May 2025
MassDEP announced that the agency will exercise enforcement discretion by not taking enforcement action against manufacturers that do not meet the Model Year 2026 and 2027 Advanced Clean Car II (ACC II) Zero Emission Vehicle (ZEV) sales compliance obligations.
- MassDEP adopted California's ACC II regulations in 310 CMR 7.40 in 2022. ACC II requires manufacturers of on-road passenger cars and light-duty trucks to produce and deliver for sale an increasing percentage of ZEVs starting in Model Year 2026 and increasing to 100% for Model Year 2035 and subsequent Model Years.
- MassDEP will exercise enforcement discretion by not taking enforcement action against manufacturers that do not meet the Model Year 2026 and 2027 ACC II ZEV sales compliance obligations.
- To qualify for this exercise of enforcement discretion, manufacturers shall not withhold internal combustion vehicles from car and truck dealerships seeking those vehicles.
- Each manufacturer also shall provide on a quarterly basis starting July 1, 2025, through July 1, 2027, reports detailing its efforts to: promote and market ZEVs; provide ZEVs for ride and drive events; increase deployment of charging infrastructure including investments in fast charging, level 2 charging, and home charging options; educate and train dealerships including sales and service staff on sales and maintenance of ZEVs; and increase ZEVs in fleets and ridesharing and ride hailing services. Manufacturers that do not meet these conditions will continue to be subject to all regulatory requirements in 310 CMR 7.40 for Model Year 2026 and 2027.
MassDEP Enforcement Discretion
April 2025
MassDEP announced that the agency will exercise enforcement discretion to exempt on-road medium- and heavy-duty vehicles in Classes 2b-8 from Advanced Clean Trucks (ACT) requirements in 310 CMR 7.40 in Massachusetts for Model Years 2025 and 2026, provided that manufacturers supply internal combustion (ICE) engines to distributors seeking those vehicles, without restriction.
- MassDEP adopted California's ACT regulations in 310 CMR 7.40 in 2021. ACT requires manufacturers of on-road medium- and heavy-duty vehicles to produce and deliver for sale an increasing percentage of zero emission vehicles (ZEVs) starting in Model Year 2025 through Model Year 2035.
- MassDEP will exercise enforcement discretion by not taking enforcement action against manufacturers that do not meet their Model Year 2025 or Model Year 2026 ACT ZEV sales compliance obligations. To qualify for this exercise of enforcement discretion, manufacturers must supply ICE vehicles to distributors seeking them, without restriction — i.e., manufacturers may not engage in withholding or rationing practices.
- While manufacturers were involved in developing the ACT framework, they now indicate that ACT requirements are too difficult to meet. Some manufacturers are limiting ICE truck sales as a means to ensure their compliance with ACT sales requirements, reducing availability to a wide range of users. Further, the current federal administration has created significant uncertainty around ZEV incentives, charging investments, manufacturing and tariffs, each of which threaten a smooth transition to medium- and heavy-duty ZEVs.
- This enforcement discretion replaces and supersedes the ACT enforcement discretion MassDEP issued on October 18, 2024 (i.e., state and local agencies no longer need to submit written requests regarding purchases of snow removal and street-sweeping vehicles since all medium- and heavy-duty vehicle purchases are covered by this updated enforcement discretion).
MassDEP Enforcement Discretion
November 2024
The emergency regulations amendments to 310 CMR 7.40 went into effect on November 4, 2024, and incorporate regulations promulgated by the California Air Resources Board for the Heavy-duty Omnibus model year 2026 legacy engine provisions, clarify exemptions for transit buses, emergency vehicles and military tactical vehicles, and delays the Heavy-duty Omnibus effective model year from model year 2025 to 2026.
- MassDEP is providing two public hearings and a public comment period on the emergency regulations, which may be modified after public hearing and comment.
- The public hearings will take place: Monday, December 9, 2024, at 1:00 PM and 5:30 PM (EST).
- The emergency regulations, background information, and public hearing registration information are available on MassDEP’s web site at 310 CMR 7.00: Air Pollution Control.
October 2024
MassDEP announced that the agency plans to file emergency regulations, which will be effective on filing, to delay implementation of the Heavy-Duty Omnibus (HDO) regulation until Model Year (MY) 2026 and will exercise enforcement discretion under the Advanced Clean Trucks (ACT) regulation to exempt vehicles purchased by state and local agencies for snowplowing and snow removal purposes (e.g., dump trucks, salt and sand spreaders, front end loaders) and street sweepers for MY 2025 and MY 2026.
