Summary
Details
- California
California’s Clean Truck Check (HD I/M) program applies to most diesel and alternative-fuel heavy-duty vehicles with a gross vehicle weight rating (GVWR) above 14,000 pounds operating in California, including many vehicles registered outside the state.
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Background
California introduced the Clean Truck Check program under Senate Bill 210 to improve heavy-duty vehicle emissions compliance and reduce smog-forming pollution from trucks and buses. CARB approved the regulation in December 2021, with phased implementation beginning in January 2023. The program combines periodic emissions testing with roadside emissions monitoring and expanded enforcement mechanisms.
The regulation applies to nearly all diesel and alternative-fuel heavy-duty vehicles operating on California public roads, even if they are registered outside the state. Covered vehicle types include commercial trucks, buses, hybrid heavy-duty vehicles, and some motorhomes. Exemptions apply to certain categories such as zero-emission vehicles, military tactical vehicles, and authorized emergency vehicles.
Reporting Requirements
To remain compliant, vehicle owners must:
Report vehicles through the Clean Truck Check Vehicle Inspection System (CTC-VIS)
Pay an annual compliance fee
Submit passing emissions compliance tests according to the required schedule
Testing methods depend on vehicle type and model year. Newer OBD-equipped vehicles typically complete electronic emissions testing, while older vehicles may require smoke opacity testing and visual inspections. CARB-certified testers or approved OBD systems must submit results electronically.
Penalties for Noncompliance
CARB uses roadside monitoring systems, audits, and emissions inspections to identify non-compliant vehicles operating in California. Enforcement actions can include financial penalties, DMV registration holds, mandatory referee inspections, and orders requiring vehicles to be repaired before returning to service.
CARB has also begun publishing enforcement settlements related to Clean Truck Check and associated heavy-duty emissions regulations. For example, in January 2025, CARB reached a settlement with Legend Trucking, LLC and Queen Trucking, LLC involving violations of the Clean Truck Check program. The settlement included suspended penalties totaling $47,363 and required the company to bring the affected truck into compliance before operating it in California again.
Current Status
The Clean Truck Check program is fully active, with CARB continuing to expand emissions testing and enforcement activities across California’s heavy-duty vehicle sector. The regulation applies to most diesel and alternative-fuel heavy-duty vehicles over 14,000 lbs GVWR operating on California roads, including many out-of-state trucks.
In 2025 and 2026, the program became the subject of federal regulatory disputes concerning its application to out-of-state and foreign-registered vehicles. In August 2025, EPA proposed partially disapproving California’s HD I/M regulation under the Clean Air Act, arguing that applying the program to non-California vehicles could violate the Commerce Clause of the U.S. Constitution.
In January 2026, EPA finalized a partial disapproval of California’s State Implementation Plan related to Clean Truck Check for out-of-state and out-of-country vehicles. California, however, stated that it would continue enforcing the program for trucks operating in the state regardless of registration location.
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