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

Federal RegisterMar 28, 2022

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Parts 2, 59, 60, 80, 85, 86, 87, 600, 1027, 1030, 1033, 1036, 1037, 1039, 1042, 1043, 1045, 1048, 1051, 1054, 1060, 1065, 1066, 1068, and 1090

[EPA-HQ-OAR-2019-0055; FRL-7165-03-OAR]

RIN 2060-AU41

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

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Proposed rule.

SUMMARY:

The Environmental Protection Agency (EPA) is proposing a rule that would reduce air pollution from highway heavy-duty vehicles and engines, including ozone, particulate matter, and greenhouse gases. This proposal would change the heavy-duty emission control program—including the standards, test procedures, useful life, warranty, and other requirements—to further reduce the air quality impacts of heavy-duty engines across a range of operating conditions and over a longer period of the operational life of heavy-duty engines. Heavy-duty vehicles and engines are important contributors to concentrations of ozone and particulate matter and their resulting threat to public health, which includes premature death, respiratory illness (including childhood asthma), cardiovascular problems, and other adverse health impacts. This proposal would reduce emissions of nitrogen oxides and other pollutants. In addition, this proposal would make targeted updates to the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 program, proposing that further GHG reductions in the MY 2027 timeframe are appropriate considering lead time, costs, and other factors, including market shifts to zero-emission technologies in certain segments of the heavy-duty vehicle sector. We also propose limited amendments to the regulations that implement our air pollutant emission standards for other sectors (

e.g.,

light-duty vehicles, marine diesel engines, locomotives, various types of nonroad engines, vehicles, and equipment).

DATES:

Comments:

Written comments must be received on or before May 13, 2022. Under the Paperwork Reduction Act (PRA), comments on the information collection provisions are best assured of consideration if the Office of Management and Budget (OMB) receives a copy of your comments on or before April 27, 2022.

Public Hearing:

EPA plans to hold a virtual public hearing on April 12, 2022. An additional session may be held on April 13, 2022. Please refer to Participation in Virtual Public Hearing in the

SUPPLEMENTARY INFORMATION

section for additional information on the public hearing.

ADDRESSES:

You may send comments, identified by Docket ID No. EPA-HQ-OAR-2019-0055, by any of the following methods:

•

Federal eRulemaking Portal: https://www.regulations.gov/ (our preferred method)

. Follow the online instructions for submitting comments.

•

Email: a-and-r-Docket@epa.gov

. Include Docket ID No. EPA-HQ-OAR-2019-0055 in the subject line of the message.

•

Mail:

U.S. Environmental Protection Agency, EPA Docket Center, OAR, Docket EPA-HQ-OAR-2019-0055, Mail Code 28221T, 1200 Pennsylvania Avenue NW, Washington, DC 20460.

•

Hand Delivery or Courier (by scheduled appointment only):

EPA Docket Center, WJC West Building, Room 3334, 1301 Constitution Avenue NW, Washington, DC 20004. The Docket Center's hours of operations are 8:30 a.m.-4:30 p.m., Monday-Friday (except Federal Holidays).

Instructions:

All submissions received must include the Docket ID No. for this rulemaking. Comments received may be posted without change to

https://www.regulations.gov/

, including any personal information provided. For detailed instructions on sending comments and additional information on the rulemaking process, see the “Public Participation” heading of the

SUPPLEMENTARY INFORMATION

section of this document. Out of an abundance of caution for members of the public and our staff, the EPA Docket Center and Reading Room are open to the public by appointment only to reduce the risk of transmitting COVID-19. Our Docket Center staff also continues to provide remote customer service via email, phone, and webform. Hand deliveries and couriers may be received by scheduled appointment only. For further information on EPA Docket Center services and the current status, please visit us online at

https://www.epa.gov/dockets

Public Hearing.

EPA plans to hold a virtual public hearing for this rulemaking. Please refer to

Participation in Virtual Public Hearing

in the

SUPPLEMENTARY INFORMATION

section for additional information.

FOR FURTHER INFORMATION CONTACT:

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

nelson.brian@epa.gov

SUPPLEMENTARY INFORMATION:

A. Public Participation

Written Comments

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2019-0055, at

https://www.regulations.gov

(our preferred method), or the other methods identified in the

ADDRESSES

section. Once submitted, comments cannot be edited or removed from the docket. The EPA may publish any comment received to its public docket. Do not submit electronically any information you consider to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Multimedia submissions (audio, video, etc.) must be accompanied by a written comment. The written comment is considered the official comment and should include discussion of all points you wish to make. The EPA will generally not consider comments or comment contents located outside of the primary submission (

i.e.,

on the web, cloud, or other file sharing system). For additional submission methods, the full EPA public comment policy, information about CBI or multimedia submissions, and general guidance on making effective comments, please visit

https://www.epa.gov/dockets/commenting-epa-dockets

Due to public health concerns related to COVID-19, the EPA Docket Center and Reading Room are open to the public by appointment only. Our Docket Center staff also continues to provide remote customer service via email, phone, and webform. Hand deliveries or couriers will be received by scheduled appointment only. For further information and updates on EPA Docket Center services, please visit us online at

https://www.epa.gov/dockets

The EPA continues to carefully and continuously monitor information from the Centers for Disease Control and Prevention (CDC), local area health departments, and our Federal partners so that we can respond rapidly as conditions change regarding COVID-19.

Participation in Virtual Public Hearing

Please note that because of current CDC recommendations, as well as state and local orders for social distancing to

limit the spread of COVID-19, EPA cannot hold in-person public meetings at this time.

The EPA plans to hold a virtual public hearing on April 12, 2022. An additional session may be held on April 13, 2022. This hearing will be held using Zoom. In order to attend the virtual public hearing, all attendees (including those who will not be presenting verbal testimony) must register in advance. EPA will begin registering speakers for the hearing upon publication of this document in the

Federal Register

. To register, please use the registration link that will be available on the EPA rule web page once registration begins:

https://www.epa.gov/regulations-emissions-vehicles-and-engines/proposed-rule-and-related-materials-control-air-1

. A separate registration form must be submitted for each person attending the hearing.

The last day to register to speak at the hearing will be five working days before the first public hearing date. The EPA will post a general agenda for the hearing with the order of speakers at:

https://www.epa.gov/regulations-emissions-vehicles-and-engines/proposed-rule-and-related-materials-control-air-1

. This agenda will be available no later than two working days before the first public hearing date.

In order to allow everyone to be heard, EPA is limiting verbal testimony to three minutes per person. Speakers will not be able to share graphics via the virtual public hearing. Speakers will be able to request an approximate speaking time as part of the registration process, with preferences considered on a first-come, first-served basis. EPA also recommends submitting the text of oral comments as written comments to the rulemaking docket.

EPA will make every effort to follow the schedule as closely as possible on the day of the hearing; however, please plan for the hearings to run either ahead of schedule or behind schedule.

The EPA may ask clarifying questions during the oral presentations, but will not respond to the presentations at that time. Written statements and supporting information submitted during the comment period will be considered with the same weight as oral comments and supporting information presented at the public hearing.

Please note that any updates made to any aspect of the hearing will be posted online at:

https://www.epa.gov/regulations-emissions-vehicles-and-engines/proposed-rule-and-related-materials-control-air-1

. While the EPA expects the hearing to go forward as described here, please monitor our website or contact Tuana Phillips, (202)-565-0074,

phillips.tuana@epa.gov

to determine if there are any updates. The EPA does not intend to publish a document in the

Federal Register

announcing updates.

If you require the services of a translator or special accommodations such as audio description, please identify these needs when you register for the hearing or by contacting Tuana Phillips at (202)-565-0074,

phillips.tuana@epa.gov

. EPA may not be able to arrange accommodations without advance notice.

B. General Information

Does this action apply to me?

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

NAICS codes

NAICS title

326199

All Other Plastics Product Manufacturing.

332431

Metal Can Manufacturing.

335312

Motor and Generator Manufacturing.

336111

Automobile Manufacturing.

336112

Light Truck and Utility Vehicle Manufacturing.

336120

Heavy Duty Truck Manufacturing.

336211

Motor Vehicle Body Manufacturing.

336212

Truck Trailer Manufacturing.

336213

Motor Home Manufacturing.

336411

Manufacturers of new aircraft.

336412

Manufacturers of new aircraft engines.

333618

Other Engine Equipment Manufacturing.

336999

All Other Transportation Equipment Manufacturing.

423110

Automotive and Other Motor Vehicle Merchant Wholesalers.

447110

Gasoline Stations with Convenience Stores.

447190

Other Gasoline Stations.

454310

Fuel dealers.

811111

General Automotive Repair.

811112

Automotive Exhaust System Repair.

811198

All Other Automotive Repair and Maintenance.

NAICS Association. NAICS & SIC Identification Tools. Available online:

https://www.naics.com/search

This table is not intended to be exhaustive, but rather provides a guide for readers regarding entities likely to be regulated by this action. This table lists the types of entities that EPA is now aware could potentially be regulated by this action. Other types of entities not listed in the table could also be regulated. To determine whether your entity is regulated by this action, you should carefully examine the applicability criteria found in Sections XII and XIII of this preamble. If you have questions regarding the applicability of this action to a particular entity, consult the person listed in the

FOR FURTHER INFORMATION CONTACT

section.

What action is the agency taking?

The Environmental Protection Agency (EPA) is proposing a rule that would reduce air pollution from highway heavy-duty vehicles and engines. This proposal would change the heavy-duty emission control program—including the standards, test procedures, regulatory useful life, emission-related warranty, and other requirements—to further reduce the air quality impacts of heavy-duty engines across a range of operating conditions and over a longer period of the operational life of heavy-duty engines. Heavy-duty vehicles and engines are important contributors to concentrations of ozone and particulate matter and their resulting threat to public health, which includes premature death, respiratory illness (including childhood asthma), cardiovascular problems, and other adverse health impacts. This proposal would reduce emissions of nitrogen oxides and other pollutants. In addition, this proposal would make targeted updates to the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 program, proposing that further GHG reductions in the MY 2027 timeframe are appropriate considering lead time, costs, and other factors, including market shifts to zero-emission technologies in certain segments of the heavy-duty vehicle sector.

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

Section 202(a)(1) of the Clean Air Act requires the EPA to set emission standards for air pollutants from new motor vehicles or new motor vehicle engines, which the Administrator has found cause or contribute to air pollution that may endanger public health or welfare. See Sections I.A.4, I.F, and XIV of this preamble for more information on the agency's authority for this action.

What are the incremental costs and benefits of this action?

We compare total monetized health benefits to total costs associated with the proposed Options 1 and 2 in Section IX. Our results show that annual benefits of the proposed Option 1 would be larger than the annual costs in 2045, a year when the program would be fully implemented and when most of the regulated fleet would have turned over,

with annual net benefits of $9 and $31 billion assuming a 3 percent discount rate, and net benefits of $8 and $28 billion assuming a 7 percent discount rate.

Annual benefits would also be larger than annual costs in 2045 for the proposed Option 2, although net benefits would be lower than from the proposed Option 1 (net benefits of proposed Option 2 would be $6 and $23 billion at a 3 percent discount rate, and net benefits of $5 and 21 billion at a 7 percent discount rate). See Section VIII for more details on the net benefit estimates. For both the proposed Options 1 and 2, benefits also outweigh the costs when expressed in present value terms and as equalized annual values.

The range of benefits and net benefits reflects a combination of assumed PM

2.5

and ozone mortality risk estimates and selected discount rate.

Did EPA conduct a peer review before issuing this action?

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

https://cfpub.epa.gov/si/

Table of Contents

ES. Executive Summary

A. Purpose of the Regulatory Action

B. Overview of the Regulatory Action

C. Summary of the Major Provisions in the Regulatory Action

D. Projected Emission Reductions, Air Quality Improvements, Costs, and Benefits

E. Summary of Specific Requests for Comments

I. Introduction

A. Brief Overview of the Heavy-Duty Truck Industry

B. History of Emission Standards for Heavy-Duty Engines and Vehicles

C. Petitions to EPA for Additional NO

Emissions Control

D. California Heavy-Duty Highway Low NO

Program Development

E. Advance Notice of Proposed Rulemaking

F. EPA Statutory Authority for the Proposal

G. Basis of the Proposed Standards

II. Need for Additional Emissions Control

A. Background on Pollutants Impacted by This Proposal

B. Health Effects Associated With Exposure to Pollutants Impacted by This Proposal

C. Environmental Effects Associated With Exposure to Pollutants Impacted by This Proposal

III. Proposed Test Procedures and Standards

A. Overview

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

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

D. Summary of Spark-Ignition Heavy-Duty Engine Exhaust Emission Standards and Test Procedures

E. Summary of Spark-Ignition Heavy-Duty Vehicle Refueling Emission Standards and Test Procedures

IV. Compliance Provisions and Flexibilities

A. Regulatory Useful Life

B. Ensuring Long-Term In-Use Emissions Performance

C. Onboard Diagnostics

D. Inducements

E. Certification Updates

F. Durability Testing

G. Averaging, Banking, and Trading

H. Early Adoption Incentives

I. Compliance Options for Generating NO

Emission Credits From Electric Vehicles

J. Fuel Quality

K. Other Flexibilities Under Consideration

V. Program Costs

A. Technology Package Costs

B. Operating Costs

C. Program Costs

VI. Estimated Emission Reductions From the Proposal and Alternatives

A. Emission Inventory Methodology

B. Estimated Emission Reductions From the Proposed Criteria Pollutant Program

C. Estimated Emission Reductions From the Alternatives Analyzed

D. Evaluating Emission Impacts of Electric Vehicles in the Proposed Emission Inventory Baseline

VII. Air Quality Impacts of the Proposed Rule

A. Ozone

B. Particulate Matter

C. Nitrogen Dioxide

D. Carbon Monoxide

E. Air Toxics

F. Visibility

G. Nitrogen Deposition

H. Demographic Analysis of Air Quality

VIII. Benefits of the Program

IX. Comparison of Benefits and Costs

A. Methods

B. Results

X. Economic Impact Analysis

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

B. Employment Impacts

XI. Targeted Updates to the HD GHG Phase 2 Heavy-Duty Greenhouse Gas Emissions Program

A. Background on Heavy-Duty Greenhouse Gas Emission Standards

B. What has changed since we finalized the HD GHG Phase 2 rule?

C. Proposed Changes to HD GHG Phase 2 CO

Standards for Targeted Subcategories

D. HD GHG Phase 2 Advanced Technology Credits for CO

Emissions

E. Emissions and Cost Impacts of Proposed Revised MY 2027 CO

Emission Standards

F. Summary of Proposed Changes to HD GHG Phase 2

XII. Other Amendments

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

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

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

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

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

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

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

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

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

J. Locomotives (40 CFR Part 1033)

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

L. Heavy-Duty Compression-Ignition Engines (40 CFR Part 86)

XIII. Executive Orders Reviews

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

B. Paperwork Reduction Act (PRA)

C. Regulatory Flexibility Act (RFA)

D. Unfunded Mandates Reform Act (UMRA)

E. Executive Order 13132: Federalism

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

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

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

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

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

XIV. Statutory Provisions and Legal Authority

Executive Summary

A. Purpose of the Regulatory Action

The Environmental Protection Agency (EPA) is proposing a multipollutant rule to further reduce air pollution from heavy-duty engines and vehicles across the United States, including ozone and particulate matter (PM). In addition, as part of this rulemaking we are proposing

targeted updates to the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 program (HD GHG Phase 2). This proposed rulemaking builds on and improves the existing emission control program for on-highway heavy-duty engines and vehicles. This proposal is pursuant to EPA's authority under the Clean Air Act to regulate air pollutants emitted from mobile sources. The proposal is also consistent with Executive Order (E.O.) 14037, which directed EPA to consider setting new oxides of nitrogen (NO

) emission standards and updating the existing GHG emissions standards for heavy-duty engines and vehicles.