- Massachusetts is required by state law to adopt certain California vehicle emission standards. The standards adopted through this requirement for passenger vehicles has led to lower transportation emissions, adoption of hybrid and electric vehicles by over 125,000 residents, businesses, and state and local agencies, and less poor air quality days.
- In 2021, as part of the Motor Vehicle Emissions Standards law, Massachusetts adopted California’s emission standards for medium- and heavy-duty trucks.
- Those standards come in the form of two regulations, (1) the Heavy-duty Omnibus (HDO) Regulation (requiring manufacturers to sell lower emissions engines) and (2) the Advanced Clean Trucks (ACT) Regulation (requiring a certain percentage of manufacturers’ overall sales to include sales of Zero Emission Vehicles).
- California has not yet received the required waiver from the U.S. Environmental Protection Agency (EPA) to enforce the Heavy-duty Omnibus Regulation, therefore California (and Massachusetts) cannot enforce the regulation. In addition, MassDEP has been informed that there may not be a sufficient supply of engines which comply with the Heavy-duty Omnibus Regulation.
- For those reasons, MassDEP is updating the first year of the Heavy-duty Omnibus Regulation compliance to begin in Model Year 2026.
- The Advanced Clean Trucks rule sets a minimum percentage requirement for the sale of zero emission vehicles (ZEVs) by manufacturers and provides the ability for manufacturers to buy credits to make up for any lack of ZEV sales.
- MassDEP has heard directly from cities and towns that manufacturers are restricting the sales of diesel vehicles in order to comply with the regulation.
- Municipalities have also expressed challenges with identifying electric trucks that serve their needs and concerns about charging infrastructure, particularly for handling potential snow emergencies.
- To address these concerns and provide more flexibility to dealers and purchasers, MassDEP is providing exemptions for snow removal vehicles (e.g., dump trucks, salt and sand spreaders, front end loaders) and street sweepers for Model Years 2025 and 2026 for state and municipal vehicle purchases.
- These added flexibilities will allow municipalities to procure the equipment they need while still making progress on decarbonizing our transportation sector.
MassDEP Enforcement Discretion
FAQ on MassDEP HDO and ACT Implementation
NESCAUM also has published FAQs on ACT and HDO.
CARB has published ACT Myth vs. Fact.
March 2023
MassDEP finalized regulations that took effect on December 30, 2022, amending 310 CMR 7.40: Low Emission Vehicle (LEV) Program, to adopt California’s Advanced Clean Cars II Regulation that requires increasing sales of zero emission vehicles (ZEVs) and Plug-In Hybrid Electric Vehicles (PHEVs).
September 2022
MassDEP hosted a pair of virtual stakeholder meetings to share information on its upcoming Massachusetts Advanced Clean Cars II Regulation, aimed at addressing emissions from light- and medium-duty on-road vehicles.
Presentation from Stakeholder Meetings, September 13 & 14, 2022
March 2022
MassDEP finalized regulations that took effect on December 30, 2021, amending 310 CMR 7.40: Low Emission Vehicle (LEV) Program, to adopt California’s:
- Advanced Clean Trucks (ACT) regulation for medium- and heavy-duty (MHD) vehicles;
- Phase 2 Greenhouse Gas (GHG) regulation for MHD engines and vehicles; and
- Heavy-Duty Omnibus regulation for heavy-duty engines and vehicles.
April 2021
MassDEP held two virtual public stakeholder meetings to share information on upcoming regulatory efforts to address criteria pollutant, greenhouse gas, and toxic air contaminant emissions from medium- and heavy-duty (MHD) on-road vehicles.
August 2020
Massachusetts joined with the states of Colorado, Connecticut, Delaware, Maine, Maryland, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, and Washington in supporting California’s agreements with BMW (including Rolls Royce), Ford, Honda, Volkswagen (including Audi and Porsche), and Volvo to voluntarily continue making annual reductions in greenhouse gas (GHG) emissions from their vehicles.
Gasoline and diesel cars and light trucks will get cleaner through model year 2026, preventing hundreds of millions of tons of GHG over the lifetime of the agreements.
See Additional Resources below to learn more about these Massachusetts and multi-state initiatives.