Diesel trucks are not banned in California, but the state enforces the tightest diesel rules in the country and they apply to anyone driving a heavy diesel on California roads. The core requirement is straightforward: since January 1, 2023, nearly every diesel vehicle over 14,000 pounds operating in the state must run a 2010-model-year or newer engine.1California Air Resources Board. Truck and Bus Regulation On top of that, covered trucks have to be reported to the California Air Resources Board (CARB), pay an annual Clean Truck Check fee, and pass periodic emissions testing. Older engines are being pushed off the road, but a compliant diesel truck can still legally do business in California today.
What “Operating in California” Actually Means
The rules don’t care where your truck is registered. The Truck and Bus Regulation covers all diesel vehicles over 14,000 pounds operating in California, whether they’re based in the state or hauling in from somewhere else.1California Air Resources Board. Truck and Bus Regulation An interstate carrier running loads through California needs a 2010 or newer engine and needs to be reported through CARB’s system, same as a California-based fleet.
Clean Truck Check adds a parallel obligation. Non-gasoline heavy-duty vehicles over 14,000 pounds operating in California must register in the program, pay the annual compliance fee ($32.13 per vehicle for 2026), and pass emissions testing.2California Air Resources Board. Clean Truck Check Compliance Fee Update Effective 1/1/2026 Out-of-state operators sometimes learn about this at a roadside inspection.
Which Trucks Are Covered
The Truck and Bus Regulation is the backbone rule. It applies to most on-road diesel trucks and buses with a gross vehicle weight rating over 14,000 pounds, including privately owned rigs, federally owned vehicles, and school buses.1California Air Resources Board. Truck and Bus Regulation Diesel vehicles between 8,501 and 14,000 pounds generally sit below that threshold and don’t face the same Truck and Bus or Clean Truck Check requirements.3California Air Resources Board. New California Requirements for On-Road and Off-Road Heavy-Duty Vehicles
Separate regulations cover a few adjacent categories, each with its own compliance track:
- Drayage trucks serving California’s seaports and intermodal railyards.4Cornell Law School. Cal. Code Regs. Tit. 13, 2014.1
- Off-road diesel equipment rated at 25 horsepower or more, including bulldozers, forklifts, cranes, and excavators. Rented and leased machines count.5California Air Resources Board. In-Use Off-Road Diesel-Fueled Fleets Regulation Overview
- Transport Refrigeration Units (TRUs), the diesel-powered cooling systems on trucks, trailers, containers, and railcars.6California Air Resources Board. TRU Compliance Information
The 2010 Engine Floor
The single most important number for a diesel truck owner in California is the 2010 model year. Every diesel vehicle over 14,000 pounds operating in the state must have a 2010-model-year or newer engine and emissions system, with limited exceptions.1California Air Resources Board. Truck and Bus Regulation The 2010 line matters because that’s when EPA emissions standards took effect requiring diesel particulate filters and selective catalytic reduction systems.
If your truck has a pre-2010 engine and doesn’t qualify for an exemption, you have three practical options: repower with a 2010 or newer compliant engine, buy a newer truck, or stop operating in California.
How Compliance Works Day to Day
TRUCRS Reporting
CARB’s Truck Regulation Upload, Compliance, and Reporting System (TRUCRS) is the central database for reporting under several regulations, including the Truck and Bus Regulation and Advanced Clean Fleets.7California Air Resources Board. TRUCRS Reporting Information Trucks with 2010 or newer engines that aren’t using any flexibility options don’t have to report to TRUCRS for Truck and Bus purposes, though other regulations may still pull them in.8California Air Resources Board. TRUCRS Reporting Guide
Clean Truck Check Fee and Testing
Clean Truck Check is the heavy-duty counterpart to California’s passenger Smog Check. Covered vehicles have to be reported, pay the annual fee, and go through periodic emissions testing.9California Air Resources Board. Clean Truck Check Overview Fact Sheet The 2026 compliance fee is $32.13 per vehicle, adjusted annually for inflation.2California Air Resources Board. Clean Truck Check Compliance Fee Update Effective 1/1/2026
Emissions compliance testing became effective October 1, 2024, with the first deadlines on January 1, 2025, and semiannual testing kicking in that year.10California Air Resources Board. Clean Truck Check FAQ Qualifying agricultural vehicles test only once per year.11California Air Resources Board. Clean Truck Check Agricultural Vehicles Requirements
The test method depends on engine year. Trucks with 2013 or newer diesel engines are checked with an on-board diagnostics scan using a CARB-certified device. Older diesel engines get a smoke opacity test and a visual inspection of emissions controls.12California Air Resources Board. Clean Truck Check Emissions Compliance Testing Requirements Testing has to be done by a credentialed tester who has completed CARB’s training course and passed an exam with at least 80 percent.13California Air Resources Board. Clean Truck Check Tester Training Course
Exemptions Worth Knowing
Low-Use Vehicles
A truck that rarely runs in California may qualify for the permanent low-use exemption under the Truck and Bus Regulation. The vehicle has to average 200 or fewer hours of operation per year, or less than 600 hours across any rolling three-year period.14California Air Resources Board. Fact Sheet: Low-Use Requirements Exceed the 200-hour annual ceiling and you’re in violation. The older year-by-year low-use option ended on January 1, 2024.