2 3

In this proposed action, EPA is co-proposing two regulatory options for new NO

standards: Proposed Option 1 and proposed Option 2. As discussed in Section B.1 of this Executive Summary and throughout this preamble, we request comment on the options presented, as well as the full range of options between them.

President Joseph Biden. Executive Order on Strengthening American Leadership in Clean Cars and Trucks. 86 FR 43583, August 10, 2021.

Oxides of nitrogen (NO

) refers to nitric oxide (NO) and nitrogen dioxide (NO

Heavy-duty (HD) engines operating across the U.S. emit NO

and other pollutants that contribute to ambient levels of ozone, PM, and NO

. These pollutants are linked to premature death, respiratory illness (including childhood asthma), cardiovascular problems, and other adverse health impacts. Data show that heavy-duty engines are important contributors to concentrations of ozone and PM

2.5

and their resulting threat to public health.

Zawacki et al, 2018. Mobile source contributions to ambient ozone and particulate matter in 2025. Atmospheric Environment, Vol 188, pg 129-141. Available online:

https://doi.org/10.1016/j.atmosenv.2018.04.057

Davidson et al, 2020. The recent and future health burden of the U.S. mobile sector apportioned by source. Environmental Research Letters. Available online:

https://doi.org/10.1088/1748-9326/ab83a8

The proposed rulemaking would change key provisions of the heavy-duty emission control program—including the standards, test procedures, regulatory useful life, emission-related warranty, and other requirements; the two regulatory options (proposed Options 1 and 2) would result in different numeric levels of the standards and lengths of useful life and warranty periods. The proposed Options 1 and 2 and the range between them provide the numeric values for these key provisions that we focus on for this proposal. Together, the key provisions in the proposal would further reduce the air quality impacts of heavy-duty engines across a range of operating conditions and over a longer period of the operational life of heavy-duty engines (see Section I.B for an overview of the proposed program). The requirements in the proposed Option 1 and the proposed Option 2 would lower emissions of NO

and other air pollutants (PM, hydrocarbons (HC), air toxics, and carbon monoxide (CO)) beginning as early as model year (MY) 2027. The emission reductions from both the proposed Option 1 and the proposed Option 2 would increase over time as more new, cleaner vehicles enter the fleet.

We estimate that if finalized as proposed, the proposed Option 1 would reduce NO

emissions from heavy-duty vehicles in 2040 by more than 50 percent; by 2045, a year by which most of the regulated fleet would have turned over, heavy-duty NO

emissions would be more than 60 percent lower than they would have been without this action. Our estimates show proposed Option 2 would reduce heavy-duty NO

emissions in 2045 by 47 percent (see Section I.D for more information on our projected emission reductions from proposed Option 1 or 2). These emission reductions would result in air quality improvements in ozone and PM

2.5

; we estimate that in 2045, the proposed Option 1 would result in total annual monetized ozone- and PM

2.5

-related benefits of $12 and $33 billion at a 3 percent discount rate, and $10 and $30 billion at a 7 percent discount rate. In the same calendar year, proposed Option 2 would result in total annual monetized ozone- and PM

2.5

-related benefits of $9 and $26 billion at a 3 percent discount rate, and $8 and $23 billion at a 7 percent discount (see Section VIII for discussion on quantified and monetized health impacts). Given the analysis we present in this proposal, we currently believe that Option 1 may be a more appropriate level of stringency as it would result in a greater level of achievable emission reduction for the model years proposed, which is consistent with EPA's statutory authority under Clean Air Act section 202(a)(3). These emission reductions would result in widespread decreases in ambient concentrations of pollutants such as ozone and PM

2.5

. These widespread projected air quality improvements would play an important role in addressing concerns from states, local communities, and Tribal governments about the contributions of heavy-duty engines to air quality challenges they face such as meeting their obligations to attain or continue to meet National Ambient Air Quality Standards (NAAQS), and to reduce other human health and environmental impacts of air pollution.

In addition to further reducing emissions of NO

and other ozone and PM

2.5

precursors, as part of this rulemaking we are proposing targeted updates to the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 program (HD GHG Phase 2).

The proposed updates would apply to certain CO

standards for MYs 2027 and later trucks that are appropriate considering lead time, costs, and other factors, including market shifts to zero-emission technologies in certain segments of the heavy-duty vehicle sector. The proposed updates are intended to balance further incentivizing zero and near-zero emissions vehicle development with ensuring that the standards achieve an appropriate fleet-wide level of CO

emissions reductions.

81 FR at 73478 (October 25, 2016).

1. Industry Overview

Heavy-duty highway vehicles (also referred to as “trucks” in this preamble) range from vocational vehicles that support local and regional construction, refuse collection, and delivery work to long-haul tractor-trailers that move freight cross-country. This diverse array of vehicles is categorized into weight classes based on gross vehicle weight ratings (GVWR) that span Class 2b trucks and vans greater than 8,500 lbs GVWR through Class 8 long-haul tractors and other commercial vehicles that exceed 33,000 lbs GVWR.

These vehicles are primarily powered by diesel-fueled, compression-ignition (CI) engines, although gasoline-fueled, spark-ignition (SI) engines are common in the lighter weight classes, and

smaller numbers of alternative fuel engines (

e.g.,

liquified petroleum gas, compressed natural gas) are found in the heavy-duty fleet. Vehicles powered by electricity, either in the form of battery electric vehicles (BEVs) or fuel cell electric vehicles (FCEVs) are also increasingly entering the heavy-duty fleet. The operational characteristics of some commercial applications (

e.g.,

delivery vehicles) can be similar across several vehicle weight classes, allowing a single engine, or electric power source in the case of BEVs and FCEVs, to be installed in a variety of vehicles. For instance, engine specifications needed for a Class 4 parcel delivery vehicle may be similar to the needs of a Class 5 mixed freight delivery vehicle or a Class 6 beverage truck. Performance differences needed to operate across this range of vehicles can be achieved through adjustments to chassis-based systems (

e.g.,

transmission, cooling system) external to the engine.

This proposed rulemaking includes revised criteria pollutant standards for engine-certified Class 2b through 8 heavy-duty engines and vehicles; this proposal also includes revised GHG standards for Class 4 through 8 vehicles. Class 2b and 3 vehicles with GVWR between 8,500 and 14,000 pounds are primarily commercial pickup trucks and vans and are sometimes referred to as “medium-duty vehicles”. The majority of Class 2b and 3 vehicles are chassis-certified vehicles, and EPA intends to include them in a future combined light-duty and medium-duty rulemaking action, consistent with E.O, 14037, Section 2a. Heavy-duty engines and vehicles are also used in nonroad applications, such as construction equipment; nonroad heavy-duty engines and vehicles are not the focus of this proposal. See Section I for more discussion on the spectrum of heavy-duty vehicles and how they relate to the proposed rule. As outlined in Section C of this Executive Summary and detailed in Section XII, this proposal also includes limited amendments to regulations that implement our air pollutant emission standards for other industry sectors, including light-duty vehicles, light-duty trucks, marine diesel engines, locomotives, and various types of nonroad engines, vehicles, and equipment.

2. The Need for Additional Emission Control of NO

and Other Pollutants From Heavy-Duty Engines

Across the U.S., NO

emissions from heavy-duty engines are important contributors to concentrations of ozone and PM

2.5

and their resulting health effects.

8 9

Heavy-duty engines will continue to be one of the largest contributors to mobile source NO

emissions nationwide in the future, representing 32 percent of the mobile source NO

emissions in calendar year 2045.

Furthermore, it is estimated that heavy-duty engines would represent 89 percent of the onroad NO

inventory in calendar year 2045.

Reducing NO

emissions is a critical part of many areas' strategies to attain and maintain the ozone and PM NAAQS; many state and local agencies anticipate challenges in attaining the NAAQS, maintaining the NAAQS in the future, and/or preventing nonattainment (see Section II). Some nonattainment areas have already been “bumped up” to higher classifications because of challenges in attaining the NAAQS.

Zawacki et al, 2018. Mobile source contributions to ambient ozone and particulate matter in 2025. Atmospheric Environment, Vol 188, pg 129-141. Available online:

https://doi.org/10.1016/j.atmosenv.2018.04.057

Davidson et al, 2020. The recent and future health burden of the U.S. mobile sector apportioned by source. Environmental Research Letters. Available online:

https://doi.org/10.1088/1748-9326/ab83a8

U.S. Environmental Protection Agency (2021). 2016v1 Platform.

https://www.epa.gov/air-emissions-modeling/2016v1-platform

Han, Jaehoon. Memorandum to the Docket EPA-HQ-OAR-2019-0055: “MOVES Modeling-Related Data Files (MOVES Code, Input Databases and Runspecs) for the Proposed Heavy-Duty 2027 Standards”. February 2022.

For example, in September 2019 several 2008 ozone nonattainment areas were reclassified from moderate to serious, including Dallas, Chicago, Connecticut, New York/New Jersey and Houston, and in January 2020, Denver. The 2008 NAAQS for ozone is an 8-hour standard with a level of 0.075 ppm, which the 2015 ozone NAAQS lowered to 0.070 ppm.

In addition, emissions from heavy-duty engines can significantly affect individuals living near truck freight routes. Based on a study EPA conducted of people living near truck routes, an estimated 72 million people live within 200 meters of a truck freight route (see discussion in Section II.B.7). Relative to the rest of the population, people of color and those with lower incomes are more likely to live near truck routes (see Sections II.B and VII.H for additional discussion on our analysis of environmental justice impacts of this proposal). This population includes children, and in addition, childcare facilities and schools can be in close proximity to freight routes.

Kingsley, S., Eliot, M., Carlson, L. et al. Proximity of US schools to major roadways: a nationwide assessment. J Expo Sci Environ Epidemiol 24, 253-259 (2014).

https://doi.org/10.1038/jes.2014.5

Clean Air Act section 202(a)(3)(A) requires EPA to set emission standards for NO

, PM, HC, and CO that reflect the greatest degree of emission reduction achievable through the application of technology that will be available for the model year to which such standards apply. Although heavy-duty engines have become much cleaner over the last decade, catalysts and other technologies have evolved such that harmful air pollutants can be reduced even further.

Heavy-duty emissions that affect local and regional populations are attributable to several engine operating modes and processes. Specifically, the operating modes and processes projected to contribute the most to the heavy-duty NO

emission inventory in 2045 are medium-to-high load (36 percent), low-load (28 percent), and aging (24 percent) (

i.e.,

deterioration and mal-maintenance of the engine's emission control system) (see Section VI for more information on projected inventory contributions from each operating mode or process). These data suggest that medium- and high-load operating conditions continue to merit concern, while also showing that opportunities for significant additional emission reductions and related air quality improvements can be achieved through provisions that encourage emission control under low-load operation and throughout an engine's operational life. Our approach for provisions that address these aspects of the emission inventory is outlined below and described in more detail in sections that follow.

As described in Section III, the standards in proposed Options 1 and 2 would reduce emissions during a broader range of operating conditions that span nearly all in-use operation. The standards in proposed Options 1 and 2 are based on technology improvements which have become available over the 20 years since the last major rule was promulgated to address emissions of NO

, PM, HC, and CO (hereafter referred to as “criteria pollutants”) and toxic pollutants from heavy-duty engines. As further detailed in Section III, available data indicate that emission levels demonstrated for certification are not achieved under the broad range of real-world operating conditions.

14 15 16 17

In fact, less than ten percent of the data collected during a typical test while the vehicle is operated on the road is subject to EPA's in-use, on-the-road emission standards.

These testing data further show that NO

emissions from heavy-duty diesel vehicles are high during many periods of vehicle operation that are not subject to current on-the-road emission standards. For example, “low-load” engine conditions occur when a vehicle operates in stop-and-go traffic or is idling; these low-load conditions can result in exhaust temperature decreases that then lead to the diesel engine's selective catalytic reduction (SCR)-based emission control system becoming less effective or ceasing to function. Test data collected as part of EPA's manufacturer-run in-use testing program indicate that this low-load operation could account for more than half of the NO

emissions from a

vehicle during a typical workday.

Similarly, heavy-duty SI engines also operate in conditions where their catalyst technology becomes less effective, resulting in higher levels of air pollutants; however, unlike CI engines, it is sustained medium-to-high load operation where emission levels are less certain.

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

Sandhu, Gurdas, et al. “Identifying Areas of High NO

Operation in Heavy-Duty Vehicles”. 28th CRC Real-World Emissions Workshop, March 18-21, 2018.

Sandhu, Gurdas, et al. “In-Use Emission Rates for MY 2010+ Heavy-Duty Diesel Vehicles”. 27th CRC Real-World Emissions Workshop, March 26-29, 2017.

As noted in Section C of this Executive Summary and discussed in Section III, testing engines and vehicles while they are operating over the road without a defined duty cycle is referred to as “off-cycle” testing; as detailed in Section III, we are proposing new off-cycle test procedures and standards as part of this rulemaking.

Heavy-duty CI engines are currently subject to off-cycle standards that are not limited to specific test cycles, but we use the term “on-the-road” here for readability.

Sandhu, Gurdas, et al. “Identifying Areas of High NO

Operation in Heavy-Duty Vehicles”. 28th CRC Real-World Emissions Workshop, March 18-21, 2018.

As noted in this Section A.2 of the Executive Summary, deterioration and mal-maintenance of the engine's emission control system is also projected to result in NO

emissions that would represent a substantial part of the HD inventory in 2045. To address this problem, as part of our comprehensive approach, both proposed Options 1 and 2 include longer regulatory useful life and emission-related warranty requirements that would maintain emission control through more of the operational life of heavy-duty vehicles (see Section IV for more discussion on the proposed useful life and warranty requirements).

Reducing NO

emissions from heavy-duty vehicles would address health and environmental issues raised by state, local, and Tribal agencies in their comments on the Advance Notice of Proposed Rule (ANPR).

In addition to concerns about meeting the ozone and PM

2.5

NAAQS, they expressed concerns about environmental justice, regional haze, and damage to terrestrial and aquatic ecosystems. They mentioned the impacts of NO

emissions on numerous locations, such as the Chesapeake Bay, Narragansett Bay, Long Island Sound, Joshua Tree National Park and the surrounding Mojave Desert, the Adirondacks, and other areas. Tribes and agencies commented that NO

deposition into lakes is harmful to fish and other aquatic life forms on which they depend for subsistence livelihoods. They also commented that regional haze and increased rates of weathering caused by pollution are of particular concern and can damage culturally significant archeological sites.

The Agency published an ANPR on January 21, 2020 to present EPA's early thinking on this rulemaking and solicit feedback from stakeholders to inform this proposal (85 FR 3306).

3. The Historic Opportunity for Clean Air Provided by Zero-Emission Vehicles

We are at the early stages of a significant transition in the history of the heavy-duty on-highway sector—a shift to zero-emission vehicle (ZEV) technologies. This change is underway and presents an opportunity for significant reductions in heavy-duty vehicle emissions. Major trucking fleets, manufacturers and U.S. states have announced plans to transition the heavy-duty fleet to zero-emissions technology, and over just the past few years we have seen the early introduction of zero-emission technology into a number of heavy-duty vehicle market segments.

