Heavy-Duty Vehicles, Air Pollution, and Climate Change
link to page 2 
Updated February 14, 2023
Heavy-Duty Vehicles, Air Pollution, and Climate Change
In August 2021, the Biden Administration announced plans
prevent vehicle drivers from tampering with emission
to reduce greenhouse gas (GHG) emissions and other air
control devices. EPA estimated that by 2045, the rule would
pollutants from medium- and heavy-duty vehicles and
result in, inter alia, up to 2,900 fewer premature deaths;
engines through a series of rulemakings over three years
18,000 fewer cases of childhood asthma; and $29 billion in
(Executive Order 14037 of August 5, 2021, “Strengthening
annual net benefits. EPA also estimated the technology
American Leadership in Clean Cars and Trucks,” 86
required to meet the new rule will cost between $2,500 and
Federal Register 43583). The first rule, promulgated by the
$8,300 per vehicle.
U.S. Environmental Protection Agency (EPA) in January
2023, set new standards for nitrogen oxides (NOx) and other
On February 9, 2023, S.J.Res. 11 was introduced in
criteria pollutant emissions for new medium- and heavy-
Congress, providing for disapproval of EPA’s January 2023
duty vehicles and engines starting in model year (MY)
heavy-duty vehicles rule under the Congressional Review
2027. A second rule, to be promulgated by EPA and the
Act. Sponsors of the resolution state that the new standards
National Highway Traffic Safety Administration (NHTSA),
are overly challenging to implement, would make the cost
is expected to set more stringent GHG emission and fuel
of new trucks prohibitive for small business owners
efficiency standards for the sector beginning with MY2027.
(potentially increasing pollution by incentivizing operators
to keep older, higher-emitting trucks on the road for
Emissions from Heavy-Duty Vehicles
longer), and would increase supply chain costs.
The medium- and heavy-duty vehicle and engine sector
(defined at 40 C.F.R. §1037 and 49 C.F.R. §523) generally
Greenhouse Gas Emission Standards
includes tractor-trailers, vocational vehicles, buses, and
In October 2016, EPA and NHTSA jointly published the
heavy-duty pickup trucks and vans. EPA reports that
current set of GHG emission and fuel efficiency standards
“pollution from heavy-duty trucks contributes to poor air
for medium- and heavy-duty vehicles and engines (81
quality and health across the country, especially in
Federal Register 73478) through their authorities under the
overburdened and underserved communities.” These
CAA and the Energy Independence and Security Act of
vehicles are the largest contributor to mobile source
2007 (EISA, P.L. 110-140). These standards, referred to as
emissions of NOx (about 32% in 2017, the most recently
Phase 2, expanded on the Phase 1 standards (promulgated
available inventory; NOx reacts in the atmosphere to form
in September 2011, for MY2014 through MY2018; 76
ground-level ozone, or smog), as well as particulate matter,
Federal Register 57106) and introduced first-ever controls
carbon monoxide, and air toxics. Further, according to
on trailers (the part of the vehicle pulled by the tractor—
EPA’s Inventory of U.S. Greenhouse Gas Emissions and
since vacated) and glider vehicles (a new chassis combined
Sinks: 1990–2019 (published April 2021), medium- and
with an older engine). The standards phase-in between
heavy-duty vehicles emitted 456.6 million metric tons of
MY2021 and MY2027 for engines and vehicles and
carbon dioxide (CO2) in 2019 (about 25% of total CO2
between MY2018 and MY2027 for gliders (see Figure 1).
emissions from the U.S. transportation sector).
The Phase 2 rule maintained the underlying regulatory
Current Standards
structure developed in Phase 1, such as the general
Criteria Pollutant Emission Standards
categorization of medium- and heavy-duty vehicles and the
separate standards for engines and vehicles. It also retained
In January 2023, EPA finalized the current set of emission
the Phase 1 averaging, banking, and trading compliance
standards for criteria, or common, pollutants from heavy-
provisions and its flexibilities for small businesses.
duty vehicles and engines (88 Federal Register 4269)
However, unlike Phase 1, the rule established “technology-
through its authorities under the Clean Air Act (CAA). The
advancing standards”—standards based not only on
new standards, to begin in MY2027, would require original
currently available technologies but also on utilization of
equipment manufacturers to reduce tailpipe emissions of
technologies under development or not widely deployed.