Emergency Vehicles
Authorized emergency vehicles as defined by California Vehicle Code section 165, and vehicles carrying an emergency vehicle permit from the California Highway Patrol, are exempt from the Truck and Bus Regulation’s upgrade requirements. Vehicles dispatched by a government agency to support emergency operations under a governor’s executive order also qualify.15California Air Resources Board. Truck and Bus Emergency Use Miles Fact Sheet Routine work to prevent public health risks isn’t emergency use.
Agricultural Vehicles
CARB defines an agricultural vehicle narrowly. It must be owned or operated by a farming business, used exclusively in agricultural operations, and limited to transporting agricultural products to the first point of processing.11California Air Resources Board. Clean Truck Check Agricultural Vehicles Requirements Qualifying vehicles get the lighter, once-a-year emissions testing schedule under Clean Truck Check.
What Happens If You Don’t Comply
Enforcement combines DMV registration blocks, roadside inspections, and fleet audits. For many owners, the first sting is at the DMV: it will refuse to renew registration for a truck that isn’t compliant with the Truck and Bus Regulation. If your vehicle gets flagged, paying the registration fee buys you a 90-day temporary operating permit, and that’s the window to get right.16California Air Resources Board. CARB Warning on DMV Registration Renewal Notice
The statutory penalty ceiling is high. Under the California Health and Safety Code, violations of CARB regulations that don’t carry a separate penalty can draw fines up to $37,500 per action.17California Legislative Information. California Health and Safety Code 43016 Actual penalties vary. For the Periodic Smoke Inspection Program, failure-to-test penalties have ranged from $42 to $2,000 per violation. For off-road fleets that fail to report, minimums have run around $800 per violation, with statutory maximums reaching roughly $5,500 to $10,900 per violation per day.18California Air Resources Board. 2014-2024 Minimum and Maximum Penalties
Companies that hire or dispatch trucks carry risk too. CARB has pursued penalties against businesses that used non-compliant carriers without checking their status, and roadside inspections can pull a vehicle out of service on the spot.
Help Paying for Compliance
Upgrading a truck isn’t cheap, and CARB and related programs offer funding to soften the cost.
The Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project (HVIP) provides point-of-sale vouchers for zero-emission vehicle purchases. Owner-operators, small businesses, school districts, and municipal fleets can apply. Small fleets with 20 or fewer medium- and heavy-duty vehicles and annual revenue under $15 million qualify for increased voucher amounts.
The Innovative Small E-Fleet Pilot Program (ISEF) targets that same small-operator profile: 20 or fewer trucks and under $15 million in annual revenue, open to companies, nonprofits, public agencies, and independent owner-operators. Voucher amounts for zero-emission replacements range from $9,000 for a Class 2b vehicle up to $330,000 for a Class 8 truck and $420,000 for a Class 8 fuel cell vehicle. ISEF also supports alternative business models like all-inclusive leases and truck-sharing arrangements.19California Air Resources Board. Innovative Small E-Fleet Pilot Program
The Carl Moyer Memorial Air Quality Standards Attainment Program funds engine replacements and equipment upgrades through local air districts. For fiscal year 2025–2026, CARB allocated approximately $12.35 million in state reserve funds, directed toward zero-emission equipment and infrastructure projects.20California Air Resources Board. Carl Moyer Program State Reserve Solicitation Availability and applications go through local air districts and vary by region.
Deadlines Still Coming
The 2010 engine floor is already in force for on-road trucks. Off-road equipment is on a longer runway. The Off-Road Diesel Regulation eliminates older engine tiers between 2024 and 2036, with schedules based on fleet size.5California Air Resources Board. In-Use Off-Road Diesel-Fueled Fleets Regulation Overview
- 2026: large and medium fleets must retire Tier 1 engines and comparable on-road engines from before 1999.
- 2028: large fleets must retire Tier 2 engines and comparable on-road engines from before 2003; medium fleets phase out Tier 1.
- 2030 through 2036: remaining medium and small fleets phase out Tier 2 engines on a staggered schedule.
Off-road fleets have to update their inventory in CARB’s reporting system by March 1 each year.
Drayage rules are in a holding pattern. Under the regulation, only zero-emission drayage trucks have been eligible for new registration in CARB’s system since January 1, 2024, and all drayage trucks are supposed to be zero-emission by January 1, 2035.4Cornell Law School. Cal. Code Regs. Tit. 13, 2014.1 CARB has said it will not enforce the drayage registration prohibitions until the U.S. EPA grants a preemption waiver or determines one isn’t needed.21California Air Resources Board. Advanced Clean Fleets Regulation Enforcement Notice CARB withdrew its waiver request in January 2025, so enforcement remains paused indefinitely. Existing drayage trucks with 2010 or newer engines can keep running.