similarity, the remainder of this section refers to these provisions 

collectively as “the ABT program” except where agency-specific distinctions are 

required.

As discussed in detail below, the structure of this proposed GHG ABT program 

for HD engines is based closely on earlier ABT programs for HD engines; the proposed 

program for HD pickups and vans is built on the existing light-duty GHG program 

flexibility provisions; and we propose first-time ABT provisions for combination tractors 
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and vocational trucks that are as consistent as possible with our other HD vehicle 

regulations. The flexibility provisions associated with this new regulatory category are 

intended to systematically build upon the structure of the existing programs. 

As an overview, “averaging” means the exchange of emission credits between 

engine families or truck families within a given manufacturer’s regulatory class. For 

example within each regulatory class, engine manufacturers divide their product line into 

‘‘engine families’’ that are comprised of engines expected to have similar emission 

characteristics throughout their useful life. Averaging allows a manufacturer to certify

one or more engine families within the same regulatory class at levels above the 

applicable emission standard. The increased emissions over the standard must be offset 

by one or more engine families within that manufacturer’s regulatory class that are 

certified below the same emission standard, such that the average emissions from all the 

manufacturer’s engine families, weighted by engine power, regulatory useful life, and 

production volume, are at or below the level of the emission standard. (The inclusion of 

engine power, useful life, and production volume in the averaging calculations allows the 

emissions credits or debits to be expressed in total emissions over the useful life of the 

credit-using or generating engine sales.) Total credits for each regulatory class within 

each model year are determined by summing together the credits calculated for every

engine family within that specific regulatory class. 

“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 to another manufacturer. In the current program, manufacturers 

are restricted to only averaging, banking and trading credits generated within a regulatory 

class. In the past, we have followed this practice of allowing trading between like 

products for two primary reasons. First by only allowing credit averaging, banking and 

trading between similar products we can help ensure that the regulations do not create an 

unlevel playing field for the regulated industry. Engine and truck manufacturers have 

commonly expressed to us a concern that some manufacturers with a wide range of 

product offerings spanning a number of regulatory categories would be able to use the 

ABT program provisions to generate credits in regulatory class markets where they face 

less competition and then use those credits to compete unfairly in other regulatory 

categories where they face greater competition. Second, we have recognized that the 

estimation of emission credits is not an absolutely precise process and actual emission 

reductions or increases “in-use” will vary due to differences in vehicle duty cycles, 

maintenance practices and any number of other factors. By restricting credit trading 

between like products, the agencies gain some degree of assurance that the operation and 

use of the vehicles generating credits and consuming credits will be similar.

Emission credits in the current EPA engine ABT program and NHTSA fuel 

consumption credits represent the amount of emissions and fuel consumption of an 

engine or truck family that fall below or above the applicable CO2 emission and fuel 

consumption standards. Calculated or selected emissions and fuel consumption levels

below the standard create “positive credits,” while calculated or selected emissions and 

fuel consumption levels above the standard create “negative credits.” In addition, 
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“projected credits” refer to emission and fuel consumption credits based on the (future or 

estimated) projected applicable production volume of the engine or truck family. 

“Reserved credits” are emission and fuel consumption credits generated within a model 

year waiting to be reported to the agencies at the end of the model year. “Actual credits” 

refer to emission credits based on actual applicable production volume as contained in the 

end-of-year reports (or final reports as applicable) submitted to the agencies. Some or all 

of these credits may be revoked if the agencies review of the end-of-year reports or any 

subsequent audit action(s) reveals problems or errors with credit computations.

For this proposal, the agencies are adopting the framework of EPA’s existing 

engine ABT program, including how averaging, banking, and trading would work in the 

proposed GHG and fuel consumption ABT program.

(1) Heavy-duty Engines

For the heavy-duty engine ABT program, the EPA and NHTSA are proposing to 

use EPA’s existing regulatory engine classification categories as the category

designations under this engine ABT program. The existing diesel engine categories are 

light-heavy duty (LHD), medium-heavy duty (MHD), and heavy-heavy duty (HHD). 

LHD diesel engines are primarily used in vehicles with a gross vehicle weight rating 

(GVWR) of less than 19,500 lbs. These engines typically have a rated horsepower 

ranging from 70 to 170hp. Vehicle body types in this group might include any heavyduty vehicle built for a light-duty truck chassis, van trucks, multi-stop vans, recreational 

vehicles, and some single axle straight trucks. Vehicles containing these engines would 

normally include personal transportation, light-load commercial hauling and delivery, 

passenger service, agriculture, and construction applications.

MHD diesel engines are normally used in vehicles whose GVWR varies from 

19,500–33,000 lbs. These diesel engines rated horsepower generally ranges from 170 to 

250hp. Vehicles containing these engines typically include school buses, tandem axle 

straight trucks, city tractors, and a variety of special purpose vehicles such as small dump 

trucks, and trash compactor trucks. Normally the applications for these vehicles would 

include commercial short haul and intra-city delivery and pickup. 

HHD diesel engines are intended for use in vehicles which exceed 33,000 lbs. 

GVWR. These diesel engines rated horsepower generally exceeds 250hp. Vehicles 

containing engines of this type are normally tractors, trucks, and buses used in inter-city, 

long-haul applications. HHD engines are generally regarded as designed for rebuild and 

have a long useful life period. LHD and MHD engines are typically not intended for 

rebuild, though some MHD engines are designed for rebuild, and have a shorter useful 

life. 

Gasoline or spark ignited engines for heavy-duty vehicles fall into one separate 

regulatory class. These engines are typically installed in trucks with a GVWR ranging 

from 8,500 pounds to 19,500 pounds although they can be installed into trucks of any 

size.
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The compliance program we are proposing would adopt a slightly different 

method for generating a manufacturer’s CO2 emission and fuel consumption credit or 

deficit. The manufacturer’s certification test result would serve as the basis for the 

generation of the manufacturer’s family certification level (FCL). The FCL is a new term 

we propose for this program to differentiate the purpose of this credit generation 

technique from the family emission limit (FEL) previously used in a similar context in 

other EPA rules. A manufacturer could define its FCL at any level at or above the 

certification test result. Credits for the ABT program would be generated when the FCL 

is compared to the CO2 and fuel consumption standard, as discussed in section II. The 

credits earned in this section will be restricted to the engine classification and not tradable 

with other engine classifications consistent with EPA’s past practice for ABT programs 

as described previously. Credit calculation for the proposed Engine ABT and fuel 

consumption programs would be generated, either positive or negative, according to 

Equation IV-1 and Equation IV-2:

Equation IV-1 Proposed HD Engine CO2 credit (deficit)

HD Engine CO2 credit (deficit) (metric tons) = (Std-FCL) x (CF) x (Volume) x (UL) x 

(10-6)

where

Std = the standard associated with the specific engine regulatory class (g/hp-hr)

FCL = Family Certification Level for the engine family

CF = a transient cycle conversion factor in bhp-hr/mile which is the integrated 

total cycle brake horsepower-hour divided by the equivalent mileage of the applicable 

test cycle. For gasoline heavy duty engines, the equivalent mileage is 6.3 miles. For 

diesel heavy duty engines, the equivalent mileage is 6.5 miles.

Volume = (projected or actual) production volume of the engine family

UL = useful life of the engine (miles)

10-6converts the grams of CO2 to metric tons

Equation IV-2: Proposed HD Engine Fuel Consumption credit (deficit) in gallons 

HD Diesel Engine Fuel Consumption credit for (deficit) (gallons) = (HD Engine CO2

Credit in metric tons) x (106) / (PG)

Where

PG=the number of grams of CO2 per gallon of fuel: 10,180 for diesel, 8,871 for 

gasoline

HD Gasoline Engine Fuel Consumption credit for (deficit) (gallons) = (HD 

Engine CO2 Credit in metric tons) x (106) / (8,871)
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106converts the metric tons to grams

To calculate credits, manufacturers would determine a family certification limit

(FCL) for each engine family category they have designated for the ABT program. That 

FCL may be above (negative) or below (positive) the standard and would be used to 

establish the CO2 credits earned (or used) in Equation IV-1. The proposed CO2 and fuel 

consumption standards are associated with specific regulatory classes as described in 

§II.C (light heavy-duty, medium heavy-duty, and heavy heavy-duty). In the ABT 

program, engines certified with an FCL below the standard in each of the three regulatory

classes in Table IV-1 could generate positive credits (g/bhp-hr and gal/100 bhp-hr). The 

volume used in Equation IV-1 refers to the total number of eligible engines sold per 

family to participate in the ABT program during that model year. An engine family is 

described in draft regulation 40 CFR 1036.230. 

In equation IV-1, a manufacturer would also need to average its Power Rating 

across their engine family configurations and weight this figure by sales volume per 

engine family class. As an example, a manufacturer with three engine families in their 

fleet engine family average subject to the ABT program with power rating classes of 300, 

325 and 350 horsepower would average the power rating of these classes according to 

intended volume of sales, Let’s assume the manufacturer sells (100, 150 and 200) 

engines respectively. The resulting average power rating would be [(300 hp x 100) + 

(325 hp x 150) + (350 hp x 200)] ÷ 450, so the average would be 330.56 hp. 

The useful life values in Equation IV-1 are proposed to be the same as the 

regulatory classifications previously used for the LHD, MHD and HHD engine groups. 

Thus, the agencies propose that for LHD diesel engines and gasoline engines, the useful 

life values would be 110,000; for MHD engines, 185,000 miles; and for HHD engines, 

435,000 miles. Once CO2 credits are calculate using Equation IV-1, a manufacturer 

would simply convert the tons of CO2 to gallons to calculate fuel consumption credits, 

using Equations IV-2.

 The same equation would be used to compute credits needed to reconcile deficits 

when the manufacturer seeks to settle shortfalls within a particular model year that still 

meets EPA’s GHG standards and NHTSA’s fuel consumption standards under the ABT 

program. We have defined engine families in 40 CFR § 1036.230 and manufacturers 

may designate how to group their engines for certification and compliance purposes.
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Table IV-1: Engine Service Classes

Engine Category Intended service class description

LHD light-duty truck chassis

van

multi-stop van

single axle straight trucks

MHD school buses

tandem axle straight trucks

City tractors

Dump and Refuse

Utility vehicles

HHD Multi-axle trucks used long-haul applications

Large inter-city busses

Credits generated by engine manufacturers under this ABT program would be 

restricted for use only within their engine class based on performance against the 

standard as defined in Table II.1. For example, LHD engine manufacturers could only

use their LHD engine credits for averaging, banking and trading with LHD engines, not 

with MHD or HHD engines. This limitation is consistent with today’s criteria pollutant 

program for engines and would help ensure that credits earned to reduce GHG emissions 

and fuel consumption would be used to limit their growth and not circumvent the intent 

of the regulations. EPA and NHTSA are concerned that extending the use of credits 

beyond these designated classes could also create an advantage for large or integrated 

manufacturers that currently does not exist in the market. A manufacturer that produces 

both engines and equipment for heavy-duty highway vehicles could mix credits across 

engine and equipment sectors, shifting the burden between the sectors, not equally shared 

in either sector, to gain an advantage over competitors that are not integrated. Similarly, 

large volume manufacturers of engines can shift credits between heavy-heavy duty 

engines and light-heavy duty engines to gain an advantage in one sector over other 

manufacturers that may not have multiple engine offerings over several regulatory engine 

sectors. Finally, relating credits between categories of engines could be problematic 

because of the differences in regulatory useful lives. The agencies want to avoid having 

credits from longer useful life categories flooding shorter useful life categories, adversely 

impacting compliance with CO2 standards in the shorter useful life category. The 

agencies would like to ensure that this regulation reduces CO2 emissions and fuel 

consumption in each engine category but does not interfere with the ability of 

manufacturers to engage in free trade and competition. Limiting credit ABT to the 

regulatory category and not between engines and equipment would help due solely to the 

regulatory structure to insure that we offer no new advantage to any competitor in the 

market place. However, the agencies welcome comments on the extension of credits 

beyond the limitations we are proposing. 

Under previous ABT programs for other rulemakings, EPA has allowed 

manufacturers to carry forward deficits from engines for a set period of time. The 

agencies are proposing to allow manufacturers of engines to carry forward deficits for up 

to three years before reconciling the short-fall. However, manufacturers must use credits, 
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once credits are generated, to offset a shortfall before credits may be banked or traded for 

additional model years. This restriction reduces the chance of manufacturers passing 

forward deficits before reconciling shortfalls and exhausting those credits before 

reconciling past deficits. We will accept comments on alternative approaches for 

reconciling deficit shortfalls in the engine category.

As described in section II above, EPA is proposing that engine manufacturers 

have the added option of combining their CH4 and N2O emissions with their CO2

emissions for a CO2 equivalence value that recognizes the inter-correlation of these 

elements in impacting global warming. This option does not apply to the NHTSA fuel 

consumption program. To take account of the different global warming potential of these 

GHGs, EPA proposes to use Equation IV-3:

Equation IV-3: CO2 Eq = CO2 + (25*CH4) + (298 *N2O)

The CO2 equivalency equation can be used to combine CH4 and N2O with CO2

where the result would need to meet the CO2 standard rather than report numbers for the 

CO2 standard and separate numbers for the N2O and CH4 caps. In general, we do not 

expect manufacturers to use this provision. However, we are providing this alternative as 

a flexibility in the event an engine OEM has trouble meeting the CH4 and/or the N2O 

emissions caps. (As specified above, there are no ABT credits for performance that falls 

below N2O and CH4 caps). Manufacturers would need to meet the FEL limit when they

use the CO2 equivalent standard, not the FCL imposed for CO2 alone.

Additional flexibilities for engines are discussed later in Section IV(B). Engine 

manufacturers will not need to adopt new testing provisions or new equipment to assess 

engine performance to meet the requirements for CO2 emissions or fuel consumption 

reduction, though manufacturers may need to purchase new equipment to measure N2O. 

In fact, the only additional testing cost that is anticipated to meet the GHG standards set 

forth above will likely be N2O measurement equipment. We have not generated new 

classifications for manufacturers outside the existing ones previously chosen for this 

industry so we do not anticipate any additional difficulties presented in this regulation for 

manufacturers to understand and utilize our ABT program. We welcome comments on 

additional arguments related to needed flexibility within this program. 

(2) Class 7/8 Combination Tractors 

In addition to the engine ABT program described above, the agencies are also 

proposing a vehicle ABT program to facilitate reductions in GHG emissions and fuel 

consumption based on combination tractor design changes and improvements. For this 

category, the structure of the proposed ABT program should create incentives for tractor 

manufacturers to advance new, clean technologies, or existing technologies earlier than 

they would otherwise. 

As explained above, combination tractor manufacturers are divided into the 

following nine regulatory classes under these proposed rules:
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Class 7 Day Cab Class 8 Day Cab Class 8 Sleeper Cab

Low Roof Low Roof Low Roof

Mid Roof Mid Roof Mid Roof

High Roof High Roof High Roof

Vehicle credits for tractors in these classifications will be earned on a g/ton-mile 

or gallon/1000 ton-mile basis for tractors which are below the standard. Credits 

generated within regulatory classes will be tradable between truck manufacturers in that 

specific regulatory class only. Credits will not be fungible between engine and vehicle 

regulatory classes. This is similar to the restrictions we have described above for engine 

manufacturers. 

This limitation will help ensure that credits earned to reduce GHG emissions and 

fuel consumption will be used to limit their growth and not circumvent the intent of our 

regulation. We are concerned that extending the use of credits to be transferred or traded 

to other classes may create an advantage for large or integrated manufacturers that 

currently does not exist in the market. We would like to ensure that this regulation 

reduces the emission of CO2 and fuel consumption but does not interfere with the ability

of manufacturers to engage in free trade and competition. This addresses competitive 

concerns expressed by non-integrated manufacturers and those with limited participation

in the market. This structure allows for a straightforward compliance program for each 

sector independently with aspects that are also independently quantifiable and verifiable. 

Credit calculation for the Proposed Class 7/8 Tractor CO2 and fuel consumption credits 

will be generated, either positive or negative, according to Equation IV-4 and Equation 

IV-5:

Equation IV-4: The proposed Class 7/8 Tractor CO2 credit (deficit)

Class 7/8 Tractor CO2 credit (deficit)(metric tons) = (Std-FCL) x (Payload Tons) x 

(Volume) x (UL) x (10-6)

where

Std = the standard associated with the specific tractor regulatory class (g/ton-mile)

Payload tons = the prescribed payload for each class in tons (12.5 tons for Class 7 

and 19 tons for Class 8)

FCL = Family Certification Level for the tractor family

Volume = (projected or actual) production volume of the tractor family

UL = useful life of the tractor (435,000 miles for Class 8 and 185,000 miles for 

Class 7)

10-6converts the grams of CO2 to metric tons

Equation IV-5: Proposed Class 7/8 Tractor Fuel Consumption credit (deficit) in gallons = 
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Class 7/8 Tractor Fuel Consumption credit for (deficit) (gallons) = (Class 7/8 Tractor

CO2 credit in metric tons) x (106) / (10,180)

where

10,180 is the number of grams of CO2 per gallon of diesel fuel

106converts the metric tons to grams

Similar to the proposed Heavy-duty Engine ABT program described in the

previous section, tractor manufacturers would be able to carry forward credit deficits 

from their regulatory classes for three years before reconciling the shortfall. However, 

just as in the engine category, manufacturers must use credits once those credits have 

been generated to offset a shortfall before those credits can be banked or traded for 

additional model years. This restriction reduces the chance of tractor manufacturers 

passing forward deficits before reconciling their shortfalls and exhausting those credits 

before reconciling past deficits. Manufacturers of vehicles that generate a deficit at the 

end of the model year, i.e. their fleet average exceeds the fleet standard for their vehicle 

classification, that manufacturer could carry that deficit forward for three years following 

the model year for which that deficit was generated. Deficits must be reconciled at the 

reporting dates for year three. We will accept comments on alternative approaches of 

reconciling deficit shortfalls.

Additional flexibilities for class 7/8 combination tractors are discussed later in 

Section IV(B).

(3) Class 2b-8 Vocational Vehicles

Similar to the Class 7 and 8 combination tractor manufacturers, we are offering a 

limited ABT program for Class 2b-8 vocational chassis manufacturers. As the 

certification of the chassis will be based on the use of low rolling resistance tires, those 

manufacturers that introduce products into the market with performance improvements, 

which are better than required to meet the vehicle standards, vehicle credits will be 

generated. Credit calculation for the Proposed Class 2b-8 vocational vehicle CO2 and 

fuel consumption credits (deficits) will be generated, either positive or negative, 

according to Equation IV-6 and Equation IV-7:

Equation IV-6: The proposed HD HWY CO2 vehicle credit (deficit)

Vocational Vehicle CO2 credit (deficit) (metric tons) = (Std-FCL) x (Payload Tons) x 

(Sales Volume) x (UL) x (10-6) 

where

Std = the standard associated with the specific tractor regulatory class (g/ton-mile)
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Payload tons = the prescribed payload for each class in tons (2.85 tons for LHD, 

5.6 tons for MHD, and 19 tons for HHD)

FCL = Family Certification Level for the vehicle family

Volume = (projected or actual) production volume of the vehicle family

UL = useful life of the vehicle (110,000 miles for LHD, 185,000 miles for MHD, 

or 435,000 miles for HHD)

10-6converts the grams of CO2 to metric tons

Equation IV-7: Proposed Vocational Vehicle Fuel Consumption credit (deficit) in gallons 

Vocational Vehicle Fuel Consumption credit for (deficit) (gallons) = (Vocational Vehicle

CO2 credit in metric tons) x (106) / (10,180)

where

10,180 is the number of grams of CO2 per gallon of diesel fuel

106converts the metric tons to grams

Also similar to the proposed heavy-duty engine and tractor ABT programs, the 

vehicle credits generated within each regulatory class will be allowed to be averaged, 

banked, or traded between chassis manufacturers within their existing categories. For 

vocational vehicles the categories are based on the vehicles GVWR rating. We are 

proposing vehicles with a GVWR <14,000 lbs, vehicles between 14,000 and 26,000 lbs, 

and vehicles with a GVWR >26,000 lbs. These three weight categories will form the 

restrictive classifications for vocational vehicles and are discussed in 40 CFR § 1037.230. 

Similar to the proposed Heavy-duty Engine ABT program above, vocational 

chassis manufacturers will be able to carry forward deficits from their fleet-wide average 

for three years before reconciling the shortfall. However, just as in the engine category, 

manufacturers must use credits earned once those credits have been generated to offset a 

shortfall before those credits can be banked or traded for additional model years. This 

restriction reduces the chance of chassis manufacturers passing forward deficits before 

reconciling their shortfalls and exhausting those credits before reconciling past deficits. 

Manufacturers of vocational vehicles that generate a deficit at the end of the model year, 

could carry that deficit forward for three years following the model year for which that 

deficit was generated. Deficits must be reconciled at the reporting dates for year three. 

We will accept comments on alternative approaches of reconciling deficit shortfalls.

B. Class 2b/3 Heavy-duty Pickup Trucks and Vans Flexibility 

Provisions

As explained above, EPA and NHTSA are proposing specific flexibility

provisions for manufacturers of HD pickups and vans similar to the fleet-averaging 
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program that currently exists for light-duty cars and trucks. An flexibility program is 

important because it provides manufacturers flexibilities that assist the development and 

implementation of new technologies efficiently, and therefore enables new technologies 

to be implemented faster than without a flexibility program. A flexibility program also 

provides incentives to manufacturers if there are unexpected shifts in sales. 

A manufacturer’s credit or debit balance will be determined by calculating their 

fleet average performance and comparing it to the manufacturer’s CO2 and fuel 

consumption standards, as determined by their fleet mix, for a given model year. A target 

standard is determined for each vehicle with a unique payload, load capacity and drive 

configuration. These unique targets along with their associated production volumes are 

summed to derive the production volume-weighted manufacturer annual fleet average 

standard. The attribute basis for Class 2b/3 differs from our light-duty approach. The 

attribute basis for this flexibility will be the payload, 4-wheel drive (4WD) and towing 

capacity as discussed in Section II. A manufacturer will generate credits if its vehicle 

achieves a fleet average CO2 or fuel consumption level lower than its standard and will 

generate debits if its fleet average CO2 or fuel consumption level is above that standard. 

At the end of the model year, each manufacturer will calculate a production-weighted 

fleet average. If a manufacturer’s fleet achieves a fleet average CO2 and fuel consumption 

level lower than its standard, it will generate credits, and if its fleet average CO2 and fuel 

consumption level is above that standard, it will generate debits. The end-of-year reports 

will provide appropriate data to assess pre-compliance estimates with final model year 

figures. Similar to Tier 2 and LD GHG programs, the agencies would address any

ultimate deficits by a possible void of certificates on a sufficient number of vehicles to 

address shortfall. Enforcement action would fall to penalty or other relief as appropriate 

or applicable.

The credit calculation for the Proposed Class 2b and 3 Heavy Duty Pickup and 

Van GHG and fuel consumption regulations will be generated, either positive or negative, 

according to Equation IV-18 and Equation IV-9:

Equation IV-8 The proposed class 2b-3 Heavy Duty Pickup and Vans CO2 credit (deficit)

Class 2b-3 HD PU and Van CO2 credit (deficit) (metric tons) = (Manufacturer’s 

Production Weighted Fleet Emission Standard-Manufacturer’s Production Weighed Fleet 

Average Emission Performance) x (Sales Volume) x (UL) x (10-6) 

where

Std = the standard associated with the specific 2b/3 pickup and van 

regulatory class (g/ton-mile)

Manufacturers Fleet Performance = [EPA needs to clarify that 

performance is determined using the unique configurations within each model 

type] 

Sales Volume = (projected or actual) production volume of the vehicle 

family
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UL = useful life of the vehicle (xxxxx miles) 

10-6converts the grams of CO2 to metric tons

Equation IV-7 Proposed Vocational Vehicle Fuel Consumption credit (deficit) in gallons = 

Vocational Vehicle Fuel Consumption credit for (deficit) (gallons) = (Class 2b-3 HD PU 

and Van CO2 fleet credits in metric tons) x (106) / (10,180)

where

10,180 is the number of grams of CO2 per gallon of diesel fuel

106converts the metric tons to grams

We propose to prohibit trading between Class 2b/3 complete vehicles and any

other category including light-duty passenger cars and light trucks, engines, Class 7/8 

tractors, and Class 2b-8 Vocational Vehicles. We propose to allow trading only within 

the Class 2b/3 complete vehicle category. This restriction is intended to promote 

improvements in GHG emissions and fuel consumption in all vehicle and engine 

categories, and to avoid shifting the burden or cost of reduction to other categories. It is 

expected these restrictions will maximize improvements across all regulated categories.

Similar to the proposed Heavy-duty Engine ABT program above, class 2b/3 

heavy duty pickup and van manufacturers under this flexibility program would be able to 

carry forward deficits from their fleet-wide average for three years before reconciling the 

shortfall. Manufacturers will be required to provide a plan in their pre-model year reports 

showing how they will resolve projected credit deficits. However, just as in the engine 

category, manufacturers must use credits earned once those credits have been generated 

to offset a shortfall before those credits can be banked or traded for additional model 

years. This restriction reduces the chance of vehicle manufacturers passing forward 

deficits before reconciling their shortfalls and exhausting those credits before reconciling 

past deficits. We will accept comments on alternative approaches of reconciling deficit 

shortfalls.

C. Additional Proposed Flexibility Provisions

In the proposed GHG program we have developed provisions to facilitate 

reductions in GHG emissions and fuel consumptions beginning in the 2014 model year. 

We have specifically focused on reducing CO2 emissions and fuel consumption. While 

we view our proposed ABT and flexibility structure as sufficient to encourage reduction 

efforts by heavy-duty highway engine and vehicle manufacturers, we understand that 

other efforts may enhance the overall GHG reduction we anticipate achieving. Therefore 

we propose the following flexibilities to address additional opportunities for 

manufacturers to reduce their GHG emissions and fuel consumption. These opportunities 
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will help provide additional incentives for manufacturers to innovate and to develop new 

strategies and cleaner technologies. 

(1) Early Credit Option

The agencies are proposing that manufacturers of HD engines, combination 

tractors, and vocational trucks be eligible to generate early credits if they demonstrate 

improvements in excess of the standards prior to model year 2014 (for EPA CO2

emission standards) or prior to model year 2016 (for NHTSA fuel consumption 

standards). Specifically, manufacturers would need to certify their engines or vehicles to 

the standards at least six months before the start of the 2014 model year. The limitations 

on the use of credits in the ABT programs – i.e., limiting averaging to within each the 

regulatory category and vehicle or engine subcategory – would apply for the proposed 

early credits as well. We propose that manufacturers of HD pickups and vans that 

demonstrate improvements in excess of the standards [...] be eligible for early credits 

against their fleet average CO2 and fuel consumption standards The agencies consider the 

proposed availability of early credits to be a valuable complement to the overall ABT 

program by encouraging achievement of the standards earlier than would likely otherwise 

occur.

NHTSA and EPA request comment on whether a credit multiplier, specifically a 

multiplier of 1.5, would be appropriate to apply to early credits, as a greater incentive for 

early compliance. Additionally, the agencies seek comment on whether or not a 

requirement that HD engines, combination tractors, and vocational trucks that are eligible 

to generate early credits, be allowed to do so only if they certify prior to June 1, 2013 

should a multiplier of 1.5 be applied to early credits. 

(2) Advanced Technology Credits

As discussed in earlier sections, EPA and NHTSA are proposing targeted 

provisions that we expect would promote the implementation of certain advanced 

technologies. Specifically, manufacturers that show improvements in CO2 emissions and 

fuel consumptions and incorporate the following technologies would be eligible for 

special credits that could be applied to any heavy duty vehicle or engine, and not be 

limited to the vehicle category generating the credit:

 Hybrid powertrain designs that incorporate regeneration of the energy

storage components

 Rankine Cycle engines

 Electric Vehicles (EVs)

For Rankine Cycle engines, we propose that advanced technology credits be 

determined using the same HD engine test procedure used for diesel and gasoline 

engines. For EVs, we propose that advanced technology credits be established based on 

zero vehicle emissions, so that the credit would numerically equal the standard. NHTSA 
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and EPA request comment on whether a credit multiplier, specifically a multiplier of 1.5, 

would be appropriate to apply to advanced technology credits, as a greater incentive for 

their introduction. NHTSA and EPA request comment on the list of technologies 

identified as advanced technologies and whether additional technologies should be added 

to the list. NHTSA and EPA also request comment on whether credits generated from 

vehicles complying prior to 2014 and using Advanced SmartWay or Advanced 

SmartWay II aerodynamic technologies should be designated as Advanced Technology

Credits that could be applied to any heavy duty vehicle or engine.

For vocational trucks incorporating hybrid powertrains, we propose two methods 

for establishing the number of credits generated, each of which is discussed next: 

(a) Chassis Dynamometer Evaluation

For hybrid certification to generate credits we propose to utilize chassis testing as 

an effective way to compare the CO2 emissions and fuel consumption performance of 

conventional and hybrid vehicles. We are proposing that heavy-duty hybrid vehicles be 

certified using “A to B” vehicle chassis dynamometer testing. This concept allows a 

hybrid vocational truck manufacturer to directly quantify the benefit associated with use 

of its hybrid system on an application-specific basis. The concept would entail testing 

the conventional vehicle, identified as “A”, using the cycles as defined in Section V. The 

“B” vehicle would be the hybrid version of vehicle “A”. The “B” vehicle would need to 

be the same exact vehicle model as the “A” vehicle. As an alternative, if no specific “A” 

vehicle existed for the hybrid vehicle that is the exact vehicle model, the most similar 

vehicle model would need to be used for testing. We propose to define the “most similar 

vehicle” as a vehicle with the same footprint, same payload, same testing capacity, the 

same engine power system, the same intended service class, and the same coefficient of 

drag. 

To determine the benefit associated with the hybrid system for greenhouse gas

(GHG) performance, the weighted CO2 emissions results from the chassis test of each 

vehicle would define the benefit as described below:

1. (CO2_A – CO2_B)/ (CO2_A) = ______ (Improvement Factor)

2. Improvement Factor x [TEST] CO2 Result_B = ___ (g/ton mile benefit)

Similarly, the benefit associated with the hybrid system for fuel consumption 

would be determined from the weighted fuel consumption results from the chassis tests of 

each vehicle as described below:

3. (Fuel Consumption_A – Fuel Consumption_B)/ (Fuel Consumption_A)= 

______ (Improvement Factor)

4. Improvement Factor x [TEST] Fuel Consumption Result_B = ___ 

(gallon/ton mile benefit)
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The agencies are proposing two sets of duty cycles to evaluate the benefit 

depending on the vehicle application (such as delivery truck, bucket truck, or refuse 

truck) to assess hybrid vehicle performance. The key difference between these two sets 

of vehicles is that one set (e.g. delivery trucks) does not operate a power take-off (PTO) 

unit while the other set (e.g. bucket and refuse applications) does. The first set of duty

cycles would apply to the hybrid powertrains used to improve the motive performance of 

the vehicle (such as pickup and delivery trucks) and to assess improvements associated 

with hybrid technology. The typical operation of these vehicles is very similar to the 

overall drive cycles proposed in Section II. Therefore, the agencies are proposing to use 

the vocational vehicle weightings for these vehicles, as shown in Table IV-2. We are 

proposing the same regulatory vocational vehicle classifications as for the ABT 

vocational vehicle classification. Should an OEM want to use hybrid or innovative 

vehicles for other sectors, improvements associated with hybrid technology will be 

assessed using traditional duty cycle and test procedures for conventional vehicles. 

Hybrid vehicles used in applications such as utility and refuse trucks tend to have 

additional benefit associated with use of stored energy, which avoids main engine 

operation and related CO2 emissions and fuel consumption. To appropriately address 

these alternative sources for benefits, exercising the conventional and hybrid vehicles 

using their PTO would help to quantify the benefit to GHG emissions and fuel 

consumption reductions. Focus on PTO is specifically for vehicles that use PTO and this 

adequately expresses the inherent function of the vehicle. The duty cycle proposed to 

quantify the hybrid CO2 and fuel consumption impact over this broader set of operation 

would be the three primary cycles plus a PTO duty cycle. Our proposed PTO cycle is 

based on consideration of using alternate, appropriate duty cycles with Administrator 

approval in a public process. The PTO duty cycle as proposed takes into account the 

sales impact and population of utility trucks and refuse haulers. As described below, the 

agencies are proposing to add an additional PTO cycle to measure the improvement 

achieved for this type of hybrid powertrain application. The proposed weightings for the 

hybrids with PTO are included in Table IV-2. 

Table IV-2: Proposed Drive Cycle Weightings for Hybrid Vehicles

Transient 55 mph 65 mph PTO

Vocational Vehicles without PTO 42% 21% 37% 0%

Vocational Vehicles with PTO 30% 15% 27% 28%

(i) Power Take Off (PTO) Cycle

In most PTO equipped trucks, it is necessary to run the primary drive engine at all 

times when the PTO might be needed. Typical PTO systems require no more than 19 kW 

at any time, which is far below the optimal operation range of the primary drive engine of 

most trucks. Furthermore, in intermittent operations, the primary drive engine is kept 

running at all times in order to ensure that the PTO can operate instantaneously. This 

results in excess idle time. It would be possible to hybridize or change the operation of a 

conventional PTO equipped truck to lower the GHG emissions in the real world. 
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However, there is currently no method for an engine, vehicle or equipment manufacturer 

to demonstrate GHG emissions reductions due to the application of advanced PTO 

technology. The current and proposed test procedures do not allow for PTO operation to 

be included in the test protocol. The agencies are proposing to add a new optional PTO 

test to the standard set of tests in order for manufacturers of advanced PTO systems to 

demonstrate in the laboratory environment GHG reductions that will be realized from 

their systems in the real world.

EPA commissioned Southwest Research Institute (SwRI) to review the heavy

duty truck market to determine what types of trucks used PTO’s and if the manufacturers 

thought that there was any possibility of commercial hybrid PTO applications. In some 

segments, manufacturers did not think a hybrid PTO was feasible. On the other hand, 

there are already utility and refuse trucks in existence that feature hybrid PTO units. We 

chose to study the behavior of conventional versions of these trucks in order to 

understand their typical operation.

The agencies are proposing a laboratory test where the vehicle or vehicle 

powertrain, including the PTO, would be put into a laboratory environment. The PTO 

system would then be disconnected from the vehicle apparatus that it normally powers 

and the hydraulic lines would be attached to a test rig. The vehicle or powertrain would 

be started and the PTO would be actuated over cycle, seen in Table IV-3. During the 

cycle, the engine emissions would be measured. In order to determine the GHG 

emissions improvement, the certifying party would need to run a conventional version of 

the PTO system over the cycle and then run the advanced PTO technology package over 

the same cycle. The difference in GHG emissions would be the improvement. 

EPA commissioned SwRI to design a test rig that will be used to run the PTO 

cycle. The test rig is designed to be portable, durable, and easy to replicate. It will have 

two hydraulic circuits so that it can handle two stage PTO pumps typically found on 

refuse trucks with side load arms. In the event a truck had a single stage PTO system, the 

second circuit would not be used. We are proposing that the testing take place on a fully 

warmed up vehicle and PTO system in “standard” laboratory conditions. The test cycle 

will be approximately ten minutes long.
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Table IV-3: Proposed PTO Cycle

Cycle 

Simulation

Mode Time Normalized Pressure, 

Circuit 1 (%)

Normalized Pressure, 

Circuit 2 (%)

Utility 0 0 0.0 0.0

Utility 1 33 80.5 0.0

Utility 2 40 0.0 0.0

Utility 3 145 83.5 0.0

Utility 4 289 0.0 0.0

Refuse 5 361 0.0 13.0

Refuse 6 363 0.0 38.0

Refuse 7 373 0.0 53.0

Refuse 8 384 0.0 73.0

Refuse 9 388 0.0 0.0

Refuse 10 401 0.0 13.0

Refuse 11 403 0.0 38.0

Refuse 12 413 0.0 53.0

Refuse 13 424 0.0 73.0

Refuse 14 442 11.2 0.0

Refuse 15 468 29.3 0.0

Refuse 16 473 0.0 0.0

Refuse 17 486 11.2 0.0

Refuse 18 512 29.3 0.0

Refuse 19 517 0.0 0.0

Refuse 20 530 12.8 11.1

Refuse 21 532 12.8 38.2

Refuse 22 541 12.8 53.4

Refuse 23 550 12.8 73.5

Refuse 24 553 0.0 0.0

Refuse 25 566 12.8 11.1

Refuse 26 568 12.8 38.2

Refuse 27 577 12.8 53.4

Refuse 28 586 12.8 73.5

Refuse 29 589 0.0 0.0

Refuse 30 600 0.0 0.0

(b) Engine Dynamometer Evaluation

The engine test procedure we are proposing for hybrid evaluation involves

exercising the conventional engine and hybrid-engine system based on an engine testing 

strategy. The basis for the system control volume, which serves to determine the valid 

test article, will need to be the most accurate representation of real world functionality. 
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An engine test methodology would be considered valid to the extent the test is performed 

on a test article that does not mischaracterize criteria pollutant performance or actual 

system performance. Energy inputs should not be based on simulation data which is not 

an accurate reflection of actual real world operation. It is clearly important to be sure 

credits are generated based on known physical systems. This includes testing using 

recovered vehicle kinetic energy. Additionally, the duty cycle over which this enginehybrid system will be exercised must reflect the use of the application, while not 

promoting a proliferation of duty cycles which prevent a standardized basis for 

comparing hybrid system performance. The agencies are proposing the use of the Heavy 

Duty Engine FTP cycle for evaluation of hybrid vehicles, which is the same test cycle 

proposed for engines used in vocational vehicles. For powerpack testing, which includes 

the engine and hybrid systems in a pre-transmission format, the engine based testing is 

applicable for determination of brake-specific emissions benefit versus the engine 

standard. For post-transmission powertrain systems and vehicles, the comparison 

evaluation based on the Improvement Factor and the T.E.S.T. result based on a vehicle 

drive trace in a powertrain test cell or chassis dynamometer test cell seem to accurately 

reflect the performance improvements associated with these test configurations. It is 

important that introduction of clean technology be incentivized without compromising 

the program intent of real world improvements in GHG and fuel consumption 

performance. The agencies seek comments on the most appropriate test procedures to 

accurately reflect the performance improvement associated with hybrid systems tested 

using these or other protocols. 

(3) Innovative Technology Credits

NHTSA and EPA are proposing an optional credit opportunity intended to apply

to new and innovative technologies that reduce fuel consumption and CO2 emissions, but 

for which the reduction benefits are not captured over the test procedure used to 

determine compliance with the standards (i.e., the benefits are “off-cycle”). Eligible 

innovative technologies would be those that are relatively newly introduced in one or 

more vehicle models, but that are not yet implemented in widespread use in the heavyduty fleet. EPA and NHTSA would not approve credits for technologies that are not 

innovative or novel approaches to reducing greenhouse gas emissions and fuel 

consumption. Further, any credits for these off-cycle technologies would need to be 

based on real-world fuel consumption and GHG reductions that can be measured with 

verifiable test methods, and representing driving conditions typical of the vehicle 

application.

We would not consider technologies to be eligible for these credits if the 

technology has a significant impact on CO2 emissions over the primary test cycles. 

Rather, we are focused for purposes of Innovative Technology credits on technologies 

that are not nearly so well developed and understood, and that we are not prepared to 

require their utilization to meet the CO2 standards. However, EPA and NHTSA are 

aware of some emerging and innovative technologies and concepts in various stages of 

development with CO2 reduction potential that might not be adequately captured on the 

proposed certification test cycles, and we believe that some of these technologies might 

merit some additional CO2 and fuel consumption credit for the manufacturer. Examples 
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include adaptive cruise control, electric engine battery, and active aerodynamics. We 

believe it would be appropriate to provide an incentive to encourage the introduction of 

these types of technologies and that a credit mechanism is an effective way to do so. This 

optional credit opportunity would be available through the 2018 model year. 

We are proposing that manufacturers quantify CO2 and fuel consumption 

reductions associated with the use of the off-cycle technologies such that the credits 

could be applied based on the proposed metrics (such as g/mile and gal/100 mile for 

pickup trucks, g/ton-mile and gal/1000 ton-mile for tractors and vocational trucks, and 

g/bhp-hr and gal/100 bhp-hr for engines). EPA and NHTSA request comments whether 

credits generated using innovative technologies should be fungible across vehicle and 

engine categories or restricted to within the category where the credit was generated. 

Credits would have to be based on real additional reductions of CO2 emissions and fuel 

consumption and would need to be quantifiable and verifiable with a repeatable 

methodology. Such submissions of data should be submitted to EPA and NHTSA, and 

will be subject to public scrutiny. We propose that the technologies upon which the 

credits are based would be subject to full useful life compliance provisions, as with other 

emissions controls. Unless the manufacturer can demonstrate that the technology would 

not be subject to in-use deterioration over the useful life of the vehicle, the manufacturer 

would have to account for deterioration in the estimation of the credits in order to ensure 

that the credits are based on real in-use emissions reductions over the life of the vehicle.

As discussed below, we are proposing a two-tiered process for demonstrating the 

CO2 and fuel consumption reductions of an innovative and novel technology with 

benefits not captured by the proposed test procedures. First, a manufacturer of heavy 

duty pickup trucks and vans would determine whether the benefit of the technology could 

be captured using the 5-cycle methodology currently used to determine light duty vehicle 

fuel economy label values. EPA established the 5-cycle test methods to better represent 

real-world factors impacting fuel economy, including higher speeds and more aggressive 

driving, colder temperature operation, and the use of air conditioning. If this 

determination is affirmative, the manufacture would follow the protocol laid out below 

and in the proposed regulations. If the heavy duty pickup truck and van manufacturer 

found that the technology was such that the benefit was not adequately captured using the 

5-cycle approach, then the manufacturer would have to develop a robust methodology, 

subject to EPA and NHTSA approval, to demonstrate the benefit and determine the 

appropriate CO2 and fuel consumption credit. The heavy-duty engine, combination

tractor, and vocational truck manufacturers would automatically opt for the second tier 

process and would develop a robust methodology to demonstrate the reductions.

(a) Technology Demonstration Using EPA 5-Cycle Methodology for Heavy Duty 

Pickup Truck and Van Manufacturers 

As noted above, the CO2 and fuel consumption reduction benefit of some 

innovative technologies could be demonstrated using the 5-cycle approach currently used 
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for EPA’s fuel economy labeling program for light duty vehicles. The 5-cycle 

methodology was finalized in EPA’s 2006 fuel economy labeling rule,166 which provides 

a more accurate fuel economy label estimate to consumers starting with 2008 model year 

vehicles. In addition to the FTP and HFET test procedures, the 5-cycle approach folds in 

the test results from three additional test procedures to determine fuel economy. The 

additional test cycles include cold temperature operation, high temperature, high 

humidity and solar loading, and aggressive and high-speed driving; thus these tests could 

be used to demonstrate the benefit of a technology that reduces CO2 and fuel 

consumption over these types of driving and environmental conditions. Using the test 

results from these additional test cycles collectively with the 2-cycle data provides a more 

precise estimate of the average fuel consumption and CO2 emissions of a vehicle for both 

the city and highway independently. A significant benefit of using the 5-cycle 

methodology to measure and quantify the CO2 and fuel consumption reductions is that the 

test cycles are properly weighted for the expected average U.S. operation, meaning that 

the test results could be used without further adjustments.

The use of these supplemental cycles may provide a method by which 

technologies not demonstrated on the baseline 2-cycles can be quantified. The cold 

temperature FTP can capture new technologies that improve the CO2 and fuel 

consumption performance of vehicles during colder weather operation. These 

improvements may be related to warm-up of the engine or other operation during the 

colder temperature. An example of such a new, innovative technology is a waste heat 

capture device that provides heat to the cabin interior, enabling additional engine-off 

operation during colder weather not previously enabled due to heating and defrosting 

requirements. The additional engine-off time would result in additional CO2 and fuel 

consumption reductions that otherwise would not have been realized without the heat

capture technology.

Certain new technologies may be able to use the high temperatures, humidity, and 

solar load of the SC03 test cycle to accurately measure their impact. An example of a 

new technology may be a refrigerant storage device that accumulates pressurized 

refrigerant during driving operation or uses recovered vehicle kinetic energy during 

deceleration to pressurize the refrigerant. Much like the waste heat capture device used 

in cold weather, this device would also allow additional engine-off operation while 

maintaining appropriate vehicle interior occupant comfort levels. Another example is 

glazed windows. This reflects sunlight away from the cabin so that the energy required 

to stabilize the cabin air to a comfortable level is decreased. The impact of these 

windows may be measureable on an SC03 test (with and without the window option). 

The US06 cycle may be used to capture innovative technologies designed to 

reduce CO2 emissions and fuel consumption during higher speed and more aggressive

acceleration conditions, but not reflected on the 2-cycle tests. . An example of this is an 

 

166 Fuel Economy Labeling of Motor Vehicles: Revisions to Improve Calculation of Fuel Economy 

Estimates; Final Rule (71 FR 77872, December 27, 2006)
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active aerodynamic technology. This technology recognizes the benefits of reduced 

aerodynamic drag at higher speeds and makes changes to the vehicle at those speeds. 

The changes may include active front or grill air deflection devices designed to redirect 

frontal airflow. Certain active suspension devices designed primarily to reduce 

aerodynamic drag by lowering the vehicle at higher speeds may also be measured on the 

US06 cycle. To properly measure these technologies on the US06, the vehicle would 

require unique load coefficients with and without the technologies. The different load 

coefficient (properly weighted for the US06 cycle) could effectively result in reduced 

vehicle loads at the higher speeds when the technologies are active. Similar to the 

previously discussed cycles, the results from the US06 test with and without the 

technology could then use the 5-cycle methodology to quantify CO2 reductions. 

If the 5-cycle procedures can be used to demonstrate the innovative technology, 

then the process would be relatively simple. The manufacturer would simply test 

vehicles with and without the technology installed or operating and compare results. All 

5-cycles would be tested with the technology enabled and disabled, and the test results 

would be used to calculate a combined city/highway CO2 and fuel consumption value 

with the technology and without the technology. These values would be compared to 

determine the amount of the credit; the combined city/highway CO2 or fuel consumption 

value with the technology operating would be subtracted from the combined 

city/highway CO2 or fuel consumption value without the technology operating to 

determine the gram per mile CO2 credit or gallon per mile fuel consumption credit. It is 

likely that multiple tests of each of the five test procedures would need to be performed in 

order to achieve the necessary strong degree of statistical significance of the credit 

determination results. This would have to be done for each model type for which a credit 

was being sought, unless the manufacturer could demonstrate that the impact of the 

technology was independent of the vehicle configuration on which it was installed. In 

this case, the agencies may consider allowing the test to be performed on an engine 

family basis or other grouping. At the end of the model year, the manufacturer would 

determine the number of vehicles produced subject to each credit amount and report that 

to the agencies in the final model year report. The gram per mile credit value determined 

with the 5-cycle comparison testing would be multiplied by the total production of 

vehicles subject to that value to determine the total number of credits. 

(b) Alternative Off-Cycle Credit Methodologies 

In cases where the benefit of a technological approach to reducing CO2 emissions 

and fuel consumption cannot be adequately represented using existing test cycles, EPA 

and NHTSA would review and approve as appropriate test procedures and analytical 

approaches to estimate the effectiveness of the technology for the purpose of generating 

credits. An alternative approach may be developed and submitted to EPA and NHSTA 

for approval. The demonstration program should be robust, verifiable, and capable of 

demonstrating the real-world emissions benefit of the technology with strong statistical 

significance. 

The CO2 and fuel consumption benefit of some technologies may be able to be 

demonstrated with a modeling approach, using engineering principles. The amount of 
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potential electrical power that the panel could supply could be modeled for average U.S. 

conditions and the units of electrical power translated to equivalent fuel energy or 

annualized CO2 emission rate reduction from the captured solar energy. The CO2

reductions from other technologies may be more challenging to quantify, especially if 

they are interactive with the driver, geographic location, environmental condition, or 

other aspect related to operation on actual roads. In these cases, manufacturers might 

have to design extensive on-road test programs. Any such on-road testing programs 

would need to be statistically robust and based on average U.S. driving conditions, 

factoring in differences in geography, climate, and driving behavior across the U.S. 

Whether the approach involves on-road testing, modeling, or some other 

analytical approach, the manufacturer would be required to present a proposed 

methodology to EPA and NHTSA. EPA and NHTSA would approve the methodology

and credits only if certain criteria were met. Baseline emissions and control emissions 

would need to be clearly demonstrated over a wide range of real world driving conditions 

and over a sufficient number of vehicles to address issues of uncertainty with the data. 

Data would need to be on a vehicle model-specific basis unless a manufacturer 

demonstrated model specific data was not necessary. Approval of the approach to 

determining a CO2 and fuel consumption benefit would not imply approval of the results 

of the program or methodology; when the testing, modeling, or analyses are complete the 

results would likewise be subject to EPA and NHTSA review and approval. The 

agencies believe that manufacturers could work together to develop testing, modeling, or 

analytical methods for certain technologies, similar to the SAE approach used for A/C 

refrigerant leakage scores.

The agencies request comments on the proposed approach for off-cycle emissions 

credits, including comments on how best to structure the program. EPA and NHTSA 

particularly request comments on how the case-by-case approach to assessing off-cycle 

innovative technology credits could best be designed, including ways to ensure the 

verification of real-world emissions benefits and to ensure transparency in the process of 

reviewing manufacturer’s proposed test methods.

(4) Air Conditioning Credit Option for Complete Pickup Truck and Van 

Manufacturers

EPA has previously offered GHG ABT credits for light-duty cars and trucks 

recognizing both direct and indirect emissions in the air conditioning system and its 

operation. The A/C systems in the large pickups and vans are very similar to the lightduty systems for which we have offered GHG ABT programs. They share systems and 

components for A/C operation that are used in Light-Duty cars and trucks. Class 2b/3 

Light-Heavy-duty vehicles are similar in make and payload capacity that makes it 

reasonable to extend GHG ABT credits for that category. 

The indirect effect of A/C emissions of CO2 and fuel consumption resulting from 

increased emissions due to running the vehicle with the A/C operating are expected to be 

equivalent to what is generated for light-duty vehicles; 46 g/mile (HFET) and 86 g/mile 

(FTP). The A/C reduction technologies currently used in light-duty can also be used for 
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light-heavy duty vehicles. Light-duty vehicles taking part in the light-duty A/C GHG 

ABT program experienced a 24% reduction in GHG emissions and we would expect to 

see a similar improvement in light-heavy duty vehicles. Some of the technological 

improvements used in the light-duty context and available to light-heavy-duty

manufacturers include, but are not limited to; efficient compressors and other 

components, forced recirculation, reduced reheat, and improved blower and fan controls. 

We believe these direct and indirect A/C improvements will require minimal additional 

cost for light-heavy duty manufacturers and have been shown to reduce the GHG 

emissions and fuel consumption from light-duty vehicles.

(5) Alternative Fuel Vehicle Adjustment for Class 2b/3 Complete Vehicles

The agencies currently do not propose a program for flex fuel vehicles (FFV) or alternative fuel 

vehicles. However, we are accepting comment on whether to provide a flexibility program similar to the 

program we currently offer for light-duty FFV vehicles.

] 

V. NHTSA and EPA Proposed Compliance, Certification, and 

Enforcement Provisions

A. Overview

(1) Proposed Compliance Approach 

This section describes EPA’s and NHTSA’s proposed program to ensure 

compliance with EPA’s proposed emission standards for carbon dioxide (CO2), nitrous 

oxide (N2O), and methane (CH4) and NHTSA’s proposed fuel consumption standards, as 

described in section II. To achieve the goals projected in this proposal, it is important for 

the agencies to have an effective and coordinated compliance program for our respective 

standards. As is the case with the Light-Duty GHG and CAFE program, the proposed 

compliance program for heavy-duty vehicles and engines has two central priorities. (1) 

to address the agencies’ respective statutory requirements; and (2) to streamline the 

compliance process for both manufacturers and the ageneies by building on existing 

practice wherever possible, and by structuring the program such that manufacturers can 

use a single data set to satisfy the requirements of both agencies. It is also important to 

consider the provisions of EPA’s existing criteria pollutant program in the development 

of the approach used for heavy-duty certification and compliance. The existing EPA 

heavy-duty highway engine emissions program has an established infrastructure and 

methodology that would allow effective integration with this proposed GHG and fuel 

consumption program, without needing to create new unique processes in many

instances. The compliance program would also need to address the importance of the 

impact of new control methods for heavy-duty vehicles as well as other control systems 

and strategies that may extend beyond the traditional purview of the criteria pollutant 

program. 

The proposed heavy-duty compliance program would use a variety of 

mechanisms to conduct compliance assessments, including preproduction certification 
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and postproduction, in-use monitoring once vehicles enter customer service. Specifically, 

the agencies are establishing a compliance program that utilizes existing EPA testing 

protocols and certification procedures. Under the provisions of this program, 

manufacturers would have significant opportunity to exercise implementation flexibility, 

based on the program schedule and design, as well as the credit provisions that exist in 

the program for conventional and hybrid power systems. Today’s action also discusses a 

process to foster the use of innovative technologies, not yet contemplated in the current 

certification process. EPA would continue to conduct compliance preview meetings 

which provide the Agency an opportunity to review a manufacturer’s new product plans 

and ABT projections. Given the nature of the proposed compliance program which 

would involve both engine and vehicle compliance for some categories, it would be 

necessary for manufacturers to begin pre-certification meetings with EPA early enough to 

address issues of certification and compliance for both integrated and non-integrated 

product offerings. 

Based on feedback EPA received during the Light-Duty GHG comment period, 

EPA would seek to ensure transparency in the compliance process. In addition to 

providing information in published reports annually regarding the status of credit 

balances and compliance on an industry basis, EPA and NHTSA seek comment on 

additional strategies for providing information useful to the public regarding industry’s 

progress toward reducing GHG emissions and fuel consumption from this sector while 

protecting sensitive business information.

(a) Heavy-Duty Pickup Trucks and Vans 

The proposed compliance regulations (for certification, testing, reporting, and 

associated compliance activities) for heavy-duty pickup trucks and vans closely track 

both current practices and the recently adopted greenhouse gas regulations for light-duty 

vehicles and trucks. Thus they would be familiar to manufacturers. EPA already

oversees testing, collects and processes test data, and performs calculations to determine 

compliance with both CAFE and CAA standards for Light-Duty. For Heavy-Duty

products that closely parallel light-duty pick-ups and vans, under a coordinated approach, 

the compliance mechanisms for both programs for NHTSA and EPA would be consistent 

and non-duplicative for GHG pollutant standards and fuel consumption requirements. 

Vehicle emission standards established under the CAA apply throughout a vehicle’s full 

useful life. 

Under EPA existing criteria pollutant emission standard program for heavy-duty

pickup trucks and vans, vehicle manufacturers certify a group of vehicles called a test 

group. A test group typically includes multiple vehicle lines and model types that share 

critical emissions-related features. The manufacturer generally selects and tests a single 

vehicle to represent the entire test group for certification purposes. The test vehicle is the 

one expected to be the worst case for the emission standard at issue. Emissions from the 

test group are assigned as the value for the entire test group. However, the compliance 

program in the recent GHG regulations for light-duty vehicles requires that 

manufacturers perform addition testing. This same approach would be applied to the 

category of heavy-duty vehicles known as complete pickups and vans.
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(b) Heavy-duty Engines

Heavy-duty engine certification and compliance for traditional criteria pollutants 

has been established by EPA since 1988. In developing a program to address GHG 

pollutants, it is important to build upon the infrastructure for certification and compliance 

that exists today, while developing additional tools to address GHG pollutants which has 

control strategies which extend beyond those of traditional criteria pollutants. In so 

doing, the Agency is proposing to continue its current engine based strategy to effect 

control of GHG pollutants, as well as adding new strategies to address vehicle design 

which impact GHG emissions. The traditional engine approach would largely match the 

existing gaseous pollutant control strategy. This would allow the basic tools for 

certification and compliance, which have already been developed and implemented, to be 

expanded for carbon dioxide, methane, and nitrous oxide. Engines with similar 

emissions control technology may be certified in engine families, as with criteria 

pollutants. 

The proposed approach for certification would follow the current process which 

would require manufacturer submission of certification applications, approval of the 

application, and receipt of the certificate of conformity prior to introduction into 

commerce of any engines. EPA proposes the certificate of conformity be a single 

document that would be applicable for both criteria pollutants and greenhouse gas 

pollutants. 

(c) Class 7/8 Combination Tractors and Class 2b-8 Vocational Vehicles

Currently, EPA does not directly regulate exhaust emissions from most heavyduty vehicles. Instead, a compliance assessment of the engine is undertaken as described 

above. Vehicle manufacturers installing certified engines are required to do so in a 

manner that maintains all functionality of the emission control system. While no process 

exists for certifying heavy-duty vehicles other than light-heavy duty pickups and vans, a 

process similar to the one used for heavy-duty engines can be applied to the vehicles.

We are proposing a standard certification program for heavy-duty vehicles. 

Manufacturers would divide their vehicles into families and submit an application for 

certification for each family. However, the demonstration of compliance would not 

require emission testing, but would instead involve a computer simulation model, 

[TEST]. This modeling tool uses a combination of manufacturer-specified and EPAprovided vehicle parameters to develop a vehicle model. This model is then exercised 

over certain drive cycles. With today’s action, EPA is proposing the duty cycles over 

which Class 7 and 8 combination tractors will be exercised to are: 65 mile per hour 

steady state cruise cycle, the 55 mile per hour steady state cruise cycle, and the ARB 

transient cycle. Additional details regarding these duty cycles will be addressed in 

section D(1)(b) of this chapter. Over each duty cycle, the simulation tool will return the 

expected CO2 emissions, in g/ton-mile and gal/1000 ton-mile, which can then be 

compared to the emission standard.
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B. Heavy-duty Pickup Trucks and Vans

(1) Proposed Compliance Approach

EPA and NHTSA are proposing new emission standards to control greenhouse 

gases (GHGs) from heavy-duty trucks between a 8,500 and 14,000 gross vehicle weight 

rating that are not already covered under the light-duty truck and medium duty passenger 

vehicle GHG standards already set forth in the “Light-Duty Vehicle Greenhouse Has 

Emissions Standards and Corporate Average Fuel Economy Standard; Final Rule” as 

published in the Federal Register on Friday May 7, 2010. In this section “trucks” now 

refers to heavy-duty pickup trucks and vans between 8,500 and 14,000 pounds not 

already covered under the above light-duty rule. 

First, EPA is proposing fleet average emission standards for carbon dioxide (CO2)

on a gram per mile (g/mile) basis and NHTSA is proposing fuel consumption standards 

on a gallon per mile (gal/mile) basis that would apply separately to a manufacturer’s fleet 

of trucks from both the manufacturer’s fleet of light-duty vehicles and heavy-duty

vehicles with a GVWR above 14,000 pounds. CO2 is the primary pollutant resulting 

from the combustion of vehicular fuels, and the amount of CO2 emitted is highly 

correlated to the amount of fuel consumed. EPA and NHTSA are providing auto 

manufacturers with the opportunity to earn credits toward the fleet-wide average CO2 and 

fuel consumption standards for improvements to air conditioning system efficiency that 

reduce the load on the engine and thereby reduce CO2 emissions and fuel consumption. 

Separately, EPA is setting standards to control the leakage of HFCs from air conditioning 

systems. In addition, the EPA is proposing separate emissions standards for two other 

GHG pollutants: methane (CH4) and nitrous oxide (N20). CH4 and N2O emissions relate 

closely to the design and efficient use of emission control hardware (i.e., catalytic 

converters). The standards for CH4 and N2O would be set as a cap that would limit 

emissions increases and prevent backsliding from current emission levels. 

Previously, complete vehicles with a Gross Vehicle Weight Rating of 8,500-

14,000 pounds could be certified according to 40 CFR part 86, section S. These heavyduty chassis certified vehicles were required to pass emissions on both the FTP and 

HFET, also known as the Federal Test Procedure and the Highway Fuel Economy Test, 

for most 50 state certificates of compliance167. These proposed rules would use the same 

testing procedures already required for certification, namely the FTP and the HFET. 

Using the data from these two tests, the EPA could apply attribute based standards for 

CO2 emissions. The attribute upon which the CO2 standard would be based will be a 

function of vehicle payload, vehicle towing capacity and two- wheel vs four-wheel drive 

configuration as discussed in chapter 2 C (1)(c) of this notice. This attribute based 

standard would be a manufacturer fleet standard and would be subject to an average 

banking and trading scheme similar to the light-duty GHG rule. This proposal would 

require nearly all heavy-duty trucks between 8,500 and 14,000 gross vehicle weight 

rating that are not already covered under the light-duty truck and medium duty passenger 

 

167

 50-state as opposed to ???? California? 49-state?
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vehicle GHG standards be tested on a chassis dynamometer. This requirement would 

apply based on whether the vehicle manufacturer sold the vehicle as a complete or nearly 

complete vehicle.168 Manufacturers would be allowed to exclude vehicles they sell to 

secondary manufacturers without cabs (often known as rolling chassis), as well as a very

small number of vehicles sold with cabs. Specifically, a manufacturer could engine 

certify up to two percent of its vehicles with complete cabs, or up to 2,000 vehicles if its 

total sales in this category was less than 100,000.To the extent manufacturers are allowed 

to engine certify for criteria pollutant (non GHG) requirements today, they would also be 

allowed to do so under the proposed regulations.

(a) Certification Process

CAA section 203(a)(1) prohibits manufacturers from introducing a new motor 

vehicle into commerce unless the vehicle is covered by an EPA-issued certificate of 

conformity. Section 206(a)(1) of the CAA describes the requirements for EPA issuance 

of a certificate of conformity, based on a demonstration of compliance with the emission 

standards established by EPA under section 202 of the Act. The certification 

demonstration requires emission testing, and must be done for each model year.169

Under Tier 2 heavy duty chassis certification and other EPA emission standard 

programs, vehicle manufacturers certify a group of vehicles called a test group. A test 

group typically includes multiple vehicle car lines and model types that share critical 

emissions-related features.170 The manufacturer generally selects and tests one vehicle to 

represent the entire test group for certification purposes. The test vehicle is the one 

expected to be the worst case for the emission standard at issue. 

EPA requires the manufacturer to make a good faith demonstration in the 

certification application that vehicles in the test group will both 1) comply throughout 

their useful life within the emissions bin assigned, and 2) contribute to fleetwide 

compliance with the applicable emissions standards when the year is over. EPA issues a 

certificate for the vehicles included in the test group based on this demonstration, and 

includes a condition in the certificate that if the manufacturer does not comply with the 

fleet average, then production vehicles from that test group will be treated as not covered 

by the certificate to the extent needed to bring the manufacturer’s fleet average into 

compliance with the applicable standards. 

The certification process often occurs several months prior to production and 

manufacturer testing may occur months before the certificate is issued. The certification 

process for the Tier 2 heavy duty chassis program is an efficient way for manufacturers to 

conduct the needed testing well in advance of certification, and to receive the needed 

 

168 The proposed regulations would use the term “cab-complete vehicle” to refer to incomplete vehicles 

sold with complete cabs, but lacking a cargo carrying container.

169 CAA section 206(a)(1).

170 The specific test group criteria are described in 40 CFR § 86.1827-01, car lines and model types have 

the meaning given in 40 CFR § 86.1803-01.
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certificates in a time frame which allows for the orderly production of vehicles. The use 

of conditions on the certificate has been an effective way to ensure that manufacturers 

comply throughout their useful life and meet fleet standards. EPA has also adopted this 

approach as part of its LD GHG compliance program.

EPA is proposing to similarly condition each certificate of conformity for the 

GHG program upon a manufacturer's good faith demonstration of compliance with the 

manufacturer’s fleetwide average CO2 standard. The following discussion explains how 

EPA proposes to integrate the proposed vehicle certification program into the existing 

certification program.

(b) Certification Test Groups and Test Vehicle Selection

For heavy duty chassis certification to the criteria emission standards, 

manufacturers currently as mentioned above divide their fleet into "test groups" for 

certification purposes. The test group is EPA's unit of certification; one certificate is 

issued per test group. These groupings cover vehicles with similar emission control 

system designs expected to have similar emissions performance.171 The factors 

considered for determining test groups include Gross Vehicle Weight, combustion cycle, 

engine type, engine displacement, number of cylinders and cylinder arrangement, fuel 

type, fuel metering system, catalyst construction and precious metal composition, among 

others. Vehicles having these features in common are generally placed in the same test 

group.172

EPA is proposing to retain the current test group structure for 2b and 3 chassis 

certified trucks in the certification requirements for CO2. At the time of certification, 

manufacturers would use the CO2 emission level from the Emission Data Vehicle as a 

surrogate to represent all of the models in the test group. However, following 

certification further testing would generally be allowed for compliance with the fleet 

average CO2 standard as described below. EPA's issuance of a certificate would be 

conditioned upon the manufacturer's subsequent model level testing and attainment of the 

actual fleet average. Under the current Tier 2 program, complete heavy duty Otto-cycle 

vehicles under 14000 pounds Gross Vehicle Weight Rating are required to chassis 

certify.

