CARB’s Omnibus regulation sets updated emissions standards for engine manufactures to certify against. California first issued its standard for lowering NOx from truck exhaust in 2002, and it has been updated several times.

The latest regulation, approved in December 2021 and going into effect January 1 2024, set emissions standards for engine model years spanning from 2024 to 2031. These standards mandate a 90% reduction in NOx emissions from heavy-duty on-road engines compared to existing standards, with a phased implementation scheduled from 2024 to 2031.

CARB NOx requirement for 2024 reduces NOx emissions requirements from 0.2 g/hp-hr to 0.05 g/hp-hr. 

EMA expressed concerns and engaged in discussions regarding CARB’s issuance of heavy-duty truck standards. This dialogue led to an agreement in July 2023 for CARB to revise the standards. As part of the agreement, CARB committed to aligning key provisions of the Omnibus regulation’s emission standards, associated test procedures, and enforcement provisions for 2027 and subsequent model engines with corresponding federal requirements. CARB released the proposed amendments for public comment in December 2023

Omnibus Legacy Provision

• CARB will allow an engine manufacturer to sell a “legacy engine” (EPA 2024 Product –> MY23 NOx/PM and MY24 GHG) in limited quantities as % of total CA diesel sales.
• The higher NOx/PM levels of the legacy engines sales must be offset through NOx and PM mitigation, which includes monetary compensation and community projects.