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By: @Brittney Barsotti

On June 1, the California Air Resources Board (CARB) published a second 15-Day Comment Period set of amendments to their Advanced Clean Fleets (ACF) regulations mandating state and local governments transition medium-duty and heavy-duty vehicle fleets to zero-emission vehicles (ZEV). The deadline for this new round of public comment is June 16, 2026.

Access Sample Comment Letter at:

csda.net/ZEV-Flexibility

CARB’s latest action follows its previous ACF regulation 15-Day Comment Period that closed on April 17. Those amendments adjusted certain exemptions, allowed local governments to switch between “milestone” and “purchase” paths to compliance, and added any franchises to the regulations.

This most recent round of amendments is intended by CARB to clarify throughout several corresponding sections that vehicles under contract with a state or local government are considered part of the fleet for compliance with the ACF regulations. These amendments still do not address CSDA’s call for flexibility and requested categorical exemption for vehicles that support emergency response.

CSDA plans to provide comment in connection with the latest 15-Day Comment Period, urging CARB to provide greater flexibility and exclude vehicles that support emergency services, consistent with our coalitions’ request in the public comment period that ended April 17.

Shortly following the release of this draft for public comment, CARB also issued a “guidance” to the ACF regulations.

According to the newly released CARB guidance materials, the proposed ACF amendments are designed to: 

• Improve compliance flexibility for public fleets;
• Repeal the High Priority Fleets and Drayage portions to provide greater regulatory certainty for private fleets; and,
• Clarify responsibilities related to vehicles under contract.

On its updated guidance webpage, CARB highlights the “Key Updates” in this second 15-Day Comment Period draft:

• Public agencies must report vehicles under contract in their fleets when determining compliance with the ACF regulation. 
• Private fleets are not subject to the ACF state and local government regulations. 
• The regulation applies to public services performed by a state and local government agency, including functions carried out through contractual arrangements.

CARB’s proposed amendments explicitly apply the ACF regulations to any vehicles that a state or local government “owns, leases, rents, operates, or contracts for the operation of,” that are not specifically excluded in the definitions section 2013(c). Purchases are now defined as, “add a vehicle to the California fleet.” Note that “California fleet” means the subset of vehicles in the total fleet operated in California by a fleet owner during a calendar year.

Additionally, CARB’s proposed amendments provide that local governments must submit documentation including “copies of any agreement contracting for vehicles or services using vehicles,” as a part of existing reporting requirements.

You can view CARB’s summary of the proposed changes here.

CSDA members can find extensive background information and resources, including sample social media posts and published editorials featuring CSDA members at csda.net/ZEV-Flexbility.