173

 The current Tier 2 program allows complete heavy duty diesel vehicles under 

140000 pounds GVWR to optionally chassis certify.

174

 These proposed rules will now 

require all HD vehicles under 14000 pounds GVWR to chassis certify except as noted in 

section xx. 

EPA recognizes that the Tier 2 heavy duty chassis test group criteria do not 

necessarily relate to CO2 emission levels. For instance, while some of the criteria, such 

 

171 40 CFR § 86.1827-01.

172 EPA provides for other groupings in certain circumstances, and can establish its own test groups in cases 

where the criteria do not apply. 40 CFR § 86.1827-01(b), (c) and (d).

173 40 CFR § 86.1801-01(a)

174 40 CFR § 86.1863-07(a)
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as combustion cycle, engine type and displacement, and fuel metering, may have a 

relationship to CO2 emissions, others, such as those pertaining to the catalyst, may not. 

In fact, there are many vehicle design factors that impact CO2 generation and emission

but are not major factors included in EPA's test group criteria.175 Most important among 

these may be vehicle weight, horsepower, aerodynamics, vehicle size, and performance 

features. To remedy this, EPA is considering allowing manufacturers provisions similar 

to the LD GHG rule that would yield more accurate CO2 estimates than only using the 

test group emission data vehicle CO2 emissions. 

EPA believes that the current test group concept is appropriate for N20 and CH4

because the technologies that would be employed to control N2O and CH4 emissions 

would generally be the same as those used to control the criteria pollutants.

As just discussed, the “worst case” vehicle a manufacturer selects as the 

Emissions Data Vehicle to represent a test group under Tier 2 (40 CFR § 86.1828-01) 

may not have the highest levels of CO2 in that group. For instance, there may be a 

heavier, more powerful configuration that would have higher CO2, but may, due to the 

way the catalytic converter has been matched to the engine, actually have lower NOX, 

CO, PM or HC. Therefore, EPA is proposing to require a single Emission Data Vehicle 

that would represent the test group for both Tier 2 heavy duty chassis and CO2

certification. The manufacturer would be allowed to initially apply the Emission Data 

Vehicle’s CO2 emissions value to all models in the test group, even if other models in the 

test group are expected to have higher CO2 emissions. However, as a condition of the 

certificate, this surrogate CO2 emissions value would generally be replaced with actual, 

model-level CO2 values based on results from CAFE testing that occurs later in the model 

year or through the use of ADFEs. This model level data would become the official 

certification test results (as per the conditioned certificate) and would be used to 

determine compliance with the fleet average. Only if the test vehicle is in fact the worst 

case CO2 vehicle for the test group could the manufacturer elect to apply the Emission 

Data Vehicle emission levels to all models in the test group for purposes of calculating 

fleet average emissions. Manufacturers would be unlikely to make this choice, because 

doing so would ignore the emissions performance of vehicle models in their fleet with 

lower CO2 emissions and would unnecessarily inflate their CO2 fleet average. Testing at 

the model level would necessarily increase testing burden beyond the minimum Emission 

Data Vehicle testing. 

EPA requests comment regarding whether the Tier 2 heavy duty chassis test 

group can adequately represent CO2 emissions for certification purposes, and whether the 

Emission Data Vehicle's CO2 emission level is an appropriate surrogate for all vehicles in 

a test group at the time of certification, given that the certificate would be conditioned 

upon additional model level testing occurring during the year and that the surrogate CO2

emission values would be replaced with model-level emissions data from those tests. 

 

175 EPA noted this potential lack of connection between fuel economy testing and testing for emissions 

standard purposes when it first adopted fuel economy test procedures. See 41 FR at 38677 (Sept. 10, 

1976).
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Comments should also address EPA's desire to minimize the up-front pre-production

testing burden and whether the proposed efficiencies would be balanced by the 

requirement to test all model types in the fleet by the conclusion of the model year in 

order to establish the fleet average CO2 levels. 

There are two standards that the manufacturer would be subject to, the fleet 

average standard and the in-use standard for the useful life of the vehicle. Compliance 

with the fleet average standard is based on production weighted averaging of the test data 

that applies for each model, For each model, the in-use standard is set at 10% higher than 

the level used for that model in calculating the fleet average. The certificate covers both 

of these standards, and the manufacturer has to demonstrate compliance with both of 

these standards for purposes of receiving a certificate of conformity. The certification 

process for the in-use standard is discussed above. 

(c) Pre-Model Year (or Compliance Plan) Reporting

EPA and NHTSA are proposing that manufacturers submit a compliance plan for 

their entire fleet no later than two months prior to the certification of any test group in a 

given model year. Preferably, this compliance plan would be submitted at the 

manufacturer’s annual certification preview meeting, This preview meeting is typically 

held before the earliest date that the model year can begin. The earliest a model year can 

begin is January 2nd of the calendar year prior to the model year. This plan would include 

the manufacturer's estimate of its attribute-based standard, along with a demonstration of 

compliance with the standard based on projected model-level CO2 emissions and fuel 

consumption, and production estimates. This information would be similar to the 

information submitted to NHTSA and EPA in the pre-model year report required for 

CAFE compliance for light duty vehicles. Included in the compliance plan, 

manufacturers seeking to take advantage of air conditioning or other credit flexibilities 

would include these in their compliance demonstration. Similarly, the compliance 

demonstration would need to include a credible plan for addressing deficits accrued in 

prior model years. EPA and NHTSA would review the compliance plan for technical 

viability and conduct a certification preview discussion with the manufacturer. The 

agencies would view the compliance plan as part of the manufacturer's good faith 

demonstration, but understands that initial projections can vary considerably from the 

reality of final production and emission results. In addition, the compliance plan must be 

approved by the EPA Administrator prior to any certificate of compliance being issued. 

The agencies request comment on the proposal to evaluate manufacturer compliance 

plans prior to the beginning of model year certification.

(d) Demonstrating compliance with the proposed standards

(i) CO2 and Fuel Consumption Fleet Standards

 As noted, attribute-based CO2 standards result in each manufacturer having a 

fleet average CO2 standard unique to its heavy-duty truck fleet of GVWR 8500-14000 

pounds and that standard would be separate from the standard for passenger cars, lighttrucks, and other heavy-duty trucks. The standards depend on those attributes

corresponding to the relative capability, or “work factor”, of the vehicle models produced
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by that manufacturer. The proposed attributes used to determine the stringency of the 

CO2 standard are payload and towing capacity as described in chapter 2 C of this notice. 

Generally, fleets with a mix of vehicles with increased payloads or greater towing 

capacity (or utilizing four wheel drive configurations) would face numerically less 

stringent standards (i.e., higher CO2 grams/mile standards) than fleets consisting of less 

powerful vehicles. (However, the standards would be expected to equally challenging 

and achieve similar percent reductions.) Although a manufacturer’s fleet average 

standard could be estimated throughout the model year based on projected production

volume of its vehicle fleet, the final compliance values would be based on the final model 

year production figures. A manufacturer’s calculation of fleet average emissions at the 

end of the model year would be based on the production-weighted average emissions of 

each model in its fleet. The payload and towing capacity inputs used to determine 

manufacturer compliance with these proposed rules would be the advertised values.

The agencies propose to use the same general vehicle category definitions that are 

used in the current EPA HD chassis certification.176 The new vehicle category definitions 

differ slightly from the EPA definitions for Heavy-duty Vehicle definitions for the Tier 2 

program, as well as other EPA vehicle programs. Mainly, manufactures would be able to 

test, and possibly model, more configurations of vehicles that were historically in a given 

test group. Tier 2 requires the worst case configuration be tested for emissions 

certification. For HD chassis certification, this usually meant only testing the vehicle 

with the highest ALVW, roadload, and engine displacement within a given test group. 

This worst case configuration may only represent a small fraction of the test group 

production volume. By testing the worst case, albeit possibly small volume, vehicle 

configuration, the EPA had a reasonable expectation that all represented vehicles would 

pass the given emissions standards. Since CO2 standards are a fleet standard based on 

volume and payload, it may be in a manufacturer’s best interest to test multiple 

configurations within a given test group. The agencies are requesting comment on 

allowing the manufacturer to test as many configurations within a test group as the 

manufacturer requires in order to best represent the volumes of each configuration within 

that said test group. 

The agencies are proposing the use of Analytically Derived Fuel Economy similar 

to the ADFE provisions allowed for light duty with 40 CFR § 600.006-89 (e). This 

provision would allow EPA and NNTSA to accept analytical expressions to generate CO2

and fuel economy that have been approved in advance by the agencies. 

For model years 2014 through 2017, or earlier if early credits are sought, EPA is 

proposing the equation and parameter values below for assigning a CO2 level to an 

individual vehicle’s relevant attributes. These CO2 values would be production weighted 

to determine each manufacturer’s fleet average. Each parameter would change on an 

annual basis, resulting in the annual increase in stringency. For the function used to 

describe the proposed standard, see section II C of this notice 

 

176 40 CFR § 86.1816-05
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(ii) CO2 In-Use Standards

Section 202(a)(1) of the CAA requires emission standards to apply to vehicles 

throughout their statutory useful life, see Section II.B. The useful life requirement for 

this proposal is 10 years or 120,000 miles.

Currently, EPA regulations require manufacturers to conduct in-use testing as a 

condition of certification for heavy-duty trucks between a 8,500 and 14,000 gross vehicle 

weight tht are chassis certified. The vehicles are tested to determine the in-use levels of 

criteria pollutants when they are in their first and third years of service. This testing is 

referred to as the In-Use Verification Program (IUVP) testing, which was first 

implemented as part of EPA’s CAP 2000 certification program.177 

EPA is requesting comment on applying the same In-Use program already set 

forth in the “Light-Duty Vehicle Greenhouse Has Emissions Standards and Corporate 

Average Fuel Economy Standard; Final Rule” as published in the Federal Register on 

Friday May 7, 2010 to Heavy Duty Pick Ups and Vans. The In-Use Verification Program 

for Heavy Duty Pick Ups and Vans would follow the same general provisions of the light 

duty program in regard to testing, vehicle selection, and reporting.

(e) Cab-Chassis Vehicles and Complete Class 4 Vehicles

As discussed in Section I.C(2)(a), we are proposing to include most cab-chassis 

Class 2b/3 vehicles in the complete Class 2b/3 program. Because their numbers are 

relatively small, and to reduce the testing and compliance tracking burden to 

manufacturers, we would treat these vehicles as equivalent to the complete van or truck 

product they are derived from. The manufacturer would determine which complete 

vehicle configuration it produces most closely matches the cab-chassis product leaving its 

facility, and would include each of these cab-chassis vehicles in the fleet averaging 

calculations as though it were identical to the corresponding complete vehicle.

Any in-use testing of these vehicles would do likewise, with loading of the tested 

vehicle to a total weight equal to the ALVW of the corresponding complete vehicle 

configuration. If the secondary manufacturer had altered or replaced any vehicle 

components in a way that would substantially affect CO2 emissions from the tested 

vehicle, the OEM could request that EPA not test the vehicle or invalidate a test result. 

Secondary (finisher) manufacturers would not be subject to requirements under this 

provision, other than to comply with anti-tampering regulations. However, if they

modify vehicle components in such a way that GHG emissions and fuel consumption are 

 

177 64 FR 23906, May 4, 1999. 
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substantially affected, they become manufacturers subject to the standards under this 

proposal.

We realize that this approach does not capture the likely loss of aerodynamic 

efficiency involved in converting these vehicles from standard pickup trucks or vans to 

ambulances and the like, and thus it could assign them lower GHG emissions and fuel 

consumption than they deserve. However, we feel that this approach strikes a fair 

balance between the alternatives—grouping these vehicles with vocational trucks subject 

only to engine standards and tire requirements, or creating a complex and burdensome 

program that forces OEMs to track, and perhaps control, a plethora of vehicle 

configurations they currently do not manage. We request comment on this proposed 

provision and any suggestions for ways to improve it.

(2) Proposed Labeling Provisions

Vehicles in the 2B & 3 categories currently have vehicle emission control 

information labels (VECI) showing compliance with criteria pollutant standards, similar 

to ECIs for engines. As with engines, we believe this label is sufficient, assuming minor 

modifications may be needed for CO2 FELs if ABT is used.

(3) Other Certification Issues

(a) Carryover/Carry Across Certification Test Data

EPA’s proposed certification program for vehicles allows manufacturers to carry

certification test data over and across certification testing from one model year to the 

next, when no significant changes to models are made. EPA will also apply this policy to 

CO2, N2O and CH4 certification test data. 

(b) Compliance Fees

The CAA allows EPA to collect fees to cover the costs of issuing certificates of 

conformity for the classes of vehicles and engines covered by this proposal. On May 11, 

2004, EPA updated its fees regulation based on a study of the costs associated with its 

motor vehicle and engine compliance program (69 FR 51402). At the time that cost study

was conducted the current rulemaking was not considered. 

At this time the extent of any added costs to EPA as a result of this proposal is not 

known. EPA will assess its compliance testing and other activities associated with the 

rule and may amend its fees regulations in the future to include any warranted new costs.

C. Heavy-Duty Engines

(1) Proposed Compliance Approach

Section 203 of the Clean Air Act requires that all motor vehicles and engines sold 

in the United States to carry a certificate of conformity issued by the US EPA. For 

heavy-duty engines, this certifies that the engine meets all requirements as set forth in the 
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regulations (40 CFR Part 86, Subpart N, for criteria pollutants) including the requirement 

that the engine be compliant with emission standards. This demonstration is completed 

through emission testing as well as durability testing to determine the level of 

deterioration throughout the useful life of the engine. In addition to compliance with 

emission standards, manufacturers are also required to warrant their products against 

emission defects, and demonstrate that a service network is in place to correct any such 

conditions. The engine manufacturer also bears responsibility in the event that an 

emission-related recall is necessary. Finally, the engine manufacturer is responsible for 

tracking and ensuring correct installation of any emission related components installed by

a second party (i.e. vehicle manufacturer). We believe this compliance structure is also 

valid for administering these proposed GHG regulations for heavy-duty engines.

(a) Certification Process

In order to obtain a certificate of conformity, engine manufacturers must complete 

a compliance demonstration, normally consisting of test data from relatively new (lowhour) engines as well as supporting documentation, showing that their product meets 

emission standards and other requirements in the CFR. To account for aging effects, 

low-hour test results are coupled with testing-based deterioration factors (DFs), which 

provide a ratio (or offset) of end-of-life emissions to low-hour emissions for each 

pollutant being measured. These factors are then applied to all subsequent low-hour test 

data points to predict the emissions behavior at the end of the useful life. 

For purposes of this compliance demonstration and certification, engines with 

similar engine hardware and emission characteristics throughout their useful life may be 

grouped together in engine families, consistent with current criteria-pollutant certification 

procedures. Examples of such characteristics are the combustion cycle, aspiration 

method, and aftertreatment system. Under this system, the worst-case engine (“parent 

rating”) is selected based on having the highest fuel feed per engine stroke, and all 

emissions testing is completed on this model. All other models within the family (“child 

ratings”) are expected to have emissions at or below the parent model and therefore in 

compliance with emission standards. Any engine within the family can be subject to 

selective enforcement audits (SEAs), in-use, confirmatory, or other compliance testing.

We are proposing to continue to use this approach for the selection of the worstcase engine (“parent rating”) for fuel consumption and GHG emissions as well. We 

believe this is appropriate because this worst case engine configuration would be 

expected to have the highest in-use fuel consumption and GHG emissions within the 

family. We note that lower engine ratings contained within this family would be 

expected to have a higher fuel consumption rate when measured over the Federal Test 

Procedures and expressed in terms of fuel consumption per brake horsepower hour. This 

higher fuel consumption rate is misleading in the context of comparing engines within a 

single engine family. This seeming contradiction can be most easily understood in terms 

of an example. For a typical engine family a top rating could be 500 horsepower with a 

number of lower engine ratings down to 400 horsepower or lower included within the 

family. When installed in identical trucks the 400 and 500 horsepower engines would be 

expected to operate identically when the demanded power from the engines is 400 
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horsepower or less. So in the case where in-use driving never included acceleration rates 

leading to horsepower demand greater than 400 horsepower, the two trucks with the 400 

and 500 horsepower engines would give identical fuel consumption and GHG 

performance. When the desired vehicle acceleration rates were high enough to require 

more than 400 horsepower, the 500 horsepower truck would accelerate faster than the 

400 horsepower truck resulting in higher average speeds and higher fuel consumption and 

GHG emissions measured on a per mile or per ton-mile basis. Hence, the higher rated 

engine family would be expected to have the highest in-use fuel consumption and CO2

emissions. 

The reason that the lower engine ratings appear to have worse fuel consumption 

relates to our use of a brake specific work metric. The brake specific metric measures 

power produced from the engine and delivered to the vehicle ignoring the parasitic work 

internal to the engine to overcome friction and air pumping work within the engine. The 

fuel consumed and GHG emissions produced to overcome this internal work and to 

produce useful (brake) work are both measured in the test cycle but only the brake work 

is reflected in the calculation of the fuel consumption rate. This is desirable in the 

context of reducing fuel consumption as this approach rewards engine designs that 

minimize this internal work through better engine designs. The less work that is needed 

internal to the engine, the lower the fuel consumption will be. If we included the 

parasitic work in the calculation of the rate, we would provide no incentive to reduce 

internal friction and pumping losses. However, when comparing two engines within the 

very same family with identical internal work characteristics, this approach gives a 

misleading comparison between two engines as described above. This is the case 

because both engines have an identical fuel consumption rate to overcome internal work 

but different rates of brake work with the higher horsepower rating having more brake 

work because the test cycle is normalized to 100 percent of the engine’s rated power. 

The fuel consumed for internal work can be thought of as a fixed offset identical between 

both engines. When this fixed offset is added to the fuel consumed for useful (brake) 

work over the cycle, it increases the overall fuel consumption (the numerator in the rate) 

without adding any work to the denominator. This fixed offset identical between the two 

engines has a bigger impact on the lower engine rating. In the extreme this can be seen 

easily. As the engine ratings decrease and approach zero, the brake work approaches 

zero and the calculated brake specific fuel consumption approaches infinity. For these 

reasons, we are proposing that the same selection criteria, as outlined in 40 CFR Part 86, 

Subpart N, be used to define a single engine family designation for both criteria pollutant 

and GHG emissions. Further, we are proposing that for fuel consumption and CO2

emissions only any selective enforcement audits (SEAs), in-use, confirmatory, or other 

compliance testing will be limited to the parent rating for the family. This approach is 

being contemplated for administrative convenience at this time and we seek comments on 

alternatives to address compliance testing. Consistent with the current regulations, 

manufacturers may electively subdivide a grouping of engines which would otherwise 

meet the criteria for a single family if they have evidence that the emissions are different 

over the useful life. 

The Agency utilizes a 12-digit naming convention for all mobile-source engine 

families (and test groups for vehicles). This convention is also shared by the California 
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Air Resources Board which allows manufacturers to potentially use a single family name 

for both EPA and CARB certification. Of the 12 digits, 9 are EPA-defined and provide 

identifying characteristics of the engine family. The first digit represents the model year, 

through use of a predefined code. For example, “A” corresponds to the 2010 model year 

and “B” corresponds to the 2011 model year. The 5th position corresponds to the industry 

sector code, which includes such examples as light-duty vehicle (V) and heavy-duty 

diesel engines (H). The next three digits are a unique alphanumeric code assigned to each 

manufacturer by EPA. The next four digits describe the displacement of the engine; the 

units of which are dependent on the industry segment and a decimal may be used when 

the displacement is in liters. For engine families with multiple displacements, the largest 

displacement is used for the family name. For on-highway vehicles and engines, the 

tenth character is reserved for use by CARB. The final characters (including the 10th

character in absence of CARB guidance) left to the manufacturer to determine, such that 

the family name forms a unique identifying characteristic of the engine family.

This convention is well understood by the regulated industries, provides sufficient 

detail, and is flexible enough to be used across a wide spectrum of vehicle and engine 

categories. In addition, the current harmonization with other regulatory bodies reduces 

complications for affected manufacturers. For these reasons, we are not proposing any 

major changes to this naming convention for this proposal. There may be additional 

categories defined for the 5th character to address heavy-duty vehicle test groups, 

however that will be discussed later.

As with criteria pollutant standards, the heavy-duty diesel regulatory category is 

subdivided into three regulatory subcategories, depending on the GVW of the vehicle in 

which the engine will be used. These regulatory subcategories are defined as lightheavy-duty diesel (LHDD), medium heavy-duty diesel (MHDD), and heavy heavy-duty 

diesel (HHDD). All heavy-duty gasoline engines (HDG) are grouped into a single 

subcategory. Each of these regulatory subcategories are expected to be in service for 

varying amounts of time, so they each carry different regulatory useful lives. For this 

reason, expectations for demonstrating useful life compliance differ by subcategory, 

particularly as related to deterioration factors.

Light heavy-duty diesel engines (and all gasoline heavy-duty engines) have the 

same regulatory useful life as a light-duty vehicle (110,000 miles), which is significantly 

shorter than the other heavy-duty regulatory subcategories. Therefore, we believe it is 

appropriate to maintain commonality with the light-duty GHG rule. During the lightduty GHG rulemaking, the conclusion was reached that no significant deterioration 

would occur over the useful life. Therefore, EPA is proposing to specify that 

manufacturers would use assigned DFs for CO2 and the values would be zero (for 

additive DFs) and one (for multiplicative DFs). EPA is interested in data that addresses 

this issue.

For the medium heavy-duty and heavy heavy-duty diesel engine segments, the 

regulatory useful lives are significantly longer (185,000 and 435,000 miles, respectively). 

For this reason, the Agency is not convinced that engine/aftertreatment wear will not 

have a negative impact on GHG emissions. To address useful life compliance for MHDD 
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and HHDD engines certified to GHG standards, we believe the criteria pollutant 

approach for developing DFs is appropriate. Using CO2 as an example, many of the 

engine deterioration concerns previously identified will affect CO2 emissions. Reduced 

compression, as a result of wear, will cause higher fuel consumption and increase CO2

production. In addition, as aftertreatment devices (ATDs) age (primarily particulate 

traps), regeneration events may become more frequent and take longer to complete. Since 

regeneration commonly requires an increase in fuel rate, CO2 emissions would likely

increase as well. Finally, any changes in EGR levels will affect heat release rates, peak 

combustion temperatures, and completeness of combustion. Since these factors could 

reasonably be expected to change fuel consumption, CO2 emissions would be expected to 

change accordingly. 

HHDD engines may also require some degree of aftertreatment maintenance 

throughout their useful life. For example, one major heavy-duty engine manufacturer 

specifies that their diesel particulate filters be removed and cleaned at intervals between 

200,000 and 400,000 miles, depending on the severity of service. Another major engine 

manufacturer requires DPF service at 300,000 miles. This maintenance or lack thereof if 

service is neglected, could have serious negative implications to CO2 emissions. In

addition, there may be emissions-related warranty implications for manufacturers to 

ensure that if rebuilding or specific emissions related maintenance is necessary, it will 

occur at the prescribed intervals. Therefore, it is impetrative that manufacturers are 

detailed in their maintenance instructions. The Agency currently seeks public comment 

on how to properly address this issue. 

Lean-NOX aftertreatment devices may also facilitate GHG reductions by allowing 

engines to run with higher engine-out NOX levels in exchange for more efficient 

calibrations. In most cases, these aftertreatment devices require a consumable reductant, 

such as diesel exhaust fluid (DEF), which requires periodic maintenance by the vehicle 

operator. Without such maintenance, the emission control system may be compromised 

and compliance with emission standards may be jeopardized. Such maintenance is 

considered to be critical emission related maintenance and manufacturers must therefore 

demonstrate that it is likely to be completed at the required intervals. One example of 

such a demonstration are engine power derate strategies that will limit engine power or 

vehicle speed in absence of this required maintenance.

If the manufacturer determines that maintenance is necessary on critical emissionrelated components within the useful life period, they must have a reasonable basis for 

ensuring that this maintenance will be completed as scheduled. This includes any

adjustment, cleaning, repair, or replacement of critical emission-related components. 

Typically, the Agency has only allowed manufacturers to schedule such maintenance if 

the manufacturer can demonstrate that the maintenance is reasonably likely to be done at 

the recommended intervals. This demonstration may be in the form of survey data 

showing at least 80% of in-use engines get the prescribed maintenance at the correct 

intervals. Another possibility is to provide the maintenance free of charge. We see no 

reason to depart from this approach for GHG-related critical emission-related 

components; however the Agency welcomes commentary on this approach.
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(b) Demonstrating compliance with the proposed standards

(i) CO2 Standards

As mentioned previously, demonstrating compliance over the useful life generally 

consists of low-hour testing over specified duty cycles. Deterioration factors (DFs) are 

applied to these low-hour tests to project end-of-life emission levels. 

These final adjusted test results form the basis for the Family Certification Limit 

(FCL), which the manufacturer must specify to be at or above the certification test 

results. This FCL becomes the emission standard for the family and any certification or 

confirmatory testing must show compliance with this limit. In addition, manufactures 

may choose an FCL at any level above their certification test results to provide a larger 

compliance margin. If subsequent certification or confirmatory testing reveals emissions 

above the FCL, the new, higher result becomes the FCL. 

The FCL is also used to determine the Family Emissions Limit (FEL), which 

serves as the emission limit for any subsequent field testing conducted after the time of 

certification. This would primarily include selective enforcement audits (SEAs), but also 

may include in-use testing and/or production line testing for GHGs. The FEL differs 

from the FCL in that it includes an EPA-defined compliance margin; currently proposed 

to be 2%. Under this scenario the FEL will always be 2% higher than the FCL. If field 

testing activities reveal emission levels to be above this FEL, then the new test result 

becomes the FCL for the family, similar to certification testing.

Engine Emission Testing

Under current non-GHG engine emissions regulations, manufacturers are required 

to demonstrate compliance using two test methods: the heavy-duty transient cycle and the 

heavy-duty steady state test. Each test is an engine speed versus engine torque schedule 

intended to be run on an engine dynamometer. Over each test, emissions are sampled 

using the equipment and procedures outlined in 40 CFR Part 1065, which includes 

provisions for measuring CO2, N2O, and CH4. Emissions may be sampled continuously

or in a batch configuration (commonly known as “bag sampling”) and the total mass of 

emissions over each cycle are normalized by the engine power required to complete the 

cycle. Following each test, a validation check is made comparing actual engine speed 

and torque over the cycle to the commanded values. If these values do not align well, the 

test is deemed invalid.

The transient test, also known as the Federal Test Procedure (FTP), is 

characteristic of typical urban stop-and-go driving. Also included is a period of more 

steady state operation that would be typical of short cruise intervals at 45 to 55 miles per 

hour. Each transient test consists of two 20 minute tests separated by a “soak” period of 

20 minutes. The first test is run with the engine in a “cold” state, which involves letting 

the engine cool to ambient conditions either by sitting overnight or by forced cooling 

provisions outlined in §86.1335-90 (or 40 CFR Part 1036). This portion of the test is 

meant to assess the ability of the engine to control emissions during the period prior to 
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reaching normal operating temperature. This is commonly a challenging area in criteria 

pollutant emission control, as cold combustion chamber surfaces tend to inhibit mixing 

and vaporization of fuel and aftertreatment devices do not tend to function well at low 

temperatures. 

Following the first test, the engine is shut off for a period of 20 minutes, during 

which emission analyzer checks are performed and preparations are made for the second 

test (also known as the “hot” test). After completion of the second test, the results from 

the cold and hot tests are weighted and a single composite result is calculated for each 

pollutant. Based on typical in-use duty cycles, the cold test results are given a 1/7 

weighting and the hot test results are given a 6/7 weighting. Deterioration factors are 

applied to the final weighted results and the results are then compared to the emission 

standards.

Prior to 2007, compliance only needed to be demonstrated over the FTP. 

However, a number of events brought to light the fact that this transient cycle may not be 

as well suited for engines which spend much of their duty cycle at steady cruise 

conditions, such as those used in line-haul semi-trucks. As a result, the steady-state test 

was added, which was known as the supplemental emission test (or SET), consisting of 

13 steady-state modes. During each mode, emissions were sampled for a period of five 

minutes. Weighting factors were then applied to each mode and the final weighted 

results were compared to the emission standards (including deterioration factors). In 

addition, emissions at each mode could not exceed the NTE emission limits. 

Alternatively, manufacturers could run the test as a ramped-modal cycle (RMC). In this 

case, the cycle still consists of the same speed/torque modes, however linear progressions 

between points are added and instead of weighting factors, each mode is sampled for 

various amounts of time. The result is a continuous cycle lasting approximately 40 

minutes. With the implementation of Part 1065 test procedures in 2010, manufacturers 

are now required to run the modal test as a ramped-modal cycle. In addition, the order of 

the speed/torque modes in the RMC have changed for 2010 and later engines.

It is well known that fuel consumption, and therefore CO2 emissions, are highly 

dependent on the drive cycle over which they are measured. Steady cruise conditions, 

such as highway driving, tend to be more efficient, having lower fuel consumption and 

CO2 emissions. In contrast, highly transient operation, such as city driving, tends to lead 

to lower efficiency and therefore higher fuel consumption and CO2 emissions. One 

example of this is the difference between EPA-measured city and highway fuel economy 

ratings assigned to all new light-duty passenger vehicles. 

For these heavy-duty engine and vehicle rules, we believe it is important to assess 

CO2 emissions and fuel consumption over both transient and steady state test cycles, as 

all vehicles will operate in conditions typical of each cycle at some point in their useful 

life. However, due to the drive cycle dependence of CO2 emissions, we do not believe it 

is reasonable to have a single CO2 standard which must be met for both cycles. A single 

CO2 standard would likely prove to be too lax for steady-state conditions while being too 

strict for transient conditions. Therefore, we are recommending that all heavy-duty

engines be tested over both transient and steady-state tests. However, only the results 
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from either the transient or steady-state test cycles will be used to assess compliance with 

GHG standards, depending on they type of vehicle the engine will be used in. Engines 

that will be used in class 7/8 tractors will use the RMC for GHG certification, and 

vocational truck engines will use the FTP transient test. In both cases, results from the 

other test cycle will be reported but not used for a compliance decision. Engines will 

continue to be required to show criteria pollutant compliance over both cycles, in addition 

to NTE requirements.

Durability testing

Another element of the current certification process is the requirement to 

complete durability testing to establish deterioration factors (DFs). As previously

mentioned, manufacturers are required to demonstrate that their engines comply with 

emission standards throughout the regulatory compliance period of the engine. This 

demonstration is commonly made through the combination of low-hour test results and 

testing based deterioration factors.

For engines without aftertreatment devices (ATDs), deterioration factors 

primarily account for engine wear as service is accumulated. Commonly this includes 

valve/valve seat wear and piston ring wear, which both serve to reduce in-cylinder 

pressure. Oil control seals and gaskets also deteriorate with age, leading to higher 

lubricating oil consumption. Additionally, flow properties of EGR systems may change 

as deposits accumulate and therefore alter the mass of EGR inducted into the combustion 

chamber. These factors, amongst others, may serve to reduce power, increase fuel 

consumption, and change combustion properties; all of which affect pollutant emissions.

For engines equipped with ATDs, DFs take into account engine deterioration, as 

described above, in addition to aging affects on the ATDs. Oxidation catalysts and other 

catalytic devices rely on active precious metals to effectively convert and reduce harmful 

pollutants. These metals may become less active with age and therefore pollutant 

conversion efficiencies may decrease. Particulate filters may also experience reduced 

trapping efficiency with age due to ash accumulation and/or degradation of the filter 

substrate, which may lead to higher tailpipe PM measurements and/or increased 

regeneration frequency. With ATD equipped engines, the DFs for pollutants managed by 

ATDs are primarily a function of the aftertreatment device(s) rather than deterioration of 

the engine, since conversion/reduction efficiencies of the ATDs are generally quite high 

in a nominal state.

At this time, we anticipate that most engine component wear will not have a 

significant negative impact on CO2 emissions. However, wear and aging of aftertreatment 

devices may or may not have a significant negative impact on CO2 emissions. In 

addition, future engine or aftertreatment technologies may experience significant 

deterioration in CO2 emissions performance over the useful life of the engine. For these 

reasons, we believe that the use of DFs for CO2 emissions is both appropriate and 

necessary. As with criteria pollutant emissions, these DFs are preferably developed 

through testing the engine over a representative duty cycle for an extended period of 

time. This is typically either half or full useful life, depending on the regulatory class. 
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The DFs are then calculated by comparing the high-hour to low-hour emission levels, 

either by division or subtraction (for multiplicative & additive DFs, respectively). 

This testing process may be a significant cost to an engine manufacturer, mainly

due to the amount of time and resources required to run the engine out to half or full 

useful life. For this reason, durability testing for the determination of DFs is not 

commonly repeated from model year to model year. In addition, some DFs may be 

allowed to carry over between families sharing a common architecture and aftertreatment 

system. EPA prefers to have manufacturers develop testing-based DFs for their products, 

and we are proposing that this be the case for the final rule. However, we do understand 

that for the reasons stated above, it may be impractical to expect manufacturers to have 

testing-based deterioration factors available for this proposal. Therefore, we are willing to 

consider requiring the use of assigned DFs for CO2. Under this possibility, we suggest 

that manufacturers would be required to submit any CO2 data from durability testing to 

aid in developing more accurate assigned DFs.

IRAFs/Regeneration impacts on CO2

Heavy-duty engines may be equipped with exhaust aftertreatment devices which 

require periodic “regeneration” to return the device to a nominal state. A common 

example is a diesel particulate filter (DPF), which accumulates particulate matter (PM) as 

the engine is operated. When the PM accumulation reaches a threshold such that exhaust 

backpressure is significantly increased, exhaust temperature is actively increased to 

oxidize the stored PM. The increase in exhaust temperature is commonly facilitated 

through late combustion phasing and/or raw fuel injection into the exhaust system 

upstream of the DPF. Both methods impact emissions and therefore must be accounted 

for at the time of certification. In accordance with §86.004-28(i), this type of event would 

be considered infrequent because in most cases they only occur once every 30 to 50 hours 

of engine operation (rather than once per transient test cycle), and therefore adjustment 

factors must be applied at certification to account for these effects.

Similar to DFs, these adjustment factors are based off of manufacturer testing; 

however this testing is far less time consuming. Emission results are measured from two 

test cycles: with and without regeneration occurring. The differences in emission results 

are used, along with the frequency at which regeneration is expected to occur, to develop 

upward (UAFs) and downward adjustment factors (DAFs). UAFs are added to all 

emission results derived from a test cycle in which regeneration did not occur. Similarly, 

DAFs are applied to results based on a cycle which did experience a regeneration event. 

Each pollutant will have a unique set of adjustment factors and additionally, separate 

factors are commonly developed for transient and steady-state test cycles.

The impact of regeneration events on criteria pollutants varies by pollutant and 

the aftertreatment device(s) used. In general, the adjustment factor can have a very

significant impact on compliance with the NOX standard. For this reason, heavy-duty 

truck and engine OEMs are already very well motivated to extend the regeneration 

frequency to as long an interval as possible and to reduce the during of the regeneration 

as much as possible. Both of these actions significantly reduce the impact of 
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regeneration on CO2 emissions and fuel consumption. We do not believe that adding an 

adjustment factor for infrequent regeneration to the CO2 or fuel efficiency standards 

would provide a significant additional motivation to OEMs to reduce regenerations. 

However, doing so would add significant uncertainty to our projections of CO2 and fuel 

consumption performance in 2014 and beyond. In addressing that uncertainty, the 

Agencies would have to set less stringent fuel efficiency and CO2 standards for heavyduty trucks and engines. In practice, we believe adding an adjustment factor for 

infrequent regeneration would provide no significant improvement in infrequent 

regeneration beyond what will be achieved through the NOX standards, but would force 

the Agencies to set less effective standards for CO2 and fuel efficiency. Therefore, we 

are not proposing to include an infrequent regeneration adjustment factor for CO2 or fuel 

efficiency in this program. The Agencies are seeking public commentary on this 

approach.

AECDs

As part of the engine control strategy, there may be devices or algorithms which 

reduce the effectiveness of emission control systems under certain limited circumstances. 

These strategies are referred to as Auxiliary Emission Control Devices (AECDs). One 

example would be the reduced use of EGR during cold engine operation. In this case, low 

coolant temperatures may cause the electronic control unit to reduce EGR flow to 

improve combustion stability. Once the engine warms up, normal EGR rates are resumed 

and full NOX control is achieved. 

At the time of certification, manufacturers are required to disclose all AECDs and 

provide a full explanation of when the AECD is active, which sensor inputs effect AECD 

activation, and what aspect of the emission control system is affected by the AECD. 

Manufacturers are further required to attest that their AECDs are not “defeat-devices,” 

which are intentionally targeted at reducing emission control effectiveness. 

Several common AECDs disclosed for criteria pollutant certification will have a 

similarly negative influence on GHG emissions as well. One such example is cold-start 

enrichment, with provides additional fueling to stabilize combustion shortly after initially

starting the engine. From a criteria pollutant perspective, HC emissions can reasonably 

be expected to increase as a result. From a GHG perspective, the extra fuel does not result 

in a similar increase in power output and therefore the efficiency of the engine is reduced,

which has a negative impact on CO2 emissions. In addition, there may be AECDs that 

uniquely reduce GHG emission control effectiveness. Therefore, consistent with today’s 

certification procedures, we are proposing that a comprehensive list of AECDs covering 

both criteria pollutant, as well as GHG emissions is required at the time of certification. 

(ii) EPA’s N2O and CH4 Standards

In 2009, a rule was established requiring manufacturers of mobile-source engines 

to report the emissions of CO2, N2O, and CH4. While CO2 is commonly measured during 

certification testing, CH4 and N2O are not. CH4 has traditionally not been included in 

criteria pollutant regulations because it is a relatively stable molecule and does not 
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contribute significantly to ground-level ozone formation. In addition, N2O is commonly

a byproduct of lean-NOX aftertreatment systems. Until recently, these types of systems 

were not widely used on heavy-duty engines and therefore N2O emissions were 

insignificant. Both species, while emitted in small quantities relative to CO2, have much 

higher global warming potential (GWP) than CO2 and therefore must be considered as 

part of a comprehensive GHG regulation.

EPA is proposing that CH4 and N2O be reported at the time of certification. We 

are proposing to allow manufacturers to use a compliance statement based on good 

engineering judgment for the first year of the program in lieu of direct measurement of 

N2O. However, beginning in 2015 model year, the agency is proposing to require the 

direct measurement of N2O for certification. The intent of the CH4 and N2O standards 

are more focused on prevention of future increases in these compounds, rather than 

forcing technologies that reduce these pollutants. As one example, we envision 

manufacturers satisfying this requirement by using catalyst formulations that do not 

promote increases in N2O rather than pursuing a catalyst that may increase N2O. In many

ways this becomes a design-based criterion in that the decision of one catalyst over 

another will effectively determine compliance with N2O standards over the useful life of 

the engine. For this reason, we believe low-hour test results are adequate to demonstrate 

compliance with CH4 and N2O standards and we are proposing to accept DF values 

provided by manufacturers of zero (additive) or one (multiplicative).

EPA is also proposing an option which allows manufacturers to calculate a CO2-

equivalent value which is subject to the CO2 standards in lieu of complying with the 

separate N2O and CH4 caps.

(c) Additional Compliance Provisions

(i) Warranty & Defect Reporting

Under section 207 of the Clean Air Act, engine manufacturers are required to 

warrant their product such that it is free from defects that would cause the engine to not 

comply with emission standards. This warranty must be applicable from when the engine 

is introduced into commerce through a period generally defined as half of the regulatory

useful life (specified in hours and years, whichever comes first). The exact time of this 

warranty is dependent on the regulatory class of the engine. In addition, components that 

are considered “high cost” are required to have an extended warranty. Examples of such 

components would be exhaust aftertreatment devices and electronic control units.

Current warranty provisions in 40 CFR Part 86 define the warranty periods and covered 

components for heavy-duty engines. The current list of components is comprised of any

device or system whose failure would result in an increase in criteria pollutant emissions. 

At this point, we believe this list to be adequate for addressing GHG emissions as well. 

However, there may be instances where the failure of a component or system may reduce 

the efficiency of the engine while not increasing criteria pollutant emissions. In this case, 

the component or system may be inappropriately left off the list of covered components. 

Therefore we are seeking public comment on what devices and/or systems may need to 
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be added to the warranted component list to adequately address GHG emissions. The 

following list identifies items commonly defined as critical emission-related components:

 Electronic control units

 Aftertreatment devices

 Fuel metering components

 EGR-System components

 Crankcase-ventilation valves

 All components related to charge-air compression and cooling

 All sensors and actuators associated with any of these components

When a manufacturer experiences an elevated rate of failure of an emission 

control device, they are required to submit defect reports to the EPA. These reports will 

generally have an explanation of what is failing, the rate of failure, and any possible 

corrections taken by the manufacturer. Based on how successful EPA believes the 

manufacturer to be in addressing these failures, the manufacturer may need to conduct a 

product recall. In such an instance, the manufacturer is responsible for contacting all 

customers with affected units and repairing the defect at no cost to them. We believe this 

structure for the reporting of criteria pollutant defects, and recalls, is appropriate for 

components related to complying with GHG emissions as well. 

(2) Proposed Enforcement Provisions

(a) ECI Labeling

Current provisions for engine certification require manufacturers to equip their 

product with permanent emission control information (ECI) labels. These labels list 

important characteristics, parameters, and specifications related to the emissions 

performance of the engine. These include, but are not limited to, the manufacturer, 

model, displacement, emission control systems, and tune-up specifications. In addition, 

this label also provides a means for identifying the engine family name, which can then 

be referenced back to certification documents. This label provides essential information 

for field inspectors to determine that an engine is in fact in the certified configuration.

We do not anticipate any major changes needing to be made to ECI labels as a 

result of new GHG standards and a single label is appropriate for both criteria pollutant 

and GHG emissions purposes. Perhaps the most significant addition would be the 

inclusion of family certification levels (FCLs) or family emission limits (FELs) for GHG 

pollutants, if the manufacturer is participating in averaging, banking, and trading. In 

most cases, this would be a CO2 FEL. However, a manufacturer may also specify a CO2-

equivalent FEL (CO2e), which considers N2O and CH4 emissions in addition to CO2.
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(b) In-Use Standards

In-use testing of engines provides a number of benefits for ensuring useful life 

compliance. In addition to verifying compliance with emission standards at any given 

point in the useful life, it can be used along with manufacturer defect reporting, to 

indentify components failing at a higher than normal rate. In this case, a product recall or 

other service campaign can be initiated and the problem can be rectified. Another key

benefit of in-use testing is the discouragement of control strategies catered to the 

certification test cycles. In the past, engine manufacturers were found to be producing 

engines that performed acceptably over the certification test cycle, while changing to 

alternate operating strategies “off-cycle” which caused increases in criteria pollutant 

emissions. While these strategies are clearly considered defeat devices, in-use testing 

provides a meaningful way of ensuring that such strategies are not active under normal 

engine operation.

Currently, manufacturers of certified heavy-duty engines are required to conduct 

in-use testing programs. The intent of these programs is to ensure that their products are 

continuing to meet criteria pollutant emission standards at various points within the 

useful life of the engine. Since initial certification is based on engine dynamometer 

testing, and removing in-use engines from their respective vehicles is often impractical, a 

unique testing procedure was developed. This includes using portable emission 

measurement systems (PEMS) and testing the engine over typical in-situ drive routes 

rather than a prescribed test cycle. To assess compliance, emission results from a well 

defined area of the speed/torque map of the engine, known as the not-to-exceed (NTE) 

zone, are compared to the emission standards. To account for potential increases in 

measurement and operational variability, certain allowances are applied to the standard

which results in the standard for NTE measurements (NTE limit) to be at or above the 

duty cycle emission standards.

In addition, EPA also conducts an annual in-use testing program of heavy-duty

engines. Testing procured vehicles with specific engines over well-defined drive routes 

using a constant trailer load allows for a consistent comparison of in-use emissions 

performance. If potential problems are identified in-situ, the engine may be removed 

from the vehicle and tested using an engine dynamometer over the certification test 

cycles. If deficiencies are confirmed the Agency will either work with the manufacturer 

to take corrective action or proceed with enforcement action against the manufacturer.

The GHG reporting rule requires manufacturers to submit CO2 data from all 

engine testing (beginning in the 2011 model year), which we believe is equally applicable 

to in-use measurements. Methods of CO2 in-situ measurement are well established and 

most, if not all, PEMS devices measure and record CO2 along with criteria pollutants. 

CH4 and N2O present in-situ measurement challenges that may be impractical to 

overcome for this testing, and therefore it is not recommended that they be included in inuse testing requirements at this time. While measurement of CO2 may be practical and 

important, implementing an NTE emission standard for CO2 is challenging. As 

previously discussed, CO2 emissions are highly dependent on the drive cycle of the 

vehicle, which does not lend itself well to the NTE-based test procedure. Therefore, we 
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propose that manufacturers be required to submit CO2 data from in-use testing, in both 

g/bhp-hr and g/ton-mile, but these data will be used for reference purposes only (there 

would be no NTE limit/standard for CO2).

(3) Other Certification Provisions

(a) Carryover/Carry Across Certification Test Data

EPA’s current certification program for heavy-duty engines allows manufacturers 

to carry certification test data over and across certification testing from one model year to 

the next, when no significant changes to models are made. EPA is proposing to also 

apply this policy to CO2, N2O and CH4 certification test data. 

(b) Certification Fees

The CAA allows EPA to collect fees to cover the costs of issuing certificates of 

conformity for the classes of engines covered by this proposal. On May 11, 2004, EPA 

updated its fees regulation based on a study of the costs associated with its motor vehicle 

and engine compliance program (69 FR 51402). At the time that cost study was

conducted, the current rulemaking was not considered. At this time the extent of any

added costs to EPA as a result of this proposal is not known. EPA will assess its

compliance testing and other activities associated with the rule and may amend its fees 

regulations in the future to include any warranted new costs.

(c) OBD

Beginning in the 2013 model year, manufacturers will be required to equip heavyduty engines with on-board diagnostic systems. These systems monitor the activity of the 

emission control system and issue alerts when faults are detected. These diagnostic 

systems are currently being developed based around components and systems that 

influence criteria pollutant emissions. Consistent with the light-duty vehicle GHG rule, 

we believe that monitoring of these components and systems for criteria pollutant 

emissions will have and equally beneficial affect on CO2 emissions. Therefore, we do 

not anticipate the necessity of having any unique OBD provisions for heavy-duty GHG 

emissions. We are open to comment on this topic, however.

(d) Applicability of Current High Altitude Provisions to Greenhouse Gases

EPA is proposing that engines covered by this proposal must meet CO2, N2O and 

CH4 standards at elevated altitudes. The CAA requires emission standards under section 

202 for heavy-duty engines to apply at all altitudes. EPA does not expect engine CO2, 

CH4, or N2O emissions to be significantly different at high altitudes based on engine

calibrations commonly used at all altitudes. Therefore, EPA proposes that it retain its 

current high altitude regulations so manufacturers will not normally be required to submit 

engine CO2 test data for high altitude. Instead, they will be required to submit an 

engineering evaluation indicating that common calibration approaches will be utilized at 

high altitude. Any deviation in emission control practices employed only at altitude will 
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need to be included in the auxiliary emission control device (AECD) descriptions 

submitted by manufacturers at certification. In addition, any AECD specific to high 

altitude will be required to include emissions data to allow EPA evaluate and quantify

any emission impact and validity of the AECD.

D. Class 7/8 Combination Trucks

(1) Proposed Compliance Approach

In addition to requiring engine manufacturers to certify their engines, 

manufacturers of class 7 and 8 combination trucks must also certify that their vehicles 

meet CO2 emission and fuel consumption standards. This vehicle certification will 

ensure that efforts beyond just engine efficiency improvements are undertaken to reduce 

GHG emissions. Some examples include aerodynamic improvements, rolling resistance 

reduction, idle reduction technologies, and vehicle speed limiting systems. 

Unlike engine certification however, this certification will be based on a loadspecific basis (g/ton-mile as opposed to work-based, or g/bhp-hr). This will take into 

account the anticipated vehicle loading that would be experienced in use and the 

associated affects on fuel consumption and CO2 emissions. Vehicle manufacturers will 

also be required to warrant their products against emission defects, and demonstrate that a 

service network is in place to correct any such conditions. The vehicle manufacturer also 

bears responsibility in the event that an emission-related recall is necessary. 

(a) Certification Process

In order to obtain a certificate of conformity for the truck, vehicle manufacturers 

must complete a compliance demonstration, showing that their product meets emission 

standards as well as other requirements in the CFR. For purposes of this demonstration, 

vehicles with similar emission characteristics throughout their useful life are grouped 

together in test groups, similar to EPA’s light-duty emissions certification program. 

Examples of characteristics that would define a test group for heavy-duty vehicles are 

wheel and tire package, aerodynamic profile, number and rolling resistance of tires, and 

engine model. Under this system, the worst-case vehicle would be selected based on 

having the highest fuel consumption, and all other models within the family are assumed 

to have emissions at or below the parent model and therefore in compliance with 

emission standards. Any vehicle within the family can be subject to selective 

enforcement auditing in addition to confirmatory or other administrator testing. The 

worst-case vehicle is then tested using either the optional chassis test or attribute-based 

model.

We anticipate test groups for class 7/8 combination tractors to utilize the 

standardized 12-digit naming convention, as outlined in the engine certification section of 

this chapter. As with engines, each certifying vehicle manufacturer will have a unique 

three digit code assigned to them. Currently, there is no 5th digit (industry sector) code 

for this class of vehicles, for which we propose to use the next available character, “2.” 

Since we are proposing that the engine is one of several test-group defining features, we 

still believe it is appropriate to include engine displacement in the family name. If the 
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test-group consists includes multiple engine models with varying displacements, the 

largest would be specified in the test-group name, consistent with current practices. The 

remaining characters would remain available for CARB and/or manufacturer use, such 

that the result is a unique test-group name.

Class 7 and 8 trucks share several common traits, such as the trailer attachment 

provisions, number of wheels, and general construction. However, further inspection 

reveals key differences related to GHG emissions. Payloads hauled by class 7 vehicles 

are significantly less than class 8 vehicles. In addition, class 8 vehicles may have 

provisions for hotelling (“sleeper cabs”), which results in an increase in size as well as 

the addition of comfort features like power and climate control for use while the truck is 

parked. Both segments may have various degrees of roof fairing to provide better 

aerodynamic matching to the trailer being pulled. This is a feature which can help reduce 

CO2 emissions significantly when properly matched to the trailer, but can also increase 

CO2 emissions if improperly matched. Based on these differences, it is reasonable to 

expect differences in CO2 emissions, and therefore these properties form the basis for 

combination tractor regulatory subcategories.

The various combinations of payload, cab size, and roof profile result in nine 

regulatory subcategories for class 7 and 8 trucks. These include class 7 (day cabs), class 

8 (day cabs), and class 8 (sleeper cabs), each with high, mid, and low roof profiles. These 

vehicles all have a regulatory useful life of 435,000 miles and therefore must meet CO2

emission standards throughout this period, as required in the CAA. 

(b) Demonstrating compliance with the proposed standards

(i) CO2 and Fuel Consumption Standards

Consistent with existing certification processes for light-duty vehicles and heavyduty pickups and vans, emissions testing of the complete vehicle would be the preferred 

method for demonstrating compliance with vehicle emission standards. However, 

vehicle-level certification is new to the heavy-duty vehicle segment above 14,000 lbs. 

Therefore, most vehicle manufacturers are not adequately equipped to conduct vehiclelevel emission testing for class 7/8 combination tractors. Chassis dynamometers, 

emission sampling equipment, and staff engineering support are a few of the factors that 

would add significant cost to vehicle development in a relatively short amount of time, 

which may make the prospect of vehicle testing quite onerous. In addition to the 

infrastructure and testing facilities the industry would need to add, the Agencies have not 

completed the extensive work ultimately desirable for us to propose new test procedures 

and standards based on the use of a chassis test procedure. Recognizing these constraints 

related to time, staffing, and capitol, we are proposing only a vehicle simulation model 

option for demonstrating compliance at the time of certification. However, we do believe 

that a chassis based test procedure as currently utilized for vehicles below 14,000lbs 

could be a better long-term approach to regulate all heavy-duty vehicles and we are 

seeking comment on a chassis based approach.

Model
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Vehicle modeling will be conducted using EPA’s [TEST] simulation model, 

which is described in detail in Chapter 4 of the draft RIA. Basically, this model functions 

by defining a vehicle model then exercises this model over various drive cycles. Several 

initialization files are needed to define a vehicle, which include mechanical attributes, 

control algorithms, and driver inputs. The majority of these inputs will be predetermined 

by EPA and NHTSA for the purposes of vehicle certification. The net results from the 

[TEST] model are CO2 emissions and fuel consumption values over the drive cycle that 

the user selects. The CO2 emission result will be used for demonstrating compliance with 

vehicle GHG standards.

The vehicle manufacturer will be responsible for entering aerodynamic properties 

of the vehicle, the weight reduction, tire properties, idle reduction systems, and vehicle 

speed limiting systems. For [TEST] inputs relating to weight reduction, rolling 

resistance, and aerodynamics, EPA is proposing the use of lookup tables based on typical 

performance levels across the industry. These lookup tables do not have data directly 

related to CO2, but rather provide the appropriate coefficients for the model to assess 

CO2-related performance. Examples are typical drag coefficients for conventional and 

Smart-Way class 8 sleeper cabs or coefficients of rolling resistance for standard and lowrolling resistance tires. The exception is for idle reduction technologies, which will have 

a CO2 reduction specified in the lookup tables. We believe this approach reduces the 

testing burden placed upon manufacturers, yet adequately assesses improvements 

associated with select technologies. The model will be publicly available and will be 

found on EPA’s website.

The Agency reserves the right to independently evaluate the inputs to model via 

Administrator testing to validate those model inputs. The Agency also reserves the right 

to evaluate vehicle performance using the inputs to the model provided by the 

manufacturer to confirm the performance of the system using [TEST]. In the event of 

such testing or evaluation, the Administrator’s results become the official certification 

results. The exception being that the manufacturer may continue to use their data, 

provided it represents a worst-case condition over the Administrator’s results.

To better facilitate the entry of only the appropriate parameters, EPA will provide 

a spreadsheet-type template for entering data specific to each vehicle. This template can 

then be fed directly to the model, which allows the end user to avoid interacting directly 

with the model and any associated coding. It is expected that this template will be 

submitted to EPA as part of the certification process for each certified vehicle 

configuration.

For certification, the model will exercise the vehicle over three test cycles; one 

transient and two steady-state. For the transient test, we are proposing to use the heavyheavy-duty diesel truck (HHDDT) transient test cycle, which was developed by the 

California Air Resources Board and West Virginia University to evaluate heavy-duty 

vehicles. The transient mode simulates urban, start-stop driving, featuring 1.8 stops per 

mile over the 2.9 mile duration. The two steady state test points are reflective of the 

tendency for some of these vehicles to operate for extended periods at highway speeds. 
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Based on data from the EPA’s MOVES database, and common highway speed limits, we 

are expecting these two points to be 55 and 65 mph. 

The model will predict the total emissions results from each segment using the 

unique properties entered for each vehicle. These results are then normalized to the

payload and distance covered, so as to yield a gram/ton-mile result, as well as a fuel 

consumption (gal/ton-mile) result for each test cycle. As with engine and vehicle testing, 

certification will be based on a parent rating for the test group, representing the worstcase fuel consumption and CO2 emissions. However, vehicle manufacturers will also 

have the opportunity to model sub-configurations to determine any benefits that are 

available on only a select number of vehicles within a test group.

The results from all three tests are then combined using weighting factors, which 

reflect typical usage patterns. The typical usage characteristics of class 7 and 8 trucks 

with day cabs differ significantly from class 8 vehicles with sleeper cabs. The trucks 

with day cabs tend to operate in more urban areas, have a limited travel range, and tend to 

return to a common depot at the end of each shift. Class 8 sleeper cabs, however, are 

typically used for long distance trips which consist of mostly highway driving in an effort 

to cover the highest mileage in the shortest time. For these reasons, we propose that the 

cycles are weighted differently for these two groups of vehicles. For class 7 and 8 trucks 

with day cabs, we recommend weights of 64%, 17%, and 19% (65 mph, 55 mph, and 

transient, resp.). For class 8 with sleeper cabs, the high speed cruise tendency results in 

weights of 86%, 9%, and 5% (65 mph, 55 mph, and transient, resp.). These final, 

weighted emission results are compared to the emission standard to assess compliance.

Durability Testing

As with engine certification, a manufacturer must provide evidence of compliance 

through the regulatory useful life of the vehicle. Factors influencing vehicle-level GHG 

performance over the life of the vehicle fall into two basic categories: vehicle attributes 

and maintenance items. Each category merits different treatment from the perspective of 

assessing useful life compliance, as each has varying degrees of manufacturer versus 

owner/operator responsibility.

The category of vehicle attributes generally refers to aerodynamic features, such 

as fairings, side-skirts, air dams, air foils, etc, which are installed by the manufacturer to 

reduce aerodynamic drag on the vehicle. These features have a significant impact on 

GHG emissions and their emission reduction properties are assessed early in the useful 

life (at the time of certification). These features are expected to last the full life of the 

vehicle without becoming detached, cracked/broken, misaligned, or otherwise not in the 

original state. In the absence of the aforementioned failure modes, the performance of 

these features is not expected to degrade over time and the benefit to reducing GHG 

emissions is expected to last for the life of the vehicle with no special maintenance 

requirements. To assess useful life compliance, we recommend a design-based approach 

which would ensure that the manufacturer has robustly designed these features so they

can reasonably be expected to last the useful life of the vehicle.
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The category of maintenance items refers to items that are replaced, renewed, 

cleaned, inspected, or otherwise addressed in the preventative maintenance schedule 

specified by the vehicle manufacturer. Items that have a direct influence on GHG 

emissions are primarily lubricants and tire pressure. Synthetic engine oil may be used by

vehicle manufacturers to reduce the GHG emissions of their vehicles. Manufacturers may

specify that these fluids be changed throughout the useful life of the vehicle. If this is the

case, the manufacturer should have a reasonable basis that the owner/operator will use 

fluids having the same properties. This may be accomplished by requiring (in service 

documentation, labeling, etc) that only these fluids can be used as replacements. 

Similarly, tire pressure has a profound affect on GHG emissions and fuel consumption. It 

is preferred that vehicle manufacturers equip their vehicles with tire pressure monitoring 

systems (TPMS) to ensure that drivers are immediately notified of tires with low 

pressure. Aside from TPMS, there is unfortunately little that a manufacturer can do to 

ensure proper tire inflation. Fortunately, the effect of tire inflation on fuel consumption is 

well known and therefore we believe that most owner/operators will keep tires properly 

inflated if only for economic reasons. Currently, EPA seeks public comment on the 

merits and feasibility of requiring TPMS on all new heavy-duty vehicles as part of this 

proposal.

If the vehicle remains in its original certified condition throughout its useful life, 

it is not believed that GHG emissions would increase as a result of service accumulation. 

This is based on the assumption that as components wear, the rolling resistance due to 

friction is likely to stay the same or decrease. With all other components remaining equal 

(tires, aerodynamics, etc), the overall drag force would stay the same or decrease, thus 

not significantly changing GHG emissions at the end of useful life. It is important to 

remember however, that this vehicle assessment does not take into account any enginerelated wear affects, which may in fact increase GHG emissions over time.

For the reasons explained above, we believe that for the first phase of this 

program, it is most important to ensure that the vehicle remain in its certified 

configuration throughout the useful life. This can most effectively be accomplished 

through engineering analysis and specific maintenance instructions provided by the 

vehicle manufacturer. The vehicle manufacturer would be primarily responsible for 

providing engineering analysis demonstrating that vehicle attributes will last for the full 

life of the vehicle. In addition they will be required to submit the recommended 

maintenance schedule (and other service related documentation), showing that fluids 

meeting original equipment properties are required as replacements. 

(ii) EPA’s Air Conditioning Leakage Standards

Heavy-duty vehicle air conditioning (A/C) systems contribute to GHG emissions 

in two ways. First, operation of the air conditioning unit places an accessory load on the 

engine, which increases fuel consumption. Second, most modern refrigerants are 

Hydrofluorocarbon (HFC) based, which have significant global warming potential 

(GWP=1430). For heavy-duty vehicles, the load added by the air conditioning system is 

comparatively small compared to other power requirements of the vehicle. Therefore, we 

are not targeting any GHG reduction due to decreased air conditioning usage or higher 
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efficiency A/C units for this proposal. However, refrigerant leakage, even in very small 

quantities, can have significant adverse effects on GHG emissions. 

Refrigerant leakage is a concern for heavy-duty vehicles, similar to light-duty

vehicles. To address this, EPA is proposing a design-based standard for reducing 

refrigerant leakage from heavy-duty vehicles. This standard is based off using the best 

practices for material selection and interface sealing, as outlined in SAE publication 

J2727. Based on design criteria in this publication, a leakage “score” can be assessed and 

an estimated annual leak rate can be made for the A/C system.

At the time of certification, manufacturers will be required to outline the design of 

their system, including specifying materials and construction methods. They will also 

need to supply the leakage score developed using SAE J2727 and the refrigerant volume 

of their system to determine the leakage rate per year. If the certifying manufacturer does 

not complete installation of the air conditioning unit, detailed instructions must be 

provided to the final installer which ensures that the A/C system is assembled to meet the 

low-leakage standards. These instructions will also need to be provided at the time of 

certification, and manufacturers must retain all records relating to auditing of the final 

assembler.

(c) In-Use Standards

As previously addressed, the drive-cycle dependence of CO2 emissions makes 

NTE-based in-use testing impractical. In addition, we believe the reporting of CO2 data 

from the criteria pollutant in-use testing program will be helpful in future rulemaking 

efforts. For these reasons, we are not proposing an NTE-based in-use testing program for 

class 7/8 combination tractors during this proposal.

In the absence of NTE-based in-use testing, provisions are necessary for verifying 

that production vehicles are in the certified configuration, and remain so throughout the 

useful life. Perhaps the easiest method for doing this is to verify the presence of installed 

emission-related components. This would basically consist of a vehicle audit against 

what is claimed in the certification application. This includes verifying the presence of 

aerodynamic components, such as fairings, side-skirts, and gap-reducers. In addition, the 

presence of idle-reduction and speed limiting devices would be verified. The presence of 

low rolling resistance tires could be verified at the point of initial sale; however 

verification at other points throughout the useful life would be non-enforceable for the 

reasons mentioned previously.

The category of wear items primarily relates to tires. It is expected that vehicle 

manufacturers will equip their trucks with low rolling resistance (LRR) tires, as they may

provide a substantial reduction in GHG emissions. The tire replacement intervals for this 

class of vehicle is normally in the range of 50,000 to 100,000 miles, which means the 

owner/operator will be replacing the tires at several points within the useful life of the 

vehicle. We believe that as LRR tires become more common on new equipment, the 

aftermarket prices of these tires will also decrease. Along with decreasing tire prices, the 

fuel savings realized through use of LRR tires will ideally provide enough incentive for 
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owner/operators to continue purchasing these tires. The inventory modeling in today's 

proposal reflects the continued use of low rolling resistance tires through the life of the 

vehicle. We seek comment on this and all aspects of our inventory modeling.

(2) Proposed Enforcement Provisions

As identified above, a significant amount of vehicle-level GHG reduction is 

anticipated to come from the use of components specifically designed to reduce GHG 

emissions. Examples of such components include low rolling resistance tires, 

aerodynamic fairings, idle reduction systems, and vehicle speed limiters. At the time of 

certification, vehicle manufacturers will specify which components will be on their 

vehicle when introduced into commerce. Based on this list of components reported to 

EPA the GHG performance of the vehicle will be assessed either through modeling or 

testing and a certificate of conformity may be issued. As described in the in-use testing 

section, it is important to have the ability to determine if the vehicle is in the certified 

configuration both at the time of sale, as well as at any point within the useful life.

Perhaps the most practical and basic method of verifying a vehicle is in its certified 

configuration is through a vehicle emissions control information label, similar to that 

used for engines and light-duty vehicles. This label would list identifying features of the 

vehicle, including model year, vehicle model, certified engine family, vehicle 

manufacturer, test group, and GHG emissions category. In addition, this label would list 

emission-related components that an inspector could reference in the event of a field 

inspection. Possible examples may include LRR (for low rolling resistance tires), ARF 

(aerodynamic roof fairing), and ARM (aerodynamic rearview mirrors). With this 

information, inspectors could verify the presence and condition of attributes listed as part 

of the certified configuration.

