CARB ACF Regulation: 2025 Changes, Compliance Pathways & Penalties

The CARB Advanced Clean Fleets regulation still applies to California state and local government fleets, which must buy only zero-emission vehicles starting January 1, 2027, but its two biggest private-sector pieces — the high-priority fleet rules and the drayage truck rules — are no longer being enforced after CARB withdrew its federal Clean Air Act waiver request in January 2025 and settled a multi-state lawsuit in May 2025. If you run a government fleet, your obligations are intact. If you run a private high-priority or drayage fleet, the mandates are paused and CARB has committed to repealing them.

What Changed in 2025

CARB formally withdrew its waiver and authorization request to the U.S. Environmental Protection Agency on January 13, 2025, which pulled out from under ACF the federal preemption authority its private-fleet provisions required.¹ That alone halted enforcement of the high-priority fleet and drayage truck requirements.

Four months later, CARB settled a lawsuit brought by a coalition of 17 states led by Nebraska along with trucking industry groups. Under the settlement, California agreed not to enforce the high-priority fleet and drayage provisions and committed to opening formal rulemaking to repeal those portions of the regulation.² CARB also acknowledged it cannot enforce the planned 2036 ban on new internal-combustion truck sales without an EPA waiver. A rulemaking hearing was scheduled for September 25, 2025.³

What survived untouched: the state and local government fleet requirements. Those obligations never depended on an EPA waiver, so neither the withdrawal nor the settlement reached them.

Government Fleet Requirements Still in Force

City, county, and state agencies that operate vehicles with a gross vehicle weight rating above 8,500 pounds are covered. Since January 1, 2024, at least 50 percent of the agency’s annual vehicle purchases have had to be zero-emission. On January 1, 2027, that figure jumps to 100 percent of new vehicle purchases. Government fleet managers must submit annual reports through CARB’s TRUCRS system by April 1 each year, running through 2045.⁴

Agencies that paused ZEV procurement expecting the whole regulation to unravel should reset: CARB retains full enforcement authority here, and the 2027 cliff is close.

High-Priority Fleet and Drayage Rules (Enforcement Suspended)

Before enforcement stopped, ACF defined a “high-priority fleet” as any entity with $50 million or more in gross annual revenue, or one owning and operating 50 or more vehicles. Coverage extended to vehicles over 8,500 pounds GVWR plus light-duty package delivery vehicles and yard tractors.⁵

Drayage trucks serving California seaports and railyards had their own track. Internal-combustion drayage trucks had to be registered in TRUCRS by December 31, 2023, and could continue operating only until reaching their minimum useful life, defined as the later of 13 years from the engine’s certified model year, or whichever comes first of 800,000 miles or 18 years old.⁶

None of this is being enforced in 2026. Private fleets in these categories should still watch the rulemaking docket, because a renewed waiver request or a new regulation could put similar obligations back on the table.

The Two Compliance Pathways

ACF offers covered fleets two ways to phase in zero-emission vehicles. Government fleets still operate under this framework, and private fleets need to understand it in case any version of it returns.

Model Year Schedule

Every newly added vehicle must be zero-emission. Existing internal-combustion vehicles can stay in service until the end of their useful life — generally 13 to 18 years from the engine’s certified model year, with an 800,000-mile cap — and then must be retired and replaced with a ZEV.⁶ This path demands careful tracking of model year and mileage on every vehicle.

ZEV Milestones Option

The milestones path lets fleet owners keep individual older vehicles running longer as long as the overall fleet hits ZEV percentage targets on time. CARB sorts vehicles into three groups with staggered schedules:⁷

Group 1 covers box trucks, vans, two-axle buses, yard tractors, and light-duty package delivery vehicles. Target: 10 percent ZEV by 2025, rising to 100 percent by 2035.
Group 2 covers work trucks, day cab tractors, pickup trucks, and three-axle buses. Target: 10 percent ZEV by 2027, rising to 100 percent by 2039.
Group 3 covers sleeper cab tractors and specialty vehicles. Target: 10 percent ZEV by 2030, rising to 100 percent by 2042.

The milestones route helps when some vehicle types still lack mature ZEV options. A fleet might front-load ZEV purchases in box trucks and vans while keeping long-haul sleepers on diesel until the technology and charging infrastructure catch up.

Exemptions and Extensions

For fleets still subject to ACF, the regulation includes several safety valves, grounded in 13 CCR § 2015.1 and § 2015.3.⁸