NOx by approximately 80% and particulate matter by 50%,
These could include advancements in the engine,
compared with the previous standards, and increase the
transmission, driveline, aerodynamic design, lower rolling
regulatory useful life period of vehicles by 1.5-2.5 times
resistance tires, and extended idle reduction technologies.
and the emissions warranty period by 2.8-4.5 times,
depending on the class of vehicle. The rule requires
manufacturers to better ensure engines and emission control
The Phase 3 proposal, announced in Executive Order
systems work properly on the road for a longer period of
14037, is scheduled for release in the spring of 2023.
time and to demonstrate that engines are designed to
https://crsreports.congress.gov
Heavy-Duty Vehicles, Air Pollution, and Climate Change
Figure 1. CO2 and Fuel Consumption Reductions from the Phase 2 Medium- and Heavy-Duty Vehicle Standards
Source: Courtesy of International Council on Clean Transportation, under a Share Alike license of Creative Commons.
Notes: Classifications defined at 49 C.F.R. §523.2 and 49 C.F.R. §565.15.
Selected Issues
Glider Kit and Glider Vehicle Provisions
Some selected issues from the Phase 2 GHG rulemaking
The term glider kit is used in the vehicle industry to
that have remained of interest to Congress include the
describe a chassis and cab assembly that is produced
following:
without a new engine, transmission, or rear axle. A third
party then typically installs used parts to complete the
Trailer Provisions
assembly. Historically, gliders have been used as a means
The Phase 2 rule included standards for both engine
to salvage valuable components from vehicles that were
emissions and the vehicle as a whole, including
badly damaged in collisions. Prior to the Phase 2
requirements for improvements to the aerodynamics of
rulemaking, EPA and NHTSA observed a sharp increase in
freight trailers. In November 2021, the U.S. Court of
glider sales, suggesting to them that gliders were being used
Appeals for the D.C. Circuit granted the Truck Trailer
to circumvent standards for safety and emissions (e.g., NOx
Manufacturing Association’s petition for review, holding
and particulates). For this reason, EPA moved to apply
that EPA cannot regulate trailers under CAA Section 202(a)
current emission standards to gliders under the Phase 2 rule.
because trailers are not “self-propelled” motor vehicles. A
majority of the three-judge panel also held that NHTSA
In July 2017, several glider kit manufacturers filed a
does not have authority to regulate trailers under EISA
petition for reconsideration with EPA, arguing that gliders
because trailers use no fuel.
should not be considered “new motor vehicles” under the
CAA, and that EPA thus lacked the authority to regulate
Racecar Provisions
them. In November 2017, EPA issued a proposed repeal of
In the Phase 2 proposal, EPA included language that was
the requirements (82 Federal Register 53442). Upon
intended to clarify tampering provisions with respect to
review, the White House Office of Information and
nonroad vehicles. Industry groups claimed that the
Regulatory Affairs reportedly informed EPA that the
provisions would prevent owners from modifying motor
agency needed a regulatory impact analysis before it could
vehicles used exclusively for racing. EPA removed the
finalize the repeal. In July 2018, EPA announced an 18-
language from the final rule. Nevertheless, some argue that
month enforcement pause on the Phase 2 production limits
the underlying compliance uncertainty remains. Legislation
for glider vehicles as it reconsidered the rule. No further
to clarify it has been proposed in several Congresses (most
action has been taken since.
recently H.R. 3281/S. 2736 in the 117th Congress). In
December 2016, the Racing Enthusiasts and Suppliers
Richard K. Lattanzio, Specialist in Environmental Policy
Coalition filed a petition with the D.C. Circuit to address
IF12043
the uncertainty. On August 12, 2022, the three-judge panel
dismissed the petition for review.
https://crsreports.congress.gov
Heavy-Duty Vehicles, Air Pollution, and Climate Change
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
United States Government, are not subject to copyright protection in the United States. Any CRS Report may be
reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include
copyrighted images or material from a third party, you may need to obtain the permission of the copyright holder if you
wish to copy or otherwise use copyrighted material.
https://crsreports.congress.gov | IF12043 · VERSION 5 · UPDATED
Updated February 14, 2023
Heavy-Duty Vehicles, Air Pollution, and Climate Change
In August 2021, the Biden Administration announced plans
prevent vehicle drivers from tampering with emission
to reduce greenhouse gas (GHG) emissions and other air
control devices. EPA estimated that by 2045, the rule would
pollutants from medium- and heavy-duty vehicles and
result in, inter alia, up to 2,900 fewer premature deaths;
engines through a series of rulemakings over three years
18,000 fewer cases of childhood asthma; and $29 billion in
(Executive Order 14037 of August 5, 2021, “Strengthening
annual net benefits. EPA also estimated the technology
American Leadership in Clean Cars and Trucks,” 86
required to meet the new rule will cost between $2,500 and
Federal Register 43583). The first rule, promulgated by the
$8,300 per vehicle.
