Advanced Clean Fleets Regulation Summary
Accelerating Zero-Emission Truck Markets
The Advanced Clean Fleets (ACF) regulation is part of the California Air Resources Board’s (CARB or Board) overall approach to accelerate a large-scale transition to zero-emission medium- and heavy-duty vehicles. This regulation works in conjunction with the Advanced Clean Trucks (ACT) regulation, approved March 2021, which helps ensure that zero-emission vehicles (ZEV) are brought to market. More information on the ACT regulation is available in this fact sheet. The ACF regulation is critical to achieving both our health protective ambient air quality standards and the climate goals established Governor’s Executive Order N-79-20. This regulation is expected to save $26.5 billion in statewide health benefits from criteria pollutant emissions and a net cost savings of $48 billion to fleets. The following information summarizes the ACF regulation, which complements the ACT regulation, and is a part of a broader strategy to deploy medium- and heavy-duty ZEVs everywhere feasible.
Which fleets does the ACF regulation affect?
The ACF regulation applies to fleets performing drayage operations, those owned by State, local, and federal government agencies, and high priority fleets. High priority fleets are entities that own, operate, or direct at least one vehicle in California, and that have either $50 million or more in gross annual revenues, or that own, operate, or have common ownership or control of a total of 50 or more vehicles (excluding light-duty package delivery vehicles). The regulation affects medium- and heavy-duty on-road vehicles with a gross vehicle weight rating greater than 8,500 pounds, off-road yard tractors, and light-duty mail and package delivery vehicles.
What are the different components of ACF?
- Manufacturer sales mandate. Manufacturers may sell only zero-emission medium- and heavy-duty vehicles starting in 2036.
- Drayage fleets. Beginning January 1, 2024, trucks must be registered in the CARB Online System to conduct drayage activities in California. Non-zero-emission “legacy” drayage trucks may register in the CARB Online System through December 31, 2023. Legacy drayage trucks can continue to operate through their minimum useful life. Beginning January 1, 2024, only zero-emission drayage trucks may register in the CARB Online System. All drayage trucks entering seaports and intermodal railyards would be required to be zero-emission by 2035.
- High priority and federal fleets. High priority and federal fleets must comply with the Model Year Schedule or may elect to use the optional ZEVMilestones Option to phase-in ZEVs into their fleets:
- Model Year Schedule: Fleets must purchase only ZEVs beginning 2024 and, starting January 1, 2025, must remove internal combustion engine vehicles at the end of their useful life as specified in the regulation.
- ZEVMilestones Option (Optional): Instead of the Model Year Schedule, fleets may elect to meet ZEV targets as a percentage of the total fleet starting with vehicle types that are most suitable for electrification. The schedule is laid out in Table 1.
- State and local agencies. State and local government fleets, including city, county, special district, and State agency fleets, are required to ensure 50 percent of vehicle purchases are zero-emission beginning in 2024 and 100 percent of vehicle purchases are zero-emission by 2027. Small government fleets (those with 10 or fewer vehicles) and those in designated counties must start their ZEV purchases beginning in 2027. Alternately, State and local government fleet owners may elect to meet ZEV targets using the ZEV Milestones Option as shown in Table 1. State and local government fleets may purchase either ZEVs or near-ZEVs, or a combination of ZEVs and near-ZEVs, until 2035. Starting in 2035, only ZEVs will meet the requirements.
What is the ZEV Milestones Option?
Fleets that fall under the High Priority and Federal Fleets or the State and Local Government Fleets parts of ACF may choose to use the ZEV Milestones Option, shown in Table 1, to meet their ZEV targets.
Table 1: ZEV Fleet Milestones by Milestone Group and Year
Percentage of vehicles that must be
Milestone Group 1: Box trucks, vans, buses with two axles, yard tractors, light-duty package delivery vehicles
2035 and beyond
Milestone Group 2: Work trucks, day cab tractors, buses with three axles
2039 and beyond
Milestone Group 3: Sleeper cab tractors and specialty vehicles
2042 and beyond
How will this regulation affect existing trucks or equipment?
