California’s Advanced Clean Fleets regulation requires covered medium- and heavy-duty fleet operators to phase combustion-engine trucks out and replace them with zero-emission vehicles on a mandatory schedule that began in 2024 and finishes, depending on vehicle type, between 2035 and 2042. The rule covers state and local government fleets, large private fleets, federal agencies operating in California, and drayage trucks at seaports and railyards. Private and federal fleets choose between two compliance paths, and several extensions are available for infrastructure delays, delivery delays, and vehicle types with no viable zero-emission option.
Who Has to Comply
The regulation sits in Title 13 of the California Code of Regulations and splits covered operators into four groups, each with its own section and its own timeline.
State and Local Government Fleets
Under 13 CCR § 2013, any California state or local agency that owns, leases, or operates a covered vehicle follows a purchase-based schedule. Since January 1, 2024, at least 50% of annual vehicle purchases have had to be zero-emission, and starting January 1, 2027, 100% of purchases must be zero-emission. Small government fleets of ten or fewer vehicles, and agencies in designated low-population counties, can wait until January 1, 2027 to begin, at which point the 100% purchase rule applies to them too.1California Air Resources Board. State and Local Government Agency Fleet Requirements Overview
High Priority Fleets
Section 2015 covers the largest private operators. You are a high priority fleet if your entity (including all subsidiaries and branches) reports $50 million or more in total gross annual revenue to the IRS, or if you own, operate, or direct 50 or more vehicles with a gross vehicle weight rating above 8,500 pounds. Fleets under common ownership or control are counted together toward that 50-vehicle threshold.2California Air Resources Board. California Code of Regulations Title 13 – High Priority and Federal Fleets Requirements
Federal Government Fleets
Federal agencies operating covered vehicles in California are pulled into § 2015 with the high priority private fleets, not the § 2013 state and local government rules.3Legal Information Institute. California Code of Regulations Title 13 Section 2013 – State and Local Government Fleet Applicability, Definitions, and General Requirements
Drayage Trucks
Drayage trucks at California seaports and intermodal railyards run on a faster and separate schedule under 13 CCR § 2014.1. Since January 1, 2024, any newly registered drayage truck must be zero-emission. Legacy combustion drayage trucks already registered can keep operating, but they must visit a California seaport or railyard at least once each calendar year to keep their registration, and they cannot exceed their minimum useful life. By January 1, 2035, every drayage truck operating in California must be zero-emission.4New York Codes, Rules and Regulations. California Code of Regulations Title 13 Section 2014.1 – In-Use On-Road Heavy-Duty Drayage Trucks
The Two Compliance Paths
If you run a high priority or federal fleet, you pick one of two ways to comply.
Model Year Schedule
The Model Year Schedule under 13 CCR § 2015.1 works as a one-for-one replacement rule. When an existing combustion vehicle hits the age and mileage thresholds that define its useful life, it comes out of the California fleet, and any replacement must be zero-emission. No new combustion trucks can be added to the fleet after the applicable compliance date.5New York Codes, Rules and Regulations. California Administrative Code Title 13 Section 2015.1 – High Priority and Federal Fleet Model Year Schedule
This path suits fleets that already turn vehicles over on a predictable cycle. You do not chase percentage targets across the whole fleet. You do, however, lose flexibility: when a vehicle hits its removal date, it goes.
ZEV Milestones Option
The ZEV Milestones Option under 13 CCR § 2015.2 sets fleet-wide percentage targets by calendar year, sorted by vehicle group.6Legal Information Institute. California Code of Regulations Title 13 Section 2015.2 – High Priority and Federal Fleets ZEV Milestones Option
The deadlines break out by vehicle group:
- Group 1 (box trucks, vans, two-axle buses, yard tractors, light-duty package delivery vehicles): 10% ZEV by 2025, 25% by 2028, 50% by 2031, 75% by 2033, 100% by 2035.
- Group 2 (work trucks, day cab tractors, pickup trucks, three-axle buses): 10% by 2027, 25% by 2030, 50% by 2033, 75% by 2036, 100% by 2039.
- Group 3 (sleeper cab tractors and specialty vehicles): 10% by 2030, 25% by 2033, 50% by 2036, 75% by 2039, 100% by 2042.
Each percentage must be held continuously until the next milestone. If your Group 1 vehicles hit 10% in 2025, they stay at or above 10% through the end of 2027, then move to 25% starting in 2028. Each milestone period requires recalculating your total California fleet size to figure out how many zero-emission units you need. Fleets with mixed vehicle types juggle overlapping deadlines across the three groups.
