California NOx Omnibus Regulation Requires 90 Percent NOx Reduction by 2027

On August 27, 2020, the California Air Resources Board (CARB) approved the Heavy-Duty Low NOx Omnibus Regulation (Omnibus Regulation), which requires heavy-duty truck manufacturers to achieve stringent nitrogen oxide (NOx) emission standards. The Omnibus Regulation follows the board’s June 2020 approval of the Advanced Clean Trucks regulation, which requires medium- and heavy-duty truck manufacturers to increase the sales of zero-emission models. Both rules require that certain compliance milestones be met by 2024.

The Omnibus Regulation reduces the NOx emission standards by approximately 75 percent below current standards in 2024 and by 90 percent below current standards in 2027. In addition to the NOx emission standards, the Omnibus Regulation establishes numerous requirements on new heavy-duty trucks and engines. These requirements, which will also be phased in, include a substantial reduction in particulate matter emissions, new in-use engine testing procedures, idling requirements, and extension of engine warranties.