The US Environmental Protection Agency (EPA) announced two new proposed federal emissions standards spanning light-, medium- and heavy-duty vehicles for model year 2027 and beyond. EPA projects that the proposed standards would avoid nearly 10 billion tons of CO₂ emissions—equivalent to more than twice the total US CO₂ emissions in 2022—through 2055. Together, the proposals would reduce oil imports by approximately 20 billion barrels.

Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles

The first set of proposed standards, the “Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles,” builds on EPA’s existing emissions standards for passenger cars and light trucks for MYs 2023 through 2026. The proposal retains the proven regulatory design of previous EPA standards for light-duty vehicles, but leverages advances in clean car technology to further reduce both climate pollution and smog- and soot-forming emissions.

The light-duty vehicle category includes passenger cars and light trucks consistent with previous EPA criteria pollutant and GHG rules. In this proposed rule, heavy-duty Class 2b and 3 vehicles are referred to as "medium-duty vehicles" (MDVs) to distinguish them from Class 4 and higher vehicles that remain under the heavy-duty program. EPA has not previously used the MDV nomenclature, referring to these larger vehicles in prior rules as light-heavy-duty vehicles, heavy-duty Class 2b and 3 vehicles, or heavy-duty pickups and vans.

In the context of this rule, the MDV category includes primarily large pickups and vans with a gross vehicle weight rating (GVWR) of between 8,501 and 14,000 pounds and excludes vehicles used primarily as passenger vehicles (medium-duty passenger vehicles, or MDPVs).

The proposed program consists of several key elements:

• More stringent emissions standards for criteria pollutants;

• More stringent emissions standards for GHGs;

• Changes to certain optional credit programs;

• Durability provisions for light-duty electrified vehicle batteries;

• Warranty provisions for both electrified vehicles and diesel engine-equipped vehicles; and

• Various improvements to several elements of the existing light-duty program that will also apply to the proposed program.

The levels of stringency proposed in this rule for both light- and medium-duty vehicles continue the trend over the past fifty years for criteria pollutants, and over the past decade for GHGs, of EPA establishing numerically lower emissions standards based on continued advancements in emissions control technology.

While EPA’s feasibility assessments in past rulemakings were predominantly based on advancements in ICE technologies that provided incremental emissions reductions, in this proposal EPA’s technology feasibility assessment includes the increasing availability of zero and near-zero tailpipe emissions technologies, including PEVs, as a cost-effective compliance technology. The technological feasibility of PEVs is further bolstered by the economic incentives provided in the IRA and the auto manufacturers’ stated plans for producing significant volumes of zero and near-zero emission vehicles in the timeframe of this rule. Because of this increased feasibility of zero and near-zero tailpipe emissions technologies, EPA believes it is appropriate to propose over the six-year timeframe of these standards even lower emissions standards than has been possible in past rulemakings.

—Proposed Rule: Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles

GHG emissions standards. For light-duty vehicles, EPA is proposing standards that would increase in stringency each year over a six-year period, from MYs 2027-2032. The proposed standards are projected to result in an industry-wide average target for the light-duty fleet of 82 grams/mile (g/mile) of CO₂ in MY 2032, representing a 56% reduction in projected fleet average GHG emissions target levels from the existing MY 2026 standards.

For medium-duty vehicles, EPA’s proposed standards for MDVs would increase in stringency year over year from MY 2027 through MY 2032. When phased in, the MDV standards are projected to result in an average target of 275 grams/mile of CO₂ by MY 2032, which would represent a reduction of 44 percent compared to the current MY 2026 standards.

The light-duty CO₂ standards continue to be footprint-based, with separate standards curves for cars and light trucks. The medium-duty vehicle standards continue to be based on a work-factor metric designed for commercially-oriented vehicles, which reflects a combination of payload, towing and 4-wheel drive equipment.

EPA EPA is proposing to revise the current air conditioning (AC) credits program in two ways. First, for AC system efficiency credits under the light-duty GHG program, EPA is proposing to limit the eligibility for these voluntary credits for tailpipe CO₂ emissions control to ICE vehicles starting in MY 2027 (i.e., BEVs would not earn AC efficiency credits because even without such credits they would be counted as zero g/mi CO₂ emissions for compliance calculations). Second, EPA is proposing to remove refrigerant-based AC provisions for both light- and medium-duty vehicles because, under a separate rulemaking, EPA has proposed to disallow the use of high global warming potential refrigerants.

EPA is also proposing to sunset the off-cycle credits program for both light and medium-duty vehicles.

EPA is not reopening its averaging, banking, and trading provisions, which continue to be a central part of its fleet average standards compliance program and which help manufacturers to employ a wide range of compliance paths. EPA is also not proposing to restore multiplier incentives for BEVs, PHEVs and fuel cell vehicles, which currently end after MY 2024 under existing regulations.

EPA also is proposing changes to the provisions for small volume manufacturers (i.e., production of less than 5,000 vehicles per year) to transition them from the existing approach of unique case-by-case alternative standards to the primary program standards by MY 2032, recognizing that additional lead time is appropriate given their challenges in averaging across limited product lines.

