CARB's Advanced Clean Fleets Rule Keeps Shifting: Where Things Stand for San Diego Operators in 2026

If you've given up trying to keep track of California's Advanced Clean Fleets (ACF) regulation, you're not alone, 2026 alone has brought amendments, a partial repeal, and a state-law challenge to how far CARB can actually reach. Here's where things stand, in plain language, as of this summer.

The basics

ACF is the California Air Resources Board's regulation pushing state and local government fleets, and, depending on how the rule is interpreted, certain private contractors working with them, toward zero-emission medium- and heavy-duty vehicles by 2030. It's part of a broader package of clean-vehicle rules that includes the separate Advanced Clean Trucks regulation.

What changed this year

On September 25, 2025, CARB voted to repeal the ACF's Drayage and High-Priority Fleets requirements entirely, citing confusion and uncertainty around how those provisions would be enforced. That repeal is set to take effect January 1, 2027. Then, on June 1, 2026, CARB released a second round of 15-day modifications to the broader rule, with the public comment period closing June 16, 2026, and key industry concerns still unresolved going into the back half of the year.

The private contractor question is still unsettled

One of the most consequential open issues: CARB staff have maintained that private companies operating under contract for state or local government entities count as part of that government fleet, and are therefore subject to ACF requirements, even though they're privately owned businesses. But California's AB 1436 was recently amended specifically to clarify that CARB cannot regulate private contract fleets, directly or indirectly, without first securing a federal preemption waiver under the Clean Air Act. In other words: state law and CARB's own rulemaking are currently pointing in different directions, and it isn't fully resolved.

What this means if you lease your equipment

We're not going to tell you how ACF applies to your specific fleet, that's a conversation for your compliance counsel or fleet advisor, especially while the rule is still being litigated and amended. What we can say is this: in a regulatory environment that's changing every few months, locking capital into aging owned equipment carries real risk if the rules shift again before that equipment is fully depreciated. Leasing gives you room to adjust as the picture clarifies, rather than betting on which way a still-unsettled rule will land.

If you want to talk through how a flexible trailer lease fits into your planning while ACF plays out, reach out, we follow this closely because our clients ask us about it constantly.