U.S. Environmental Protection Agency (EPA) in January
2023, set new standards for nitrogen oxides (NOx) and other
On February 9, 2023, S.J.Res. 11 was introduced in
criteria pollutant emissions for new medium- and heavy-
Congress, providing for disapproval of EPA’s January 2023
duty vehicles and engines starting in model year (MY)
heavy-duty vehicles rule under the Congressional Review
2027. A second rule, to be promulgated by EPA and the
Act. Sponsors of the resolution state that the new standards
National Highway Traffic Safety Administration (NHTSA),
are overly challenging to implement, would make the cost
is expected to set more stringent GHG emission and fuel
of new trucks prohibitive for small business owners
efficiency standards for the sector beginning with MY2027.
(potentially increasing pollution by incentivizing operators
to keep older, higher-emitting trucks on the road for
Emissions from Heavy-Duty Vehicles
longer), and would increase supply chain costs.
The medium- and heavy-duty vehicle and engine sector
(defined at 40 C.F.R. §1037 and 49 C.F.R. §523) generally
Greenhouse Gas Emission Standards
includes tractor-trailers, vocational vehicles, buses, and
In October 2016, EPA and NHTSA jointly published the
heavy-duty pickup trucks and vans. EPA reports that
current set of GHG emission and fuel efficiency standards
“pollution from heavy-duty trucks contributes to poor air
for medium- and heavy-duty vehicles and engines (81
quality and health across the country, especially in
Federal Register 73478) through their authorities under the
overburdened and underserved communities.” These
CAA and the Energy Independence and Security Act of
vehicles are the largest contributor to mobile source
2007 (EISA, P.L. 110-140). These standards, referred to as
emissions of NOx (about 32% in 2017, the most recently
Phase 2, expanded on the Phase 1 standards (promulgated
available inventory; NOx reacts in the atmosphere to form
in September 2011, for MY2014 through MY2018; 76
ground-level ozone, or smog), as well as particulate matter,
Federal Register 57106) and introduced first-ever controls
carbon monoxide, and air toxics. Further, according to
on trailers (the part of the vehicle pulled by the tractor—
EPA’s Inventory of U.S. Greenhouse Gas Emissions and
since vacated) and glider vehicles (a new chassis combined
Sinks: 1990–2019 (published April 2021), medium- and
with an older engine). The standards phase-in between
heavy-duty vehicles emitted 456.6 million metric tons of
MY2021 and MY2027 for engines and vehicles and
carbon dioxide (CO2) in 2019 (about 25% of total CO2
between MY2018 and MY2027 for gliders (see Figure 1).
emissions from the U.S. transportation sector).
The Phase 2 rule maintained the underlying regulatory
Current Standards
structure developed in Phase 1, such as the general
Criteria Pollutant Emission Standards
categorization of medium- and heavy-duty vehicles and the
separate standards for engines and vehicles. It also retained
In January 2023, EPA finalized the current set of emission
the Phase 1 averaging, banking, and trading compliance
standards for criteria, or common, pollutants from heavy-
provisions and its flexibilities for small businesses.
duty vehicles and engines (88 Federal Register 4269)
However, unlike Phase 1, the rule established “technology-
through its authorities under the Clean Air Act (CAA). The
advancing standards”—standards based not only on
new standards, to begin in MY2027, would require original
currently available technologies but also on utilization of
equipment manufacturers to reduce tailpipe emissions of
technologies under development or not widely deployed.
