Chapter 173-423 WAC – Clean Vehicles Program

Ecology is considering amendments to Chapter 173-423 WAC, the Clean Vehicles Program rule. Washington law (RCW 70A.30.010) requires Ecology to adopt certain California regulations to maintain consistency with California’s emissions standards for new motor vehicles and engines.

To date, Ecology has delivered on this Legislative requirement to adopt regulations consistent with the following California programs: Advanced Clean Cars, Advanced Clean Cars II, Advanced Clean Trucks, and Heavy-Duty Low NOx Omnibus standards.

Ecology is currently considering amendments to Washington regulations that will track amendments to California’s Advanced Clean Trucks and Heavy-Duty Low-NOx Omnibus regulations currently adopted and/or under consideration by the California Air Resources Board (CARB). These amendments are important to streamline program implementation, provide additional compliance flexibility, and maintain consistency with other states and the federal government.

The Advanced Clean Trucks regulations apply to medium- and heavy-duty engine and vehicle manufacturers and require zero-emission models to make up an increasing percentage of new vehicle sales in Washington, starting with engine model year 2025. The Heavy-Duty Low-NOx omnibus regulation applies to heavy-duty internal combustion engine manufacturers and requires them to meet more protective air quality standards, particularly on oxides of nitrogen and particulate matter, starting in model year 2026.

Ecology is also inviting public input about additional California motor vehicle emissions standards the agency should consider adopting in a future rulemaking to comply with the requirements in Chapter 70A.30 RCW and efficiently and cost-effectively reduce greenhouse gas emissions from transportation in line with Washington’s greenhouse gas emissions reduction mandates in RCW 70A.45.020.