US EPA grants waiver for California’s ACC II, Omnibus regulations

18 December 2024

The US Environmental Protection Agency (EPA) has granted two requests from the California Air Resources Board (CARB) for waivers to implement its Advanced Clean Cars II (ACC II) regulations for light-duty vehicles, and its “Omnibus” low-NOx regulation for heavy-duty vehicles and engines. Under the Clean Air Act, California can adopt emission regulations independent from EPA’s regulations but the state must seek a waiver from the EPA for new motor vehicle emission standards.

The ACC II program is a single package of requirements for model year 2026 through 2035 and later for on-road light- and medium-duty engines and vehicles. The ACC II regulations include revisions to both California’s Low Emission Vehicle (LEV IV) and Zero Emission Vehicle (ZEV) regulations.

The ACC II ZEV component specifies future zero emission vehicle requirements in California as a percent of annual new vehicle sales. This requirement increases from 35% in 2026 to 100% in 2035. Plug-in hybrids (PHEV) meeting certain criteria (including a 70 miles all-electric range) can be used to meet up to 20% of the annual ZEV requirements.

The Omnibus regulation established California low-NOx emission standards for model year 2024 and later heavy-duty engines and vehicles. These standards are comparable in stringency to the federal EPA emission standards for model year 2027 and later heavy-duty engines. In July 2023, CARB reached an agreement with a group of leading US engine manufacturers to align the California standards with the EPA 2027 and later emission requirements.

Last year, the EPA also granted a waiver for the CARB Advanced Clean Trucks (ACT) regulation, which established a mandatory percentage schedule for heavy-duty ZEV sales in California. The ACT schedule requires that in 2035, between 40 and 75% (depending on vehicle class) of all heavy-duty vehicle sales in California must be ZEVs.

However, the EPA still has not granted a waiver for the CARB Advanced Clean Fleets (ACF) regulation, which would require that from 2036, 100% of new heavy-duty vehicle sales in California be zero emission vehicles. Other CARB emission regulations that still require an EPA waiver include the In-Use Locomotive Regulation.

The EPA said in a press release that it “continues reviewing additional waiver requests from California and is working to ensure its decisions are durable and grounded by law.”

Source: US EPA