Executive Order 14037 identifies three potential regulatory actions for EPA to consider: (1) This proposed rule for heavy-duty vehicles for new criteria pollutant standards and strengthening of the Model Year 2027 GHG standards; (2) a separate rulemaking to establish more stringent criteria and GHG emission standards for medium-duty vehicles for Model Year 2027 and later (in combination with light-duty vehicles); and (3) a third rulemaking to establish new GHG standards for heavy-duty vehicles for Model Year 2030 and later. This strategy will establish the EPA regulatory path for the future of the heavy-duty vehicle sector, and in each of these actions EPA will consider the critical role of ZEVs in enabling stringent emission standards.

In addition to the proposed standards and requirements for NO

and other air pollutant emissions, we are also proposing targeted revisions to the already stringent HD GHG Phase 2 rulemaking, which EPA finalized in 2016.

The HD GHG Phase 2 program includes GHG emission standards tailored to certain regulatory vehicle categories in addition to heavy-duty engines including: Combination tractors; vocational vehicles; and heavy-duty pickup trucks and vans. The HD GHG Phase 2 program includes progressively more stringent CO

emission standards for HD engines and vehicles; these standards phase in starting in MY 2021 through MY 2027. The program built upon the GHG Phase 1 program promulgated in 2011, which set the first-ever GHG emission standards for heavy-duty engines and trucks.

81 FR 73478 (October 25, 2016). Note that the HD GHG Phase 2 program also includes coordinated fuel efficiency standards established by the U.S. Department of Transportation through the National Highway Traffic Safety Administration, and those standards were established in a joint rulemaking process with EPA.

76 FR 57106, September 15, 2011.

When the HD GHG Phase 2 rule was promulgated in 2016, we established the Phase 2 GHG standards and advanced technology incentives on the premise that electrification of the heavy-duty market was unlikely to occur in the timeframe of the program. However, several factors have arisen since the adoption of Phase 2 that have changed our outlook for heavy-duty electric vehicles. First, the heavy-duty market has evolved such that in 2021, there are a number of manufacturers producing fully electric heavy-duty vehicles in a number of applications. Second, the State of California has adopted an Advanced Clean Trucks program that includes a manufacturer sales requirement for zero-emission truck sales, specifically that “manufacturers who certify Class 2b-8 chassis or complete vehicles with combustion engines would be required to sell zero-emission trucks as an increasing percentage of their annual California sales from 2024 to 2035.”

Finally, other states have signed a Memorandum of Understanding establishing goals to increase the heavy-duty electric vehicle market.

We are proposing that further GHG reductions in the MY 2027 timeframe are appropriate considering lead time, costs, and other factors, including these developments to zero-emission technologies in certain segments of the heavy-duty vehicle sector. We discuss the impacts of these factors on the heavy-duty market in Section XI. As outlined in Section I.B and detailed in Section XI, we are proposing to increase the stringency of the existing MY 2027 standards for many of the vocational vehicle and tractor subcategories, specifically those where we project early introduction of ZEVs. We are also considering whether it would be appropriate in the final rule to increase the stringency of the standards even more than what we propose for MYs 2027-2029, including the potential for progressively more stringent CO

standards across these three model years. Progressively strengthening the stringency of the standards for model years 2028 and 2029 could help smooth the transition to ambitious greenhouse gas standards for the heavy-duty sector starting as soon as model year 2030. We believe there is information and data that could support higher projected penetrations of HD ZEVs in the MY 2027 to 2029 timeframe and we request comment and additional supporting information and data on higher penetration rates, which could serve as the basis for the increase in the stringency of the CO

standards for specific Phase 2 vehicle subcategories. For example, what information and data are available that

would support HD ZEV penetration rates of 5 percent or 10 percent (or higher) in this timeframe, and in what HD vehicle applications and categories. We are also requesting comment on an aspect of the HD GHG Phase 2 advanced technology incentive program.

CARB. “Notice of Decision: Advanced Clean Truck Regulation.” June 2020. Available online at:

https://ww3.arb.ca.gov/regact/2019/act2019/nod.pdf

Fifteen states and one district sign Multi-State MOU.

https://www.nescaum.org/documents/multistate-truck-zev-governors-mou-20200714.pdf

EPA has heard from a number of stakeholders urging EPA to put in place policies to rapidly advance ZEVs in this current rulemaking, and to establish standards requiring 100 percent of all new heavy-duty vehicles be zero-emission no later than 2035. The stakeholders state that accelerating ZEV technologies in the heavy-duty market is necessary to prioritize environmental justice in communities that are impacted by freight transportation and already overburdened by pollution.

One policy EPA has been asked to consider is the establishment of a ZEV sales mandate (

i.e.,

a nationwide requirement for manufacturers to produce a portion of their new vehicle fleet as ZEVs). EPA is not proposing in this action to establish a heavy-duty ZEV mandate. EPA in this action is considering how the development and deployment of ZEVs can further the goals of environmental protection and best be reflected in the establishment of EPA's standards and regulatory program for MY 2027 and later heavy-duty vehicles. As discussed earlier in this section, EPA will also be considering the important role of ZEV technologies in the upcoming light-duty and medium-duty vehicle proposal for MY 2027 and later, and in the heavy-duty vehicle proposal for MY 2030 and later. EPA requests comment under this proposal on how the Agency can best consider the potential for ZEV technologies to significantly reduce air pollution from the heavy-duty vehicle sector (including but not limited to the topic of whether and how to consider including specific sales requirements for HD ZEVs).

Letter to EPA Administrator Michael Regan from the Moving Forward Network. October 26, 2021.

4. Statutory Authority for This Action

As discussed in Section I, EPA is proposing revisions to emission standards and other requirements applicable to emissions of NO

, PM, HC, CO, and GHG from new heavy-duty engines and vehicles under our broad statutory authority to regulate air pollutants emitted from mobile sources, consistent with our history of using a multi-pollutant approach to regulating criteria pollutants and GHG emissions from heavy-duty engines and vehicles. Section 202(a)(1) of the Clean Air Act (CAA) requires the EPA to “by regulation prescribe (and from time to time revise) . . . standards applicable to the emission of any air pollutant from any class or classes of new motor vehicles or new motor vehicle engines . . . , which in his judgment cause, or contribute to, air pollution which may reasonably be anticipated to endanger public health or welfare”. Standards under CAA section 202(a) take effect “after such period as the Administrator finds necessary to permit the development and application of the requisite technology, giving appropriate consideration to the cost of compliance within such period.” Thus, in establishing or revising CAA section 202(a) standards designed to reduce air pollution that endangers public health and welfare, EPA also must consider issues of technological feasibility, compliance cost, and lead time. EPA may consider other factors such as safety. There are currently heavy-duty engine and vehicle standards for emissions of NO

, PM, HC, CO, and GHGs.

Under CAA section 202(a)(3)(A), standards for emissions of NO

, PM, HC, and CO emissions from heavy-duty vehicles and engines are to “reflect the greatest degree of emission reduction achievable through the application of technology which the Administrator determines will be available for the model year to which such standards apply, giving appropriate consideration to cost, energy, and safety factors associated with the application of such technology.”

Section 202(a)(3)(C) requires that these standards apply for no less than 3 model years and apply no earlier than 4 years after promulgation.

Section 202(a)(3)(A) and (C) apply only to regulations applicable to emissions of these four pollutants and do not apply to regulations applicable to GHGs.

Emission standards set under CAA section 202(a) apply to vehicles and engines “for their useful life.” CAA section 202(d) directs EPA to prescribe regulations under which the useful life of vehicles and engines shall be determined, and for heavy-duty vehicles and engines establishes minimum values of 10 years or 100,000 miles, whichever occurs first, unless EPA determines that greater values are appropriate. CAA section 207(a) further requires manufacturers to provide an emissions warranty, and EPA set the current warranty periods for heavy-duty engines in 1983.

48 FR 52170, November 16, 1983.

As outlined in this executive summary, the proposed program would reduce heavy-duty emissions through several major provisions pursuant to the CAA authority described in this section. Sections I.F and XIV of this preamble further discuss our statutory authority for this proposal; Section I.G further describes the basis of our proposed NO

, PM, HC, CO, and GHG emission standards and other requirements. Section XIII describes how this proposal is also consistent with E.O. 14037, “Strengthening American Leadership in Clean Cars and Trucks” (August 5, 2021), which directs EPA to consider taking action to establish new NO

standards for heavy-duty engines and vehicles beginning with model year 2027.

B. Overview of the Regulatory Action

Our approach to further reduce air pollution from highway heavy-duty engines and vehicles through the proposed program features several key provisions. We co-propose options to address criteria pollutant emissions from heavy-duty engines. In addition, this proposal would make targeted updates to the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 program, proposing that further GHG reductions in the MY 2027 timeframe are appropriate considering lead time, costs, and other factors, including market shifts to zero-emission technologies in certain segments of the heavy-duty vehicle sector. We also propose limited amendments to the regulations that implement our air pollutant emission standards for other sectors (

e.g.,

light-duty vehicles, marine diesel engines, locomotives, various types of nonroad engines, vehicles, and equipment). Our proposed provisions are briefly described in this Section I.B and summarized in Section I.C. We describe the proposed Options 1 and 2 in detail in the Sections III, IV, and XI. We discuss our analyses of estimated emission reductions, air quality improvements, costs, and monetized benefits of the proposed program in Section I.D below, and these are detailed in Sections V through X.

1. Overview of Criteria Pollutant Program

The proposed provisions to reduce criteria pollutant emissions can be thought of in three broad categories: (1) Controlling emissions under a broader range of engine operating conditions, (2) maintaining emission control over a greater portion of an engine's operational life,

and (3) providing manufacturers with flexibilities to meet

the proposed standards while clarifying our regulations. Specifically, provisions in the first category would include updated test procedures and revised emission standards, while those in the second category would include lengthened regulatory useful life and emission warranty periods, as well as several other updates to encourage proper maintenance and repair. These provisions would apply to heavy-duty engines used in Class 2b through 8 vehicles.

Provisions in the third category would provide opportunities to generate NO

emission credits that provide manufacturers with flexibilities to meet the proposed standards and encourage the introduction of new emission control technologies earlier than required. This category also includes our proposal to modernize our current regulatory text, including clarifications and updates for hybrid electric, battery-electric, and fuel cell electric heavy-duty vehicles.

As further discussed in Section IV.A, we use “operational life” to refer to when engines are in use on the road.

EPA plans to consider new standards for chassis-certified Class 2b and 3 vehicles (GVWR between 8,500 and 14,000 pounds) as part of a future combined light-duty and medium-duty rulemaking action, consistent with E.O. 14037. We are not proposing changes to the standards or test procedures for chassis-certified heavy-duty vehicles. Instead, this proposal focuses on engine-certified products.

Our discussion below focuses on the revised emission standards and useful life and warranty periods contained in two regulatory options that we are proposing: The proposed Option 1 and the proposed Option 2. Although we refer to the two regulatory options as the proposed Option 1 and the proposed Option 2, we are giving full consideration to both options, as well as the full range of options between them. Both the proposed Option 1 and the proposed Option 2 would begin in MY 2027, but the proposed Option 1 would have a second step in MY 2031. Overall, proposed Option 2 is less stringent than the MY 2031 standards in the proposed Option l because the proposed Option 2 has higher numeric NO

emission standards and shorter useful life periods. As discussed in Section D of this Executive Summary and Section VI, we project proposed Option 1 would result in greater emission reductions than proposed Option 2; Section I.G summarizes the basis of our proposed Options 1 and 2 with details on our feasibility analysis for each option presented in Section III. In addition to the proposed Options 1 and 2, we present an alternative (the Alternative) that we also considered. The Alternative is more stringent than either the proposed Option 1 MY 2031 standards or the proposed Option 2 because the Alternative has shorter lead time, lower numeric NO

emission standards and longer useful life periods. We note that we currently are unable to conclude that the Alternative is feasible in the MY 2027 timeframe over the useful life periods in the Alternative in light of deterioration in the emission control technologies that we have evaluated to date, and we expect that we would need additional supporting data or other information in order to determine that the Alternative is feasible in the MY 2027 timeframe to consider adopting it in the final rule.

The proposed Option 1 and proposed Option 2 generally represent the range of regulatory options, including the standards and test procedures, regulatory useful life and emission-related warranty periods and implementation schedules that we are currently considering in this rulemaking, depending in part on any additional comments and other information we receive on the feasibility, costs, and other impacts of the proposed Options 1 and 2. We request comment on all aspects of the proposed Options 1 and 2, or other alternatives roughly within the range of options covered by the proposed Options 1 and 2, including the revised emission standards and useful life and warranty periods, one and two-step approaches, model years of implementation and other provisions described in this proposal. Based on currently available information, in order to consider adopting the Alternative in the final rule, we believe we would need additional supporting data or other information to be able to conclude that the Alternative is feasible in the MY 2027 timeframe. We request comment, including relevant data and other information, related to the feasibility of the implementation model year, numeric levels of the emission standards, and useful life and warranty periods included in the Alternative, or other alternatives outside the range of options covered by the proposed Options 1 and 2.

We will continue learning about the capability and durability of engine and aftertreatment technologies through our ongoing technology evaluations, as well as any information provided in public comments on this proposal. Section III describes our plans for expanding on the analyses developed for this proposal.

2. Overview of Targeted Revisions to the HD GHG Phase 2 Program

In addition to the proposed criteria pollutant program provisions, we are proposing to increase the stringency of the existing GHG standards for MY 2027 trucks and requesting comment on updates to the advanced technology incentive program for electric vehicles. We propose updates to select MY 2027 GHG standards after consideration of the market shifts to zero-emission technologies in certain segments of the heavy-duty vehicle sector. These proposed GHG provisions are based on our evaluation of the heavy-duty EV market for the MY 2024 through 2027 timeframe. While the HD Phase 2 GHG standards were developed in 2016 based on the premise that electrification of the heavy-duty market beyond low volume demonstration projects was unlikely to occur in the timeframe of the program, our current evaluation shows that there are a number of manufacturers producing fully electric heavy-duty vehicles in several applications in 2021—and this number is expected to grow in the near term. These developments along with considerations of lead time, costs and other factors have demonstrated that further GHG reductions in the MY 2027 timeframe are appropriate. We expect school buses, transit buses, delivery trucks (such as box trucks or step vans), and short haul tractors to have the highest EV sales of all heavy-duty vehicle types between now and 2030.

We have given careful consideration to an approach that would result in targeted updates to reflect the emerging HD EV market without fundamentally changing the HD GHG Phase 2 program as a whole. Thus, we are proposing targeted updates to the HD Phase 2 GHG standards to account for the current electrification of the market by making changes to only those standards that are impacted by these four types of electric vehicles. We believe this proposal considered the feasibility of technologies, cost, lead time, emissions impact, and other relevant factors, and therefore these standards are appropriate under CAA section 202(a). We also are seeking comment on changes to the advanced technology credit program since the current level of HD GHG Phase 2 incentives for electrification may no longer be appropriate for certain segments of the HD EV market considering the projected rise in electrification. We provide an overview of this approach in this Section I.C and detail our proposal in Section XI.

See Section XI.B for more on the growing EV market for these four vehicle types.