Similarly, on current ECI labels, manufacturers list abbreviations, which are defined 

in SAE J1930, for each emission control device. Examples include three-way catalyst 

(TWC), electronic control (EC), and heated oxygen sensor (HO2S). Unfortunately we are 

not aware of a similar, existing list of vehicle emission control devices and features likely 

to be used on heavy-duty vehicles. At this point, it is also difficult to develop such a list 

due to the wide array of devices and features vehicle manufacturers may used in the 

future. Therefore, we are currently seeking comment on how to best define a list of 

emission control devices and features for use in this vehicle GHG certification label. 

(3) Other Certification Provisions

(a) Warranty

Section 207 of the Clean Air Act requires manufacturers to warrant their products 

to be free from defects that would otherwise cause non-compliance with emission 

standards. In addition, this warranty must ensure that the vehicle remains in this 

configuration throughout its useful life. For purposes of this regulation, vehicle 

manufacturers must warrant all components installed which act to reduce CO2 emissions 

at the time of initial sale. This includes all aerodynamic features, tires, idle reduction 
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systems, speed limiting system, and other equipment added to reduce CO2 emissions. In 

addition, the manufacturer must ensure these components and systems remain functional 

for the useful life of the vehicle. The exception being tires, which are only required to be 

warranted for the first life of the tires (vehicle manufacturers are not expected to cover 

replacement tires). For aerodynamic features, such as fairings or side-skirts, the 

manufacturer must warrant against failures which are not the result operator damage. 

However, these components should be designed to withstand possible damage from 

normal driving, which may include stone impingement and other minor impact with 

small debris.

The vehicle manufacturer is also required to warrant the A/C system for the useful 

life of the vehicle against design or manufacturing defects causing refrigerant leakage in 

excess of the standard.

At the time of certification, manufacturers must supply a copy of the warranty

statement that will be supplied to the end customer. This document should outline what 

is covered under the GHG emissions related warranty as well as the length of coverage. 

Customers must also have clear access to the terms of the warranty, the repair network, 

and the process for obtaining warranty service.

(b) Certification Fees

Similar to engine certification, the Agency will assess certification fees for heavyduty vehicles. The proceeds from these fees are used to fund the compliance and 

certification activities related to GHG regulation for this regulatory category. In addition 

to the certification process, other activities funded by certification fees include EPAadministered in-use testing, selective enforcement audits, and confirmatory testing. At 

this point, the exact costs associated with the heavy-duty vehicle GHG compliance are 

not well known. EPA will assess its compliance program associated with this proposal 

and assess the appropriate level of fees. We anticipate that fees will be applied based on 

test groups, following the light-duty vehicle approach. 

(c) Requirements for conducting aerodynamic assessment using allowed methods

The requirements for conducting aerodynamic assessment using allowed methods 

includes three key components: 1) adherence to a minimum set of standardized criteria 

for each allowed method; 2) accuracy demonstration for a given aerodynamic assessment 

methodology and correlation demonstration between methodologies if a manufacturer is 

using an alternative method to determine aerodynamic values; and 3) submittal of 

aerodynamic values and supporting information on annual basis for the purposes of 

certifying vehicles to a particular aerodynamic bin as discussed in the section II.

First, we are proposing requirements for conducting each of the allowed 

aerodynamic assessment methods. We will cite approved and published standards and 

practices, where feasible, but will attempt to propose criteria where none exists or where 

more current research indicates otherwise. We are requesting comment on the proposed 

requirements for each allowed method, standards and practices that should be used, and 
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any unique criteria that we are proposing. A description of the requirements for each 

method is discussed later in this section. The manufacturer would be required to provide 

information showing that the meet these requirements and attest to the accuracy of the 

information provided.

Second, a manufacturer would be required to demonstrate a) the accuracy of 

aerodynamic assessment methodology and b) correlation demonstration between 

methodologies if a manufacturer is using an alternative method to determine aerodynamic 

values. 

The accuracy of aerodynamic assessment would be demonstrated using multiple 

tests on multiple vehicles with some statistical confidence applied as discussed later in 

this section. This ensures the accuracy of method solely on the merits of the chosen 

method. 

Further, if a manufacturer chooses to use a method other than the coastdown 

procedure (e.g., wind tunnel or CFD) for aerodynamic assessment, the manufacturer 

would be required to correlate that method using multiple tests on multiple vehicles. For 

wind tunnel testing, either full or reduced scale, a correlation would need to occur with 

coastdown procedure only to ensure that the wind tunnel is accurately modeling the 

aerodynamic value in the real world. For CFD, a correlation would occur with the 

coastdown procedure and a wind tunnel since CFD is a calculated value and, therefore, 

requires some empirical measurement to ensure accuracy. 

This demonstration must occur before a manufacturer can use their method and 

any testing for demonstration purposes must adhere to the requirements for conducting 

aerodynamic assessment mentioned above. 

Third, to ensure continued compliance, manufactures would be required to 

provide a minimum set of information on an annual basis at certification time to 1) 

support continued use of an aerodynamic assessment method and 2) to assign an 

aerodynamic values based on the applicable aerodynamic bins. The information supplied 

to the agencies should be based on an approved aerodynamic assessment method and 

adhere to the requirements for conducting aerodynamic assessment mentioned above.

Regardless of the method, all testing should be performed with a tractor-trailer 

combination to mimic real world usage. Accordingly, it is important to match the type of 

tractor with the correct trailer. Although, as discussed elsewhere in this proposal, the 

correct tractor-trailer combination is not always present or tractor-only operation may

occur, the majority of operation in the real world involves correctly matched tractortrailer combinations and we will attempt to reflect that here. Therefore, the following 

guidelines should be used when performing aerodynamic assessment:

• For a Class 7/8 tractor truck with a low roof, a flatbed trailer loaded to capacity

must be used;

• For a Class 7/8 tractor truck with a mid roof, a tanker trailer loaded to capacity

must be used;
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• For a Class 7/8 tractor truck with a high roof, a box trailer consistent with the 

specifications described in this proposal for the reference truck must be used.

This ensures consistency and continuity in the aerodynamic assessments, and 

maintains the overlap with real world operation.

Standardized Criteria for Aerodynamic Assessment Methods

(i) Coastdown Procedure Requirements

For coast down testing, the test runs should be conducted in a manner consistent 

with SAE J2263 with additional modifications as described in the Regulatory Impact 

Analysis using the mixed model analysis method. The Agency seeks comment on the use 

of these protocols and the modifications the Agency has described. 

Since the coastdown procedure is the primary aerodynamic assessment method, 

the manufacturer would be required to conduct the coastdown procedure according to the 

requirements in this proposal and supply the following to the agency for approval: 

 Facility information: name and location, description and/or 

background/history, equipment and capability, track and facility elevation, 

and track size/length;

 Test conditions for each test result including date and time, wind speed 

and direction, ambient temperature and humidity, vehicle speed, driving 

distance, manufacturer name, test vehicle/model type, model year, 

applicable model engine family, tire type and rolling resistance, test 

weight and driver name(s) and/or ID(s); 

 Cd results from valid tests including, at a minimum, eight (8) valid test 

results, with no maximum number, standard deviation, calculated error 

and error bands, and total number of tests, including number of voided or 

invalid tests. 

(ii) Wind Tunnel Testing Requirements

Wind tunnel testing must conform to the following procedures and modifications, 

where applicable, including: 

 SAE J1252, “SAE WIND TUNNEL TEST PROCEDURE FOR TRUCKS 

AND BUSES” (July 1981) except that article 5.2 that specifies a minimum 

Reynolds number of 0.7 x 106is not included and is superseded, for the 

purposes of this rulemaking, by a minimum Reynolds number of 1.0 x 106

and, for reduced-scale wind tunnel testing, a one-eighth (1/8th) or larger 

scale model of a heavy-duty tractor and trailer must be used and of 

sufficient design to simulate airflow through the radiator inlet grill;. 
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 J1594, “VEHICLE AERODYNAMICS TERMINOLOGY” (December 

1994); and

 J2071, “AERODYNAMIC TESTING OF ROAD VEHICLES - OPEN 

THROAT WIND TUNNEL ADJUSTMENT” (June 1994).

In addition, the wind tunnel used for aerodynamic assessment must be a 

recognized facility by the Subsonic Aerodynamic Testing Association (SATA). 

The Agency seeks comment on the use of these protocols and the modifications 

the Agency has described and the need for membership in SATA. 

For wind tunnel testing, we are proposing that manufacturers perform wind tunnel 

testing and the coastdown procedure, according the requirements proposed in this 

proposal, on the same tractor model and provide the results for both methods. The wind 

tunnel tests should be conducted at a zero yaw angle and, if so equipped, utilizing the 

moving/rolling floor (i.e., the moving/rolling floor should be on during the test as 

opposed to static) for comparison to the coastdown procedure, which assumes zero yaw 

angle for the oncoming wind. The manufacturer would be required to supply the 

following:

 Facility information: name and location, description and 

background/history, layout, wind tunnel type, diagram of wind tunnel 

layout, structural and material construction;

 Wind tunnel design details: corner turning vane type and material, air 

settling, mesh screen specification, air straightening method, tunnel 

volume, surface area, average duct area, and circuit length;

 Wind tunnel flow quality: temperature control and uniformity, airflow 

quality, minimum airflow velocity, flow uniformity, angularity and 

stability, static pressure variation, turbulence intensity, airflow 

acceleration and deceleration times, test duration flow quality, and overall 

airflow quality achievement;

 Test/Working section information: test section type (e.g., open, closed, 

adaptive wall) and shape (e.g., circular, square, oval), length, contraction 

ratio, maximum air velocity, maximum dynamic pressure, nozzle width 

and height, plenum dimensions and net volume, maximum allowed model 

scale, maximum model height above road, strut movement rate (if 

applicable), model support, primary boundary layer slot, boundary layer 

elimination method and photos and diagrams of the test section;

 Fan section description: fan type, diameter, power, maximum rotational 

speed, maximum tip speed, support type, mechanical drive, sectional total 

weight
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 Data acquisition and control (where applicable): acquisition type, motor 

control, tunnel control, model balance, model pressure measurement, 

wheel drag balances, wing/body panel balances, and model exhaust 

simulation

 Moving ground plane or Rolling Road (if applicable): construction and 

material, yaw table and range, moving ground length and width, belt type, 

maximum belt speed, belt suction mechanism, platen instrumentation, 

temperature control, and steering; and

 Facility correction factors and purpose. 

(iii) CFD Requirements

Currently, there is no existing standard, protocol or methodology governing the 

use of CFD. Therefore, we are coupling the use of CFD with empirical measurements 

from coastdown and wind tunnel procedures. However, we think it is important to 

require a minimum set of criteria that all CFD analysis should for the purpose of these 

rules.

Therefore, the agencies propose that an unstructured, time-accurate, 5 million cell, 

Navier-Stokes computational fluid dynamics code which uses turbulence models with 

boundary layer resolution of +/- 95% be used to perform aerodynamic assessment and 

calculate the drag coefficient. In addition, CFD runs should be conducted with the 

assumption zero yaw angle to match wind tunnel and coast down results. 

The agencies seek comment on the use of commercial or open source code and 

the criteria set forth above for conducting the analysis.

Finally, in general for each of the allowed aerodynamic assessment methods, we 

are requesting comment on the list of information that must be provided for facilities and 

test conditions.

Acceptance Demonstration for Aerodynamic Assessment Methods

The manufacturer would have to demonstrate that the methodology used for 

aerodynamic assessment is acceptable prior to its use. This demonstration would be 

performed prior to certification in the initial year, model year 2014, of the rules’ 

implementation and would require agency approval to proceed with use of the method for 

aerodynamic assessment thereafter. 

The demonstration testing would occur on up to three of the manufacturer’s 

models including: the top selling model, the worst-case aerodynamic model, and another 

randomly chosen model in the manufacturer’s fleet depending on the size of the 

manufacturer. If there is overlap in the models (e.g., the top selling model is also the 

worst-case), the agencies will choose the model used for demonstration. For smaller 

manufacturers, a reduction in the number of vehicles for demonstration should be 

requested from and must be approved by the agencies.
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The manufacturer would be required to perform three to five tests on the 

production-intent version of the tractor model and three to five tests of the modified 

version of the tractor model that would produce a significant difference in Cd. This 

demonstrates that the method used can capture differences in Cd produced by

vehicle/model configuration changes. 

For each aerodynamic assessment method, the manufacturer would be required to 

provide information on the test conditions for each test result including but not limited to: 

test date and time, wind speed (if applicable), temperature, humidity, manufacturer and 

model, model year, applicable model engine family, tire type and rolling resistance for 

actual model, model test weight, equivalent vehicle test weight, actual and simulated or 

equivalent vehicle speed, Reynolds number (if applicable), yaw angle (if applicable), 

blockage ratio (if applicable), model mounting (if applicable), model geometry, body axis 

force and moments (if applicable), total test duration, test vehicle and type and operator 

name(s) and/or ID(s). In addition, the manufacturer must provide the Cd results from 

valid tests including: at a minimum, three to five (3-5) valid test results for each 

configuration (e.g., base and modified) with no maximum number, standard deviation for 

valid test results, calculated error and error bands for valid test results, and total number 

of tests, including number of voided or invalid tests.

In addition to the testing for each aerodynamic assessment method, alternative 

methods will also require correlation testing to the coastdown procedure. This will 

provide confidence in the use of the alternative method once these proposed regulations 

are implemented. 

For an aerodynamic assessment method to be deemed acceptable, the results from 

the multiple test runs should be within plus or minus five percent (+/- 5%) of each other 

with a 95% confidence interval. In addition, for alternative aerodynamic assessment 

methods, the results must also correlate with the coastdown procedure or wind tunnel test 

results, depending on the alternative aerodynamic assessment method used, within plus or 

minus ten percent (+/- 10%) with a 95% confidence interval. We may also consider other 

factors to determine if an aerodynamic assessment method is acceptable. We are 

requesting comment on the correlation factors within and between aerodynamic 

assessment methods

For CFD, the manufacturer would be required to perform the coastdown 

procedure and wind tunnel testing on the model being simulated and compare the 

predicted Cd results to the experimental results. The simulations should be conducted 

assuming zero degrees of yaw angle and all simulated conditions should be consistent 

with the experimental test conditions. 

The manufacturer may use the data from the aerodynamic assessment correlation 

to satisfy the acceptance demonstration for that methodology.

Once the demonstration and correlation is performed, the manufacturer would not 

have to perform a demonstration test unless they make a fundamental change in their 

aerodynamic assessment method (e.g., switch to wind tunnel testing from coastdown, 
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change wind tunnel testing facilities or CFD software code). In addition, the agencies 

reserve the right to evaluate the manufacturer’s information and to request a redemonstration on a specific model if the manufacturer introduces a model used for 

demonstration and correlation with much different characteristics than the current model 

in their fleet. 

We are requesting comment on the number of vehicles that a manufacturer is 

required to test for demonstration purpose and the requirement for the method-to-method 

correlation of 5%.

Annual Testing and Data Submittal for Aerodynamic Assessment

Once the manufacturer has performed acceptance demonstration, the aerodynamic 

assessment can be used to generate Cd values for all models the manufacturer plans to 

certify and introduce into commerce. For each model, the manufacturer would supply a 

predicted Cd based on the frontal area for each of the other models in the manufacturer’s 

fleet and the other conditions used to determine the base Cd. This reduces burden on the 

manufacturer to perform aerodynamic assessment but provides data for all the models in 

a manufacturer’s fleet. If a manufacturer has previously performed aerodynamic 

assessment on the other models, the manufacturer may submit an experimental Cd in lieu 

of a predicted Cd.

The aerodynamic assessment data will be used in one of two ways: 1) the 

manufacturer will input the values and data, including the Cd from the aerodynamic 

assessment, into the agency’s model and determine a GHG value/score or 2) the agency

will use the manufacturer’s input data into the model and assign a GHG value/score.

Since the agency may input the data into the model, manufacturers must provide 

the information described above for acceptance demonstration for the purposes of annual 

certification. In addition, the manufacturer must supply manufacturer fleet information to 

the agency for annual certification purposes along with the acceptance demonstration 

parameters: manufacturer name, model year, model line (if different than manufacturer 

name), model name, engine family, engine displacement, transmission name and type, 

number of axles, axle ratio, vehicle dimensions, including frontal area, predicted or 

measured coefficient of Drag (Cd), assumptions used in developing the predicted or 

measured Cd. justification for carry-across of aerodynamic assessment data, photos of the 

model line-up, if available, and model applications and usage options.

We are requesting comment on the annual testing requirements and the burden on 

manufacturers to satisfy the requirements.

(d) Aerodynamic Assessment In-Use Compliance 

Although the procedures above ensure accuracy in the aerodynamic assessment, it 

is always beneficial to have the ability to perform confirmation or validation postcertification. Therefore, we reserve the right and have the authority under the Clean Air 

Act (CAA) to perform in-use compliance checks of aerodynamic assessment and the 

underlying methods to confirm and validate the generated aerodynamic results.
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Therefore, we are proposing a in-use compliance program for aerodynamic 

assessment that consists of two parts: 1) an in-use vehicle confirmatory evaluation using 

a vehicle recruited from the in-use fleet and performing the aerodynamic assessment 

discussed in this proposal, either using the manufacturer’s facility and tools or using the 

agency’s facility and tools; and/or 2) validation of the manufacturer source data by

performing an audit of the manufacturer’s aerodynamic assessment methods and tools 

using a reference truck as described in this proposal.

(i) In-Use Vehicle Aerodynamic Confirmation

The agencies will confirm the aerodynamic values, in particular Cd, of the 

manufacturer’s vehicle by: 1) recruiting the truck from the in-use fleet, 2) returning the 

truck to specification, if necessary, and 3) evaluating the in-use truck using the 

coastdown procedure. 

The manufacturer must provide the agencies with supporting information to 

perform the confirmation including: identifying a candidate vehicle, providing 

specifications for that particular model and for that particular vehicle, if possible, based 

on VIN, and other information as requested by the agencies.

Alternatively, if the manufacturer has chosen to use an alternative method to 

determine and provide aerodynamic assessment, the agencies may use the manufacturer’s 

model example for evaluation at some alternative site. For reduced-scale wind tunnel 

testing, this would include providing the scale model that the manufacturer used for 

aerodynamic assessment to the agencies for evaluation in a different reduced-scale wind 

tunnel of the agencies’ choosing. For CFD, the manufacturer would supply the agencies 

with the CFD software files (e.g., computer aided design and engineering files or 

CAD/CAE files) of the model to the agencies for analysis using some other CFD code of 

the agencies choosing. In addition, the manufacturers must supply other information as 

requested by the agencies to support evaluation of the alternative methods (e.g., test 

conditions if different than the acceptance demonstration and correlation testing above).

(ii) Manufacturer Aerodynamic Assessment Source Audit/Crosscheck 

In addition to the aerodynamic assessment confirmation, the agencies reserve the 

right to also perform an audit of the aerodynamic assessment method used by the 

manufacturer. 

For this audit, the agencies will select a standard reference truck for use in 

evaluating the manufacturer’s aerodynamic source. The reference truck will include an 

actual full size tractor-trailer combination from the in-use fleet (vehicle reference truck), 

a reduced-scale model of the tractor-trailer combination (reduced-scale reference truck), 

and CFD files of the tractor-trailer combination (CFD reference truck). The vehicle, 

reduced-scale and CFD reference truck would be used by the agencies at the 

manufacturer’s facility to evaluate the aerodynamic assessment method including: 

coastdown procedures at the manufacturer’s owned/operated or contracted track , wind 

tunnel evaluation at manufacturer’s owned/operated or contracted facility, and/or CFD 
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software analysis at the manufacturer’s facility or using the manufacturer’s CFD software 

program.

The manufacturer would be required to allow or arrange access for the agencies to 

the facility and/or CFD software for the audit and provide information to support the 

audit as requested by the agencies.

We are seeking comment on the information the manufacturer must supply to the 

agencies to support aerodynamic confirmation and source audits, and the use of a 

reference truck for aerodynamic assessment audits.

E. Class 2b-8 Vocational Trucks

(1) Proposed Compliance Approach

Similar to class 7 and 8 combination tractors, heavy-duty vocational vehicles will 

be required to have both engine and complete vehicle certificates of conformity. As 

discussed in the engine certification section, engines that will be used in vocational 

vehicles will need to be certified using the FTP cycle for GHG pollutants and show 

compliance through the useful life of the engine. This certification is in addition to the 

current requirements for obtaining a certificate of conformity for criteria pollutant 

emissions.

For this proposal, the majority of the GHG reduction for vocational trucks is 

expected come from the use of low rolling resistance tires as well as increased utilization 

of hybrid powertrain systems. Other technologies such as aerodynamic improvements 

and vehicle speed limiting systems are not as relevant for this class of vehicles, since the 

typical duty cycle is much more urban, consisting of lower speeds and frequent stopping. 

Idle reduction strategies are expected to be encompassed by hybrid technology, which we 

anticipate will handle power-take-off (PTO) operation. Therefore, for these initial rules, 

certification of heavy-duty vocational vehicles with conventional powertrains will focus 

on quantifying GHG benefits due to the use of low rolling resistance tires.

(a) Certification Process

Vehicles will be divided into test groups for purposes of certification. As with 

class 7/8 combination tractors, these are groups of vehicles within a given regulatory

class that are expected to share common emission characteristics. Vocational truck 

regulatory classes share the same structure as those used for heavy-duty engine criteria 

pollutant certification and are based on gross vehicle weight ratings (GVWR). For 

review, this includes light-heavy (LHD) with a GVWR less than 14,000 lbs, mediumheavy (MHD) with a GVWR greater than (or equal to) 14,000 lbs and less than 26,000 

lbs, and heavy-heavy (HHD) with a GVWR greater than (or equal to) 26,000 lbs. Other 

test group features may include the type of tires used, intended application, and number 

of wheels.
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As with class 7/8 combination tractors, we anticipate using the standardized 12-

digit naming convention to identify vocational truck test groups. As with engines and 

class 7/8 combination tractors, each certifying vehicle manufacturer will have a unique 

three digit code assigned to them. Currently, there is no 5th digit (industry sector) code 

for this class of vehicles, for which we propose to use the next available character, “3.” 

Since we are proposing that the engine is one of several test-group defining features, we 

still believe it is appropriate to include engine displacement in the family name. If the 

test-group consists includes multiple engine models with varying displacements, the 

largest would be specified in the test-group name, consistent with current practices. The 

remaining characters would remain available for CARB and/or manufacturer use, such 

that the result is a unique test-group name.

Each test group will need to demonstrate compliance with emission standards 

using the [TEST] vehicle model approach. Additional provisions are available for 

certification of hybrid vehicles or vehicles using unique technologies, which was detailed 

in Chapter IV. If the test group consists of multiple models, only result from the worstcase model is necessary for certification. However, manufacturers will need to submit an 

engineering evaluation demonstrating that the test group has been assembled 

appropriately and that the test model indeed reflects the worst-case model. Also, 

manufacturers should plan on submitting tire rolling resistance properties to EPA at the 

time of certification. Finally the data from each of the certification cycles described 

below will need to be submitted at the time of certification.

(b) Demonstrating compliance with the proposed standards

(i) CO2 and Fuel Consumption Standards

Model

For this stage of the rules, demonstrating compliance with GHG standards 

primarily involves demonstrating the use of LRR tires and quantifying the associated CO2

benefit. Similar to class 7/8 combination tractors, this will be done using [TEST]. 

However, the input parameters entered by the vehicle manufacturer will be limited to the 

properties of the tires. [TEST] will use the tire data, along with a baseline truck and 

engine, to generate a complete vehicle model. The test weight used in the model will be 

based on the vehicle class, as identified above. Light-heavy duty vehicles will have a test 

weight of 16,000 lbs, 25,150 lbs for medium-heavy duty vehicles, and heavy-heavy duty 

vocational vehicles will use a test weight of 67,000 lbs. The model will then be exercised 

over the HHDDT transient cycle as well as 55 and 65 mph steady-state cruise conditions. 

The results of each of the three tests will be weighted at 37%, 21%, and 42% for 65 mph, 

55 mph, and transient tests, respectively.

It may seem more expedient and just as accurate to require manufacturers use 

tires meeting certain industry standards for qualifying tires as having low rolling 

resistance. In addition, CO2 benefits could be quantified for different ranges of 

coefficients of rolling resistance to provide a means for comparison to the standard. 

However, we believe that as technology advances, other aspects of vocational trucks may
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warrant inclusion in future rulemakings. For this reason, we believe it is important to 

have the certification framework in place to accommodate such additions. While the 

modeling approach may seem to be overly complicated for this phase of the rules, it also

serves to create a certification pathway for future rulemakings and therefore we believe 

this is the best approach.

In-use Standards

The category of wear items primarily relates to tires. It is expected that vehicle 

manufacturers will equip their trucks with low rolling resistance (LRR) tires, as they may

provide a substantial reduction in GHG emissions. The tire replacement intervals for this 

class of vehicle is normally in the range of 50,000 to 100,000 miles, which means the 

owner/operator will be replacing the tires at several points within the useful life of the 

vehicle. We believe that as LRR tires become more common on new equipment, the 

aftermarket prices of these tires will also decrease. Along with decreasing tire prices, the 

fuel savings realized through use of LRR tires will ideally provide enough incentive for 

owner/operators to continue purchasing these tires. The inventory modeling in today's 

proposal reflects the continued use of low rolling resistance tires through the life of the 

vehicle. We seek comment on this and all aspects of our inventory modeling.

(ii) Evaporative Emission Standards

Evaporative and refueling emissions from heavy-duty highway engines and 

vehicles are currently regulated under 40 CFR part 86. Even though these emission

standards apply to the same engines and vehicles that must meet exhaust emission 

standards, we require a separate certificate for complying with evaporative and refueling 

emission standards. An important related point to note is that the evaporative and 

refueling emission standards always apply to the vehicle, while the exhaust emission 

standards may apply to either the engine or the vehicle. For vehicles other than pickups 

and vans, the standards proposed in this notice to address greenhouse gas emissions apply

separately to engines and to vehicles. Since we plan to apply both greenhouse gas 

standards and evaporative/refueling emission standards to vehicle manufacturers, we 

believe it would be advantageous to have the regulations related to their certification 

requirements written together as much as possible. EPA regards these proposed changes 

as discrete, minimal, and for the most part clarifications to the existing standards. Except 

as specifically proposed here, EPA is not soliciting comment on, or otherwise considering 

whether to make changes to those standards. Accordingly, EPA will not consider any 

comments directed to any aspect of these standards other than those specifically proposed 

here.

We are generally not proposing to change the evaporative or refueling emission 

standards, but we have come across several provisions that warrant clarification or 

correction: 

 When adopting the most recent evaporative emission change we did not carry 

through the changes to the regulatory text applying evaporative emission 

standards for methanol-fueled compression-ignition engine. The proposed 
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regulations correct this by applying the new standards to all fuels that are subject 

to standards.

 We are proposing provisions to address which standards apply when an auxiliary

(nonroad) engine is installed in a motor vehicle, which is currently not directly 

addressed in the highway regulation. The proposed approach would require 

testing complete vehicles with any auxiliary engines (and the corresponding fuelsystem components). Incomplete vehicles would be tested without the auxiliary

engines, but any such engines and the corresponding fuel-system components 

would need to meet the standards that apply under our nonroad program as 

specified in 40 CFR part 1060.

 We are proposing to remove the option for secondary vehicle manufacturers to 

use a larger fuel tank capacity than is specified by the certifying manufacturer 

without re-certifying the vehicle. Secondary vehicle manufacturers needing a 

greater fuel tank capacity would need to either work with the certifying 

manufacturer to include the larger tank, or go through the effort to re-certify the 

vehicle itself. Our understanding is that this provision has not been used and 

would be better handled as part of certification rather than managing a separate 

process. We are proposing corresponding changes to the emission control 

information label.

 Rewriting the regulations in a new part in conjunction with the greenhouse gas 

standards allows for some occasions of improved organization and clarity, as well 

as updating various provisions. For example, we are proposing a leaner 

description of evaporative emission families that does not reference sealing 

methods for carburetors or air cleaners. We are also clarifying how evaporative 

emission standards affect engine manufacturers and proposing more descriptive 

provisions related to certifying vehicles above 26,000 pounds GVWR using 

engineering analysis.

 Since we adopted evaporative emission standards for gaseous-fuel vehicles, we 

have developed new approaches for design-based certification (see, for example, 

40 CFR 1060.240). We request comment on changing the requirements related to 

certifying gaseous-fuel vehicles to design-based certification. This would allow 

for a simpler assessment for certifying these vehicles without changing the 

standards that apply.

(2) Proposed Labeling Provisions

It is crucial that a means exist for allowing field inspectors to identify whether a 

vehicle is certified, and if so, whether it is in the certified configuration. As with engines 

and tractor trailers, we believe an emission control information (ECI) label is a logical 

first step in facilitating this identification. For vocational trucks, the engine will have an 

ECI label that is permanently affixed to the engine and identify the engine as certified for 

use in a certain regulatory subcategory of vehicle (i.e. MHD, etc). If this label is 

obscured during installation, a duplicate label will need to be added in a conspicuous 

location. 
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The vehicle will also have an ECI label listing the test group, engine family, and 

range of tire rolling resistances that the vehicle is certified to use. In addition, if any 

other emission related components are present, such as hybrid powertrains, key

components will also need to be specified on the label. Like the engine label, this will 

need to be permanently affixed to the vehicle in an area that is clearly accessible to the 

owner/operator.

(3) Other Certification Issues

Warranty

As with other heavy-duty engine and vehicle regulatory categories, manufacturers 

of vocational trucks are required to warrant their product to be free from defects that 

would adversely affect emissions. This warranty also covers the failure of emission 

related components for the useful life of the vehicle. For vocational trucks, the two key

emission related components addressed in this proposal are the tires and A/C system. 

Manufacturers of vocational trucks are required to warrant both tires and A/C 

systems to be free from defects at the time of initial sale. As with class 7/8 combination 

tractors, we expect the vehicle manufacturer to only warrant tires the original tires against 

manufacturing or design-related defects. This tire warranty would not cover replacement 

tires or damage from road hazards or improper inflation. In addition, the vehicle 

manufacturer is required to warrant the A/C system for the useful life of the vehicle 

against design or manufacturing defects causing refrigerant leakage in excess of the 

standard.

As with class 7/8 combination tractors, all warranty documentation must be 

submitted to EPA at the time of certification. This should include the warranty statement 

provided to the owner/operator, description of the service repair network, list of covered 

components (both conventional and high-cost), and length of coverage.

Certification Fees

Similar to engine and tractor-trailer vehicle certification, the Agency will assess 

certification fees for vocational trucks. The proceeds from these fees are used to fund the 

compliance and certification activities related to GHG regulation for this industry

segment. In addition to the certification process, other activities funded by certification 

fees include EPA-administered in-use testing, selective enforcement audits, and

confirmatory testing. At this point, the exact costs associated with the heavy-duty vehicle 

GHG compliance are not well known. EPA will assess its compliance program associated 

with this proposal and assess the appropriate level of fees. We anticipate that fees will be 

applied based on test groups, following the light-duty vehicle approach.
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F. Statutory Prohibited Acts

(1) Heavy-Duty Vehicles & Engines

Section 203 of the Clean Air Act describes acts that are prohibited by law. This 

section and associated regulations apply equally to the greenhouse gas standards as to any 

other regulated emission. Acts that are prohibited by section 203 of the Clean Air Act 

include the introduction into commerce or the sale of an engine or vehicle without a 

certificate of conformity, removing or otherwise defeating emission control equipment, 

the sale or installation of devices designed to defeat emission controls, and other actions.

In addition, vehicle manufacturers, or any other party, may not make changes to the 

certified engine that would result in it not being in the certified configuration. 

EPA proposes to include in the regulations a new section that details these 

prohibited acts. Prior regulations, such as the NLEV program, had included such a 

section, and although there is no burden associated with the regulations or any specific 

need to repeat what is in the Clean Air Act, EPA believes that including this language in

the regulations provides clarity and improves the ease of use and completeness of the 

regulations. (see 40 CFR § 86.1854–12).

G. NHTSA Enforcement Penalties

As part of the fuel efficiency improvement program to be created through this 

rulemaking, NHTSA is proposing civil penalties for non-compliance with fuel 

consumption standards. NHTSA’s authority under EISA, as codified at 49 U.S.C. 

32902(k), requires the agency to determine appropriate measurement metrics, test 

procedures, standards, and compliance and enforcement protocols for HD vehicles. 

NHTSA interprets its authority to develop an enforcement program to include the 

authority to determine and assess civil penalties for non-compliance, that would impose 

penalties determined based on the discussion that follows. 

NHTSA proposes that in cases of non-compliance, the agency would establish 

civil penalties based on consideration of the following factors:

 Actual fuel consumption performance related to the applicable standard 

 Estimated cost to comply with the regulation and applicable standard

 Quantity of vehicles or engines not complying

 Manufacturer’s history of non-compliance

 The civil penalty should act as a deterrent

 The financial condition of the manufacturer

 Civil penalties paid for non-compliance of the same vehicles under the EPA 

GHG program
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NHTSA recognizes that EPA also has authority to impose civil penalties for noncompliance with GHG regulations. In the case of non-compliance with fuel consumption 

regulations, NHTSA intends to give consideration to civil penalties imposed by EPA for 

GHG non-compliance.178 

The proposed civil penalty amount NHTSA could impose would not exceed the 

limit that EPA is authorized to impose under the CAA. The potential maximum civil 

penalty for a manufacturer would be calculated as follows:

Equation V-1: Aggregate Maximum Civil Penalty

Aggregate Maximum Civil Penalty for a Non-Compliant Regulatory Class = (CAA Limit) x (production 

volume within the regulatory class)

NHTSA seeks comments related to this proposal for a civil penalty program under 

EISA.

 

178 EPA discussed a similar situation concerning consideration of civil penalties imposed by NHTSA for 

CAFE violations for light-duty vehicles, in the final rule establishing the 2012-2016 MY standards. See 75 

FR 25324, 25482 (May 7, 2010).
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VI. How Would This Proposed Program Impact Fuel 

Consumption, GHG Emissions, and Climate Change?

A. What methodologies did the agencies use to project GHG emissions 

and fuel consumption impacts?

EPA and NHTSA used EPA's official mobile source emissions inventory model 

named Motor Vehicle Emissions Simulator (MOVES2010)179, to estimate emission and 

fuel consumption impacts of these proposed rules. MOVES has capability to take in user 

inputs to modify default data to better estimate emissions for different scenarios, such as 

different regulatory alternatives, state implementation plans (SIPs), geographic locations, 

vehicle activity, and microscale projects. 

The agencies performed multiple MOVES runs to establish reference case and 

control case emission inventories and fuel consumption values. The agencies ran 

MOVES with user input databases that reflected characteristics of the proposed rules, 

such as emissions improvements and recent sales projections. Some post-processing of 

the model output was required to ensure proper results. The agencies ran MOVES for 

non-GHGs, CO2, CH4, and N2O for calendar years 2005 and 2030. Additional runs were 

performed for just the three greenhouse gases and for fuel consumption for every

calendar year from 2014 to 2050, inclusive, which fed the economy-wide modeling, 

monetized benefits estimation, and climate impacts analysis.

The agencies also used MOVES to estimate emissions and fuel consumption 

impacts for the other alternatives considered and described in Section IX.

B. MOVES Analysis

(1) Inputs and assumptions

(a) Reference run updates

Since MOVES2010 vehicle sales and activity data were developed from 

AEO2006, EPA first updated these data using sales and activity estimates from 

AEO2010. EPA also updated the fuel supply information in MOVES to reflect a 100% 

E10 “gasoline” fuel supply to reflect the Renewable Fuels Standard180. MOVES2010 

defaults were used for all other parameters to estimate the reference case emissions 

inventories. 

(b) Control run updates

EPA developed more user input data for MOVES runs to estimate control case 

inventories. The fuel supply update used in the reference case was also used in the 

 

179 MOVES homepage: http://www.epa.gov/otaq/models/moves/index.htm

180 http://www.epa.gov/otaq/fuels/renewablefuels/index.htm
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control case. To account for improvements of engine and vehicle efficiency, EPA 

developed several user inputs to run the control case in MOVES. Since MOVES does 

not operate based on engine FTP cycle results, EPA used the percent reduction in engine 

CO2 emissions expected due to the proposed rules to develop energy inputs for the 

control case runs. Also, EPA used the percent reduction in aerodynamic drag coefficient 

and tire rolling resistance coefficient expected from the proposed rules to develop road 

load input for the control case.

Table VI-1 and Table VI-2 describe the estimated expected reductions from these 

proposed rules, which were input into MOVES for estimating control case emissions 

inventories.

Table VI-1: Estimated reductions in engine CO2 emission rates from these proposed rules

GVWR class Fuel Model years CO2 Reduction from 

2010 MY

HHD (8a-8b) Diesel 2014-2016 3%

2017+ 6%

MHD (6-7) and LHD 4-5 Diesel 2014-2016 5%

2017+ 9%

Gasoline 2016+ 5%

Table VI-2: Estimated reductions in rolling resistance and aerodynamic drag coefficients from these 

proposed rules

Truck type Reduction in tire rolling 

resistance coefficient from 2010 

MY

Reduction in aerodynamic 

drag coefficient from 2010 

MY

Combination long-haul 8.4% 7.2%

Combination short-haul 7.0% 5.3%

Straight trucks, refuse trucks, 

motor homes, transit buses, 

and other vocational trucks

10.0% 0%

Since nearly all 2b/3 pickup trucks and vans will be certified on a chassis 

dynamometer, the CO2 reductions for these vehicles will not be represented as engine and 

road load reduction components, but total vehicle CO2 reductions. These estimated 

reductions are described in Table VI-3.
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Table VI-3: Estimated total vehicle CO2 reductions for 2b/3 pickup trucks and vans

GVWR class Fuel Model year CO2 Reduction from 

reference case

LHD 2b-3 Gasoline 2014 1.5%

2015 2%

2016 4%

2017 6%

2018+ 10%

Diesel 2014 2.3%

2015 3%

2016 6%

2017 9%

2018+ 15%

C. What are the projected reductions in fuel consumption and GHG 

emissions?

 EPA and NHTSA expect significant reductions in GHG emissions and fuel 

consumption from these proposed rules – emission reductions from both downstream 

(tailpipe) and upstream (fuel production and distribution) sources, and fuel consumption 

reductions from more efficient vehicles. Increased vehicle efficiency and reduced vehicle 

fuel consumption would also reduce GHG emissions from upstream sources. The 

following subsections summarize the GHG emissions and fuel consumption reductions 

expected from these proposed rules.

(1) Downstream (tailpipe)

EPA used MOVES to estimate downstream GHG inventories from these proposed 

rules. We expect reductions in CO2 from all heavy-duty vehicle classes. The reductions 

come from engine improvements and road load improvements. EPA expects CH4 and 

N2O emissions to increase very slightly because of VMT rebound and because significant 

vehicle reductions are not expected from these proposed rules. Overall, downstream

GHG emissions (CO2eq) will be reduced significantly, and is described in the following 

subsections. 

For CO2 and fuel consumption, the total energy consumption “pollutant” was run 

in MOVES rather than CO2 itself. The energy was converted to fuel consumption based 
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on fuel heating values used in the development of MOVES emission and energy rates181. 

These values are 122,893 kJ/gallon for gasoline and 138,451 kJ/gallon for diesel. To 

calculate CO2, the agencies assumed a CO2 content of 8,887 g/gallon for gasoline and 

10,180 g/gallon for diesel. 

(a) Model year lifetime

Table VI-4: Reference case and control case GHG (CO2, CH4, and N2O) reductions and fuel savings 

by truck type (2b/3, vocational, and combination) for MY 2014 through 2018 

Downstream GHG 

Reductions (MMT CO2eq)

2b3 pickups/vans 21

Vocational 35

Combination short-haul 45

Combination long-haul 106

(b) Calendar year 

Table VI-5: Annual Downstream GHG Emissions Reductions and Fuel Savings in 2018, 2030, and 

2050

Downstream GHG 

Reductions (MMT 

CO2eq)

Diesel Savings 

(million gallons)

Gasoline Savings 

(million gallons)

2018 20 1,861 71

2030 58 5,412 352

2050 91 8,453 570

(2) Upstream (fuel production and distribution)

Upstream GHG emission reductions associated with the production and 

distribution of fuel were projected using emission factors from DOE’s “Greenhouse 

Gases, Regulated Emissions, and Energy Use in Transportation” (GREET1.8) model, 

with some modifications consistent with the Light Duty Greenhouse Gas rulemaking. 

More information regarding these modifications can be found in the RIA Chapter 5.

These estimates include both international and domestic emission reductions, since 

reductions in foreign exports of finished gasoline and/or crude would make up a 

significant share of the fuel savings resulting from the GHG standards. Thus, significant 

portions of the upstream GHG emission reductions will occur outside of the U.S.; a 

breakdown and discussion of projected international versus domestic reductions is 

 

181 MOVES2004 Energy and Emission Inputs. EPA420-P-05-003, March 2005. 

http://www.epa.gov/otaq/models/ngm/420p05003.pdf
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included in the RIA. GHG emission reductions from upstream sources can be found in 

Table VI-6.

Table VI-6: Annual Upstream GHG Emissions Reductions in 2018, 2030, and 2050

CO2 (MMT) CH4 (MMT 

CO2eq)

N2O (MMT 

CO2eq)

Total GHG (MMT 

CO2eq)

2018 4.5 0.8 0.02 5.3

2030 12.7 2.0 0.06 14.7

2050 19.8 3.1 0.10 22.9

(3) Total (upstream + downstream)

Table VI-7: Annual Total GHG Emissions Reductions and Oil Savings in 2018, 2030, and 2050

GHG Reductions (MMT 

CO2eq)

2018 25

2030 73

2050 114

D. Overview of Climate Change Impacts from GHG Emissions

Once emitted, GHGs that are the subject of this regulation can remain in the 

atmosphere for decades to centuries, meaning that 1) their concentrations become wellmixed throughout the global atmosphere regardless of emission origin, and 2) their 

effects on climate are long lasting. GHG emissions come mainly from the combustion of 

fossil fuels (coal, oil, and gas), with additional contributions from the clearing of forests 

and agricultural activities. The transportation sector represents a significant portion, 28%, 

of U.S. GHG emissions.

182

This section provides a summary of observed and projected changes in GHG 

emissions and associated climate change impacts. The source document for the section 

below is the Technical Support Document (TSD)183 for EPA’s Endangerment and Cause 

or Contribute Findings Under the Clean Air Act.184 Below is the Executive Summary of 

 

182 U.S. EPA (2009) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2007. EPA-430-R-09-

004, Washington, DC.

183 “Technical Support Document for Endangerment and Cause or Contribute Findings for Greenhouse 

Gases Under Section 202(a) of the Clean Air Act” Docket: EPA-HQ-OAR-2009-0472-11292 

184 See 74 FR 66496 (Dec. 15, 2009)-8
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the TSD which provides technical support for the endangerment and cause or contribute 

analyses concerning GHG emissions under section 202(a) of the Clean Air Act. The 

TSD reviews observed and projected changes in climate based on current and projected 

atmospheric GHG concentrations and emissions, as well as the related impacts and risks 

from climate change that are projected in the absence of GHG mitigation actions, 

including this proposal and other U.S. and global actions. The TSD was updated and 

revised based on expert technical review and public comment as part of EPA’s 

rulemaking process for the final Endangerment Findings. The key findings synthesized 

here and the information throughout the TSD are primarily drawn from the assessment 

reports of the Intergovernmental Panel on Climate Change (IPCC), the U.S. Climate 

Change Science Program (CCSP), the U.S. Global Change Research Program 

(USGCRP), and the National Research Council (NRC).185

In May 2010, the National Research Council (NRC) of the U.S. National 

Academy of Sciences published its comprehensive assessment, “Advancing the Science 

of Climate Change186” (NRC, 2010). It concluded that “climate change is occurring, is 

caused largely by human activities, and poses significant risks for—and in many cases is 

already affecting—a broad range of human and natural systems.” Furthermore, the NRC 

stated that this conclusion is based on findings that are “consistent with the conclusions 

of recent assessments by the U.S. Global Change Research Program, the 

Intergovernmental Panel on Climate Change’s Fourth Assessment Report, and other 

assessments of the state of scientific knowledge on climate change.” These are the same 

assessments that served as the primary scientific references underlying the 

Administrator’s Endangerment Finding. Importantly, this recent NRC assessment 

represents another independent and critical inquiry of the state of climate change science, 

separate and apart from the previous IPCC and U.S. Global Change Research Program 

(USGCRP) assessments. The NRC assessment is a clear affirmation that the scientific 

underpinnings of the Administrator’s Endangerment Finding are robust, credible, and 

appropriately characterized by EPA.

(1) Observed Trends in Greenhouse Gas Emissions and Concentrations

The primary long-lived GHGs directly emitted by human activities include carbon 

dioxide (CO2), methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), 

perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). Greenhouse gases have a 

warming effect by trapping heat in the atmosphere that would otherwise escape to space.

In 2007, U.S. GHG emissions were 7,150 teragrams187 of CO2 equivalent188 (TgCO2eq). 

 

185 For a complete list of core references from IPCC, USGCRP/CCSP, NRC and others relied upon for 

development of the TSD for EPA’s Endangerment and Cause or Contribute Findings see section 1(b), 

specifically, Table 1.1 of the TSD. 

186 National Research Council (NRC) (2010). Advancing the Science of Climate Change. National 

Academy Press. Washington, DC.

187 One teragram (Tg) = 1 million metric tons. 1 metric ton = 1,000 kilograms = 1.102 short tons = 2,205 

pounds.

188 Long-lived GHGs are compared and summed together on a CO2-equivalent basis by multiplying each 

gas by its global warming potential (GWP), as estimated by IPCC. In accordance with United Nations 
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The dominant gas emitted is CO2, mostly from fossil fuel combustion. Methane is the 

second largest component of U.S. emissions, followed by N2O and the fluorinated gases 

(HFCs, PFCs, and SF6). Electricity generation is the largest emitting sector (34% of total 

U.S. GHG emissions), followed by transportation (28%) and industry (19%). 

Transportation sources under Section 202(a)189 of the Clean Air Act (passenger 

cars, light duty trucks, other trucks and buses, motorcycles, and passenger cooling)

emitted 1,649 TgCO2eq in 2007, representing 23% of total U.S. GHG emissions. U.S. 

transportation sources under Section 202(a) made up 4.3% of total global GHG emissions 

in 2005,190 which, in addition to the United States as a whole, ranked only behind total 

GHG emissions from China, Russia, and India but ahead of Japan, Brazil, Germany, and 

the rest of the world’s countries. In 2005, total U.S. GHG emissions were responsible for 

18% of global emissions, ranking only behind China, which was responsible for 19% of 

global GHG emissions. The scope of this proposal focuses on GHG emissions under 

Section 202(a) from heavy-duty source categories (see Section VI.C). 

The global atmospheric CO2 concentration has increased about 38% from preindustrial levels to 2009, and almost all of the increase is due to anthropogenic emissions. 

The global atmospheric concentration of CH4 has increased by 149% since pre-industrial 

levels (through 2007); and the N2O concentration has increased by 23% (through 2007). 

The observed concentration increase in these gases can also be attributed primarily to 

anthropogenic emissions. The industrial fluorinated gases, HFCs, PFCs, and SF6, have 

relatively low atmospheric concentrations but the total radiative forcing due to these 

gases is increasing rapidly; these gases are almost entirely anthropogenic in origin. 

Historic data show that current atmospheric concentrations of the two most 

important directly emitted, long-lived GHGs (CO2 and CH4) are well above the natural 

range of atmospheric concentrations compared to at least the last 650,000 years. 

Atmospheric GHG concentrations have been increasing because anthropogenic emissions 

have been outpacing the rate at which GHGs are removed from the atmosphere by natural 

processes over timescales of decades to centuries.

(2) Observed Effects Associated With Global Elevated Concentrations of 

GHGs

Current ambient air concentrations of CO2 and other GHGs remain well below 

published exposure thresholds for any direct adverse health effects, such as respiratory or 

toxic effects.

 

Framework Convention on Climate Change (UNFCCC) reporting procedures, the U.S. quantifies GHG 

emissions using the 100-year timeframe values for GWPs established in the IPCC Second Assessment 

Report.

189 Source categories under Section 202(a) of the Clean Air Act are a subset of source categories considered 

in the transportation sector and do not include emissions from non-highway sources such as boats, rail, 

aircraft, agricultural equipment, construction/mining equipment, and other off-road equipment.

190 More recent emission data are available for the United States and other individual countries, but 2005 is 

the most recent year for which data for all countries and all gases are available.
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The global average net effect of the increase in atmospheric GHG concentrations, 

plus other human activities (e.g., land-use change and aerosol emissions), on the global 

energy balance since 1750 has been one of warming. This total net heating effect, 

referred to as forcing, is estimated to be +1.6 (+0.6 to +2.4) watts per square meter 

(W/m2), with much of the range surrounding this estimate due to uncertainties about the 

cooling and warming effects of aerosols. However, as aerosol forcing has more regional 

variability than the well-mixed, long-lived GHGs, the global average might not capture 

some regional effects. The combined radiative forcing due to the cumulative (i.e., 1750 to 

2005) increase in atmospheric concentrations of CO2, CH4, and N2O is estimated to be 

+2.30 (+2.07 to +2.53) W/m2. The rate of increase in positive radiative forcing due to 

these three GHGs during the industrial era is very likely to have been unprecedented in 

more than 10,000 years.

Warming of the climate system is unequivocal, as is now evident from 

observations of increases in global average air and ocean temperatures, widespread 

melting of snow and ice, and rising global average sea level. Global mean surface 

temperatures have risen by 1.3 ± 0.32F (0.74°C ± 0.18C) over the last 100 years. Eight 

of the 10 warmest years on record have occurred since 2001. Global mean surface 

temperature was higher during the last few decades of the 20th century than during any

comparable period during the preceding four centuries. 

Most of the observed increase in global average temperatures since the mid-20th 

century is very likely due to the observed increase in anthropogenic GHG concentrations. 

Climate model simulations suggest natural forcing alone (i.e., changes in solar irradiance) 

cannot explain the observed warming. 

U.S. temperatures also warmed during the 20th and into the 21st century;

temperatures are now approximately 1.3°F (0.7°C) warmer than at the start of the 20th

century, with an increased rate of warming over the past 30 years. Both the IPCC191 and 

the CCSP reports attributed recent North American warming to elevated GHG 

concentrations. In the CCSP (2008) report,192 the authors find that for North America, 

“more than half of this warming [for the period 1951-2006] is likely the result of humancaused greenhouse gas forcing of climate change.” 

Observations show that changes are occurring in the amount, intensity, frequency

and type of precipitation. Over the contiguous United States, total annual precipitation 

increased by 6.1% from 1901 to 2008. It is likely that there have been increases in the 

 

191 Hegerl, G.C. et al. (2007) Understanding and Attributing Climate Change. In: Climate Change 2007: 

The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the 

Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, 

K.B. Averyt, M. Tignor, and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom 

and New York, NY, USA.

192 CCSP (2008) Reanalysis of Historical Climate Data for Key Atmospheric Features: Implications for 

Attribution of Causes of Observed Change. A Report by the U.S. Climate Change Science Program and the 

Subcommittee on Global Change Research [Randall Dole, Martin Hoerling, and Siegfried Schubert (eds.)]. 

National Oceanic and Atmospheric Administration, National Climatic Data Center, Asheville, NC, 156 pp.
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number of heavy precipitation events within many land regions, even in those where 

there has been a reduction in total precipitation amount, consistent with a warming 

climate.

There is strong evidence that global sea level gradually rose in the 20th century

and is currently rising at an increased rate. It is not clear whether the increasing rate of 

sea level rise is a reflection of short-term variability or an increase in the longer-term 

trend. Nearly all of the Atlantic Ocean shows sea level rise during the last 50 years with 

the rate of rise reaching a maximum (over 2 millimeters [mm] per year) in a band along 

the U.S. east coast running east-northeast.

Satellite data since 1979 show that annual average Arctic sea ice extent has 

shrunk by 4.1% per decade. The size and speed of recent Arctic summer sea ice loss is 

highly anomalous relative to the previous few thousands of years.

Widespread changes in extreme temperatures have been observed in the last 50 

years across all world regions, including the United States. Cold days, cold nights, and 

frost have become less frequent, while hot days, hot nights, and heat waves have become 

more frequent.

Observational evidence from all continents and most oceans shows that many

natural systems are being affected by regional climate changes, particularly temperature 

increases. However, directly attributing specific regional changes in climate to 

emissions of GHGs from human activities is difficult, especially for precipitation.

Ocean CO2 uptake has lowered the average ocean pH (increased acidity) level by

approximately 0.1 since 1750. Consequences for marine ecosystems can include reduced 

calcification by shell-forming organisms, and in the longer term, the dissolution of 

carbonate sediments.

Observations show that climate change is currently affecting U.S. physical and 

biological systems in significant ways. The consistency of these observed changes in 

physical and biological systems and the observed significant warming likely cannot be 

explained entirely due to natural variability or other confounding non-climate factors.

(3) Projections of Future Climate Change with Continued Increases in 

Elevated GHG Concentrations

Most future scenarios that assume no explicit GHG mitigation actions (beyond

those already enacted) project increasing global GHG emissions over the century, with 

climbing GHG concentrations. Carbon dioxide is expected to remain the dominant 

anthropogenic GHG over the course of the 21st century. The radiative forcing associated 

with the non-CO2 GHGs is still significant and increasing over time. 
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Future warming over the course of the 21st century, even under scenarios of lowemission growth, is very likely to be greater than observed warming over the past 

century. According to climate model simulations summarized by the IPCC,

193 through 

about 2030, the global warming rate is affected little by the choice of different future 

emissions scenarios. By the end of the 21st century, projected average global warming 

(compared to average temperature around 1990) varies significantly depending on the 

emission scenario and climate sensitivity assumptions, ranging from 3.2 to 7.2F (1.8 to 

4.0C), with an uncertainty range of 2.0 to 11.5F (1.1 to 6.4C).

All of the United States is very likely to warm during this century, and most areas 

of the United States are expected to warm by more than the global average. The largest 

warming is projected to occur in winter over northern parts of Alaska. In western, central 

and eastern regions of North America, the projected warming has less seasonal variation 

and is not as large, especially near the coast, consistent with less warming over the 

oceans. 

It is very likely that heat waves will become more intense, more frequent, and 

longer lasting in a future warm climate, whereas cold episodes are projected to decrease 

significantly.

Increases in the amount of precipitation are very likely in higher latitudes, while 

decreases are likely in most subtropical latitudes and the southwestern United States, 

continuing observed patterns. The mid-continental area is expected to experience drying 

during summer, indicating a greater risk of drought. 

Intensity of precipitation events is projected to increase in the United States and 

other regions of the world. More intense precipitation is expected to increase the risk of 

flooding and result in greater runoff and erosion that has the potential for adverse water 

quality effects. 

It is likely that hurricanes will become more intense, with stronger peak winds 

and more heavy precipitation associated with ongoing increases of tropical sea surface 

temperatures. Frequency changes in hurricanes are currently too uncertain for confident 

projections.

By the end of the century, global average sea level is projected by IPCC194 to rise 

between 7.1 and 23 inches (18 and 59 centimeter [cm]), relative to around 1990, in the 

absence of increased dynamic ice sheet loss. Recent rapid changes at the edges of the 

 

193 Meehl, G.A. et al. (2007) Global Climate Projections. In: Climate Change 2007: The Physical Science 

Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel 

on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and 

H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

194 IPCC (2007) Summary for Policymakers. In: Climate Change 2007: The Physical Science Basis. 

Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on 

Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and 

H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
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Greenland and West Antarctic ice sheets show acceleration of flow and thinning. While 

an understanding of these ice sheet processes is incomplete, their inclusion in models 

would likely lead to increased sea level projections for the end of the 21st century. 

Sea ice extent is projected to shrink in the Arctic under all IPCC emissions 

scenarios. 

(4) Projected Risks and Impacts Associated With Future Climate Change

Risk to society, ecosystems, and many natural Earth processes increase with 

increases in both the rate and magnitude of climate change. Climate warming may

increase the possibility of large, abrupt regional or global climatic events (e.g., 

disintegration of the Greenland Ice Sheet or collapse of the West Antarctic Ice Sheet). 

The partial deglaciation of Greenland (and possibly West Antarctica) could be triggered 

by a sustained temperature increase of 2 to 7F (1 to 4oC) above 1990 levels. Such 

warming would cause a 13 to 20 feet (4 to 6 meter) rise in sea level, which would occur 

over a time period of centuries to millennia. 

The CCSP195 reports that climate change has the potential to accentuate the 

disparities already evident in the American health care system, as many of the expected 

health effects are likely to fall disproportionately on the poor, the elderly, the disabled, 

and the uninsured. The IPCC196 states with very high confidence that climate change 

impacts on human health in U.S. cities will be compounded by population growth and an 

aging population. 

Severe heat waves are projected to intensify in magnitude and duration over the 

portions of the United States where these events already occur, with potential increases in 

mortality and morbidity, especially among the elderly, young, and frail. 

Some reduction in the risk of death related to extreme cold is expected. It is not 

clear whether reduced mortality from cold will be greater or less than increased heatrelated mortality in the United States due to climate change. 

Increases in regional ozone pollution relative to ozone levels without climate 

change are expected due to higher temperatures and weaker circulation in the United 

States and other world cities relative to air quality levels without climate change. 

Climate change is expected to increase regional ozone pollution, with associated risks in 

 

195 Ebi, K.L., J. Balbus, P.L. Kinney, E. Lipp, D. Mills, M.S. O’Neill, and M. Wilson (2008) Effects of 

Global Change on Human Health. In: Analyses of the effects of global change on human health and welfare 

and human systems. A Report by the U.S. Climate Change Science Program and the Subcommittee on 

Global Change Research. [Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. 

Environmental Protection Agency, Washington, DC, USA, pp. 2-1 to 2-78.

196 Field, C.B. et al. (2007) North America. In: Climate Change 2007: Impacts, Adaptation and 

Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental 

Panel on Climate Change [M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson 

(eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
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respiratory illnesses and premature death. In addition to human health effects, 

tropospheric ozone has significant adverse effects on crop yields, pasture and forest 

growth, and species composition. The directional effect of climate change on ambient 

particulate matter levels remains uncertain. 

Within settlements experiencing climate change, certain parts of the population 

may be especially vulnerable; these include the poor, the elderly, those already in poor 

health, the disabled, those living alone, and/or indigenous populations dependent on one 

or a few resources. Thus, the potential impacts of climate change raise environmental 

justice issues.

The CCSP197 concludes that, with increased CO2 and temperature, the life cycle of 

grain and oilseed crops will likely progress more rapidly. But, as temperature rises, these 

crops will increasingly begin to experience failure, especially if climate variability

increases and precipitation lessens or becomes more variable. Furthermore, the 

marketable yield of many horticultural crops (e.g., tomatoes, onions, fruits) is very likely 

to be more sensitive to climate change than grain and oilseed crops.

Higher temperatures will very likely reduce livestock production during the 

summer season in some areas, but these losses will very likely be partially offset by

warmer temperatures during the winter season.

Cold-water fisheries will likely be negatively affected; warm-water fisheries will 

generally benefit; and the results for cool-water fisheries will be mixed, with gains in the 

northern and losses in the southern portions of ranges.

Climate change has very likely increased the size and number of forest fires, 

insect outbreaks, and tree mortality in the interior West, the Southwest, and Alaska, and 

will continue to do so. Over North America, forest growth and productivity have been 

observed to increase since the middle of the 20th century, in part due to observed climate 

change. Rising CO2 will very likely increase photosynthesis for forests, but the increased 

photosynthesis will likely only increase wood production in young forests on fertile soils. 

The combined effects of expected increased temperature, CO2, nitrogen deposition, 

ozone, and forest disturbance on soil processes and soil carbon storage remain unclear.

Coastal communities and habitats will be increasingly stressed by climate change 

impacts interacting with development and pollution. Sea level is rising along much of the 

U.S. coast, and the rate of change will very likely increase in the future, exacerbating the 

impacts of progressive inundation, storm-surge flooding, and shoreline erosion. Storm 

impacts are likely to be more severe, especially along the Gulf and Atlantic coasts. Salt 

marshes, other coastal habitats, and dependent species are threatened by sea level rise, 

 

197 Backlund, P., A. Janetos, D.S. Schimel, J. Hatfield, M.G. Ryan, S.R. Archer, and D. Lettenmaier (2008) 

Executive Summary. In: The Effects of Climate Change on Agriculture, Land Resources, Water Resources, 

and Biodiversity in the United States. A Report by the U.S. Climate Change Science Program and the 

Subcommittee on Global Change Research. Washington, DC., USA, 362 pp.
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fixed structures blocking landward migration, and changes in vegetation. Population 

growth and rising value of infrastructure in coastal areas increases vulnerability to 

climate variability and future climate change.

Climate change will likely further constrain already overallocated water resources

in some regions of the United States, increasing competition among agricultural, 

municipal, industrial, and ecological uses. Although water management practices in the 

United States are generally advanced, particularly in the West, the reliance on past 

conditions as the basis for current and future planning may no longer be appropriate, as 

climate change increasingly creates conditions well outside of historical observations. 

Rising temperatures will diminish snowpack and increase evaporation, affecting seasonal 

availability of water. In the Great Lakes and major river systems, lower water levels are 

likely to exacerbate challenges relating to water quality, navigation, recreation, 

hydropower generation, water transfers, and binational relationships. Decreased water 

supply and lower water levels are likely to exacerbate challenges relating to aquatic 

navigation in the United States. 

Higher water temperatures, increased precipitation intensity, and longer periods of 

low flows will exacerbate many forms of water pollution, potentially making attainment 

of water quality goals more difficult. As waters become warmer, the aquatic life they

now support will be replaced by other species better adapted to warmer water. In the 

long term, warmer water and changing flow may result in deterioration of aquatic 

ecosystems. 

Ocean acidification is projected to continue, resulting in the reduced biological 

production of marine calcifiers, including corals. 

Climate change is likely to affect U.S. energy use and energy production and 

physical and institutional infrastructures. It will also likely interact with and possibly

exacerbate ongoing environmental change and environmental pressures in settlements, 

particularly in Alaska where indigenous communities are facing major environmental and 

cultural impacts. The U.S. energy sector, which relies heavily on water for hydropower 

and cooling capacity, may be adversely impacted by changes to water supply and quality 

in reservoirs and other water bodies. Water infrastructure, including drinking water and 

wastewater treatment plants, and sewer and stormwater management systems, will be at 

greater risk of flooding, sea level rise and storm surge, low flows, and other factors that 

could impair performance.

Disturbances such as wildfires and insect outbreaks are increasing in the United 

States and are likely to intensify in a warmer future with warmer winters, drier soils, and 

longer growing seasons. Although recent climate trends have increased vegetation 

growth, continuing increases in disturbances are likely to limit carbon storage, facilitate 

invasive species, and disrupt ecosystem services. 

Over the 21st century, changes in climate will cause species to shift north and to 

higher elevations and fundamentally rearrange U.S. ecosystems. Differential capacities 

for range shifts and constraints from development, habitat fragmentation, invasive 
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species, and broken ecological connections will alter ecosystem structure, function, and 

services.

Climate change impacts will vary in nature and magnitude across different 

regions of the United States. 

Sustained high summer temperatures, heat waves, and declining air quality are 

projected in the Northeast,198 Southeast,199 Southwest,200 and Midwest.201 Projected 

climate change would continue to cause loss of sea ice, glacier retreat, permafrost 

thawing, and coastal erosion in Alaska.

Reduced snowpack, earlier spring snowmelt, and increased likelihood of seasonal 

summer droughts are projected in the Northeast, Northwest,202 and Alaska. More severe, 

sustained droughts and water scarcity are projected in the Southeast, Great Plains,203 and 

Southwest. 

The Southeast, Midwest, and Northwest in particular are expected to be impacted 

by an increased frequency of heavy downpours and greater flood risk. 

Ecosystems of the Southeast, Midwest, Great Plains, Southwest, Northwest, and 

Alaska are expected to experience altered distribution of native species (including local 

extinctions), more frequent and intense wildfires, and an increase in insect pest outbreaks 

and invasive species. 

Sea level rise is expected to increase storm surge height and strength, flooding, 

erosion, and wetland loss along the coasts, particularly in the Northeast, Southeast, and 

islands. 

Warmer water temperatures and ocean acidification are expected to degrade 

important aquatic resources of islands and coasts such as coral reefs and fisheries. 

A longer growing season, low levels of warming, and fertilization effects of 

carbon dioxide may benefit certain crop species and forests, particularly in the Northeast 

and Alaska. Projected summer rainfall increases in the Pacific islands may augment 

limited freshwater supplies. Cold-related mortality is projected to decrease, especially in 

 

198 Northeast includes West Virginia, Maryland, Delaware, Pennsylvania, New Jersey, New York, 

Connecticut, Rhode Island, Massachusetts, Vermont, New Hampshire, and Maine.

199 Southeast includes Kentucky, Virginia, Arkansas, Tennessee, North Carolina, South Carolina, southeast 

Texas, Louisiana, Mississippi, Alabama, Georgia, and Florida.

