Regions · California

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Due to its vehicle regulations that preceded the Federal Clean Air Act (CAA) of 1970 and its particularly severe motor vehicle-related air quality air issues, the state of California retains the unique authority as a U.S. state to set emission standards that are equivalent to or more stringent than federal standards. Section 177 of the Clean Air Act authorizes other States to adopt California’s more stringent standards. Currently, 15 States have done so. The California Air Resources Board and the California EPA are the regulatory bodies that are primarily responsible for upholding California’s air quality and transportation regulations. Vehicle emissions are regulated through the LEV (Low Emission Vehicle) program, which served as the basis for U.S. Tier 2 and 3 standards. California has also developed optional low-NOx standards for heavy-duty vehicles. Other programs include the Low-Carbon Fuel Standard, which sets GHG limits for transportation fuels.

Pages in California

California: Heavy-duty: Emissions

Current Standard: California's heavy-duty vehicle emission standards were harmonized with federal standards in 2004, with some differences in applicability limits…

Test Cycles in California

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