C. Summary of the Major Provisions in the Regulatory Action

1. Controlling Criteria Pollutant Emissions Under a Broader Range of Engine Operating Conditions

In the first broad category of provisions to reduce criteria pollutant emissions in this rulemaking, we are proposing to reduce emissions from heavy-duty engines under a range of operating conditions through revisions to our emissions standards and test procedures. These revisions would apply to both laboratory-based standards and test procedures for both heavy-duty CI and SI engines, as well as the standards and test procedures for heavy-duty CI engines on the road in the real world.

Duty cycle test procedures measure emissions while the engine is operating over precisely defined duty cycles in an emissions testing laboratory and provide very repeatable emission measurements. “Off-cycle” test procedures measure emissions while the engine is not operating on a specified duty-cycle; this testing can be conducted while the engine is being driven on the road (

e.g.,

on a package delivery route), or in an emission testing laboratory. We may also refer to off-cycle test procedures in this preamble as “on the road” testing for simplicity. Both duty cycle and off-cycle testing are conducted pre-production (

e.g.,

for certification) or post-production to verify that the engine meets applicable duty cycle or off-cycle emission standards throughout useful life (See Section III.A and IV.K for more discussion).

i. Proposed Laboratory Standards and Test Procedures

For heavy-duty CI engines, we are proposing new standards for laboratory-based tests using the current duty cycles, the transient Federal Test Procedure (FTP) and the steady-state Supplemental Emission Test (SET) procedure. These existing test procedures require CI engine manufacturers to demonstrate the effectiveness of emission controls when the engine is transitioning from low-to-high loads or operating under sustained high load, but do not provide for demonstrating emission control under sustained low-load operations. We are proposing that laboratory demonstrations for heavy-duty CI engines would also include a new low-load cycle (LLC) test procedure to demonstrate that emission controls are meeting proposed LLC standards when the engine is operating under low-load and idle conditions. The proposed addition of the LLC would help ensure lower NO

emissions in urban areas and other locations where heavy-duty vehicles operate in stop-and-go traffic or other low-load conditions.

For heavy-duty SI engines, we are proposing new standards for their laboratory demonstrations using the current FTP duty cycle, and updates to the current engine mapping procedure to ensure the engines achieve the highest torque level possible during testing. We are proposing to add the SET procedure to the heavy-duty SI laboratory demonstrations; it is currently only required for heavy-duty CI engines. Heavy-duty SI engines are increasingly used in larger heavy-duty vehicles, which makes it more likely for these engines to be used in higher-load operations covered by the SET. We are further proposing a new refueling emission standard for incomplete vehicles above 14,000 lb GVWR starting in MY 2027.

The proposed refueling standard is based on the current refueling standard that applies to complete heavy-duty gasoline-fueled vehicles. Consistent with the current evaporative emission standards that apply for these same vehicles, we are proposing that manufacturers could use an engineering analysis to demonstrate that they meet our proposed refueling standard.

Some vehicle manufactures sell their engines or “incomplete vehicles” (

i.e.,

chassis that include their engines, the frame, and a transmission) to body builders who design and assemble the final vehicle.

Our proposed Option 1 and proposed Option 2 NO

emission standards for all defined duty cycles for heavy-duty CI and SI engines are detailed in Table 1. As shown, the proposed Option 1 NO

standards would be implemented in two steps beginning with MY 2027 and becoming more stringent in MY 2031. The proposed Option 2 NO

emission standards would be implemented with a single step in MY 2027. As noted in Section B.1 of this Executive Summary, overall, we consider proposed Option 2 to be less stringent than the standards in the proposed Option 1 because proposed Option 2 has higher numeric NO

emission standards with similar useful life periods as the proposed Option 1 in MY 2027, and shorter length of useful life periods than the proposed Option 1 in MY 2031. In contrast, the Alternative is more stringent than proposed Option 1's MY 2031 standards (see Section III), and we currently do not have information to support the conclusion that the combination of shorter lead time, lower numeric levels of the standards and longer useful life periods in the Alternative is feasible in the MY 2027 timeframe based on the emission control technologies we have evaluated to date. See Section III for more discussion on feasibility. Consistent with our current approach for criteria pollutants, the standards in proposed Options 1 and 2, presented in Table 1, are numerically identical for SI and CI engines.

See Section III for our proposed and alternative PM, HC, and CO standards.

Table 1—Proposed Options 1 and 2 NO

Emission Standards for Heavy-Duty CI and SI Engines on Specific Duty Cycles

[Milligrams/horsepower-hour (mg/hp-hr)]

Duty cycle

Proposed Option 1

Model years 2027-2030

All HD engines

Model years 2031 and later

Spark ignition HDE, light HDE, and

medium HDE

Heavy HDE through

intermediate useful life (IUL)

Heavy HDE from IUL to full useful life (FUL)

Proposed

Option 2

Model years 2027 and later

Spark ignition HDE, light HDE, medium HDE, heavy HDE

FTP (transient mid/high load conditions)

SET (steady-state conditions)

LLC (low-load conditions)

100

The current FTP and SET standard for all HD engines is 0.20 g/hp-hr or 200 mg/hp-hr; we are proposing the LLC test procedure and therefore there is not a current standard for the LLC.

ii. Proposed On-the-Road Standards and Test Procedures

In addition to demonstrating emission control over defined duty cycles in a laboratory, heavy-duty CI engines must be able to demonstrate emission control over an undefined duty cycle while engines are in use on the road in the real world. Both proposed Options 1 and 2 include updates to the procedure for “off-cycle” testing, such that data collected during a wider range of operating conditions would be valid, and therefore subject to emission standards.

As discussed in Section III, “off-cycle” testing measures emissions while the engine is not operating on a specified duty-cycle; this testing can be conducted while the engine is being driven on the road (

e.g.,

on a package delivery route), or in an emission testing laboratory.

Similar to the current approach, emission measurements collected during off-cycle testing would be collected on a second-by-second basis. We are proposing the emissions data would be grouped into 300-second windows of operation. Each 300-second window would then be binned based on the type of operation that the engine performs during that 300-second period. Specifically, the average power of the engine during each 300-second window would determine whether the emissions during that window are binned as idle (Bin 1), low-load (Bin 2), or medium-to-high load (Bin 3).

Due to the challenges of measuring engine power directly on in-use vehicles, we are proposing to use the CO

emission rate (grams per second) as a surrogate for engine power; further, we propose to normalize CO

emission rates relative to the nominal maximum CO

rate of the engine (

e.g.,

when an engine with a maximum CO

emission rate of 50 g/sec emits at a rate of 10 g/sec, its normalized CO

emission rate is 20 percent).

Our proposed 3-bin approach would cover a wide range of operations that occur in the real world—significantly more in-use operation than today's requirements. Bin 1 would include extended idle and other very low-load operations, where engine exhaust temperatures may drop below the optimal temperature where SCR-based aftertreatment works best. Bin 2 would include a large fraction of urban driving conditions, during which engine exhaust temperatures are generally moderate. Bin 3 would include higher-power operations, such as on-highway driving that typically results in higher exhaust temperatures and high catalyst efficiencies.

Given the different operational profiles of each of these three bins, we are proposing a separate standard for each bin. The proposed structure follows that of our current not-to-exceed (NTE) off-cycle standards, while covering a much broader range of engine operation.

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

Table 2 presents our proposed Option 1 and Option 2 off-cycle standards for NO

emissions from heavy-duty CI engines. The proposed Option 2 off-cycle NO

standards are higher (less stringent) and have a shorter useful life than the proposed Option 1 standards in MY 2031. For the Alternative, our assessment of currently available data indicates that the off-cycle standard for the medium/high load bin (Bin 3) would not be feasible in the MY 2027 timeframe, and additional or different technology would be necessary to meet the Alternative off-cycle standards. See Section III for details on the off-cycle standards for other pollutants in the proposed Options 1 and 2 and the Alternative.

Table 2—Proposed Options 1 and 2 Off-Cycle NO

Standards for Heavy-Duty CI Engines

Operation bin

Proposed Option 1

Model years 2027-2030

All HD engines

Model years 2031 and later

Light HDE, and medium HDE

Heavy HDE through IUL

Heavy HDE from IUL to FUL

Proposed

Option 2

Model years 2027 and later

All HD engines

idle (g/hr)

7.5

low load (mg/hp-hr)

180

7.5

150

medium/high load (mg/hp-hr)

In addition to the proposed standards for the defined duty cycle and off-cycle test procedures, the proposed Options 1 and 2 include several other provisions for controlling emissions from specific operations in CI or SI engines. First, we are proposing to allow CI engine manufacturers to voluntarily certify to the California Air Resources Board (CARB) clean idle standards by adding to EPA regulations an idle test procedure that is based on an existing CARB procedure.

We are also proposing to require a closed crankcase ventilation system for all highway CI engines to prevent crankcase emissions from being emitted directly to the atmosphere. See Section III.B for more discussion on both the proposed idle and crankcase provisions. For heavy-duty SI, we are proposing refueling emission standards for incomplete vehicles above 14,000 lb GVWR (see Section III.E for more discussion).

13 CCR 1956.8 (a)(6)(C)—Optional NO

idling emission standard.

2. Maintaining Criteria Pollutant Emission Control Over a Greater Portion of an Engine's Operational Life

Reducing emissions under a broad range of engine operating conditions is one category of our proposed program provisions. Maintaining emission control over a greater portion of an engine's operational life is the second broad category of proposed provisions. The major elements in this category include proposals to (1) extend the regulatory useful life of heavy-duty engines, (2) provide an opportunity for manufacturers to use rapidly aged parts necessary to demonstrate emission performance over the regulatory useful life, (3) lengthen emission warranty periods, and 4) increase the likelihood that emission controls will be maintained properly through more of the service life of heavy-duty engines. Our proposals for each of these elements is outlined below and detailed in Section IV; unless explicitly stated otherwise, proposals for each of these elements would apply under both proposed Options 1 and 2, as well as the full range of options in between them.

i. Proposed Useful Life Periods

EPA is proposing to increase the regulatory useful life mileage values for new heavy-duty engines to better reflect real-world usage, extend the emissions durability requirement for heavy-duty engines, and ensure certified emission performance is maintained throughout

more of an engine's operational life. For proposed Option 1, Increases to useful life values for heavy-duty engines would apply in two steps, as discussed in Section IV.A. For the first step for CI engines, MY 2027 through 2030, we are proposing useful life mileage values that are approximately a midpoint between the current useful life mileages and our proposed CI engines MY 2031 and later mileages. For the second step, we are proposing useful life mileage values for MY 2031 and later CI engines that cover a majority of the estimated operational life mileages, but less than the first out-of-frame rebuild for these engines. The proposed Option 1 first step for SI engines in MY 2027 through 2030 would better align with the current useful life mileages for GHG emission standards applicable to these engines. The proposed Option 1 second step useful life mileage for SI engines for MY 2031 and later is based on the published engine service life for heavy-duty gasoline engines in the market today.

The useful life mileages in the proposed Option 2 are shorter than those in the proposed Option 1; we are giving full consideration to the useful life periods of proposed Options 1 and 2, and the range between the useful life periods in the proposed Options. Our proposed Option 1 and Option 2 useful life periods for heavy-duty CI and SI engines are presented in Table 3. See Section IV for the useful periods of the Alternative.

As noted in this Section C of the Executive Summary, we are proposing refueling standards for HD SI engines that are certified as incomplete vehicles that are equivalent to the standards in effect for complete heavy-duty vehicles. We propose to apply the existing useful life periods for the complete vehicle refueling standards (15 years or 150,000 miles; see 40 CFR 1037.103(f) and 86.1805-16(d) for “MDPV” and “HDV”) to the HD SI engines certified as incomplete vehicles. See preamble Section IV.A for more details.

Table 3—Proposed Options 1 and 2 Useful Life Periods for Heavy-Duty CI and SI Engines Criteria Pollutant Standards

Model year

Spark-ignition HDE

Miles

Years

Compression-ignition

Light HDE

Miles

Years

Medium HDE

Miles

Years

Heavy HDE

b c

Miles

Years

Current

110,000

185,000

435,000

Proposed Option 1: 2027-2030

155,000

190,000

270,000

600,000

Proposed Option 1

: 2031 and later

200,000

270,000

350,000

800,000

Proposed Option 2: 2027 and later

150,000

250,000

325,000

650,000

Current useful life period for Spark-ignition HDE and Light HDE for GHG emission standards is 15 years or 150,000 miles. See 40 CFR 1036.108(d).

We are also proposing to increase the hours-based useful life criterion from the current 22,000 hours for Heavy HDE to 32,000 hours for model years 2027-2030 and 40,000 hours for model years 2031 and later.

The Heavy HDE class includes certain SI engines (e.g., natural gas-fueled engines) intended for use in Class 8 vehicles.

For MY 2031 and later Heavy HDE, the proposed Option 1 would include intermediate useful life periods of 435,000 miles, 10 years, or 22,000 hours, whichever comes first. See Section III for a discussion of the proposed Option 1 standards we propose to apply for the intermediate and full useful life periods.

ii. Proposed Durability Demonstration Updates

The proposed longer useful life periods outlined in Table 3 would require manufacturers to extend their durability demonstrations, which show that the engines will meet applicable emission standards throughout their regulatory useful life. EPA regulations require manufacturers to include durability demonstration data as part of an application for certification of an engine family. Manufacturers typically complete this demonstration by following regulatory procedures to calculate a deterioration factor (DF).

To address the need for accurate and efficient emission durability demonstration methods, EPA worked with manufacturers and CARB to address this concern through guidance for MY 2020 and later engines.

In Section IV.F, we propose three methods for determining DFs, consistent with the recent guidance, including a new option to bench-age the aftertreatment system to limit the burden of generating a DF over the proposed lengthened useful life periods. We also propose to codify in the EPA regulations three DF verification options available to manufacturers in recent guidance. The proposed verification options would confirm the accuracy of the DF values submitted by manufacturers for certification. We also introduce a test program to evaluate a rapid-aging protocol for diesel catalysts that we may consider as an option for CI engine manufacturers to use in their durability demonstration.

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

iii. Proposed Emissions Warranty Periods

EPA's current emission-related warranty periods range from 22 percent to 54 percent of regulatory useful life. As EPA is proposing to lengthen the useful life periods in this rulemaking, we are also proposing to lengthen the emission warranty periods and increase the fraction of useful life miles covered under warranty. These proposed revised warranty periods are expected to result in better engine maintenance and less tampering, helping to maintain the benefits of the emission controls. In addition, longer regulatory warranty periods may lead engine manufacturers to simplify repair processes and make them more aware of system defects that would be tracked and reported to EPA over a longer period.

In Section IV.B, we provide detailed discussion and request comment on these four ways that longer emission warranty periods may enhance long-term performance of emission-related devices and systems. We also discuss other impacts of lengthening regulatory emission warranty periods and other approaches that vary coverage and may similarly ensure long-term in-use emission performance.

EPA is proposing to lengthen the emissions warranty periods for all primary intended service classes to cover a larger portion of the operational lives of new heavy-duty engines. Our proposed Option 1 warranty mileages for MY 2031 are approximately 80 percent of the proposed useful life mileages. The proposed Option 1 MY 2027 through 2030 mileages are

approximately midpoints between the current and proposed Option 1 MY 2031 and later mileages. The proposed Option 2 set of emission warranty periods would match CARB's Step 1 warranty periods that will already be in effect beginning in model year 2022 for engines sold in California.

We believe the proposed Option 2 mileages represent an appropriate lower end of the range we are considering for the revised regulatory emission warranty periods. Our proposed Option 1 and proposed Option 2 emission warranty periods are presented in Table 4.