Criteria pollutant standards. For light-duty vehicles, EPA is proposing non-methane organic gases (NMOG) plus nitrogen oxides (NO_x) standards that would phase-down to a fleet average level of 12 mg/mi by MY 2032, representing a 60% reduction from the existing 30 mg/mi standards for MY 2025 established in the Tier 3 rule in 2014.

For medium- duty vehicles, EPA is proposing NMOG+NO_x standards that would require a fleet average level of 60 mg/mi by MY 2032, representing a 66% to 76% reduction from the Tier 3 standards of 178 mg/mi for Class 2b vehicles and 247 mg/mi for Class 3 vehicles. EPA is proposing cold temperature (-7°C) NMOG+NO_x standards for light- and medium-duty vehicles to ensure robust emissions control over a broad range of operating conditions.

For both light-duty and all medium-duty vehicles, EPA is proposing a particulate matter (PM) standard of 0.5 mg/mi and a requirement that the standard be met across three test cycles, including a cold temperature (-7°C) test. This proposed standard would revise the existing PM standards established in the 2014 Tier 3 rule. Through the application of readily available emissions control technology and requiring compliance across the broad range of driving conditions represented by the three test cycles, EPA projects the standards will reduce tailpipe PM emissions from ICE vehicles by more than 95%. In addition to reducing PM emissions, the proposed standards would reduce emissions of mobile source air toxics.

EPA is also proposing requirements to certify compliance with criteria pollutants standards for medium-duty vehicles with high gross combined weight rating (GCWR) under the heavy-duty engine program, changes to medium-duty vehicle refueling emissions requirements for incomplete vehicles, and several NMOG+NO_x provisions aligned with the CARB Advanced Clean Cars II program for light-duty vehicles.

EPA is proposing changes to the carbon monoxide and formaldehyde standards for light- and medium-duty vehicles, including at -7 °C. EPA is also proposing to eliminate commanded enrichment for ICE-powered vehicles for power and component protection. Averaging, banking, and trading provisions may be employed within the new program, and with certain limitations, credits may be transferred from the Tier 3 program to provide manufacturers with flexibilities in developing compliance strategies.

Future gasoline fuel property standards. EPA is seeking comment on potential future gasoline fuel property standards aimed at further reducing PM emissions, for consideration in a possible subsequent rulemaking, which could provide an important complement to the vehicle standards being proposed.

Battery durability. EPA is proposing new battery durability requirements for light-duty and medium-duty BEVs and PHEVs. In addition, the agency is proposing revised regulations which would include BEV and PHEV batteries and associated electric powertrain components under existing emission warranty provisions. Relatedly, EPA is also proposing the addition of two new grouping definitions for BEVs and PHEVs (monitor family and battery durability family), new reporting requirements, and a new calculation for the PHEV charge depletion test to support the battery durability requirements.

The proposed standards are also projected to accelerate the transition to electric vehicles. Depending on the compliance pathways manufacturers select to meet the standards, EPA projects that EVs could account for 67% of new light-duty vehicle sales and 46% of new medium-duty vehicle sales in MY 2032.

Greenhouse Gas Standards for Heavy-Duty Vehicles - Phase 3

The second set of proposed standard, the “Greenhouse Gas Standards for Heavy-Duty Vehicles - Phase 3,” would apply to heavy-duty vocational vehicles (such as delivery trucks, refuse haulers or dump trucks, public utility trucks, transit, shuttle, school buses) and trucks typically used to haul freight. These standards would complement the criteria pollutant standards for MY 2027 and beyond heavy-duty vehicles that EPA finalized in December 2022 and represent the third phase of EPA’s Clean Trucks Plan.

EPA is proposing progressively more stringent GHG emission standards that would apply to MYs 2027-2032 and later for numerous vocational vehicle and tractor subcategories.

Proposed MY 2032 and Later Vocational Vehicle CO₂ Emission Standards (grams/ton-mile) by Regulatory Subcategory

Proposed MY 2032 and Later Tractor CO₂ Emission Standards (grams/ton-mile) by Regulatory Subcategory

The proposed standards do not mandate the use of a specific technology, and EPA anticipates that a compliant fleet under the proposed standards would include a diverse range of technologies (e.g., transmission technologies, aerodynamic improvements, engine technologies, battery electric powertrains, hydrogen fuel cell powertrains, etc.).

EPA expects the proposed GHG emission standards would lead to an increase in HD ZEVs relative to the reference case without the proposed rule, which would also result in reductions of vehicle emissions of non-GHG pollutants that contribute to ambient concentrations of ozone, particulate matter (PM_2.5), NO₂, CO, and air toxics.

Although EPA projects that non-GHG emissions from power generation would increase as a result of the increased demand for electricity associated with the proposal, the agency expects those projected impacts to decrease over time due to EGU regulations and changes in the future power generation mix, including impacts of the IRA. EPA also projects that non-GHG emissions from refineries would decrease as a result of the lower demand for liquid fuel associated with the proposed GHG standards.