200 Southwest includes California, Nevada, Utah, western Colorado, Arizona, New Mexico (except the 

extreme eastern section), and southwest Texas.

201 The Midwest includes Minnesota, Wisconsin, Michigan, Iowa, Illinois, Indiana, Ohio, and Missouri.

202 The Northwest includes Washington, Idaho, western Montana, and Oregon.

203 The Great Plains includes central and eastern Montana, North Dakota, South Dakota, Wyoming, 

Nebraska, eastern Colorado, Nebraska, Kansas, extreme eastern New Mexico, central Texas, and 

Oklahoma
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the Southeast. In the Midwest in particular, heating oil demand and snow-related traffic 

accidents are expected to decrease.

Climate change impacts in certain regions of the world may exacerbate problems 

that raise humanitarian, trade, and national security issues for the United States. The 

IPCC204 identifies the most vulnerable world regions as the Arctic, because of the effects 

of high rates of projected warming on natural systems; Africa, especially the sub-Saharan 

region, because of current low adaptive capacity as well as climate change; small islands, 

due to high exposure of population and infrastructure to risk of sea level rise and 

increased storm surge; and Asian mega-deltas, such as the Ganges-Brahmaputra and the 

Zhujiang, due to large populations and high exposure to sea level rise, storm surge and 

river flooding. Climate change has been described as a potential threat multiplier with 

regard to national security issues.

E. Changes in Atmospheric CO2 Concentrations, Global Mean 

Temperature, Sea Level Rise, and Ocean pH Associated with the 

Proposal’s GHG Emissions Reductions

EPA examined205 the reductions in CO2 and other GHGs associated with this

proposal and analyzed the projected effects on atmospheric CO2 concentrations, global 

mean surface temperature, sea level rise, and ocean pH which are common variables used 

as indicators of climate change. The analysis projects that this proposal will reduce 

atmospheric concentrations of CO2, global climate warming and sea level rise. Although 

the projected reductions are small in overall magnitude by themselves, they are 

quantifiable and would contribute to reducing the risks associated with climate change. 

EPA therefore determines that the projected reductions in atmospheric CO2, 

global mean temperature and sea level rise are meaningful in the context of this proposal. 

For this proposal, EPA has provided an analysis for projected changes in ocean pH in the 

context of the changes in emissions from this proposal. Based on this analyses, the 

results for projected atmospheric CO2 concentrations are estimated to be reduced by an 

average of XXX ppm, global mean temperature is estimated to be reduced by XXX to 

XXX °C by 2100 and sea-level rise is projected to be reduced by approximately XXX –

XXX cm by 2100. 

 

204 Parry, M.L. et al. (2007) Technical Summary. In: Climate Change 2007: Impacts, Adaptation and 

Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental 

Panel on Climate Change [M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden, and C.E. Hanson 

(eds.)], Cambridge University Press, Cambridge, United Kingdom, pp. 23S78.

205 Using the Model for the Assessment of Greenhouse Gas Induced Climate Change (MAGICC, 

http://www.cgd.ucar.edu/cas/wigley/magicc/), EPA estimated the effects of this proposal’s greenhouse gas 

emissions reductions on global mean temperature and sea level. Please refer to Chapter 8.4 of the RIA for 

additional information.
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(1) Estimated Projected Reductions in Atmospheric CO2 Concentration, 

Global Mean Surface Temperatures, Sea Level Rise, and Ocean pH

EPA estimated changes in the atmospheric CO2 concentration, global mean 

surface temperature, sea level, and ocean pH out to 2100 resulting from the emissions 

reductions in this proposal using the Model for the Assessment of Greenhouse Gas 

Induced Climate Change (MAGICC, version 5.3). This widely-used, peer reviewed 

modeling tool was also used to project temperature and sea level rise under different 

emissions scenarios in the Third and Fourth Assessments of the Intergovernmental Panel 

on Climate Change (IPCC). 

GHG emissions reductions from Section VI.C were applied as net reductions to a 

peer reviewed global reference case (or baseline) emissions scenario to generate an 

emissions scenario specific to this proposal. For the scenario related to this proposal, all 

emissions reductions were assumed to begin in 2014, with zero emissions change in 2013

(from the reference case) followed by emissions linearly increasing to equal the value 

supplied in Section VI.C for 2018 and then continuing to 2100. Details about the 

reference case scenario and how the emissions reductions were applied to generate the 

scenario can be found in the proposal’s RIA, Chapter 8. 

Changes in atmospheric CO2 concentration, temperature, and sea level for both 

the reference case and the emissions scenarios associated with this proposal were 

computed using MAGICC. To calculate the reductions in the atmospheric CO2 

concentrations as well as in temperature and sea level resulting from this proposal, the 

output from the scenario associated with these proposed rules was subtracted from an 

existing Global Change Assessment Model (GCAM, formerly MiniCAM) reference

emission scenario. To capture some key uncertainties in the climate system with the 

MAGICC model, changes in temperature and sea level rise were projected across the 

most current IPCC range for climate sensitivities which ranges from 1.5°C to 6.0°C 

(representing the 90% confidence interval).

206

 This wide range reflects the uncertainty in 

this measure of how much the global mean temperature would rise if the concentration of 

carbon dioxide in the atmosphere were to double. Details about this modeling analysis 

can be found in the RIA Chapter 8.4.

The results of this modeling, summarized in Table VI-8, show small, but 

quantifiable, reductions in atmospheric CO2 concentrations, projected global mean 

surface temperature and sea level resulting from this proposal, across all climate 

sensitivities. As a result of the emission reductions from this proposal, the atmospheric 

CO2 concentration is projected to be reduced by an average of XXX parts per million 

 

206 In IPCC reports, equilibrium climate sensitivity refers to the equilibrium change in the annual mean 

global surface temperature following a doubling of the atmospheric equivalent carbon dioxide 

concentration. The IPCC states that climate sensitivity is “likely” to be in the range of 2°C to 4.5°C, “very 

unlikely” to be less than 1.5°C, and “values substantially higher than 4.5°C cannot be excluded.” IPCC 

WGI, 2007, Climate Change 2007 - The Physical Science Basis, Contribution of Working Group I to the 

Fourth Assessment Report of the IPCC, http://www.ipcc.ch/
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(ppm), the global mean temperature is projected to be reduced by approximately XXXXXX°C by 2100, and global mean sea level rise is projected to be reduced by

approximately XXX-XXX cm by 2100. The reductions are small relative to the IPCC’s 

2100 “best estimates” for global mean temperature increases (1.8 – 4.0oC) and sea level

rise (0.20-0.59m) for all global GHG emissions sources for a range of emissions 

scenarios. EPA used a peer reviewed model, the MAGICC model, to do this analysis. 

Further discussion of EPA’s modeling analysis is found in the draft RIA.

Table VI-8: Effect of GHG Emissions Reductions On Projected Changes in Global Climate for the 

Proposal (for climate sensitivities ranging from 1.5-6°C)

Measure Units Year Projected Change

Atmospheric 

CO2

Concentration

ppm 2100

Global Mean 

Surface 

Temperature

o C 2100

Sea Level Rise cm 2100

Ocean pH pH units 2100

As a substantial portion of CO2 emitted into the atmosphere is not removed by 

natural processes for millennia, each unit of CO2 not emitted into the atmosphere avoids 

essentially permanent climate change on centennial time scales. Though the magnitude 

of the avoided climate change projected here is small, these reductions would represent a 

reduction in the adverse risks associated with climate change (though these risks were not 

formally estimated for this proposal) across all climate sensitivities. 

The IPCC207 has noted that ocean acidification due to the direct effects of elevated 

CO2 concentrations will impair a wide range of planktonic and other marine organisms 

that use aragonite to make their shells or skeletons. EPA used the Program CO2SYS,208

version 1.05 to estimate projected changes in tropical ocean pH based on the atmospheric

CO2 concentration reductions resulting from this proposal. The program performs 

calculations relating parameters of the carbon dioxide (CO2) system in seawater. EPA 

used the program to calculate ocean pH as a function of atmospheric CO2, among other 

specified input conditions. Based on the projected atmospheric CO2 concentration

reductions (average of XX ppm by 2100) that would result from this proposal, the 

program calculates an increase in ocean pH of about 0.00XX pH units in 2100. Thus, this 

 

207 Fischlin, A. et al. (2007) Ecosystems, their Properties, Goods, and Services. In: Climate Change 2007: 

Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report 

of the Intergovernmental Panel on Climate Change [M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der 

Linden and C.E. Hanson (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, 

NY, USA.

208 Lewis, E., and D. W. R. Wallace. 1998. Program Developed for CO2 System Calculations. 

ORNL/CDIAC-105. Carbon Dioxide Information Analysis Center, Oak Ridge National Laboratory, U.S. 

Department of Energy, Oak Ridge, Tennessee.
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analysis indicates the projected decrease in atmospheric CO2 concentrations from today’s 

proposal would result in an increase in ocean pH. 

EPA’s analysis of the proposed rules’ effect on global climate conditions is 

intended to quantify these potential reductions using the best available science. While 

EPA’s modeling results of the effect of this proposal alone show small differences in 

climate effects (CO2 concentration, temperature, sea-level rise, ocean pH), when 

expressed in terms of global climate endpoints and global GHG emissions, they yield 

results that are repeatable and consistent within the modeling frameworks used.

VII. How Would This Proposal Impact Non-GHG Emissions 

and Their Associated Effects?

A. Emissions Inventory Impacts

(1) Upstream Impacts of the Program

Increasing efficiency in heavy-duty vehicles would result in reduced fuel demand 

and therefore reductions in the emissions associated with all processes involved in getting 

petroleum to the pump. These projected upstream emission impacts on criteria pollutants 

are summarized in Table VII-1. The upstream reductions would grow over time as the 

fleet turns over to cleaner CO2 vehicles, so that by 2030 VOC would decrease by 4,272

tons, NOX by 9,856 tons, CO by 3,277 tons and PM2.5 by 1,348 tons. Table VII-2 shows 

the corresponding projected impacts on upstream air toxic emissions in 2030. 

Formaldehyde would decrease by XX tons, benzene by XX tons, acetaldehyde by XX

tons, acrolein by XX tons, and 1,3-butadiene by XX tons. 
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Table VII-1: Overall estimated upstream impacts on criteria pollutants for calendar years 2018, 

2030, and 2050 (short tons)

Calendar Year NOX VOC CO PM2.5

2018 -5,710 -1,639 -1,954 -855

2030 -9,856 -4,272 -3,277 -1,348

2050 -15,421 -6,778 -5,127 -2,108

Table VII-2: Overall estimated upstream impacts on air toxics for calendar years 2018, 2030, and 

2050 (short tons)

Calendar 

Year

Benzene 1,3-butadiene Formaldehyde Acetaldehyde Acrolein

2018

2030

2050

To project these impacts, EPA estimated the impact of reduced petroleum 

volumes on the extraction and transportation of crude oil as well as the production and 

distribution of finished gasoline and diesel. For the purpose of assessing domestic-only

emission reductions it was necessary to estimate the fraction of fuel savings attributable

to domestic finished gasoline and diesel, and of this fuel what fraction is produced from 

domestic crude. For this analysis EPA estimated that 50 percent of fuel savings is 

attributable to domestic finished gasoline and diesel and that 90 percent of this gasoline

and diesel originated from imported crude. Emission factors for most upstream emission 

sources are based on the GREET1.8 model, developed by DOE’s Argonne National 

Laboratory but in some cases the GREET values were modified or updated by EPA to be

consistent with the National Emission Inventory (NEI). These updates are consistent with 

those used for the upstream analysis included in the Light Duty Greenhouse Gas 

rulemaking. More information on the development of the emission factors used in this 

analysis can be found in draft RIA Chapter XX.

(2) Downstream Impacts of the Program

While these proposed rules do not regulate non-GHG pollutants, EPA expects 

reductions in downstream emissions of most non-GHG pollutants. These pollutants 

include NOX, SO2, CO, and HC. The primary reason for this is the improvements in road 

load (aerodynamics and tire rolling resistance for Class 7 and Class 8 vehicles) proposed 

in this proposal. Another reason is that emissions from certain pollutants (e.g. SO2) are 

proportional to fuel consumption. For vehicle types not affected by road load 

improvements, non-GHG emissions may increase very slightly due to VMT rebound. 

EPA also anticipates the use of auxiliary power units (APUs) in combination long-haul 

trucks for GHG reduction purposes during extended idling. These units exhibit different 

non-GHG emissions characteristics compared to the on-road engines they would replace 

during extended idling. EPA used MOVES to determine non-GHG emissions inventories 

for reference and control cases. The improvements in road load, use of APUs, and VMT 

rebound were included in the MOVES runs and post-processing.
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Table VII-3: Overall estimated downstream impacts on criteria pollutants for calendar years 2018, 

2030, and 2050. Most of the reductions are through projected increased APU use.

Calendar 

Year

Downstream 

NOX (short tons)

Downstream VOC 

(short tons)

Downstream 

CO (short tons)

Downstream 

PM2.5 (short tons)

2018 -96,764 -22,004 -23,329 662*

2030 -231,631 -52,577 -53,709 1,568

2050 -326,491 -74,157 -75,083 2,210

*Note: Positive number means an emissions increase from reference case to control case. 

For PM2.5, the projected widespread use of APUs leads to higher PM2.5, as APUs are 

required meet much less stringent PM2.5 standards than on-road engines.

Table VII-4: Overall estimated downstream impacts on air toxics for calendar years 2018, 2030, and 

2050 (short tons)

Calendar 

Year

Benzene 1,3-butadiene Formaldehyde Acetaldehyde Acrolein

2018

2030

2050

(3) Total Impacts of the Program

As shown in Table VII-5, the agencies estimate that this program would result in 

reductions of NOX, VOC, CO, and SOX. For NOX, VOC, and CO, much of the net 

reductions are realized through the use of APUs, which emit these pollutants at a lower 

rate than on-road engines during extended idle operation. The downstream increase in 

PM2.5 due to APU use is mostly negated by upstream PM2.5 reductions, though our 

calculations show a slight net increase in 2030 and 2050. Additional reductions are 

achieved in all pollutants through reduced road load (improved aerodynamics and tire 

rolling resistance), which reduces the amount of work required to travel a given distance. 

For SOX, downstream emissions are roughly proportional to fuel consumption; therefore 

a decrease is seen in both upstream and downstream sources. 
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CY NOX VOC CO PM2.5

short tons % short tons % short tons % short tons %

2018 -102,474 -5.0% -23,643 -7.6% -25,283 -0.79% -193 -0.26%

2030 -241,487 -19.6% -56,849 -27.0% -56,986 -2.13% 220 0.75%

2050 -341,912 -21.6% -80,935 -30.7% -80,210 -2.47% 102 0.28%

Table VII-5: Overall estimated total impacts (upstream plus downstream) on criteria pollutants for 

calendar years 2018, 2030, and 2050. Results are shown in both total short tons and percent change 

from reference case to control case.

Table VII-6: Overall estimated downstream impacts on air toxics for calendar years 2018, 2030, and 

2050 (short tons)

B. Health Effects of Non-GHG Pollutants

In this section we discuss health effects associated with exposure to some of the 

criteria and air toxic pollutants impacted by the proposed heavy-duty vehicle standards. 

(1) Particulate Matter

(a) Background

Particulate matter is a generic term for a broad class of chemically and physically 

diverse substances. It can be principally characterized as discrete particles that exist in the 

condensed (liquid or solid) phase spanning several orders of magnitude in size. Since 

1987, EPA has delineated that subset of inhalable particles small enough to penetrate to 

the thoracic region (including the tracheobronchial and alveolar regions) of the 

respiratory tract (referred to as thoracic particles). Current National Ambient Air Quality

Standards (NAAQS) use PM2.5 as the indicator for fine particles (with PM2.5 referring to 

particles with a nominal mean aerodynamic diameter less than or equal to 2.5 μm), and 

use PM10 as the indicator for purposes of regulating the coarse fraction of PM10 (referred 

to as thoracic coarse particles or coarse-fraction particles; generally including particles 

with a nominal mean aerodynamic diameter greater than 2.5 μm and less than or equal to 

10 μm, or PM10-2.5). Ultrafine particles are a subset of fine particles, generally less than 

100 nanometers (0.1 μm) in aerodynamic diameter. 

Fine particles are produced primarily by combustion processes and by

transformations of gaseous emissions (e.g., SOX, NOX and VOC) in the atmosphere. The 

chemical and physical properties of PM2.5 may vary greatly with time, region, 

CY Benzene 1,3-butadiene Formaldehyde Acetaldehyde Acrolein

short tons % short tons % short tons % short tons % short tons %

2018

2030

2050
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meteorology, and source category. Thus, PM2.5 may include a complex mixture of 

different pollutants including sulfates, nitrates, organic compounds, elemental carbon and 

metal compounds. These particles can remain in the atmosphere for days to weeks and 

travel hundreds to thousands of kilometers.

(b) Health Effects of PM

Scientific studies show ambient PM is associated with a series of adverse health 

effects. These health effects are discussed in detail in EPA’s Integrated Science 

Assessment for Particulate Matter (ISA).

209

 Further discussion of health effects 

associated with PM can also be found in the draft RIA for this proposal. The ISA 

summarizes evidence associated with PM2.5, PM10-2.5, and ultrafine particles (UFPs).

The ISA concludes that health effects associated with short-term exposures (hours 

to days) to ambient PM2.5 include mortality, cardiovascular effects, such as altered 

vasomotor function and hospital admissions and emergency department visits for 

ischemic heart disease and congestive heart failure, and respiratory effects, such as 

exacerbation of asthma symptoms in children and hospital admissions and emergency

department visits for chronic obstructive pulmonary disease (COPD) and respiratory

infections.

210

 The ISA notes that long-term exposure to PM2.5 (months to years) is 

associated with the development/progression of cardiovascular disease, premature 

mortality, and respiratory effects, including reduced lung function growth, increased 

respiratory symptoms, and asthma development.211 The ISA concludes that that the 

currently available scientific evidence from epidemiologic, controlled human exposure, 

and toxicological studies supports a causal association between short- and long-term 

exposures to PM2.5 and cardiovascular effects and mortality. Furthermore, the ISA 

concludes that the collective evidence supports likely causal associations between shortand long-term PM2.5 exposures and respiratory effects. The ISA also concludes that the 

scientific evidence is suggestive of a causal association for reproductive and 

developmental effects and cancer, mutagenicity, and genotoxicity and long-term 

exposure to PM2.5.

212

For PM10-2.5, the ISA concludes that the current evidence is suggestive of a causal 

relationship between short-term exposures and cardiovascular effects, such as 

hospitalization for ischemic heart disease. There is also suggestive evidence of a causal 

relationship between short-term PM10-2.5 exposure and mortality and respiratory effects. 

Data are inadequate to draw conclusions regarding the health effects associated with 

long-term exposure to PM10-2.5.

213

 

209 U.S. EPA (2009) Integrated Science Assessment for Particulate Matter (Final Report). U.S. 

Environmental Protection Agency, Washington, DC, EPA/600/R-08/139F, Docket EPA-HQ-OAR-2009-

0472-11295 

210 See U.S. EPA, 2009 Final PM ISA at.Note 209, at Section 2.3.1.1.

211 See U.S. EPA 2009 Final PM ISA at Note 209, at page 2-12, Sections 7.3.1.1 and 7.3.2.1.

212 See U.S. EPA 2009 Final PM ISA at Note 209, at Section 2.3.2.

213 See U.S. EPA 2009 Final PM ISA at Note 209, at.Section 2.3.4, Table 2-6.
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For UFPs, the ISA concludes that there is suggestive evidence of a causal 

relationship between short-term exposures and cardiovascular effects, such as changes in 

heart rhythm and blood vessel function. It also concludes that there is suggestive 

evidence of association between short-term exposure to UFPs and respiratory effects.

Data are inadequate to draw conclusions regarding the health effects associated with 

long-term exposure to UFP’s.214

(2) Ozone

(a) Background

Ground-level ozone pollution is typically formed by the reaction of VOC and 

NOX in the lower atmosphere in the presence of sunlight. These pollutants, often referred 

to as ozone precursors, are emitted by many types of pollution sources, such as highway

and nonroad motor vehicles and engines, power plants, chemical plants, refineries, 

makers of consumer and commercial products, industrial facilities, and smaller area 

sources.215

The science of ozone formation, transport, and accumulation is complex. 

Ground-level ozone is produced and destroyed in a cyclical set of chemical reactions, 

many of which are sensitive to temperature and sunlight. When ambient temperatures 

and sunlight levels remain high for several days and the air is relatively stagnant, ozone 

and its precursors can build up and result in more ozone than typically occurs on a single 

high-temperature day. Ozone can be transported hundreds of miles downwind from 

precursor emissions, resulting in elevated ozone levels even in areas with low local VOC 

or NOX emissions.

(b) Health Effects of Ozone

The health and welfare effects of ozone are well documented and are assessed in 

EPA’s 2006 Air Quality Criteria Document (ozone AQCD) and 2007 Staff Paper.216,217 

People who are more susceptible to effects associated with exposure to ozone can include 

children, the elderly, and individuals with respiratory disease such as asthma. Those with 

greater exposures to ozone, for instance due to time spent outdoors (e.g., children and 

outdoor workers), are of particular concern. Ozone can irritate the respiratory system, 

causing coughing, throat irritation, and breathing discomfort. Ozone can reduce lung 

function and cause pulmonary inflammation in healthy individuals. Ozone can also 

aggravate asthma, leading to more asthma attacks that require medical attention and/or 

 

214 See U.S. EPA 2009 Final PM ISA at Note 209, at Section 2.3.5, Table 2-6.

215 Area sources are defined as sources that emit less than 10 tons per year of a criteria or hazardous air 

pollutant or less than 25 tons per year of a combination of pollutants.

216 U.S. EPA. (2006). Air Quality Criteria for Ozone and Related Photochemical Oxidants (Final). 

EPA/600/R-05/004aF-cF. Washington, DC: U.S. EPA.

217 U.S. EPA. (2007). Review of the National Ambient Air Quality Standards for Ozone: Policy 

Assessment of Scientific and Technical Information, OAQPS Staff Paper. EPA-452/R-07-003. 

Washington, DC, U.S. EPA. Docket EPA-HQ-OAR-2009-0472-0105 through -0106.
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the use of additional medication. Thus, ambient ozone may cause both healthy and 

asthmatic individuals to limit their outdoor activities. In addition, there is suggestive 

evidence of a contribution of ozone to cardiovascular-related morbidity and highly 

suggestive evidence that short-term ozone exposure directly or indirectly contributes to 

non-accidental and cardiopulmonary-related mortality, but additional research is needed 

to clarify the underlying mechanisms causing these effects. In a recent report on the 

estimation of ozone-related premature mortality published by the National Research 

Council (NRC), a panel of experts and reviewers concluded that short-term exposure to 

ambient ozone is likely to contribute to premature deaths and that ozone-related mortality

should be included in estimates of the health benefits of reducing ozone exposure.218 

Animal toxicological evidence indicates that with repeated exposure, ozone can inflame 

and damage the lining of the lungs, which may lead to permanent changes in lung tissue 

and irreversible reductions in lung function. The respiratory effects observed in 

controlled human exposure studies and animal studies are coherent with the evidence 

from epidemiologic studies supporting a causal relationship between acute ambient ozone 

exposures and increased respiratory-related emergency room visits and hospitalizations in 

the warm season. In addition, there is suggestive evidence of a contribution of ozone to 

cardiovascular-related morbidity and non-accidental and cardiopulmonary mortality.

(3) Nitrogen Oxides and Sulfur Oxides

(a) Background

Nitrogen dioxide (NO2) is a member of the NOX family of gases. Most NO2 is 

formed in the air through the oxidation of nitric oxide (NO) emitted when fuel is burned 

at a high temperature. SO2, a member of the sulfur oxide (SOX) family of gases, is 

formed from burning fuels containing sulfur (e.g., coal or oil derived), extracting gasoline 

from oil, or extracting metals from ore. 

SO2 and NO2 can dissolve in water droplets and further oxidize to form sulfuric 

and nitric acid which react with ammonia to form sulfates and nitrates, both of which are 

important components of ambient PM. The health effects of ambient PM are discussed in 

Section VII. B. (1) (b) of this preamble. NOX along with non-methane hydrocarbon 

(NMHC) are the two major precursors of ozone. The health effects of ozone are covered 

in Section VII. B. (2) (b).

(b) Health Effects of NO2

Information on the health effects of NO2 can be found in the EPA Integrated 

Science Assessment (ISA) for Nitrogen Oxides.219 The EPA has concluded that the 

 

218 National Research Council (NRC), 2008. Estimating Mortality Risk Reduction and Economic Benefits 

from Controlling Ozone Air Pollution. The National Academies Press: Washington, D.C. Docket EPAHQ-OAR-2009-0472-0322

219 U.S. EPA (2008). Integrated Science Assessment for Oxides of Nitrogen – Health Criteria (Final 

Report). EPA/600/R-08/071. Washington, DC: U.S.EPA. Docket EPA-HQ-OAR-2009-0472-0350.
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findings of epidemiologic, controlled human exposure, and animal toxicological studies 

provide evidence that is sufficient to infer a likely causal relationship between respiratory

effects and short-term NO2 exposure. The ISA concludes that the strongest evidence for 

such a relationship comes from epidemiologic studies of respiratory effects including 

symptoms, emergency department visits, and hospital admissions. The ISA also draws 

two broad conclusions regarding airway responsiveness following NO2 exposure. First, 

the ISA concludes that NO2 exposure may enhance the sensitivity to allergen-induced 

decrements in lung function and increase the allergen-induced airway inflammatory

response following 30-minute exposures of asthmatics to NO2 concentrations as low as 

0.26 ppm. In addition, small but significant increases in non-specific airway

hyperresponsiveness were reported following 1-hour exposures of asthmatics to 0.1 ppm 

NO2. Second, exposure to NO2 has been found to enhance the inherent responsiveness of 

the airway to subsequent nonspecific challenges in controlled human exposure studies of 

asthmatic subjects. Enhanced airway responsiveness could have important clinical 

implications for asthmatics since transient increases in airway responsiveness following 

NO2 exposure have the potential to increase symptoms and worsen asthma control. 

Together, the epidemiologic and experimental data sets form a plausible, consistent, and 

coherent description of a relationship between NO2 exposures and an array of adverse 

health effects that range from the onset of respiratory symptoms to hospital admission. 

Although the weight of evidence supporting a causal relationship is somewhat 

less certain than that associated with respiratory morbidity, NO2 has also been linked to 

other health endpoints. These include all-cause (nonaccidental) mortality, hospital 

admissions or emergency department visits for cardiovascular disease, and decrements in 

lung function growth associated with chronic exposure.

(c) Health Effects of SO2

Information on the health effects of SO2 can be found in the EPA Integrated 

Science Assessment for Sulfur Oxides.220 SO2 has long been known to cause adverse 

respiratory health effects, particularly among individuals with asthma. Other potentially 

sensitive groups include children and the elderly. During periods of elevated ventilation, 

asthmatics may experience symptomatic bronchoconstriction within minutes of exposure. 

Following an extensive evaluation of health evidence from epidemiologic and laboratory

studies, the EPA has concluded that there is a causal relationship between respiratory

health effects and short-term exposure to SO2. Separately, based on an evaluation of the 

epidemiologic evidence of associations between short-term exposure to SO2 and 

mortality, the EPA has concluded that the overall evidence is suggestive of a causal 

relationship between short-term exposure to SO2 and mortality.

 

220 U.S. EPA. (2008). Integrated Science Assessment (ISA) for Sulfur Oxides – Health Criteria (Final 

Report). EPA/600/R-08/047F. Washington, DC: U.S. Environmental Protection Agency. Docket EPA-HQOAR-2009-0472-0335.
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(4) Carbon Monoxide

Information on the health effects of carbon monoxide (CO) can be found in the 

EPA Integrated Science Assessment (ISA) for Carbon Monoxide.

221

 The ISA concludes 

that ambient concentrations of CO are associated with a number of adverse health 

effects.222 This section provides a summary of the health effects associated with 

exposure to ambient concentrations of CO.

223

 

Human clinical 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 show 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 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 inconsistent neural and behavioral effects 

following low-level CO exposures. The ISA concludes 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 epidemiologic and animal toxicological studies cited in the ISA have 

evaluated associations between CO exposure and birth outcomes such as preterm birth or 

cardiac birth defects. The epidemiologic studies provide limited evidence of a COinduced effect on preterm births and birth defects, with weak evidence for a decrease in 

birth weight. Animal toxicological studies have found associations between perinatal CO 

exposure and decrements in birth weight, as well as other developmental outcomes. The 

ISA concludes these studies are suggestive of a causal relationship between long-term 

exposures to CO and developmental effects and birth outcomes.

 

221 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

222 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. 

223 Personal exposure includes contributions from many sources, and in many different environments. 

Total personal exposure to CO includes both ambient and nonambient components; and both components 

may contribute to adverse health effects.
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Epidemiologic studies provide evidence of effects on respiratory morbidity such 

as changes in pulmonary function, respiratory symptoms, and hospital admissions 

associated with ambient CO concentrations. 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 ISA concludes that the evidence is suggestive of a causal relationship between shortterm CO exposure and respiratory morbidity, and inadequate to conclude that a causal 

relationship exists between long-term exposure and respiratory morbidity. 

Finally, the ISA concludes that the epidemiologic evidence is suggestive of a 

causal relationship between short-term exposures to CO and mortality. Epidemiologic 

studies provide evidence of an association 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 which 

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 ISA also 

concludes that there is not likely to be a causal relationship between relevant long-term 

exposures to CO and mortality.

(5) Air Toxics

Heavy-duty vehicle emissions contribute to ambient levels of air toxics known or 

suspected as human or animal carcinogens, or that have noncancer health effects. The 

population experiences an elevated risk of cancer and other noncancer health effects from 

exposure to the class of pollutants known collectively as “air toxics.”224 These 

compounds include, but are not limited to, benzene, 1,3-butadiene, formaldehyde, 

acetaldehyde, acrolein, diesel particulate matter and exhaust organic gases, polycyclic 

organic matter (POM), and naphthalene. These compounds were identified as national or 

regional risk drivers in past National-scale Air Toxics Assessments (NATA) and have 

significant inventory contributions from mobile sources.225 

(a) Diesel Exhaust

Heavy-duty diesel engines emit diesel exhaust (DE), a complex mixture 

composed of 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, 

 

224 U. S. EPA. 2002 National-Scale Air Toxics Assessment. 

http://www.epa.gov/ttn/atw/nata12002/risksum.html Docket EPA-HQ-OAR-2009-0472-11322

225 U.S. EPA .2009. National-Scale Air Toxics Assessment for 2002. http://www.epa.gov/ttn/atw/nata2002/ 

Docket EPA-HQ-OAR-2009-0472-11321
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including aldehydes, benzene and 1,3-butadiene. The diesel particulate matter (DPM) 

present in DE consists of fine particles (< 2.5 μm), including a subgroup with a large 

number of ultrafine particles (< 0.1 μm). 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 (POM), 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, accelerate, decelerate), 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 for some of the compounds present in diesel exhaust ranges from hours to 

days.226

(i) Diesel Exhaust: Potential Cancer Effects

In EPA’s 2002 Diesel Health Assessment Document (Diesel HAD),227 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. A number of 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) have made 

similar classifications. However, EPA also concluded in the Diesel HAD that it is not 

possible currently to calculate a cancer unit risk for diesel exhaust due to a variety of 

factors that limit the current studies, such as limited quantitative exposure histories in 

occupational groups investigated for lung cancer.

For the Diesel HAD, EPA reviewed 22 epidemiologic studies on the subject of the 

carcinogenicity of workers exposed to diesel exhaust in various occupations, finding 

increased lung cancer risk, although not always statistically significant, in 8 out of 10 

cohort studies and 10 out of 12 case-control studies within several industries. Relative 

risk for lung cancer associated with exposure ranged from 1.2 to 1.5, although a few 

studies show relative risks as high as 2.6. Additionally, the Diesel HAD also relied on 

two independent meta-analyses, which examined 23 and 30 occupational studies 

respectively, which found statistically significant increases in smoking-adjusted relative 

lung cancer risk associated with exposure to diesel exhaust of 1.33 to 1.47. These metaanalyses demonstrate the effect of pooling many studies and in this case show the 

 

226 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. 

227 See U.S. EPA (2002) Diesel HAD at Note 226, at pp. 1-1, 1-2.
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positive relationship between diesel exhaust exposure and lung cancer across a variety of 

diesel exhaust-exposed occupations.

228,229

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 possible risk range by comparing a typical environmental exposure level 

for highway diesel sources to a selected range of occupational exposure levels. The 

occupationally observed risks were then proportionally scaled according to the exposure 

ratios to obtain an estimate of the possible environmental risk. A number of calculations 

are needed to accomplish this, and these can be seen in the EPA Diesel HAD. The 

outcome was that environmental risks from diesel exhaust exposure could range from a 

low of 10-4to 10-5to as high as 10-3, reflecting the range of occupational exposures that 

could be associated with the relative and absolute risk levels observed in the occupational 

studies. Because of uncertainties, the analysis acknowledged that the risks could be 

lower than 10-4or 10-5, and a zero risk from diesel exhaust exposure was not ruled out.

(ii) Diesel Exhaust: Other Health Effects

Noncancer health effects of acute and chronic exposure to diesel exhaust 

emissions are also of concern to the EPA. EPA derived a diesel exhaust reference 

concentration (RfC) from consideration of four well-conducted chronic rat inhalation 

studies showing adverse pulmonary effects.230,231,232,233 The RfC is 5 μg/m3for diesel 

exhaust as measured by DPM. This RfC does not consider allergenic effects such as 

those associated with asthma or immunologic effects. There is growing evidence, 

discussed in the Diesel HAD, that exposure to diesel exhaust can exacerbate these effects, 

but the exposure-response data are presently lacking to derive an RfC. The EPA Diesel 

HAD states, “With DPM [diesel particulate matter] being a ubiquitous component of 

ambient PM, there is an uncertainty about the adequacy of the existing DE [diesel 

exhaust] noncancer database to identify all of the pertinent DE-caused noncancer health 

hazards.” (p. 9-19). The Diesel HAD concludes “that acute exposure to DE [diesel 

exhaust] has been associated with irritation of the eye, nose, and throat, respiratory

 

228 Bhatia, R., Lopipero, P., Smith, A. (1998). Diesel exposure and lung cancer. Epidemiology, 9(1), 84-91.

229 Lipsett, M. Campleman, S. (1999). Occupational exposure to diesel exhaust and lung cancer: a metaanalysis. Am J Public Health, 80(7), 1009-1017.

230 Ishinishi, N. Kuwabara, N. Takaki, Y., et al. (1988). Long-term inhalation experiments on diesel 

exhaust. In: Diesel exhaust and health risks. Results of the HERP studies. Ibaraki, Japan: Research 

Committee for HERP Studies; pp.11-84.

231 Heinrich, U., Fuhst, R., Rittinghausen, S., et al. (1995). Chronic inhalation exposure of Wistar rats and 

two different strains of mice to diesel engine exhaust, carbon black, and titanium dioxide. Inhal Toxicol, 7,

553-556.

232 Mauderly, J.L., Jones, R.K., Griffith, W.C., et al. (1987). Diesel exhaust is a pulmonary carcinogen in 

rats exposed chronically by inhalation. Fundam. Appl. Toxicol., 9, 208-221.

233 Nikula, K.J., Snipes, M.B., Barr, E.B., et al. (1995). Comparative pulmonary toxicities and 

carcinogenicities of chronically inhaled diesel exhaust and carbon black in F344 rats. Fundam. Appl. 

Toxicol, 25, 80-94..
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symptoms (cough and phlegm), and neurophysiological symptoms such as headache, 

lightheadedness, nausea, vomiting, and numbness or tingling of the extremities.”234

(iii) Ambient PM2.5 Levels and Exposure to Diesel Exhaust PM

The Diesel HAD also briefly summarizes health effects associated with ambient 

PM and discusses the EPA’s annual PM2.5 NAAQS of 15 μg/m3. There is a much more 

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 

and premature mortality effects of PM2.5 as a whole.

(iv) Diesel Exhaust PM Exposures

Exposure of people to diesel exhaust depends on their various activities, the time 

spent in those activities, the locations where these activities occur, and the levels of diesel 

exhaust pollutants in those locations. The major difference between ambient levels of 

diesel particulate and exposure levels for diesel particulate is that exposure accounts for a 

person moving from location to location, proximity to the emission source, and whether 

the exposure occurs in an enclosed environment.

Occupational Exposures

Occupational exposures to diesel exhaust from mobile sources can be several 

orders of magnitude greater than typical exposures in the non-occupationally exposed 

population.

Over the years, diesel particulate exposures have been measured for a number of 

occupational groups. A wide range of exposures have been reported, from 2 μg/m3to 

1,280 μg/m3, for a variety of occupations. As discussed in the Diesel HAD, the National 

Institute of Occupational Safety and Health (NIOSH) has estimated a total of 1,400,000 

workers are occupationally exposed to diesel exhaust from on-road and nonroad vehicles.

Elevated Concentrations and Ambient Exposures in Mobile Source-Impacted Areas

Regions immediately downwind of highways or truck stops may experience 

elevated ambient concentrations of directly-emitted PM2.5 from diesel engines. Due to 

the unique nature of highways and truck stops, emissions from a large number of diesel 

engines are concentrated in a small area. Studies near roadways with high truck traffic 

indicate higher concentrations of components of diesel PM than other locations.235,236,237 

 

234 See U.S. EPA (2002), Diesel HAD at Note 226, at p. 9-9.

235 Zhu, Y.; Hinds, W.C.; Kim, S.; Shen, S.; Sioutas, C. (2002) Study of ultrafine particles near a major 

highway with heavy-duty diesel traffic. Atmospheric Environment 36: 4323-4335.

236 Lena, T.S; Ochieng, V.; Holguín-Veras, J.; Kinney, P.L. (2002) Elemental carbon and PM2.5 levels in 

an urban community heavily impacted by truck traffic. Environ Health Perspect 110: 1009-1015.
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High ambient particle concentrations have also been reported near trucking terminals, 

truck stops, and bus garages.238,239,240 Additional discussion of exposure and health 

effects associated with traffic is included below in Section VII. B. (5) (j). 

(b) Benzene

The EPA’s IRIS database lists benzene as a known human carcinogen (causing 

leukemia) by all routes of exposure, and concludes that exposure is associated with 

additional health effects, including genetic changes in both humans and animals and 

increased proliferation of bone marrow cells in mice.

241,242,243 EPA states in its IRIS 

database that data indicate a causal relationship between benzene exposure and acute 

lymphocytic leukemia and suggest a relationship between benzene exposure and chronic 

non-lymphocytic leukemia and chronic lymphocytic leukemia. The International Agency

for Research on Carcinogens (IARC) has determined that benzene is a human carcinogen 

and the U.S. Department of Health and Human Services (DHHS) has characterized 

benzene as a known human carcinogen.244,245

A number of adverse noncancer health effects including blood disorders, such as 

preleukemia and aplastic anemia, have also been associated with long-term exposure to 

benzene.246,247 The most sensitive noncancer effect observed in humans, based on current 

 

237 Soliman, A.S.M.; Jacko, J.B.; Palmer, G.M. (2006) Development of an empirical model to estimate realworld fine particulate matter emission factors: the Traffic Air Quality model. J Air & Waste Manage 

Assoc 56: 1540-1549.

238 Davis, M.E.; Smith, T.J.; Laden, F.; Hart, J.E.; Ryan, L.M.; Garshick, E. (2006) Modeling particle 

exposure in U.S. trucking terminals. Environ Sci Techol 40: 4226-4232.

239 Miller, T.L.; Fu, J.S.; Hromis, B.; Storey, J.M. (2007) Diesel truck idling emissions – measurments at a 

PM2.5 hot spot. Proceedings of the Annual Conference of the Transportation Research Board, paper no. 07-

2609.

240 Ramachandran, G.; Paulsen, D.; Watts, W.; Kittelson, D. (2005) Mass, surface area, and number metrics 

in diesel occupational exposure assessment. J Environ Monit 7: 728-735.

241 U.S. EPA. 2000. Integrated Risk Information System File for Benzene. This material is available 

electronically at http://www.epa.gov/iris/subst/0276.htm. Docket EPA-HQ-OAR-2009-0472-1659.

242 International Agency for Research on Cancer (IARC). 1982. Monographs on the evaluation of 

carcinogenic risk of chemicals to humans, Volume 29. Some industrial chemicals and dyestuffs, World 

Health Organization, Lyon, France, p. 345-389. Docket EPA-HQ-OAR-2009-0472-0366

243 Irons, R.D.; Stillman, W.S.; Colagiovanni, D.B.; Henry, V.A. 1992. Synergistic action of the benzene 

metabolite hydroquinone on myelopoietic stimulating activity of granulocyte/macrophage colonystimulating factor in vitro, Proc. Natl. Acad. Sci. 89:3691-3695. Docket EPA-HQ-OAR-2009-0472-0370.

244 International Agency for Research on Cancer (IARC). 1982. Monographs on the evaluation of 

carcinogenic risk of chemicals to humans, Volume 29. Some industrial chemicals and dyestuffs, World 

Health Organization, Lyon, France. Docket EPA-HQ-OAR-2009-0472-0366

245 U.S. Department of Health and Human Services National Toxicology Program 11th Report on 

Carcinogens available at: http://ntp.niehs.nih.gov/go/16183. 

246 Aksoy, M. (1989). Hematotoxicity and carcinogenicity of benzene. Environ. Health Perspect. 82: 193-

197. Docket EPA-HQ-OAR-2009-0472-0368.

247 Goldstein, B.D. (1988). Benzene toxicity. Occupational medicine. State of the Art Reviews. 3: 541-554. 

Docket EPA-HQ-OAR-2009-0472-0325.
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data, is the depression of the absolute lymphocyte count in blood.248, 249 In addition, 

recent work, including studies sponsored by the Health Effects Institute (HEI), provides 

evidence that biochemical responses are occurring at lower levels of benzene exposure 

than previously known.250,251,252,253 EPA’s IRIS program has not yet evaluated these new 

data.

(c) 1,3-Butadiene

EPA has characterized 1,3-butadiene as carcinogenic to humans by

inhalation.254,255 The IARC has determined that 1,3-butadiene is a human carcinogen and 

the U.S. DHHS has characterized 1,3-butadiene as a known human carcinogen.256,257 

There are numerous studies consistently demonstrating that 1,3-butadiene is metabolized 

into genotoxic metabolites by experimental animals and humans. The specific 

mechanisms of 1,3-butadiene-induced carcinogenesis are unknown; however, the 

scientific evidence strongly suggests that the carcinogenic effects are mediated by 

 

248 Rothman, N., G.L. Li, M. Dosemeci, W.E. Bechtold, G.E. Marti, Y.Z. Wang, M. Linet, L.Q. Xi, W. Lu, 

M.T. Smith, N. Titenko-Holland, L.P. Zhang, W. Blot, S.N. Yin, and R.B. Hayes (1996) Hematotoxicity 

among Chinese workers heavily exposed to benzene. Am. J. Ind. Med. 29: 236-246. Docket EPA-HQOAR-2009-0472-0326.

249 U.S. EPA (2002) Toxicological Review of Benzene (Noncancer Effects). Environmental Protection 

Agency, Integrated Risk Information System (IRIS), Research and Development, National Center for 

Environmental Assessment, Washington DC. This material is available electronically at 

http://www.epa.gov/iris/subst/0276.htm. Docket EPA-HQ-OAR-2009-0472-0327.

250 Qu, O.; Shore, R.; Li, G.; Jin, X.; Chen, C.L.; Cohen, B.; Melikian, A.; Eastmond, D.; Rappaport, S.; Li, 

H.; Rupa, D.; Suramaya, R.; Songnian, W.; Huifant, Y.; Meng, M.; Winnik, M.; Kwok, E.; Li, Y.; Mu, 

R.; Xu, B.; Zhang, X.; Li, K. (2003) HEI Report 115, Validation & Evaluation of Biomarkers in Workers 

Exposed to Benzene in China. Docket EPA-HQ-OAR-2009-0472-0328. 

251 Qu, Q., R. Shore, G. Li, X. Jin, L.C. Chen, B. Cohen, et al. (2002) Hematological changes among 

Chinese workers with a broad range of benzene exposures. Am. J. Industr. Med. 42: 275-285. Docket 

EPA-HQ-OAR-2009-0472-0329.

252 Lan, Qing, Zhang, L., Li, G., Vermeulen, R., et al. (2004) Hematotoxically in Workers Exposed to Low

Levels of Benzene. Science 306: 1774-1776. Docket EPA-HQ-OAR-2009-0472-0330.

253 Turtletaub, K.W. and Mani, C. (2003) Benzene metabolism in rodents at doses relevant to human 

exposure from Urban Air. Research Reports Health Effect Inst. Report No.113. Docket EPA-HQ-OAR2009-0472-0385.

254 U.S. EPA (2002) Health Assessment of 1,3-Butadiene. Office of Research and Development, National 

Center for Environmental Assessment, Washington Office, Washington, DC. Report No. EPA600-P-98-

001F. This document is available electronically at http://www.epa.gov/iris/supdocs/buta-sup.pdf. Docket 

EPA-HQ-OAR-2009-0472-0386.

255 U.S. EPA (2002) Full IRIS Summary for 1,3-butadiene (CASRN 106-99-0). Environmental Protection 

Agency, Integrated Risk Information System (IRIS), Research and Development, National Center for 

Environmental Assessment, Washington, DC http://www.epa.gov/iris/subst/0139.htm. Docket EPA-HQOAR-2009-0472-1660

256 International Agency for Research on Cancer (IARC) (1999) Monographs on the evaluation of 

carcinogenic risk of chemicals to humans, Volume 71, Re-evaluation of some organic chemicals, hydrazine 

and hydrogen peroxide and Volume 97 (in preparation), World Health Organization, Lyon, France. Docket 

EPA-HQ-OAR-2009-0472-0387

257 U.S. Department of Health and Human Services (2005) National Toxicology Program 11th Report on 

Carcinogens available at: ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E7FCE50709CB4C932. 
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genotoxic metabolites. Animal data suggest that females may be more sensitive than 

males for cancer effects associated with 1,3-butadiene exposure; there are insufficient 

data in humans from which to draw conclusions about sensitive subpopulations. 1,3-

butadiene also causes a variety of reproductive and developmental effects in mice; no 

human data on these effects are available. The most sensitive effect was ovarian atrophy

observed in a lifetime bioassay of female mice.258

(d) Formaldehyde

Since 1987, EPA has classified formaldehyde as a probable human carcinogen 

based on evidence in humans and in rats, mice, hamsters, and monkeys.259 EPA is 

currently reviewing recently published epidemiological data. For instance, research 

conducted by the National Cancer Institute (NCI) found an increased risk of 

nasopharyngeal cancer and lymphohematopoietic malignancies such as leukemia among 

workers exposed to formaldehyde.260, 261 In an analysis of the lymphohematopoietic 

cancer mortality from an extended follow-up of these workers, NCI confirmed an 

association between lymphohematopoietic cancer risk and peak exposures.262 A recent 

National Institute of Occupational Safety and Health (NIOSH) study of garment workers 

also found increased risk of death due to leukemia among workers exposed to 

formaldehyde.263 Extended follow-up of a cohort of British chemical workers did not 

find evidence of an increase in nasopharyngeal or lymphohematopoietic cancers, but a 

continuing statistically significant excess in lung cancers was reported.264 Recently, the 

IARC re-classified formaldehyde as a human carcinogen (Group 1).265 

 

258 Bevan, C.; Stadler, J.C.; Elliot, G.S.; et al. (1996) Subchronic toxicity of 4-vinylcyclohexene in rats and 

mice by inhalation. Fundam. Appl. Toxicol. 32:1-10. Docket EPA-HQ-OAR-2009-0472-0388.

259 U.S. EPA (1987) Assessment of Health Risks to Garment Workers and Certain Home Residents from 

Exposure to Formaldehyde, Office of Pesticides and Toxic Substances, April 1987. Docket EPA-HQ-OAR2009-0472-0389.

260 Hauptmann, M..; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Blair, A. 2003. Mortality from 

lymphohematopoetic malignancies among workers in formaldehyde industries. Journal of the National 

Cancer Institute 95: 1615-1623. Docket EPA-HQ-OAR-2009-0472-0336.

261 Hauptmann, M..; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Blair, A. 2004. Mortality from solid 

cancers among workers in formaldehyde industries. American Journal of Epidemiology 159: 1117-1130. 

Docket EPA-HQ-OAR-2009-0472-0337.

262 Beane Freeman, L. E.; Blair, A.; Lubin, J. H.; Stewart, P. A.; Hayes, R. B.; Hoover, R. N.; Hauptmann, 

M. 2009. Mortality from lymphohematopoietic malignancies among workers in formaldehyde industries: 

The National Cancer Institute cohort. J. National Cancer Inst. 101: 751-761. Docket EPA-HQ-OAR-2009-

0472-0338.

263 Pinkerton, L. E. 2004. Mortality among a cohort of garment workers exposed to formaldehyde: an 

update. Occup. Environ. Med. 61: 193-200. Docket EPA-HQ-OAR-2009-0472-0339.

264 Coggon, D, EC Harris, J Poole, KT Palmer. 2003. Extended follow-up of a cohort of British chemical 

workers exposed to formaldehyde. J National Cancer Inst. 95:1608-1615. Docket EPA-HQ-OAR-2009-

0472-0340.

265 International Agency for Research on Cancer (IARC). 2006. Formaldehyde, 2-Butoxyethanol and 1-tertButoxypropan-2-ol. Volume 88. (in preparation), World Health Organization, Lyon, France. Docket EPAHQ-OAR-2009-0472-1164
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Formaldehyde exposure also causes a range of noncancer health effects, including 

irritation of the eyes (burning and watering of the eyes), nose and throat. Effects from 

repeated exposure in humans include respiratory tract irritation, chronic bronchitis and 

nasal epithelial lesions such as metaplasia and loss of cilia. Animal studies suggest that 

formaldehyde may also cause airway inflammation – including eosinophil infiltration into 

the airways. There are several studies that suggest that formaldehyde may increase the 

risk of asthma – particularly in the young.266,267

(e) Acetaldehyde

Acetaldehyde is classified in EPA’s IRIS database as a probable human 

carcinogen, based on nasal tumors in rats, and is considered toxic by the inhalation, oral, 

and intravenous routes.

268

 Acetaldehyde is reasonably anticipated to be a human 

carcinogen by the U.S. DHHS in the 11th Report on Carcinogens and is classified as 

possibly carcinogenic to humans (Group 2B) by the IARC.269,270 EPA is currently

conducting a reassessment of cancer risk from inhalation exposure to acetaldehyde.

The primary noncancer effects of exposure to acetaldehyde vapors include 

irritation of the eyes, skin, and respiratory tract.271 In short-term (4 week) rat studies, 

degeneration of olfactory epithelium was observed at various concentration levels of 

acetaldehyde exposure.

272, 273

 Data from these studies were used by EPA to develop an 

inhalation reference concentration. Some asthmatics have been shown to be a sensitive 

subpopulation to decrements in functional expiratory volume (FEV1 test) and 

 

266 Agency for Toxic Substances and Disease Registry (ATSDR). 1999. Toxicological profile for 

Formaldehyde. Atlanta, GA: U.S. Department of Health and Human Services, Public Health Service. 

http://www.atsdr.cdc.gov/toxprofiles/tp111.html Docket EPA-HQ-OAR-2009-0472-1191.

267 WHO (2002) Concise International Chemical Assessment Document 40: Formaldehyde. Published 

under the joint sponsorship of the United Nations Environment Programme, the International Labour 

Organization, and the World Health Organization, and produced within the framework of the InterOrganization Programme for the Sound Management of Chemicals. Geneva. Docket EPA-HQ-OAR-2009-

0472-1199.

268 U.S. EPA. 1991. Integrated Risk Information System File of Acetaldehyde. Research and Development, 

National Center for Environmental Assessment, Washington, DC. This material is available electronically 

at http://www.epa.gov/iris/subst/0290.htm. Docket EPA-HQ-OAR-2009-0472-0390.

269 U.S. Department of Health and Human Services National Toxicology Program 11th Report on 

Carcinogens available at: ntp.niehs.nih.gov/index.cfm?objectid=32BA9724-F1F6-975E7FCE50709CB4C932.

270 International Agency for Research on Cancer (IARC). 1999. Re-evaluation of some organic chemicals, 

hydrazine, and hydrogen peroxide. IARC Monographs on the Evaluation of Carcinogenic Risk of 

Chemical to Humans, Vol 71. Lyon, France. Docket EPA-HQ-OAR-2009-0472-0387

271 U.S. EPA. 1991. Integrated Risk Information System File of Acetaldehyde. This material is available 

electronically at http://www.epa.gov/iris/subst/0290.htm.

272 Appleman, L. M., R. A. Woutersen, V. J. Feron, R. N. Hooftman, and W. R. F. Notten. 1986. Effects 

of the variable versus fixed exposure levels on the toxicity of acetaldehyde in rats. J. Appl. Toxicol. 6: 331-

336.

273 Appleman, L.M., R.A. Woutersen, and V.J. Feron. 1982. Inhalation toxicity of acetaldehyde in rats. I. 

Acute and subacute studies. Toxicology. 23: 293-297. Docket EPA-HQ-OAR-2009-0472-0392.
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bronchoconstriction upon acetaldehyde inhalation.274 The agency is currently conducting 

a reassessment of the health hazards from inhalation exposure to acetaldehyde. 

(f) Acrolein

Acrolein is extremely acrid and irritating to humans when inhaled, with acute 

exposure resulting in upper respiratory tract irritation, mucus hypersecretion and 

congestion. The intense irritancy of this carbonyl has been demonstrated during 

controlled tests in human subjects, who suffer intolerable eye and nasal mucosal sensory

reactions within minutes of exposure.275 These data and additional studies regarding 

acute effects of human exposure to acrolein are summarized in EPA’s 2003 IRIS Human 

Health Assessment for acrolein.276 Evidence available from studies in humans indicate 

that levels as low as 0.09 ppm (0.21 mg/m3) for five minutes may elicit subjective 

complaints of eye irritation with increasing concentrations leading to more extensive eye, 

nose and respiratory symptoms.277 Lesions to the lungs and upper respiratory tract of 

rats, rabbits, and hamsters have been observed after subchronic exposure to acrolein.278 

Acute exposure effects in animal studies report bronchial hyper-responsiveness.279 In a 

recent study, the acute respiratory irritant effects of exposure to 1.1 ppm acrolein were 

more pronounced in mice with allergic airway disease by comparison to non-diseased 

mice which also showed decreases in respiratory rate.280 Based on these animal data and 

demonstration of similar effects in humans (e.g., reduction in respiratory rate), 

individuals with compromised respiratory function (e.g., emphysema, asthma) are 

expected to be at increased risk of developing adverse responses to strong respiratory

irritants such as acrolein. 

EPA determined in 2003 that the human carcinogenic potential of acrolein could 

not be determined because the available data were inadequate. No information was 

available on the carcinogenic effects of acrolein in humans and the animal data provided 

 

274 Myou, S.; Fujimura, M.; Nishi K.; Ohka, T.; and Matsuda, T. 1993. Aerosolized acetaldehyde induces 

histamine-mediated bronchoconstriction in asthmatics. Am. Rev. Respir.Dis.148(4 Pt 1): 940-3. Docket 

EPA-HQ-OAR-2009-0472-0408.

275 U.S. EPA (U.S. Environmental Protection Agency). (2003) Toxicological review of acrolein in support 

of summary information on Integrated Risk Information System (IRIS) National Center for Environmental 

Assessment, Washington, DC. EPA/635/R-03/003. p. 10. Available online at: 

http://www.epa.gov/ncea/iris/toxreviews/0364tr.pdf.

276 See U.S. EPA 2003 Toxicological review of acrolein, Note 275, above. 

277 See U.S. EPA 2003 Toxicological review of acrolein, Note 275, at p. 11.

278 Integrated Risk Information System File of Acrolein. Office of Research and Development, National 

Center for Environmental Assessment, Washington, DC. This material is available at 

http://www.epa.gov/iris/subst/0364.htm Docket EPA-HQ-OAR-2009-0472-0391.

279 See U.S. 2003 Toxicological review of acrolein, Note 275, at p. 15. 

280 Morris JB, Symanowicz PT, Olsen JE, et al. 2003. Immediate sensory nerve-mediated respiratory 

responses to irritants in healthy and allergic airway-diseased mice. J Appl Physiol 94(4):1563-1571. Docket 

EPA-HQ-OAR-2009-0472-0396.
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inadequate evidence of carcinogenicity.

281

 The IARC determined in 1995 that acrolein 

was not classifiable as to its carcinogenicity in humans.

282

(g) Polycyclic Organic Matter (POM)

POM is generally defined as a large class of organic compounds which have 

multiple benzene rings and a boiling point greater than 100 degrees Celsius. Many of the 

compounds included in the class of compounds known as POM are classified by EPA as 

probable human carcinogens based on animal data. One of these compounds, 

naphthalene, is discussed separately below. Polycyclic aromatic hydrocarbons (PAHs) 

are a subset of POM that contain only hydrogen and carbon atoms. A number of PAHs 

are known or suspected carcinogens. Recent studies have found that maternal exposures 

to PAHs (a subclass of POM) in a population of pregnant women were associated with 

several adverse birth outcomes, including low birth weight and reduced length at birth, as 

well as impaired cognitive development at age three.283,284 EPA has not yet evaluated 

these recent studies.

(h) Naphthalene

Naphthalene is found in small quantities in gasoline and diesel fuels. 

Naphthalene emissions have been measured in larger quantities in both gasoline and 

diesel exhaust compared with evaporative emissions from mobile sources, indicating it is 

primarily a product of combustion. EPA released an external review draft of a 

reassessment of the inhalation carcinogenicity of naphthalene based on a number of 

recent animal carcinogenicity studies.285 The draft reassessment completed external peer 

review.286 Based on external peer review comments received, additional analyses are 

being undertaken. This external review draft does not represent official agency opinion 

and was released solely for the purposes of external peer review and public comment. 

 

281 U.S. EPA. 2003. Integrated Risk Information System File of Acrolein. Research and Development, 

National Center for Environmental Assessment, Washington, DC. This material is available at 

http://www.epa.gov/iris/subst/0364.htm

282 International Agency for Research on Cancer (IARC). 1995. Monographs on the evaluation of 

carcinogenic risk of chemicals to humans, Volume 63. Dry cleaning, some chlorinated solvents and other 

industrial chemicals, World Health Organization, Lyon, France. Docket EPA-HQ-OAR-2009-0472-0393

283 Perera, F.P.; Rauh, V.; Tsai, W-Y.; et al. (2002) Effect of transplacental exposure to environmental 

pollutants on birth outcomes in a multiethnic population. Environ Health Perspect. 111: 201-205. Docket 

EPA-HQ-OAR-2009-0472-0372.

284 Perera, F.P.; Rauh, V.; Whyatt, R.M.; Tsai, W.Y.; Tang, D.; Diaz, D.; Hoepner, L.; Barr, D.; Tu, Y.H.; 

Camann, D.; Kinney, P. (2006) Effect of prenatal exposure to airborne polycyclic aromatic hydrocarbons 

on neurodevelopment in the first 3 years of life among inner-city children. Environ Health Perspect 114: 

1287-1292. Docket EPA-HQ-OAR-2009-0472-0373.

285 U. S. EPA. 2004. Toxicological Review of Naphthalene (Reassessment of the Inhalation Cancer Risk), 

Environmental Protection Agency, Integrated Risk Information System, Research and Development, 

National Center for Environmental Assessment, Washington, DC. This material is available electronically 

at http://www.epa.gov/iris/subst/0436.htm. Docket EPA-HQ-OAR-2009-0472-0272.

286 Oak Ridge Institute for Science and Education. (2004). External Peer Review for the IRIS 

Reassessment of the Inhalation Carcinogenicity of Naphthalene. August 2004. 

http://cfpub.epa.gov/ncea/cfm/recordisplay.cfm?deid=84403 Docket EPA-HQ-OAR-2009-0472-0273.
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The National Toxicology Program listed naphthalene as "reasonably anticipated to be a 

human carcinogen" in 2004 on the basis of bioassays reporting clear evidence of 

carcinogenicity in rats and some evidence of carcinogenicity in mice.287 California EPA 

has released a new risk assessment for naphthalene, and the IARC has reevaluated 

naphthalene and re-classified it as Group 2B: possibly carcinogenic to humans.288 

Naphthalene also causes a number of chronic non-cancer effects in animals, including 

abnormal cell changes and growth in respiratory and nasal tissues.289

(i) Other Air Toxics

In addition to the compounds described above, other compounds in gaseous 

hydrocarbon and PM emissions from heavy-duty vehicles will be affected by these

proposed rules. Mobile source air toxic compounds that would potentially be impacted 

include ethylbenzene, propionaldehyde, toluene, and xylene. Information regarding the 

health effects of these compounds can be found in EPA’s IRIS database.290

(j) Exposure and Health Effects Associated with Traffic

Populations who live, work, or attend school near major roads experience 

elevated exposure concentrations to a wide range of air pollutants, as well as higher risks 

for a number of adverse health effects. While the previous sections of this preamble have 

focused on the health effects associated with individual criteria pollutants or air toxics, 

this section discusses the mixture of different exposures near major roadways, rather than 

the effects of any single pollutant. As such, this section emphasizes traffic-related air 

pollution, in general, as the relevant indicator of exposure rather than any particular 

pollutant.

Concentrations of many traffic-generated air pollutants are elevated for up to 300-

500 meters downwind of roads with high traffic volumes.291 Numerous sources on roads 

contribute to elevated roadside concentrations, including exhaust and evaporative 

emissions, and resuspension of road dust and tire and brake wear. Concentrations of 

several criteria and hazardous air pollutants are elevated near major roads. Furthermore, 

different semi-volatile organic compounds and chemical components of particulate 

 

287 National Toxicology Program (NTP). (2004). 11th Report on Carcinogens. Public Health Service, U.S. 

Department of Health and Human Services, Research Triangle Park, NC. Available from: http://ntpserver.niehs.nih.gov.

288 International Agency for Research on Cancer (IARC). (2002). Monographs on the Evaluation of the 

Carcinogenic Risk of Chemicals for Humans. Vol. 82. Lyon, France. Docket EPA-HQ-OAR-2009-0472-

0274.

289 U. S. EPA. 1998. Toxicological Review of Naphthalene, Environmental Protection Agency, Integrated 

Risk Information System, Research and Development, National Center for Environmental Assessment, 

Washington, DC. This material is available electronically at http://www.epa.gov/iris/subst/0436.htm 

290 U.S. EPA Integrated Risk Information System (IRIS) database is available at: www.epa.gov/iris 

291 Zhou, Y.; Levy, J.I. (2007) Factors influencing the spatial extent of mobile source air pollution impacts: 

a meta-analysis. BMC Public Health 7: 89. doi:10.1186/1471-2458-7-89
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matter, including elemental carbon, organic material, and trace metals, have been 

reported at higher concentrations near major roads.

 Populations near major roads experience greater risk of certain adverse health 

effects. The Health Effects Institute published a report on the health effects of trafficrelated air pollution.292

 It concluded that evidence is “sufficient to infer the presence of a 

causal association” between traffic exposure and exacerbation of childhood asthma 

symptoms. The HEI report also concludes that the evidence is either “sufficient” or 

“suggestive but not sufficient” for a causal association between traffic exposure and new 

childhood asthma cases. A review of asthma studies by Salam et al. (2008) reaches 

similar conclusions.293 The HEI report also concludes that there is “suggestive” evidence 

for pulmonary function deficits associated with traffic exposure, but concluded that there 

is “inadequate and insufficient” evidence for causal associations with respiratory health 

care utilization, adult-onset asthma, chronic obstructive pulmonary disease (COPD) 

symptoms, and allergy. A review by Holguin (2008) notes that the effects of traffic on 

asthma may be modified by nutrition status, medication use, and genetic factors.294

The HEI report also concludes that evidence is “suggestive” of a causal 

association between traffic exposure and all-cause and cardiovascular mortality. There is 

also evidence of an association between traffic-related air pollutants and cardiovascular 

effects such as changes in heart rhythm, heart attack, and cardiovascular disease. The 

HEI report characterizes this evidence as “suggestive” of a causal association, and an 

independent epidemiological literature review by Adar and Kaufman (2007) concludes 

that there is “consistent evidence” linking traffic-related pollution and adverse 

cardiovascular health outcomes.295

Some studies have reported associations between traffic exposure and other health 

effects, such as birth outcomes (e.g., low birth weight) and childhood cancer. The HEI 

report concludes that there is currently “inadequate and insufficient” evidence for a 

causal association between these effects and traffic exposure. A review by RaaschouNielsen and Reynolds (2006) concluded that evidence of an association between 

childhood cancer and traffic-related air pollutants is weak, but noted the inability to draw 

firm conclusions based on limited evidence.296

There is a large population in the U.S. living in close proximity of major roads. 

