WSR 25-21-084
PERMANENT RULES
DEPARTMENT OF ECOLOGY
[Order 24-07—Filed October 16, 2025, 7:27 a.m., effective November 16, 2025]
Effective Date of Rule: Thirty-one days after filing.
Purpose: The department of ecology (ecology) is adopting 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. 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. The advanced clean trucks program 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 and provides flexibility to manufacturers by allowing the purchase of credits from other manufacturers to meet this requirement, thereby offering manufacturers choice in which models to transition to zero-emissions technology. The heavy-duty low NOx omnibus regulation applies to heavy-duty internal combustion engine manufacturers and requires heavy-duty vehicles sold in Washington to meet more protective air quality standards, particularly on oxides of nitrogen and particulate matter, starting in model year 2026.
Citation of Rules Affected by this Order: Amending chapter 173-423 WAC, Clean vehicles program.
Statutory Authority for Adoption: Chapter
70A.30 RCW.
Other Authority: Ecology has completed an environmental justice assessment in accordance with RCW
70A.02.060 as a part of this rule making.
Adopted under notice filed as WSR 25-11-045 on May 15, 2025.
Number of Sections Adopted in Order to Comply with Federal Statute: New 0, Amended 0, Repealed 0; Federal Rules or Standards: New 0, Amended 0, Repealed 0; or Recently Enacted State Statutes: New 0, Amended 3, Repealed 0.
Number of Sections Adopted at the Request of a Nongovernmental Entity: New 0, Amended 0, Repealed 0.
Number of Sections Adopted on the Agency's own Initiative: New 0, Amended 0, Repealed 0.
Number of Sections Adopted in Order to Clarify, Streamline, or Reform Agency Procedures: New 0, Amended 0, Repealed 0.
Number of Sections Adopted using Negotiated Rule Making: New 0, Amended 0, Repealed 0; Pilot Rule Making: New 0, Amended 0, Repealed 0; or Other Alternative Rule Making: New 0, Amended 0, Repealed 0.
Date Adopted: October 16, 2025.
Casey D. Sixkiller
Director
RDS-6240.2
AMENDATORY SECTION(Amending WSR 23-01-102, filed 12/19/22, effective 1/19/23)
WAC 173-423-030Adoption by reference.
(1) This chapter adopts by reference the California Code of Regulations in the following titles:
(a) Title 13, sections 1900, 1956.8, 1960.1, 1961, 1961.1 to 1961.4, 1962.2 to 1962.8, 1963, 1963.1 to 1963.5, 1965, 1968.2, 1968.5, 1969, 1971.1, 1971.5, 1976, 1978, 2035 to 2040, 2046, 2109, 2111 to 2133, 2135, 2137, 2139 to 2149, 2166, 2166.1, 2167, 2168, 2169, 2169.1 to 2169.8, 2170, 2235, 2423, 2485 and Appendix A to Article 2.1 in section 2112;
(b) Exception to adopting Title 13 by reference. The following sections are not adopted by reference:
(i) Section 1956.8 (a)(2)(F); and
(ii) Section 1962.4 (e)(2)(A)3.a.i and ii; and
(c) Title 17, sections 95300 to 95307, 95311, and 95660 to 95663.
(2) Adoption or adoption by reference means the rule applies as if it was copied into this rule. California Code of Regulations means those provisions as adopted in final regulatory orders by the California Air Resources Board as they exist on ((September 7, 2022, or the adoption date in WAC 173-400-025(1), whichever is later))May 6, 2025.
(3) Copies of the relevant sections of California Code of Regulations adopted by reference in this chapter are available on ecology's website or by contacting:
Washington State Department of Ecology
((Air Quality))Climate Pollution Reduction Program
300 Desmond Drive
Lacey, WA 98503
360-407-6800
(4) For purposes of applying the adopted sections of California Code of Regulations in Washington, unless the context requires otherwise:
(a) "California" means "Washington";
(b) "CARB," "ARB," or "air resources board" means "ecology"; and
(c) "Executive officer" means "ecology."