Extensions and Exemptions
Section 2015.3 provides several safety valves. Each requires documentation and CARB approval.7Legal Information Institute. California Code of Regulations Title 13 Section 2015.3 – High Priority and Federal Fleets Exemptions and Extensions
ZEV Infrastructure Delay Extension
If you started a charging or hydrogen fueling infrastructure project at least one year before your compliance date and construction or utility connection did not finish in time, you can request an extension to keep existing vehicles in service while the project wraps up. CARB can grant up to two years for a construction delay and up to five years for a site electrification delay, depending on the documentation showing the delay was outside your control.8California Air Resources Board. Advanced Clean Fleets Regulation Exemptions and Extensions Overview
Vehicle Delivery Delay Extension
If you ordered a zero-emission vehicle and the manufacturer cannot deliver on time, this extension keeps the existing combustion vehicle in the fleet while the order is pending. You need manufacturer documentation showing the order date and expected delivery.5New York Codes, Rules and Regulations. California Administrative Code Title 13 Section 2015.1 – High Priority and Federal Fleet Model Year Schedule
Daily Usage Exemption
If no battery-electric vehicle on the market can match the demonstrated daily range, payload, or duty cycle of a vehicle in your fleet, you can request an exemption to buy a new combustion vehicle in the same configuration. This is a technical showing based on your actual operating data, not a general argument that electric trucks do not fit your industry.7Legal Information Institute. California Code of Regulations Title 13 Section 2015.3 – High Priority and Federal Fleets Exemptions and Extensions
ZEV Purchase Exemption
Fleets on the Model Year Schedule can use a purchase exemption when no zero-emission vehicle in the needed configuration is available for sale. The request must be filed no later than one year before the compliance date, and no earlier than when the existing combustion vehicle reaches 16 years old or 700,000 miles, whichever comes first. If granted, you can buy a new combustion replacement, and the old vehicle’s removal deadline is extended until the new one arrives.5New York Codes, Rules and Regulations. California Administrative Code Title 13 Section 2015.1 – High Priority and Federal Fleet Model Year Schedule
Where Enforcement Stands
California needs a preemption waiver from the EPA under Section 209 of the federal Clean Air Act before it can fully enforce the high priority fleet requirements. As of early 2026, that waiver has not been granted.
CARB has said it will not seek monetary penalties against fleet owners for potential violations of the high priority fleet requirements between January 1, 2024, and 90 days after the EPA takes final action on the waiver request. But CARB has reserved the right to enforce retroactively once the waiver comes through. Vehicles added to a fleet after January 1, 2024, that do not meet ACF requirements may need to be removed, or the fleet may be required to switch onto the ZEV Milestones Option.9California Air Resources Board. Advanced Clean Fleets Enforcement Notice
In February 2026 the EPA rescinded the 2009 Greenhouse Gas Endangerment Finding and repealed federal GHG emission standards for highway vehicles.10U.S. Environmental Protection Agency. Final Rule – Rescission of the Greenhouse Gas Endangerment Finding and Motor Vehicle Greenhouse Gas Emission Standards Under the Clean Air Act How that affects California’s pending waiver request is unclear. The ACF regulation rests on California’s independent Clean Air Act authority over criteria pollutants rather than on federal GHG rules, and CARB has warned it will enforce retroactively once the waiver clears. The practical takeaway is that compliance planning should proceed as if the deadlines are firm.
Penalties
Once the waiver is granted and the grace period ends, violations carry strict liability of up to $1,000 per day for each day the violation continues under the California Health and Safety Code. For violations tied to federal Clean Air Act delegation authority, the ceiling rises to $10,000 per day.11California Legislative Information. California Health and Safety Code HSC Section 39674
Drayage enforcement is more direct. A non-compliant drayage truck is removed from the CARB Online System, which means it can no longer legally operate at California seaports or intermodal railyards. That is an operational shutdown, not just a fine.4New York Codes, Rules and Regulations. California Code of Regulations Title 13 Section 2014.1 – In-Use On-Road Heavy-Duty Drayage Trucks
Reporting Through TRUCRS
Compliance reporting runs through CARB’s Truck Regulation Upload, Compliance, and Reporting System (TRUCRS). For each vehicle in your fleet, you will need:
- The 17-character Vehicle Identification Number.
- The Engine Family Name, a 12-character EPA code on the engine’s emission control label. The first character shows the model year; for 2026 engines that character is “T.”12Environmental Protection Agency. Information About Family Naming Conventions for Vehicles and Engines
- The Gross Vehicle Weight Rating, which determines how the vehicle is classified.
- The odometer reading, which tracks operational life for vehicles nearing removal thresholds.
- Fleet location, meaning the primary base of operations, cross-referenced with your business entity information.
If an engine’s emission label is missing or unreadable, contact the dealer or engine manufacturer with the engine serial number to get a replacement. Confirm the engine family name you record is the U.S. EPA and California code, not a European Commission code that some manufacturers print on the same label.
Once your data is assembled, you create a TRUCRS account, open the Advanced Clean Fleets module, select your compliance path, and enter the vehicle details. After submission, TRUCRS produces compliance reports and, if the fleet meets current requirements, a compliance certificate that serves as your official record for audits and inspections.13California Air Resources Board. Truck Regulations Upload, Compliance and Reporting System Reporting Guide
Charging Infrastructure Lead Times
For most fleets the tightest constraint is not the trucks. It is the charging infrastructure. Equipment procurement for commercial-grade chargers can take from six months to over two years. The full process from site planning through utility upgrades, permitting, installation, and commissioning routinely runs beyond a year.
That matters for two reasons. First, fleets that wait until a deadline is close are the ones most likely to need the infrastructure delay extension. Second, that extension requires proving you started the project at least a year before your compliance date, so the extension is only available to fleets that planned ahead.
Costs vary widely with the number of chargers, the level of electrical service upgrades needed, and local permitting. Total installed costs for DC fast charging capable of serving medium- and heavy-duty trucks can run from roughly $10,000 for a basic setup to well over $350,000 for a high-capacity depot. Engage your local utility early. Many utilities operate commercial fleet electrification programs that can reduce cost and shorten the interconnection timeline.