Final rule · 2026-02350

Air Plan Revisions; California; Heavy-Duty Vehicle Inspection and Maintenance Program

The U.S. Environmental Protection Agency (EPA) is taking final action to partially approve and partially disapprove a submission by the State of California to revise its State Implementation Plan (SIP) relating to the control of emissions from non-gasoline combustion vehicles over 14,000 pounds. The EPA's partial approval will allow the submitted Heavy-Duty Inspection and Maintenance Regulation ("HD I/M Regulation") to become federally enforceable as part of the California SIP with respect to vehicles registered within the State. The EPA is partially disapproving the submission to the extent that the HD I/M Regulation purports to apply to out-of-state vehicles as inconsistent with the Clean Air Act (CAA), because the State has not provided adequate assurances under CAA section 110(a)(2)(E)(i) that implementation of the SIP is not prohibited by Federal law. The partial disapproval will not trigger CAA section 179 sanctions because the submittal is not a required submission under CAA section 110(a)(2).