The ACF regulation will transition fleets to ZEVs over the course of the upcoming decades and guarantees a full useful life. The ACF regulation’s default Model Year Schedule begins in 2024, and allows drayage and high priority and federal fleets to continue using their existing trucks until the earlier of 18 years or 800,000 miles or a minimum of 13 years if the truck has over 800,000 miles. State and local government fleets have no requirement to end the use of their existing compliant vehicles. This means affected fleets may keep their existing combustion-powered vehicles for the full useful life provided by Senate Bill 1 (Beall, Statutes 2017, Chapter 5) under the Model Year Schedule. As an alternative to the Model Year Schedule, the ZEV Milestones Option is phased-in over almost two decades and allows fleets full flexibility to manage their fleet composition over the phase-in period, as long as the ZEV Milestones targets are met.
What if there isn’t a zero-emission truck to replace what a fleet needs?
There are over a hundred ZEV models available now and more are coming as manufacturers begin to ramp up their sales. However, the High Priority and Federal Fleets and the State and Local Government Fleets requirements include an exemption for cases in which a ZEV is not available for purchase and is needed to comply. The ZEV Purchase Exemption allows a fleet owner to purchase a new internal combustion engine vehicle and exclude it from the internal combustion engine vehicle removal requirement of the Model Year Schedule, or exclude it from the ZEV Milestones calculation. Exemptions to purchase internal combustion engine vehicles would only be needed if the fleet cannot otherwise meet the ZEV targets. A list of vehicles that are not available as ZEVs or near-ZEVs will be kept on the CARB website, and fleet owners can apply for fleet-specific exemptions if the needed vehicle is not listed and if the fleet falls under the High Priority and Federal Fleets or the State and Local Government Fleet requirements.
Zero-emission truck availability (as of July 2022)
The ACF regulation will be phased-in over the next two decades, allowing fleets time to replace their existing conventional medium- and heavy-duty vehicles with comparable ZEVs. Fleet managers with vehicles in Milestone Group 3, which includes specialty vehicles, will have the most time to make decisions about the order and timing of vehicle replacements in their fleets. The specialty truck and sleeper cab tractor phase-in requirement starts in 2030, and by this time, ZEV technology is expected to have advanced to the point that range and vehicle weight are no longer barriers. Based on Large Entity Reporting data collected in 2021, 3 percent of the medium- and heavy-duty vehicles in California are specialty vehicles, as defined in the ACF regulation.
How many vehicles will be affected by the ACF regulation?
The ACF regulation is expected to significantly increase the number of medium- and heavy-duty ZEVs on California roads, beyond the sales expected from the ACT regulation. The 2 regulations together are expected to result in about 510,000, 1,350,000 and 1,690,000 ZEVs in California in 2035, 2045, and 2050, respectively. Figure 1 below provides details of these increases over time.
Figure 1: Statewide medium- and heavy-duty ZEV population forecast
CARB staff estimate that, of the 1.8 million medium- and heavy-duty vehicles operating daily in California, 532,000 will be subject to ACF fleet requirements. Figure 2, below, shows how many vehicles in certain groups of vehicle classes are estimated to be subject to the ACF regulation, and what percentage of the vehicles that operate in California that is. The regulation focuses on the truck types that pollute the most; 67 percent of all Class 7-8 tractors, the largest polluters, will be covered.
Figure 2: Projected percentage of vehicles affected by regulation
Why do we need the ACF regulation?
The primary goal of the ACF regulation is to accelerate the market for zero-emission trucks, vans, and buses by requiring fleets that are well suited for electrification, to transition to ZEVs where feasible. The Board directed CARB staff to ensure that fleets, businesses, and public entities that own or direct the operation of medium- and heavy-duty vehicles in California purchase and operate ZEVs to achieve a smooth transition to ZEV fleets by 2045 everywhere feasible, specifically to reach:
- 100 percent zero-emission drayage trucks, last mile delivery, and government fleets by 2035
- 100 percent zero-emission refuse trucks and local buses by 2040
- 100 percent zero-emission capable utility fleets by 2040
Achieving these and other milestones will also contribute to meeting the goals in the Governor’s Executive Order N-79-20. The ACF regulation continues the progress toward meeting public health and climate goals by reducing emissions from the medium- and heavy-duty vehicles on California roads, as shown in Table 2 below.