See Section IV.B for updates in proposed Options 1 and 2 to our years-based warranty periods and add hours-based warranty periods for all engine classes to cover low average annual mileage applications. We also considered an alternative set of warranty periods that are presented in Section IV.B.

For SI engines, the Alternative 1 warranty mileage matches the current useful life, consistent with the approach for Light HDE Alternative 1 warranty.

In addition to exhaust standards, we are proposing refueling standards for HD SI engines that are certified as incomplete vehicles. The onboard refueling vapor recovery systems necessary to meet the proposed refueling standards will likely build on existing evaporative emissions systems, and we propose to apply the existing warranty periods for evaporative emission control systems to the ORVR systems (5 years or 50,000 miles). See Preamble IV.B.1.

Table 4—Proposed Options 1 and 2 Emission-Related Warranty Periods for Heavy-Duty CI and SI Engines Criteria Pollutant Standards

Model year

Spark-ignition HDE

Miles

Hours

Compression-ignition

Light HDE

Miles

Hours

Medium HDE

Miles

Hours

Heavy HDE

Miles

Hours

Years

Current

50,000

100,000

Proposed Option 1: 2027-2030

110,000

6,000

150,000

7,000

220,000

11,000

450,000

22,000

Proposed Option 1: 2031 and later

160,000

8,000

210,000

10,000

280,000

14,000

600,000

30,000

Proposed Option 2: 2027 and later

110,000

150,000

350,000

iv. Proposed Provisions To Ensure Long-Term Emissions Performance

In the ANPR, we introduced several ideas for an enhanced, comprehensive strategy to increase the likelihood that emission controls will be maintained properly through more of the operational life of heavy-duty engines, including beyond their useful life periods. Our proposed updates to maintenance provisions include defining the type of maintenance manufacturers may choose to recommend to owners in maintenance instructions, updating minimum maintenance intervals for certain critical emission-related components, and outlining specific requirements for maintenance instructions provided in the owner's manual.

We are proposing changes to the owner's manual and emissions label requirements to ensure access to certain maintenance information and improve serviceability. We expect this additional maintenance information to improve factors that contribute to mal-maintenance, which would result in better service experiences for independent repair technicians, specialized repair technicians, owners who repair their own equipment, and possibly vehicle inspection and maintenance technicians. We also believe that improving owner experiences with operating and maintaining heavy-duty engines can reduce the likelihood of tampering.

v. Proposed Inducement Provisions

ANPR commenters indicated that engine derates or “inducements” are a significant source of operator frustration.

EPA currently has guidance on potential options manufacturers might utilize to meet existing requirements through an inducement strategy for their SCR-based aftertreatment system.

We are proposing to codify inducement provisions after considering manufacturer designs and operator experiences with SCR-based aftertreatment systems. In Section IV.D, we present the key principles we followed in developing the proposed inducement provisions, which includes a focus on conditions that are within an operator's control, a multi-step derate schedule, and a backup check to override false inducements. We also include a detailed set of requests for comment highlighting the wide range of adjustments we are currently considering.

Engine derating is an aftertreatment design strategy that reduces engine performance to induce operators to maintain appropriate levels of high-quality diesel emission fluid (DEF) in their SCR-based aftertreatment systems. Throughout this preamble we refer to engine derates that derive from DEF-related triggers as “inducements.”

Kopin, Amy. Memorandum to docket EPA-HQ-OAR-2019-0055. “Inducement-Related Guidance Documents, and Workshop Presentation.” October 1, 2021.

vi. Proposed Onboard Diagnostics Provisions

Onboard diagnostics (OBD) refer to systems of electronic controllers and sensors required by current regulation to detect malfunctions of engines and emission controls. EPA's existing OBD program, promulgated in 2009, allows manufacturers to demonstrate how the OBD system they have designed to comply with California OBD requirements also complies with the intent of the EPA OBD requirements.

Although EPA maintains separate OBD regulations, all manufacturers currently seek OBD approval from CARB for OBD systems in engine families applying for 50-state certification, and then use this approval to demonstrate compliance with EPA requirements.

See 40 CFR 86.010-18(a)(5).

In Section IV.C, we are proposing to update our OBD regulations both to better address newer diagnostic methods and available technologies, and to streamline provisions where possible. We propose to incorporate by reference the existing CARB OBD regulations updated in 2019 as the starting point for our updated OBD regulations.

We are proposing to exclude or revise certain CARB provisions that we believe are not appropriate for a federal program and are proposing to include additional elements to improve the usefulness of

OBD systems for users (see Section IV.C for details).

CARB Final Rulemaking to Consider Technical Status and Prosed Revisions to On-Board Diagnostic System Requirements for Heavy-Engines, Passenger Cars, Light-Duty Trucks, Medium Duty Vehicles and Engines was approved and became effective on July 31, 2013. California Code of Regulations sections 1968.2 and 1971.1 available at:

https://ww3.arb.ca.gov/regact/2012/hdobd12/hdobd12.htm

EPA is specifically proposing additional OBD elements to improve the robustness and usefulness of OBD systems. These additional elements include emission system health monitors, an expanded list of publicly available OBD parameters, additional freeze frame data parameters, and enabling certain self-testing capabilities for owners. These proposed changes would benefit the environment by helping to reduce malfunctioning emission systems in-use through access to additional data that may be useful for service technicians, state and local inspection and maintenance operations, and owners.

3. Other Proposed Compliance Provisions and Flexibilities

In addition to the key program provisions, we are also proposing several provisions to provide manufacturers with flexibility to meet the proposed standards and encourage the introduction of new emission control technologies earlier than required; these provisions would apply under both proposed Options 1 and 2, as well as the full range of options in between them. These provisions include our proposal to migrate and update the compliance provisions of 40 CFR part 86, subpart A, to 40 CFR part 1036; continue averaging, banking, and trading (ABT) of credits generated against our heavy-duty engine criteria pollutant standards; provide incentives for early adoption of technologies to meet the standards; allow manufacturers to generate NO

emission credits for hybrid electric, battery electric, and fuel cell electric vehicles (HEVs, BEVs, and FCEVs); and make limited amendments to regulations that implement our air pollutant emission standards for other industry sectors, including light-duty vehicles, light-duty trucks, marine diesel engines, locomotives, and various types of nonroad engines, vehicles, and equipment.

i. Proposed Migration From 40 CFR Part 86, Subpart A

Heavy-duty criteria pollutant regulations were originally codified into 40 CFR part 86, subpart A, in the 1980s. We believe this rulemaking provides an opportunity to clarify (and otherwise improve) the wording of our existing heavy-duty criteria pollutant regulations in plain language and migrate them to 40 CFR part 1036.

Part 1036, which was created for the Phase 1 GHG program, provides a consistent, updated format for our regulations, with improved organization. In general, this migration is not intended to change the compliance program previously specified in part 86, except as specifically proposed in this rulemaking. See our summary of the proposed migration in Section III.A, and additional details in our memorandum to the docket.

The proposed provisions of part 1036 would generally apply for model years 2027 and later, unless noted, and manufacturers would continue to use part 86 in the interim.

We are proposing to migrate some provisions to parts 1065 and 1068 to apply broadly to other sectors. Additionally, some current vehicle provisions in part 1037 refer to part 86 and we are proposing to update those references in part 1037 as needed.

Stout, Alan; Brakora, Jessica. Memorandum to docket EPA-HQ-OAR-2019-0055. “Technical Issues Related to Migrating Heavy-Duty Highway Engine Certification Requirements from 40 CFR part 86, subpart A, to 40 CFR part 1036”. October 1, 2021.

ii. Proposed Opportunities for NO

Emission Credits

We are proposing targeted revisions to the current emissions ABT provisions to account for specific aspects of the broader proposed program. We are also proposing an early adoption incentive program that would recognize the environmental benefits of lower-emitting vehicles entering the fleet ahead of required compliance dates for the proposed standards. Through this optional program, manufacturers who demonstrate early compliance with the proposed MY 2027 or MY 2031 standards would apply a multiplier to emission credits generated under the proposed ABT program (see Section IV.H for details). We are also proposing to offer NO

emission credits for HEVs, BEVs and FCEVs based on the near-zero or zero-tailpipe emissions performance of these technologies, for HEVs or BEVs and FCEVs, respectively, and after consideration of ANPR comments. We are choosing not to propose emission credit multipliers for HEVs, BEVs, and FCEVs. We believe that the potential loss of emission reductions that could result from providing credit multipliers is not justified in light of the current extent of technology development and implementation. Manufacturers choosing to generate NO

emission credits from BEVs or FCEVs would need to conduct testing and meet durability requirements discussed in Section IV.

iii. Other Amendments

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

We are proposing amendments in two areas of note for the general compliance provisions in 40 CFR part 1068. First, we are proposing to take a comprehensive approach for making confidentiality determinations related to compliance information that companies submit to EPA. We are proposing to apply these provisions for all highway, nonroad, and stationary engine, vehicle, and equipment programs, as well as aircraft and portable fuel containers.

Second, we are proposing provisions that include clarifying text to establish what qualifies as an adjustable parameter and to identify the practically adjustable range for those adjustable parameters. The proposed adjustable-parameter amendments also include specific provisions related to electronic controls that aim to deter tampering.

4. Targeted Revisions to the HD GHG Phase 2 Program

As noted at the start of this Section I.B, we have developed a proposed approach to make targeted updates that take into consideration the growing HD electric vehicle market without fundamentally changing the HD GHG Phase 2 program as a whole. These developments along with considerations of lead time, costs and other factors have demonstrated that further GHG reductions in the MY 2027 timeframe are appropriate. Specifically, we propose to adjust the HD GHG Phase 2 vehicle GHG emission standards by sales-weighting the projected heavy-duty EV production levels of school buses, transit buses, commercial delivery trucks, and short-haul tractors and by lowering the applicable emission standards in MY 2027 accordingly. We project these four vehicle types will have the highest EV sales of all heavy-

duty vehicle types between now and 2030. Because these four EV vehicle types do not correspond directly with the specific subcategories for standards that we developed in HD GHG Phase 2 (subcategories differentiated by vehicle weight, use, fuel type, etc.), we use EPA certification data to determine which subcategories of standards would be impacted by EV production in MY 2027. By sales-weighing the projected production levels of the four EV vehicle types in 2027, our proposed approach adjusts 17 of the 33 MY 2027 Phase 2 vocational vehicle and tractor standards and does not change any MY 2021 or MY 2024 standards or any of the Class 2b/3 pickup truck and van standards. We request comment on the proposed approach to determine the threshold.

In addition to these proposed standard adjustments, we are requesting comment on options to update the advanced technology incentive program for electric and plug-in hybrid vehicles beginning in MY 2024. These changes may be appropriate to reflect that such levels of incentives for electrification may no longer be appropriate for certain segments of the HD EV market. We are trying to balance providing additional incentives for the continued development of zero and near-zero emission vehicles without inadvertently undermining the GHG emission reductions from the HD GHG Phase 2 program with inappropriate incentives.

D. Projected Emission Reductions, Air Quality Improvements, Costs, and Benefits

Our analysis of the estimated emission reductions, air quality improvements, costs, and monetized benefits of the proposed criteria pollutant program is outlined below and detailed in Sections V through X. While the discussion below generally focuses on our analysis of the proposed Option 1, we also discuss the proposed Option 2; additional information on analyses of proposed Options 1 and 2 is included in the sections that follow. As discussed in Section III, we currently lack information to show that the Alternative is feasible in the MY 2027 timeframe based on the emission control technologies that we have evaluated to date, and therefore we are not presenting an analysis of the costs or benefits of the Alternative. We expect that we would need additional data supporting the feasibility of the Alternative to further consider it in the development of the final rule.

The proposed provisions in Options 1 and 2, which are described in detail in Sections III and IV, are expected to reduce emissions from highway heavy-duty engines in several ways. We project the proposed emission standards for heavy-duty CI engines would reduce tailpipe emissions of NO

; the combination of the proposed low-load test cycle and off-cycle test procedure for CI engines would help to ensure that the reductions in tailpipe emissions are achieved in-use, not only under high-speed, on-highway conditions, but also under low-load and idle conditions. We also project reduced tailpipe emissions of NO

, CO, PM, VOCs, associated air toxics, and methane from the proposed emission standards for heavy-duty SI engines, particularly under cold-start and high-load operating conditions. The longer emission warranty and regulatory useful life requirements for heavy-duty CI and SI engines in the proposed Options 1 and 2 would help maintain the expected emission reductions for all pollutants, including primary exhaust PM

2.5

, throughout the useful life of the engine. The onboard refueling vapor recovery requirements for heavy-duty SI engines in the proposed Options 1 and 2 would reduce VOCs and associated air toxics. Table 5 summarizes the projected reductions in heavy-duty emission from the proposed Options 1 and 2 in 2045 and shows the significant reductions in NO

emissions from the proposal. In general, we estimate that Option 2 would result in lower emission reductions because of the less stringent emission standards combined with shorter useful life and warranty periods than the proposed Option 1 in MY 2031. Section VI and draft Regulatory Impact Analysis (RIA) Chapter 5 provide more information on our projected emission reductions for proposed Options 1 and 2, as well as the Alternative.

Table 5—Projected Heavy—Duty Emission Reductions in 2045 From the Proposed Options 1 and 2 Standards

Pollutant

Percent reduction in highway heavy-duty emissions

Proposed Option 1

Proposed Option 2

Primary PM

2.5

VOC

The proposed criteria pollutant program in proposed Options 1 and 2 would also reduce emissions of other pollutants. For instance, the proposed Option 1 would result in a 27 percent reduction in benzene and a 0.7 percent reduction in methane from highway heavy-duty engines in 2045. Leading up to 2045, emission reductions are expected to increase over time as the fleet turns over to new, compliant engines.

Reductions in emissions of NO

, VOC, PM

2.5

, and CO from the proposed rule are projected to lead to decreases in ambient concentrations of ozone, PM

2.5

, NO

, and CO. The proposed Option 1 standards would significantly decrease ozone concentrations across the country, with a population-weighted average decrease of over 2 ppb in 2045.

Ambient PM

2.5

, NO

and CO concentrations are also predicted to improve in 2045 as a result of the proposed Option 1 program. The emission reductions provided by the proposed standards would be important in helping areas attain the NAAQS and prevent future nonattainment. In addition, the proposed Option 1 standards are expected to result in improvements in nitrogen deposition and visibility, but they are predicted to have relatively little impact on ambient concentrations of air toxics.

Due to resource constraints, we only conducted air quality modeling for the proposed Option 1.

We also used our air quality data from modeling Option 1 to conduct a demographic analysis of human exposure to future air quality in scenarios with and without the proposed criteria pollutant standards in place. To compare demographic trends, we sorted 2045 baseline air quality concentrations from highest to lowest concentration and created two groups: Areas within the contiguous U.S. with the worst air quality and the rest of the country. We found that in the 2045 baseline, the number of people of color living within areas with the worst air quality is nearly double that of non-Hispanic Whites. We also found that the largest predicted improvements in both ozone and PM

2.5

are estimated to occur in areas with the worst baseline air quality, where larger numbers of people of color are projected to reside. More details on our air quality modeling and demographic analyses are included in Section VII and draft RIA Chapter 6.

Our estimates of reductions in heavy-duty engine emissions, and associated air quality impacts, are based on manufacturers adding emissions-reduction technologies in response to the proposed Options 1 or 2 criteria pollutant standards, along with making emission control components more durable in response to the longer regulatory useful life periods in the proposed Options 1 or 2. We also estimate costs to both truck owners and manufacturers attributable to the longer emission warranty for both the proposed Options 1 and 2. We estimate costs of

the proposed Options 1 and 2 to both manufacturers and truck owners in our program cost analysis in Section V and draft RIA Chapter 7.