AMENDATORY SECTION(Amending WSR 23-01-102, filed 12/19/22, effective 1/19/23)
WAC 173-423-040Definitions and abbreviations.
The following definitions apply to the administration of this chapter. Any term that is not defined in this section must be as defined or described in California Code of Regulations, Title 13, section 1900 or 1963, or Title 17, section 95662, as applicable. Definitions in California Code of Regulations, Title 13, section 1900 or 1963, or Title 17, section 95662 will prevail if any discrepancy arises.
(1) "Authorized emergency vehicle" is defined as provided in RCW
46.04.040.
(2) "Ecology" means the department of ecology.
(3) "Gross vehicle weight rating" or "GVWR" is defined as provided in California Code of Regulations, Title 17, section 95662 (a)(5), reprinted here.
"The value specified by the vehicle manufacturer as the maximum design loaded weight of a single vehicle, consistent with good engineering judgment."
(4) "Light-duty truck" is defined as provided in California Code of Regulations, Title 13, section 1900, reprinted here.
"Any 2000 and subsequent model motor vehicle certified to the standards in California Code of Regulations, Title 13, section 1961 (a)(1), 1961.2, or 1961.4 rated at 8,500 pounds gross vehicle weight or less, and any other motor vehicle, rated at 6,000 pounds gross vehicle weight or less, which is designed primarily for purposes of transportation of property or is a derivative of such a vehicle, or is available with special features enabling off-street or off-highway operation and use."
(5) "Manufacturer" is defined as provided in California Code of Regulations, Title 17, section 95662 (a)(11); California Code of Regulations, Title 13, section 1963(14); and California Code of Regulations, Title 13, section 1900 (8)-(10), summarized here.
(a) Any person engaged in the manufacturing or assembling of new motor vehicles or new motor vehicle engines, or importing such vehicles or engines for resale, or who acts for and is under the control of any such person in connection with the distribution of new motor vehicles and new motor vehicle engines, but shall not include any dealer with respect to new motor vehicles or new motor vehicle engines received by him in commerce. In general, this term includes any person who manufactures or assembles a vehicle (including a trailer or another incomplete vehicle) for sale in Washington or otherwise introduces a new motor vehicle into commerce in Washington. This includes importers who import vehicles for resale, entities that manufacture glider kits, and entities that assemble glider vehicles. This does not include persons who supply parts to the importer or vehicle manufacturer of record, nor does it include the secondary vehicle manufacturer.
(b) An independent low volume manufacturer, intermediate volume manufacturer, large volume manufacturer, or a small volume manufacturer, with volume status determined by sales in California and therefore consistent in all cases with California's determination of volume status per manufacturer, defined as provided in California Code of Regulations, Title 13, section 1900.
(6) "Medium-duty passenger vehicle" is defined as provided in California Code of Regulations, Title 13, section 1900, reprinted here.
(((6)))"Any medium-duty vehicle with a gross vehicle weight rating of less than 10,000 pounds that is designed primarily for the transportation of persons. The medium-duty passenger vehicle definition does not include any vehicle which: (1) is an "incomplete truck" i.e., is a truck that does not have the primary load carrying device or container attached; or (2) has a seating capacity of more than 12 persons; or (3) is designed for more than 9 persons in seating rearward of the driver's seat; or (4) is equipped with an open cargo area of 72.0 inches in interior length or more. A covered box not readily accessible from the passenger compartment will be considered an open cargo area, for purposes of this definition."
(7) "Medium-duty vehicle" is defined as provided in California Code of Regulations, Title 13, section 1900, reprinted here.
(((7)))"Any 2000 and subsequent model heavy-duty low-emission, ultra-low-emission, super-ultra-low-emission or zero-emission vehicle certified to the standards in California Code of Regulations, Title 13, section 1961 (a)(1), 1961.2, 1961.4, 1962, 1962.1, or 1962.2, having a manufacturer's gross vehicle weight rating between 8,501 and 14,000 pounds."
(8) "Military tactical vehicle" is defined as provided in California Code of Regulations, Title 13, section 1905, reprinted here.
