Chapter 173-423 WAC – Clean Vehicles Program
On October 16, 2025, Ecology adopted amendments to our Clean Vehicles Program Rules (Chapter 173-423 WAC) to incorporate changes to the Advanced Clean Trucks and Heavy-Duty Low NOx Omnibus regulations adopted by the California Air Resources Board (CARB). These regulations are an essential policy tool for addressing climate change and improving air quality in Washington.
These amendments respond to industry concerns by easing compliance requirements for the heaviest vehicles. They also streamline implementation and maintain consistency with state and federal laws. Advanced Clean Trucks applies to medium- and heavy-duty engine and vehicle manufacturers. It requires manufacturers to gradually sell more new zero-emission models in Washington through model year 2035 or buy credits from manufacturers who exceed sales requirements. Credits give manufacturers flexibility in meeting the zero-emission sales requirements. Heavy-Duty Low NOx Omnibus requires that any new heavy-duty internal combustion engines sold in Washington meet more protective air quality standards, particularly on emissions of oxides of nitrogen and particulate matter, starting in model year 2026.
Rulemaking timeline
Announcement phase (CR-101)
Filing date:
Nov. 20, 2024
Announcement documents
Rule development phase
Nov. 20, 2024 - May 2025Public input & involvement
Ecology's public meetings
Public comment period (informal)
Dec. 2, 2024, midnight – Feb. 9, 2024, 11:59 p.m.
Read the comments on the Clean Vehicles Program rulemaking.
| Date | Documents | Location |
|---|---|---|
|
Public Information Session Tuesday, Dec. 10, 2024 |
Presentation | |
|
Combined Community Forum Wednesday, Jan. 29, 2025 |
Presentation | Community forum recording |
|
Industry Focused Public Meeting Thursday, Jan. 30, 2025 |
Presentation | Meeting recording |
|
Public Information Session Monday, Feb. 3, 2025 |
Presentation | Session recording |
Rule proposal phase (CR-102)
May 15, 2025
- Proposal notice (CR-102 form)
- Proposed rule language
- SEPA Determination of Non-significance and Environmental Checklist
Comment period
The comment period closed July 3, 2025, at 11:59 p.m. Please see submitted comments here.
Public hearings for this rulemaking were held on June 24, 2025, at 9 a.m. and June 25, 2025, at 5 p.m. Please see recordings and presentation materials below.
The hearings began with a short presentation and question-and-answer session, followed by the opportunity to provide testimony. Written comments receive the same consideration as verbal testimony.
Rule adoption phase (CR-103)
Oct. 16, 2025
Nov. 16, 2025
Accessibility
To request ADA accommodation for disabilities, or printed materials in a format for the visually impaired, contact Ecology's ADA Coordinator by email at ecyadacoordinator@ecy.wa.gov, or call 360-407-6831. People with impaired hearing may call Washington Relay Service at 711. People with speech disability may call TTY at 877-833-6341.