According to the Census Bureau’s American Housing Survey for 2007, approximately 20 

 

292 HEI Panel on the Health Effects of Air Pollution. (2010) Traffic-related air pollution: a critical review 

of the literature on emissions, exposure, and health effects. [Online at www.healtheffects.org]

293 Salam, M.T.; Islam, T.; Gilliland, F.D. (2008) Recent evidence for adverse effects of residential 

proximity to traffic sources on asthma. Current Opin Pulm Med 14: 3-8.

294 Holguin, F. (2008) Traffic, outdoor air pollution, and asthma. Immunol Allergy Clinics North Am 28: 

577-588.

295 Adar, S.D.; Kaufman, J.D. (2007) Cardiovascular disease and air pollutants: evaluating and improving 

epidemiological data implicating traffic exposure. Inhal Toxicol 19: 135-149.

296 Raaschou-Nielsen, O.; Reynolds, P. (2006) Air pollution and childhood cancer: a review of the 

epidemiological literature. Int J Cancer 118: 2920-2929.
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million residences in the U.S., 15.6% of all homes, are located within 300 feet (91 m) of a 

highway with 4+ lanes, a railroad, or an airport.297 Therefore, at current population of 

approximately 309 million, assuming that population and housing are similarly

distributed, there are over 48 million people in the U.S. living near such sources. The 

HEI report also notes that in two North American cities, Los Angeles and Toronto, over 

40% of each city’s population live within 500 meters of a highway or 100 meters of a 

major road. It also notes that about 33% of each city’s population resides within 50 

meters of major roads. Together, the evidence suggests that a large U.S. population lives 

in areas with elevated traffic-related air pollution.

People living near roads are often socioeconomically disadvantaged. According 

to the 2007 American Housing Survey, a renter-occupied property is over twice as likely 

as an owner-occupied property to be located near a highway with 4+ lanes, railroad or 

airport. In the same survey, the median household income of rental housing occupants 

was less than half that of owner-occupants ($28,921/$59,886). Numerous studies in 

individual urban areas report higher levels of traffic-related air pollutants in areas with 

high minority or poor populations.298,299,300

Students may also be exposed in situations where schools are located near major 

roads. In a study of nine metropolitan areas across the U.S., Appatova et al. (2008) found 

that on average greater than 33% of schools were located within 400 m of an Interstate, 

U.S., or state highway, while 12% were located within 100 m.301 The study also found 

that among the metropolitan areas studied, schools in the Eastern U.S. were more often 

sited near major roadways than schools in the Western U.S.

Demographic studies of students in schools near major roadways suggest that this 

population is more likely than the general student population to be of non-white race or 

Hispanic ethnicity, and more often live in low socioeconomic status locations. 302,303,304 

 

297 U.S. Census Bureau (2008) American Housing Survey for the United States in 2007. Series H-150 

(National Data), Table 1A-7. [Accessed at 

http://www.census.gov/hhes/www/housing/ahs/ahs07/ahs07.html on January 22, 2009]

298 Lena, T.S.; Ochieng, V.; Carter, M.; Holguín-Veras, J.; Kinney, P.L. (2002) Elemental carbon and 

PM2.5 levels in an urban community heavily impacted by truck traffic. Environ Health Perspect 110: 

1009-1015.

299 Wier, M.; Sciammas, C.; Seto, E.; Bhatia, R.; Rivard, T. (2009) Health, traffic, and environmental 

justice: collaborative research and community action in San Francisco, California. Am J Public Health 99: 

S499-S504.

300 Forkenbrock, D.J. and L.A. Schweitzer, Environmental Justice and Transportation Investment Policy. 

Iowa City: University of Iowa, 1997.

301 Appatova, A.S.; Ryan, P.H.; LeMasters, G.K.; Grinshpun, S.A. (2008) Proximal exposure of public 

schools and students to major roadways: a nationwide U.S. survey. J Environ Plan Mgmt

302 Green, R.S.; Smorodinsky, S.; Kim, J.J.; McLaughlin, R.; Ostro, B. (2004) Proximity of California 

public schools to busy roads. Environ Health Perspect 112: 61-66.

303 Houston, D.; Ong, P.; Wu, J.; Winer, A. (2006) Proximity of licensed child care facilities to nearroadway vehicle pollution. Am J Public Health 96: 1611-1617.

304 Wu, Y.; Batterman, S. (2006) Proximity of schools in Detroit, Michigan to automobile and truck traffic. 

J Exposure Sci Environ Epidemiol 16: 457-470.
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There is some inconsistency in the evidence, which may be due to different local 

development patterns and measures of traffic and geographic scale used in the studies.301 

C. Environmental Effects of Non-GHG Pollutants

In this section we discuss some of the environmental effects of PM and its 

precursors such as visibility impairment, atmospheric deposition, and materials damage 

and soiling, as well as environmental effects associated with the presence of ozone in the 

ambient air, such as impacts on plants, including trees, agronomic crops and urban 

ornamentals, and environmental effects associated with air toxics.

(1) Visibility

Visibility can be defined as the degree to which the atmosphere is transparent to 

visible light.305 Visibility impairment is caused by light scattering and absorption by suspended 

particles and gases. 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 

2009 PM ISA.306

EPA is pursuing a two-part strategy to address visibility. First, EPA has 

concluded that PM2.5 causes adverse effects on visibility in various locations, depending 

on PM concentrations and factors such as chemical composition and average relative

humidity, and has set secondary PM2.5 standards.307 The secondary PM2.5 standards act in 

conjunction with the regional haze program. EPA’s regional haze rule (64 FR 35714) 

was put in place in July 1999 to protect the visibility in Mandatory Class I Federal areas. 

There are 156 national parks, forests and wilderness areas categorized as Mandatory

Class I Federal areas (62 FR 38680-81, July 18, 1997).308 Visibility can be said to be 

impaired in both PM2.5 nonattainment areas and Mandatory Class I Federal areas.

 

305 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. Docket EPA-HQ-OAR-2005-0161. This book can be viewed on the 

National Academy Press Website at http://www.nap.edu/books/0309048443/html/

306 See U.S. EPA 2009 Final PM ISA at Note 209.. 

307 The existing annual primary and secondary PM2.5 standards have been remanded and are being 

addressed in the currently ongoing PM NAAQS review.

308 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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(2) Plant and Ecosystem Effects of Ozone

Elevated ozone levels contribute to environmental effects, with impacts to plants 

and ecosystems being of most concern. Ozone can produce both acute and chronic injury

in sensitive species depending on the concentration level and the duration of the 

exposure. Ozone effects also tend to accumulate over the growing season of the plant, so 

that even low concentrations experienced for a longer duration have the potential to 

create chronic stress on vegetation. Ozone damage to plants includes visible injury to 

leaves and impaired photosynthesis, both of which can lead to reduced plant growth and 

reproduction, resulting in reduced crop yields, forestry production, and use of sensitive 

ornamentals in landscaping. In addition, the impairment of photosynthesis, the process 

by which the plant makes carbohydrates (its source of energy and food), can lead to a 

subsequent reduction in root growth and carbohydrate storage below ground, resulting in 

other, more subtle plant and ecosystems impacts. 

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 forest and other natural vegetation can potentially lead to 

species shifts and loss from the affected ecosystems, resulting in a loss or reduction in 

associated ecosystem goods and services. Lastly, 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. The final 2006 Ozone Air Quality Criteria Document presents more 

detailed information on ozone effects on vegetation and ecosystems.

(3) Atmospheric Deposition

Wet and dry deposition of ambient particulate matter delivers a complex mixture 

of metals (e.g., mercury, zinc, lead, nickel, aluminum, cadmium), organic compounds 

(e.g., POM, dioxins, furans) and inorganic compounds (e.g., nitrate, sulfate) to terrestrial 

and aquatic ecosystems. The chemical form of the compounds deposited depends on a 

variety of factors including ambient conditions (e.g., temperature, humidity, oxidant 

levels) and the sources of the material. Chemical and physical transformations of the 

compounds occur in the atmosphere as well as the media onto which they deposit. These 

transformations in turn influence the fate, bioavailability and potential toxicity of these 

compounds. Atmospheric deposition has been identified as a key component of the 

environmental and human health hazard posed by several pollutants including mercury, 

dioxin and PCBs.309

Adverse impacts on water quality can occur when atmospheric contaminants 

deposit to the water surface or when material deposited on the land enters a waterbody 

through runoff. Potential impacts of atmospheric deposition to waterbodies include those 

related to both nutrient and toxic inputs. Adverse effects to human health and welfare 

can occur from the addition of excess nitrogen via atmospheric deposition. The nitrogen-

 

309 U.S. EPA (2000) Deposition of Air Pollutants to the Great Waters: Third Report to Congress. Office of 

Air Quality Planning and Standards. EPA-453/R-00-0005. Docket EPA-HQ-OAR-2009-0472-0091.
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nutrient enrichment contributes to toxic algae blooms and zones of depleted oxygen, 

which can lead to fish kills, frequently in coastal waters. Deposition of heavy metals or 

other toxics may lead to the human ingestion of contaminated fish, impairment of 

drinking water, damage to the marine ecology, and limits to recreational uses. Several 

studies have been conducted in U.S. coastal waters and in the Great Lakes Region in 

which the role of ambient PM deposition and runoff is investigated.310,311,312,313,314 

Atmospheric deposition of nitrogen and sulfur contributes to acidification, 

altering biogeochemistry and affecting animal and plant life in terrestrial and aquatic 

ecosystems across the U.S. The sensitivity of terrestrial and aquatic ecosystems to 

acidification from nitrogen and sulfur deposition is predominantly governed by geology. 

Prolonged exposure to excess nitrogen and sulfur deposition in sensitive areas acidifies 

lakes, rivers and soils. Increased acidity in surface waters creates inhospitable conditions 

for biota and affects the abundance and nutritional value of preferred prey species, 

threatening biodiversity 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 include a 

decline in sensitive forest tree species, such as red spruce (Picea rubens) and sugar maple 

(Acer saccharum), and a loss of biodiversity of fishes, zooplankton, and macro

invertebrates.

In addition to the role nitrogen deposition plays in acidification, nitrogen 

deposition also leads to nutrient enrichment and altered biogeochemical cycling. In 

aquatic systems increased nitrogen can alter species assemblages and cause 

eutrophication. In terrestrial systems nitrogen 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 Section 7.1.2 of the draft RIA.

Adverse impacts on soil chemistry and plant life have been observed for areas 

heavily influenced by atmospheric deposition of nutrients, metals and acid species, 

resulting in species shifts, loss of biodiversity, forest decline and damage to forest 

 

310 U.S. EPA (2004) National Coastal Condition Report II. Office of Research and Development/ Office of 

Water. EPA-620/R-03/002. Docket EPA-HQ-OAR-2009-0472-0089.

311 Gao, Y., E.D. Nelson, M.P. Field, et al. 2002. Characterization of atmospheric trace elements on PM2.5 

particulate matter over the New York-New Jersey harbor estuary. Atmos. Environ. 36: 1077-1086. Docket 

EPA-HQ-OAR-2009-0472-11297.

312 Kim, G., N. Hussain, J.R. Scudlark, and T.M. Church. 2000. Factors influencing the atmospheric 

depositional fluxes of stable Pb, 210Pb, and 7Be into Chesapeake Bay. J. Atmos. Chem. 36: 65-79. 

Docket EPA-HQ-OAR-2009-0472-11299.

313 Lu, R., R.P. Turco, K. Stolzenbach, et al. 2003. Dry deposition of airborne trace metals on the Los 

Angeles Basin and adjacent coastal waters. J. Geophys. Res. 108(D2, 4074): AAC 11-1 to 11-24. Docket 

EPA-HQ-OAR-2009-0472-11296.

314 Marvin, C.H., M.N. Charlton, E.J. Reiner, et al. 2002. Surficial sediment contamination in Lakes Erie 

and Ontario: A comparative analysis. J. Great Lakes Res. 28(3): 437-450. Docket EPA-HQ-OAR-2009-

0472-11300.
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productivity. Potential impacts also include adverse effects to human health through 

ingestion of contaminated vegetation or livestock (as in the case for dioxin deposition), 

reduction in crop yield, and limited use of land due to contamination. 

Atmospheric deposition of pollutants can reduce the aesthetic appeal of buildings 

and culturally important articles through soiling, and can contribute directly (or in 

conjunction with other pollutants) to structural damage by means of corrosion or erosion. 

Atmospheric deposition may affect materials principally by promoting and accelerating 

the corrosion of metals, by degrading paints, and by deteriorating building materials such 

as concrete and limestone. Particles contribute to these effects because of their 

electrolytic, hygroscopic, and acidic properties, and their ability to adsorb corrosive gases 

(principally sulfur dioxide). 

(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. Volatile 

organic compounds (VOCs), some of which are considered air toxics, have long been 

suspected to play a role in vegetation damage.315 In laboratory experiments, a wide range 

of tolerance to VOCs has been observed.316 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.317

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 nitrogen 

oxides.318, 319, 320 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 

 

315 U.S. EPA. 1991. Effects of organic chemicals in the atmosphere on terrestrial plants. EPA/600/3-91/001. 

Docket EPA-HQ-OAR-2009-0472-0401.

316 Cape JN, ID Leith, J Binnie, J Content, M Donkin, M Skewes, DN Price AR Brown, AD Sharpe. 2003. 

Effects of VOCs on herbaceous plants in an open-top chamber experiment. Environ. Pollut. 124:341-343. 

Docket EPA-HQ-OAR-2009-0472-0357. 

317 Cape JN, ID Leith, J Binnie, J Content, M Donkin, M Skewes, DN Price AR Brown, AD Sharpe. 2003. 

Effects of VOCs on herbaceous plants in an open-top chamber experiment. Environ. Pollut. 124:341-343. 

Docket EPA-HQ-OAR-2009-0472-0357. 

318 Viskari E-L. 2000. Epicuticular wax of Norway spruce needles as indicator of traffic pollutant 

deposition. Water, Air, and Soil Pollut. 121:327-337. Docket EPA-HQ-OAR-2009-0472-1128.

319 Ugrekhelidze D, F Korte, G Kvesitadze. 1997. Uptake and transformation of benzene and toluene by 

plant leaves. Ecotox. Environ. Safety 37:24-29. Docket EPA-HQ-OAR-2009-0472-1142.

320 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. Docket 

EPA-HQ-OAR-2009-0472-0358.
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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.

D. Air Quality Impacts of Non-GHG Pollutants

(1) Current Levels of Non-GHG Pollutants

This proposal may have impacts on ambient concentrations of criteria and air 

toxic pollutants. Nationally, levels of PM2.5, ozone, NOX, SOX, CO and air toxics are 

declining.321 However, approximately 127 million people lived in counties that exceeded 

any NAAQS in 2008.322 These numbers do not include the people living in areas where 

there is a future risk of failing to maintain or attain the NAAQS. It is important to note 

that these numbers also do not account for the fact that EPA recently finished reviewing 

the ozone, and SO2 standards. Also, EPA is currently reviewing the standards for PM and 

CO, and those standards could be made more protective, which would increase the 

number of people living in nonattainment areas. 

Further, the majority of Americans continue to be exposed to ambient 

concentrations of air toxics at levels which have the potential to cause adverse health 

effects.323,324 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 U.S. EPA’s recent mobile source air toxics rule.325

(2) Impacts of Proposed Standards on Future Ambient Concentrations of 

PM2.5, Ozone and Air Toxics

Full-scale photochemical air quality modeling is necessary to accurately project 

levels of criteria pollutants and air toxics. For the final rules, a national-scale air quality

modeling analysis will be performed to analyze the impacts of the standards on PM2.5, 

ozone, and selected air toxics (i.e., benzene, formaldehyde, acetaldehyde, acrolein and 

1,3-butadiene). The length of time needed to prepare the necessary emissions 

inventories, in addition to the processing time associated with the modeling itself, has 

precluded us from performing air quality modeling for this proposal.

Sections VII.A and VII.B of the preamble present projections of the changes in 

criteria pollutant and air toxics emissions due to the proposed vehicle standards; the basis 

for those estimates is set out in Chapter 6 of the draft RIA. The atmospheric chemistry

related to ambient concentrations of PM2.5, ozone and air toxics is very complex, and 

 

321 U. S. EPA (2010) Our Nation’s Air: Status and Trends through 2008. Office of Air Quality Planning and 

Standards, Research Triangle Park, NC. Publication No. EPA 454/R-09-002. 

http://www.epa.gov/airtrends/2010/. 

322 See U. S. EPA Trends, Note 321. 

323 U. S. Environmental Protection Agency (2007). Control of Hazardous Air Pollutants from Mobile 

Sources; Final Rule. 72 FR 8434, February 26, 2007.

324 See U. S. EPA 2010. Light-Duty Final Rule, Note (#),.

325 See U. S. EPA 2007, Note 323.
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making predictions based solely on emissions changes is extremely difficult. However, 

based on the magnitude of the emissions changes predicted to result from the proposed 

standards, EPA expects that there will be a relatively small change in ambient air quality, 

pending a more comprehensive analysis for the final rules. 

For the final rules, EPA intends to use a 2005-based Community Multi-scale Air 

Quality (CMAQ) modeling platform as the tool for the air quality modeling. The CMAQ 

modeling system is a comprehensive three-dimensional grid-based Eulerian air quality

model designed to estimate the formation and fate of oxidant precursors, primary and 

secondary PM concentrations and deposition, and air toxics, over regional and urban 

spatial scales (e.g., over the contiguous U.S.).326,327,328 The CMAQ model is a wellknown and well-established tool and is commonly used by EPA for regulatory analyses, 

for instance the recent ozone NAAQS proposal, and by States in developing attainment 

demonstrations for their State Implementation Plans.329 The CMAQ model version 4.7

was most recently peer-reviewed in February of 2009 for the U.S. EPA.330 

CMAQ includes many science modules that simulate the emission, production, 

decay, deposition and transport of organic and inorganic gas-phase and particle-phase 

pollutants in the atmosphere. EPA intends to use the most recent version of CMAQ 

which reflects updates to version 4.7 to improve the underlying science. These include 

aqueous chemistry mass conservation improvements, improved vertical convective 

mixing and lowered CB05 mechanism unit yields for acrolein from 1,3-butadiene tracer 

reactions which were updated to be consistent with laboratory measurements. 

VIII. What are the Agencies' Estimated Cost, Economic, and 

Other Impacts of the Proposed Program?

In this section, we present the costs and impacts of the proposed HD National 

Program. It is important to note that NHTSA’s proposed fuel consumption standards and 

EPA’s proposed GHG standards would both be in effect, and each would lead to average 

 

326 U.S. Environmental Protection Agency, Byun, D.W., and Ching, J.K.S., Eds, 1999. Science algorithms 

of EPA Models-3 Community Multiscale Air Quality (CMAQ modeling system, EPA/600/R-99/030, 

Office of Research and Development). 

327 Byun, D.W., and Schere, K.L., 2006. Review of the Governing Equations, Computational Algorithms, 

and Other Components of the Models-3 Community Multiscale Air Quality (CMAQ) Modeling System, J. 

Applied Mechanics Reviews, 59 (2), 51-77.

328 Dennis, R.L., Byun, D.W., Novak, J.H., Galluppi, K.J., Coats, C.J., and Vouk, M.A., 1996. The next 

generation of integrated air quality modeling: EPA’s Models-3, Atmospheric Environment, 30, 1925-1938.

329 U.S. EPA (2007). Regulatory Impact Analysis of the Proposed Revisions to the National Ambient Air 

Quality Standards for Ground-Level Ozone. EPA document number 442/R-07-008, July 2007.

330 Report on the peer-review is still being finalized. Draft available upon request from Director S.T.Rao, 

Atmospheric Modeling and Analysis Division; rao.st@epa.gov; 919-541-4541. Allen, D., Burns, D., 

Chock, D., Kumar, N., Lamb, B., Moran, M. (February 2009 Draft Version). Report on the Peer Review of 

the Atmospheric Modeling and Analysis Division, NERL/ORD/EPA. U.S. EPA, Research Triangle Park, 

NC. 
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fuel economy increases and GHG emission reductions. The two agencies’ proposed 

standards would comprise the HD National Program.

The net benefits of the proposed HD National Program consist of the effects of 

the program on: 

 the vehicle program costs (costs of complying with the vehicle CO2 standards)

 fuel savings associated with reduced fuel usage resulting from the program

 the economic value of reductions in greenhouse gas emissions, 

 the reductions in other (non-GHG) pollutants, 

 costs associated with increases in noise, congestion, and accidents resulting from 

increased vehicle use, 

 the economic value of improvements in U.S. energy security impacts,

 benefits associated with increased vehicle use due to the “rebound” effect. 

We also present the cost-effectiveness of the standards, or the cost per ton of 

emissions reduced. A few effects of the program, such as the effects on other pollutants, 

are not included here. We plan to add the effects of other pollutants to the analysis for 

the final rule.

The program may have other effects that are not included here. The agencies seek 

comment on whether any costs or benefits are omitted from this analysis, so that they can 

be explicitly recognized in the Final Rule.

The total monetized benefits (excluding fuel savings) under the program are 

projected to be $1.5 to $8.0 billion in 2030, depending on the value used for the social 

cost of carbon. These benefits are summarized below in Table VIII-5. The costs of the 

program in 2030 are estimated to be approximately $2.0 billion for new engine and truck 

technology less $18.9 billion in savings realized by trucking operations through fewer 

fuel expenditures (calculated using pre-tax fuel prices). These costs are summarized 

below in Table VIII-4. The present value of the total monetized benefits (excluding fuel 

savings) under the program are expected to range from $23.7 billion to $152.9 billion 

with a 3% discount rate; with a 7% discount rate, the total monetized benefits are 

expected to range from $15.3 billion to $144.5 billion. These values, summarized in 

Table VIII-XX, depend on the value used for the social cost of carbon. The present value 

of costs of the program for new engine and truck technology, in Table VIII-XX, are 

expected to be $43.8 billion using a 3% discount rate, and $23.5 billion with a 7% 

discount rate, less fuel savings (calculated using pre-tax fuel prices) of $351.1 billion 

with a 3% discount rate, and $152.1 billion with a 7% discount rate. Total present net 

benefits (in Table VIII-XX) are thus expected to range from $331 billion to $460.2 

billion with a 3% discount rate, and $143.9 billion to $273.1 billion with a 7% discount 

rate.

The estimates developed here are measured against a baseline fuel economy 

associated with MY 2010 vehicles. The extent to which fuel economy improvements 

may have occurred in the absence of the rule affect the net benefits associated with the 

rule. If trucks would have ended up installing technologies to achieve the fuel savings 
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and reduced GHG emissions in the absence of this proposal, then both the costs and 

benefits of these fuel savings could be attributed to market forces, not the rule. At this 

time, the agencies do not have estimates of the extent of fuel-saving technologies that 

might have been adopted in the absence of this proposal. We seek comment on the 

degree to which the technologies discussed in this proposal would have been adopted in 

the absence of this proposal. 

EPA has undertaken an analysis of the economy-wide impacts of the GHG 

tailpipe standards as an exploratory exercise that EPA believes could provide additional 

insights into the potential impacts of the program. These economy-wide impacts do not 

represent additional benefits of the program over and above those already included in the 

analysis, and were not a factor that was considered in evaluating the stringency of the 

proposed standards. It is important to note that the results of this modeling exercise are 

dependent on the assumptions associated with how manufacturers will make fuel 

economy improvements and how trucking operations will respond to increases in higher 

vehicle costs and improved vehicle fuel economy as a result of the program. Section 

VIII.F discusses the underlying implications of these assumptions on economic impacts. 

Further information on these and other aspects of the economic impacts of our rule are 

summarized in the following sections and are presented in more detail in the RIA for this 

proposed rulemaking.

A. Conceptual Framework for Evaluating Impacts

This regulation is motivated primarily by the goals of reducing emissions of 

greenhouse gases and promoting energy security by reducing consumption of petroleumbased fuels. These are classic externalities, meaning that private markets do not 

incorporate the costs associated with these problems; these costs are not borne by the 

households or businesses whose actions are responsible for them. In the absence of some 

mechanism to “internalize” these costs – that is, to transfer their burden to individuals or 

firms whose decisions impose them – individuals will consume more petroleum-based 

fuels than is socially optimal. Externalities are a classic motivation for government 

intervention in markets. These externalities, as well as effects due to changes in 

emissions of other pollutants and other impacts, are discussed in Sections VIII.H – VIII.J. 

This proposal also identifies technologies that reduce truck operators’ fuel costs 

enough that they pay for themselves over short periods of time under the assumptions 

made for this analysis (e.g. AEO 2010 projected fuel prices). Standard economic theory

suggests that in normally-functioning competitive markets, interactions between vehicle 

buyers and producers would lead producers to incorporate all cost-effective technology

into the vehicles that they offer, without government intervention. Unlike in the lightduty vehicle market, the vast majority of vehicles in the medium- and heavy-duty truck 

market are purchased and operated by businesses, for most of whom fuel costs represent 

a substantial operating expense. 

Even in the presence of uncertainty and imperfect information – conditions that 

hold to some degree in every market – we generally expect firms to attempt to minimize 

their costs in an effort to survive in a competitive marketplace, and therefore to make 
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decisions that are in the best interest of the company and its owners and/or shareholders. 

In this case, the benefits of the rule would be due to external benefits. However, as 

discussed below in in Section VIII.E, the agencies have estimated that the application of 

fuel-saving technologies in response to the proposed standards would yield private 

returns of 140% to 420% (see Table VIII-21 below). The agencies have also estimated 

that the application of these technologies would be significantly lower in the absence of 

the proposed standards (i.e., under the “no action” regulatory alternative), meaning that 

truck buyers and operators ignore opportunities to make investments in higher fuel 

economy that appear to offer significant economic returns.

As the March 2010 NAS Report notes, buyers of new trucks appear to require 

very short payback periods, ranging from 18 months to 2 years for fuel-saving 

technologies.331 Such short payback periods imply that purchasers and operators of new 

trucks apply very high discount rates to future fuel savings. As Helfand and Wolverton 

note, however, the observation that truck buyers may discount future returns heavily does 

not by itself explain why they demand such short payback periods.332 

This discussion examines some reasons that may explain why the market for fuel 

economy may not operate as efficiently as theory would suggest. These include 

imperfect information in the original and resale markets, split incentives, uncertainty 

about future fuel prices, and adjustment and transactions costs. As the discussion will 

indicate, some of these explanations suggest failures in the private market for fuel-saving 

technology in addition to the external failures that are the motivation for the rule. Other 

explanations suggest market-based behaviors that may imply additional costs not 

accounted for in this analysis. The agencies invite comment on these explanations, and 

any information to support corresponding estimates of their importance. The agencies 

also request comment and information regarding any other factors that could explain the 

appearance of cost-effective fuel-saving technologies that have not been incorporated into 

trucks.

(1) Information Issues in the Original Sale Markets

First, there appears to be poor information available about the effectiveness of 

many fuel-saving technologies for new vehicles. As the NAS report notes, “Reliable, 

peer-reviewed data on fuel saving performance is available only for a few technologies in 

a few applications.” If reliable information on the effectiveness of new technologies is 

absent, truck buyers will understandably be reluctant to spend additional money to 

purchase vehicles equipped with unproven technologies. However, information about the 

effectiveness of selected technologies does exist, and some appear to be very costeffective. The SmartWay Transport Partnership has been effective in getting the word 

out to its partners about these technologies, and, as a consequence, many SmartWay

 

331 See NAS 2010, Note (#), at pp. S-12, 8-16.

332 Helfand, Gloria, and Ann Wolverton. “Evaluating the Consumer Response to Fuel Economy: A 

Review of the Literature.” U.S. Environmental Protection Agency: National Center for Environmental 

Economics Working Paper #09-04, August 2009.
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Partners have adopted these new technologies. Nevertheless, adoption of newer 

technologies throughout the trucking industry still lags their widespread availability.

There are several possible explanations for the slow adoption of apparently costeffective technologies. It may be difficult for truck drivers and fleet operators to separate 

the individual effects of various technologies and operating strategies from one another,

particularly when they tend to be used in conjunction. It may also be difficult for truck 

operators to assess the applicability of even objective and reliable test results to their own 

specific vehicle configurations and operating practices; at the same time, the effects of 

specific technologies or operating practices may vary with geography, season of the year, 

or other factors. If so, then cost-effective technological improvements may not be 

adopted because they cannot be distinguished from inefficient technologies. 

Information provision, such as the efforts of the SmartWay program, can address 

the problem of the reliability of results, as long as truck purchasers are willing to act on 

the information. As noted, though, technological diffusion may be a gradual process 

even when information is widely available.

The requirement for the use of new technologies included in this proposal will 

speed their adoption and thus provide more readily available information about their 

benefits. To the extent that the benefits of these new technologies are well documented, 

they are provided to trucks more quickly and more consistently than in the absence of 

regulation, although the diversity of truck uses, driving situations, and driver behavior 

may still lead to variation in the fuel savings that individual trucks or fleets experience. 

(2) Information Issues in the Resale Market

In addition to issues in the new vehicle market, the resale market does not appear 

to reward the addition of fuel-saving technology to vehicles adequately to ensure their 

original purchase by new truck buyers. This lack of payback for users beyond the 

original owner almost certainly contributes to the short payback period that new 

purchasers expect.

Some of this unwillingness to pay for fuel-saving technology may be due to the 

extension of the information problems in the new vehicle market into resale markets. 

Buyers in the resale market have no more reason to trust information on fuel-saving 

technologies than buyers in the original market. Because actual fuel economy of trucks 

on the road depends on many factors, including geography and driving styles or habits, 

logs of truck performance for used vehicles may not provide reliable information about 

the fuel economy that purchasers of used trucks will experience.

A related possibility is that vehicles will be used for different purposes by their 

second owners than those for which they were originally designed. For instance, a 

vehicle originally purchased for long hauls might be used instead for regional or 

intrastate trips, in which case some of the fuel-saving measures that proved effective in 

its original use may not be equally effective in the new uses. If information were more 

widely available and reliable, then purchasers in the resale market would seek vehicles 
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with technologies that best suited their purposes, and buyers would be matched with 

sellers so that used vehicles would be used in purposes for which their fuel-saving 

technologies were most valuable. The fuel savings recovered in the secondary market 

may not match those in the original market if the optimal new use of the vehicle does not 

earn as many benefits from the technologies. In that case, the premium for fuel-saving 

technology in the secondary market should accurately reflect the value in that market, 

even if it is lower than its value in the original market, and the market has not failed. 

Because the information necessary to optimize use in the secondary market may not be 

readily available or reliable, however, buyers in the resale market may have less ability 

than purchasers of new vehicles to identify and gain the advantages of new fuel-saving 

technologies, and thus even less likely to pay a premium for them.

For these reasons, technology diffusion is likely to be even slower in the resale 

market than in the original market. Even when fuel-saving technologies will provide 

benefits in the resale markets, purchasers of used vehicles may not be willing to pay for 

them. As a result, the purchasers of original equipment cannot expect the resale market 

to provide appropriate compensation for the new technologies, even when those 

technologies would reduce costs for the new buyers. This market failure is likely to 

contribute to the very short payback period required for new technologies in the new 

vehicle market.

(3) Split incentives in the medium- and heavy-duty truck industry

When markets work effectively, signals provided by transactions in one market 

are quickly transmitted to related markets and influence the decisions of buyers and 

sellers in those related markets. For instance, in a well-functioning market system, 

changes in the expected future price of fuel should be transmitted rapidly to those who 

purchase trucks, who will then re-evaluate the amount of fuel-saving technology to 

purchase for new vehicles. In the heavy-duty vehicle market, however, it appears that the 

transmission of new information and resulting changes in buyers’ and sellers’ incentives 

is often neither smooth nor complete. If they endure for prolonged periods, such “split 

incentives” may contribute to inefficiencies in the market for fuel economy. 

One place where such a split may occur is between the owners and operators of 

trucks. Because they are generally responsible for purchasing fuel, truck operators have 

strong incentives to economize on its use,and are thus likely to support the use of fuelsaving technology. However, the owners of trucks or trailers are often different from 

their operators, and, when purchasing vehicles, may be more concerned about their 

longevity or maintenance costs than about their fuel efficiency. As a result, capital 

investments by truck owners may be channeled into equipment that improves vehicles’ 

durability or reduces their maintenance costs, rather than into fuel-saving technology. If 

operators can choose freely among the trucks they drive, competition among truck 

owners to employ operators would encourage owners to invest in fuel-saving technology. 

However, if truck owners have more ability to choose among operators, then market 

signals for improved fuel savings that are transmitted to truck owners may be muted.
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Anecdotal information about large truck fleets suggests that, even within a 

company, the office or department responsible for truck purchases is often different from 

that responsible for purchasing fuel. Therefore, the employees who purchase trucks may

have strong incentives to lower their initial capital cost, but not equally strong incentives 

to lower operating costs. 

Single-wide tires, which save fuel and allow more payload (increasing revenue), 

offer another example of split incentives. They require a different driving style; those 

concerned about retaining drivers may resist their purchase, because drivers may not like 

the slightly different "feel" of wheel torque needed. Maintenance and repair staff may

resist them because the tires may not be as available as they would like on the road, or 

they may need to change road service providers. Finally, those who resell the trucks may

believe that the resale market will not value the tires. While financial pressures should 

strong provide incentives for greater coordination, especially when fuel costs are a large 

share of operating costs, it can be difficult institutionally to change budgeting procedures 

and to coordinate across offices. Thus, even within a company incentives for fuel savings 

may not be fully transmitted.

In addition, the NAS report notes that split incentives can arise between tractor 

and trailer operators.333 Trailers affect the fuel efficiency of shipping, but trailer owners 

do not face strong incentives to coordinate with truck owners. Although some trucking 

fleets own or lease their own trailers, a significant part of the trucking business is “drop 

and hook” service, in which trucking fleets pick up and drop off trailers and containers. 

These trailers and containers can belong to shippers, other trucking companies, leasing 

companies, or ocean-going vessel lines, in which cases their owners may not face strong 

incentives to economize on fuel consumption by tractor operators. Though tractor 

operators should, in principle, have some ability to arrange tractor-trailer combinations 

that provide increased fuel efficiency, the value of the resulting fuel savings may be small 

relative to the complexity and cost involved. EPA and NHTSA are not proposing to 

regulate trailers in this proposal.

By itself, information provision may be inadequate to address the potential 

underinvestment in fuel economy resulting from such split incentives, especially in the 

near term. In this setting, regulation may contribute to fuel savings that otherwise may be 

difficult to achieve.

(4) Uncertainty about Future Cost Savings

Another factor contributing to slow adoption of fuel saving technologies may be 

uncertainty about future fuel prices or truck maintenance costs. When purchasers have 

less than perfect foresight about future operating expenses, they may implicitly discount 

future savings in those costs due to uncertainty about potential returns from investments 

that reduce future costs, while the immediate costs of the fuel-saving or maintenancereducing technologies are certain and immediate, and thus not subject to discounting. In 

 

333 See NAS 2010, Note (#), at p. 8-8.
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this situation, both the expected return on capital investments in higher fuel economy and 

potential variance about its expected rate are likely to play a role in a firm’s calculation of 

its payback period on such investments.

In the context of energy efficiency investments for the home, Metcalf and 

Rosenthal (1995) and Metcalf and Hassett (1995) point out that households weigh 

known, up-front costs that are essentially irreversible against an unknown stream of 

future fuel savings.334 Uncertainty about the value of future energy savings may make 

risk-averse households reluctant to invest in energy-saving technologies that appear to 

offer attractive economic returns. These authors find that it is possible to replicate the 

observed adoption rates for energy efficiency improvements by incorporating the effect 

of uncertainty about the value of future energy savings into an empirical model. 

Greene et al (2009) also find support for this explanation in the context of lightduty fuel economy decisions: a loss-averse consumer's expected net present value of 

increasing the fuel economy of a passenger car can be very close to zero, even if a riskneutral expected value calculation shows that its buyer can expect significant net benefits 

from purchasing a more fuel-efficient car.

335 These authors find is worth noting that they

find that uncertainty regarding the future price of gasoline is a less important source of 

this result than is uncertainty about the lifetime and reliability of the vehicle. Supporting 

this hypothesis is a finding by Dasgupta et. al (2007) that consumers are more likely to 

lease than buy a vehicle with higher maintenance costs because it provides them with the 

option to return it before those costs become too high.336 However, the agencies know of 

no studies that have estimated the impact of uncertainty on perceived future savings for 

medium and heavy-duty vehicles. 

Purchasers' uncertainty about future fuel prices implies that mandating 

improvements in fuel efficiency can reduce the expected utility associated with truck 

purchases. This is because adopting such regulation requires purchasers to assume a 

greater level of risk than they would in its absence, even if the future fuel savings 

predicted by a risk-neutral calculation actually materialize. Thus the mere existence of 

uncertainty about future savings in fuel costs does not by itself assure that regulations 

requiring improved fuel efficiency will necessarily provide economic benefits for truck 

purchasers and operators. On the other hand, risk aversion reduces expected returns for 

 

334 Metcalf, G., and D. Rosenthal (1995). “The ‘New’ View of Investment Decisions and Public Policy 

Analysis: An Application to Green Lights and Cold Refrigerators,” Journal of Policy Analysis and 

Management 14: 517–531. Metcalf and Hassett (1995). “Energy Tax Credits and Residential Conservation 

Investment: Evidence from Panel Data (with Kevin Hassett)” Journal of Public Economics 57 (1995): 201-

217. Metcalf, G., and K. Hassett (1999). “Measuring the Energy Savings from Home Improvement 

Investments: Evidence from Monthly Billing Data.” The Review of Economics and Statistics 81(3): 516-

528.

335 Greene, D., J. German, and M. Delucchi (2009). “Fuel Economy: The Case for Market Failure” in 

Reducing Climate Impacts in the Transportation Sector, Sperling, D., and J. Cannon, eds. Springer Science.

336 Dasgupta, S., S. Siddarth, and J. Silva-Risso (2007). “To Lease or to Buy? A Structural Model of a 

Consumer’s Vehicle and Contract Choice Decisions.” Journal of Marketing Research 44: 490 – 502.
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businesses; competitive pressures can reduce risk aversion, because risk-neutral 

companies can make higher average profits over time. 

(5) Adjustment and Transactions Costs

Another possibility is that transactions costs of changing to new technologies 

(how easily drivers will adapt to the changes, e.g.) may slow their adoption. Because of 

the diversity in the trucking industry, truck owners and fleets may like to see how a new 

technology works in the field, when applied to their specific operations, before they adopt 

it. If a conservative approach to new technologies leads truck buyers to adopt new 

technologies slowly, then successful new technologies are likely to be adopted over time 

without market intervention, but with delays in achieving fuel saving, environmental, and 

energy security benefits. 

In addition, there may be costs associated with training drivers to realize the 

potential fuel savings enabled by new technologies, or with accelerating fleet operators’ 

scheduled fleet turnover and replacement to hasten their acquisition of vehicles equipped 

with new fuel-saving technologies. Here, again, there may be no market failure; instead, 

requiring the widespread use of these technologies may impose adjustment and 

transactions costs not included in this analysis. As in the discussion of the role of risk, 

these costs are typically immediate and undiscounted, while their benefits are future and 

uncertain; risk or loss aversion may further discourage companies from adopting new 

technologies.

To the extent that there may be transactions costs associated with the new 

technologies, then regulation gives all new truck purchasers a level playing field: they

will all adjust on approximately the same time frame. If experience with the new 

technologies serves to reduce uncertainty and risk, industry as a whole may become more 

accepting of new technologies. This could increase demand for future new technologies 

and induce additional benefits in the legacy fleet through complementary efforts like 

SmartWay.

(6) Summary

On the one hand, commercial vehicles are under competitive pressure to reduce 

operating costs, and thus their purchasers and operators can be expected to pursue costeffective fuel-saving technologies. On the other hand, the short payback period required 

by buyers of new trucks is a symptom that may suggest some combination of uncertainty

about future cost savings, transactions costs, and imperfectly functioning markets. 

Asymmetric or missing information can contribute to market failures, as Akerlof (1970) 

has argued.337 The market for medium- and heavy-duty trucks may face this problem, 

both in the new vehicle market and in the resale market. In addition, widespread use of 

 

337 Akerlof, George A. “The Market for ‘Lemons’: Quality Uncertainty and the Market Mechanism,” 

Quarterly Journal of Economics 84(3) (1970): 488-500.
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tractor-trailer combinations introduces the possibility that owners of trailers may have 

weaker incentives than truck owners or operators to adopt fuel-saving technology.

Provision of information about fuel-saving technologies will assist in the adoption 

of new cost-saving technologies, but diffusion of new technologies can be a slow process. 

Those who are willing to experiment with new technologies expect to find cost savings, 

but those may be difficult to prove. As noted above, because individual results of new 

technologies vary, new truck purchasers may find it difficult to identify or verify the 

effects of fuel-saving technologies. Those who are risk-averse are likely to avoid new 

technologies out of concerns over the possibility of spending money for no return, or with 

other adverse impacts. As the SmartWay program demonstrates, competitive pressures in 

the freight transport industry can provide a strong incentive to reduce fuel consumption 

and improve environmental performance. However, not every driver or trucking fleet 

operating today has the requisite ability or interest to access the technical information 

provided by SmartWay, nor the resources necessary to evaluate this information within 

the context of his or her own freight operation.

Regulation in this context will obviously speed adoption of technologies. The 

faster adoption will increase potential buyers’ understanding of the value of new 

technologies. To the extent that different technologies are used, greater information will 

be gained on the relative effects of those technologies. This mechanism should reduce 

the information problem, by easing both identification and adoption of new technologies. 

Regulation will also complement existing efforts like SmartWay by providing additional

and widespread demonstration of the benefits of new technologies. This will reinforce 

among truck operators of legacy fleet vehicles a desire to adopt similar new fuel-saving 

technologies through the SmartWay program.

B. Costs Associated with the proposed program

In this section, EPA presents our estimate of the costs associated with the 

proposed program. The presentation here summarizes the costs associated with new 

technology expected to be added to meet the new GHG and fuel consumption standards. 

The analysis summarized here provides our estimate of incremental costs on a per truck 

basis and on an annual total basis. 

The presentation here summarizes the best estimate by EPA and NHTSA staff as 

to the technology mix expected to be employed for compliance. For details behind the 

cost estimates associated with individual technologies, the reader is directed to Section III 

of this preamble and to Chapter 2 of the draft RIA. 

With respect to the cost estimates presented here, the agencies note that, because 

these estimates relate to technologies which are in most cases already available, these 

cost estimates are technically robust. 
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(1) Costs per Truck

For the class 2b and 3 trucks, the agencies have used a methodology consistent 

with that used for our recent light-duty joint rulemaking since most of the technologies 

expected for class 2b and 3 trucks is consistent with that expected for the larger light-duty

trucks. The cost estimates presented in the recent light-duty joint rulemaking were then 

scaled upward to account for the larger weight, towing capacity, and work demands of 

the trucks in these heavier classes. For details on that scaling process and the resultant 

costs for individual technologies, the reader is directed to Section III of this preamble and

to Chapter 2 of the draft RIA. Note also that all cost estimates have been updated to 2008 

dollars for this analysis while the recent light-duty joint rulemaking was presented in 

2007 dollars. 

For the heavy-duty gasoline and the light heavy-duty diesel engines, we have used 

engine-related costs from the class 2b and 3 truck estimates since the light heavy-duty 

engines are essentially the same engines as those sold into the class 2b and 3 truck 

market. 

For medium and heavy heavy-duty engines, the agencies have estimated costs 

using a different methodology than that employed in the recent light-duty joint 

rulemaking. In the recent light-duty joint rulemaking, the fixed costs were included in 

the hardware costs via an indirect cost multiplier. As such, the hardware costs presented 

in that analysis, and in the cost estimates for class 2b and 3 trucks and the light HD diesel 

and HD gasoline engines, included both the actual hardware and the associated fixed 

costs. For this analysis, some of the fixed costs are estimated separately for medium and 

heavy HD engines and are presented separately from the hardware costs. For details, the 

reader is directed to Chapter 2 of the draft RIA. Importantly, once totaled both 

methodologies account for all the costs associated with the proposal. As noted above, all 

costs are presented in 2008 dollars.

The estimates of vehicle compliance costs cover the years leading up to – 2012 

and 2013 – and including implementation of the program – 2014 through 2018. Also 

presented are costs for the years following implementation to shed light on the long term 

(2022 and later) cost impacts of the program. The year 2022 was chosen here consistent 

with the recent light-duty joint rulemaking. That year was considered long term in that 

analysis because the short-term and long-term markup factors described shortly below are 

applied in five year increments with the 2012 through 2016 implementation span and the 

2017 through 2021 span both representing the short-term. Since many of the costs used 

in this analysis are based on costs in the recent light-duty joint rulemaking analysis, 

consistency with that analysis seems appropriate. That said, comments are requested as 

to whether 2024 would be a more appropriate long term year. 

Some of the individual technology cost estimates are presented in brief in Section 

III, and account for both the direct and indirect costs incurred in the automobile 

manufacturing and dealer industries (for a complete presentation of technology costs, 

please refer to Chapter 2 of the draft RIA). To account for the indirect costs on class 2b 

and 3 trucks and on light heavy-duty engines, the agencies have applied an indirect cost 
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markup (ICM) factor to all of the direct costs to arrive at the estimated technology cost. 

The ICM factor used was 1.17 in the short-term (2014 through 2021) to account for 

differences in the levels of R&D, tooling, and other indirect costs that will be incurred. 

Once the program has been fully implemented, some of the indirect costs will no longer 

be attributable to these standards and, as such, a lower ICM factor is applied to direct 

costs in 2022 and later. The agencies have also applied ICM factors to class 4 through 8 

truck and both medium and heavy heavy-duty engine technologies. Mark up factors in 

these categories range from 1.11 to 1.26 in the short term (2014 through 2021) depending 

on the complexity of the given technology. Note that, for the medium and heavy HD 

engines, the agencies have applied these mark ups to ensure that our estimates are 

conservative since we have estimated fixed costs separately for technologies applied to 

these categories effectively making the use of markups a double counting of indirect 

costs. The agencies request comment on this fact. The agencies also request comment 

on the ICMs being used in this analysis -- the levels associated with R&D, warranty, etc. 

-- and whether those are appropriate or should be revised. If commenters suggest 

revisions, the agencies request supporting arguments and/or documentation. For the 

details on the ICMs, please refer to the report that has been placed in the docket for this 

proposal.338

The agencies have also considered the impacts of manufacturer learning on the 

technology cost estimates. Consistent with recent light-duty joint rulemaking, some costs 

are estimated to decline by 20 percent with each of the first two doublings of production 

beginning with the first year of implementation. These volume-based cost declines, 

termed “volume” based learning, take place after manufacturers have had the opportunity

to find ways to improve upon their manufacturing processes or otherwise manufacture 

these technologies in a more efficient way. After two 20 percent cost reduction steps, the 

cost reduction learning curve flattens out considerably as only minor improvements in 

manufacturing techniques and efficiencies remain to be had. By then, costs decline 

roughly three percent per year as manufacturers and suppliers continually strive to reduce 

costs. These time-based cost declines, termed “time” based learning, take place at a rate 

of three percent per year. Learning impacts have been considered on most but not all of 

the technologies expected to be used because some of the expected technologies are 

already used rather widely in the industry and, presumably, learning impacts have already

occurred. The agencies have considered volume-based learning for only a handful of 

technologies considered to be new or emerging technologies such as energy recovery

systems and thermal storage units which might one day be used on big trucks. For most 

technologies, EPA has considered them to be more established and, hence, the agencies 

have applied the lower time based learning. For more discussion of the learning 

approach and the technologies to which each type of learning has been applied the reader 

is directed to Chapter 2 of the draft RIA.

The technology cost estimates discussed in Section III and detailed in Chapter 2 

of the draft RIA are used to build up technology package cost estimates. For each engine 

 

338 Insert reference to Chi Li's updated ICM report.
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and truck class, a single package for each was developed capable of complying with the 

proposed standards and the costs for each package was generated. The technology

packages and package costs are discussed in more detail in Chapter 2 of the draft RIA. 

The compliance cost estimates take into account all credits and trading programs and

include costs associated with air conditioning controls. Table VIII-1 presents the average 

incremental costs per truck for this proposal. For Class 2b and 3, costs increase as the 

standards become more stringent in 2014 through 2018. Following 2018, costss then 

decrease going forward as learning effects result in decreased costs for individual 

technologies. By 2022, the long term ICMs take effect and costs decrease yet again. For 

vocational trucks, cost trends are more difficult to discern as diesel engines begin adding 

technology in 2014, gasoline engines begin adding technology in 2016, and the trucks 

themselves begin adding technology in 2014. With learning effects the costs, in general, 

decrease each year except for the heavy-duty gasoline engine changes in 2016. Long 

term ICMs take effect in 2022 to provide more cost reductions. For combination tractors, 

costs generally decrease each year due to learning effects with the exception of 2017 

when the engines placed in sleeper cab tractors add turbo compounding. Following that, 

learning impacts result in cost reductions and the long term ICMs take effect in 2022 for 

further cost reductions. By 2030 and later, cost per truck estimates remain constant for 

all classes. Regarding the long term ICMs taking effect in 2022, the agencies consider 

this the point at which some indirect costs decrease or are no longer considered 

attributable to the program (e.g., warranty costs go down). Costs per truck remain 

essentially constant thereafter. 

Table VIII-1: Estimated Cost per Truck (2008 dollars)

Class 2b&3 Vocational Combination

2014 $233 $362 $6,828

2015 $302 $356 $6,638

2016 $587 $389 $6,358

2017 $877 $382 $6,668

2018 $1,458 $349 $6,403

2020 $1,454 $333 $6,144

2030 $1,375 $272 $5,081

2040 $1,375 $267 $5,081

2050 $1,375 $267 $5,081

As noted above, the fixed costs were estimated separately from the hardware costs 

for the medium and heavy HD engines that are placed in Vocational and Combination 

trucks. Those fixed costs are not included in Table VIII-1. The agencies have estimated 

the R&D costs at $6.75 million per manufacturer per year for five years and the new test 

cell costs (to accommodate measurement of N2O emissions) at $100,000 per 

manufacturer. These costs apply individually for medium and heavy HD engines. Given 

the 11 manufacturers impacted by the proposed standards, each of which are estimated to 

sell both medium and heavy HD engines, we have estimated a five year annual R&D cost 

of $148.5 million dollars (2 x 11 x $6.75 million for each year 2012-2016) and a one time 

test cell cost of $1.1 million dollars (2 x 11 x $100,000 in 2013). Estimating annual sales 

of medium and heavy HD engines at roughly 280,000 units results in roughly $530 per 
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engine per year for five years beginning in 2012 and ending in 2016. Again, these costs 

are not reflected in Table VIII-1, but are included in Table VIII-2 as “Other Engineering 

Costs.” 

(2) Annual Costs of the Proposal

The costs presented here represent the incremental costs for newly added 

technology to comply with the proposal. Together with the projected increases in truck 

sales, the increases in per-truck average costs shown in Table VIII-1above result in the 

total annual costs presented in Table VIII-2 below. Note that the costs presented in Table 

VIII-2 do not include the savings that would occur as a result of the improvements to fuel 

consumption. Those impacts are presented in Section VIII. E. . Note also that the costs 

presented here represent costs estimated to occur presuming that EPA’s proposed 

standards will continue in perpetuity. Any future changes to the proposed standards 

would be considered at the time they are proposed and/or made final. In other words, 

EPA’s proposed standards do not apply only to 2014-2018 model year trucks - they do, in 

fact, apply to all 2014 and later model year trucks. We present more detail regarding the 

2014-2018 model year trucks in Section VIII.K where we summarize all monetized costs 

and benefits.

Table VIII-2: Annual Costs Associated with the Proposal ($Millions of 2008 dollars)

Year Class 2b&3 Vocational Combination Other

Engineering

Costs

Annual

Costs

2012 $0 $0 $0 $149 $149

2013 $0 $0 $0 $151 $151

2014 $183 $202 $834 $149 $1,367

2015 $221 $205 $825 $149 $1,399

2016 $418 $231 $804 $149 $1,602

2017 $622 $234 $859 $0 $1,714

2018 $1,045 $220 $843 $0 $2,108

2020 $1,004 $222 $844 $0 $2,070

2030 $980 $234 $805 $0 $2,019

2040 $1,057 $322 $921 $0 $2,300

2050 $1,140 $423 $1,065 $0 $2,627

NPV, 3% $19,240 $5,561 $18,261 $692 $43,755

NPV, 7% $9,923 $2,891 $10,009 $632 $23,456

C. Indirect Cost Multipliers

(1) Markup Factors to Estimate Indirect Costs

For most of the segments in this analysis, the indirect costs are estimated by 

applying indirect cost multipliers (ICM) to direct cost estimates. ICMs were calculated 

by EPA as a basis for estimating the impact on indirect costs of individual vehicle 

technology changes that would result from regulatory actions. Separate ICMs were 

derived for low, medium, and high complexity technologies, thus enabling estimates of 
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indirect costs that reflect the variation in research, overhead, and other indirect costs that 

can occur among different technologies. ICMs were also applied in the MY 2012-2016 

CAFE rulemaking. 

Previous CAFE rulemakings applied a retail price equivalent (RPE) factor to 

estimate indirect costs and mark up direct costs to the retail level. Retail Price 

Equivalents are estimated by dividing the total revenue of a manufacturer by the direct 

manufacturing costs. As such, it includes all forms of indirect costs for a manufacturer 

and assumes that the ratio applies equivalently for all technologies. ICMs are based on 

RPE estimates that are then modified to reflect only those elements of indirect costs that 

would be expected to change in response to a technology change. For example, warranty

costs would be reflected in both RPE and ICM estimates, while marketing costs might 

only be reflected in an RPE estimate but not an ICM estimate for a particular technology, 

if the new technology is not one expected to be marketed to consumers. Because ICMs 

calculated by EPA are for individual technologies, many of which are small in scale, they

often reflect a subset of RPE costs; as a result, the RPE is typically higher than an ICM. 

This is not always the case, as ICM estimates for complex technologies may reflect 

higher than average indirect costs, with the resulting ICM larger than the averaged RPE 

for the industry. 

Precise association of ICM elements with individual technologies based on the 

varied accounting categories in company annual reports is not possible. Hence, there is a 

degree of uncertainty in the ICM estimates. If all indirect costs moved in proportion to 

changes in direct costs the ICM and RPE would be the same. Because most individual 

technologies are smaller scale than many of the activities of auto companies (such as 

designing and developing entirely new vehicles), it would be expected that the RPE 

estimate would reflect an upper bound on the average ICM estimate. The agencies are 

continuing to study ICMs and the most appropriate way to apply them, and it is possible 

revised ICM values may be used in our final rulemaking. With this in mind, the agencies 

are presenting a sensitivity analysis reflecting costs measured using the RPE in place of 

the ICM and indirect costs estimated independently in our primary analysis to examine 

the potential impact of these two approaches on estimated costs. 

(2) Background

While this analysis relies on ICMs to estimate indirect costs, an alternative 

method of estimating indirect costs is the retail price equivalent factor (RPE). The RPE 

has been used by NHTSA, EPA and other agencies to account for cost factors not 

included in available direct cost estimates, which are derived from cost teardown studies 

or sometimes provided by manufacturers. The RPE is the basis for these markups in all 

DOT safety regulations and in most previous fuel economy rules. The RPE includes all 

variable and fixed elements of overhead costs, as well as selling costs such as vehicle 

delivery expenses, manufacturer profit, and full dealer markup, and assumes that the ratio 

of indirect costs to direct costs is constant for all vehicle changes. Historically, NHTSA 

has estimated that the RPE has averaged about 1.5 for the light-duty motor vehicle 

industry. The implication of an RPE of 1.5 is that each added $1.00 of variable cost in 
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materials, labor, and other direct manufacturing costs results in an increase in consumer 

prices of $1.50 for any change in vehicles. 

NHTSA has estimated the RPE from light-duty vehicle manufacturers’ financial 

statements over nearly 3 decades, and although its estimated value has varied somewhat 

year-to-year, it has generally hovered around a level of 1.5 throughout most of this 

period. The NAS report as well as a study by RTI International found that other 

estimates of the RPE varied from 1.26 to over 2.339 In a recent report, The National 

Academy of Sciences (NAS) acknowledged that an ICM approach was preferable but 

recommended continued use of the RPE over ICMs until such time as empirical data 

derived from rigorous estimation methods is available. The NAS report recommended 

using an RPE of 1.5 for outsourced (supplier manufactured) and 2.0 for in-house (OEM 

manufactured) technologies and an RPE of 1.33 for advanced hybrid and electric vehicle 

technologies. 

ICMs typically are significantly lower than RPEs, because they measure changes 

in only those elements of overhead and selling-related costs that are directly influenced 

by specific technology changes to vehicles. For example, the number of managers might 

not be directly proportional to the value of direct costs contained in a vehicle, so that if a 

regulation increases the direct costs of manufacturing vehicles, there might be little or no 

change in the number of managers. ICMs would thus assume little or no change in that 

portion of indirect costs associated with the number of managers – these costs would be 

allocated only to the existing base vehicle. By contrast, the RPE reflects the historical 

overall relationship between the direct costs to manufacture vehicles and the prices 

charged for vehicles, which must compensate manufacturers for both their direct and 

indirect costs for producing and selling vehicles. The assumption behind the RPE is that 

changes in the long-term price of the final product that accompany increases in direct 

costs of vehicle manufacturing will continue to reflect this historical relationship. 

Another difference between the RPE and ICM is that ICMs have been derived 

separately for different categories of technologies. A relatively simple technology 

change, such as switching to a different tire with lower rolling resistance characteristics, 

would not influence indirect costs in the same proportion as a more complex change, 

such as development of a full hybrid design. ICMs were developed for 3 broad 

categories of technology complexities, and are applied separately to fuel economy

technologies judged to fit into each of these categories. This requires determining which 

of these complexity categories each technology should be assigned. 

There is some level of uncertainty surrounding both the ICM and RPE markup 

factors. The ICM estimates used in this proposal group all technologies into three broad 

categories and treat them as if individual technologies within each of the three categories 

(low, medium, and high complexity) would have the same ratio of indirect costs to direct 

 

339 Rogozhin, Alex, Michael Gallaher, and Walter McManus. “Automobile Industry Retail Price 

Equivalent and Indirect Cost Multipliers.” Report prepared for EPA by RTI International. EPA Report 

EPA-420-R-09-003, February 2009.
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costs. This simplification means it is likely that the direct cost for some technologies 

within a category will be higher and some lower than the estimate for the category in 

general. More importantly, the ICM estimtes have not been validated through a direct 

accounting of actual indirect costs for individual technologies. Rather, the ICM estimates 

were developed using adjustment factors developed in two separate occasions: the first, a 

consensus process, was reported in the RTI report; the second, a modified Delphi method, 

was conducted separately and reported in an EPA memo.340 Both these panels were 

composed of EPA staff members with previous background in the automobile industry; 

the memberships of the two panels overlapped but were not the same.341 The panels 

evaluated each element of the industry’s RPE estimates and estimated the degree to 

which those elements would be expected to change in proportion to changes in direct 

manufacturing costs. The method and estimates in the RTI report were peer reviewed by

three industry experts and subsequently by reviewers for the International Journal of 

Production Economics.342 RPEs themselves are inherently difficult to estimate because 

the accounting statements of manufacturers do not neatly categorize all cost elements as 

either direct or indirect costs. Hence, each researcher developing an RPE estimate must 

apply a certain amount of judgment to the allocation of the costs. Moreover, RPEs for 

heavy and medium duty trucks and for engine manufacturers are not as well studied as 

they are for the light-duty automobile industry. Since empirical estimates of ICMs are 

ultimately derived from the same data used to measure RPEs, this affects both measures. 

However, the value of RPE has not been measured for specific technologies, or for 

groups of specific technologies. Thus applying a single average RPE to any given 

technology by definition overstates costs for very simple technologies, or understates 

them for advanced technologies. 

To highlight the potential differences between the use of ICMs and RPEs to 

estimate indirect costs, the agencies conducted an analysis based on the use of average 

RPEs for each industry in the place of the ICM and direct fixed cost estimates used in our 

proposal. Since most technologies involved in this proposal are low complexity level 

technologies, the estimate based on the use of an average RPE likely overstates the costs.

The weighted average RPEs for the truck and engine industries are 1.36 and 1.28 

respectively. These values were substituted for the ICMs and directly estimate indirect 

costs used in the primary cost analysis referenced elsewhere in this document. Using the 

average RPEs, the five model year cost of $8.2B in the primary analysis increases to 

$9.5B, an increase of 16 percent. The agencies request comment accompanied by

supporting data on the use of ICMs and RPE factors to estimate fixed costs.

 

340 Helfand, Gloria, and Todd Sherwood. “Documentation of the Development of Indirect Cost Multipliers 

for Three Automotive Technologies.” Memorandum, Assessment and Standards Division, Office of 

Transportation and Air Quality, U.S. Environmental Protection Agency, August 2009.

341 NHTSA staff participated in the development of the process for the second, modified Delphi panel, and 

reviewed the results as they were developed, but did not serve on the panel.

342 The results of the RTI report were published in Alex Rogozhin, Michael Gallaher, Gloria Helfand, and 

Walter McManus, “Using Indirect Cost Multipliers to Estimate the Total Cost of Adding New Technology 

in the Automobile Industry.” International Journal of Production Economics 124 (2010): 360-368.
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D. Cost per Ton of Emissions Reductions

The agencies have calculated the cost per ton of GHG (CO2-equivalent, or CO2e) 

reductions associated with this proposal using the above costs and the emissions 

reductions described in Sections VI and VII. The cost per metric ton of GHG emissions 

reductions has been calculated in the years 2020, 2030, 2040, and 2050 using the annual 

vehicle compliance costs and emission reductions for each of those years. The value in 

2050 represents the long-term cost per ton of the emissions reduced. The agencies have 

also calculated the cost per metric ton of GHG emission reductions including the savings 

associated with reduced fuel consumption (presented below in Section VIII. E. ). This 

latter calculation does not include the other benefits associated with this proposal such as 

those associated with energy security benefits as discussed later in Section VIII.I. By

including the fuel savings in the cost estimates, the cost per ton is less than $0 since the 

estimated value of fuel savings outweighs the program costs. The results for CO2 costs 

per ton under the proposal are shown in Table VIII-3.

Table VIII-3: Annual Cost Per Metric Ton of CO2 Reduced ($2008 dollars)

Year Program 

Cost

Fuel 

Savings

(post-tax)

CO2 

Reduced

Cost per Ton 

(without Fuel 

Savings)

Cost per Ton 

(with Fuel 

Savings)

2020 $2,100 $9,300 36 $60 -$200

2030 $2,000 $21,100 73 $30 -$260

2040 $2,300 $30,700 94 $20 -$300

2050 $2,600 $38,200 114 $20 -$310

E. Impacts of Reduction in Fuel Consumption

(1) What are the Projected Changes in Fuel Consumption

The new CO2 standards will result in significant improvements in the fuel 

efficiency of affected trucks. Drivers of those trucks will see corresponding savings 

associated with reduced fuel expenditures. The agencies have estimated the impacts on 

fuel consumption for the tailpipe CO2 standards. To do this, fuel consumption is 

calculated using both current CO2 emission levels and the new CO2 standards. The 

difference between these estimates represents the net savings from the CO2 standards. 

Note that the total number of miles that vehicles are driven each year is different under 

the control case scenario than in the reference case due to the “rebound effect,” which is 

discussed in Section (5) VIII. E. (5) . EPA also notes that drivers who drive more than 

our average estimates for vehicle miles traveled (VMT) will experience more fuel 

savings; drivers who drive less than our average VMT estimates will experience less fuel 

savings. 

The expected impacts on fuel consumption are shown in Table VIII-4. The 

gallons shown in the tables reflect impacts from the new CO2 standards and include 

increased consumption resulting from the rebound effect.
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Table VIII-4: Fuel Consumption Impacts of the Proposal (Million gallons)

Year Gasoline Diesel

2014 1.7 316

2015 4.9 624

2016 19 931

2017 39 1,393

2018 71 1,861

2020 132 2,723

2030 352 5,412

2040 468 7,004

2050 569 8,453

(2) Potential Impacts on Global Fuel Use and Emissions 

EPA’s quantified reductions in fuel consumption focus on the gains from 

reducing fuel used by heavy-duty vehicles within the United States. However, as 

discussed in section VIII.I, EPA also recognizes that this regulation will lower the world 

price of oil (the “monopsony” effect). Lowering oil prices could lead to an uptick in oil 

consumption globally, leading to a corresponding increase in GHG emissions in other 

countries. This global increase in emissions could slightly offset some of the emission 

reductions achieved domestically as a result of the regulation. 

EPA does not provide quantitative estimates of the impact of the regulation on 

global petroleum consumption and GHG emissions but invites comment on whether to 

consider this impact.

(3) What are the Monetized Fuel Savings?