NOx by approximately 80% and particulate matter by 50%,
These could include advancements in the engine,
compared with the previous standards, and increase the
transmission, driveline, aerodynamic design, lower rolling
regulatory useful life period of vehicles by 1.5-2.5 times
resistance tires, and extended idle reduction technologies.
and the emissions warranty period by 2.8-4.5 times,
depending on the class of vehicle. The rule requires
manufacturers to better ensure engines and emission control
The Phase 3 proposal, announced in Executive Order
systems work properly on the road for a longer period of
14037, is scheduled for release in the spring of 2023.
time and to demonstrate that engines are designed to
https://crsreports.congress.gov
Heavy-Duty Vehicles, Air Pollution, and Climate Change
Figure 1. CO2 and Fuel Consumption Reductions from the Phase 2 Medium- and Heavy-Duty Vehicle Standards
Source: Courtesy of International Council on Clean Transportation, under a Share Alike license of Creative Commons.
Notes: Classifications defined at 49 C.F.R. §523.2 and 49 C.F.R. §565.15.
Selected Issues
Glider Kit and Glider Vehicle Provisions
Some selected issues from the Phase 2 GHG rulemaking
The term glider kit is used in the vehicle industry to
that have remained of interest to Congress include the
describe a chassis and cab assembly that is produced
following:
without a new engine, transmission, or rear axle. A third
party then typically installs used parts to complete the
Trailer Provisions
assembly. Historically, gliders have been used as a means
The Phase 2 rule included standards for both engine
to salvage valuable components from vehicles that were
emissions and the vehicle as a whole, including
badly damaged in collisions. Prior to the Phase 2
requirements for improvements to the aerodynamics of
rulemaking, EPA and NHTSA observed a sharp increase in
freight trailers. In November 2021, the U.S. Court of
glider sales, suggesting to them that gliders were being used
Appeals for the D.C. Circuit granted the Truck Trailer
to circumvent standards for safety and emissions (e.g., NOx
Manufacturing Association’s petition for review, holding
and particulates). For this reason, EPA moved to apply
that EPA cannot regulate trailers under CAA Section 202(a)
current emission standards to gliders under the Phase 2 rule.
because trailers are not “self-propelled” motor vehicles. A
majority of the three-judge panel also held that NHTSA
In July 2017, several glider kit manufacturers filed a
does not have authority to regulate trailers under EISA
petition for reconsideration with EPA, arguing that gliders
because trailers use no fuel.
should not be considered “new motor vehicles” under the
CAA, and that EPA thus lacked the authority to regulate
Racecar Provisions
them. In November 2017, EPA issued a proposed repeal of
In the Phase 2 proposal, EPA included language that was
the requirements (82 Federal Register 53442). Upon
intended to clarify tampering provisions with respect to
review, the White House Office of Information and
nonroad vehicles. Industry groups claimed that the
Regulatory Affairs reportedly informed EPA that the
provisions would prevent owners from modifying motor
agency needed a regulatory impact analysis before it could
vehicles used exclusively for racing. EPA removed the
finalize the repeal. In July 2018, EPA announced an 18-
language from the final rule. Nevertheless, some argue that
month enforcement pause on the Phase 2 production limits
the underlying compliance uncertainty remains. Legislation
for glider vehicles as it reconsidered the rule. No further
to clarify it has been proposed in several Congresses (most
action has been taken since.
recently H.R. 3281/S. 2736 in the 117th Congress). In
December 2016, the Racing Enthusiasts and Suppliers
Richard K. Lattanzio, Specialist in Environmental Policy
Coalition filed a petition with the D.C. Circuit to address
IF12043
the uncertainty. On August 12, 2022, the three-judge panel
dismissed the petition for review.
https://crsreports.congress.gov
Heavy-Duty Vehicles, Air Pollution, and Climate Change
Disclaimer
This document was prepared by the Congressional Research Service (CRS). CRS serves as nonpartisan shared staff to
congressional committees and Members of Congress. It operates solely at the behest of and under the direction of Congress.
Information in a CRS Report should not be relied upon for purposes other than public understanding of information that has
been provided by CRS to Members of Congress in connection with CRS’s institutional role. CRS Reports, as a work of the
United States Government, are not subject to copyright protection in the United States. Any CRS Report may be
reproduced and distributed in its entirety without permission from CRS. However, as a CRS Report may include
copyrighted images or material from a third party, you may need to obtain the permission of the copyright holder if you
wish to copy or otherwise use copyrighted material.
https://crsreports.congress.gov | IF12043 · VERSION 5 · UPDATED