US EPA proposes emission standards for MY 2027 light-duty vehicles, Phase 3 GHG standards for heavy-duty vehicles

12 April 2023

The US Environmental Protection Agency (EPA) announced new proposed federal vehicle emission standards for model year (MY) 2027 and later light- and heavy-duty vehicles. The proposed standards are described in two proposed rules:

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• Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium-Duty Vehicles. This proposal includes two components, a GHG emission regulation and new emission standards for criteria pollutants:
  • GHG Emissions—The new standards would start in MY 2027 and gradually increase through model year 2032, when the rule would ensure that 64%-67% of all new US car sales would be electric vehicles.
  • Criteria pollutants—The standards would require further reductions of NMOG+NOx and PM emissions. The PM standards are expected to drive widespread use of gasoline particulate filters (GPF) to reduce PM emissions from gasoline vehicles.
• Greenhouse Gas Emissions Standards for Heavy-Duty Engines and Vehicles-Phase 3. This proposal includes new GHG emission standards for heavy-duty vocational trucks and tractors to be phased-in from 2027 through 2032. In 2032, the proposed standards would require a ZEV adoption rate of 50% for vocational vehicles, 35% for short-haul trucks, and 25% for long-haul trucks.

Light- and Medium-Duty Vehicle Proposed Standards. The first set of proposed standards, the “Multi-Pollutant Emissions Standards for Model Years 2027 and Later Light-Duty and Medium Duty Vehicles,” would bring new, more stringent emission standards for criteria pollutants and GHGs for light-duty vehicles and Class 2b and 3 (“medium-duty”) vehicles that would phase-in over model years 2027 through 2032.

• For light-duty vehicles, the EPA is proposing standards that would increase in stringency each year over a six-year period, from MY 2027 through 2032. The proposed standards are projected to result in an industry-wide average target for the light-duty fleet of 82 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 (MDV), the proposed standards 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 g/mile of CO₂ by MY 2032, which would represent a reduction of 44% 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 EPA is proposing to revise the footprint standards curves to flatten the slope of each curve and to narrow the numerical stringency difference between the car and truck curves. 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.

The proposed GHG standards are projected to accelerate the transition to electric vehicles. The EPA projects that in MY 2032, EVs could account for 67% of new light-duty vehicle sales and 46% of new medium-duty vehicle sales.

The key changes to the criteria pollutant emission standards are:

• For light-duty vehicles, the EPA proposed NMOG+NOx 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.
• For medium- duty vehicles, the EPA proposed NMOG+NOx 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.
• New cold temperature (-7°C) NMOG+NOx standards are proposed 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, the EPA proposed a 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 (3 mg/mi) established in the 2014 Tier 3 rule.

The EPA projects that the new PM standards will drive widespread use of filters to reduce gasoline particulate matter emissions and the GHG standards will spur greater deployment of CO₂-reducing technologies for gasoline-powered vehicles.

In addition, the EPA has proposed GHG program revisions in several areas, including off-cycle and air conditioning credits, the treatment of upstream emissions associated with zero-emission vehicles and plug-in hybrid electric vehicles in compliance calculations, medium-duty vehicle incentive multipliers, and vehicle certification and compliance. The EPA has also proposed new standards to control refueling emissions from incomplete medium-duty vehicles, and battery durability and warranty requirements for light-duty and medium-duty plug-in vehicles.

A separate regulation, proposed by the Department of Energy (DOE), would also change the methodology for the calculation of CAFE petroleum-equivalent fuel economy ratings for electric vehicles, beginning with MY 2027. The old fuel economy method divided the EV electricity consumption converted to gasoline equivalent by a constant coefficient of 0.15. The concern was that the method was making EVs look cleaner than they really are, thus allowing manufacturers to continue selling more polluting ICE vehicles. The proposed new method, based on life-cycle approach for electricity production, would produce lower EV fuel economy values, making it harder for manufacturers to meet CAFE standards by increasing the EV share in their vehicle fleet.

Heavy-Duty Truck Proposed Standards. The second set of proposed standards, 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 later heavy-duty vehicles that the EPA finalized in December 2022.

The proposed program features several key provisions that include updating the existing MY 2027 GHG emission standards and promulgating new GHG emission standards starting in MY 2028 through 2032 for HD vehicles. Specifically, the EPA is proposing to set progressively more stringent GHG emission standards that would apply to MY 2027, 2028, 2029, 2030, 2031, and 2032.

The proposed standards do not mandate the use of a specific technology, and the EPA anticipates that a compliant heavy-duty fleet would include a mix CO₂-reducing technologies such as transmission technologies, aerodynamic improvements, engine technologies, battery electric powertrains, and hydrogen fuel cell powertrains.

The EPA plans to hold virtual public hearings for both proposed rules—on May 2 and 3 for the heavy-duty Phase 3 rule and on May 9-10 for the light-duty proposal. Public comments on the proposals must be received within 60 (light-duty rule) or 50 (heavy-duty rule) days after the date of publication in the Federal Register.

Source: US EPA