Using the fuel consumption estimates presented in Table VIII-4, the agencies can 

calculate the monetized fuel savings associated with the proposed standards. To do this, 

reduced fuel consumption is multiplied in each year by the corresponding estimated 

average fuel price in that year, using the reference case taken from the AEO 2010. 

These estimates do not account for the significant uncertainty in future fuel prices; the 

monetized fuel savings will be understated if actual fuel prices are higher (or overstated if 

fuel prices are lower) than estimated. AEO is a standard reference used by NHTSA and 

EPA and many other government agencies to estimate the projected price of fuel. This

has been done using both the pre-tax and post-tax fuel prices. Since the post-tax fuel 

prices are the prices paid at fuel pumps, the fuel savings calculated using these prices 

represent the savings consumers would see. The pre-tax fuel savings are those savings 

that society would see. These results are shown in Table VIII-5. Note that in Section 

VIII.K, the overall benefits and costs of the rule are presented and, for that reason, only 

the pre-tax fuel savings are presented there. The agencies also request comment on the 

additional information that would be provided by conducting sensitivity analysis that 

considers the effect of uncertainty in future fuel prices on estimated fuel savings. For 

instance, the Agencies could conduct sensitivity analyses by relying on the AEO2010 low 

oil price and high oil price scenarios.
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Table VIII-5: Estimated Monetized Fuel Savings ($Millions of 2008 dollars)

Year Fuel Savings

(pre-tax)

Fuel Savings

(post-tax)

2014 $700 $800

2015 $1,400 $1,700

2016 $2,200 $2,700

2017 $3,600 $4,200

2018 $5,000 $5,900

2020 $8,000 $9,300

2030 $18,900 $21,100

2040 $28,000 $30,700

2050 $35,200 $38,200

NPV, 3% $351,100 $389,900

NPV, 7% $152,100 $170,100

As shown in Table VIII-5, the agencies are projecting that truck consumers would 

realize very large fuel savings as a result of the proposed standards. As discussed further 

in the introductory paragraphs of Section VIII, it is a conundrum from an economic 

perspective that these large fuel savings have not been provided by manufacturers and 

purchased by consumers of these products. Unlike in the light-duty vehicle market, the 

vast majority of vehicles in the medium- and heavy-duty truck market are purchased and 

operated by businesses; for them, fuel costs may represent substantial operating expenses. 

Even in the presence of uncertainty and imperfect information – conditions that hold to 

some degree in every market – we generally expect firms to be cost-minimizing to 

survive in a competitive marketplace and to make decisions that are therefore in the best 

interest of the company and its owners and/or shareholders.

A number of behavioral and market phenomena may lead to a disconnect between 

how businesses account for fuel savings in their decisions and the way in which we 

account for the full stream of fuel savings for this rule, including imperfect information in 

the original and resale markets, split incentives, uncertainty in future fuel prices, and 

adjustment or transactions costs (see Section VIII.A for a more detailed discussion). As 

discussed below in the context of rebound in Section VIII.E.5, the nature of the 

explanation for this gap may influence the actual magnitude of the fuel savings. The 

agencies request comment on this issue as discussed in more detail in Section VIIIA. The 

agencies also request comment on the interest in a sensitivity analysis that considers the 

role of fuel price uncertainty by considering lower and higher future fuel prices scenarios. 

(4) Payback Period and Lifetime Savings on New Truck Purchases

Another factor of interest is the payback period on the purchase of a new truck 

that complies with the new standards. In other words, how long would it take for the 

expected fuel savings to outweigh the increased cost of a new vehicle? For example, a 

new 2018 MY 2b/3 truck is estimated to cost $1,458 more, a vocational truck $349 more, 
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and a combination truck $6,403 more (all values are on average, and relative to the 

reference case vehicle, see Table VIII-1) due to the addition of new GHG reducing 

technology. This new technology will result in lower fuel consumption and, therefore, 

savings in fuel expenditures. But how many months or years would pass before the fuel 

savings exceed the upfront costs? 

Table VIII-6 shows the payback period analysis for Class 2b and 3 pickup trucks 

and vans. The table shows fuel consumed under the reference case and fuel consumed by

a 2018 model year truck under the proposal, inclusive of fuel consumed due to rebound 

miles. The decrease in fuel consumed under the proposal is then monetized by

multiplying by the fuel price reported by AEO (reference case) in 2018. This value 

represents the fuel savings expected under the proposal for a Class 2b and 3 pickup or 

van. These savings are then discounted each year since future savings are considered to 

be of less value than current savings. Shown next are estimated increased costs (costs do 

not necessarily reflect increased prices which may be higher or lower than costs) for the 

new truck (refer to Table VIII-1). The next columns show the period required for the fuel 

savings to exceed the new truck costs. As seen in the table, in the fifth year of 

ownership, the discounted fuel savings (at 3%) have begun to outweigh the increased cost 

of the truck. Using 7% discounting, this payback occurs in year 6. As shown in the 

table, the full life savings using 3% discounting would be $2,460 and at 7% discounting 

would be $1,500.

Table VIII-6: Payback Period for a 2018 Model Year Class 2b/3 Pickup or Van (2008$)

Year of 

Ownersh

ip

Fuel Use (gallons) Fuel Savings ($)aIncreas

ed Cost 

($)

Cumulative Savings 

($)

Referen

ce Case

Proposa

l

b

Discount

ed at 3%

Discount

ed at 7%

Discount

ed at 3%

Discount

ed at 7%

1 921 812 $327 $321 -$1,458 -$1,131 -$1,137

2 903 797 $321 $303 -$810 -$833

3 884 779 $315 $286 -$495 -$547

4 857 756 $303 $266 -$192 -$282

5 824 727 $291 $245 $99 -$37

6 786 693 $273 $222 $372 $185

7 742 654 $253 $198 $625 $383

Full Life 12,103 10,670 $3,913 $2,969 -$1,458 $2,455 $1,512

Notes:

a

Fuel savings calculated using the AEO 2010 reference case fuel prices. Gasoline and diesel fuel prices 

have been weighted by gasoline and diesel fuel reductions estimated for all 2018MY heavy-duty trucks 

during their lifetimes.

b Gallons under the proposal case include gallons consumed during rebound driving.

The story is somewhat different for vocational trucks and combination trucks. 

These cases are shown in Table Table VIII-7 and Table Table VIII-8, respectively. Since 

these trucks travel more miles in a given year, their payback periods are much shorter and 

actually are expected to occur within the first year of ownership under both the 3% and 
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7% discounting cases. As can be seen in Tables Table VIII-7 and Table VIII-8, the 

lifetime fuel savings are estimated to be considerable with savings of $4,000 (3%) and 

$3,100 (7%) for the vocational trucks and over $73,000 (3%) and $57,000 (7%) for the 

combination trucks.

Table VIII-7: Payback Period for a 2018 Model Year Vocational Truck (2008$)

Year of 

Ownersh

ip

Fuel Use (gallons) Fuel Savings ($)aIncreas

ed Cost 

($)

Cumulative Savings 

($)

Referen

ce Case

Proposa

l

b

Discount

ed at 3%

Discount

ed at 7%

Discount

ed at 3%

Discount

ed at 7%

1 2,093 1,928 $495 $486 -$349 $147 $138

2 1,917 1,766 $453 $428 $600 $566

3 1,755 1,617 $415 $378 $1,015 $944

4 1,601 1,475 $376 $330 $1,392 $1,273

5 1,448 1,334 $339 $286 $1,731 $1,559

6 1,303 1,200 $300 $244 $2,031 $1,803

7 1,177 1,084 $266 $208 $2,297 $2,010

Full Life 20,030 18,464 $4,345 $3,413 -$349 $3,996 $3,065

Notes:

a

Fuel savings calculated using the AEO 2010 reference case fuel prices. Gasoline and diesel fuel prices 

have been weighted by gasoline and diesel fuel reductions estimated for all 2018MY heavy-duty trucks 

during their lifetimes.

b Gallons under the proposal case include gallons consumed during rebound driving.
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Table VIII-8: Payback Period for a 2018 Model Year Combination Truck (2008$)

Year of 

Ownershi

p

Fuel Use (gallons) Fuel Savings ($)aIncrease

d Cost 

($)

Cumulative Savings ($)

Referenc

e Case

Proposal

b

Discounte

d at 3%

Discounte

d at 7%

Discounte

d at 3%

Discounte

d at 7%

1 30,257 27,011 $9,746 $9,567 -$6,403 $3,343 $3,164

2 27,801 24,814 $8,968 $8,474 $12,311 $11,638

3 25,415 22,681 $8,223 $7,480 $20,535 $19,117

4 23,049 20,566 $7,426 $6,502 $27,961 $25,620

5 20,652 18,425 $6,636 $5,593 $34,597 $31,213

6 18,353 16,371 $5,820 $4,722 $40,417 $35,935

7 16,325 14,559 $5,092 $3,977 $45,510 $39,912

Full Life 261,897 233,569 $79,711 $64,032 -$6,403 $73,308 $57,629

Notes:

a

Fuel savings calculated using the AEO 2010 reference case fuel prices. Gasoline and diesel fuel prices 

have been weighted by gasoline and diesel fuel reductions estimated for all 2018MY heavy-duty trucks 

during their lifetimes.

b Gallons under the proposal case include gallons consumed during rebound driving.

All of these payback analyses include fuel consumed during rebound VMT in the 

proposal or control case but not in the reference case, consistent with other parts of the 

analysis. Further, this analysis does not include other societal impacts such as reduced 

time spent refueling or noise, congestion and accidents since the focus is meant to be on 

those factors consumers think about most while in the showroom considering a new car 

purchase.

(5) Rebound Effect

The VMT rebound effect refers to the fraction of fuel savings expected to result 

from an increase in fuel efficiency that is offset by additional vehicle use. If truck 

shipping costs decrease as a result of lower fuel costs, an increase in truck VMT may

occur. Unlike the light-duty rebound effect, the medium-duty and heavy-duty rebound 

effect has not been extensively studied. Because the factors influencing the medium- and 

heavy-duty rebound effect are generally different from those affecting the light-duty 

rebound effect, much of the research on the light-duty rebound effect is not likely to 

apply to the medium- and heavy-duty sectors. One of the major differences between the 

medium- and heavy-duty rebound effect and the light-duty rebound effect is that heavyduty trucks are used primarily for commercial and business purposes. Since these 

businesses are profit driven, decision makers are highly likely to be aware of the costs 

and benefits of different shipping decisions, both in the near term and long term. 

Therefore, shippers are much more likely to take into account changes in the overall 

operating costs per mile when making shipping decisions that affect VMT. 
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Another difference from the light-duty case is that, as discussed in the recent NAS 

Report343, when calculating the percentage change in trucking costs to determine the 

rebound effect, all changes in the operating costs should be considered. The cost of labor 

and fuel generally constitute the top two shares of truck operating costs, depending on the 

price of petroleum,.344, distance traveled, type of truck, and commodity.

345

 Finally, the 

equipment costs associated with the purchase or leasing of the truck is also a significant 

component of total operating costs. Even though vehicle costs are lump-sum purchases, 

they can be considered operating costs for trucking firms, and these costs are, in many

cases, expected to be passed onto the final consumers of shipping services on a variable 

basis. This shipping cost increase could help temper the rebound effect relative to the 

case of light-duty vehicles, in which vehicle costs are not considered operating costs.

When calculating the net change in operating costs, both the increase in new 

vehicle costs and the decrease in fuel costs per mile should be taken into consideration. 

The higher the net cost savings, the higher the expected rebound effect. Conversely, if 

the upfront vehicle costs outweighed future cost savings and total costs increased, 

shipping costs would rise, which would likely result in a decrease in truck VMT. In 

theory, other changes such as maintenance costs and insurance rates would also be taken 

into account, although information on these potential cost changes is extremely limited. 

We invite comment on the most appropriate methodology for factoring new vehicle 

purchase or leasing costs into the per-mile operating costs. We also invite comment or 

data on how these regulations could affect maintenance, insurance, or other operating 

costs.

The following sections describe the factors affecting the rebound effect, different 

methodologies for estimating the rebound effect, and examples of different estimates of 

the rebound effect to date. According to the NAS study, it is “not possible to provide a 

confident measure of the rebound effect,” yet NAS concluded that a rebound effect likely

exists and that “estimates of fuel savings from regulatory standards will be somewhat 

misestimated if the rebound effect is not considered.” While we believe the medium- and 

heavy- duty rebound effect needs to be studied in more detail, we have attempted to 

capture the potential impact of the rebound effect in our analysis. For this proposal, we 

have used a rebound effect for single unit trucks of 15%, a rebound effect for medium 

duty (2b and 3) trucks of 10%, and a rebound effect for combination tractors of 5%. 

These VMT impacts are reflected in the estimates of total GHG and other air pollution 

reductions presented in Chapter 5 of the draft RIA. We invite comment and the 

submission of additional data on the medium-duty and heavy-duty rebound effect. 

 

343 National Academy of Sciences (NAS) Report, 2010. Technologies and Approaches to Reducing the 

Fuel Consumption of Medium- and Heavy-Duty Vehicles. See http://www.nap.edu/catalog/12845.html

344 American Transportation Research Institute, An Analysis of the Operational Costs of Trucking, 

December 2008. 

345 Transport Canada, Operating Cost of Trucks, 2005. See http://www.tc.gc.ca/eng/policy/report-acgoperatingcost2005-2005-e-2-1727.htm, accessed on July 16, 2010. See also ATRI, 2008.
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(a) Factors Affecting the Magnitude of the Rebound Effect

The heavy-duty vehicle rebound effect is driven by the interaction of several 

different factors. In the short-run, decreasing the fuel cost per mile of driving could lead 

to a decrease in end product prices. Lower prices could stimulate additional demand for 

those products, which would then result in an increase in VMT. In the long run, shippers 

could reorganize their logistics and distribution networks to take advantage of lower truck 

shipping costs. For example, shippers may shift away from other modes of shipping such 

as rail, barge, or air. In addition, shippers may also choose to reduce the number of 

warehouses, reduce load rates, and make smaller, more frequent shipments, all of which 

could also lead to an increase in heavy-duty VMT. Finally, the benefits of the fuel 

savings could ripple through the economy and increase GDP, which would in turn 

increase overall demand for goods and services, and therefore increase truck VMT. 

Conversely, if a fuel economy regulation leads to net increases in the cost of 

trucking because fuel savings do not fully offset the increase in upfront vehicle costs, 

then the price of trucking services could rise, spurring a decrease in heavy-duty VMT and 

shift to rail shipping. These effects would also ripple through the economy.

Because these factors have not been well studied to date, the interaction and 

potential magnitude of these impacts is not well understood. However, the rebound 

effect is one of the determinants of the fuel savings likely to result from adopting stricter 

fuel economy or GHG emissions standards, and is thus an important parameter affecting 

EPA’s evaluation of alternative standards for future model years. Therefore, we invite 

submission of data regarding the medium- and heavy-duty rebound effect.

(b) Options for Quantifying the Rebound Effect

As described in the previous section, the fuel economy rebound effect for heavyduty trucks has not been studied as extensively as the rebound effect for light-duty

vehicles, and virtually no research has been conducted on the medium-duty truck rebound 

effect. In this proposal, we discuss four options for quantifying the rebound effect. We 

invite comment on these options, and we also welcome comment on other possible 

methodologies. 

(i) Aggregate Estimates

The aggregate approximation approach quantifies the overall change in truck 

VMT as a result of a percentage change in truck shipping prices. This approach relies on 

estimates of aggregate price elasticity of demand for trucking services, given a 

percentage change in trucking prices, which is generally referred to as an “own-price 

elasticity.” Estimates of trucking own-price elasticities vary widely, and there is no 

general consensus on the most appropriate values to use. A 2004 literature survey cited 

in the recent NAS report346 found aggregate elasticity estimates in the range of -0.5 to -

 

346 NAS Report, 2010.
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1.5.347 In other words, given an own-price elasticity of -1.5, a 10% decrease in trucking 

prices leads to a 15% increase in demand for truck shipping demand. However, this 

survey does not differentiate between studies that quantify change in tons shipped or tonmiles. In addition, most of the studies find that these elasticity estimates vary

substantially based on the length of the trip and the type of cargo. For example, one 

study estimated an own-price elasticity of -0.1 for the lumber sector and -2.3 for the 

chemical sector.348 

The increase in overall truck VMT resulting from the rebound effect implicitly

includes some component of mode shifting. Since there are differences in GHG 

emissions per ton of freight moved by rail compared to truck, any potential shifting of 

freight from one mode to the other could have GHG impacts. Although the total demand 

for freight transport is generally determined by economic activity, there is often the 

choice of shipping by either truck or by rail when freight is transported over land routes. 

This is because the United States has both an extensive highway network and an 

extensive rail network; these networks closely parallel each other and are often both 

viable choices for freight transport for many origin and destination pairs within the 

continent. If rates go down for one mode, there will be an increase in demand for that 

mode and some demand will be shifted from other modes. This “cross-price elasticity” is 

a measure of the percentage change in demand for shipping by another mode (e.g., rail) 

given a percentage change in the price of trucking. Aggregate estimates of cross-price 

elasticities also vary widely, and there is no general consensus on the most appropriate 

value to use for analytical purposes. The NAS report cites values ranging from 0.35 to 

0.59.349 Other reports provide significantly different cross-price elasticities, ranging from 

0.1350 to 2.0.351 

When considering intermodal shift, the most relevant kinds of shipments are those 

that are competitive between rail and truck modes. These trips include long-haul 

shipments greater than 500 miles, which weigh between 50,000 and 80,000 pounds (the 

legal road limit in many states). Special kinds of cargo like coal and short-haul deliveries 

are of less interest because they are generally not economically transferable between 

truck and rail modes, and they would not be expected to shift modes except under an 

extreme price change. However, the total volume of ton-miles that could potentially be 

subject to mode shifting has also not been studied extensively. 

 

347 Graham and Glaister, “Road Traffic Demand Elasticity Estimates: A Review,” Transport Reviews 

Volume 24, 3, pp. 261-274, 2004. 

348 Winston, C. (1981). The welfare effects of ICC rate regulation revisited. The Bell Journal of Economics, 

12, 232-244.

349 2010 NAS Report. See also 2009 Cambridge Systematics, Inc., Draft Final Paper commissioned by the 

NAS in support of the medium-duty and heavy-duty report. Assessment of Fuel Economy Technologies 

for Medium and Heavy Duty Vehicles: Commissioned Paper on Indirect Costs and Alternative 

Approaches. 

350 Friedlaender, A. and Spady, R. (1980) A derived demand function for freight transportation, Review of

Economics and Statistics, 62, pp. 432–441.

351 Christidis and Leduc, “Longer and Heavier Vehicles for freight transport,” European Commission Joint 

Research Center’s Institute for Prospective Technology Studies, 2009. 
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(ii) Sector-Specific Estimates

Given the limited data available regarding the medium- and heavy- duty rebound 

effect, the aggregate approach greatly simplifies many of the assumptions associated with 

calculations of the rebound effect. In reality, however, responses to changes in fuel 

efficiency and new vehicle costs will vary significantly based on the commodities 

affected. A detailed, sector-specific approach would be expected to more accurately

reflect changes in the trucking market given these standards. For example, input-output 

tables could be used to determine the trucking cost share of the total delivered price of a 

product or sector. Using the change in trucking prices described in the aggregate 

approach, the product-specific demand elasticities could be used to calculate the change 

in sales and shipments for each product. The change in shipment increases could then be 

weighted by the share of the trucking industry total, and then summed to get the total 

increase in trucking output. A simplifying assumption could then be made that the 

increase in output results in an increase in VMT. This type of detailed data has not yet 

been collected, so we do not have any calculations available for the proposal. While we 

hope to have this data available for the final rulemaking, gathering high quality data may

take a longer time frame. We invite the submission of comments or data that could be 

used as part of this methodology. 

(iii) Econometric Estimates 

Similar to the methodology used to estimate the light-duty rebound effect, the 

heavy-duty rebound effect could be modeled econometrically by estimating truck demand 

as a function of economic activity (e.g., GDP) and different input prices (e.g., vehicle 

prices, driver wages, and fuel costs per mile). This type of econometric model could be 

estimated for either truck VMT or ton-miles as a measure of demand. The resulting 

elasticity estimates could then be used to determine the change in trucking demand, given 

the change in fuel cost and truck prices per mile from these standards. 

(iv) Other Modeling Approaches

Regulation of the heavy-duty industry has been studied in more detail in Europe, 

as the European Commission (EC) has considered allowing longer and heavier trucks for 

freight transport. Part of the analysis considered by the EC relies on country-specific 

modeling of changes in the freight sector that would result from changes in regulations.352 

This approach attempts to explicitly calculate modal shift decisions and impacts on GHG 

emissions. Although similar types of analysis have not been conducted extensively in the 

U.S., research is currently underway that explores the potential for intermodal shifting in 

the U.S. For example, Winebrake and Corbett have developed the Geospatial Intermodal 

Freight Transportation (GIFT) model, which evaluates the potential for GHG emissions 

reductions based on mode shifting, given existing limitations of infrastructure and other 

 

352 Christidis and Leduc, “Longer and Heavier Vehicles for freight transport,” European Commission Joint 

Research Center’s Institute for Prospective Technology Studies, 2009. 
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route characteristics in the U.S. 353 This model connects multiple road, rail, and 

waterway transportation networks and embeds activity-based calculations in the model. 

Within this intermodal network, the model assigns various economic, time-of-delivery, 

energy, and environmental attributes to real-world goods movement routes. The model 

can then calculate different network optimization scenarios, based on changes in prices 

and policies.354 However, more work is needed in this area to determine whether this 

type of methodology is appropriate for the purposes of capturing the rebound effect. We 

invite comment on this approach, as well as suggestions on alternative modeling 

frameworks that could be used to assess mode shifting, fuel consumption, and the GHG 

emission implications of these proposed regulations. 

(c) Estimates of the Rebound Effect

The aggregate methodology was used by Cambridge Systematics, Inc. (CSI) to 

show several examples of the magnitude of the rebound effect. 355 In their paper 

commissioned by the NAS in support of the recent medium- and heavy-duty report, CSI

calculated an effective rebound effect for two different technology cost and fuel savings 

scenarios associated with an example Class 8 truck. Scenario 1 increased average fuel 

economy from 5.59 mpg to 6.8 mpg, with an additional cost of $22,930. Scenario 2 

increased the average fuel economy to 9.1 mpg, at an incremental cost of $71,630 per 

vehicle. The CSI examples provided estimates using a range of own-price elasticities (-

0.5 to -1.5) and cross-price elasticities (0.35 to 0.59) from the literature. Based on these 

two scenarios and a number of simplifying assumptions to aid the calculations, CSI found 

a rebound effect of 11-31% for Scenario 1 and 5-16% for Scenario 2 when the fuel 

savings from rail were not taken into account (“First rebound effect”). When the fuel 

savings from reduced rail usage were included in the calculations, the overall rebound 

effect was between 9-13% for Scenario 1 and 3-15% for Scenario 2 (“Second Rebound 

Effect”). See Table VIII-9.

CSI included a number of caveats associated with these calculations. Namely, the 

elasticity estimates derived from the literature are “heavily reliant on factors including the 

type of demand measures analyzed (vehicle-miles of travel, ton-miles, or tons), analysis 

geography, trip lengths, markets served, and commodities transported.” Furthermore, the 

CSI example only focused on Class 8 combination tractors and did not attempt to 

quantify the potential rebound effect for any other truck classes. Finally, these scenarios 

were characterized as “sketches” and were not included in the final NAS report. In fact, 

the NAS report asserted that it is “not possible to provide a confident measure of the 

 

353 Winebrake, James and James J. Corbet (2010). “Improving the Energy Efficiency and Environmental 

Performance of Goods Movement,” in Sperling, Daniel and James S. Cannon (2010) Climate and 

Transportation Solutions: Findings from the 2009 Asilomar Conference on Transportation and Energy 

Policy. See http://www.its.ucdavis.edu/events/2009book/Chapter13.pdf

354 Winebrake, J. J.; Corbett, J. J.; Falzarano, A.; Hawker, J. S.; Korfmacher, K.; Ketha, S.; Zilora, S., 

Assessing Energy, Environmental, and Economic Tradeoffs in Intermodal Freight Transportation, Journal 

of the Air & Waste Management Association, 58(8), 2008.

355 Cambridge Systematics, Inc., “Assessment of Fuel Economy Technologies for Medium and Heavy Duty 

Vehicles: Commissioned Paper on Indirect Costs and Alternative Approaches,” September 17, 2009, 
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rebound effect,” yet concluded that a rebound effect likely exists and that “estimates of 

fuel savings from regulatory standards will be somewhat misestimated if the rebound 

effect is not considered.” 

Table VIII-9: Range of Rebound Effect Estimates from Cambridge Systematics Aggregate 

Assessment

Scenario 1 

(6.8 mpg, $22,930)

Scenario 2

(9.1 mpg, $71,630)

“First Rebound Effect” (increase in truck 

VMT resulting from decrease in 

operating costs)

11-31% 5-16%

“Second Rebound Effect” (net fuel 

savings when decreases from rail are 

taken into account)

9-13 % 3-15%

As an alternative, using the econometric approach, NHTSA has estimated the 

rebound effect in the short run and long run for single unit (Class 4-7) and (Class 8) 

combination tractors. As shown in Table VIII-10:, the estimates for the long-run rebound 

effect are larger than the estimates in the short run, which is consistent with the theory

that shippers have more flexibility to change their behavior (e.g., restructure contracts or 

logistics) when they are given more time. In addition, the estimates derived from the 

national data also showed larger rebound effects compared to the state data.356 One 

possible explanation for the difference in the estimates is that the national rebound 

estimates are capturing some of the impacts of changes in economic activity. 

Historically, large increases in fuel prices are highly correlated with economic 

downturns, and there may not be enough variation in the national data to differentiate the 

impact of fuel price changes from changes in economic activity. In contrast, some states 

may see an increase in output when energy prices increase (e.g., large oil producing states 

such as Texas and Alaska); therefore, the state data may be more accurately isolating the 

individual impact of fuel price changes.

Table VIII-10: Range of Rebound Effect Estimates from NHTSA Econometric Analysis

Truck Type National Data State Data

 

356 NHTSA’s estimates of the rebound effect are derived from econometric analysis of national and state 

VMT data reported in Federal Highway Administration, Highway Statistics, various editions, Tables VM-1 

and VM-4. Specifically, the estimates of the rebound effect reported in Table VIII-10 are ranges of the 

estimated short-run and long-run elasticities of annual VMT by single-unit and combination trucks with 

respect to fuel cost per mile driven. (Fuel cost per mile driven during each year is equal to average fuel 

price per gallon during that year divided by average fuel economy of the truck fleet during that same year.) 

These estimates are derived from time-series regression of annual national aggregate VMT for the period 

1970-2008 on measures of nationwide economic activity, including aggregate GDP, the value of durable 

and nondurable goods production, and the volume of U.S. exports and imports of goods, and variables 

affecting the price of trucking services (driver wage rates, truck purchase prices, and fuel costs), and from 

regression of VMT for each individual state over the period 1994-2008 on similar variables measured at the 

state level.
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Short Run Long Run Short Run Long Run

Single Unit 13-22% 28-45% 3-8% 12-21%

Combination N/A 12-14% N/A 4-5%

As discussed throughout this section, there are multiple methodologies for 

quantifying the rebound effect, and these different methodologies produce a large range 

of potential values of the rebound effect. However, for the purposes of quantifying the 

rebound effect for this proposal, we have used a rebound effect with respect to changes in 

fuel costs per mile on the lower range of the long-run estimates. Given the fact that the 

long-run state estimates are generally more consistent with the aggregate estimates, for 

this proposal we have chosen a rebound effect for single unit trucks of 15% that is within 

the range of estimates from both methodologies. Similarly, we have chosen a rebound 

effect for combination tractors of 5%. 

To date, no estimates of the medium-duty (2b and 3) rebound effect have been 

cited in the literature. Since medium-duty vehicles are used for very different purposes 

than heavy-duty vehicles, it does not necessarily seem appropriate to apply one of the 

heavy-duty estimates to the 2b and 3 classes. Class 2b and 3 vehicles are more similar in 

use to large light-duty vehicles, so for the purposes of our analysis, we have chosen to 

apply the light-duty rebound effect of 10% to this class of vehicles. 

For the purposes of this proposal, we have not taken into account any potential 

fuel savings or GHG emission reductions from the rail sector due to mode shifting. 

However, we have provided CSI’s example calculations and request comment on these 

values. 

Furthermore, we have made a number of simplifying assumptions in our 

calculations, which are discussed in more detail in the RIA. Specifically, we have not 

attempted to capture how current market failures might impact the rebound effect. The 

direction and magnitude of the rebound effect in the medium- and heavy-duty truck 

market are expected to vary depending on the existence and types of market failures 

affecting the fuel economy of the trucking fleet. If firms are already accurately

accounting for the costs and benefits of these technologies and fuel savings, then these 

regulations would increase their net costs, because trucks would already include all the 

cost-effective technologies. As a result, the rebound effect would actually be negative 

and truck VMT would decrease as a result of these proposed regulations. However, if 

firms are not optimizing their behavior today due to factors such as lack of reliable 

information (see Section VIII.A. for further discussion), it is more likely that truck VMT 

would increase. If firms recognize their lower net costs as a result of these regulations 

and pass those costs along to their customers, then the rebound effect would increase 

truck VMT. This response assumes that trucking rates include both truck purchase costs 

and fuel costs, and that the truck purchase costs included in the rates spread those costs 

over the full expected lifetime of the trucks. If those costs are spread over a shorter 

period, as the expected short payback period implies, then those purchase costs will 

inhibit reduction of freight rates, and the rebound effect will be smaller. 
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As discussed in more detail in Section VIII.A, if there are market failures such as 

split incentives, estimating the rebound effect may depend on the nature of the failures. 

For example, if the original purchaser cannot fully recoup the higher upfront costs 

through fuel savings before selling the vehicle nor pass those costs onto the resale buyer, 

the firm would be expected to raise shipping rates. A firm purchasing the truck secondhand might lower shipping rates if the firm recognizes the cost savings after operating the 

vehicle, leading to an increase in VMT. Similarly, if there are split incentives and the 

vehicle buyer isn’t the same entity that purchases the fuel, than there would theoretically 

be a positive rebound effect. In this scenario, fuel savings would lower the net costs to 

the fuel purchaser, which would result in a larger increase in truck VMT. 

If all of these scenarios occur in the marketplace, the net effect will depend on the 

extent and magnitude of their relative effects, which are also likely to vary across truck 

classes (for instance, split incentives may be a much larger problem for class 7 and 8 

tractors than they are for heavy duty pickup trucks). Additional details on the rebound 

effect are included in the draft RIA. We invite comment on all of the rebound estimates 

and assumptions. 

F. Class Shifting and Fleet Turnover Impacts

The agencies considered two additional potential indirect costs, benefits, effects, 

and externalities which may lead to unintended consequences of the proposal to improve

the fuel efficiency and reduce GHG emissions from HD trucks. The next sections cover 

the agencies’ qualitative discussions on potential class shifting and fleet turnover effects.

(1) Class shifting

Heavy duty vehicles are typically configured and purchased to perform a function. 

For example, a concrete mixer truck is purchased to transport concrete, a combination 

tractor is purchased to move freight with the use of a trailer, and a Class 3 pickup truck 

could be purchased by a landscape company to pull a trailer carrying lawnmowers. The 

purchaser makes decisions based on many attributes of the vehicle, including the gross 

vehicle weight rating of the vehicle which in part determines the amount of freight or 

equipment that can be carried. If the agencies propose a regulation that impacts either the 

performance of the vehicle or the marginal cost of the vehicle relative to the other vehicle 

classes, then consumers could choose to purchase a different vehicle which may result in 

an unintended consequence of increased fuel consumption and GHG emissions in-use.

The agencies, along with the NAS panel, found that there is little or no literature 

which evaluates class shifting between trucks.357 The agencies welcome comments that 

would help inform the evaluation of this potential impact. NHTSA and EPA qualitatively

evaluated the proposed rule in light of potential class shifting. The agencies looked at 

four potential cases of shifting - from light duty pickup trucks to heavy duty pickup 

 

357 NAS. Page 6-38.
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trucks, from sleeper cabs to day cabs, from combination tractors to vocational trucks, and 

within vocational trucks.

Light duty pickup trucks, those with a GVWR of less than 8,500 pounds, are 

currently regulated under the existing CAFE program and will meet GHG emissions 

standards beginning in 2012. The increased stringency of the 2012-2016 light-duty GHG 

and CAFE rule has led some to speculate that vehicle consumers may choose to purchase 

heavy-duty pickup trucks that are currently unregulated if the cost of the light-duty

regulation is high relative to the cost to buy the larger heavy-duty pickup trucks. Since 

fuel consumption and GHG emissions rise significantly with vehicle mass, a shift from 

light-duty trucks to heavy-duty trucks would likely lead to higher fuel consumption and 

GHG emissions, an untended consequence of the regulations. Given the significant price 

premium of a heavy-duty truck (often five to ten thousand dollars more than a light-duty 

pickup), we believe that such a class shift would be unlikely even absent today’s 

proposed regulations. With today’s proposed regulation, any incentive for such a class 

shift is significantly diminished. The proposed regulations for the HD pickup trucks, and 

similarly for vans, are based on similar technologies and therefore reflect a similar 

expected increase in cost when compared to the light-duty GHG regulation. Hence, the 

combination of the two regulations provides little incentive for a shift from light-duty

trucks to HD trucks. To the extent that our proposed regulation of heavy-duty pickups 

and vans could conceivably encourage a class shift towards lighter pickups, this 

unintended consequence would in fact be expected to lead to lower fuel consumption and 

GHG emissions as the smaller light-duty pickups are significantly more efficient than 

heavy-duty pickup trucks.

The projected cost increases for our proposal differ significantly between class 8 

day cabs and class 8 sleeper cabs reflecting our expectation that compliance with the 

proposed standards will lead truck consumers to specify sleeper cabs equipped with 

auxiliary power units (APUs) while day cab consumers will not. Since Class 8 day cab 

and sleeper cab trucks perform essentially the same function when hauling a trailer, this 

raises the possibility that the higher cost for an APU equipped sleeper cab could lead to a 

shift from sleeper cab to day cab trucks. We do not believe that such an intended 

consequence will occur for the following reasons. The addition of a sleeper berth to a 

tractor cab is not a consumer-selectable attribute in quite the same way as other vehicle 

features. The sleeper cab provides a utility that long-distance trucking fleets need to 

conduct their operations -- an on-board sleeping berth that lets a driver comply with 

federally-mandated rest periods, as required by the Department of Transportation Federal 

Motor Carrier Safety Administration's hours-of-service regulations. The cost of sleeper 

trucks is already higher than the cost of day cabs, yet the fleets that need this utility

purchase them.358 A day cab simply cannot provide this utility. The need for this utility

would not be changed even if the marginal costs to reduce greenhouse gas emissions 

 

358 A baseline tractor price of a new day cab is $89,500 versus $113,000 for a new sleeper cab based on 

information gathered by ICF in the “Investigation of Costs for Strategies to Reduce Greenhouse Gas 

Emissions for Heavy-Duty On-Road Vehicles”, July 2010. Page 3.
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from sleeper cabs exceed the marginal costs to reduce greenhouse gas emissions from 

day cabs.359 A trucking fleet could decide to put its drivers in hotels in lieu of using 

sleeper berths, and switch to day cabs. However, this is unlikely to occur in any great 

number, since the added cost for the hotel stays would far overwhelm differences in the 

marginal cost between day and sleeper cabs. Even if some fleets do opt to buy hotel 

rooms and switch to day cabs, they would be highly unlikely to purchase a day cab that 

was aerodynamically worse than the sleeper cab they replaced, since the need for features 

optimized for long-distance hauling would not have changed. So in practice, there would 

likely be little difference to the environment for any switching that might occur. Further, 

while our projected costs assume the purchase of an APU for compliance, in fact our 

regulatory structure would allow compliance using a near zero cost software utility that 

eliminates tractor idling after five minutes. Using this compliance approach, the cost 

difference between a class 8 sleeper cab and day cab due to our proposed regulations is 

small. We are providing this alternative compliance approach reflecting that some 

sleeper cabs are used in team driving situations where one driver sleeps while the other 

drives. In that situation, an APU is unnecessary since the tractor is continually being 

driven when occupied. When it is parked, it will automatically eliminate any additional 

idling through the shutdown software. If trucking companies choose this option, then 

costs based on purchase of APUs may overestimate the costs of this rule to this sector.

Class shifting from combination tractors to vocational trucks may occur if a 

customer deems the additional marginal cost of tractors due to the regulation to be greater 

than the utility provided by the tractor. The agencies initially considered this issue when 

deciding whether to include Class 7 tractors with the Class 8 tractors or regulate them as 

vocational trucks. The agencies’ evaluation of the combined vehicle weight rating of the 

Class 7 shows that if these vehicles were treated significantly differently from the Class 8 

tractors, then they could be easily substituted for Class 8 tractors. Therefore, the agencies 

are proposing to include both classes in the tractor category. The agencies believe that a 

shift from tractors to vocational trucks would be limited because of the ability of tractors 

to pick up and drop off trailers at locations which cannot be done by vocational trucks.

The agencies do not envision that the proposed regulatory program will cause 

class shifting within the vocational class. The marginal cost difference due to the 

regulation of vocational trucks is minimal. The cost of low rolling resistance tires on a 

per tire basis is the same for all vocational trucks so the only difference in marginal cost 

of the vehicles is due to the number of axles. The agencies believe that the utility gained 

from the additional load carrying capability of the additional axle will outweigh the 

additional cost for heavier vehicles.360

In conclusion, NHTSA and EPA believe that the proposed regulatory structure for 

HD trucks does not significantly change the current competitive and market factors that 

 

359 The average marginal cost difference between sleeper cabs and day cabs in the proposal is nearly 

$6,000.

360 The proposed rule projects the difference in costs between the HD and MD vocational truck 

technologies is approximately $30.
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determine purchaser preferences among truck types. Furthermore, even if a small amount 

of shifting does occur, any resulting GHG impacts are likely to be negligible because any 

vehicle class that sees an uptick in sales is also being regulated for fuel economy. 

Therefore, the agencies did not include an impact of class shifting on the vehicle 

populations used to assess the benefits of the proposal. The agencies welcome comments 

to inform the benefits assessment of the final rule.

(2) Fleet Turnover Effect

A regulation that increases the cost to purchase and/or operate trucks could impact 

whether a consumer decides to purchase a new truck and the timing of that purchase. 

The term pre-buy refers to the idea that truck purchases may occur earlier than otherwise 

planned to avoid the additional costs associated with a new regulatory requirement. 

Slower fleet turnover, or low-buys, may occur when owners opt to keep their existing 

truck rather than purchase a new truck due to the incremental cost of the regulation. 

The NAS panel discusses the topics associated with HD truck fleet turnover. 

NAS noted that there is some empirical evidence of pre-buy behavior in response to the 

2004 and 2007 heavy-duty engine emission standards, with larger impacts occurring in 

response to higher costs.361 However, those regulations increased upfront costs to firms 

without any offsetting future cost savings from reduced fuel purchases. In summary, NAS 

stated that

...during periods of stable or growing demand in the freight sector, prebuy behavior may have significant impact on purchase patterns, especially

for larger fleets with better access to capital and financing. Under these 

same conditions, smaller operators may simply elect to keep their current 

equipment on the road longer, all the more likely given continued 

improvements in diesel engine durability over time. On the other hand, to 

the extent that fuel economy improvements can offset incremental 

purchase costs, these impacts will be lessened. Nevertheless, when it 

comes to efficiency investments, most heavy duty fleet operators require 

relatively quick payback periods, on the order of two to three years.362 

The regulations the agencies are proposing today are projected to return fuel 

savings to the truck owners that offset the cost of the regulation within a few years for 

vocational trucks and class 7 and 8 tractors, the categories where the potential for prebuy 

and delayed fleet turnover are concerns. In the case of vocational vehicles, the added 

cost is small enough that it is unlikely to have a substantial effect on purchasing behavior. 

In the case of class 7 and 8 trucks, the effects of the regulation on purchasing behavior 

will depend on the nature of the market failures and the extent to which firms consider 

the projected future fuel savings in their purchasing decisions. 

 

361 NAS p. 6-36 – 6-37

362 NAS Report. Page 6-37.
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If trucking firms account for the rapid payback, they are unlikely to strategically 

accelerate or delay their purchase plans at additional cost in capital to avoid a regulation 

that will lower their overall operating costs. As discussed in Section VIII.A., this 

scenario may occur if this proposed rule reduces uncertainty about fuel-saving 

technologies. More reliable information about ways to reduce fuel consumption allows 

truck purchasers to evaluate better the benefits and costs of additional fuel savings, 

primarily in the original vehicle market, but possibly in the resale market as well. 

Other market failures may leave open the possibility of some pre-buy or delayed 

purchasing behavior. Firms may not consider the full value of the future fuel savings for 

several reasons. For instance, truck purchasers may not want to invest in fuel economy 

because of uncertainty about fuel prices. Another explanation is that the resale market 

may not fully recognize the value of fuel savings, due to lack of trust of new technologies 

or changes in the uses of the vehicles. Lack of coordination (also called split 

incentives—see Section VIII.A) between truck purchasers (who emphasize the up-front 

costs of the trucks) and truck operators, who would like the fuel savings, can also lead to 

pre-buy or delayed purchasing behavior. If these market failures prevent firms from fully

internalizing fuel savings when deciding on vehicle purchases, then pre-buy and delayed 

purchase could occur and could result in a slight decrease in the GHG benefits of the 

regulation. 

Thus, whether pre-buy or delayed purchase is likely to play a significant role in 

the truck market depends on the specific behaviors of purchasers in that market. Without 

additional information about which scenario is more likely to be prevalent, the Agencies 

are not projecting a change in fleet turnover characteristics due to this regulation. We 

welcome comments on all aspects of this assumption, especially in the context of our 

assumed increase in truck freight shipments due to a VMT rebound.

G. Benefits of Reducing CO2 Emissions

(1) Social Cost of Carbon

EPA has assigned a dollar value to reductions in carbon dioxide (CO2) emissions 

using recent estimates of the “social cost of carbon” (SCC). The SCC is an estimate of 

the monetized damages associated with an incremental increase in carbon emissions in a 

given year. It is intended to include (but is not limited to) changes in net agricultural 

productivity, human health, property damages from increased flood risk, and the value of 

ecosystem services due to climate change. The SCC estimates used in this analysis were 

developed through an interagency process that included EPA, DOT/NHTSA, and other 

executive branch entities, and concluded in February 2010. We first used these SCC 

estimates in the benefits analysis for the final joint EPA/DOT rule to establish light-duty

vehicle GHG emission etandards and CAFE standards; see the rule’s preamble for 

discussion about application of the SCC.

363

 The SCC Technical Support Document (SCC 

 

363 See U.S. EPA 2010 LD Final Rule, Note (#).
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TSD) provides a complete discussion of the methods used to develop these SCC 

estimates.364 

The interagency group selected four SCC values for use in regulatory analyses, 

which we have applied in this analysis: $5, $22, $36, and $67 per metric ton of CO2 

emissions in 2010, in 2008 dollars.365,366 The first three values are based on the average 

SCC from three integrated assessment models, at discount rates of 2.5, 3, and 5 percent, 

respectively. SCCs at several discount rates are included because the literature shows 

that the SCC is quite sensitive to assumptions about the discount rate, and because no 

consensus exists on the appropriate rate to use in an intergenerational context. The fourth 

value is the 95th percentile of the SCC from all three models at a 3 percent discount rate. 

It is included to represent higher-than-expected impacts from temperature change further 

out in the tails of the SCC distribution. Low probability, high impact events are 

incorporated into all of the SCC values through explicit consideration of their effects in 

two of the three models as well as the use of a probability density function for 

equilibrium climate sensitivity. Treating climate sensitivity probabilistically results in 

more high temperature outcomes, which in turn lead to higher projections of damages.

The SCC increases over time because future emissions are expected to produce 

larger incremental damages as physical and economic systems become more stressed in 

response to greater climatic change. Note that the interagency group estimated the 

growth rate of the SCC directly using the three integrated assessment models rather than 

assuming a constant annual growth rate. This helps to ensure that the estimates are 

internally consistent with other modeling assumptions. Table VIII-11 presents the SCC 

estimates used in this analysis.

When attempting to assess the incremental economic impacts of carbon dioxide 

emissions, the analyst faces a number of serious challenges. A recent report from the 

National Academies of Science points out that any assessment will suffer from 

uncertainty, speculation, and lack of information about (1) future emissions of 

greenhouse gases, (2) the effects of past and future emissions on the climate system, (3) 

 

364 Docket ID EPA-HQ-OAR-2009-0472-114577, Technical Support Document: Social Cost of Carbon for 

Regulatory Impact Analysis Under Executive Order 12866, Interagency Working Group on Social Cost of 

Carbon, with participation by Council of Economic Advisers, Council on Environmental Quality, 

Department of Agriculture, Department of Commerce, Department of Energy, Department of 

Transportation, Environmental Protection Agency, National Economic Council, Office of Energy and 

Climate Change, Office of Management and Budget, Office of Science and Technology Policy, and 

Department of Treasury (February 2010). Also available at http://epa.gov/otaq/climate/regulations.htm

365 The interagency group decided that these estimates apply only to CO2 emissions. Given that warming 

profiles and impacts other than temperature change (e.g. ocean acidification) vary across GHGs, the group 

concluded “transforming gases into CO2-equivalents using GWP, and then multiplying the carbonequivalents by the SCC, would not result in accurate estimates of the social costs of non-CO2 gases” (SCC 

TSD, pg 13).

366 The SCC estimates were converted from 2007 dollars to 2008 dollars using a GDP price deflator (1.021) 

obtained from the Bureau of Economic Analysis, National Income and Product Accounts Table 1.1.4, 

Prices Indexes for Gross Domestic Product.
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the impact of changes in climate on the physical and biological environment, and (4) the 

translation of these environmental impacts into economic damages.367 As a result, any

effort to quantify and monetize the harms associated with climate change will raise 

serious questions of science, economics, and ethics and should be viewed as provisional. 

The interagency group noted a number of limitations to the SCC analysis, 

including the incomplete way in which the integrated assessment models capture 

catastrophic and non-catastrophic impacts, their incomplete treatment of adaptation and 

technological change, uncertainty in the extrapolation of damages to high temperatures, 

and assumptions regarding risk aversion. The limited amount of research linking climate 

impacts to economic damages makes the interagency modeling exercise even more 

difficult. The interagency group hopes that over time researchers and modelers will work 

to fill these gaps and that the SCC estimates used for regulatory analysis by the Federal 

government will continue to evolve with improvements in modeling. Additional details 

on these limitations are discussed in the SCC TSD.

In light of these limitations, the interagency group has committed to updating the 

current estimates as the science and economic understanding of climate change and its 

impacts on society improves over time. Specifically, the interagency group has set a 

preliminary goal of revisiting the SCC values in the next few years or at such time as 

substantially updated models become available, and to continue to support research in 

this area. 

Applying the global SCC estimates, shown in Table VIII-11, to the estimated 

domestic reductions in CO2 emissions under this proposed rule, we estimate the dollar 

value of the climate related benefits for each analysis year. For internal consistency, the 

annual benefits are discounted back to net present value terms using the same discount 

rate as each SCC estimate (i.e. 5%, 3%, and 2.5%) rather than 3% and 7%.368 These 

estimates are provided in Table VIII-12.

 

367

 Cite NRC 2009

368 It is possible that other benefits or costs of proposed regulations unrelated to CO2 emissions will be 

discounted at rates that differ from those used to develop the SCC estimates.
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Table VIII-11: Social Cost of CO2, 2010 – 2050a(in 2008 dollars)

Year Discount Rate and Statistic

5% Average 3% Average 2.5% Average 3% 

95th percentile

2010 $4.80 $21.85 $35.84 $66.26

2015 $5.87 $24.35 $39.21 $74.33

2020 $6.94 $26.85 $42.58 $82.39

2025 $8.45 $30.15 $46.84 $92.25

2030 $9.95 $33.44 $51.10 $102.10

2035 $11.46 $36.73 $55.36 $111.95

2040 $12.97 $40.02 $59.63 $121.81

2045 $14.50 $42.93 $63.00 $130.43

2050 $16.03 $45.84 $66.37 $139.06

a The SCC values are dollar-year and emissions-year specific.

Table VIII-12: Monetized CO2 Benefits of Vehicle Program, CO2 Emissionsa(Million 2008$)

YEAR CO2

EMISSIONS 

REDUCTION 

(Million Metric 

Tons)

BENEFITS

Avg SCC at 

5% ($5-$16)a

Avg SCC at 3% 

($22-$46)a

Avg SCC at 

2.5% ($36-

$66)a

95th percentile 

SCC at 3% 

($66-$139)a

2020 33.3 $231 $894 $1,418 $2,744

2030 64.1 $638 $2,144 $3,277 $6,548

2040 82.4 $1,068 $3,297 $4,911 $10,033

2050 97.8 $1,568 $4,486 $6,494 $13,606

Net 

Present 

Valueb

2,310 $8,100 $41,000 $69,700 $125,300

a Except for the last row (net present value), the SCC values are dollar-year and emissions-year specific.

b Net present value of reduced CO2 emissions is calculated differently from other benefits. The same 

discount rate used to discount the value of damages from future emissions (SCC at 5, 3, 2.5 percent) is used 

to calculate net present value of SCC for internal consistency. Refer to the SCC TSD for more detail.

H. Non-GHG Health and Environmental Impacts

This section discusses the non-GHG health and environmental impacts that can be 

expected to occur as a result of the proposed heavy-duty vehicle GHG rule. GHG 

emissions are predominantly the byproduct of fossil fuel combustion processes that also 

produce criteria and hazardous air pollutants. The vehicles that are subject to the 

proposed standards are also significant sources of mobile source air pollution such as 

direct PM, NOX, VOCs and air toxics. The proposed standards would affect exhaust 

emissions of these pollutants from vehicles. They would also affect emissions from 

upstream sources related to changes in fuel consumption. Changes in ambient ozone, 

PM2.5, and air toxics that would result from the proposed standards are expected to affect 
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human health in the form of premature deaths and other serious human health effects, as 

well as other important public health and welfare effects. 

It is important to quantify the health and environmental impacts associated with 

the proposed standard because a failure to adequately consider these ancillary copollutant impacts could lead to an incorrect assessment of their net costs and benefits. 

Moreover, co-pollutant impacts tend to accrue in the near term, while any effects from 

reduced climate change mostly accrue over a time frame of several decades or longer. 

EPA typically quantifies and monetizes the health and environmental impacts 

related to both PM and ozone in its regulatory impact analyses (RIAs), when possible. 

However, EPA was unable to do so in time for this proposal. EPA attempts to make 

emissions and air quality modeling decisions early in the analytical process so that we 

can complete the photochemical air quality modeling and use that data to inform the 

health and environmental impacts analysis. Resource and time constraints precluded the 

Agency from completing this work in time for the proposal. Instead, we provide a 

characterization of the health and environmental impacts that will be quantified and 

monetized for the final rulemaking. 

EPA bases its analyses on peer-reviewed studies of air quality and health and 

welfare effects and peer-reviewed studies of the monetary values of public health and 

welfare improvements, and is generally consistent with benefits analyses performed for 

the analysis of the final Ozone National Ambient Air Quality Standard (NAAQS) and the 

final PM NAAQS analysis, as well as the proposed Portland Cement National Emissions 

Standards for Hazardous Air Pollutants (NESHAP) RIA, and final NO2 NAAQS.369,370,

371,372

 

Though EPA is characterizing the changes in emissions associated with toxic 

pollutants, we will not be able to quantify or monetize the human health effects 

associated with air toxic pollutants for either the proposal or the final rule analyses. 

Please refer to Section VII for more information about the air toxics emissions impacts 

associated with the proposed standards.

 

369 U.S. Environmental Protection Agency. (2008). Final Ozone NAAQS Regulatory Impact Analysis. 

Prepared by: Office of Air and Radiation, Office of Air Quality Planning and Standards. March.

370 U.S. Environmental Protection Agency. October 2006. Final Regulatory Impact Analysis (RIA) for the 

Proposed National Ambient Air Quality Standards for Particulate Matter. Prepared by: Office of Air and 

Radiation. 

371 U.S. Environmental Protection Agency (U.S. EPA). 2009. Regulatory Impact Analysis: National 

Emission Standards for Hazardous Air Pollutants from the Portland Cement Manufacturing Industry. 

Office of Air Quality Planning and Standards, Research Triangle Park, NC. April. Available on the 

Internet at <http://www.epa.gov/ttn/ecas/regdata/RIAs/portlandcementria_4-20-09.pdf>. EPA-HQ-OAR2009-0472-0241

372 U.S. Environmental Protection Agency (U.S. EPA). 2010. Final NO2 NAAQS Regulatory Impact 

Analysis (RIA). Office of Air Quality Planning and Standards, Research Triangle Park, NC. April. 

Available on the Internet at http://www.epa.gov/ttn/ecas/regdata/RIAs/FinalNO2RIAfulldocument.pdf. 

Accessed March 15. EPA-HQ-OAR-2009-0472-0237
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(1) Human Health and Environmental Impacts

To model the ozone and PM air quality benefits of the final rule, EPA will use the 

Community Multiscale Air Quality (CMAQ) model (see VII.C for a description of the 

CMAQ model). The modeled ambient air quality data will serve as an input to the 

Environmental Benefits Mapping and Analysis Program (BenMAP).373 BenMAP is a 

computer program developed by EPA that integrates a number of the modeling elements 

used in previous RIAs (e.g., interpolation functions, population projections, health impact 

functions, valuation functions, analysis and pooling methods) to translate modeled air 

concentration estimates into health effects incidence estimates and monetized benefits 

estimates. 

Chapter 8.3 in the draft RIA that accompanies this proposal lists the co-pollutant 

health effect exposure-response functions EPA will use to quantify the co-pollutant 

incidence impacts associated with the final heavy-duty vehicles standard. These include 

PM- and ozone-related premature mortality, chronic bronchitis, nonfatal heart attacks, 

hospital admissions (respiratory and cardiovascular), emergency room visits, acute 

bronchitis, minor restricted activity days, and days of work and school lost.

(2) Monetized Impacts

To calculate the total monetized impacts associated with quantified health 

impacts, EPA applies values derived from a number of sources. For premature mortality, 

EPA applies a value of a statistical life (VSL) derived from the mortality valuation 

literature. For certain health impacts, such as chronic bronchitis and a number of 

respiratory-related ailments, EPA applies willingness-to-pay estimates derived from the 

valuation literature. For the remaining health impacts, EPA applies values derived from 

current cost-of-illness and/or wage estimates. Chapter 8.3 in the DRIA that accompanies 

this proposal presents the monetary values EPA will apply to changes in the incidence of 

health and welfare effects associated with the final standard. 

(3) Other Unquantified Health and Environmental Impacts

In addition to the co-pollutant health and environmental impacts EPA will 

quantify for the analysis of the final standard, there are a number of other health and 

human welfare endpoints that EPA will not be able to quantify or monetize because of 

current limitations in the methods or available data. These impacts are associated with 

emissions of air toxics (including benzene, 1,3-butadiene, formaldehyde, acetaldehyde, 

and acrolein), ambient ozone, and ambient PM2.5 exposures. Chapter 8.3 of the DRIA 

lists these unquantified health and environmental impacts.

While there will be impacts associated with air toxic pollutant emission changes 

that result from the final standard, EPA will not attempt to monetize those impacts. This 

 

373 Information on BenMAP, including downloads of the software, can be found at 

http://www.epa.gov/ttn/ecas/ benmodels.html.
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is primarily because currently available tools and methods to assess air toxics risk from 

mobile sources at the national scale are not adequate for extrapolation to incidence 

estimations or benefits assessment. The best suite of tools and methods currently

available for assessment at the national scale are those used in the National-Scale Air 

Toxics Assessment (NATA). The EPA Science Advisory Board specifically commented 

in their review of the 1996 NATA that these tools were not yet ready for use in a 

national-scale benefits analysis, because they did not consider the full distribution of 

exposure and risk, or address sub-chronic health effects.374 While EPA has since 

improved the tools, there remain critical limitations for estimating incidence and 

assessing benefits of reducing mobile source air toxics. EPA continues to work to 

address these limitations; however, EPA does not anticipate having methods and tools 

available for national-scale application in time for the analysis of the final rules.375

I. Energy Security Impacts 

This proposed rule to reduce fuel consumption and GHG emissions in heavy duty 

vehicles results in improved fuel efficiency which, in turn, helps to reduce U.S. 

petroleum imports. A reduction of U.S. petroleum imports reduces both financial and 

strategic risks caused by potential sudden disruptions in the supply of imported petroleum 

to the U.S. This reduction in risk is a measure of improved U.S. energy security. This 

section summarizes our estimates of U.S. oil import reductions and energy security 

benefits of the proposed heavy duty fuel consumption and GHG vehicle standards. 

Additional discussion of this issue can be found in Chapter 9.4 of the draft RIA.

(1) Implications of Reduced Petroleum Use on U.S. Imports

In 2008, U.S. petroleum import expenditures represented 21 percent of total U.S. 

imports of all goods and services.376 In 2008, the U.S. imported 66 percent of the

petroleum it consumed, and the transportation sector accounted for 70 percent of total 

U.S. petroleum consumption. This compares to approximately 37 percent of petroleum 

from imports and 55 percent of consumption from petroleum in the transportation sector 

 

374 Science Advisory Board. 2001. NATA – Evaluating the National-Scale Air Toxics Assessment for 

1996 – an SAB Advisory. http://www.epa.gov/ttn/atw/sab/sabrev.html.

375 In April, 2009, EPA hosted a workshop on estimating the benefits of reducing hazardous air pollutants. 

This workshop built upon the work accomplished in the June 2000 Science Advisory Board/EPA 

Workshop on the Benefits of Reductions in Exposure to Hazardous Air Pollutants, which generated 

thoughtful discussion on approaches to estimating human health benefits from reductions in air toxics 

exposure, but no consensus was reached on methods that could be implemented in the near term for a broad 

selection of air toxics. Please visit http://epa.gov/air/toxicair/2009workshop.html for more information 

about the workshop and its associated materials.

376 Source: U.S. Bureau of Economic Analysis, U.S. International Transactions Accounts Data, as shown on 

June 24, 2009.
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in 1975.377 It is clear that petroleum imports have a significant impact on the U.S. 

economy. 

Requiring lower-GHG vehicle technology in heavy-duty vehicles in the U.S. is 

expected to lower U.S. oil imports. EPA used the MOVES model to estimate the fuel

savings due to this proposal. A detailed explanation of the MOVES model can be found 

in Chapter 5 of the draft RIA. 

Based on a detailed analysis of differences in fuel consumption, petroleum 

imports, and imports of refined petroleum products and crude oil among the Reference 

Case, High Economic Growth, and Low Economic Growth Scenarios presented in the 

Energy Information Administration’s Annual Energy Outlook (AEO) 2009, EPA and 

NHTSA estimate that approximately 50 percent of the reduction in fuel consumption 

resulting from adopting improved fuel GHG standards and fuel economy standards is 

likely to be reflected in reduced U.S. imports of refined fuel, while the remaining 50 

percent would be expected to be reflected in reduced domestic fuel refining. Of this latter 

figure, 90 percent is anticipated to reduce U.S. imports of crude petroleum for use as a 

refinery feedstock, while the remaining 10 percent is expected to reduce U.S. domestic 

production of crude petroleum. Thus, on balance, each gallon of fuel saved as a 

consequence of the heavy duty GHG standards and fuel economy standards is anticipated 

to reduce total U.S. imports of crude petroleum or refined fuel by 0.95 gallons.378 EPA’s 

estimates that the reduction in U.S. oil imports from this proposal for the years 2020, 

2030 and 2040, in millions of barrels per day (MMBD), are presented in Table VIII-13

below. 

Table VIII-13: U.S. Oil Import Reductions from the Heavy-Duty Vehicle Rule in 2020, 2030 and 2040 

(in MMBD)

2020 2030 2040

0.177 0.357 0.463

(2) Energy Security Implications

In order to understand the energy security implications of reducing U.S. 

petroleum imports, EPA worked with Oak Ridge National Laboratory (ORNL), which 

has developed approaches for evaluating the economic costs and energy security

implications of oil use. The energy security estimates provided below are based upon a 

methodology developed in a peer-reviewed study entitled "The Energy Security Benefits 

 

377 Source: U.S. Department of Energy, Annual Energy Review 2008, Report No. DOE/EIA-0384(2008), 

Tables 5.1 and 5.13c, June 26, 2009.

378 This figure is calculated as 0.50 + 0.50*0.9 = 0.50 + 0.45 = 0.95.
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of Reduced Oil Use, 2006-2015," completed in March 2008. This study is included as 

part of the docket for this proposal.

379,380

When conducting this analysis, ORNL considered the full economic cost of 

importing petroleum into the U.S. The economic cost of importing petroleum into the 

U.S. is defined to include two components in addition to the purchase price of petroleum 

itself. These are: (1) the higher costs for oil imports resulting from the effect of 

increasing U.S. import demand on the world oil price and on OPEC market power (i.e., 

the "demand" or "monopsony" costs); and (2) the risk of reductions in U.S. economic 

output and disruption of the U.S. economy caused by sudden disruptions in the supply of 

imported petroleum to the U.S. (i.e., macroeconomic disruption/adjustment costs). 

Maintaining a U.S. military presence to help secure stable oil supply from potentially

vulnerable regions of the world was not included in this analysis because its attribution to 

particular missions or activities is hard to quantify. 

As part of the process for developing the ORNL energy security estimates, EPA 

sponsored an independent, expert peer review of the 2008 ORNL study. A report 

compiling the peer reviewers’ comments is provided in the docket.381 In addition, EPA 

has worked with ORNL to address comments raised in the peer review and to develop 

estimates of the energy security benefits associated with a reduction in U.S. oil imports 

for this heavy duty vehicle rule. In response to peer reviewer comments, ORNL modified 

its model by changing several key parameters involving OPEC supply behavior, the 

responsiveness of oil demand and supply to a change in the world oil price, and the 

responsiveness of U.S. economic output to a change in the world oil price.

For this proposed rule, ORNL estimated energy security premiums by

incorporating the most recent available AEO 2010 oil price forecasts and market trends. 

Energy security premiums for the years 2020, 2030 and 2040 are presented in Table 

VIII-14 ,

382 as well as a breakdown of the components of the energy security premium for 

each of these years. The components of the energy security premiums and their values 

are discussed in detail in Chapter 9.4 of the RIA.

 

379 Leiby, Paul N., "Estimating the Energy Security Benefits of Reduced U.S. Oil Imports" Oak Ridge 

National Laboratory, ORNL/TM-2007/028, Final Report, 2008. (Docket EPA-HQ-OAR-2010-0162)

380 The ORNL study “The Energy Security Benefits of Reduced Oil Use, 2006-2015," completed in March

2008, is an update version of the approach used for estimating the energy security benefits of U.S. oil 

import reductions developed in an ORNL 1997 Report by Leiby, Paul N., Donald W. Jones, T. Randall 

Curlee, and Russell Lee, entitled “Oil Imports: An Assessment of Benefits and Costs." (Docket EPA-HQOAR-2010-0162)

381 Peer Review Report Summary: Estimating the Energy Security Benefits of Reduced U.S. Oil Imports, 

ICF, Inc., September 2007.

382 AEO 2009 forecasts energy market trends and values only to 2035. The energy security premium 

estimates post-2035 were assumed to be the 2035 estimate.
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Table VIII-14: Energy Security Premiums in 2020, 2030 and 2040 (2008$/Barrel)

Year

(range)

Monopsony Macroeconomic 

Disruption/Adjustment Costs

Total Mid-Point

2020 $12.28

($4.16 - $23.74)

$7.39

($3.39 – $11.92)

$19.66

($10.27 - $30.90)

2030 $12.69

($4.43 – 23.80)

$8.54

($4.10 – $13.60)

$21.23

($11.30 - $32.88)

2040 $12.68

($4.41 – $23.41)

$8.99

($4.48 - $14.08)

$21.67

($11.54 - $33.11)

The literature on the energy security for the last two decades has routinely 

combined the monopsony and the macroeconomic disruption components when 

calculating the total value of the energy security premium. However, in the context of 

using a global value for the Social Cost of Carbon (SCC), the question arises: how should 

the energy security premium be determined when a global perspective is taken? 

Monopsony benefits represent avoided payments by the U.S. to oil producers in foreign 

countries that result from a decrease in the world oil price as the U.S. decreases its 

consumption of imported oil. 

Although there is clearly a benefit to the U.S. when considered from a domestic 

perspective, the decrease in price due to decreased demand in the U.S. also represents a 

loss to other countries. Given the redistributive nature of this monopsony effect from a 

global perspective, it is excluded in the energy security benefits calculations for this 

proposal. In contrast, the other portion of the energy security premium, the U.S. 

macroeconomic disruption and adjustment costs that arise from U.S. petroleum imports, 

does not have offsetting impacts outside of the U.S., and, thus, are included in the energy

security benefits estimated for this proposal. To summarize, the agencies have included 

only the macroeconomic disruption portion of the energy security benefits to monetize 

the total energy security benefits of this proposal. 

