The California Air Resources Board has tweaked its certification standards for its Advanced Clean Truck and Zero-Emission Powertrain Certification, giving manufacturers more flexibility. 

Although Congress passed resolutions revoking the EPA waivers for these rules, the Clean Truck Partnership means truck makers are still obligated to follow the regulations.

In a July 24 email announcement, CARB said it approved amendments that support commitments made in the Clean Truck Partnership, an agreement with the nation’s leading major truck manufacturers to reduce emissions from the trucking industry.

The Clean Truck Partnership is under fire by the Western States Trucking Association, which alleges it's a de facto regulation that didn't go through proper state administrative procedures.

The amendments are minor changes with no significant cost or emissions impact, according to the agency, and were developed in response to stakeholder comments.

What Did CARB Change With Latest Clean Truck Certification Amendments?

Changes include:

• Adding a “pooling” option for manufacturers to transfer surplus zero-emission vehicle and near-zero emission vehicle credits generated between states that adopted the ACT regulation.

• Permitting manufacturers to offset a portion of deficits generated in the Class 7-8 tractor group with Class 2b-3 or Class 4-8 group ZEV credits for each model year, allowing manufacturers more flexibility and to account for fluctuations in ZEV and NZEV sales across states and vehicle classes. 

• Adjusting the minimum all-electric range requirement for NZEV in later years

• Giving manufacturers increased flexibility on the order in which they retire credits.

• Modifying the communication protocols of the ZEV connector criteria for certifying zero-emission powertrains.

“California’s commitment to cleaner trucks has created an ecosystem of programs and incentives that will continue to drive progress despite the federal administration’s unlawful actions challenging our state’s efforts to reduce emissions and deploy clean transportation technologies,” said CARB Chair Liane Randolph in the announcement.

Why CARB is Changing Clean Truck Rules

The Advanced Clean Trucks regulation was adopted by CARB in 2020, requiring truck manufacturers to transition from diesel trucks and vans to electric zero-emission trucks beginning in 2024. 

In 2023, CARB and truck and engine manufacturers announced the Clean Truck Partnership. Truck OEs committed to meeting CARB’s regulations in the state regardless of CARB’s overall authority to implement those regulations. This was in exchange for rule changes giving them more flexibility at the time.

On June 12, 2025, President Trump signed Congressional resolutions to overturn three of the U.S. Environmental Protection Agency’s previous decisions to grant California waivers, including its Advanced Clean Cars II, Advanced Clean Trucks, and Heavy-Duty Engine and Vehicle Omnibus regulations.

How Did California React to EPA Waiver Revocations?

California swiftly filed suit to challenge the resolutions as illegal and unconstitutional.

Following the President’s action, CARB released guidance for manufacturers subject to the regulations. The advisory explained that CARB would continue accepting and processing certification applications to ensure continuity and enable lawful vehicle sales in California.

That guidance said CARB would continue to accept and process certification applications and administer the Zero Emission Powertrain Certification Procedure as it existed on January 21, 2020, and the Standards and Test procedures incorporated in the Zero Emission Powertrain Certification Procedure as they existed on January 21, 2020.

The guidance also said CARB would continue to accept and process manufacturer sales reports for medium- and heavy-duty engines and vehicles under the requirements of the Advanced Clean Trucks regulations.

On the Heavy-Duty Engine and Vehicle Omnibus Regulation, CARB has issued Executive Orders of Certification for Omnibus-compliant engines sold in California and will continue to accept and process certification applications for model year 2025 and 2026 medium- and heavy-duty vehicles.

What’s Next in California-versus-DC?

Gov. Gavin Newsom signed an executive order on June 12 directing state agencies to assess additional actions to spur light-, medium-, and heavy-duty zero-emission vehicle adoption in California. Those recommendations are due to the governor in August.

“Despite the market uncertainty and disruption brought on by the federal government, California remains steadfast in its commitment to work with manufacturers to keep moving toward a cleaner transportation system while also reducing harmful and costly air pollution,” said CARB’s announcement.