California Air Resources Board

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SACRAMENTO – Clean Truck Check, formerly known as the Heavy-Duty Inspection and Maintenance Regulation, was approved by the California Air Resources Board (CARB) in 2021. The program ensures heavy-duty vehicles operating in California are well-maintained, and repaired quickly when needed, to reduce emissions and improve public health statewide, especially in disadvantaged communities disproportionately impacted by air pollution. When fully implemented, the regulation is projected to reduce statewide NOx emissions by over 81 tons per day and PM emissions by 0.7 tons per day in 2037. Together, these emissions reductions will result in over 7,500 avoided premature deaths.  

Clean Truck Check applies to nearly all diesel and alternative fuel heavy-duty vehicles with a gross vehicle weight rating (GVWR) over 14,000 pounds that operate on California public roads and highways even if they are not registered in California. This includes public vehicles (federal, state, and local government); motorcoaches; transit, shuttle and school buses; hybrid vehicles; commercial vehicles; personal vehicles; California registered motorhomes; single vehicle fleets; and vehicles registered outside of California (not including motorhomes). 

Clean Truck Check has been implemented in three phases. Phase 1 began January 1, 2023. This initial phase began with the deployment of Remote Emissions Monitoring Devices (REMD). REMD monitor the exhaust emissions of passing heavy-duty vehicles and flag potential high emitters that may receive a Notice to Submit to Testing (NST). NST’s require vehicle owners to submit a passing compliance test to CARB, after any necessary emissions-related repairs are made, within 30 days of receipt of the notice. Failure to comply and remedy emissions-related concerns could result in the vehicle being deemed non-compliant and subject to enforcement action, additional compliance testing, penalties, and/or CA DMV registration holds. 

Phase 2 of the program began October 1, 2023. This phase requires vehicle owners who are subject to the program to report their vehicles in the Clean Truck Check, Vehicle Inspection System (CTC-VIS) annual vehicle compliance fees. Phase 2 also launched freight contractor, broker, and applicable freight facility (i.e., ports and railyards) requirements. Freight contractors must only contract with compliant vehicles or fleets and brokers must only arrange transportation within California through motor carriers with compliant vehicles or fleets. Ports and railyards must ensure vehicle compliance status at the time of entry, or attempted entry. 

Phase 3 of Clean Truck Check requires heavy-duty vehicle owners to conduct emissions compliance testing on their vehicles. This is similar to California’s Smog Check program for cars. Emissions compliance testing requirements were effective October 1, 2024, and testing deadlines began January 1, 2025. This phase requires the submission of a passing emissions compliance test as part of the vehicle’s compliance demonstration. Nearly all vehicles are subject to twice per year testing and, subsequently, vehicles equipped with an On-Board Diagnostic (OBD) system will be subject to quarterly testing beginning October 1, 2027. Agricultural Vhicles, as defined by the regulation, and California-registered motorhomes are only required to test once per year. Testing requirements vary based on engine model year. For California-registered vehicles, the compliance testing deadlines are linked to each vehicle’s DMV registration expiration/renewal date. For vehicles registered outside of California and for vehicles exempt from DMV registration requirements, compliance deadlines are based on the last number of a vehicle’s vehicle identification number (VIN). Passing test results may be submitted up to 90 days before a compliance deadline. Testing should be performed in a timely manner to allow time for any necessary repairs, and to avoid penalties and possible California DMV registration holds. 

More Information 

Clean Truck Check-Vehicle Inspection System (CTC-VIS) Reporting Database Training Videos and Webinars 
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CARB Truck Regulations 
CARB TruckStop X

Contact: hdim@arb.ca.gov