Our evaluation of costs to manufacturers includes direct costs (

i.e.,

cost of materials, labor costs) and indirect manufacturing costs (

e.g.,

warranty, research and development). The direct manufacturing costs include individual technology costs for emission-related engine components and for exhaust aftertreatment systems. Importantly, our analysis of direct manufacturing costs includes the costs of the existing emission control technologies because we expect the emissions warranty and regulatory useful life provisions in the proposed Options 1 and 2 to have some impact on not only the new technology added to comply with the proposed standards, but also on any existing emission control components. The cost estimates thus reflect the portion of baseline case engine hardware and aftertreatment systems for which new costs would be incurred due to the proposed warranty and useful life provisions, even absent any changes in the level of emission standards. The indirect manufacturing costs in our analysis include warranty costs, research and development costs, profits and other indirect costs. We combine direct and indirect manufacturing costs to calculate total technology costs, which we then add to operating costs in our calculation of program costs.

As part of our evaluation of operating costs, we estimate costs truck owners incur to repair emission control system components. Our repair cost estimates are based on industry data showing the amount spent annually by truck owners on different types of repairs, and our estimate of the percentage of those repairs that are related to emission control components. Our analysis of this data shows that extending the useful life and emission warranty periods would lower emission repair costs during several years of operation for several vehicle types. More discussion on our emission repair costs estimates of the proposed Options 1 and 2 criteria pollutant standards is included in Section V, with additional details presented in draft RIA Chapter 7.

We combined our estimates of emission repair costs with other operating costs (

i.e.,

urea/DEF, fuel consumption) and technology costs to calculate total program costs. Our analysis of proposed Option 1 shows that total costs for the criteria pollutant program relative to the baseline (or no action scenario) range from $1.8 billion in 2027 to $2.3 billion in 2045 (2017 dollars, undiscounted, see Table V-16). We estimate that proposed Option 2 would result in higher costs than the proposed Option 1 in 2045. We expect that the same emission control technologies would be needed to meet both the proposed Option 1 and 2 standards, which would result in the same direct technology costs in both cases. The higher projected costs of the proposed Option 2 relative to the proposed Option 1 result from our expectation that the shorter useful life and emission warranty periods of the proposed Option 2 compared to proposed Option 1 in MY 2031 and later would lead to higher emission control system repair costs for proposed Option 2 than the proposed Option 1 (

i.e.,

shorter emissions warranty periods result in higher emission repair costs in proposed Option 2) (see Section V for details). Overall, the analysis shows that the costs of proposed Option 1 are less than the costs of proposed Option 2. The present value of program costs for proposed Options 1 and 2, and additional details are presented in Section V.

Section VIII presents our analysis of the human health benefits associated with the proposed Options 1 and 2. We estimate that in 2045, the proposed Option 1 would result in total annual monetized ozone- and PM

2.5

-related benefits of $12 and $33 billion at a 3 percent discount rate, and $10 and $30 billion at a 7 percent discount rate.

In the same calendar year, proposed Option 2 would result in total annual monetized ozone- and PM

2.5

-related benefits of $9 and $26 billion at a 3 percent discount rate, and $8 and $23 billion at a 7 percent discount. These benefits only reflect those associated with reductions in NO

emissions (a precursor to both ozone and secondarily-formed PM

2.5

) and directly-emitted PM

2.5

from highway heavy-duty engines. There are additional human health and environmental benefits associated with reductions in exposure to ambient concentrations of PM

2.5

, ozone, and NO2 that EPA has not quantified due to data, resource, or methodological limitations. There would also be benefits associated with reductions in air toxic pollutant emissions that result from the proposed program, but we did not attempt to monetize those impacts due to methodological limitations. The estimated benefits of the proposed Options 1 and 2 would be larger if we were able to monetize all unquantified benefits at this time. More detailed information about the benefits analysis conducted for the proposal, including the present value of program benefits for Options 1 and 2, is included in Section VIII and draft RIA Chapter 8.

2045 is a snapshot year chosen to approximate the annual health benefits that occur in a year in which the proposed program would be fully implemented and when most of the regulated fleet would have turned over.

We compare total monetized health benefits to total costs associated with the proposed Options 1 and 2 in Section IX. Table 6 shows that annual benefits of the proposed Option 1 would be larger than the annual costs in 2045, with annual net benefits of $9 and $31 billion assuming a 3 percent discount rate, and net benefits of $8 and $28 billion assuming a 7 percent discount rate.

Annual benefits would also be larger than annual costs in 2045 for the proposed Option 2, although net benefits would be slightly lower than from the proposed Option 1 (net benefits of proposed Option 2 would be $6 and $23 billion at a 3 percent discount rate, and net benefits of $5 and 21 billion at a 7 percent discount rate). For both the proposed Options 1 and 2, benefits also outweigh the costs when expressed in present value terms and as equalized annual values.

The range of benefits and net benefits reflects a combination of assumed PM

2.5

and ozone mortality risk estimates and selected discount rate.

Table 6—2045 Costs, Benefits and Net Benefits of the Proposed Option 1 and Option 2

[Billions, 2017$]

a b

Proposed Option 1

3% discount

7% discount

Proposed Option 2

3% discount

7% discount

2045:

Benefits

$12-$33

$10-$30

$9.1-$26

$8.2-$23

Costs

2.3

2.9

Net Benefits

9.2-31

8.1-28

6.2-23

5.3-21

All benefits estimates are rounded to two significant figures; numbers may not sum due to independent rounding. The range of benefits (and net benefits) in this table are two separate estimates and do not represent lower- and upper-bound estimates, though they do reflect a grouping of estimates that yield more and less conservative benefits totals. The costs and benefits in 2045 are presented in annual terms and are not discounted. However, all benefits in the table reflect a 3 percent and 7 percent discount rate used to account for cessation lag in the valuation of avoided premature deaths associated with long-term exposure.

The benefits associated with the standards presented here do not include the full complement of health, environmental, and climate-related benefits that, if quantified and monetized, would increase the total monetized benefits.

Section X examines the potential impacts of the proposed standards on heavy-duty vehicles (sales, mode shift, fleet turnover) and employment in the heavy-duty industry. The proposed standards may impact vehicle sales due to both changes in purchase price and longer emission warranty mileage requirements; these effects may show up as increased purchases of more new vehicles than usual before the proposed standards come into effect, in anticipation of higher prices after the proposed standards (“pre-buy”). The proposed standards may also reduce sales after the proposed standards would be in place (“low-buy”). In this proposal, we suggest an approach to quantify potential impacts on vehicle sales due to new emission standards; we also provide an example of how the results could be applied to the final regulatory analysis for this rule in draft RIA Chapter 10.1. Our example results for proposed Option 1 suggest pre- and low-buy for Class 8 trucks may range from zero to approximately two percent increase in sales over a period of up to 8 months before the 2031 standards begin (pre-buy), and a decrease in sales from zero to approximately two percent over a period of up to 12 months after the 2031 standards begin (low-buy). We have provided the example results as information for commenters to consider and provide input to EPA on this type of approach for quantifying how emissions regulations may impact heavy-duty vehicle sales fleet turnover. Based on input we receive, we may consider using this type of analysis in the final rule to inform both the potential impacts on vehicle sales, and the related impacts on employment in the heavy-duty industry. We expect little mode shift due to the proposed standards because of the large difference in cost of moving goods via trucks versus other modes of transport (

e.g.,

planes or barges).

Employment impacts of the proposed standards depend on the effects of the standards on sales, the share of labor in the costs of the standards, and changes in labor intensity due to the standards. We quantify the effects of costs on employment, and we discuss the effects due to sales and labor intensity qualitatively. This partial quantification of employment impacts estimates that increased costs of vehicles and parts would, by itself and holding labor intensity constant, be expected to increase employment by 400 to 2,200 job-years in 2027, and 300 to 1,800 job-years in 2032 under proposed Option 1.

Employment would be expected to increase by 400 to 2,200 job years, and 300 to 1,500 job years in 2027 and 2032 respectively under proposed Option 2. See Section X for further detail on limitations and assumptions of this analysis.

Where a job-year is, for example, one year of full-time work for one person, or one year of half-time work for two people.

Finally, the projected cost and GHG emission impacts of the proposed changes to the HD GHG Phase 2 program are described in Section XI.E.

E. Summary of Specific Requests for Comments

We are requesting comment on all aspects of this proposed rulemaking. In addition, as detailed in the sections that follow, we are specifically requesting comments from stakeholders on a variety of key topics throughout this proposed to inform the final rulemaking process. In this section we highlight topics on which we believe it would be especially beneficial to receive comments from stakeholders, or which may be of most interest to stakeholders.

Section III presents extensive information and analyses, including two options for the proposed criteria pollutant standards, to provide notice that EPA will be considering a range of numeric emission standard values and implementation dates in the final rule. We are requesting comment on the proposed Options 1 and 2, as well as the Alternative, standards for each duty cycle, as well as the one- and two-step approaches in proposed Options 1 and 2, respectively, and the implementation dates of MYs 2027 and 2031. In addition, we are requesting input on several aspects of the proposed new LLC duty cycle for heavy-duty CI engines and applying the SET duty cycle to heavy-duty SI engines (see Section III). We are also requesting comment on several aspects of the proposed off-cycle standards for heavy-duty CI engines, including the levels of the standards in proposed Options 1 and 2 and the specific operating range covered by each bin, and whether off-cycle standards and in-use testing should also apply for SI engines. For SI engines, we request comment on our proposed refueling HC emission standard for incomplete vehicles above 14,000 lb GVWR, including requests for comment and data to inform test procedure updates we should consider to measure HC emissions from these larger fuel systems and vehicles. We are also requesting comment on whether EPA should finalize interim standards for testing used to verify that the engine meets the standards through useful life (

i.e.,

in-use testing that occurs after the vehicle enters commerce). Typically, EPA sets the same standards for in-use testing and certification testing but, in some cases, we have provided higher in-use standards to give manufacturers time to gain experience with the new technology needed to meet the standards.

As outlined in this Executive Summary and discussed in Sections III and IV, we are proposing to significantly lower NO

emission standards and to significantly increase the regulatory useful life for heavy-duty on highway engines, which would require manufactures to develop and produce additional engine and aftertreatment technology. Due to the combination of lower (more stringent) numeric standards and longer useful periods included in our proposal, we are requesting comment on whether

EPA should finalize in-use standards that are 40 to 100 percent higher than the proposed Option 1 standards for MY 2027 to MY 2033 engines.

See 81 FR 23414 (April 28, 2014).

In Section IV we detail our requests for comment on a number of topics related to our proposed lengthened useful life and warranty periods, as well as other compliance provisions and flexibilities. For instance, we are requesting stakeholder input on our proposed useful life and warranty periods, as well as the range of options covered by the proposed Options 1 and 2, or other alternatives outside of that range. In addition to the proposed warranty periods, we request comment on other approaches to warranty, such as graduated warranty phases, that may similarly ensure long-term in-use emission performance with a smaller impact on the purchase price. We further request comment on our proposed provisions to increase the likelihood that emission controls will be maintained properly through more of the service life of heavy-duty engines (

e.g.,

revise inducement strategies, improve serviceability). In addition, we are interested in stakeholder input on our proposed approaches for the durability demonstration that manufacturers are required to include their application for certification (see Section IV.F for details). We are also interested in stakeholder input on our proposed requirements for manufacturers choosing to generate NO

emission credits from BEVs or FCEVs, as well as whether EPA should consider for this final rule, or other future rules, restrictions for NO

emission credits in the longer term (

e.g.,

beyond MY 2031) (See Section IV.I for details).

Throughout Sections III and IV, we discuss areas where our proposal differs from the California Air Resources Board (CARB) Heavy-Duty Omnibus Rulemaking, and request comment on our proposal, including whether it is appropriate to harmonize the federal and CARB regulatory programs more in light of the authority and requirements of CAA section 202, and the benefits or challenges if EPA were to finalize particular aspects of its program that are or are not fully aligned with the Omnibus.

There are also several topics that we are requesting comment on that relate to the analyses that support our proposal. For instance, we are interested in stakeholder input on our approach for estimating emission reductions from lengthening useful life and warranty periods (see Section VI for details). We are also interested in comments on our estimate of repair costs for emission control system components (see Section V for details). We request comment on the method we outline to estimate potential impacts of a proposed regulation on heavy-duty vehicle sales; we also request comment on approaches to estimate employment impacts attributable to the proposed rule (see Section X for details).

We are also interested in input from environmental justice stakeholders and underserved and overburdened communities, including children's health stakeholders, regarding the need for revised standards and how heavy-duty vehicles affect communities (see Section II); the air quality improvements we project from this proposal and how they are distributed (see Section VII); and ways the proposal could be improved to advance environmental protection for all people, including people of color, low-income communities, and those who live near highways or in heavily trafficked areas with frequent truck congestion and idling, such as ports.

In Section XI, we request comment in a number of areas related to the proposed updates to the HD GHG Phase 2 program for certain heavy-duty vehicles that are shifting to zero-emission vehicles. We are considering whether it would be appropriate in the final rule to increase the stringency of the standards even more than what we propose. Therefore, we request information on heavy-duty electric vehicle sales projections, including for what HD vehicle types, to help inform our HD electric vehicle sales projections in the MY 2024 through MY 2029 timeframe. We also are considering whether to establish more stringent standards beyond MY 2027, specifically in MY 2028 and MY 2029 using the methodology described in Section XI.C.1. We request comment on appropriate stringency and supporting data for each of those model years.

We are also interested in stakeholder input that supports changes to the advanced technology credit multiplier approach under consideration. In addition, we request comment under this proposal on how EPA can best consider the potential for ZEV technology to significantly reduce air pollution from the heavy-duty vehicle sector, including whether and how to consider including specific sales requirements for HD ZEVs.

For these and all requests for comment detailed throughout the proposal, stakeholders are encouraged to provide their rationale and any available data that supports to their perspectives.

I. Introduction

A. Brief Overview of the Heavy-Duty Truck Industry

Heavy-duty highway vehicles (also referred to as “trucks” in this preamble) range from commercial pickup trucks to vocational vehicles that support local and regional transportation, construction, refuse collection, and delivery work, to line-haul tractor-trailers that move freight cross-country. This diverse array of vehicles is categorized into weight classes based on gross vehicle weight ratings (GVWR). These weight classes span Class 2b pickup trucks and vans from 8,500 to 10,000 lbs GVWR through Class 8 line-haul tractors and other commercial vehicles that exceed 33,000 lbs GVWR.

53 54

This proposed rulemaking includes revised criteria pollutants standards for engine-certified Class 2b through 8 heavy-duty engines and vehicles; this proposal also includes revised GHG standards for Class 4 through 8 vehicles. Class 2b and 3 vehicles with GVWR between 8,500 and 14,000 pounds are primarily commercial pickup trucks and vans and are sometimes referred to as “medium-duty vehicles”. The majority of Class 2b and 3 vehicles are chassis-certified vehicles and will be included in a future combined light-duty and medium-duty rulemaking action, consistent with E.O. 14037, Section 2a. Heavy-duty engines and vehicles are also used in nonroad applications, such as construction equipment; nonroad heavy-duty engines and vehicles are not the focus of this proposal. See Section I for more discussion on the spectrum of heavy-duty vehicles and how they relate to the proposed rule. See Sections I.B and III for more discussion on the spectrum of heavy-duty vehicles and how they relate to the proposed rule.

