The US Environmental Protection Agency (EPA) finalized more stringent NO_x emissions limits for model year 2027 and later heavy-duty engines and vehicles. Relative to current rules, the new standards are more than 80% stronger, increase useful life of governed vehicles by 1.5–2.5 times, and will yield emissions warranties that are 2.8–4.5 times longer.

National heavy-duty vehicle NO_x emissions (annual US tons) for calendar years 2027 - 2045

The announcement is the first of three major actions being taken under EPA’s Clean Trucks Plan, announced in August 2021, which will move the US heavy-duty trucking fleet towards low-carbon and electric technologies. (Earlier post.)

The set of regulatory actions that make up the Clean Trucks Plan are as follows:

• Setting stronger nitrogen oxide (NO_x) standards for heavy duty trucks beginning in model year (MY) 2027 and tightening the Phase 2 greenhouse gas (GHG) emissions for MY 2027 and beyond.

• Setting stronger emissions standards for medium-duty commercial vehicles for MY 2027 and later. These revised standards will be proposed in combination with new standards for light-duty vehicles for MY 2027 and beyond.

• Setting Phase 3 GHG standards for heavy-duty vehicles beginning as soon as MY 2030 that are significantly stronger than the MY 2027 GHG standards.

The newly announced rule does not include final action regarding the proposed targeted updates to the existing Heavy-Duty Greenhouse Gas Emissions Phase 2 program (HD GHG Phase 2). EPA intends to consider potential changes to certain HD GHG Phase 2 standards as part of the Phase 3 GHG rulemaking.

In the coming months, EPA intends to release the proposals for the remaining two steps in the Clean Trucks Plan. These include the proposed Phase 3 greenhouse gas (GHG) standards for heavy-duty vehicles beginning in Model Year 2027, as well as the proposed multipollutant standards for light- and medium-duty vehicles beginning in Model Year 2027.

Now that the Agency has taken this final action on reducing NO_x emissions nationally from Heavy-Duty trucks, EPA will complete the assessment of the technical and legal record before the Agency and prioritize issuing decisions on the three pending Heavy-Duty program waiver requests from the State of California in early 2023.