The California Air Resources Board (CARB) enforces some of the most stringent heavy-duty diesel truck regulations in the United States. Any commercial truck operating in California — regardless of registration state — must comply with CARB rules. Key programs include the Clean Truck Check, a biennial opacity inspection for diesel trucks over 14,000 lbs GVWR; the Drayage Truck Rule, which mandates zero-emission vehicles for trucks serving California ports and intermodal railyards; the Advanced Clean Trucks (ACT) rule governing manufacturer ZEV sales quotas; and the Heavy-Duty Vehicle Inspection Program (HDVIP), CARB's roadside enforcement program. All qualifying trucks must be registered in TRUCRS (Truck, Bus, and Off-Road Clean Air Reporting System) and kept current. Non-compliance can result in fines of $1,000 or more per day per vehicle, mandatory Notice to Correct orders, and denial of entry at California ports and railyards.
The Clean Truck Check (CTC) program — formerly known as the Periodic Smoke Inspection Program — requires all heavy-duty diesel trucks over 14,000 lbs GVWR operating in California to pass a biennial (every two years) smoke opacity test. The test measures visible exhaust smoke during acceleration; excessive opacity indicates a poorly maintained or malfunctioning diesel engine.
All vehicles subject to Clean Truck Check must be registered in TRUCRS. Inspection results are logged against the vehicle's record. Out-of-state trucks are not exempt — if your vehicle operates in California, it must be enrolled in TRUCRS and inspected on the two-year cycle.
The CARB Drayage Truck Regulation applies to trucks that haul cargo to or from California seaports and intermodal railyards. Drayage trucks must be registered in the CARB TRUCRS system and meet zero-emission vehicle (ZEV) requirements on a phased timeline.
New drayage truck registrations must be zero-emission
All new drayage registrations at CA ports/railyards must be ZEV
All drayage trucks operating at CA ports and railyards must be zero-emission
Note: CARB regularly updates drayage timelines and phase-out schedules. Verify current requirements at CARB.ca.gov before routing loads to California ports.
The Advanced Clean Trucks regulation applies to truck manufacturers, not fleet operators. It requires manufacturers selling Class 2b–8 trucks in California to meet increasing percentages of zero-emission vehicle (ZEV) sales from 2024 through 2035.
For fleet operators, the practical effect is that the mix of available new trucks from CARB-regulated manufacturers will shift toward ZEVs over time. If you are purchasing new heavy-duty trucks for California operations, check manufacturer ZEV availability and CARB certification status before ordering.
The Heavy-Duty Vehicle Inspection Program (HDVIP) is CARB's roadside enforcement mechanism. Inspectors operate at California weigh stations and CHP checkpoints and can pull any commercial truck for a CARB compliance check.
During an HDVIP inspection, officers check for:
Trucks found out of compliance may receive a Notice to Correct, be placed out of service, or have the operator cited. Carrying printed TRUCRS registration documentation in the cab is strongly recommended.
Off-road diesel equipment — including construction, agricultural, and industrial vehicles — is governed by a separate CARB program from the on-road truck rules described on this page. If you operate off-road diesel equipment in California (excavators, generators, forklifts, harvest equipment), compliance is tracked through CARB's DOORS (Diesel Off-Road Online Reporting System). Requirements vary by fleet size and horsepower tier. Consult the CARB In-Use Off-Road Diesel program at CARB.ca.gov for current compliance schedules.
Yes. CARB regulations apply to all heavy-duty diesel vehicles operating in California, regardless of where they are registered. Out-of-state trucks must register in TRUCRS and pass the biennial Clean Truck Check inspection before operating in California.
Clean Truck Check (formerly Periodic Smoke Inspection Program) requires biennial opacity (visible smoke) testing for diesel trucks over 14,000 lbs GVWR operating in California. Vehicles must be registered in CARB's TRUCRS system and pass the smoke test every two years. Fines for non-compliance can reach $1,000 per day per vehicle.
The Drayage Truck Rule regulates diesel trucks that move cargo to and from California's ports and intermodal railyards. As of 2023, new drayage truck registrations must be zero-emission. By 2035, all trucks operating at California ports and railyards must be zero-emission. Existing older-model drayage trucks have phase-out timelines based on engine year.
TRUCRS (Truck, Bus, and Off-Road Clean Air Reporting System) is CARB's online system for registering vehicles, reporting mileage, and tracking compliance with California's heavy-duty vehicle programs. All trucks operating in California over 14,000 lbs GVWR must be registered in TRUCRS and kept current.
If your truck fails the Clean Truck Check smoke opacity test or is found non-compliant during an HDVIP roadside inspection, you may receive a Notice to Correct and be required to repair the vehicle before operating in California again. Daily fines of up to $1,000 per vehicle apply for operating a non-compliant truck in California.
Disclaimer
The information on this page is compiled from publicly available government sources and is provided for general informational purposes only. TruckRadar is an independent search engine — we are not affiliated with any government agency and this content does not constitute legal or compliance advice. Regulations change frequently; always verify current requirements directly with the official source before making compliance decisions.
Official source: CARB.ca.gov — Truck & Bus RegulationLast reviewed: 2026-01