California Air Resources Board

A key part of CARB’s 2016 Mobile Source Strategy and State SIP Strategy was the establishment of stricter oxides of nitrogen (NOx) engine emission standards for on-road heavy-duty diesel engines via the Heavy-Duty Low NOx Omnibus (Omnibus) regulation. This rulemaking was critical for helping attain federal health-based air quality standards for ozone in 2031 in the South Coast and San Joaquin Valley air basins, and fine particulate matter (PM2.5) standards in the next decade.
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