Table 2: ACF’s cumulative total emissions reductions from 2024 to 2050 relative to the Legal Baseline
Oxides of Nitrogen (NOx)
Fine Particulate Matter (PM2.5)
Carbon Dioxide (CO2)
Emissions reductions from ACF
327 million metric tons
Are zero-emission trucks available and suitable for today’s fleets?
Medium- and heavy-duty ZEVs that are commercially available today are already capable of meeting the daily needs of most local and regional trucking operations and a variety of vocational uses. The ACF regulation also provides flexibility to phase-in ZEVs in the most suitable portions of the fleets, first. Fleet owners reported information about their vehicles and operations as part of the Large Entity Reporting data collected in 2021 that shows that the vast majority of trucks drive 100 miles or fewer per day. Figure 3 provides additional detail. Today’s medium- and heavy-duty ZEVshave energy storage systems that can meet most of these daily operational requirements.
Figure 3: Estimated average daily mileages for select vehicle categories in Large Entity Reporting
How will disproportionately impacted communities benefit from the ACF regulation?
The regulation will accelerate the deployment of ZEVs and the air quality benefits they offer, to communities most impacted by harmful truck emissions. Neighborhoods located near seaports, intermodal railyards, warehouses, and distribution centers are disproportionately affected by high truck traffic from medium- and heavy-duty trucks. The drayage component of the regulation would require by 2035, that all trucks entering the seaports and intermodal railyards be zero-emission, which will greatly benefit air quality in neighborhoods surrounding these locations. Overall, this regulation will result in nearly half of all semi-trucks that travel on our highways to be zero-emission by 2035 and about 70 percent to be zero-emission by 2042. The regulation will also affect the vehicles that operate directly in neighborhoods such as delivery trucks, garbage trucks, and utility trucks. This will greatly reduce the harmful impacts of tailpipe emissions and disruptive noise in California communities.
Can zero-emission trucks save fleets money?
Yes, zero-emission trucks have lower operating and maintenance costs than conventional trucks which can help offset the higher initial purchase price. Today, the total cost of ownership in California may be comparable to conventional trucks for certain duty cycles and applications (without factoring in State or federal incentives). While ZEVs are expected to cost more up front today, reduced fuel costs, lower maintenance expenses, and Low Carbon Fuel Standard revenues are expected to deliver a net savings of $48 billion to fleets. As components and battery prices fall and technology continues to improve, total cost of ownership is expected to become more favorable.
Is there funding for purchasing zero-emission trucks?
The 2021 and 2022 State budgets include a total investment of $10 billion over 6 years to reduce CO2 emissions from the transportation sector by supporting ZEVs and ZEV infrastructure. This funding will be administered by CARB, the California Energy Commission, the California State Transportation Agency, and the Governor’s Office of Economic and Business Development. This new funding builds on ZEV and ZEV infrastructure investments made by the State for more than a decade. These investments will focus on an equitable ZEV transition by continuing to find ways to support disproportionately impacted communities.
Several funding programs are available to support the use of advanced technologies, and because funding programs only pay for early adoption not for compliance, more funding opportunities exist for those fleets that act early. These programs are administered by State agencies, federal agencies, and local air districts. For example, the Hybrid and Zero-Emission Truck and Bus Voucher Incentive Project (HVIP) provides point-of-sale rebates to help offset the purchase price of Class 2b through 8 battery electric and fuel cell electric trucks and buses. Larger rebates are available for public fleets and small private fleets with vehicles located in disproportionately impacted communities. A list of all vehicles that are currently eligible for funding is available at California HVIP.
The Innovative Small e-Fleet Pilot Project is a $35 million set-aside within HVIP to pilot an incentive program geared toward helping small trucking fleets and independent owner operators access zero-emission trucks. This pilot project opened for voucher requests from eligible small fleets in August 2022. More information on this program is available at the California HVIP small e-fleets webpage.
The Carl Moyer Memorial Air Quality Standards Attainment Program funds the replacement of old, high-polluting vehicles, engines, and equipment, with new technologies that are cleaner than required, or earlier than what is required by rules and regulations. Grant amounts are based on the cost-effectiveness of harmful pollutants that will be reduced by the project. This program may also fund the installation of charging and fueling infrastructure. More information on this program is available at the Carl Moyer webpage.