The focus of this proposal is on highway heavy-duty engines and vehicles. However, we are also proposing limited amendments to regulations that implement our air pollutant emission standards for other sectors, including light-duty vehicles, light-duty trucks, marine diesel engines, locomotives, and various types of nonroad engines, vehicles, and equipment (see Section XII).

Heavy-duty highway vehicles are primarily powered by diesel-fueled, compression-ignition (CI) engines. However, gasoline-fueled, spark-ignition (SI) engines are common in the lighter weight classes, and smaller numbers of alternative fuel engines (

e.g.,

to the needs of a Class 5 mixed freight delivery vehicle or a Class 6 beverage truck. Any performance differences needed to operate across this range of vehicles can be achieved through adjustments to chassis-based systems (

i.e.,

transmission, cooling system) external to the engine.

The industry that designs and manufactures these heavy-duty vehicles is composed of three primary segments: Vehicle manufacturers, engine manufacturers and other major component manufacturers, and secondary manufacturers (

i.e.,

body builders). Some vehicle manufacturers are vertically integrated, designing, developing, and testing their engines in-house for use in their vehicles, while others purchase some or all of their engines from independent engine suppliers. Today, only one major independent engine manufacturer supports the heavy-duty truck industry, though some vehicle manufactures sell their engines or “incomplete vehicles” (

i.e.,

chassis that include their engines, the frame, and a transmission) to body builders who design and assemble the final vehicle. Each of these subindustries is often supported by common suppliers for subsystems such as transmissions, axles, engine controls, and emission controls.

In addition to the manufacturers and suppliers responsible for producing highway heavy-duty vehicles, an extended network of dealerships, repair and service facilities, and rebuilding facilities contribute to the sale, maintenance, and extended life of these vehicles and engines. Heavy-duty vehicle dealerships offer customers a place to order vehicles from a specific manufacturer and include service facilities for those vehicles and engines. Dealership service technicians are trained to perform regular maintenance and make repairs, which generally include repairs under warranty and in response to manufacturer recalls. Some trucking fleets, businesses, and large municipalities benefit from hiring their own technicians to service their vehicles in their own facilities. Many refueling centers along major trucking routes have also expanded their facilities to include roadside assistance and service stations to diagnose and repair common problems.

Heavy-duty CI engines installed in the larger weight classes of vehicles are designed to be rebuilt. Dealerships and other service facilities are generally equipped to replace common components, such as pistons and bearings that wear over time. However, large-scale (

i.e.,

“out-of-frame”) engine overhauls that replace most of the engine components require a more sophisticated process that only a limited number of facilities provide. Some heavy-duty engine manufacturers have established their own rebuilding facilities as a separate branch of their operations and others work with independent rebuilding factories that are affiliated with multiple engine manufacturers. Rebuilding allows owners to extend the life of their engines at a lower cost than purchasing a replacement vehicle, which has made the practice common for some heavy-duty engines.

The end-users for highway heavy-duty vehicles are as diverse as the applications for which these vehicles are purchased. Smaller weight class heavy-duty vehicles are commonly purchased by delivery services, contractors, and municipalities. The middle weight class vehicles tend to be commercial vehicles for businesses and municipal work that transport people and goods locally and regionally or provide services such as utilities. Vehicles in the heaviest weight classes are generally purchased by businesses with high load demands, such as construction, towing or refuse collection, or freight delivery fleets and owner-operators with both load and speed demands for regional and long-haul goods movement. The competitive nature of the businesses and owner-operators that purchase and operate highway heavy-duty vehicles means that any time the vehicle is unable to operate due to maintenance or repair (

i.e.,

downtime) can lead to a loss in income. This need for reliability drives much of the truck and engine manufacturers' innovation and research to meet the needs of their customers.

B. History of Emission Standards for Heavy-Duty Engines and Vehicles

Emission standards for heavy-duty highway engines in the U.S. were first issued by the Department of Health, Education, and Welfare in the 1960s. These standards and the corresponding certification and testing procedures were codified at 45 CFR part 1201. In 1972, shortly after EPA was created as a federal agency and given responsibility for regulating heavy-duty engines, EPA published new standards and updated procedures while migrating the regulations to 40 CFR part 85 as part of the effort to consolidate all EPA regulations in a single location.

EPA created 40 CFR part 86 in 1976 to reorganize emission standards and certification requirements for light-duty vehicles and heavy-duty highway engines. In 1985, EPA promulgated new standards for heavy-duty highway engines, codifying the standards in 40 CFR part 86, subpart A. Since then, EPA has promulgated several rules for highway heavy-duty engines and vehicles to set new and more stringent emission standards for criteria pollutants and precursors,

to set requirements for controlling evaporative and refueling emissions,

to establish emission control programs for greenhouse gases (GHGs), and to add or revise certification procedures.

See Section I.G for additional discussion on EPA's Statutory Authority relevant to this proposal.

For example, oxides of nitrogen (NO

), hydrocarbons (HC), particulate matter (PM) and carbon monoxide (CO).

See Section III.E for more discussion on controlling evaporative and refueling emissions from light- and heavy-duty vehicles.

U.S. Environmental Protection Agency. “EPA Emission Standards for Heavy-Duty Highway Engines and Vehicles,” Available online:

https://www.epa.gov/emission-standards-reference-guide/epa-emission-standards-heavy-duty-highway-engines-and-vehicles

. (last accessed June 25, 2021).

EPA's criteria pollutant regulatory programs for the heavy-duty highway industry apply to engines.

Our regulations require that engine manufacturers identify the “primary intended service class” for each engine by considering the vehicles for which they design and market their engines. Heavy-duty CI engines are specified as light heavy-duty engine (Light HDE), medium heavy-duty engine (Medium HDE), or heavy heavy-duty engine (Heavy HDE) based largely on the weight class of the vehicles in which the engines are expected to be installed and the potential for rebuild. SI heavy-duty engines are generally specified as a single spark-ignition HDE service class unless they are designed or intended for use in the largest heavy-duty vehicles, and therefore considered heavy HDEs.

EPA sets emission standards and other regulatory provisions, including regulatory useful life and emissions warranty periods, that are targeted for the operational characteristics of each primary intended service class.

EPA's regulations address heavy-duty engines and vehicles separately from light-duty vehicles. Vehicles with GVWR above 8,500 pounds (Class 2b and above) are classified in the regulations as heavy-duty. For criteria pollutants EPA's standards generally apply to the engine rather than the vehicle for heavy-duty. However, most of the Class 2b and 3 pickup trucks and vans (vehicles with a GVWR between 8,500 and 14,000 pounds) are chassis-certified heavy-duty vehicles and covered by standards in EPA's Tier 3 program (79 FR 23414, April 28, 2014; 80 FR 0978, February 19, 2015). As noted in Section III, there are a small number of Class 2b and 3 engines (

e.g.,

trucks with dual rear wheels that are sold with a cab and chassis only), which are the subject of this proposed rulemaking.

See 40 CFR 1036.140(a)(3).

In the 1990s, EPA issued increasingly stringent standards for NO

, CO, HC,

and PM. These exhaust standards were derived from engine-based emission control strategies and manufacturers generally certified their engines' emission performance over defined duty cycles on an engine dynamometer (

i.e.,

“engine certification”). In 1997, EPA finalized standards for heavy-duty highway diesels (62 FR 54693, October 21, 1997), effective beginning with the 2004 model year, including a combined non-methane hydrocarbon (NMHC) and NO

standard that represented a reduction of NO

emissions by 50 percent. These NO

reductions also resulted in significant reductions in secondary nitrate PM.

In early 2001, EPA finalized the 2007 Heavy-Duty Engine and Vehicle Rule (66 FR 5002, January 18, 2001) to continue addressing NO

and PM emissions from both diesel and gasoline-fueled highway heavy-duty engines. This rule established a comprehensive national program that regulated a heavy-duty engine and its fuel as a single system, with emission standards taking effect beginning with model year (MY) 2007 and fully phasing in by MY 2010 (EPA 2010 standards). Prior to 2007, emission standards were based on controlling the emissions formed during the combustion process (

i.e.,

engine-out emissions), and there was no further control of emissions between the engine and the truck's tailpipe. But with promulgation of the 2007 final rule, emission standards were, for the first time, based on the use of technologies to capture, convert, and reduce harmful engine-out emissions, resulting in tailpipe emissions that were cleaner than engine-out emissions. By and large, the industry met these new standards through the use of exhaust aftertreatment technologies, namely, diesel oxidation catalysts, particulate filters, and high-efficiency catalytic exhaust emission control devices. Consistent with previous criteria pollutant regulatory programs, the program also offered flexibility to manufacturers through the use of various emission credits averaging, banking, and trading (ABT) programs.

To ensure proper functioning of these aftertreatment technologies, which could be damaged by sulfur, EPA also reduced the allowable level of sulfur in highway diesel fuel by 97 percent by mid-2006. Together, the use of exhaust aftertreatment technologies and lower-sulfur fuel resulted in diesel-fueled trucks that emitted PM and NO

tailpipe emissions at levels 90 percent and 95 percent below emission levels from then-current highway heavy-duty engines, respectively. The PM standard for new highway heavy-duty engines was set at 0.01 grams (10 milligrams, or 10 mg) per horsepower-hour (mg/hp-hr) by MY 2007 and the NO

and NMHC standards of 200 mg/hp-hr and 140 mg/hp-hr, respectively, were set to phase in between model years 2007 and 2010.

In finalizing that rule, EPA estimated that the emission reductions would achieve significant health and environmental impacts, and that the total monetized PM

2.5

and ozone-related benefits of the program would exceed $70 billion, versus program costs of $4 billion (1999$).

Heavy-duty engine emission standards are defined in work specific units (

i.e.,

milligrams per horsepower-hour) because the standards cover a large range of engine ratings, and thus time specific standards would not provide equal stringency across all engines.

In 2005, EPA finalized a manufacturer-run, in-use testing program that uses portable emission measurement systems to measure HC, CO, NO

, and PM emissions from the exhaust of in-use heavy-duty diesel trucks (70 FR 34594, June 14, 2005). The fully enforceable program began in 2007. This effort was a significant advancement in helping to ensure that the benefits of more stringent emission standards are realized under real-world driving conditions.

In 2009, as advanced emissions control systems were being introduced to meet the MY 2007/2010 standards, EPA promulgated a final rule to require that these advanced emissions control systems be monitored for malfunctions via an onboard diagnostic (OBD) system (74 FR 8310, February 24, 2009). The rule, which has been fully phased in, required engine manufacturers to install OBD systems that monitor the functioning of emission control components on new engines and alert the vehicle operator to any detected need for emission-related repair. It also required that manufacturers make available to the service and repair industry information necessary to perform repair and maintenance service on OBD systems and other emission related engine components. In addition, EPA published a series of documents that provided guidance to manufacturers on potential methods and measures to ensure that trucks equipped with Selective Catalytic Reduction (SCR) technology would be refilled with the specified quantity and quality of a urea-water mixture (also known as diesel exhaust fluid, or DEF) necessary for the proper functioning of this NO

-reducing technology. These guidance documents describe potential approaches that included progressive levels of alerts and warnings communicated to the driver of the truck, which would allow adequate time to refill the DEF tank, but ultimately, if DEF is not added, or if it is determined to be of insufficient quality, a vehicle speed-limiting “inducement” would be triggered, requiring the DEF tank to be refilled or the system to be repaired.

Also in 2009, EPA and Department of Transportation's National Highway Traffic Safety Administration (NHTSA) began working on a joint regulatory program to reduce GHG emissions and fuel consumption from heavy-duty vehicles and engines.

By utilizing regulatory approaches recommended by the National Academy of Sciences, the first phase (“Phase 1”) of the GHG and fuel efficiency program was finalized in 2011 (76 FR 57106, September 15, 2011).

The Phase 1 program, spanning implementation from MY 2014 to 2018, included separate standards for highway heavy-duty vehicles and heavy-duty engines. The program offered flexibility allowing manufacturers to attain these standards through a mix of technologies and the option to participate in an emissions credit ABT program. In the Phase 1 rulemaking EPA also revised the heavy-duty vehicle and engine regulations to make them consistent with the light-duty vehicle approach, such that all criteria pollutant and GHG standards would apply regardless of fuel type, including all-electric vehicles (EVs).

Greenhouse gas emissions from heavy-duty engines are primarily carbon dioxide (CO2), but also include methane (CH

) and nitrous oxide (N

O). Because CO

is formed from the combustion of fuel, it is directly related to fuel consumption.

National Research Council; Transportation Research Board. The National Academies' 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.” 2010. Available online:

https://www.nap.edu/catalog/12845/technologies-and-approaches-to-reducing-the-fuel-consumption-of-medium-and-heavy-duty-vehicles

In 2016, EPA and NHTSA finalized the Heavy-Duty Phase 2 GHG and fuel efficiency program (“HD GHG Phase 2”) (81 FR 73478, October 25, 2016). HD GHG Phase 2 includes technology-advancing performance-based standards for highway heavy-duty vehicles and heavy-duty engines that will phase in over the long term, with initial standards for most vehicles and engines commencing in MY 2021, increasing in stringency in MY 2024, and culminating in MY 2027 standards. HD GHG Phase 2 built upon the Phase 1 program and set standards based not only on currently available technologies, but also on technologies that were still under development or not yet widely deployed. To ensure adequate time for

technology development, HD GHG Phase 2 provided up to 10 years lead time to allow for the development and phase-in of these control technologies. EPA recently finalized technical amendments to the HD GHG Phase 2 rulemaking (“HD Technical Amendments”) that included changes to the test procedures for heavy-duty engines and vehicles to improve accuracy and reduce testing burden.

86 FR 34308, June 29, 2021.

C. Petitions to EPA for Additional NO

Emissions Control

In the summer of 2016 more than 20 organizations, including state and local air agencies from across the country, petitioned EPA to develop more stringent NO

emission standards for on-road heavy-duty engines.

Among the reasons stated by the petitioners for such an EPA rulemaking was the need for NO

emission reductions to reduce adverse health and welfare impacts and to help areas attain the NAAQS. EPA subsequently met with a wide range of stakeholders in listening sessions, during which certain themes were consistent across those stakeholders.

For example, it became clear that there is broad support for federal action in collaboration with the California Air Resources Board (CARB). So-called “50-state” standards would enable technology suppliers and manufacturers to efficiently produce a single set of reliable and compliant products. There was also broad acknowledgement of the value of aligning implementation of new NO

standards with existing MY 2021, 2024, and 2027 milestones for HD Phase 2 GHG and fuel efficiency standards. Stakeholders thought that such alignment would ensure that the GHG and fuel consumption reductions achieved under HD GHG Phase 2 are maintained and allow the regulated industry to implement GHG- and NO

-reducing technologies into their products at the same time.

Brakora, Jessica. “Petitions to EPA for Revised NO

Standards for Heavy-Duty Engines” Memorandum to Docket EPA-HQ-OAR-2019-0055. December 4, 2019.

Stakeholders included: Emissions control technology suppliers; engine and vehicle manufacturers; a labor union that represents heavy-duty engine, parts, and vehicle manufacturing workers; a heavy-duty trucking fleet trade association; an owner-operator driver association; a truck dealers trade association; environmental, non-governmental organizations; states and regional air quality districts; Tribal interests; California Air Resources Board (CARB); and the petitioners.

