The U.S. Environmental Protection Agency (EPA) recently issued a decision that grants two requests for waivers of pre-emption regarding four California Air Resource Board (CARB) regulations related to California’s heavy-duty vehicle and engine-emission standards.

Under the Clean Air Act, California can exercise broad discretion to adopt emissions requirements to meet the state’s air-quality challenges. However, state officials must seek waivers from the EPA for new motor-vehicle emission standards. In this instance, CARB requested two waivers for regulations relating to heavy-duty vehicles and engines. After reviewing the technical information provided by CARB, and those submitted by the public, and applying the ...