OLYMPIA, WA – The Washington Department of Ecology has announced proposed updates to its Advanced Clean Trucks rule, aiming to support the commercial vehicle industry’s shift toward zero-emission trucks. The changes, paired with over $130 million in anticipated state funding, are intended to ease the transition and address challenges specific to heavy-duty vehicles.
The proposed updates will allow manufacturers to either gradually increase their sales of zero-emission medium- and heavy-duty vehicles through 2035 or purchase credits from automakers who exceed the targets. While smaller vehicles have already surpassed regulatory sales requirements, sales of zero-emission semi-trucks have been slower. Ecology’s plan includes easing sales requirements for semi-trucks in 2026 and allowing a three-year window to make up any shortfalls.
The regulation allows 25% to 60% of new medium- and heavy-duty vehicles sold in Washington in 2035 to still be powered by diesel, acknowledging that some applications remain best suited to diesel engines.
State investments will support these changes. The Washington State Department of Transportation (WSDOT) program was increased from $110 million to $126 million this year, aimed at subsidizing zero-emission trucks and installing charging infrastructure. Washington is also participating in the West Coast Truck Charging and Refueling Corridor Project, contributing $26.3 million toward building charging stations from Canada to Mexico.
Additionally, $6 million has been allocated to the Northwest Seaport Alliance to support zero-emission drayage trucks serving the Ports of Seattle and Tacoma. The City of Seattle is also working on a pilot program to help trucking companies and owner-operators finance battery-electric drayage trucks.
Transportation remains the largest source of greenhouse gas emissions in Washington, with heavy-duty trucks contributing significantly to diesel pollution. Ecology is required to align these rule changes with California and other states that have adopted stricter vehicle emissions standards than federal requirements.
Public comments on the proposed rule changes will be accepted from May 15 through July 3, with public hearings scheduled for June 24 and June 25. Ecology expects to adopt the changes in October 2025.