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US EPA finalizes Phase 3 GHG standards for heavy-duty vehicles

29 March 2024

The US Environmental Protection Agency (EPA) announced final GHG emission standards for heavy-duty vehicles, such as freight trucks and buses. The Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles - Phase 3 standards phase in over model years 2027 through 2032.

The Phase 3 standards build on the EPA’s Heavy-Duty Phase 2 program from 2016. For heavy-duty vocational vehicles such as delivery trucks, refuse haulers, and public utility trucks, the Phase 3 standards vary according to vehicle type and range up to 60% stronger than the previous Phase 2 standards for MY 2032. For tractors such as day cabs and sleeper cabs on tractor-trailer trucks, the Phase 3 standards range up to 40% stronger than the previous Phase 2 standards for MY 2032.

Percent Reduction from Phase 2 CO2 Emission Standards
Vehicle Category202720282029203020312032
Light-Heavy Vocational17%22%27%32%46%60%
Medium-Heavy Vocational13%16%19%22%31%40%
Heavy-Heavy Vocational--13%15%23%30%
Day Cab Tractors-8%12%16%28%40%
Sleeper Cab Tractor---6%12%25%

While the current Phase 2 standards can be achieved using internal combustion engine vehicles (ICEV), the stringency of Phase 3 standards represents an implicit mandate for zero tailpipe emission vehicles (ZEV). The EPA expects the Phase 3 standards will require the use of a mix of powertrain technologies such as advanced internal combustion engine vehicles, hybrid vehicles (HEV), plug-in hybrid electric vehicles, battery electric vehicles, hydrogen fuel cell vehicles, and hydrogen combustion engine vehicles (H2-ICE).

The Phase 3 standards were proposed in April 2023. Relative to the proposal, EPA’s final rule provides more time in the early model years of the program for the development of vehicle technologies and deployment of charging and refueling infrastructure.

In one scenario, the EPA projects that in model year 2032, the Phase 3 new vehicle technology mix will include 60% ZEVs in the light heavy-duty vocational category, and 25% ZEVs among long haul tractors.

In another example, the EPA projected the following 2032 vehicle technology mix:

In parallel to the Phase 3 rule, the Joint Office of Energy and Transportation and the Department of Energy, in collaboration with the Department of Transportation and the EPA, recently announced the National Zero Emission Freight Corridor Strategy, a government action plan for deploying a zero-emission freight network by 2040.

Source: US EPA