Backup vehicle exemption. A used internal-combustion vehicle designated as a backup in TRUCRS and driven fewer than 1,000 miles per year can be excluded from ZEV requirements. The designation must be renewed annually, and miles driven during a declared emergency don’t count against the cap.⁹
Daily usage exemption. If available ZEVs can’t meet a vehicle’s daily operational needs, the fleet owner can apply to buy a new internal-combustion vehicle instead. At least 10 percent of the fleet must already be ZEV to qualify.
ZEV purchase exemption. When no zero-emission vehicle is available in the configuration a fleet needs, the owner can request permission to purchase a conventional vehicle.
Infrastructure delay extension. Fleets that have ordered charging or fueling equipment but face construction delays outside their control, such as utility interconnection backlogs or long transformer lead times, can apply for additional time. Supporting documentation includes an executed ZEV purchase agreement, utility applications, and construction permits.¹⁰
Vehicle delivery delay extension. When a ZEV has been ordered but the manufacturer can’t deliver on time, the compliance deadline on the internal-combustion vehicle it is replacing can be extended.
Emergency and mutual aid exemptions. Vehicles dispatched to support declared emergencies can be excluded from fleet calculations. Fleets with mutual aid agreements can request to exclude up to 25 percent of their vehicles from ZEV requirements once at least 25 percent of the fleet is already zero-emission.
Snow removal exemption. Until January 1, 2030, vehicles equipped with snowplow or snow blower attachments can be excluded from compliance calculations. Dedicated snow removal vehicles are excluded from the regulation entirely.

All extension applications must be renewed each year with updated documentation showing active progress toward compliance. Extensions buy time; they don’t erase the underlying obligation.

Reporting Through TRUCRS

Covered fleets report through CARB’s Truck Regulation Upload, Compliance, and Reporting System, which was updated in 2024 to handle ACF data. For each vehicle, the fleet reports the VIN, gross vehicle weight rating, fuel type, body style, odometer reading, engine family number, and the primary garaging or dispatch location.¹¹ The engine family number appears on the vehicle’s emission control information label, usually under the hood.¹²

Government fleets must submit annual TRUCRS reports by April 1 each year.⁴ Once TRUCRS confirms a fleet meets current requirements, it generates a compliance certificate authorizing the fleet to operate on California roads for the coming year. Keep purchase receipts, lease agreements, registration documents, and odometer logs on hand; any mismatch between reported data and actual records can trigger enforcement.

Penalties

Air quality violations under the Health and Safety Code reach ACF. A basic violation can bring a fine of up to $1,000, imprisonment of up to six months, or both. Negligent violations can run to $25,000, and knowing violations, where the operator was aware of the problem and failed to correct it, can reach $40,000. Separate provisions allow civil penalties of up to $37,500 per vehicle for selling noncompliant vehicles in California, and these amounts are subject to inflation adjustments.¹³

In practice, enforcement against high-priority and drayage fleets is suspended under the 2025 settlement. Government fleet operators remain fully exposed to this penalty framework for missed ZEV purchase requirements or reporting deadlines.

Federal Tax Credit for Charging Infrastructure

Fleets investing in charging or hydrogen fueling equipment can offset some cost through the federal Alternative Fuel Vehicle Refueling Property Credit under Internal Revenue Code Section 30C. The base credit equals 6 percent of the cost of each qualified item, including installation labor. Businesses meeting prevailing wage and apprenticeship requirements qualify for a 30-percent credit instead. Either way, the credit caps at $100,000 per item, with each charging port or fuel dispenser counting separately.¹⁴

The spread between 6 percent and 30 percent is large on heavy-duty charging equipment, which can run well into six figures per unit. Prevailing wage and apprenticeship compliance adds to labor cost, but the five-fold jump in credit rate more than covers it on most projects.

One federal incentive is gone: the Section 45W clean commercial vehicle credit, which had provided tax credits for buying zero-emission trucks and buses, was terminated effective September 30, 2025 by the One Big Beautiful Bill Act.¹⁵ Fleets that had counted on 45W to narrow the price gap between electric and diesel trucks will need to look elsewhere for purchase incentives, such as California’s Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project (HVIP).

1
U.S. Environmental Protection Agency. Withdrawal of California’s Request for a Waiver Pursuant to Clean Air Act Section 209(b)
2
Nebraska Attorney General. ACF Settlement Press Release
3
California Air Resources Board. Advanced Clean Fleets and Low Carbon Fuel Standard Regulations
4
California Air Resources Board. Advanced Clean Fleets Regulation – State and Local Government Agency Fleet Requirements Overview
5
Cornell Law School. California Code of Regulations Title 13 2015 – High Priority and Federal Fleets Applicability, Definitions, and General Requirements
6
California Air Resources Board. Advanced Clean Fleets Regulation Drayage Truck Requirements – Minimum Useful Life
7
California Air Resources Board. Advanced Clean Fleets Regulation – ZEV Milestones Option
8
Cornell Law School. California Code of Regulations Title 13 2015.1 – High Priority and Federal Fleet ZEV Requirements
9
California Air Resources Board. Advanced Clean Fleets Regulation Exemptions and Extensions Overview
10
California Air Resources Board. Advanced Clean Fleets Regulation – Zero-Emission Vehicle Infrastructure Delay Extension
11
California Air Resources Board. Truck Regulation Upload, Compliance and Reporting System Q&A
12
U.S. Environmental Protection Agency. Information About Family Naming Conventions for Vehicles and Engines
13
Justia. California Health and Safety Code 42400-42410 – Penalties
14
Internal Revenue Service. Alternative Fuel Vehicle Refueling Property Credit for Businesses
15
Inflation Reduction Act Tracker. Clean Commercial Vehicle Credit