The Truck Loan Assistance Program helps small-business fleet owners secure financing for upgrading their fleets with newer trucks. Small business truck owners with 100 or fewer employees, $10 million or less in annual revenue averaged over 3 years, and fleets with 10 or fewer heavy-duty vehicles subject to the In-Use Truck and Bus Regulation are eligible to seek financing under this program. More information on this program is available at the Truck Loan Assistance Program. This program is being redesigned as the Zero-Emission Truck Loan Pilot to better support the financing of zero-emission trucks along with any needed charging or fueling infrastructure, providing a streamlined lending process for small businesses that are transitioning to ZEVs.
The Fiscal Year 2022-23 Funding Plan for Clean Transportation Incentivesprovides additional funding for zero-emission refusetrucks. Refuse trucks are present in all communities statewide, but their impacts are felt particularly strongly by disproportionately impacted communitiesthat are located near waste transfer stations andare burdened by multiple pollution sources. There are at least 12 battery electric refuse truck models availablefor incentives through HVIP. To learn more about the 2022-2023 Funding Plan, see the Funding Plan webpage.
In addition to California’s funding programs, the federal Inflation Reduction Act of 2022 provides complementary and substantial new funding for zero-emission trucks and related infrastructure. The federal Infrastructure Investment and Jobs Act of 2021 provides $550 billion in new infrastructure investments, including for roads, bridges, public transit, water infrastructure, resilience, and broadband. For more information about CARB’s or federal funding opportunities, visit CARB Incentive Programs, the U.S. Department of Energy’s Alternative Fuels Data Center, the federal Inflation Reduction Act's energy and infrastructure provisions, and the Federal Highway Administration webpage on implementation of the Infrastructure Investment and Jobs Act.
Technical and financial assistance for infrastructure is also available through several programs. The California Public Utilities Commission has approved $1.054 billion to support medium- and heavy-duty charging installation pursuant to Senate Bill 350. In addition to this funding, investor-owned utilities are authorized to make investments in utility-side infrastructure upgrades to support transportation electrification pursuant to Assembly Bill 841. The California Energy Commission is also working to accelerate medium- and heavy-duty vehicle infrastructure for both charging and hydrogen refueling, and will invest $2.69 billion from the current State budget in infrastructure that will serve light-, medium-, and heavy-duty infrastructure. The recently launched EnergIIZE program provides energy infrastructure incentives for commercial vehicle fleets.
What is being done to increase charging and hydrogen fueling infrastructure for ZEVs?
The ACF regulation specifically focuses on the early transition to zero-emission trucks that typically return to base operations where fleets would install charging and/or hydrogen fueling stations for their own needs. The public sector, with the California Energy Commission in the lead, is planning for and investing in the expansion of charging and hydrogen fueling infrastructure. Their draft Zero-Emission Vehicle Infrastructure Plan and their Electric Vehicle Charging Infrastructure Assessment provide more information about what the State is doing to help meet fleets’ needs with respect to infrastructure. The California Energy Commission’s Integrated Energy Policy Report is theState’s blueprint for energy generation and supply, which is used by investor-owned utilities for their own infrastructure planning needs. In addition to State efforts, the private sector—including vehicle manufacturers—have made announcements regarding investments in installing publicly available charging and/or hydrogen fueling station networks, along both the east and west coasts of the U.S. and in Texas, and between several of California’s largest metropolitan areas.
What are the next steps?
The ACF regulation will move medium- and heavy-duty ZEVs into the mainstream by focusing on those fleets that are best able to be on the leading edge, and those of the greatest public health concern. The 2022 State Strategy for the State Implementation Plan describes efforts beyond ACF and the ACT regulation. This plan also describes the new authorities that would be needed for CARB to accelerate the full transition to zero-emission trucks in a way that minimizes administrative burden for fleet owners and CARB, and that creates market mechanisms to encourage those who have operations that are suitable for electrification to act early while allowing more time for those who can’t.
Where can more information be found?
Information about the ACF Regulation and upcoming meetings, workshops, and events is available at the ACF website. Information about all medium- and heavy-duty zero-emission regulations, funding, and background can be found at ZEV TruckStop.
If you have questions or wish to obtain this document in an alternative format or language, call (916) 323-2927. For TTY/TDD/Speech-to-Speech users, dial 711 for the California Relay Service.