California Air Resources Board

Diesel Regulations

(Jump to Zero-Emission Regulations)

Truck & Bus

Diesel trucks and buses with a gross vehicle weight rating(GVWR) that are greater than 14,000 pounds (lbs), must reduce exhaust emissions by meeting particulate matter (PM) filter requirements and upgrading to a 2010 or newer engine model year (EMY).

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Transport Refrigeration Unit (TRU)

On February 24, 2022, CARB approved amendments to the TRU ATCM (2022 Amendments) to achieve additional emission and health risk reductions from diesel-powered TRUs and increase the use of zero‑emission technology in the off-road sector. 

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Tractor-Trailer GHG

Owners of 53-foot or longer box-type trailers including both dry-van and refrigerated-van trailers, and owners of the heavy-duty tractors that pull them on California highways must meet specific requirements.

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Off-Road

Learn about multiple diesel regulations pertaining to off-road vehicles and equipment.

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Solid Waste

The Solid Waste Collection Vehicle (SWCV) regulation was adopted by the Board in 2004. All SWCVs, except for certain low-use vehicles, were required to have particulate matter (PM) filters installed by December 31, 2010. In January 2019, the Board approved amendments to the SWCV regulation. 

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Clean Truck Check (HD I/M)

In December of 2021, CARB approved for adoption the HD I/M program in an ongoing effort to meet air quality standards by ensuring heavy-duty vehicle emissions control systems are properly operating throughout the life of the vehicle. The program sets regular testing requirements for all non-gasoline heavy-duty trucks operating in the State and will be tied to DMV registration.

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Zero-Emission Vehicle Regulations

In recent years CARB has begun developing and adopting zero-emission vehicle (ZEV) regulations.

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Portable Equipment Registration Program (PERP)

Owners or Operators of portable engines and other types of equipment can register their units under the CARB Statewide Portable Equipment Registration Program (PERP) in order to operate their equipment throughout California without having to obtain individual permits from local air districts. 

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Cargo Handling Equipment

Mobile cargo handling equipment is any motorized vehicle used to handle cargo or perform routine maintenance activities at California’s ports and intermodal rail yards. The type of equipment includes yard trucks (hostlers), rubber-tired gantry cranes, container handlers, forklifts, etc. 

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Zero-Emission Regulations

To view a calendar of important deadlines pertaining to the Drayage, Advanced Clean Fleets (ACF), Clean Truck Check, Transport Refrigeration Unit (TRU), Zero-Emission Airport Shuttle, and Innovative Clean Transit (ICT) regulations, view our Regulatory Deadlines Calendar page.

When developing new or amending existing regulations, CARB’s goal is to obtain emission reductions to meet federal air quality standards, minimize negative health effects in the State’s most impacted and disadvantaged communities, and to lessen climate impacts.

CARB collaborates closely with stakeholders to ensure regulations are technologically feasible and cost-effective. These regulations can require manufacturers to develop and commercialize zero-emission technologies as well as increase or accelerate user adoption of those technologies. CARB also sets certification standards through new engine and vehicle emission control regulations. The development of zero-emission certification standards are critical for the widespread deployment of zero-emission technologies through regulations and incentive programs. Below are some of the regulations that CARB currently has in place or under development to accelerate the deployment and adoption of zero-emission technologies in on-road applications:

Innovative Clean Transit Regulation

• Requires cleanest available technology for transit buses
• Beginning 2026, 50% of large and 25% of small transit agency new bus purchases must be zero-emission buses
• Beginning 2029, 100% of transit agency new bus purchases must be zero-emission buses
• The goal is to transition to a 100% zero-emission bus fleet by 2040

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Zero-Emission Airport Shuttle Regulation

• Requires cleanest available technology for airport ground transportation 
• By end of 2027, airport shuttle fleets must have 33% of shuttles be zero-emission
• By end of 2035, 100% of airport shuttles must be zero-emission

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Advanced Clean Trucks Regulation

• Requires manufacturers who certify Class 2b-8 chassis or complete vehicles with combustion engines to sell zero-emission trucks as an increasing percentage of their annual California sales
• By 2035, zero-emission truck/chassis sales must be 55% of class 2b to class 3 truck sales, 75% of class 4 to class 8 straight truck sales, and 40% of truck tractor sales

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Advanced Clean Fleets (ACF) Regulation

• The California Air Resources Board (CARB or Board) adopted the Advanced Clean Fleets regulation in April 2023. The Office of Administrative Law (OAL) has not yet approved the regulation; however, this web page provides information as adopted by the Board and that would go into effect when approved by OAL. 

