The California Air Resources Board (CARB) provides some additional clarity regarding the fate of three embattled mobile source fleet rules aimed at transitioning the state to zero-emission (ZE) technology.
Advanced Clean Fleets
On January 13, 2025, by
letter to U.S. EPA, CARB withdrew its requests for a waiver of preemption under the federal Clean Air Act (CAA) for its Advanced Clean Fleets (ACF) and In-Use Locomotives Rules. Under Section 209 of the CAA, CARB must obtain U.S. EPA approval prior to enforcing regulations that establish emission standards for on-highway vehicles, nonroad equipment, and locomotives. It is understood that CARB”s waiver requests were withdrawn in order to avoid imminent refusals under the incoming Trump Administration, which would have established precedent hindering future attempts to adopt and enforce ZE rules.
However, the text of the unenforceable rules remained part of the California Code of Regulations (CCR), and additionally, both rules were the subject of litigation in both State and Federal courts. Specifically, a group of 17 states, led by Nebraska, challenged the ACF rule in the U.S. District Court. Several industry groups also filed cases in State and Federal courts.
On May 25, 2025, it was announced that CARB agreed to commence a formal rulemaking to repeal the portions of the ACF Rule affecting High Priority and Drayage Truck fleets by October 31, 2025, as part of a settlement to dismiss the pending litigation. However, CARB posted on its
ACF program webpage that “[N]ot all elements of the ACF Regulation require a federal waiver or authorization. The state and local government fleets portion of the ACF Regulation remains unaffected.” It is unclear what legal rationale CARB is applying to reach this conclusion.
While some uncertainty remains, it is clear that California will need to “go back to the drawing board” if it wants to mandate ZE technology for drayage trucks and private fleets. Likewise, other western states such as Oregon, Washington, Colorado, and New Mexico will almost certainly pause their ambitions of adopting California’s ACF Rule.
In-Use Locomotives
Following its request to U.S. EPA to withdraw its waiver request for the In-Use Locomotive regulation, CARB agreed to formally repeal the measure. CARB was likewise facing imminent waiver refusal and legal challenges by the Association of American Railroads (AAR) and the American Short Line and Regional Railroad Association (ASLRA). CARB has now initiated the
repeal rulemaking with a scheduled hearing date of June 26, 2025. Given the current regulatory environment, it is not likely that California will attempt to adopt and enforce regulations establishing locomotive emission standards in the near future.
Zero-Emission Forklifts
CARB adopted its Zero Emission Forklifts Rule in June 2024. The rule sought to ban new purchases of propane and gasoline fueled forklifts with lift capacities 12,000 pounds or less. Additionally, the rule seeks to phase out in-use forklifts of the same size, based on a model year phase-out schedule. When CARB adopted the rule, the position stated in their
Final Statement of Reasons was that:
The Regulation does not set new emissions standards for any equipment preempted from state regulation under the CAA. In fact, the Regulation specifically excludes from its definition of LSI Forklifts those forklifts that fall under the CAA section 209(e) referenced by the Commenters. Commenters, furthermore, have not provided any evidence or examples of how this Regulation would impermissibly regulate diesel forklifts that would qualify as being under 175 horsepower and used only in construction or agriculture, as those terms are used in the federal CAA, section 209(e)
The rule was challenged in State court by an industry association, resulting in CARB backtracking on its position and agreeing not to enforce the rule unless and until a waiver is granted by U.S. EPA. CARB’s current position is stated within their
Zero Emission Forklifts Advisory, issued on May 29, 2025. Therein, it is admitted that “CARB has not yet sought authorization from the U.S. Environmental Protection Agency (U.S. EPA) for the ZEF regulation pursuant to section 209(e)(2)(A) of the Clean Air Act.” This represents a retreat and acknowledgement that a U.S. EPA waiver is indeed necessary for the rule.