The total annual energy security benefits for the proposed heavy duty vehicle rule 

are reported in Table VIII-15 for the years 2020, 2030 and 2040. These estimates include

only the macroeconomic disruption/adjustment portion of the energy security premium. 

Table VIII-15: Total Annual Energy Security Benefits from the Heavy-Duty Vehicle Rule in 2020, 

2030 and 2040 (millions of 2008$)

Year Benefits

2020 $477

2030 $1,113

2040 $1,520
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J. Other Impacts

(1) Noise, Congestion and Accidents

Increased vehicle use associated with a positive rebound effect also contributes to 

increased traffic congestion, motor vehicle accidents, and highway noise. Depending on 

how the additional travel is distributed over the day and on where it takes place, 

additional vehicle use can contribute to traffic congestion and delays by increasing traffic 

volumes on facilities that are already heavily traveled during peak periods. These added 

delays impose higher costs on drivers and other vehicle occupants in the form of 

increased travel time and operating expenses, increased costs associated with traffic 

accidents, and increased traffic noise. Because drivers do not take these added costs into 

account in deciding when and where to travel, they must be accounted for separately as a 

cost of the added driving associated with the rebound effect.

EPA and NHTSA rely on estimates of congestion, accident, and noise costs 

caused by pickup trucks and vans, single unit trucks, buses, and combination trucks

developed by the Federal Highway Administration to estimate the increased external 

costs caused by added driving due to the rebound effect.383 The FHWA estimates are 

intended to measure the increases in costs from added congestion, property damages and 

injuries in traffic accidents, and noise levels caused by automobiles and light trucks that 

are borne by persons other than their drivers (or “marginal” external costs). EPA and 

NHTSA employed estimates from this source previously in the analysis accompanying 

the Light Duty GHG final rule. The agencies continue to find them appropriate for this 

analysis after reviewing the procedures used by FHWA to develop them and considering 

other available estimates of these values. FHWA’s congestion estimates for trucks 

already consider that trucks account for a lower percent of peak period traffic on 

congested freeways because they try to avoid peak periods when possible. The FHWA 

congestion costs are a weighted average based on the estimated percent of peak and offpeak freeway travel for each of the classes of trucks. FHWA focused congestion costs on 

freeways because non-freeway effects are less serious because of lower traffic volumes 

and opportunities to re-route around the congestion. The agencies, however, applied the 

congestion cost to the overall VMT increase, though the fraction of VMT on each road 

type used in MOVES range from 27 to 29 percent of the vehicle miles on freeways for 

vocational trucks and 53 percent for combination trucks. The results of this analysis 

potentially overestimate the costs and provide a conservative estimate. The agencies 

welcome comments on whether the cost calculations should be done differently in the 

final rulemaking.

The agencies are proposing to use FHWA’s “Middle” estimates for marginal 

congestion, accident, and noise costs caused by increased travel from trucks. This 

approach is consistent with the current methodology used in the Light Duty GHG 

 

383 These estimates were developed by FHWA for use in its 1997 Federal Highway Cost Allocation Study; 

see http://www.fhwa.dot.gov/policy/hcas/final/index.htm (last accessed July 21, 2010).
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rulemaking analysis. These costs are multiplied by the annual increases in vehicle miles 

travelled from the positive rebound effect to yield the estimated increases in congestion, 

accident, and noise externality costs during each future year. The values the agencies 

used in the calculation of the congestion, noise, and accident costs are included in Table 

VIII-16.

Table VIII-16 Noise, Accident, and Congestion Costs per Mile (2008$)

External Costs Pickup truck and 

vans ($/VMT)

Vocational trucks 

($/VMT)

Combination 

trucks ($/VMT)

Congestion $ 0.049 $ 0.110 $ 0.107

Accidents $ 0.026 $ 0.019 $ 0.022

Noise $ 0.001 $ 0.009 $ 0.020

In aggregate, the external costs due to noise, accidents, and congestion from the 

additional truck driving are presented in Table VIII-17.

Table VIII-17 Accident, Noise, and Congestion Costs (Millions, 2008$)

Year Class 2b&3 Vocational Combination EXTERNAL COSTS

2012 $0 $0 $0 $0

2013 $0 $0 $0 $0

2014 $8 $10 $18 $36

2015 $16 $19 $35 $70

2016 $23 $30 $52 $104

2017 $30 $39 $68 $137

2018 $37 $48 $83 $168

2020 $50 $64 $111 $225

2030 $89 $122 $193 $404

2040 $112 $182 $233 $527

2050 $133 $245 $271 $648

NPV, 3% $1,606 $2,407 $3,439 $7,452

NPV, 7% $746 $1,070 $1,614 $3,429

(2) Savings due to reduced refueling time

Reducing the fuel consumption of heavy duty trucks may either increase their 

driving range before they require refueling, or motivate truck purchasers to buy, and 

manufacturers to offer, smaller fuel tanks. Keeping the fuel tank the same size allows 

truck operators to reduce the frequency with which drivers typically refuel their vehicles; 

it thus extends the upper limit of the range they can travel before requiring refueling. 

Alternatively, if purchasers and manufacturers respond to improved fuel economy by
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reducing the size of fuel tanks to maintain a constant driving range, the smaller tank will 

require less time in actual refueling. 

Because refueling time represents a time cost of truck operation, these time 

savings should be incorporated into truck purchasers’ decisions over how much fuelsaving technology they want in their vehicles. The savings calculated here thus raise the 

same questions discussed in Preamble VIII.A and DRIA Section 9.1: does the apparent 

existence of these savings reflect failures in the market for fuel economy, or does it 

reflect costs not addressed in this analysis? The response to these questions could vary

across truck segment. See those sections for further analysis of this question.

This analysis estimates the reduction in the annual time spent filling the fuel tank; 

this reduced time could come either from fewer refueling events, if the fuel tank stays the 

same size, or less time spent refueling, if the fuel tank is made proportionately smaller.

The fuel savings are calculated as the time not spent putting fuel into the vehicle, based 

on the amount of time that would have been necessary to pump the fuel. The calculation 

does not include time spent searching for a fuel station or other time spent at the station; 

it is assumed that the time savings occur when truck operators would otherwise be 

refueling. It includes additional mileage associated with the rebound effect.

The details of this calculation are discussed in the draft RIA Chapter 9.3.2. The 

savings per vehicle through its lifetime are listed in Table VIII-18.

Table VIII-18: Aggregate Refueling Savings (2008$)

Pickup trucks and 

vans

vocational trucks tractors

3% Discount 

Rate

$64 $220 $294

7% Discount 

Rate

$50 $176 $235

The aggregate savings of the vehicles sold in 2014 through 2050 are listed in 

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Table VIII-19 Estimated Savings due to Less Frequent Refueling (Millions of 2008 dollars) 

Year Class 2b&3 Vocational Combination 

Truck/Tractor

Total

2012 $0.0 $0.0 $0.0 $0.0

2013 $0.0 $0.0 $0.0 $0.0

2014 $0.3 $1.8 $4.9 $6.9

2015 $0.6 $3.4 $9.6 $13.6

2016 $1.6 $5.2 $14.1 $21.0

2017 $3.2 $8.5 $20.6 $32.3

2018 $6.0 $11.7 $26.8 $44.5

2020 $11.3 $17.3 $38.4 $67.0

2030 $30.3 $37.4 $72.5 $140.2

2040 $41.0 $57.4 $88.7 $187.1

2050 $49.5 $77.5 $103.1 $230.0

NPV, 3% $521 $728 $1,267 $2,516

NPV, 7% $225 $315 $584 $1,123

(3) The Effect of Safety Standards and Voluntary Safety Improvements on 

Vehicle Weight

Safety regulations developed by NHTSA in previous regulations may make 

compliance with the proposed standards more difficult or may reduce the projected 

benefits of the program. The primary way that safety regulations can impact fuel 

efficiency and GHG emissions is through increased vehicle weight, which reduces the 

fuel efficiency of the vehicle. Using MY 2010 as a baseline, this section discusses the 

effects of other government regulations on model year (MY) 2014-2016 medium and 

heavy duty vehicle fuel efficiency. At this time, no known safety standards will affect 

new models in MY 2017 or 2018. The agency’s estimates are based on cost and weight 

tear-down studies of a few vehicles and cannot possibly cover all the variations in the 

manufacturers’ fleets. NHTSA requested, and various manufacturers provided, 

confidential estimates of increases in weight resulting from safety improvements. Those 

increases are shown in subsequent tables. 

We have broken down our analysis of the impact of safety standards that might 

affect the MY 2014-16 fleets into three parts: 1) those NHTSA final rules with known 

effective dates, 2) proposed rules or soon to be proposed rules by NHTSA with or 

without final effective dates, and 3) currently voluntary safety improvements planned by

the manufacturers. 

(a) Weight Impacts of Required Safety Standards 

NHTSA has undertaken several rulemakings in which several standards would 

become effective for medium and heavy duty (MD/HD) vehicles between MY 2014 and 
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MY 2016. We will examine the potential impact on MD/HD vehicle weights for MY 

2014-2016 using MY 2010 as a baseline. 

 FMVSS 119, Heavy Truck Tires Endurance and High Speed Tests

 FMVSS 121, Air Brake Systems Stopping Distance 

 FMVSS 214, Motor Coach Lap/Shoulder Belts

 MD/HD Vehicle Electronic Stability Control Systems

(i) FMVSS 119, Heavy Truck Tires Endurance and High Speed Tests

The data in the large truck crash causation study (LTCCS) and the agency’s test 

results indicate that J and L load range tires are more likely to fail the proposed 

requirements among the targeted F, G, H, J and L load range tires.384 As such the J and 

L load range tires specifically need to be addressed to meet the proposed requirements 

since the other load range tires are likely to pass the requirements. Rubber material 

improvements such as improving rubber compounds would be a countermeasure that 

reduces heat retention and improve the durability of the tires. Using high tensile strength 

steel chords in tire bead, carcass and belt would enable a weight reduction in construction 

with no strength penalties. The rubber material improvements and using high tensile 

strength steel would not add any additional weight to the current production heavy truck 

tires. Thus there may not be an incremental weight per vehicle for the period of MY 

2014-2016 compared to the MY 2010 baseline. This proposal could become a final rule 

with an effective date of MY2016. 

(ii) FMVSS No. 121, Airbrake Systems Stopping Distance

The most recent major final rule was published on July 27, 2009 and became 

effective on November 24, 2009 (MY2009) with different compliance dates. The final 

rule requires the vast majority of new heavy truck tractors (approximately 99 percent of 

the fleet) to achieve a 30 percent reduction in stopping distance compared to currently 

required levels. Three-axel tractors with a gross vehicle weight rating (GVWR) of 

59,600 pounds or less must meet the reduced stopping distance requirements by August 

1, 2011 (MY2011). Two-axle tractors and tractors with a GVWR above 59,600 pounds 

must meet the reduced stopping distance requirements by August 1, 2013 (MY2013). 

There are several brake systems that can meet the requirements in the final rule. Those 

systems include installation of larger S-cam drum brakes or disc brake systems at all 

positions, or hybrid disc and larger rear S-cam drum brake systems. 

According to the data provided by a manufacturer (Bendix), the heaviest drum 

brakes weigh more than the lightest disc brakes while the heaviest disc brakes weigh 

more than the lightest drum brakes. For a three-axle tractor equipped with all disc 

brakes, the total weight could increase by 212 pounds or could decrease by 134 pounds 

compared to an all drum braked tractor depending on which disc or drum brakes are used 

 

384 “Preliminary Regulatory Impact Analysis, FMVSS No. 119, New Pneumatic Tires for Motor Vehicles 

with a GVWR of More Than 4,536 kg (10,000 pounds), June 2010.
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for comparison. The improved brakes may add a small amount of weight to the affected 

vehicle for MY2014-2016 resulting in a slight increase in fuel consumption. 

(iii) FMVSS No. 208, Motor coach Lap/Shoulder Belts

Based on preliminary results from the agency’s cost/weight teardown studies of 

motor coach seats, it is estimated that the weight added by 3-point lap/shoulder belts 

ranges from 5.96 to 9.95 pounds per 2-person seat.385 This is the weight only of the seat 

belt assembly itself and does not include changing the design of the seat, reinforcing the 

floor, walls or other areas of the motor coach. Few current production motor coaches 

have been installed with lap/shoulder belts on their seats, and the number could be 

negligible. Assuming a 54 passenger motor coach, the added weight for the 3-point 

lap/shoulder belt assembly is in the range of 161 to 269 pounds (27 * (5.96 to 9.95)) per 

vehicle. This proposal could become a final rule with an effective date of MY2016. 

(iv) Electronic Stability Control Systems (ESC) for Medium and Heavy Duty 

(MD/HD) Vehicles

The ESC is not currently required in MD/HD vehicles and could be proposed to 

be required in the vehicles by NHTSA. FMVSS No. 105, Hydraulic and electric brake 

systems, requires multipurpose passenger vehicles, trucks and buses with a GVWR 

greater than 4,536 kg (10,000 pounds) to be equipped with an antilock brake system 

(ABS). All MD/HD vehicles have a GVWR of more than 10,000 pounds, and these 

vehicles are required to be installed with an ABS by the same standard.

The ESC incorporates yaw rate control into the ABS, and yaw is a rotation around 

the vertical axis. The ESC system uses several sensors in addition to the sensors used in 

the ABS, which is required in MD/HD vehicles. Those additional sensors could include 

steering wheel angle sensor, yaw rate sensor, lateral acceleration sensor and wheel speed 

sensor. According to the data provided by Meritor WABCO, the weight of the ESC for 

the model 4S4M tractor is estimated to be around 55.494 pounds, and the weight of the 

ABS only is estimated to be 45.54 pounds. Then the added weight for the ESC for the 

vehicle is estimated to be 9.954 (55.494 – 45.54) pounds. 

(b) Summary – Overview of Anticipated Weight Increases

Table 1 summarizes estimates made by the agency regarding the weight added by 

the above discussed standards or likely rulemakings. The agency estimates that weight 

additions required by final rules and likely NHTSA regulations effective in MY 2016 

compared to the MY 2010 fleet will increase motorcoach vehicle weight by 171-279 

pounds and will increase other heavy duty truck weights by a minor 10 pounds. 

 

385 Cost and Weight Analysis of Two Motorcoach Seating Systems: One With and One Without ThreePoint Lap/Shoulder Belt Restraints, Ludkes and Associates, July 2010.
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Table VIII-20: : Weight Additions Due to Final Rules or Likely NHTSA Regulations Comparing MY 

2016 to the MY 2010 Baseline Fleet

Standard Number

Added Weight in 

pounds

MD/HD Vehicle

Added Weight in 

kilograms

MD/HD Vehicle

119 0 0

121 0 (?) 0 (?)

208

Motorcoaches only

161-269 73-122

MD/HD Vehicle Electronic 

Stability Control Systems

10 4.5

Total Motorcoaches 171- 279 77.5-126.5

Total All other MD/HD 

vehicles

10 4.5

(4) Effects of Vehicle Mass Reduction on Safety

NHTSA and EPA have been considering the effect of vehicle weight on vehicle 

safety for the past several years in the context of our joint rulemaking for light duty 

vehicle CAFE and GHG standards, consistent with NHTSA’s long-standing 

consideration of safety effects in setting CAFE standards. Combining all modes of 

impact, the latest analysis by NHTSA for the MYs 2012-2016 final rule found that 

reducing the weight of the heavier light trucks (LT > 3,870) had a positive overall effect 

on safety, reducing societal fatalities.386 

In the context of the current rulemaking for HD fuel consumption and GHG 

standards, one would expect that reducing the weight of medium-duty trucks similarly

would, if anything, have a positive impact on safety. However, given the large difference 

in weight between light-duty vehicles and medium-duty trucks, and even larger 

difference between light-duty vehicles and heavy-duty vehicles with loads, the agencies 

believe that the impact of weight reductions of medium- and heavy-duty trucks would not 

have a noticeable impact on safety for any of these classes of vehicles.

However, the agencies recognize that it is important to conduct further study and 

research into the interaction of mass, size and safety to assist future rulemakings, and we 

expect that the collaborative interagency work currently on-going to address this issue for 

the light-duty vehicle context may also be able to inform our evaluation of safety effects 

for the final HD vehicle rule. We seek comment regarding potential safety effects due to 

 

386 “Final Regulatory Impact Analysis, Corporate Average Fuel Economy for MY 2012 - MY 2016 

Passenger Cars and Light Trucks”, NHTSA, March 2010, (Docket No. NHTSA-2009-0059-0344.1).
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weight reduction in the HD vehicle context, with particular emphasis on commenters 

providing supporting data and research for HD vehicle weight reduction. 

K. Summary of Costs and Benefits

In this section, EPA presents a summary of costs, benefits, and net benefits of the 

proposal. 

Table VIII-21 shows the estimated annual monetized costs of the proposed program for 

the indicated calendar years. The table also shows the net present values of those costs 

for the calendar years 2012-2050 using both a 3 percent and a 7 percent discount rate. 387 

In this table, fuel savings are calculated using pre-tax fuel prices. 

Table VIII-21: Estimated Monetized Costs of the Proposed Program (Millions of 2008 dollars)a

2020 2030 2040 2050

NPV, Years

2012-2050, 

3% Discount

Rate

NPV, Yeaers

2012-2050, 

7% Discount

RateE

Technology

Costs

$2,100 $2,000 $2,300 $2,600 $43,800 $23,500

Fuel Savings 

(pre-tax)

-

$8,000

-

$18,900

-

$28,000

-

$35,200

-$351,100 -$152,100

Monetized 

Annual Costs

-

$5,900

-

$16,900

-

$25,700

-

$32,600

-$307,300 -$128,600

a Technology costs and fuel savings for separate truck segments can be found in Section 8.3.

Table VIII-22 presents estimated annual monetized benefits for the indicated 

calendar years. The table also shows the net present values of those benefits for the 

calendar years 2012-2050 using both a 3 percent and a 7 percent discount rate. Note that 

fuel savings shown here result from fleet-wide reductions in fuel use. Thus they grow 

over time, as an increasing fraction of the fleet meets the 2018 standards. The table also 

shows the benefits of reduced CO2 emissions—and consequently the annual quantified 

benefits (i.e., total benefits)—for each of four SCC values considered by EPA. As 

discussed in the RIA Section 8.5, there are some limitations to the SCC analysis, 

including the incomplete way in which the integrated assessment models capture 

catastrophic and non-catastrophic impacts, their incomplete treatment of adaptation and 

technological change, uncertainty in the extrapolation of damages to high temperatures, 

and assumptions regarding risk aversion. 

 

387 For the estimation of the stream of costs and benefits, we assume that after implementation of the 

proposed MY 2014-2017 standards, the 2017 standards apply to each year out to 2050.
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In addition, these monetized GHG benefits exclude the value of net reductions in 

non-CO2 GHG emissions (CH4, N2O) expected under this proposal. Although EPA has 

not monetized the benefits of reductions in non-CO2 GHGs, the value of these reductions 

should not be interpreted as zero. Rather, the net reductions in non-CO2 GHGs will 

contribute to this proposal’s climate benefits, as explained in Section VI.C 

Table VIII-22: Monetized Benefits Associated with the Proposed Program (Millions of 2008 dollars)

2020 2030 2040 2050

NPV, Years

2012-2050, 

3% Discount

Ratea

NPV, Yeaers

2012-2050, 

7% Discount

RateaE

Reduced CO2 Emissions at each assumed SCC value b

5% (avg SCC) $200 $700 $1,200 $1,800 $8,900 $8,900

3% (avg SCC) $900 $2,400 $3,700 $5,100 $45,300 $45,300

2.5% (avg 

SCC)

$1,500 $3,600 $5,500 $7,400 $76,800 $76,800

3% (95th 

percentile)

$2,900 $7,200 $11,200 $15,400 $138,100 $138,100

Energy

Security

Impacts (price 

shock)

$500 $1,100 $1,500 $1,800 $19,800 $8,700

Accidents, 

Congestion, 

Noise

-$200 -$400 -$500 -$600 -$7,500 -$3,400

Refueling 

Savings

$100 $100 $200 $200 $2,500 $1,100

Non-CO2 GHG 

Impacts and 

Non-GHG Impacts 

c,d

n/a n/a n/a n/a n/a n/a

Total Annual Benefits at each assumed SCC value b

5% (avg SCC) $600 $1,500 $2,400 $3,200 $23,700 $15,300

3% (avg SCC) $1,300 $3,200 $4,900 $6,500 $60,100 $51,700

2.5% (avg 

SCC)

$1,900 $4,400 $6,700 $8,800 $91,600 $83,200

3% (95th 

percentile)

$3,300 $8,000 $12,400 $16,800 $152,900 $144,500

Notes:

a Note that net present value of reduced CO2 emissions is calculated differently than other benefits. The 

same discount rate used to discount the value of damages from future emissions (SCC at 5, 3, 2.5 percent) 

is used to calculate net present value of SCC for internal consistency. Refer to the SCC TSD for more 

detail. 

b

Section VIII.G notes that SCC increases over time. Corresponding to the years in this table, the SCC 

estimates range as follows: for Average SCC at 5%: $5-$16; for Average SCC at 3%: $22-$46; for 

Average SCC at 2.5%: $36-$66; and for 95th percentile SCC at 3%: $66-$139. Section VIII.F also 

presents these SCC estimates.
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c The monetized GHG benefits presented in this analysis exclude the value of changes in non-CO2 GHG 

emissions expected under this proposal (see RIA Chapter 5). Although EPA has not monetized changes in 

non-CO2 GHGs, the value of any increases or reductions should not be interpreted as zero. d Non-GHGrelated health and welfare impacts (related to PM2.5 and ozone exposure) were not estimated for this 

proposal, but will be included in the analysis of the final rulemaking. 

Table VIII-23 presents estimated annual net benefits for the indicated calendar 

years. The table also shows the net present values of those net benefits for the calendar 

years 2012-2050 using both a 3 percent and a 7 percent discount rate. The table includes 

the benefits of reduced CO2 emissions (and consequently the annual net benefits) for each 

of four SCC values considered by EPA. 

Table 

VIII-23: 

Monetized

Net 

Benefits 

Associated 

with the 

Proposed 

Program 

(Millions 

of 2008 

dollars)

2020 2030 2040 2050 NPV, 3%a NPV, 7%a

Total Annual Costsb

Total 

Annual 

Costs

-$5,900 -$16,900 -$25,700 -$32,600 -$307,300 -$128,600

Total Annual Benefits at each assumed SCC value c

5% (avg 

SCC)

$600 $1,500 $2,400 $3,200 $23,700 $15,300

3% (avg 

SCC)

$1,300 $3,200 $4,900 $6,500 $60,100 $51,700

2.5% (avg 

SCC)

$1,900 $4,400 $6,700 $8,800 $91,600 $83,200

3% (95th 

percentile)

$3,300 $8,000 $12,400 $16,800 $152,900 $144,500

Monetized Net Benefits at each assumed SCC value c

5% (avg 

SCC)

$6,500 $18,400 $28,100 $35,800 $331,000 $143,900

3% (avg 

SCC)

$7,200 $20,100 $30,600 $39,100 $367,400 $180,300

2.5% (avg 

SCC)

$7,800 $21,300 $32,400 $41,400 $398,900 $211,800

3% (95th 

percentile)

$9,200 $24,900 $38,100 $49,400 $460,200 $273,100

Notes: 
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a Net present value of reduced CO2 emissions is calculated differently than other benefits. The same 

discount rate used to discount the value of damages from future emissions (SCC at 5, 3, 2.5 percent) is used 

to calculate net present value of SCC for internal consistency. Refer to the SCC TSD for more detail.

b Negative costs represent savings.

c

Section VIII.G notes that SCC increases over time. Corresponding to the years in this table, the SCC 

estimates range as follows: for Average SCC at 5%: $5-$16; for Average SCC at 3%: $22-$46; for 

Average SCC at 2.5%: $36-$66; and for 95th percentile SCC at 3%: $66-$139. Section VIII.G also 

presents these SCC estimates.

EPA also conducted a separate analysis of the total benefits over the model year lifetimes 

of the 2014 through 2018 model year trucks. In contrast to the calendar year analysis 

presented in 

Table VIII-21 through Table VIII-23, the model year lifetime analysis shows the lifetime 

impacts of the program on each of these MY fleets over the course of their lifetime. Full 

details of the inputs to this analysis can be found in RIA Chapter 5 of the RIA. The net 

societal benefits of the full life of each of the five model years from 2014 through 2018

are shown in Table VIII-24 and Table VIII-25 at both a 3 percent and a 7 percent 

discount rate, respectively. Note that Table VIII-24 and Table VIII-25 include the 

benefits of reduced CO2 emissions—and consequently the total benefits—for each of four 

SCC values considered by EPA.

Table VIII-24: Monetized Costs, Benefits, and Net Benefits Associated with the Lifetimes of 2014-

2018 Model Year Trucks (Millions of 2008 dollars; 3% Discount Rate)

2014MY 2015MY 2016MY 2017MY 2018MY Sum

Technology -$1,400 -$1,400 -$1,600 -$1,700 -$2,100 -$8,200

Fuel 

Savings 

(pre-tax)

$6,100 $6,400 $7,200 $10,700 $11,800 $42,200

Energy

Security

Impacts 

(price 

shock)

$400 $400 $400 $600 $700 $2,500

Accidents, 

Congestion, 

Noise

-$300 -$300 -$300 -$300 -$300 -$1,400

Refueling 

Savings

$200 $200 $200 $200 $200 $1,100

Non-CO2

GHG 

Impacts 

and 

Non-GHG 

Impacts c,d

n/a n/a n/a n/a n/a n/a

Reduced CO2 Emissions at each assumed SCC value a, b
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5% (avg 

SCC)

$200 $200 $200 $300 $300 $1,200

3% (avg 

SCC)

$600 $700 $700 $1,100 $1,200 $4,300

2.5% (avg 

SCC)

$1,000 $1,000 $1,100 $1,700 $1,800 $6,600

3% (95th 

percentile)

$1,900 $2,000 $2,200 $3,200 $3,600 $12,900

Monetized Net Benefits at each assumed SCC value a, b

5% (avg 

SCC)

$5,200 $5,500 $6,100 $9,800 $10,600 $37,400

3% (avg 

SCC)

$5,600 $6,000 $6,600 $10,600 $11,500 $40,500

2.5% (avg 

SCC)

$6,000 $6,300 $7,000 $11,200 $12,100 $42,800

3% (95th 

percentile)

$6,900 $7,300 $8,100 $12,700 $13,900 $49,100

Notes: 

a Net present value of reduced CO2 emissions is calculated differently than other benefits. The same 

discount rate used to discount the value of damages from future emissions (SCC at 5, 3, 2.5 percent) is used 

to calculate net present value of SCC for internal consistency. Refer to the SCC TSD for more detail. 

b

Section VIII.G notes that SCC increases over time. Corresponding to the years in this table, the SCC 

estimates range as follows: for Average SCC at 5%: $5-$16; for Average SCC at 3%: $22-$46; for 

Average SCC at 2.5%: $36-$66; and for 95th percentile SCC at 3%: $66-$139. Section VIII.G also 

presents these SCC estimates.

c The monetized GHG benefits presented in this analysis exclude the value of changes in non-CO2 GHG 

emissions expected under this proposal (see RIA Chapter 5). Although EPA has not monetized changes in 

non-CO2 GHGs, the value of any increases or reductions should not be interpreted as zero. 

d Non-GHG-related health and welfare impacts (related to PM2.5 and ozone exposure) were not estimated 

for this proposal, but will be included in the analysis of the final rulemaking. 
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Table VIII-25: Monetized Costs, Benefits, and Net Benefits Associated with the Lifetimes of 2014-

2018 Model Year Trucks (Millions of 2008 dollars; 7% Discount Rate)

2014MY 2015MY 2016MY 2017MY 2018MY Sum

Technology -$1,400 -$1,400 -$1,600 -$1,700 -$2,100 -$8,200

Fuel 

Savings 

(pre-tax)

$4,500 $4,500 $4,900 $7,000 $7,400 $28,300

Energy

Security

Impacts 

(price 

shock)

$300 $300 $300 $400 $400 $1,700

Accidents, 

Congestion, 

Noise

-$200 -$200 -$200 -$200 -$200 -$900

Refueling 

Savings

$200 $200 $200 $200 $200 $900

Non-CO2

GHG 

Impacts and 

Non-GHG 

Impacts c,d

n/a n/a n/a n/a n/a n/a

Reduced CO2 Emissions at each assumed SCC value a, b

5% (avg 

SCC)

$200 $200 $200 $300 $300 $1,200

3% (avg 

SCC)

$600 $700 $700 $1,100 $1,200 $4,300

2.5% (avg 

SCC)

$1,000 $1,000 $1,100 $1,700 $1,800 $6,600

3% (95th 

percentile)

$1,900 $2,000 $2,200 $3,200 $3,600 $12,900

Monetized Net Benefits at each assumed SCC value a, b

5% (avg 

SCC)

$3,600 $3,600 $3,800 $6,000 $6,000 $23,000

3% (avg 

SCC)

$4,000 $4,100 $4,300 $6,800 $6,900 $26,100

2.5% (avg 

SCC)

$4,400 $4,400 $4,700 $7,400 $7,500 $28,400

3% (95th 

percentile)

$5,300 $5,400 $5,800 $8,900 $9,300 $34,700

Notes: 

a Net present value of reduced CO2 emissions is calculated differently than other benefits. The same 

discount rate used to discount the value of damages from future emissions (SCC at 5, 3, 2.5 percent) is used 

to calculate net present value of SCC for internal consistency. Refer to the SCC TSD for more detail. 
Draft Joint EPA/NHTSA NPRM Preamble HD GHG/FC Standards (12/6/2010)

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b

Section VIII.G notes that SCC increases over time. Corresponding to the years in this table, the SCC 

estimates range as follows: for Average SCC at 5%: $5-$16; for Average SCC at 3%: $22-$46; for 

Average SCC at 2.5%: $36-$66; and for 95th percentile SCC at 3%: $66-$139. Section VIII.G also 

presents these SCC estimates.

c The monetized GHG benefits presented in this analysis exclude the value of changes in non-CO2 GHG 

emissions expected under this proposal (see RIA Chapter 5). Although EPA has not monetized changes in 

non-CO2 GHGs, the value of any increases or reductions should not be interpreted as zero. 

d Non-GHG-related health and welfare impacts (related to PM2.5 and ozone exposure) were not estimated 

for this proposal, but will be included in the analysis of the final rulemaking. 

L. Economy-Wide Impacts of the Rule

EPA has undertaken an analysis of the economy-wide impacts of the mediumand heavy-duty truck fuel economy and GHG standards. The results presented in this 

section were not a factor regarding the appropriateness of the GHG or fuel economy 

standards. However, this analysis provides more insight into some of the potential

impacts of this proposal. 

It is anticipated that the GHG tailpipe standards would have impacts on the U.S. 

economy that extend beyond the transportation sector. The price of medium- and heavyduty trucks would increase with this proposal. This proposal would also lower the 

demand for transportation fuels, resulting in fuel savings to vehicle users and a lower 

overall world oil price. This combination of effects—price increases for trucks and lower 

demand and world oil prices—would impact all sectors of the economy that use mediumand heavy-duty trucks and fuels as intermediate inputs to produce final goods. 

Households would also be impacted indirectly as consumers of final goods. Furthermore, 

as discussed in Chapter 6, truck VMT is largely driven by changes in economic activity. 

To the extent that we have accounted for the increase in VMT due to the rebound effect 

in our analysis, it seems appropriate to also take into account the change in economic 

activity as a result of the rule. 

It is important to note, however, that these potential impacts do not represent 

additional benefits or costs from the regulation. Instead, they represent the effects on the 

U.S. economy as its direct benefits and costs are transmitted through changes in prices in 

the affected markets, including those for vehicles and their components, fuel, and the 

various resources used to supply them. In addition, this analysis assumes that the fuel 

savings modeled here would not have taken place in the absence of this rule and that 

there is no welfare loss associated with mandating higher fuel efficiency. As discussed in 

Section VIII.A., this assumption is based on the argument that there are imperfections in 

the market for fuel-saving technology in the trucking industry.

To estimate the impacts of this proposal on U.S. Gross Domestic Product (GDP) 

and personal consumption, EPA has used an economy-wide, computable general 

equilibrium (CGE) model. The economy-wide model used in this analysis is the 
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Intertemporal General Equilibrium Model (IGEM).388 IGEM is a model of the U.S. 

economy with an emphasis on the economy’s energy and environmental aspects. IGEM 

is a dynamic model which depicts growth of the economy due to capital accumulation, 

technical change and population change. The model utilizes a unified accounting 

framework consistent with the National Income and Product Accounts and the Industry

Classification System. It is a detailed multi-sector model covering thirty-five industries, 

consisting of five energy and thirty non-energy sectors. The model ensures market 

balances (supply equals demand) in value and quantity terms, including limits placed on 

private investment dictated by domestic and foreign saving behavior and by the fiscal 

policies of federal, state and local governments. 

Capital accumulation in the model arises from the saving and investment behavior 

of households and businesses and provides an essential input to production and 

consumption. Households in the model make choices regarding present and future 

consumption (i.e., saving) and make choices regarding the allocation of time between 

labor and leisure. The model covers all aspects of long-run growth including the supply 

of capital, labor, imported and intermediate inputs to production; the rates and directions 

of exogenous and endogenous technical change for each producing sector; and the 

degrees of substitutability among inputs and commodities in production and final demand 

(consumption, investment, governments and foreign trade). The substitution possibilities 

for both producers and consumers in IGEM are driven by model parameters that are 

based on observed market behavior revealed over the past forty to fifty years. 

In order to model this proposal, the CGE model uses outputs of the transportation 

sector models as inputs to determine the economy-wide impacts of this proposal. 

Specifically, the model uses information from other models on incremental costs of 

vehicle technologies, reduction in fuel consumption, and impacts on the world oil price. 

The incremental cost of vehicle technologies is used to generate a percentage change in 

vehicle cost that is applied to the IGEM motor vehicles sector. However, since the cost 

and fuel savings vary significantly across truck classes, we have used a weighted average

cost and fuel saving in this analysis. In addition, medium- and heavy-duty trucks make 

up approximately XXX% of the motor vehicles sector; therefore the cost increases 

represented here only apply to that portion of the IGEM sector. The data on reduction in 

fuel consumption are used as inputs to IGEM in order to reduce the amount of refined 

petroleum sector output required by the transportation sector and other sectors in the 

model. Finally, the estimates of reductions in the world oil price are directly used to 

reduce the oil price in the model. The changes in world oil price are estimated using the 

Energy Security Oil Premium Model maintained by Oak Ridge National Laboratory, 

which is discussed in more detail in Section VIII.I.

 

388 The model is developed and run by Dale W. Jorgenson Associates for EPA. Model Homepage: 

http://www.dja.insightworks.com/
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(1) Impacts on U.S. GDP

In order to use IGEM to estimate the real U.S. GDP impacts of this proposal, we 

analyzed the impact of changes in the costs of medium- and heavy-duty trucks, changes 

in fuel consumption from the shift to a lower GHG-emitting vehicle stock, and the 

impacts of changes in the demand for motor fuels on fuel prices. See Section VIII.B for 

additional information on the change in vehicle technology costs, Section VIII.E for

details on changes in fuel demand, and Section VIII.I for a discussion on the monopsony

effect. It is important to note that the economy-wide analysis does not include a 

representation of a number of additional benefits (e.g. reducing greenhouse gas and nonGHG emissions), and thus the GDP impacts presented here do not incorporate the results 

of a complete cost benefit analysis. Table VIII-26 and Figure VIII-1 show the Reference 

Case GDP and GDP with this proposal from 2015 through 2050.

Table VIII-26: Annual GDP Impacts Associated with This proposal (Billions of 2008 dollars)

year reference case 

GDP

GDP with RULE % change from reference 

case

2015 $XXX $XXX XXX%

2020 $XXX $XXX XXX%

2030 $XXX $XXX XXX%

2040 $XXX $XXX XXX%

2050 $XXX $XXX XXX%

Figure VIII-1: Gross Domestic Product

In the Reference Case, GDP rises from approximately $XXX trillion in 2015 to 

$XXX trillion in 2020, $XXX trillion in 2030, $XXX trillion in 2040, and $XXX trillion 

in 2050. With this proposal, GDP rises from approximately $XXX trillion in 2015 to 

$XXX trillion in 2020, $XXX trillion in 2030, $XXX trillion in 2040, and $XXX trillion 

in 2050.

The fuel savings and lower world oil prices that result from this proposal lead to 

lower prices economy-wide, even when the impact of higher vehicle costs are factored 

into this analysis. Lower prices allow for additional purchases of investment goods 

which, in turn, lead to a larger capital stock. These price reductions also allow higher 

levels of real government spending while improving U.S. competitiveness thus promoting 
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increased exports relative to the growth driven increase in imports. As a result, GDP is 

expected to increase as a result of this proposal. 

(2) Impacts on U.S. Consumption

In addition to showing the impacts of the GHG vehicle rule on U.S. GDP, EPA 

also shows the impacts on real U.S. personal consumption expenditures. Table VIII-27

and Figure VIII-2 show the Reference Case consumption and consumption with this 

proposal from 2015 through 2050. 

Table VIII-27: Consumption Impacts of the Rule (Billions of 2008 dollars)

year reference case 

consumption

consumption with 

RULE

% change from reference 

case

2015 $XXX $XXX XXX%

2020 $XXX $XXX XXX%

2030 $XXX $XXX XXX%

2040 $XXX $XXX XXX%

2050 $XXX $XXX XXX%

Figure VIII-2 Consumption

In the Reference Case, consumption rises from approximately $XXX trillion in 

2015 to $XXX trillion in 2020, $XXX trillion in 2030, $XXX trillion in 2040, and $XXX 

trillion in 2050. With this proposal, consumption rises from approximately $XXX trillion 

in 2015 to $XXX trillion in 2020, $XXX trillion in 2030, $XXX trillion in 2040, and 

$XXX trillion in 2050. 

The consumption impacts on a per household basis are presented in Table VIII-28

and Figure VIII-3. Higher vehicle costs are projected to reduce household consumption 

slightly in the first few years of the rule implementation. Over time, fuel savings increase 

and the price of world oil decreases, which leads to lower prices economy-wide. As a 

result, household consumption increases over the long term. 

Table VIII-28: Consumption Impacts of This proposal per Household (2007$)
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year reference case 

consumption

consumption with 

RULE

% change from reference 

case

015

$XXX $XXX XXX%

020

$XXX $XXX XXX%

030

$XXX $XXX XXX%

040

$XXX $XXX XXX%

050

$XXX $XXX XXX%

Figure VIII-3 Consumption per Household

See the draft RIA Chapter XXX for additional information.

IX. Analysis of Alternatives 

The heavy-duty truck segment is very complex. The sector consists of a diverse 

group of impacted parties, including engine manufacturers, chassis manufacturers, truck 

manufacturers, trailer manufacturers, truck fleet owners and the air breathing public. The 

proposal the Agencies have laid out today is largely shaped to maximize the 

environmental and fuel savings benefits of the program respecting the unique and varied 

nature of the regulated industries. In developing this proposal, we considered a number 

of alternatives that could have resulted in fewer or potentially greater GHG and fuel 

consumption reductions that the program we are proposing. This section summarizes the 

alternatives we considered. We welcome comments on all of these alternatives.

A. What are the alternatives that the agencies considered?

In developing alternatives, NHTSA must consider EISA’s requirement for the 

MD/HD fuel efficiency program noted above. 49 U.S.C. § 32902(k)(2) and (3) contain 
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the following three requirements specific to the MD/HD vehicle fuel efficiency 

improvement program: (1) The program must be “designed to achieve the maximum 

feasible improvement”; (2) the various required aspects of the program must be 

appropriate, cost-effective, and technologically feasible for MD/HD vehicles; and (3) the 

standards adopted under the program must provide not less than four model years of lead 

time and three model years of regulatory stability. In considering these various 

requirements, NHTSA will also account for relevant environmental and safety

considerations.

Each of the alternatives proposed by NHTSA and EPA represents, in part, a 

different way the agencies could establish a HD program pursuant to EISA and the CAA. 

The agencies are proposing Alternative 6. The alternatives below represent a broad range 

of approaches under consideration for setting proposed HD vehicle fuel efficiency and 

GHG emissions standards. The alternatives that the agencies are proposing, in order of 

increasing fuel efficiency and GHG emissions reductions, are:

(1) Alternative 1: No Action

A “no action” alternative assumes that the agencies would not issue rules

regarding a MD/HD fuel efficiency improvement program, and is considered to comply

with NEPA and to provide an analytical baseline against which to compare 

environmental impacts of the other regulatory alternatives.389 The agencies refer to this 

as the “No Action Alternative” or as a “no increase” or “baseline” alternative.

(2) Alternative 2: Engine Only

The EPA currently regulates heavy-duty engines, i.e., engine manufacturers, 

rather than the vehicle as a whole, in order to control criteria emissions.390 Under 

Alternative 2, the agencies would similarly set engine performance standards for each 

vehicle class, Class 2b through Class 8, and would specify an engine cell test procedure, 

as EPA currently does for criteria pollutants. HD engine manufacturers would be 

responsible for ensuring that each engine could meet the applicable vehicle class engine 

performance standard when tested in accordance with the specified engine cell test 

 

389 NEPA requires agencies to consider a “no action” alternative in their NEPA analyses and to compare the 

effects of not taking action with the effects of the reasonable action alternatives to demonstrate the different 

environmental effects of the action alternatives. See 40 CFR § 1502.2(e), 1502.14(d). CEQ has explained 

that “[T]he regulations require the analysis of the no action alternative even if the agency is under a court 

order or legislative command to act. This analysis provides a benchmark, enabling decision makers to 

compare the magnitude of environmental effects of the action alternatives. It is also an example of a 

reasonable alternative outside the jurisdiction of the agency which must be analyzed. [See 40 CFR 

§ 1502.14(c).] * * * Inclusion of such an analysis in the EIS is necessary to inform Congress, the public, 

and the President as intended by NEPA. [See 40 CFR § 1500.1(a).] “Forty Most Asked Questions 

Concerning CEQ’s National Environmental Policy Act Regulations,” 46 FR 18026 (1981) (emphasis 

added).

390 There are several reasons for this approach. In many cases the engine and chassis are produced by 

different manufacturers and it is more efficient to hold a single entity responsible. Also, testing an engine 

cell is more accurate and repeatable than testing a whole vehicle.
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procedure. Engine manufacturers could improve HD engines by applying the 

combinations of fuel efficiency improvements and GHG emissions reduction

technologies to the engine that they deem best achieve that result.

(3) Alternative 3: Class 8 Combination Tractors

Combination tractors consume the largest fraction of fuel within the medium- and 

heavy-duty truck segment. Tractors also offer significant potential for fuel savings due to 

the high annual mileage and high vehicle speed of typical trucks within this segment, as 

compared to annual mileage and average speeds/duty cycles of other vehicle classes. This 

alternative would set performance standards for both the engine of Class 8 vehicles and 

the overall vehicle efficiency performance for the Class 8 combination tractor segment. 

Under Alternative 3, the agencies would set an engine performance standard, as discussed 

under Alternative 2, for Class 8 tractors. In addition, Class 8 combination tractor 

manufacturers would be required to meet an overall vehicle performance standard by 

making various non-engine fuel saving technology improvements. These non-engine fuel 

efficiency and GHG emissions improvements could be accomplished, for example, by a 

combination of improvements to aerodynamics, lowering tire rolling resistance, 

decreasing vehicle mass (weight), reducing fuel use at idle, or by adding intelligent 

vehicle technologies.391 Compliance with the overall vehicle standard could be 

determined using a computer model that would simulate overall vehicle fuel efficiency

given a set of vehicle component inputs. Using this compliance approach, the Class 8 

vehicle manufacturer would supply certain vehicle characteristics (relating to the 

categories of technologies noted immediately above) that would serve as model inputs. 

The agency would supply a standard Class 8 vehicle engine’s contribution to overall 

vehicle efficiency, making the engine component a constant for purposes of compliance 

with the overall vehicle performance standard, such that compliance with the overall 

vehicle standard could only be achieved via efficiency improvements to non-engine 

vehicle components. Thus, vehicle manufacturers could make any combination of 

improvements of the non-engine technologies that they believe would best achieve the 

Class 8 overall vehicle performance standard.

(4) Alternative 4: Engines and Class 7 and 8 Tractors

This alternative combines Alternative 2 with Alternative 3, and additionally 

would set an overall vehicle efficiency performance standard for Class 7 tractors. This 

alternative would, thus, set standards for all HD engines and would set overall vehicle 

performance standards for Class 7 and 8 tractors, as described for Class 8 combination

tractors under Alternative 3. Class 7 tractors make up a small percent of the tractor 

market, approximately 9 percent.392 Though the segment is currently small, the agencies 

 

391 See the NAS Report at Note (#), above, for discussions of the potential fuel efficiency improvement 

technologies that can be applied to each of these vehicle components. (Chapter 5).

392 MJ Bradley. Heavy Duty Vehicle Market Analysis. May 2009.
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believe the inclusion of this class of vehicles would help prevent a potential class 

shifting, as noted in the NAS panel report.393 

(5) Alternative 5: Engines, Class 7 and 8 Tractors, and Class 2b/3 Pickup 

Trucks and Vans

This alternative builds on Alternative 4 through the addition of an overall vehicle 

efficiency performance standard for Class 2b/3 Pickup Trucks and Vans (or work trucks). 

Therefore, under this alternative, the agencies would set engine performance standards 

for each MD/HD vehicle class, and would also set overall vehicle performance standards 

for Class 7 and 8 tractors, as well as for Class 2b/3 Pickup Trucks and Vans. Compliance 

for the Class 2b and 3 pickup trucks and vans would be determined through a fleet 

averaging process similar to determining passenger car and light truck compliance with 

CAFE standards.

(6) Alternative 6: Engines, Tractors, and Class 2b through 8 Trucks. 

Alternative 6 represents the agencies’ preferred approach. This alternative would 

set engine efficiency standards, engine GHG emissions standards, overall vehicle fuel 

efficiency standards, and overall vehicle GHG emissions standards for Class 2b and 3 

pickup trucks and vans and the remaining Class 2b through Class 8 trucks and the 

engines installed in them. This alternative essentially sets fuel efficiency and GHG 

emissions performance standards for both the engines and the overall vehicles in the 

entire heavy-duty truck sector. Compliance with each vehicle class’ engine performance 

standard would be determined as discussed in the description of Alternative 2. 

Compliance with the tractor and vocational truck classes’ overall vehicle performance 

standard (Class 2b through 8 trucks) would be determined as discussed in the description 

of Alternative 3. Compliance for the Class 2b and 3 pickup trucks and vans as described 

in Alternative 5.

(7) Alternative 7: Engines, Tractors, Trucks, and Trailers. 

This alternative builds on Alternative 6 by adding a performance standard for fuel 

efficiency and GHG emissions of commercial trailers. Therefore, this alternative would 

include fuel efficiency performance standards and GHG emissions standards for Class 2b 

and 3 work truck and Class 3 through Class 8 vocational truck engines, and the 

performance standards for the overall fuel efficiency and GHG emissions of those 

vehicles, as described above. 

(8) Alternative 8: Engines, Tractors, Trucks, and Trailers with Hybrid 

Powertrains

Alternative 8 includes all elements of Alternative 7, plus applies the maximum 

application of hybrids to the pickup trucks, vans, vocational trucks, and tractors by the 

 

393 See NAS at Note (#), above, at page 6-38.
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2014 and the 2017 MY. The agencies are applying a 25 percent reduction to CO2

emissions and fuel consumption, based on the findings of the NAS report.394 The 

agencies also project a cost of $30,000 per vehicle for the vocational vehicles and 

combination tractors, which is the median value described in the NAS report for the 

vocational vehicles and tractors. The agencies are projecting a cost of $9,000 per vehicle 

for the HD pickup trucks and vans, again based on the NAS report.395

B. How do these alternatives compare in overall GHG emissions 

reductions and fuel efficiency and cost?

The agencies analyzed all seven alternatives through MOVES to evaluate the 

impact of each proposed alternative, as shown in Table IX-1.

Table IX-1: Annual CO2 and Oil Savings in 2030 and 2050

Downstream CO2

Savings (MMT)

Oil Savings (billion 

gallons)

2030 2050 2030 2050

Alt. 1 0 0 0 0

Alt. 2 - Total 29 46 2.9 4.6

Tractors 19 27 1.8 2.6

HD Pickup Trucks 4 7 0.4 0.7

Vocational Trucks 6 13 0.6 1.2

Alt. 3 - Total 35 50 3.4 4.9

Tractors 35 50 3.4 4.9

HD Pickup Trucks 0 0 0 0

Vocational Trucks 0 0 0 0

Alt. 4 - Total 50 76 5.0 7.5

Tractors 40 57 3.9 5.6

HD Pickup Trucks 4 7 0.4 0.7

Vocational Trucks 6 13 0.6 1.2

Alt. 5 - Total 54 82 5.4 8.2

Tractors 40 57 3.9 5.6

HD Pickup Trucks 8 13 0.8 1.3

Vocational Trucks 6 13 0.6 1.2

 

394 NAS Report. Page 6-28.

395 NAS Report. Page 6-28.
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Downstream CO2

Savings (MMT)

Oil Savings (billion 

gallons)

Preferred - Total 58 91 5.8 9.0

Tractors 40 57 3.9 5.6

HD Pickup Trucks 8 13 0.8 1.3

Vocational Trucks 10 21 1.0 2.1

Alt. 7 - Total 62 96 6.1 9.5

Tractors 40 57 3.9 5.6

HD Pickup Trucks 8 13 0.8 1.3

Vocational Trucks 10 21 1.0 2.1

Trailers 4 5 0.4 0.5

Alt. 8 - Total

Tractors

HD Pickup Trucks

Vocational Trucks

Trailers

The aggregate technology costs for each alternative in 2030 and 2050 are included 

in Table IX-2.

Table IX-2: Technology Cost Projections for the Alternatives

Technology costs (2008$ millions)

2030 2050

Alt. 1 $0 $0

Alt. 2 - Total $1,226 $1,544

Tractors $78 $103

HD Pickup Trucks $980 $1,140

Vocational Trucks $168 $301

Alt. 3 - Total $773 $1,023

Tractors $773 $1,023

HD Pickup Trucks $0 $0

Vocational Trucks $0 $0

Alt. 4 - Total $1,952 $2,506

Tractors $805 $1,065

HD Pickup Trucks $980 $1,140

Vocational Trucks $168 $301
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Alt. 5 - Total $1,953 $2,506

Tractors $805 $1,065

HD Pickup Trucks $980 $1,140

Vocational Trucks $168 $301

Preferred - Total $2,016 $2,623

Tractors $805 $1,065

HD Pickup Trucks $980 $1,140

Vocational Trucks $231 $418

Alt. 7 - Total

Tractors $805 $1,065

HD Pickup Trucks $980 $1,140

Vocational Trucks $231 $418

Trailers $713 $943

Alt. 8 - Total

Tractors

HD Pickup Trucks

Vocational Trucks

Trailers

C. How would the agencies include commercial trailers, as described in 

Alternative 7?

A common theme throughout our proposed HD Program is a recognition of the 

diversity and complexity of the heavy-duty vehicle segment. Trailers are an important 

part of this segment and are no less diverse in the range of functions and applications they

serve. They are the primary vehicle for moving freight in the United States. The type of 

freight varies from retail products to be sold in stores, to bulk goods such as stones, to 

industrial liquids such as chemicals, to equipment such as bulldozers. Semi-trailers come 

in a large variety of styles – box, refrigerated box, flatbed, tankers, bulk, dump, grain, and 

many others. The most common type of trailer is the box trailer, but even box trailers 

come in many different lengths ranging from 28 feet to 53 feet or greater, and in different 

widths, heights, depths, materials (wood, composites, and/or aluminum), construction 

(curtain side or hard side), axle configuration (sliding tandem or fixed tandem), and 

multiple other distinct features. NHTSA and EPA believe trailers impact the fuel 

consumption and CO2 emissions from combination trucks and the agencies see 

opportunities for reductions. Unlike trucks and engines, EPA and NHTSA have very

limited experience related to regulating trailers for fuel efficiency or emissions. 

Likewise, the trailer manufacturing industry has only the most limited experience 

complying with regulations related to emissions and none with regard to EPA or NHTSA 
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certification and compliance procedures. We have therefore decided not to propose 

regulations for trailers in today’s proposal. However in order to broadly solicit comments 

on controlling fuel efficiency and GHG emissions through trailer regulations we are 

describing in an advanced notice of proposed regulation style a program which could set 

the foundation of a future rulemaking for trailers. We are soliciting comments on all 

aspects of the information shared in this section.

(1) Why are the agencies considering the regulation of trailers?

Trailers impact the aerodynamic drag, rolling resistance, and overall weight of the 

combination tractor-trailer. TIAX, LLC performed an evaluation of SmartWay trailer 

technologies, and found that they provide the opportunity to reduce fuel consumption and 

greenhouse gas emissions from tractor trailers by up to 10 to12 percent for aerodynamics 

and 3 to 6 percent for lower rolling resistance tires.396 Reductions of this magnitude are 

larger than can be readily accomplished from improvements in engine design and are 

roughly of the same magnitude as reductions possible through improvements in truck 

designs. Not only do trailers represent a significant opportunity for reductions as 

discussed later in this section, but we have strong reason to believe that these reductions 

would not occur absent regulation as noted in the recent NAS report.

The NAS report notes: 

A perplexing problem for any option, regarding Class 8 vehicles, is what to do 

about the trailer. The trailer market represents a clear barrier with split incentives, 

where the owner of the trailer often does not incur fuel costs, and thus has no 

incentive to improve aerodynamics of the trailer itself or to improve the 

integration of the trailer with the tractor or truck.

397

In other words, trailers affect the fuel efficiency of shipping, but they do not face 

strong uniform incentives to coordinate with truck owners. In principle, if truck owners 

had the ability to choose what trailers they accepted, they could require trailers with fuelsaving technologies; in practice, though, truck owners have limited practical ability to be 

selective about what trailers they accept. 

In this setting, information provision may be inadequate to address the related 

problems of split incentives and thin markets. Regulation aimed at trailer manufacturers 

can contribute fuel savings and GHG reductions that otherwise may be difficult to 

achieve. 

 

396 TIAX. Assessment of Fuel Economy Technologies for Medium- and Heavy-Duty Vehicles. November 

2009. Pages 4-50 and 4-57.

397 See NAS at Note (#), above, at ,p. 8-8.
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(2) What does the trailer industry look like? 

(a) Trailer Types

The commercial trailer market includes a wide variety of trailer types. The 

market is dominated by box (or van) trailers, which made up approximately 63 percent of 

the new trailers registered between 2003 and 2007.398 The top ten new trailer 

registrations are included in by type are listed in Table IX-3.

Table IX-3: Trailer Registrations

Trailer Type Percentage of 

Registrations (2003-2007)399

Box 63%

Flatbed (Platform) 8%

Container Chassis 7%

Refrigerated Van 5%

Dump 3%

Grain 2%

Flatbed Drop Deck 2%

Tank 1%

Lowbed 1%

Livestock 1%

The remaining 6.5 percent of the trailer registrations consisted of livestock, 

transfer, hazardous chemical tanks, hoppers, gooseneck livestock, lowbed drop deck, 

beverage, special, dry bulk tanker, logging, wood chip, and other types of trailers. Within 

each of these main trailer categories there are distinctions among trailer construction, 

materials, dimension, mass, and functionality, all of which can impact a trailer’s 

contribution to truck fuel consumption and greenhouse gas emissions.

(b) Trailer Fleet Size Relative to the Tractor Fleet

The industry generally recognizes that the ratio of the number of trailers in the 

fleet relative to the number of tractors is typically three-to-one.400 Typically at any one 

time, two trailers are parked while one is being transported. For certain private fleets, this 

ratio can be greater, as high as six-to-one. This characteristic of the fleet impacts the cost 

effectiveness of trailer technologies because a trailer on average will only travel one third 

of the miles travelled by a tractor. 

 

398 See MJ Bradley at Note 392 , above.

399 See MJ Bradley at Note 392, above.

400 See TIAX at Note 396 above, at page 4-49.
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(c) Trailer Owners

Trailer ownership is distinct from that of the tractors. Trailers are often owned by

shippers or by leasing companies, not by the trucking fleets. A special type of “trailer” is 

a shipping container used for intermodal surface movement to transport freight from 

ocean going liner vessels to inland destinations via truck, rail or barge. When hauled by a 

truck, the container is loaded on a specialty piece of equipment called a “chassis.” This 

consists of a frame and axle/wheel assemblies on which the container is mounted, so that 

when the chassis and container are assembled the unit serves the same function as a road 

trailer.401 Container chassis are sometimes owned by specialty companies and are leased 

to ports, fleets, and shippers. Trailers that are purchased by fleets are typically kept much 

longer than are the tractors, so trucks and trailers have different purchasing cycles. 

Because of the disconnect between owners, the trailer owners may not benefit directly

from fuel consumption and GHG emission reductions.

(d) Trailer Builders

The top ten builders of with the largest market share of trailer sales in 2009 

include Utility Trailer Manufacturing, Great Dane, Wabash National, Hyundai Translead, 

Timpte, Wilson Trailer, Stoughton Trailers, Heil Trailer, Fontaine Trailer, and 

MANAC.402 However, nearly half of all trailer manufacturers are considered small 

businesses by the Small Business Administration definition.403 Therefore, the agencies 

will be required to convene a Small Business Regulatory Enforcement Fairness Act 

(SBREFA) panel to conduct the proper outreach to all stakeholders impacted by a 

proposed regulation for trailers.

Although trailer manufacturing is an important sector within the commercial 

vehicle manufacturing industry, trailers are far less mechanically complex than are the 

trucks that haul them. This means that trailer manufacturing has a low barrier to entry 

compared to automotive or truck manufacturers. The agencies can envision that 

proposed regulation would require significant effort to maintain a level playing field 

within the market to reduce the incentive to work around the regulation.

(3) What technologies are available to reduce fuel consumption and GHG 

emissions from trailers? 

There are opportunities to reduce the fuel consumption and GHG emissions 

impact of the trailer through aerodynamics, tires, and tare weight reductions to some 

extent in most types of trailers. In addition, refrigerated trailers have opportunities to 

both reduce the fuel consumption and CO2 emissions of the Trailer Refrigeration Unit 

 

401 Per 46 CFR § 340.2, 

402 Trailer-Body Builders.com. 2009 North American Truck Trailer Output. http://trailerbodybuilders.com/trailer-output/output/2009_trailer_output_table/

403 Per SBA definition for NAICS 336212, companies with less than 500 employees are considered small 

businesses.
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(TRU) and reduce GHG emissions through reduced refrigerant leakage. There are 

additional opportunities being developed for improvements in suspension systems, trailer 

structure, dump hoists and other features, depending upon the type of trailer and its 

intended function. 

(a) Aerodynamics

Trailer aerodynamic technologies to date have focused on the box, van trailers –

the largest segment of the trailer fleet. This focus on box, van trailers may also be 

partially attributed to the complexity of the shape of the non-box, van trailers which, in 

many cases, transport cargo that is in the windstream (e.g., flatbeds that carry heavy

equipment, car carriers, and loggers). For non-box, van trailers you could have a 

different aerodynamic shape with every load. While some technologies exist to address 

aerodynamic drag for non-box, van trailers, it has been either experimental or not widely

commercially available. 

Current trailer aerodynamic technologies for box trailers are estimated to provide 

approximately 7 percent GHG emission reductions when used as a package.404 For box 

trailers, trailer aerodynamic technologies have addressed drag at the front of the trailer 

(i.e., vortex traps, leading edge fairings), underneath the trailer (i.e., side skirts, wheel 

fairings) and the trailer rear (i.e., afterbodies). These technologies are commercially 

available and have seen moderate adoption rates. More recent trailer aerodynamic 

innovations channel air flow around the sides and under the trailer using underbody air 

deflectors (“underbelly treatment”). Table IX-4 lists technologies that the EPA 

SmartWay program has evaluated for use on box, van trailers. In general, the 

performance of these technologies is dependent upon the smooth transition of airflow 

from the tractor to the trailer. True for both tractor and trailer aerodynamic drag 

reduction, the overall shape can be optimized to minimize aerodynamic drag. 

 

404 [Cite] 
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Table IX-4: Aerodynamic Technologies for Trailers

Location on Trailer Technology Type Designed Effect

Front Vortex trap Reduce drag induced by cross-flow 

through gap between tractor and trailer

Front Front fairings Smoothly transition air to flow from 

tractor to the trailer

Rear Afterbody (boat tail 

and rear fairings)

Reduce pressure drag induced by the 

trailer wake

Undercarriage Side skirts Manage flow of air underneath tractor to 

reduce eddies and wake

Undercarriage Underbelly treatment Manage flow of air underneath tractor to 

reduce eddies and wake

Accessories General Reducing surface area perpendicular to 

travel and minimizing complex shapes 

that may induce drag

General Advanced, passive air 

management

Manage airflow through passive 

aerodynamic shapes or devices that keep 

flow attached to the vehicle (tractor and 

trailer)

The agencies’ initial assessment of the incremental costs of aerodynamics is 

included in Table IX-5. The costs represent a high volume retail price of the components 

based on information developed for the NAS report405 and the ICF cost contract.406 

Table IX-5: Aerodynamic Technology Costs

Technology Cost Estimate

Trailer Side Skirts $1300 - 1600

Gap Fairing $850

Trailer Aerocone $1000

Boat Tails $1960

Air Tabs $180

Some of these technologies, such as side skirts, may be applicable to other trailer 

types. The agencies are interested in comments regarding the aerodynamic improvement 

opportunities in all types of trailers.

 

405 See TIAX, Note 396 above.

406 ICF. Investigation of Costs for Strategies to Reduce Greenhouse Gas Emissions fro Heavy-Duty OnRoad Vehicles. June 2010.
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(b) Tires

The rolling resistance coefficient (RRc) baseline for today’s fleet is 6.5 kg/ton for 

the trailer tire, based on sales weighting of the top three manufacturers based on market 

share. This value is based on new trailer tires, since rolling resistance decreases as the 

tread wears. To achieve the intended emissions benefit, SmartWay established the 

maximum allowable RRc for the trailer tire 15% below the baseline or 5.5 kg/ton. 

Similar to combination tractor tires, low rolling resistance tires are available as either 

dual tires or as single wide-base tires for trailers. 

Research indicates the contribution to overall vehicle fuel efficiency by tires is 

approximately equal to the proportion of the vehicle weight on them.407 On a fully

loaded typical class 8 long-haul tractor and trailer, 42.5 percent of the total tire energy

loss attributed to rolling resistance is from the trailer tires. The TIAX assessment of 

single wide based tires on the trailer found that they provide approximately a 3 percent 

fuel consumption benefit over a standard dual tire package.408

Based on the ICF report,409 EPA and NHTSA estimate the incremental retail cost 

for low rolling resistance tires as $78 per tire. The agencies also estimate that the 

incremental cost to replace a pair of dual tires with a single wide based tire is $216, 

however, the cost can be reduced when the wheel replacement cost is considered, since 

half the number of tires and wheels are needed.

The inflation pressure of tires also impacts the rolling resistance. Underinflation 

causes an increase in rolling resistance and fuel consumption. Trailer systems, such as 

tire pressure monitoring or automatic tire inflation, can help drivers insure that they are 

traveling with properly inflated tires. Estimates vary, but TIAX estimates on average that 

a trailer automatic tire inflation system could provide a 0.6% benefit to fuel consumption 

for a cost of approximately $300 to $400.410 

(c) Weight Reduction

Reduction in trailer tare (or empty) weight can lead to fuel efficiency reductions 

in two ways. For applications which are not limited by the weight limit, the overall 

weight of the tractor and trailer combination would be reduced and would lead to 

improved fuel efficiency. For the applications which limit the payload due to the weight 

restrictions, the lower trailer weight would allow additional payload to be transported 

during the truck’s trip. Weight reduction opportunities in trailers exist in both the 

structural components and in the wheels and tires. Material substitution (replacing steel 

with aluminum) is feasible for components such as roof posts, bows, side posts, cross 

 

407 Bridgestone Firestone, North American Tire, LLC. “Tires & Truck Fuel Economy,” A New

Perspective. Special Edition Four, 2008

408 See TIAX, Note 396 above, at page 4-56.

409 See ICF, Note 406, above.

410 See TIAX, Note 396 above, at page 4-58.
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members, floor joists, and floors. Similar material substitution is feasible for wheels. 

Weight reduction opportunities also exist through the use of single wide based tires 

replacing two dual tires.

The agencies’ assessment of the ICF report411 indicates that the expected 

incremental retail prices of the lightweighted components are as included in Table IX-6: 

Trailer Lightweighting Costs.

