California Air Resources Board

In 2013, CARB adopted optional low oxides of nitrogen (NO_x) emission standards for on-road heavy-duty engines. CARB staff encourages engine manufacturers to introduce new technologies to reduce NO_x emissions below the current mandatory on-road heavy-duty diesel engine emission standards for model years 2010 and later. California’s current emission standards for heavy-duty engines are contained in California Code of Regulations, Title 13, section 1956.8. The optional low NO_x standards will encourage engine manufacturers to showcase new technologies and could be utilized to prioritize funding in incentive programs such as the Carl Moyer Memorial Air Quality Standards Attainment Program.