U.S. EPA. 2016. Memorandum in Response to Petition for Rulemaking to Adopt Ultra-Low NO

Standards for On-Highway Heavy-Duty Trucks and Engines. Available at

https://19january2017snapshot.epa.gov/sites/production/files/2016-12/documents/nox-memorandum-nox-petition-response-2016-12-20.pdf

EPA responded to the petitions on December 20, 2016, noting that an opportunity exists to develop a new, harmonized national NO

reduction strategy for heavy-duty highway engines.

EPA emphasized the importance of scientific and technological information when determining the appropriate level and form of a future low NO

standard and highlighted the following potential components of the action:

U.S. EPA. 2016. Memorandum in Response to Petition for Rulemaking to Adopt Ultra-Low NO

Standards for On-Highway Heavy-Duty Trucks and Engines. Available at

https://19january2017snapshot.epa.gov/sites/production/files/2016-12/documents/nox-memorandum-nox-petition-response-2016-12-20.pdf

• Lower NO

emission standards

• Improvements to test procedures and test cycles to ensure emission reductions occur in the real world, not only over the currently applicable certification test cycles

• Updated certification and in-use testing protocols

• Longer periods of mandatory emission-related component warranties

• Consideration of longer regulatory useful life, reflecting actual in-use activity

• Consideration of rebuilding

• Incentives to encourage the transition to current- and next-generation cleaner technologies as soon as possible

As outlined in the Executive Summary and detailed in the sections that follow, this proposed rulemaking considered these components.

D. California Heavy-Duty Highway Low NO

Program Development

In this section, we present a summary of recent efforts by the state of California to establish new, lower emission standards for highway heavy-duty engines and vehicles.

For the past several decades, EPA and the California Air Resources Board (CARB) have worked together to reduce air pollutants from highway heavy-duty engines and vehicles by establishing harmonized emission standards for new engines and vehicles. For much of this time, EPA has taken the lead in establishing emission standards through notice and comment rulemaking, after which CARB would adopt the same standards and test procedures. For example, EPA promulgated the current heavy-duty engine NO

and PM standards in a 2001 final rule, and CARB subsequently adopted the same emission standards. EPA and CARB often cooperate during the implementation of highway heavy-duty standards. Thus, for many years, the regulated industry has been able to design a single product line of engines and vehicles that can be certified to both EPA and CARB emission standards (which have been the same) and sold in all 50 states.

California has long had the unique ability among states to adopt its own separate new motor vehicle and engine standards per Section 209 of the Clean Air Act. Although CAA section 209(a) expressly preempts states from adopting and enforcing standards relating to the control of emissions from new motor vehicles or new motor vehicle engines (such as state controls for new heavy-duty engines and vehicles), CAA section 209(b) directs EPA to waive this preemption for California under certain conditions. Even with California's ability under the CAA to establish its own emission standards, EPA and the California Air Resources Board have worked closely together over the past several decades to largely harmonize new heavy-duty vehicle and engine criteria pollutant standard programs.

Given the significant ozone and PM air quality challenges in the state of California, CARB has taken several steps since the EPA 2010 standards were implemented to encourage or establish standards and requirements that go beyond EPA requirements, to further reduce NO

emissions from heavy-duty vehicles and engines in its state. CARB's optional (voluntary) low NO

program, which started in 2013, was created to encourage heavy-duty engine manufacturers to introduce technologies that emit NO

at levels below the current EPA 2010 standards. Under this optional program, manufacturers can certify engines to one of three levels of stringency that are 50, 75, and 90 percent below the existing EPA 2010 standards with the lowest optional standard being 20 milligrams NO

per horsepower-hour (mg/hp-h).

To date, only natural gas and liquefied petroleum gas engines have been certified to these optional standards.

California Code of Regulations, Title 13, section 1956.8.

California Air Resources Board. “Optional Low NO

Certified Heavy-Duty Engines”. February 2020. Available online:

https://ww3.arb.ca.gov/msprog/onroad/optionnox/optional_low_nox_certified_hd_engines.pdf

In May 2016, CARB published its Mobile Source Strategy that outlined its approach to reduce in-state emissions from mobile sources and meet its air quality targets.

In November 2016, CARB held its first Public Workshop on its plans to update its heavy-duty engine and vehicle programs.

CARB's 2016 Workshop kicked off a technology

demonstration program (the CARB “Low NO

Demonstration Program”), and announced plans to update emission standards, laboratory-based and in-use test procedures, emissions warranty, durability demonstration requirements, and regulatory useful life provisions. The initiatives introduced in its 2016 Workshop have since become components of CARB's Heavy-Duty “Omnibus” Rulemaking.

California Air Resources Board. “Mobile Source Strategy”. May 2016. Available online:

https://ww3.arb.ca.gov/planning/sip/2016sip/2016mobsrc.pdf

California Air Resources Board. “Heavy-Duty Low NO

: Meetings & Workshops”. Available online:

https://ww2.arb.ca.gov/our-work/programs/heavy-duty-low-nox/heavy-duty-low-nox-meetings-workshops

California Air Resources Board. Heavy-Duty Engine and Vehicle Omnibus Regulation and Associated Amendments. Available online:

https://ww2.arb.ca.gov/rulemaking/2020/hdomnibuslownox

CARB's goal for its Low NO

Demonstration Program was to investigate the feasibility of reducing NO

emissions to levels significantly below today's EPA 2010 standards. Southwest Research Institute (SwRI) was contracted to perform the work, which was split into three “Stages.”

In Stage 1 and 1b, SwRI demonstrated an engine technology package capable of achieving a 90 percent NO

emissions reduction on today's regulatory test cycles to a useful life of 435,000 miles using an accelerated aging process.

In Stage 2, SwRI developed and evaluated a new low load-focused engine test cycle. In Stage 3, SwRI evaluated a new engine platform and different technology package to ensure both criteria and GHG emission performance. EPA has been closely observing CARB's Low NO

Demonstration Program as a member of the Low NO

Advisory Group for the technology development work, which includes representatives from heavy-duty engine and aftertreatment industries, as well as from federal, state, and local governmental agencies.

Southwest Research Institute. “Update on Heavy-Duty Low NO

Demonstration Programs at SwRI”. September 26, 2019. Available online:

https://ww3.arb.ca.gov/msprog/hdlownox/files/workgroup_20190926/guest/swri_hd_low_nox_demo_programs.pdf

Southwest Research Institute. “Evaluating Technologies and Methods to Lower Nitrogen Oxide Emissions from Heavy-Duty Vehicles: Final Report”. April 2017. Available online:

https://ww3.arb.ca.gov/research/apr/past/13-312.pdf

California Air Resources Board. “Evaluating Technologies and Methods to Lower Nitrogen Oxide Emissions from Heavy-Duty Vehicles”. May 10, 2017. Available online:

https://ww3.arb.ca.gov/research/veh-emissions/low-nox/low-nox.htm

CARB has published several updates related to its Omnibus Rulemaking. In June 2018, CARB approved its “Step 1” update to California's emission control system warranty regulations.

Starting in MY 2022, the existing 100,000-mile warranty for all diesel engines will increase to 110,000 miles for engines certified as light heavy-duty, 150,000 miles for medium heavy-duty engines, and 350,000 miles for heavy heavy-duty engines. In November 2018, CARB approved revisions to the OBD requirements that include implementation of real emissions assessment logging (REAL) for heavy-duty engines and other vehicles.

In April 2019, CARB published a “Staff White Paper” to present its staff's assessment of the technologies they believed were feasible for medium and heavy heavy-duty diesel engines in the 2022-2026 timeframe.

California Air Resources Board. “HD Warranty 2018” June 28, 2018. Available online:

https://ww2.arb.ca.gov/rulemaking/2018/hd-warranty-2018

California Air Resources Board. “Heavy-Duty OBD Regulations and Rulemaking”. Available online:

https://ww2.arb.ca.gov/resources/documents/heavy-duty-obd-regulations-and-rulemaking

California Air Resources Board. “California Air Resources Board Staff Current Assessment of the Technical Feasibility of Lower NO

Standards and Associated Test Procedures for 2022 and Subsequent Model Year Medium-Duty and Heavy-Duty Diesel Engines”. April 18, 2019. Available online:

https://ww3.arb.ca.gov/msprog/hdlownox/white_paper_04182019a.pdf

In August 2020, the CARB governing board approved the staff proposal for the Omnibus rule and directed staff to initiate the process of finalizing the provisions.

81 82

The final Omnibus rule was approved by the California Office of Administrative Law in December 2021. The final rule includes updates to CARB engine standards, duty-cycle test procedures, and heavy-duty off-cycle testing program that would take effect in MY 2024, with additional updates to warranty, durability, and useful life requirements and further reductions in standards in MYs 2027 and 2031.

California Air Resources Board. “Staff Report: Initial Statement of Reasons-Public Hearing to Consider the Proposed Heavy-Duty Engine and Vehicle Omnibus Regulation and Associated Amendments”. June 23, 2020. Available online at:

https://ww3.arb.ca.gov/regact/2020/hdomnibuslownox/isor.pdf

California Air Resources Board. Heavy-Duty Engine and Vehicle Omnibus Regulation and Associated Amendments. Available online:

https://ww2.arb.ca.gov/rulemaking/2020/hdomnibuslownox

Throughout this proposal we use “Omnibus” to refer to the engine standards, duty-cycle test procedures, heavy-duty off-cycle testing program, useful life and warranty requirements included in the final Omnibus.

As described in Sections I.F and I.G, with details in Sections III and IV, EPA is proposing new NO

, PM, HC, and CO emission standards for heavy-duty engines that reflect the greatest degree of emission reduction achievable through the application of technology that we have determined would be available for the model years to which the proposed standards would apply. In doing so we have given appropriate consideration to additional factors, namely lead time, cost, energy, and safety (see Sections I.F and I.G for more discussion). Throughout the rulemaking process we will continue to evaluate what standards are appropriate given the factors that we are directed to consider under CAA section 202(a)(3). As noted at the start of this Section I.D, EPA and CARB have historically worked together to establish harmonized emission standards for new heavy-duty engines and vehicles. We have received comments from different stakeholder groups who have expressed perspectives on the alignment between the EPA and CARB Omnibus standards they would like EPA to consider during the rulemaking. For instance, in response to an Advance Notice of Proposed Rulemaking (ANPR) for this rule, many stakeholders encouraged EPA to develop a national program harmonized to the greatest extent possible (see Section I.E).

Following the ANPR, various stakeholders have provided EPA with additional perspectives on the Omnibus rule and on the extent to which EPA should align with the California program. For example, organizations such as the National Association of Clean Air Agencies,

the National Tribal Air Association,

as well as multiple vehicle supplier trade associations

have written letters to EPA in support of strong federal standards that reflect both the stringency and timeline of CARB's standards. In contrast, some engine manufacturers have raised concerns about EPA harmonizing its national program with California's rule because of their concerns with that program's overall stringency, costs, and focus on near-term NO

reductions over long-term CO

emission reductions. EPA has considered these harmonization comments in light of the authority and requirements of CAA sections 202 and

207 in developing the proposed standards, regulatory useful life periods, and emissions warranty periods and intends to continue to take into consideration potential harmonization with the CARB Omnibus program, as appropriate and consistent with CAA sections 202 and 207, during the rulemaking. As described in Sections III and IV, a notable difference between the proposed EPA program and the Omnibus rule is that the first step of the Omnibus rule takes effect in MY 2024, whereas the first step of the proposed EPA program is in MY 2027. EPA's statutory authority requires a four-year lead time for any heavy-duty engine or vehicle standard promulgated or revised under CAA section 202(a)(3) (see Section I.F). In Sections III and IV, we discuss areas where our proposal aligns with or differs from the Omnibus rule and request comment on issues related to harmonization between the federal and CARB regulatory programs, including benefits or challenges if EPA were to finalize particular aspects of its program that are not fully aligned with the Omnibus rule.

The Agency published an ANPR on January 21, 2020 to present EPA's early thinking on this rulemaking and solicit feedback from stakeholders to inform this proposal (85 FR 3306).

Letter to EPA Administrator Michael Regan from the National Association of Clean Air Agencies. Re: The urgent need for federal regulatory action to adopt more stringent NO

standards for heavy-duty engines and vehicles, beginning immediately with highway heavy-duty trucks. August 26, 2021.

Letter to EPA Administrator Andrew Wheeler from the National Tribal Air Association. Re: EPA's Advance Notice of Proposed Rulemaking for Control of Air Pollution from New Motor Vehicles: Heavy-Duty Engine Standards Docket ID EPA-HQ-OAR-2019-0055. February 20, 2020.

Letter to EPA Administrator Michael Regan from the Motor & Equipment Manufacturers Association, Manufacturers of Emission Controls Association, Advanced Engine Systems Institute, and Alliance for Vehicle Efficiency. Re: Completion of EPA's Heavy-duty Low-NO

Rulemaking. June 24, 2021.

Draft RIA Chapter 5, Appendix 6 includes tables that present the main elements (

i.e.,

numeric level of standards, useful life, emission warranty) of CARB Omnibus requirements and EPA proposal.

As discussed in the draft RIA, we analyzed the emission inventory and air quality impacts for the proposed criteria pollutant standards before the Omnibus Rule was finalized. We may incorporate the Omnibus rule into our emission inventory and other analyses as appropriate for the final rulemaking (FRM).

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We also may incorporate the CARB Advanced Clean Truck (ACT) Regulation into our final rule analyses. As further discussed in Sections IV, VI, and XI, the CARB ACT Regulation requires a minimum percentage of each manufacturer's heavy-duty vehicle sales in the state of California to be zero tailpipe emission technologies starting in MY 2024.

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See Section VI and draft RIA Chapter 5 for more information on our emission inventory modeling for the proposal and plans to incorporate other updates in our modeling for the final rule.

EPA has received waiver requests under CAA section 209(b) from California for the Omnibus or ACT rules; EPA is currently reviewing the waiver requests for the CA Omnibus and ACT rules and may consider including these rules in our analyses for the final rule. See Section III.B for discussion on our proposed approach to a voluntary standard based on one aspect of the Omnibus requirements.

CARB. “Notice of Decision: Advanced Clean Truck Regulation.” June 2020. Available online at:

https://ww3.arb.ca.gov/regact/2019/act2019/nod.pdf

Buysse and Sharpe. (July 20, 2020) “California's Advanced Clean Trucks regulation: Sales requirements for zero-emission heavy-duty trucks”, available online at:

https://theicct.org/publications/california-hdv-ev-update-jul2020

(last accessed August 11, 2021).

E. Advance Notice of Proposed Rulemaking

The ANPR provided background for the provisions proposed in this rulemaking to address criteria pollutant emissions from heavy-duty engines, including technologies we are evaluating, test programs we have initiated, and compliance programs under consideration, as well as requests for comments and data. The ANPR did not include discussion on the potential stringency of standards, potential costs of the standards, or a quantitative assessment of societal impacts (

e.g.,

air quality, economic, environmental health); these topics are presented in this proposal.

The ANPR also did not include the proposed, targeted revisions to the HD GHG Phase 2 program that are included in this rulemaking (see Section I.G for a summary of these proposed provisions and Section XI for details).

EPA received over 300 comments on the ANPR from a wide range of stakeholders, including: Government organizations (state, local, and Tribal), environmental groups, trade associations, heavy-duty engine manufacturers, independent owner-operators, suppliers, individual fleets, and individual private citizens. We provide a brief overview of the perspectives included in these comments in this subsection, with more specific discussion of comments included in subsequent sections of the proposal as relevant to individual com

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