• Sets world-first end to combustion engine sales for medium- and heavy-duty vehicles in California with a 100% zero-emission vehicle (ZEV) sales requirement on truck manufacturers starting in 2036. 

• Initial requirements focus on drayage trucks at the ports, state and local government fleets, and high priority fleets with vehicles that are suitable for electrification, their subhaulers, and entities that hire them. 

ACF Regulation Homepage
ACF Regulation Fact Sheets
Helpful Videos

ACF: Drayage

• Applies to Class 7-8 on-road trucks operating at California's seaports and intermodal railyards
• Legacy trucks may operate until the end of their useful life cycle
• Must visit a regulated seaport or railyard at least once a year
• May use limited extensions

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ACF: High Priority and Federal Fleets

Applies to:

• Fleets with 50+ vehicles, including common ownership and control
• Fleets with greater than $50 million in revenue
• Federal government fleets
• Entities that hire or dispatch fleets

Affected Vehicles:

• Class 2b-8 on-road vehicles
• Off-road yard tractors
• Light-duty package delivery vehicles

Two Compliance Paths, with flexibility to add new or used ICE vehicles meeting cleanest engine requirements:

• Model year schedule
  • Legacy trucks may operate until the end of their useful life*.
  • May use certain exemptions and extensions
  • ICE vehicle removals begin January 2025
  • Flexibility to add new or used ICE vehicles meeting cleanest engine requirements when granted exemptions to purchase ICE vehicles

• ZEV milestones option
  • Open to High Priority and State and Local Government fleets
  • Must meet ZEV milestones as a percentage of the total California fleet
  • Flexibility to add new or used ICE vehicles meeting cleanest engine requirements

*Useful life for high priority fleets is a maximum 18 years of age or those with more than 800,000 miles and are at least 13 years old. For California fleets, all additions must be ZEVs and legacy trucks must be removed after the end of their useful life. See model year schedule example chart.

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ACF: State & Local Government

• Agencies in designated counties and divisions with 10 or fewer trucks are exempt until 2027
• May use exemptions and extensions

Two compliance paths with flexibility to add new or used ICE vehicles meeting cleanest engine requirements:

• Default option is a zero-emission purchase requirement that aligns with public fleet purchasing cycles. Starting in 2024, 50% of purchases must be zero-emission. Starting 2027, all purchases must be zero-emission.

• May use Optional ZEV milestone phase-in
  • Open to High Priority and State and Local Government fleets
  • Must meet ZEV milestones as a percent of total fleet

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Zero-Emission Powertrain Certification Regulation

• Sets a zero-emission powertrain standard and certification process that will help reduce variability in the quality and increase reliability of heavy-duty electric and fuel cell vehicles
• Ensures vehicle and powertrain information are effectively and consistently communicated to purchasers
• Accelerates progress towards greater vehicle reparability
• Certification process required by Zero-Emission Airport Shuttle Regulation starting in model year 2026 and the Advanced Clean Trucks Regulation starting in model year 2024

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Zero-Emission Transport Refrigeration Unit (TRU) Regulation

• As of October 1, 2022, the effective date of the 2022 Amendments, truck TRUs are no longer subject to the in-use performance standards and are required to meet a zero-emission fleet requirement.
• TRU owners are required to turnover at least 15 percent of their truck TRU fleet (defined as truck TRUs operating in California) to zero-emission technology by December 31, 2023, and each year thereafter for seven years.
• Model year 2014 and older truck TRU engines were required to comply with ultra-low emission TRU in-use performance standard on or before December 31, 2021, prior to the October 1, 2022, effective date of the 2022 Amendments. Therefore, model year 2014 and older truck TRU engines that do not meet the ultra-low emission TRU in-use performance standard (have a Level 3 filter or use a qualifying Alternative Technology) can be cited for non-compliance if they operate in California.

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