Ecology proposes new updates to help industry transition to clean semi-trucks

OLYMPIA  – 

The Washington Department of Ecology is proposing updates to regulations that reduce pollution from new semi-trucks and other commercial vehicles sold in the state. When combined with increased state funding, the updates will increase flexibility and help the industry transition to zero-emission trucks.  

These updates include changes to the Advanced Clean Trucks rule. Under the rule, manufacturers can gradually increase their zero-emission medium- and heavy-duty vehicle sales through 2035, or they can buy credits from other automakers who exceed requirements. These vehicles range from delivery vans to full-size semi-trucks and may be electric, plug-in hybrid, or other zero-emission technologies. The regulation recognizes that some routes and applications are still best served by diesel engines and does not seek to electrify all of these vehicles. 25-60% of the new medium- and heavy-duty vehicles sold in Washington can still be powered by diesel in 2035. 

Washington’s medium- and heavy-duty zero-emission vehicle sales have been strong – far higher than the regulation requires in most cases. Semi-trucks have lower sales requirements than smaller vehicles, but sales have also been slower to grow in this category. Ecology’s proposal eases semi-truck sales requirements in 2026 and gives manufacturers three years to make up any shortfalls. Ecology, industry and partner states continue to discuss additional ways to support transition in this sector while meeting program requirements.  

“Many Washington businesses are successfully switching to clean trucks. There are already over 9,000 clean trucks on our roads,” said Ecology Director Casey Sixkiller. “We want to see that momentum grow. That’s why we’ve been working with industry from the start to ensure this policy is successful. We continue to explore ways to set meaningful, achievable standards. These updates, combined with significant funding from the state, will help further this transition.” 

In 2025, state lawmakers boosted a Washington State Department of Transportation (WSDOT) program under development from $110 million to $126 million to subsidize zero-emission trucks and pay for charging infrastructure. The program, combined with Ecology’s proposal, is expected to address semi-truck issues through at least 2027. WSDOT is also partnering with other states to build public charging from Canada to Mexico. Washington’s portion of the West Coast Truck Charging and Refueling Corridor Project is $26.3 million, using federal, state and private funding.    

“This funding allows us to partner with private industry and put more zero-emission trucks on our roads,” said Secretary of Transportation Julie Meredith. “There are a lot of use cases for this technology, but we know cost can be a barrier when it comes to electrifying the heaviest trucks. So we’re thankful for the Legislature’s increased investment to help move this effort forward.” 

The Northwest Seaport Alliance also received $6 million from the state to fund zero-emission drayage semi-trucks that haul freight from the Ports of Seattle and Tacoma to nearby warehouses and rail stops. Similarly, the City of Seattle’s Office of Sustainability & Environment is advancing the transition to zero-emission drayage through a pilot program that helps trucking companies and owner-operators finance battery electric trucks. This program focuses on reducing emissions in port-adjacent communities and improving air quality through strategic partnerships and targeted investments. 

Advanced Clean Trucks is a critical tool for reducing climate pollution and ensuring all Washingtonians have healthy air to breathe. Transportation is Washington’s single largest source of greenhouse gas emissions, and the vehicles regulated by Advanced Clean Trucks contribute disproportionately. Heavy-duty trucks are also a major source of diesel pollution-- the most harmful air pollutant in Washington.  

Ecology is required to adopt these changes to align with California and other states that choose stronger regulations on vehicle pollution than the federal minimums. Washington is one of 11 states that adopted Advanced Clean Trucks, and together these states make up 25% of the medium- and heavy-duty vehicle market.  

Ecology will accept written public comments on the proposed rule changes from 12:00 a.m. May 15, 2025, through July 3, 2025 at 11:59 pm. The agency will also hold public hearings about the changes on June 24, 2025 at 9:00 am and on June 25, 2025 at 5:00 p.m. Ecology expects to adopt the changes in October 2025.