Table IX-6: Trailer Lightweighting Costs

Component Cost

Roof Posts/Bows $120

Side Posts $525

Cross Members/Floor Joists $400

Floor $1,500

Wheels $1,500

(d) Opportunities in Refrigerated Trailers

Refrigeration units are used in van trailers to transport temperature sensitive 

products. A traditional TRU is powered by a nonroad diesel engine. There are GHG 

reduction opportunities in refrigerated trailers through the use of electrical trailer 

refrigeration units and highly reflective trailer coatings. 

Highly reflective materials, such as reflective paints or translucent white 

fiberglass roofs, can reflect the solar radiation and decrease the cooling demands on the 

trailer’s refrigeration unit. A reflective composite roof can cost approximately $800, the 

addition of reflective tape to a trailer roof would cost approximately $450.

Hybrid trailer refrigeration units utilize a diesel engine which drives a generator 

which in turn powers the compressor and fans. The cost of this unit is approximately

$4,000.

(4) What approaches could the agencies propose for evaluating fuel efficiency 

and GHG emissions contributions from trailers?

Building from EPA’s SmartWay experience, EPA and NHTSA have considered 

several options to demonstrate GHG and fuel consumption reductions from trailer 

technologies. The agencies welcome comments on the testing approaches describe below 

or alternative recommendations.

 

411 See ICF, Note,406, above.
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(a) Metric

There are several metrics that the agencies envision could be appropriate used to 

evaluate the fuel consumption and CO2 emissions due to trailers. The agencies are 

proposing the use of a ton-mile metric with a prescribed payload for each truck regulatory

class. A similar approach could be applied to trailer evaluation, which would account for 

aerodynamic improvements, tire improvements, and trailer lightweighting. However, a 

ton-mile metric does not necessarily capture the capacity aspect of trailers. Box trailers 

provide benefits to freight efficiency through an increase in either cubic volume or palletequivalent. Certain box van trailers including drop frame moving van trailers and high 

cube trailers are specially designed to maximize cubic capacity. The agencies welcome 

comments regarding the appropriate metric for trailer efficiency demonstration. 

(b) Potential Approaches to Evaluate GHG Emissions and Fuel Consumption 

Reducing Technologies

(i) Design-Based Specification Approach

The SmartWay certification for tractors and dry box van trailers began as a 

design-based specification, developed on the basis of test results for individual 

components (tires, wheels, aerodynamic equipment, auxiliary power units, and engines) 

that have been demonstrated to improve fuel efficiency and reduce emissions. 

(ii) Modeling Approach

As the agencies are proposing for the evaluation of tractors and vocational trucks, 

a similar simulation model approach could also be applied to trailers. A simulation-based 

model would require the trailer manufacturer input parameters similar to the ones 

proposed in the tractor program – coefficient of drag, tire rolling resistance, and weight. 

The agencies envision that a standardized tractor would be required to fairly assess the 

tractor-trailer system. Both agencies have years of successful experience with vehicle 

simulation modeling. EPA, DOE, DOT, Commerce and others used vehicle simulation 

modeling to jumpstart technology scenarios for the Partnership for a New Generation of 

Vehicles Program, a large public-private research program aimed at developing advanced 

fuel-efficient passenger vehicle designs. Those same agencies used vehicle simulation 

modeling for a similar purpose in the 21st Century Truck Partnership, a sister program to 

develop advanced fuel-efficient commercial truck designs. EPA used vehicle simulation 

modeling to characterize various technology scenarios for its initial design of the 

SmartWay program and to conduct analyses on its test data, test cycles, and related data. 

This experience has demonstrated to the technical staff at EPA and DOT that vehicle 

simulation modeling can be a reliable and feasible tool to assess vehicle performance. 

EPA and NHSTA welcome comments from trailer manufacturers on their ability to run 

simulation models and evaluate the aerodynamics of the trailers which they produce.

(iii) Whole Vehicle Testing – Chassis, Track or On-Road Test

Complete vehicle testing is commonly conducted on chassis dynamometers, 

tracks, or on the road. Light-duty vehicles are tested on chassis dynamometers to 
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demonstrate compliance with EPA and NHTSA regulations associated with emissions 

and fuel efficiency, respectively. Heavy duty truck manufacturers often use paired truck 

test, such as prescribed in SAE J1321,412 to evaluate the difference between two trucks. 

The current SmartWay verification program allows for a modified SAE J1321 test to be 

used to evaluate the fuel consumption performance of trailers due to improvements in 

aerodynamic design. Heavy duty truck fleets today commonly use long term on-road 

testing to evaluate trucks, trailers, and technologies. 

A chassis dynamometer test is a test conducted indoors on a hydrokinetic chassis 

dynamometer. The chassis dynamometer option in this test procedure incorporates many 

of the methods and requirements established in the federal light-duty vehicle and ‘light’ 

heavy-duty vehicle emissions certification chassis test procedure. Chassis dynamometers 

may be found at vehicle test laboratories; typically, facilities used for emissions and 

vehicle fuel efficiency testing. Because the test is conducted on a chassis dynamometer, 

rolling resistance, aerodynamic drag and inertial road load power requirements must be 

determined ahead of time, with coastdown tests and calculations to determine the proper 

horsepower absorption setting for the chassis dynamometer. 

A track test is a complete vehicle test conducted on an outside test track. Test 

tracks may be found at vehicle proving grounds or other facilities specifically designed 

for vehicle or tire performance testing. Because the test involves the vehicle being 

operated on a road surface in a manner similar to that of on-road driving, rolling 

resistance, aerodynamic drag, and inertial road load power requirements are incorporated 

in the test measurement, and do not have to be determined beforehand with a coastdown 

test and calculations. Although the result of a track test reflects real-world vehicle 

performance better than a chassis dynamometer test, by directly evaluating the impacts of 

road effects such as aerodynamic drag of tractors and trailers and rolling resistance 

effects of tires, variability of ambient conditions may result in greater variability of test 

results.413 Therefore, any protocol should include specification of ambient conditions as 

well as specifications for measurement of fuel consumption.

The TMC/SAE Fuel Consumption test is a standardized on-road test procedure 

for comparing the in-service fuel consumption of two conditions of a test vehicle or one 

test vehicle to another.414 The procedure uses an unchanging control vehicle run in 

tandem with the test vehicle. The result of the test is the percent difference in fuel 

consumption between two test vehicles.

 

412 Society of Automotive Engineers. Joint TMC/SAE Fuel Consumption Test Procedure – Type II. SAE 

J1321. October 1986.

413 However, it has been demonstrated that even tests conducted in laboratories have differences in 

repeatability within a given laboratory and differences in reproducibility among laboratories. See 

“Interlaboratory Crosscheck of Heavy duty Vehicle Chassis Dynamometers” Final Report CRC Project 

No. E-55-1, May, 2002.

414 See SAE, Note 412, above.
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The agencies are interested in comments regarding the advantages and 

disadvantages of each approach, along with any baseline trailer performance.

(5) What actions are already being taken to improve the efficiency of trailers? 

(a) SmartWay Certified Trailers

Beginning in 2007, EPA began designating certain new dry freight box van 

trailers for on the road use of 53 feet or greater length Certified SmartWay Trailers. 

Older or pre-owned trailers could also be certified if properly retrofitted. In order for a 

trailer to be designated as Certified SmartWay, the trailer must be equipped with

aerodynamic devices such as trailer skirts and gap reducers along with verified low 

rolling resistance trailer tires (either dual or single-wide). Trailer manufacturers can also 

test trailers using a modified J1321 test method to assess the fuel-saving impact of the 

aerodynamic features. Trailers that meet or exceed the minimum threshold for reduction 

in fuel consumption and that are equipped with SmartWay-verified low rolling resistance 

tires are eligible for SmartWay designation. Information about SmartWay certified 

trailers, the test methods, and verified trailer equipment is at the US EPA SmartWay web 

site, http://www.epa.gov/smartway. 

(b) California AB32

The California requirement to reduce GHG emissions from trailers became 

effective in 2010.415 It requires that all new 2011 model year dry van trailers are 

SmartWay certified or demonstrate a 5 percent aerodynamic and a 1.5 percent tire 

improvement. Compliance is demonstrated through the use of SmartWay certified 

components or a SAE paired-truck test to demonstrate improvements. California is also 

requiring retrofit of existing van trailers phasing in starting in 2011. Information on the 

California program can be found at the California Environmental Protection Agency Air 

Resources Board web site, http://www.arb.ca.gov/cc/hdghg/hdghg.htm.

(6) Why are the Agencies delaying regulation and what are the next steps for 

trailer regulation?

It is the intent of both agencies to take advantage of available and very near-term 

technologies to achieve early reductions in greenhouse gas emissions and fuel 

consumption. As noted above, President Obama requested both agencies to coordinate to 

create a first-ever National Policy to increase fuel efficiency and decrease greenhouse gas 

pollution from medium- and heavy-duty trucks for Model Years 2014-2018. To meet the 

goals within the time frame outlined by the President in his directive, EPA and DOT are 

moving expeditiously to develop these proposed regulations as outlined in today’s 

proposal. 

 

415 California Air Resources Board. http://www.arb.ca.gov/regact/2008/ghghdv08/ghghdv08.htm, accessed 

(date)
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The expertise of each agency’s technical and regulatory staff, along with critical 

input from the SmartWay program, industry and other key stakeholders, make it feasible 

to propose regulations covering commercial medium-duty and heavy-duty trucks within 

this time frame. However, both EPA and NHTSA recognize, along with the NAS, the

diversity and complexity of the trailer industry. There are dozens of trailer types, dozens 

of trailer manufacturing entities, and several diverse trailer end user groups. In addition 

to the challenge of addressing these multiple complexities, unlike many other vehicle 

sectors, this is an industry that has never before been subject to either emissions or fuel 

economy regulation. 

Additionally, since a number of trailer manufacturing entities are small 

businesses, EPA and NHTSA need to allow sufficient time to convene a Small Business 

Regulatory Enforcement Fairness Act (SBREFA) panel to conduct the proper outreach to 

the potentially impacted stakeholders. 

Therefore, EPA and NHTSA propose to follow their proposals for medium-duty

and heavy-duty truck regulations with a proposal for regulating trailers, at a future date to 

be determined after both agencies conduct a more comprehensive assessment of the 

topics discussed in this section. EPA and NHTSA welcome comment on delaying 

proposing trailer regulations and on related topics that might affect the timing of such a 

proposal.

X. Recommendations from the March 2010 NAS Report

A. Overview

One of the most important resources for the agencies in developing the HD 

National Program was the report produced by the National Academy of Sciences in 

response to Congress’ mandate in EISA. Section 108 of EISA states that DOT (by

delegation, NHTSA) must execute an agreement with the NAS “to develop a report 

evaluating MD/HD truck fuel economy standards, including—

(1) an assessment of technologies and costs to evaluate fuel economy for MD/HD 

trucks;

(2) an analysis of existing and potential technologies that may be used practically

to improve MD/HD truck fuel economy;

(3) an analysis of how such technologies may be practicallyintegrated into the 

MD/HD truck manufacturing process;

(4) an assessment of how such technologies may be used to meet fuel economy

standards to be prescribed under 49 U.S.C. § 32902(k); and

(5) associated costs and other impacts on the operation of MD/HD trucks, 

including congestion.
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EISA further states that the NAS must submit the report to DOT, the Senate 

Committee on Commerce, Science, and Transportation, and the House Committee on 

Energy and Commerce not later than one year after the date on which the Secretary

executed the agreement with the NAS. NAS requested and was granted an additional six 

months to complete its report, so based on the date of execution of the ultimate 

agreement, the deadline for the NAS report was determined to be March 2010. 

The National Research Council (NRC) Committee to Assess Fuel Economy 

Technologies for Medium- and Heavy-Duty Vehicles was formed to fulfill the contract 

between NHTSA and the NAS.416 Interpreting the tasks listed in Section 108 of EISA, 

NAS directed the committee to:

 Consider approaches to measuring fuel economy for medium- and heavy-duty

vehicles that would be required for setting standards;

 Assess current and potential technologies and estimate improvements in fuel 

economy for medium-duty and heavy-duty trucks that might be achieved;

 Address how the technologies identified in the task above may be used practically to 

improve medium-duty and heavy-duty truck fuel economy;

 Address how such technologies may be practically integrated into the medium-duty

and heavy-duty truck manufacturing process;

 Assess how such technologies may be used to meet fuel economy standards;

 Discuss the pros and cons of approaches to improving the fuel efficiency of moving 

goods as opposed to setting vehicle fuel economy standards; and

 Identify the potential costs and other impacts on the operation of medium-duty and 

heavy-duty trucks.417

The NAS Report “Technologies and Approaches to Reducing the Fuel 

Consumption of Medium- and Heavy-Duty Vehicles” (“March 2010 NAS Report” or 

“NAS Report”) was delivered to NHTSA in pre-publication form in mid-March 2010, to 

Congress in late March 2010, and was released to the public on March 31, 2010.418 

Although the NAS Report was developed and written in terms of reducing fuel 

consumption, its findings and recommendations apply equally to a program that reduces 

GHG emissions, given the close relationship between the two.

 

416 National Academy of Science, Committee to Assess Fuel Economy Technologies for Medium- and 

Heavy-Duty Vehicles, “Technologies and Approaches to Reducing the Fuel Consumption of Medium- and 

Heavy-Duty Vehicles,” March 2010 (hereafter, “March 2010 NAS Report” or “NAS Report”), at 1-1. 

Available at http://www.nap.edu/catalog.php?record_id=12845 (last accessed June 20, 2010).

417 See Note 416 above, at 1-2.

418 Id.
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B. What were the major findings and recommendations of the March 

2010 NAS Report, and how is the proposed HD National Program 

consistent with them?

The March 2010 NAS Report spanned eight chapters and several hundred pages, 

with dozens of major findings and recommendations. While this preamble refers 

frequently throughout to the various NAS findings and recommendations as it explains 

the HD National Program, this particular section is designed to provide the reader with a 

quick reference guide to the findings and recommendations and the extent to which the 

agencies’ proposed program is consistent with them. The significant majority of NAS’ 

findings and recommendations have been implemented directly by the agencies. 

Generally speaking, to the extent that the proposed HD National Program diverges from 

the NAS recommendations, it is often due to differences in the agencies’ approach as 

compared to NAS’ expectations for a HD regulatory program, which the agencies think 

are necessary and beneficial in order to obtain the greatest GHG and fuel consumption 

reductions as rapidly as possible, and to facilitate the transition for the industry to a more 

holistic regulatory system over a longer timeframe.

Instead of discussing the NAS Report findings and recommendations in the order 

presented in the Report itself, as is done in the NHTSA Study accompanying this NPRM, 

this section divides the NAS findings and recommendations into three categories: 

findings and recommendations with which (1) the HD National Program is consistent; (2) 

the HD National Program is significantly inconsistent; and (3) the HD National Program 

is less-significantly inconsistent.

(1) NAS findings and recommendations with which the proposed HD National 

Program is consistent

(a) What metrics should be employed for regulating fuel consumption/GHG 

emissions?

With the light-duty fuel economy and GHG regulations as a backdrop, the NAS 

committee considered the difference between fuel economy (a measure of how far a 

vehicle will go on a gallon of fuel) and fuel consumption (the inverse measure, of how 

much fuel is consumed in driving a given distance) as potential metrics for MD/HD 

regulations.419 Noting the non-linear nature of fuel economy – e.g., that more fuel can be 

saved by increasing fuel economy from 14 to 16 mpg than from 30 to 32 mpg – and its 

potential to confuse consumers, the committee concluded that fuel economy would not be 

a good metric for judging the fuel efficiency of a vehicle, and stated that it would use fuel 

consumption throughout the report instead.420

 

419 See Note 416 above,at 2-15 through 2-17.

420 Id. at 2-17.
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However, because MD/HD vehicles are designed to carry loads in an efficient and 

timely manner, as opposed to light-duty vehicles which are generally used simply for 

carrying passengers, the committee suggested that normalizing the fuel consumption to 

the payload that the vehicle hauls would be the best way to represent an appropriate 

attribute-based fuel consumption metric.421 The committee identified this metric as 

“Load-Specific Fuel Consumption” or “LSFC,” defined as fuel consumption on a given 

cycle (in gallons/100 miles), divided by payload (in tons).422 The committee thus 

recommended that any HD fuel consumption regulation use LSFC as the metric and be 

based on using an average (or typical) payload based on national data representative of 

the classes and duty cycle of the vehicle.423 The committee noted that standards might 

require different values of LSFC due to the various functions of the vehicle classes, e.g., 

pickup trucks versus utility trucks versus line-haul trucks.424 The committee stated that 

any data reporting or labeling should state an LSFC at specified tons of payload.425

The agencies agree that the appropriate metric for regulating HD vehicle GHG 

emissions and fuel consumption is one tied to the vehicle’s task and reflects the work 

done by the vehicle. Thus, the agencies have employed different metrics in developing 

the proposed standards in this NPRM, as follows:

The metric for HD engines is grams of CO2/brake horsepower-hour (g/bhp-hr) 

and gallons/brake horsepower-hour (gal/bhp-hr), which normalizes CO2 

emissions and fuel consumption based on work done.

The metric for line-haul Class 7 and 8 trucks is grams of CO2/payload ton-mile 

(g/ton-mile) and gallons/payload ton-mile (gal/ton-mile), which normalizes CO2 

emissions and fuel consumption based on the work done in transporting payload.

The metric for vocational (Class 4-8) trucks is also grams of CO2/ton-mile (g/tonmile) and gallons/ton-mile (gal/ton-mile), which normalizes CO2 emissions and 

fuel consumption based on work done.

The metric for Class 2b/3 trucks (and cab-chassis Class 2b/3 trucks and related 

Class 4 trucks) is grams of CO2/mile (g/mi) and gallons/mile (gal/mi)., While 

these metrics are not normalized by payload, standards are based on the work 

done by the vehicles in that the standards are vehicle attribute based and a 

function of payload capacity and towing capacity (and whether two-wheel drive 

or four-wheel drive).

In establishing measurement driving cycles and vehicle load settings, the agencies 

carefully review reviewed available data and selected cycles and vehicle load settings that 

are judged to be most representative of national average use. 

 

421 See Note 416 above, at 2-18, and at 8-18, Recommendation 8-3

422 Id.

423 See Note 416 above . at 2-40, Recommendation 2-1.

424 Id. The committee also stated that regulators should use a common procedure to develop baseline LSFC 

data for various applications, to determine if separate standards are required for different vehicles that have 

a common function.

425 Id.
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Thus, as NAS recommended, the agencies are proposing separate standards with 

different metrics – all based on consideration of the tasks vehicles perform and the work 

they do, which is consistent with the LSFC concept – for different classes of vehicles..

The agencies have no plan to require fuel consumption labeling, or to publish 

values for individual vehicles. Because of the broad range of actual vehicle use, 

including the range of payloads carried, driving cycles and road terrain, and recognizing 

that, for individual vehicles, engines, transmission ratios, final drive ratios and tire sizes 

are selected based on intended use, the agencies judge that a label or published fuel 

consumption value, based on testing under average conditions, would likely not provide 

an accurate assessment of individual vehicle fuel consumption performance, and may be 

misleading. 

(b) Which classes of vehicles should be regulated?

The committee stated that while it may seem expedient to initially focus on those 

classes of vehicles with the largest fuel consumption (i.e., Class 8, Class 6, and Class 2b, 

which together account for approximately 90 percent of fuel consumption of HD 

vehicles), the committee believes that selectively regulating only certain vehicle classes 

would lead to very serious unintended consequences and would compromise the intent of 

the regulation.426 The committee suggested, however, that within vehicle classes, there 

may be certain subclasses of vehicles (e.g., fire trucks) that could be exempt from the 

regulation without creating market distortions.427

The agencies agree that it is crucial to avoid unintended consequences such as 

class shifting, which might occur as a result of regulating only certain classes of trucks. 

Thus, as NAS recommended, the agencies are regulating all Classes 2b through 8 in this 

first round of regulations, with different standards tailored to different groups of vehicles 

to maximize fuel savings and emissions reductions as appropriate for the work that they

perform. In addition, the agencies agree with the NAS recommendation that certain 

subclasses be exempted from regulation and have provided flexibilities that include 

Averaging, Banking and Trading, and exemptions for some off-road vehicles. 

Related to this recommendation, NAS also noted that large OEMs with significant 

engineering capability design and manufacture almost all Class 2b, 3, and 8b vehicles, 

while small companies with limited engineering resources make a significant percentage 

of vehicles in Classes 4 through 8a, although in many cases they buy the complete chassis 

from larger OEMs.428 The committee emphasized that regulators will need to take into 

account the limitations of these smaller companies.429

 

426 Id. at 8-17, Finding 8-1.

427 See Note 416 above.

428 Id., Finding 8-2.

429 Id.
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The agencies agree that the impacts on small manufacturers in Classes 4 through 

8a should be considered in developing HD regulations, and have done so through the 

structure of our standards for those vehicle classes. See Section II in this preamble for a 

fuller discussion. The agencies are proposing to not set standards at this time for engine, 

chassis, and vehicle manufacturers which meet the small business definitions.

(c) What test procedures should be employed for evaluating compliance with 

standards?

The committee emphasized that a certification test method must be highly

accurate, repeatable, and identical to the in-use compliance tests, as is the case with 

current regulation of light-duty vehicles tested on a chassis dynamometer, and for heavyduty engine emission standards tested on engine dynamometers.430

 The committee stated 

that using the process and results from existing engine dynamometer testing for criteria 

emissions to certify fuel economy standards for MD/HD vehicles would build on proven, 

accurate, and repeatable methods, and put less additional administrative burden on the 

industry.

431

 However, the committee cautioned that to account for the fuel consumption 

benefits of hybrid powertrains and transmission technology, the present engine-only tests 

for emissions certification will need to be augmented with other powertrain components 

added to the engine test cell, either as real hardware or as simulated components.432 

Additionally, the vehicle attributes (aero, tires, mass) would need to be accounted for, 

perhaps by using vehicle-specific prescribed loads (via models) in the test cycle, which 

the committee stated would require close cooperation among component manufacturers 

and vehicle manufacturers.433

The committee noted that since there is currently no established federal test 

method for HD vehicle fuel consumption, either empirical testing (whether at the 

component level or up to the whole vehicle level) or simulation modeling or both could 

be used for the characterization and certification of regulated equipment.434 The 

committee cautioned that each approach involves uncertainties that can affect 

certification and compliance, and stressed the need for a pilot regulation program to 

examine the potential for these effects.435

The committee also noted that significant segments of the MD/HD vehicle 

purchasing process are highly consumer-driven, with many engine, transmission, and 

drive axle choice combinations resulting in a wide array of completed vehicles for a 

given vehicle model.436 The committee stressed that from a regulatory standpoint, the 

use of expensive and time-consuming chassis testing on each distinct vehicle variation is 

 

430 Id. at 8-19, Finding 8-8.

431 Id., Finding 8-9.

432 See Note 416 above.

433 Id.

434 Id., Finding 8-10.

435 Id.

436 Id., Finding 8-11.
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impractical.437 However, the committee suggested that by knowing the performance of 

major subcomponents on fuel consumption, it may be practical to demonstrate 

compliance certification with vehicle standards by aggregating the subcomponents into a 

specified virtual vehicle for computers to evaluate fuel consumption of the completed 

vehicle.438

The committee stated that further research will be required to underpin the 

protocol used to measure key input parameters, such as tire rolling resistance and 

aerodynamic drag forces, and to ensure the robustness of simulations for evaluating 

vehicle fuel consumption.439 However, the committee stated, once determined, these 

major components may be assembled through simulation to represent a whole-vehicle 

system, and models benchmarked to reliable data may be used to extend the prediction to 

a variety of vehicle types, by changing bodies (aerodynamic measures), tires, and 

operating weights associated with the powertrains.440

Thus, the committee recommended that the agency consider the use of simulation 

modeling with component test data and additional tested inputs from powertrain tests as a 

way of lowering cost and administrative burdens yet achieving needed accuracy of 

results.441 The committee stated that this is similar to the approach taken in Japan, but 

different in that the program would represent all of the parameters of the vehicle 

(powertrain, aerodynamics, and tires) and relate fuel consumption to the vehicle task.442 

The committee further recommended that the combined vehicle simulation/component 

testing approach be supplemented with tests of complete vehicles for audit purposes.443

The agencies agree that choosing accurate and repeatable test procedures that 

build on existing procedures to the maximum extent will minimize administrative burden 

and be crucial for the success of the program. Thus, as NAS recommended, the agencies 

are proposing chassis dynamometer testing for Class 2b/3 and related trucks, building off 

existing criteria pollutant emissions test programs and manufacturers’ experience with 

light-duty fuel economy test procedures; engine dynamometer testing for HD engines, 

building off existing criteria pollutant emissions test programs; and vehicle simulation

testing for Class 4-8 vocational trucks and Class 7-8 line-haul trucks, which is new for 

this program but which, the agencies believe, minimizes burden while maximizing 

accuracy and repeatability. The agencies have carefully considered measurement 

protocols for key simulation input parameters and have structured the program to reduce 

sensitivity to accuracy and repeatability issues. See Section V in this preamble for a 

fuller discussion. The agencies recognize the importance of continuing work to 

standardize and refine measurement methods and intend to work with industry and 

 

437 See Note 416 above.

438 Id.

439 Id., Finding 8-12.

440 Id.

441 Id., Recommendation 8-4.

442 See Note 416 above.

443 Id.
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technical organizations to improve those measurement methods. The simulation 

program includes inputs for all vehicle parameters that affect fuel consumption, but the 

interface allows manufacturers to enter a limited number of the inputs for this first 

program. The majority of inputs have been preselected by the agencies to represent 

typical vehicle attributes in each regulatory category. The agencies believes this 

approach and the choice of preselected parameters will reduce the potential for 

unintended consequences. The simulation program also uses vehicle loads and driving 

cycles that were selected based on careful consideration of vehicle task, as recommended. 

And finally, testing of complete vehicles for audit purposes has occurred and will 

continue to occur during the comment period, in order to further hone the accuracy of the 

simulation approach. The agencies are thus consistent with NAS’ recommendations with 

respect to test procedures.

The agencies have structured the program to regulate large manufacturers, and as 

such there are fewer regulated entities than the NAS study envisioned. The agencies 

agree with the NAS expectation that a program would require close cooperation among 

component manufacturers and vehicle manufacturers. The agencies believe the regulated 

manufacturers, and their suppliers, have sufficient resources handle this burden, and in 

most cases are already operating with close cooperation.

(d) How should appropriate technologies be determined?

The committee emphasized that technology effectiveness (that is, its fuel 

consumption/emissions reduction potential) is extremely dependent on application (for 

example, a hybrid powertrain applied to a pickup truck versus line-haul tractor) and drive 

cycle (for example, start-stop versus steady-state, variations in load, etc.).

444

 The 

committee also stressed that while some technologies are economically viable now, 

others may require significantly higher fuel costs or valuations of environmental/security 

externalities to make them cost-beneficial.445

The agencies recognize and agree that not all technologies are applicable in the 

same way to all HD trucks and all drive cycles, and that not all technologies are costbeneficial in the timeframe of this rulemaking. The agencies divided the overall HD fleet 

into unique categories in order to group generally similar vehicle types that have 

generally similar uses. For vocational vehicles, where uses and drive cycles are highly 

varied, the agencies have structured the program in a way that should provide benefits 

broadly through the separate regulation of engines and the vehicle (effectively only the 

tires, for this first rulemaking). Measurement of fuel consumption performance in each 

category is based on estimated average drive cycles and vehicle loading for that category. 

Section III discusses these issues in considerable detail.

 

444 Id. at S-9, Finding 4/5/6-1.

445 Id., Finding 4/5/6-2.
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(2) NAS findings and recommendations with which the proposed HD National 

Program is not significantly consistent, and why the agencies have chosen 

a different path

(a) Should the agencies conduct a pilot program?

In briefings to the agencies following the completion of the NAS Report, the 

committee repeatedly stressed its final recommendation over all others: that NHTSA 

should conduct a pilot program before beginning to regulate HD fuel consumption 

officially, and that the pilot program should have these elements:

NHTSA should “Gain experience with certification testing, data gathering, 

compiling and reporting. There needs to be a concerted effort to determine the 

accuracy and repeatability of all the test methods and simulation strategies that 

will be used with any proposed regulatory standards and a willingness to fix 

issues that are found.”

NHTSA should “Gather data on fuel consumption from several representative 

fleets of vehicles. This should continue to provide a real-world check on the 

effectiveness of the regulatory design on the fuel consumption of trucking fleets 

in various parts of the marketplace and various regions of the country.”

The committee’s fundamental concern was that given that HD fuel consumption 

had never previously been regulated, and given the scope of the regulatory system that 

the committee had envisioned, serious unintended consequences could occur if NHTSA 

did not build in extra time to conduct a pilot program, with negative effects on the 

regulated industry and on fuel savings.

With regard to NAS’ first concern, that NHTSA must gain experience with 

certification testing, data gathering, compiling and reporting before initiating a HD fuel 

consumption regulatory system, the agencies believe that the proposed HD National 

Program may avoid the risks that NAS identified because it is based in large part on 

existing test protocols and reporting systems. The agencies’ proposed certification and 

compliance programs for Classes 2b/3, for example, employ the same testing procedures 

and reporting systems as for light-duty CAFE and GHG regulations, so both the agencies 

and the manufacturers who are regulated already have much experience with testing, data 

collection, and reporting.446 For HD engine standard certification and compliance, 

similarly, the agencies’ proposed systems rely on engine testing identical to that already 

used by EPA and manufacturers for criteria emissions regulations, and also vehicle 

modeling. 

While it is true that the vehicle testing for Class 7-8 line-haul tractors and Class 4-

8 vocational trucks is new, the agencies believe that the proposed modeling approach will 

likely avoid NAS’ concerns due to its degree of simplification, relative to what NAS 

considered. The agencies are not requiring the same level of whole vehicle simulation 

 

446 See Section II of this preamble.
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for certification and compliance as envisioned by NAS – instead, while manufacturers 

will take real-world measurements for each component or system attribute, those 

measurements will all be placed into “bins,” and the bin value (which will be 

representative and pre-defined) will be the value actually employed in the modeling 

system. The agencies believe that this approach has considerable merit in the timeframe 

of this rulemaking to initiate the HD National Program for several reasons. First, since 

not all test methodologies have been firmly established, pre-defined bin values help to 

mitigate measurement uncertainty that might otherwise allow manufacturers to game the 

testing protocol. While there may be some loss of accuracy due to use of bin values 

rather than direct measurement values, and while the agencies will have to track vehicle 

model inputs carefully to ensure that manufacturers are not gaming the bins themselves, 

the agencies believe that the proposed levels of stringency should compensate for these 

risks. And second, waiting for a pilot program to gain additional experience with testing, 

data gathering, and reporting would delay our ability to get fuel efficiency and emissions 

improvements as soon as possible. If a pilot program was initiated as early as MY 2014, 

and it took one year to collect information to inform rulemaking and an additional year 

for finalizing a rule that, by statute, would provide 4 year lead time, the first regulated 

year would be 2020. The costs of waiting to regulate officially, in terms of fuel savings 

and emissions reductions, would likely outweigh the potential benefits of gaining more 

experience, especially given the structure of the first phase of the proposed HD National 

Program.

With regard to NAS’ second concern, that NHTSA must gather data on fuel 

consumption from representative fleets as a real-world check on the effectiveness of the 

regulatory design, the agencies believe that the proposed HD National Program will be 

much better able to avoid unintended consequences than the regulatory system that NAS 

envisioned because we do not propose to regulate the entire vehicle as a single system. 

The agencies believe that the proposed HD National Program approach has considerable 

merit for the timeframe of this rulemaking because it does not regulate transmission and 

final drive ratios and tire sizes, and thus allows manufacturers and customers to continue 

to specify these attributes in order to optimize them for specific vehicle use. This reduces 

the need for our regulatory program to define the real-world drive cycle (in terms of 

speed, load, grade, and altitude) exactly correctly for every individual vehicle, as 

compared to NAS’ envisioned approach. Additionally, by expressly requiring 

improvements in engine efficiency, the proposed HD National Program will require all 

vehicles to become more efficient regardless of their intended use. Although the agencies 

will not document exact real-world measured improvements in fuel efficiency/emissions 

reductions, the program will achieve percentage improvements that may be 

approximately estimated. Furthermore, while program benefits may be lower than the 

full potential envisioned by NAS if fleets choose to optimize powertrain specifications 

for purposes other than fuel efficiency, the agencies believe that achieving improvements 

sooner outweighs the less-certain later benefits of undertaking an initial pilot program as 

suggested by NAS.
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(b) Should the agencies regulate trailers in the first phase of the HD National 

Program?

The NAS committee recommended that NHTSA include trailers in its regulatory

program to achieve maximum possible fuel efficiency improvements, and also to provide 

an incentive to manufacturers to optimize the tractor/trailer interface.447 The committee 

noted that commercial trailers are produced by a separate group of about 12 major 

manufacturers that are not associated with truck manufacturers.448 The committee stated 

that trailers represent an important opportunity for fuel consumption reduction, and can 

benefit from improvements in aerodynamics and tires.449

For purposes of the proposed HD National Program, the agencies intend to 

consider regulation of trailers in the next phase of rulemaking and not in this initial phase. 

As the committee suggested, regulating trailers is very challenging due to the nature of 

the trailer industry, with many small manufacturers and very long vehicle lifespans. 

However, since trailer production volume is low, the agencies project that their impact on 

fuel consumption and emissions reduction will be much smaller than for regulating 

engines and tractors, as the agencies intend to do in the first phase of the HD National 

Program. The agencies are thus deferring trailer regulations until a subsequent phase.450

(c) Should the agencies include in their baseline analysis the effect of the California 

Air Resources Board SmartWay mandate?

The committee found that the legislation passed by California requiring tractortrailer combinations to be SmartWay certified will have a significant impact on the 

number of vehicles in the United States that are specified with fuel-efficient technologies 

beginning in 2010.451 The agencies are using a 2010 baseline with an estimate of national 

sales mix that includes the sales of SmartWay tractors. The California trailer mandate is 

not reflected in either the baseline or the proposal estimates because this proposal does 

not regulate trailers. Therefore the agencies believe the estimated program for this 

proposal account for the effects of the California SmartWay mandate 

(d) Should the agencies’ aerodynamic drag test method include varying yaw angles?

The committee recommended that a HD fuel consumption regulation should 

require that aerodynamic features be evaluated on a wind-averaged basis that takes into 

account the effects of yaw, and that tractor and trailer manufacturers should be required 

to certify their drag coefficient results using a common industry standard.452 The 

 

447 See Note 416 above, at 8-18, Recommendation 8-2.

448 Id., Finding 8-3.

449 Id.

450 See Section II of this preamble.

451 See Note 416 above, at 3-16, Finding 3-4.

452 Id. at 5-63, Recommendation 5-1.
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committee stated that yaw-induced drag can be accurately measured only in a wind 

tunnel.453

The agencies are not implementing this recommendation in the first phase of the 

proposed HD National Program. The current lack of common wind tunnel facilities 

precludes using a single aerodynamic test method at the outset of the program, which will 

begin with EPA’s GHG regulations in 2014. Instead, the program will allow 

manufacturers to continue to use whatever aerodynamic test method they currently use. 

This will ease administrative burden, but the agencies recognize that it will create 

variability in measured aerodynamic values. To address this, the agencies are employing 

a bin system for aerodynamic drag values, and varying values will be grouped in the 

same bin.454 The agencies anticipate investigating varying yaw angles in a subsequent 

rulemaking for a future phase of the HD National Program.

(e) Should the agencies complete an economic/payback analysis prior to beginning to 

regulate, in order to avoid unintended consequences?

The committee recommended that NHTSA’s study (which it expected would 

precede the NPRM) include a careful economic/payback analysis based on fuel usage by 

application and different fuel price scenarios, including operating and maintenance 

costs.455 The committee stated that standards that differentially affect the capital and 

operating costs of different vehicle classes can cause purchase of vehicles that are not 

optimized for particular operating conditions, and cautioned that the complexity of truck 

use and the variability of duty cycles increase the probability of these unintended 

consequences.456

The agencies have included in this NPRM and in the DRIA a draft 

economic/payback analysis based on industry average operating cycles and expectations 

for ongoing maintenance costs. The agencies seek comment on the assumptions and 

analysis presented in Section VIII of the preamble and Chapter 9 of the DRIA. In 

particular, the agencies request comment on the ability of these average assumptions to 

reflect payback periods for the industry as a whole and what if any changes the agencies 

should make in the analyses for the final rulemaking consistent with the 

recommendations of the NAS. 

 

453 Id. at 2-40, Finding 2-4.

454 See Section II of this preamble.

455 See Note 416 above at 6-46, Recommendation 6-1.

456 Id. at 6-47, Finding 6-12.
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(f) How should the agencies account for indirect effects and unintended consequences 

as a result of the proposed HD National Program?

The committee stressed the need of regulators to consider a number of effects in 

the development of any proposals to regulate HD fuel consumption,457 specifically fleet 

turnover impacts and pre-buy effects;458 the rebound effect;

459 vehicle class shifting

effects;460 environmental co-benefits and costs;461 congestion;

462 safety;463 and

incremental weight impacts.

464

 While the committee did not examine any of these effects 

in depth, it stated that it believed that a rebound effect likely exists, and that estimates of 

fuel savings from regulatory standards will be somewhat misestimated if the rebound 

effect is not considered.465

In response, while the agencies have initiated analyses of these unintended 

consequences, they have not all been completed in time to be incorporated into this 

NPRM. The NAS committee itself noted the lack of available information on these 

effects, especially as compared to the wealth of information available for light-duty fuel 

economy and GHG regulatory analysis. Much of this work must simply be done from 

scratch. The agencies have included estimates of the rebound effect in this NPRM and 

DRIA,466 but we hope to have analyses of other effects available for the final rule.

(3) NAS findings and recommendations with which the proposed HD National 

Program is not entirely consistent, and why the agencies have chosen a 

different path

(a) Should the agencies regulate final-stage manufacturers?

The committee recommended that NHTSA regulate the final stage manufacturers 

since they have the greatest control over the design of the vehicle and its major 

subsystems that affect fuel consumption.467 However, this recommendation was 

predicated on a regulatory system that regulated the whole vehicle as a single unit.

The agencies are proposing to regulate final-stage manufacturers for Class 2b/3 

trucks, but not for Class 4-8 vocational trucks or for Class 7-8 line-haul tractors. While 

 

457 Id. at 6-46, Finding 6-9.

458 Id., Finding 6-10.

459 Id., Finding 6-11.

460 Id. at 6-47, Finding 6-12. Of particular concern is the potential for fleets to purchase vehicles classified 

for purposes of our regulations as “vocational” trucks, in order to avoid the significant capital costs 

associated with the addition of aero improvements, weight reductions, and an APU, and then convert them 

to a tractor. The agencies believe we have addressed this potential loophole, as discussed in Section [XX].

461 See Note 416 above, Finding 6-13.

462 Id., Finding 6-14.

463 Id., Findings 6-16 and 6-17.

464 Id., Finding 6-16.

465 Id., Finding 6-11.

466 See Section VIII of this preamble and Chapter 9 of the draft RIA.

467 See Note 416 above at 8-17, Recommendation 8-1.
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choosing not to regulate the whole vehicle as a single unit for this first phase of the HD 

National Program means that the agencies’ initial rule will not achieve the maximum 

potential benefits sought by NAS through its approach, the agencies believe that the 

benefits of implementing regulations more quickly outweigh the drawbacks. 

Additionally, the proposed HD National Program approach eliminates dealing with 

thousands of final-stage manufacturers in the first phase of regulation, many of whom are 

small businesses and could be unduly affected by these regulations in this time frame.

(b) What should the agencies do about component testing data?

The committee recommended that, in order to ensure consistent data from 

component manufacturers for certification and compliance modeling, NHTSA establish a 

standardized test protocol and safeguards for the confidentiality of that component 

data.468 To that end, the committee recommended that NHTSA implement as soon as 

possible a major engineering contract to analyze several actual vehicles in several 

applications and develop an approach to component testing data in conjunction with 

vehicle simulation modeling to arrive at LSFC data for these vehicles.469

The agencies believe that these concerns are less of an issue with the proposed 

HD National Program. As discussed above, test protocols for Class 2b/3 test protocols 

are already standardized, and both the agencies and the manufacturers know what to 

expect in the data. Additionally, for Classes 3 to 8, we know what to expect in the engine 

testing and data, and since the vehicle testing uses a simplified bin approach, even though

there may be some loss of accuracy and potential for gaming, the agencies believe that 

this is the fastest way to get regulations implemented while addressing the problem of a 

lack of standardized test protocol/safeguards for data. The agencies anticipate addressing 

this issue on an ongoing basis in subsequent rulemakings for later phases of the HD 

National Program.

(c) How should the agencies validate a combined vehicle simulation/component 

testing compliance approach?

The committee recommended that actual vehicles should also be tested by

appropriate full-scale test procedures to confirm actual LSFC values and reductions 

measured with fuel consumption reduction technologies, as compared to the more costeffective fleet certification approach.470

As discussed above, the agencies believe that this is less of a concern for the 

proposed HD National Program since the agencies are not proposing to regulate the 

whole vehicle as a single system. The agencies will continue to conduct tests of complete 

vehicles for audit purposes as the HD National Program develops and as time and 

resources allow.

 

468 Id.

469 Id. at 8-20, Recommendation 8-5.

470 Id. at 8-19, Recommendation 8-4.
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(d) How should the agencies consider HD regulation in Europe and Japan?

The committee suggested that the HD fuel consumption regulations in Japan, and 

those under consideration and study by the European Commission, provide valuable input 

and experience to the U.S. plans. The committee stated that in Japan the complexity of 

HD vehicle configurations and duty cycles was determined to lend itself to the use of 

computer simulation as a cost-effective means to calculate fuel efficiency, and that the 

EC studies so far indicate plans to develop and use simulations in their expected 

regulatory system. The committee noted that Japan is not using extensive full-vehicle 

testing in the certification process, despite the fact that its HD vehicle manufacturing 

diversity is less than in the U.S., with relatively few HD vehicle manufacturers and no 

independent engine companies.

The agencies have reviewed the Japanese and planned EC HD regulations to the 

extent possible given the time frame for this rulemaking and considered those 

approaches. However, the proposed HD National Program differs from the Japanese and 

planned EC HD programs. The agencies agree that international harmonization in HD 

fuel consumption/GHG regulations is desirable and expect harmonization may increase 

over time, given the global presence of many HD vehicle manufacturers.

(e) How much engineering work needs to be done before HD fuel consumption 

regulations can be implemented?

The committee stated that significant engineering work is needed to produce a 

regulatory approach that produces cost effective and accurate results, which can provide 

meaningful data to vehicle purchasers.471 While the agencies emphasize that much 

engineering work has already been undertaken in support of this proposed HD National 

Program, we believe, as discussed above, that the need for engineering work perceived by 

NAS is reduced somewhat based on the structure of the proposed program. Since the 

agencies are not regulating transmission ratios, final drive ratio, and tire size; since the 

agencies are not regulating the complete vehicle as a single unit and instead separating 

the engine from the vehicle; and since the agencies are building off of existing regulatory

programs for light-duty vehicles and HD criteria pollutant emissions wherever possible, 

we believe that we have created a solid basis for the HD National Program that will 

address NAS’ concerns in this regard.

XI. Statutory and Executive Order Reviews

(1) Executive Order 12866: Regulatory Planning and Review

Under section 3(f)(1) of Executive Order (EO) 12866 (58 FR 51735, October 4, 

1993), this action is an “economically significant regulatory action” because it is likely to 

have an annual effect on the economy of $100 million or more. Accordingly, the 

 

471 Id. at 8-20, Finding 8-13.
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agencies submitted this action to the Office of Management and Budget (OMB) for 

review under EO 12866 and any changes made in response to OMB recommendations 

have been documented in the docket for this action.

NHTSA is also subject to the Department of Transportation’s Regulatory Policies 

and Procedures. These proposed rules are also significant within the meaning of the 

DOT Regulatory Policies and Procedures. E.O. 12866 additionally requires NHTSA to 

submit this action to OMB for review and document any changes made in response to 

OMB recommendations.

In addition, the agencies prepared an analysis of the potential costs and benefits 

associated with this action. This analysis is contained in the Draft Regulatory Impact 

Analysis, which is available in the docket for this proposal and at the docket internet 

address listed under ADDRESSES above.

(2) National Environmental Policy Act

[NHTSA will provide]

(3) Paperwork Reduction Act

The information collection requirements in this proposal have been submitted for 

approval to the Office of Management and Budget (OMB) under the Paperwork 

Reduction Act, 44 U.S.C. 3501 et seq. The Information Collection Request (ICR) 

document prepared by EPA has been assigned EPA ICR number 2394.01.

The Agency proposes to collect information to ensure compliance with the 

provisions in this proposal. This includes a variety of testing, reporting and 

recordkeeping requirements for vehicle manufacturers. Section 208(a) of the Clean Air 

Act requires that vehicle manufacturers provide information the Administrator may

reasonably require to determine compliance with the regulations; submission of the 

information is therefore mandatory. We will consider confidential all information 

meeting the requirements of section 208(c) of the Clean Air Act. 

It is estimated that this collection affects approximately 35 engine and vehicle 

manufacturers. The information that is subject to this collection is collected whenever a 

manufacturer applies for a certificate of conformity. Under Section 206() of the Clean 

Air Act (42 USC 7521), a manufacturer must have a certificate of conformity before a 

vehicle or engine can be introduced into commerce. 

The burden to the manufacturers affected by this proposal has a range based on 

the number of engines and vehicles a manufacturer produces. The total estimated burden 

associated with this proposal is 23,500 hours annually (see Error! Reference source not 

found.Error! Reference source not found.). This estimated burden for engine and 

vehicle manufacturers is a total estimate for new reporting requirements. Burden means 

the total time, effort, or financial resources expended by persons to generate, maintain, 

retain, or disclose or provide information to or for a Federal agency. This includes the 

time needed to review instructions; develop, acquire, install, and utilize technology and 
394 of 541

systems for the purposes of collecting, validating, and verifying information, processing 

and maintaining information, and disclosing and providing information; adjust the 

existing ways to comply with any previously applicable instructions and requirements; 

train personnel to be able to respond to a collection of information; search data sources; 

complete and review the collection of information; and transmit or otherwise disclose the 

information.

Table XI-1 Burden for Reporting and Recordkeeping Requirements

Number of Affected Vehicle Manufacturers 35

Annual Labor Hours for Each Manufacturer to Prepare and Submit 

Required Information

Varies 

Total Annual Information Collection Burden 23,500 

Hours 

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 40 CFR are listed in 40 CFR part 9.

To comment on the Agency’s need for this information, the accuracy of the 

provided burden estimates, and any suggested methods for minimizing respondent 

burden, including the use of automated collection techniques, EPA has established a 

public docket for this proposal, which includes this ICR, under Docket ID number EPAHQ-OAR-2010-0162. Submit any comments related to the ICR for this proposal to 

EPA and OMB. See ‘Addresses’ section at the beginning of this notice for where to 

submit comments to EPA. Send comments to OMB at the Office of Information and 

Regulatory Affairs, Office of Management and Budget, 725 17th Street, NW, 

Washington, DC 20503, Attention: Desk Office for EPA. Since OMB is required to 

make a decision concerning the ICR between 30 and 60 days after [Insert date of 

publication in the FEDERAL REGISTER], a comment to OMB is best assured of 

having its full effect if OMB receives it by [Insert date 30 days after publication in the 

FEDERAL REGISTER]. The final rules will respond to any OMB or public comments 

on the information collection requirements contained in this proposal.

(4) Regulatory Flexibility Act

(a) Overview

The Regulatory Flexibility Act (RFA) generally requires an agency to prepare a 

regulatory flexibility analysis of any rule subject to notice and comment rulemaking 

requirements under the Administrative Procedure Act or any other statute unless the 

agency certifies that the rule will not have a significant economic impact on a substantial 

number of small entities. Small entities include small businesses, small organizations, 

and small governmental jurisdictions.

For purposes of assessing the impacts of this proposal on small entities, small 

entity is defined as: (1) a small business as defined by the Small Business 
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Administration’s (SBA) regulations at 13 CFR 121.201 (see Table XI-2 below); (2) a 

small governmental jurisdiction that is a government of a city, county, town, school 

district or special district with a population of less than 50,000; and (3) a small 

organization that is any not-for-profit enterprise which is independently owned and 

operated and is not dominant in its field.

Table XI-2 provides an overview of the primary SBA small business categories 

included in the heavy-duty engine and vehicle sector:

Table XI-2: Primary SBA Small Business Categories in the Heavy-Duty Engine and Vehicle Sector

Industry a

Defined as small 

entity by SBA if less 

than or equal to:

NAICS Codesb

Motor vehicle manufacturers, engine 

and truck manufacturers

1000 employees 336111

336112

336120

Commercial importers of vehicles and 

vehicle components

$7.0 million annual 

revenue

811112

811198

541514

Alternative fuel vehicle converters

Sec. 42 –Wholesale trade is not 

applicable to government procurement 

of supplies

500 employees

1000 employees

336111

336112

422720

454312

541514

541690

811198

Truck trailer manufacturers 500 employees 336212

Notes:

a Heavy-duty engine and vehicle entities that qualify as small businesses would not be subject to these

proposed rules. We are deferring action on small vehicle entities, and we intend to address these entities in 

a future rule.

b North American Industrial Classification System

(b) Summary of Potentially Affected Small Entities

The agencies have not conducted an Initial Regulatory Flexibility Analysis for the 

proposal because we are proposing to certify that these rules would not have a significant 

economic impact on a substantial number of small entities. The agencies are proposing 

to defer standards for manufacturers meeting SBA’s definition of small business as 

described in 13 CFR 121.201 due to the short lead time to develop this proposal, the 

extremely small fuel savings and emissions contribution of these entities, and the 

potential need to develop a program that would be structured differently for them (which 

would require more time). The agencies would instead consider appropriate fuel 
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consumption and GHG standards for these entities as part of a future regulatory action. 

This includes small entities in several distinct categories of businesses for heavy-duty 

engines and vehicles: chassis manufacturers, combination tractor manufacturers, and

alternative fuel engine converters. 

Based on preliminary assessment, the agencies have identified a total of about 17 

engine manufacturers, 3 complete pickup truck and van manufacturers, 11 combination 

tractor manufacturers and 43 heavy duty chassis manufacturers. Of these, about 15

entities fit the Small Business Administration (SBA) criterion of a small business. There 

are approximately three engine converters, two tractor manufacturers, and ten heavy-duty 

chassis manufacturers in the heavy-duty engine and vehicle market that are small 

businesses. (No major heavy-duty engine manufacturers, heavy duty chassis 

manufacturers, or tractor manufacturers meet the small-entity criteria as defined by

SBA). The agencies estimate that these small entities comprise less than 0.35 percent of 

the total heavy-duty vehicle sales in the U.S., and therefore the proposed deferment will 

have a negligible impact on the fuel consumption and GHG emissions reductions from 

the proposed standards. 

To ensure that the agencies are aware of which companies would be deferred, the 

agencies are proposing that such entities submit a declaration to the agencies containing a 

detailed written description of how that manufacturer qualifies as a small entity under the 

provisions of 13 CFR 121.201. Some small entities, such as heavy duty tractor and 

chassis manufacturers, are not currently covered under criteria pollutant motor vehicle 

emissions regulations. Small engine entities are currently covered by a number of EPA 

motor vehicle emission regulations, and they routinely submit information and data on an 

annual basis as part of their compliance responsibilities. Because such entities are not 

automatically exempted from other EPA regulations for heavy-duty engines and vehicles, 

absent such a declaration, EPA would assume that the entity was subject to the 

greenhouse gas control requirements in this GHG proposal. The declaration to the 

agencies would need to be submitted at time of either engine or vehicle emissions 

certification under the Heavy Duty Highway Engine program. The agencies expect that 

the additional paperwork burden associated with completing and submitting a small 

entity declaration to gain deferral from the proposed GHG and fuel consumption 

standards would be negligible and easily done in the context of other routine submittals to 

the agencies. However, the agencies have accounted for this cost with a nominal estimate 

included in the Information Collection Request completed under the Paperwork 

Reduction Act. Additional information can be found in the Paperwork Reduction Act 

discussion in Section XI. (3) Paperwork Reduction Act. Based on this, the agencies are

proposing to certify that the rules would not have a significant economic impact on a 

substantial number of small entities. The agencies continue to be interested in the 

potential impacts of the proposal on small entities and welcome comments on issues 

related to such impacts.

(c) Conclusions

We therefore certify that this proposal will not have a significant economic impact 

on a substantial number of small entities. 
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(5) Unfunded Mandates Reform Act

Title II of the Unfunded Mandates Reform Act of 1995 (UMRA), P.L. 104-4, 

establishes requirements for Federal agencies to assess the effects of their regulatory

actions on State, local, and tribal governments and the private sector. Under section 202 

of the UMRA, the agencies generally must prepare a written statement, including a costbenefit analysis, for proposed and final rules with “Federal mandates” that may result in 

expenditures to State, local, and tribal governments, in the aggregate, or to the private 

sector, of $100 million or more in any one year. Before promulgating a rule for which a 

written statement is needed, section 205 of the UMRA generally requires the agencies to 

identify and consider a reasonable number of regulatory alternatives and adopt the least 

costly, most cost-effective or least burdensome alternative that achieves the objectives of 

the rule. The provisions of section 205 do not apply when they are inconsistent with 

applicable law. Moreover, section 205 allows the agencies to adopt an alternative other 

than the least costly, most cost-effective or least burdensome alternative if the 

Administrator (of either agency) publishes with the final rule an explanation why that 

alternative was not adopted. 

Before the agencies establish any regulatory requirements that may significantly

or uniquely affect small governments, including tribal governments, they must have 

developed under section 203 of the UMRA a small government agency plan. The plan 

must provide for notifying potentially affected small governments, enabling officials of 

affected small governments to have meaningful and timely input in the development of 

EPA and NHTSA regulatory proposals with significant Federal intergovernmental 

mandates, and informing, educating, and advising small governments on compliance with 

the regulatory requirements. 

This proposal contains no Federal mandates (under the regulatory provisions of 

Title II of the UMRA) for State, local, or tribal governments. The rules impose no 

enforceable duty on any State, local or tribal governments. The agencies have

determined that this proposal contains no regulatory requirements that might significantly 

or uniquely affect small governments. The agencies have determined that this proposal 

contains a Federal mandate that may result in expenditures of $100 or more for the 

private sector in any one year. As summarized above in Section I.D, the agencies expect 

this proposal to cost industry approximately $8 billion over the lifetime of the vehicles 

produced in the first five years of the program, and in that same time yield approximately

$49 billion in benefits. The agencies believe that the proposal represents the least costly, 

most cost-effective approach to achieve the statutory requirements of the rules. Section 

VIII.L, above, explains why the agencies believe that the fuel savings that would result 

from this proposal would lead to lower prices economy-wide, improving U.S. 

international competitiveness. The costs and benefits associated with the proposal are 

discussed in more detail above in Section VIII and in the Draft Regulatory Impact 

Analysis, as required by the UMRA.
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(6) Executive Order 13132 (Federalism)

This action does not have federalism implications. It will not have substantial 

direct effects on the States, on the relationship between the national government and the 

States, or on the distribution of power and responsibilities among the various levels of 

government, as specified in Executive Order 13132. This proposal would apply to 

manufacturers of motor vehicles and not to state or local governments. Thus, Executive 

Order 13132 does not apply to this action. Although section 6 of Executive Order 13132 

does not apply to this action, the agencies did consult with representatives of state 

governments in developing this action. 

In the spirit of Executive Order 13132, and consistent with EPA and NHTSA 

policy to promote communications between the agencies and State and local 

governments, the agencies specifically solicit comment on this proposed action from 

State and local officials.

(7) Executive Order 13175 (Consultation and Coordination with Indian Tribal 

Governments)

These proposed rules do not have tribal implications, as specified in Executive 

Order 13175 (65 FR 67249, November 9, 2000). This proposal will be implemented at 

the Federal level and impose compliance costs only on vehicle manufacturers. Tribal 

governments would be affected only to the extent they purchase and use regulated 

vehicles. Thus, Executive Order 13175 does not apply to this proposal. The agencies

specifically solicit additional comment on this proposal from tribal officials.

(8) Executive Order 13045: “Protection of Children from Environmental 

Health Risks and Safety Risks”

This action is subject to EO 13045 (62 FR 19885, April 23, 1997) because it is an 

economically significant regulatory action as defined by EO 12866, and the agencies

believe that the environmental health or safety risk addressed by this action may have a 

disproportionate effect on children. A synthesis of the science and research regarding 

how climate change may affect children and other vulnerable subpopulations is contained 

in the Technical Support Document for Endangerment or Cause or Contribute Findings 

for Greenhouse Gases under Section 202(a) of the Clean Air Act, which can be found in 

the public docket for this proposal.

472

 A summary of the analysis is presented below.

With respect to GHG emissions, the effects of climate change observed to date 

and projected to occur in the future include the increased likelihood of more frequent and 

intense heat waves. Specifically, EPA’s analysis of the scientific assessment literature has 

determined that severe heat waves are projected to intensify in magnitude, frequency, and 

 

472 U.S. EPA. (2009). Technical Support Document for Endangerment or Cause or Contribute Findings for 

Greenhouse Gases under Section 202(a) of the Clean Air Act. Washington, D.C.: U.S. EPA.. Docket EPAHQ-OAR-2009-0472-11292
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duration over the portions of the U.S. where these events already occur, with potential 

increases in mortality and morbidity, especially among the young, elderly, and frail. EPA 

has estimated reductions in projected global mean surface temperatures as a result of 

reductions in GHG emissions associated with the standards proposed in this action 

(Section II). Children may receive benefits from reductions in GHG emissions because 

they are included in the segment of the population that is most vulnerable to extreme 

temperatures.

For non-GHG pollutants, EPA has determined that climate change is expected to 

increase regional ozone pollution, with associated risks in respiratory infection, 

aggravation of asthma, and premature death. The directional effect of climate change on 

ambient PM levels remains uncertain. However, disturbances such as wildfires are 

increasing in the U.S. and are likely to intensify in a warmer future with drier soils and 

longer growing seasons. PM emissions from forest fires can contribute to acute and 

chronic illnesses of the respiratory system, particularly in children, including pneumonia, 

upper respiratory diseases, asthma and chronic obstructive pulmonary diseases.

The public is invited to submit comments or identify peer-reviewed studies and 

data that assess effects of early life exposure to the pollutants addressed by this proposal. 

(9) Executive Order 13211 (Energy Effects)

This proposal is not a “significant energy action” as defined in Executive Order 

13211, “Actions Concerning Regulations That Significantly Affect Energy Supply, 

Distribution, or Use” (66 FR 28355 (May 22, 2001)) because it is not likely to have a 

significant adverse effect on the supply, distribution, or use of energy. In fact, this 

proposal has a positive effect on energy supply and use. Because the GHG emission 

standards proposed today result in significant fuel savings, this proposal encourages more 

efficient use of fuels. Therefore, we have concluded that this proposal is not likely to 

have any adverse energy effects. Our energy effects analysis is described above in 

Section VIII.H.

(10) National Technology Transfer Advancement Act

Section 12(d) of the National Technology Transfer and Advancement Act of 1995 

(“NTTAA”), Public Law No. 104-113, 12(d) (15 U.S.C. 272 note) directs the agencies to 

use voluntary consensus standards in its regulatory activities unless to do so would be 

inconsistent with applicable law or otherwise impractical. Voluntary consensus standards 

are technical standards (e.g., materials, specifications, test methods, sampling procedures, 

and business practices) that are developed or adopted by voluntary consensus standards 

bodies. NTTAA directs the agencies to provide Congress, through OMB, explanations 

when the agencies decide not to use available and applicable voluntary consensus 

standards.

For CO2, N2O, and CH4 emissions and fuel consumption from heavy duty 

engines, the agencies are proposing to collect data over the same tests that are used for 
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the Heavy Duty Highway Engine program. This will minimize the amount of testing 

done by manufacturers, since manufacturers are already required to run these tests. 

For CO2, N2O, and CH4 emissions and fuel consumption from complete pickup 

trucks and vans, the agencies are proposing to collect data over the same tests that are 

used for the Heavy Duty Highway Engine program and California Air Resources Board. 

This will minimize the amount of testing done by manufacturers, since manufacturers are 

already required to run these tests.

For CO2 emissions and fuel consumption from heavy duty combination tractors 

and vocational trucks, the agencies are proposing to collect data through the use of a 

simulation model instead of a full-vehicle chassis dynamometer testing. This will 

minimize the amount of testing done by manufacturers. EPA's compliance assessment 

tool is based upon well-established engineering and physics principals that are the basis 

of general academic understanding in this area, and the foundation of any dynamic 

vehicle simulation model, including the models cited by ICCT in its study473 and cited by

the NAS committee in its published report.

474

 Therefore, the EPA's compliance 

assessment tool satisfies the description of a consensus. For the evaluation of tire rolling 

resistance input to the model, EPA is proposing to use the ISO 28580 test, a voluntary

consensus methodology. EPA is proposing to allow several alternatives for the 

evaluation of aerodynamics which allows the industry to continue to use their own 

evaluation tools because EPA does not know of a single consensus standard available for 

heavy duty truck aerodynamic evaluation.

For air conditioning standards, EPA is proposing to use a consensus methodology

developed by the Society of Automotive Engineers (SAE). 

(11) Executive Order 12898: Federal Actions to Address Environmental 

Justice in Minority Populations and Low-Income Populations

Executive Order (EO) 12898 (59 FR 7629 (Feb. 16, 1994)) establishes federal 

executive policy on environmental justice. Its main provision 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 and low-income populations in the United States. 

With respect to GHG emissions, EPA has determined that these proposed rules

will not have disproportionately high and adverse human health or environmental effects 

on minority or low-income populations because it increases the level of environmental 

protection for all affected populations without having any disproportionately high and 

adverse human health or environmental effects on any population, including any minority 

 

473 ICCT. ICCT Evaluation of Vehicle Simulation Tools. 2009. Last viewed on August 5, 2010 at 

http://www.theicct.org/information/reports/icct_evaluation_of_vehicle_simulation_tools

474 NAS Study. Page S-14.
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or low-income population. The reductions in CO2 and other GHGs associated with the 

standards will affect climate change projections, and EPA has estimated reductions in 

projected global mean surface temperatures (Section VI). Within communities 

experiencing climate change, certain parts of the population may be especially

vulnerable; these include the poor, the elderly, those already in poor health, the disabled, 

those living alone, and/or indigenous populations dependent on one or a few resources. 475 

In addition, the U.S. Climate Change Science Program476 stated as one of its conclusions: 

“The United States is certainly capable of adapting to the collective impacts of climate 

change. However, there will still be certain individuals and locations where the adaptive 

capacity is less and these individuals and their communities will be disproportionally

impacted by climate change.” Therefore, these specific sub-populations may receive 

benefits from reductions in GHGs. 

For non-GHG co-pollutants such as ozone, PM2.5, and toxics, EPA has concluded 

that it is not practicable to determine whether there would be disproportionately high and 

adverse human health or environmental effects on minority and/or low income 

populations from this proposal. 

The public is invited to submit comments or identify peer-reviewed studies and 

data that assess effects of early life exposure to the pollutants addressed by this proposal. 

XII. Statutory Provisions and Legal Authority

A. EPA

Statutory authority for the vehicle controls proposed today is found in section 202 

(a) (which authorizes standards for emissions of pollutants from new motor vehicles 

which emissions cause or contribute to air pollution which may reasonably be anticipated 

to endanger public health or welfare), 202 (d), 203-209, 216, and 301 of the Clean Air 

Act, 42 U.S.C. 7521 (a), 7521 (d), 7522, 7523, 7524, 7525, 7541, 7542, 7543, 7550, and 

7601.

B. NHTSA

Statutory authority for the fuel consumption standards proposed today is found in 

section 103 (which authorizes a fuel efficiency improvement program, designed to 

achieve the maximum feasible improvement to be created for commercial medium- and 

heavy-duty on-highway vehicles and work trucks, to include appropriate test methods, 

 

475 U.S. EPA. (2009). Technical Support Document for Endangerment or Cause or Contribute Findings for 

Greenhouse Gases under Section 202(a) of the Clean Air Act. Washington, D.C.: U.S. EPA. Docket EPAHQ-OAR-2009-0472-11292

476 CCSP (2008) Analyses of the effects of global change on human health and welfare and human systems. 

A Report by the U.S. Climate Change Science Program and the Subcommittee on Global Change Research. 

[Gamble, J.L. (ed.), K.L. Ebi, F.G. Sussman, T.J. Wilbanks, (Authors)]. U.S. Environmental Protection 

Agency, Washington, DC, USA.
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measurement metrics, standards, and compliance and enforcement protocols that are 

appropriate, cost-effective and technologically feasible) of the Energy Independence and 

Security Act of 2007, 49 U.S.C. 32902(k).