California Air Resources Board

California Air Resources Board (CARB) staff worked jointly with the U.S. Environmental Protection Agency (EPA) and the National Highway Traffic Safety Administration (NHTSA) on the next phase of federal greenhouse gas (GHG) emission standards for medium- and heavy-duty engines and vehicles. These federal Phase 2 standards were built on the improvements in engine and vehicle efficiency required by the Phase 1 emission standards and represent a significant opportunity to achieve further GHG reductions for 2018 (2020 in California) and later model year heavy-duty vehicles, including trailers.

In the California Phase 2 standards, California aligned with the federal Phase 2 standards in structure, timing, and stringency, but with some minor California differences.

Meetings and Workshops

Rulemaking Documents

2021

• Heavy-Duty Omnibus Regulation and Associated Amendments

2018

• Phase 2 and Tractor-Trailer Amendments Regulation

• Background Materials 

CARB Comments on Proposed Federal Rule

• Comments on the U.S. EPA and NHTSA's Phase 2 Notice of Proposed Rulemaking and Regulatory Impact Analysis (Greenhouse Gas Emissions and Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles)
• Comments on NHTSA's Phase 2 Fuel Efficiency Standards for Medium- and Heavy-Duty Engines and Vehicles: Draft Environmental Impact Statement.

Additional Resources

CARB's Draft Technology Assessment: Engine/Powerplant and Drivetrain Optimization and Vehicle Efficiency has been released.  The draft assessment evaluates the potential of various technologies to improve heavy-duty truck fuel efficiency.  These same technologies were evaluated by U.S. EPA and NHTSA as part of the federal Phase 2 regulatory development process.  This report can be accessed at the Technology and Fuels Assessment Reports webpage.