"A motor vehicle owned by the U.S. Department of Defense and/or the U.S. military services and used in combat, combat support, combat service support, tactical or relief operations, or training for such operations."
(9) "Model year"((: Means))is defined as provided in California Code of Regulations, Title 17, section 95662 (a)(16), summarized here.
(a) The manufacturer's annual production period that includes January 1st of a calendar year, or if the manufacturer has no annual production period, the calendar year. The model year for a motor vehicle manufactured in two or more stages is the model year in which the chassis is completed, except for a vehicle subject to California Code of Regulations, Title 13, sections 1963 through 1963.5 (Advanced Clean Trucks)((: Is defined as provided in California Code of Regulations, Title 13, section 1963(c))).
(((8) "Manufacturer" means an independent low volume manufacturer, intermediate volume manufacturer, large volume manufacturer, or a small volume manufacturer defined as provided in California Code of Regulations, Title 13, section 1900.
(9)))(b) For a vehicle subject to California Code of Regulations, Title 13, sections 1963 through 1963.5, "model year" is defined as provided in California Code of Regulations, Title 13, section 1963(c), reprinted here.
"For tractors and vocational vehicles with a date of manufacture on or after January 1, 2021, the vehicle's model year is the calendar year corresponding to the date of manufacture; however, the vehicle's model year may be designated to be the year before the calendar year corresponding to the date of manufacture if the engine's model year is also from an earlier year. Note that 40 Code of Federal Regulations (CFR) § 1037.601 (a)(2), as amended October 25, 2016, limits the extent to which vehicle manufacturers may install engines built in earlier calendar years. Note that manufacturers may have other model year designations for the same vehicle for compliance with other requirements or for other purposes."
(10) "Passenger car" is defined as provided in California Code of Regulations, Title 13, section 1900, reprinted here.
(((10)))"Any motor vehicle designed primarily for transportation of persons and having a design capacity of twelve persons or less."
(11) "Transit agency" is defined as provided in California Code of Regulations, Title 13, section 2023, reprinted here.
(((11)))"A public entity responsible for administering and managing transit services. Public transit agencies can directly operate transit service or contract out for all or part of the total transit service provided. A transit agency does not mean a correctional facility, airport, college or university, national park, tour bus service providers, or an entity that provide shuttle services solely for patrons of its organization."
(12) "Zero-emission vehicle" or "ZEV" is defined as provided in California Code of Regulations, Title 13, section 1962.2(a).
"Vehicles that produce zero exhaust emissions of any criteria pollutant (or precursor pollutant) or greenhouse gas, excluding emissions from air conditioning systems, under any possible operational modes or conditions. Model years 2026 and subsequent passenger cars, light-duty trucks, and medium-duty vehicles are certified under California Code of Regulations, Title 13, section 1962.4."
AMENDATORY SECTION(Amending WSR 23-01-102, filed 12/19/22, effective 1/19/23)
WAC 173-423-081Medium- and heavy-duty vehicle emission standards.
(1) Requirements to meet California vehicle emission standards. These standards establish criteria and procedures for the manufacture, testing, distribution and sale of new ((on-highway)) medium- and heavy-duty trucks and engines in Washington as adopted by reference in WAC 173-423-030.
(2) Applicability.
(a) Starting with model year 2026, ((on-highway))on-road heavy-duty engines, trucks and trailers delivered for sale or sold in Washington, except as provided in WAC 173-423-060, must comply with California Code of Regulations, Titles 13 and 17, adopted by reference in WAC 173-423-030.
(b) Requirement to meet vehicle emission standards, testing procedures, warranty, reporting, enforcement, recall and other California provisions adopted by reference.
(i) Starting with the 2026 engine model year and for each engine model year thereafter no person may deliver for sale, or sell, in Washington any new ((on-highway))on-road heavy-duty engine unless the engine is certified to the California emission standards as required under WAC 173-423-030, except as provided in WAC 173-423-060 Exemptions.
(ii) Each manufacturer of new 2026 and subsequent model year ((on-highway))on-road medium- and heavy-duty engines and trucks and trailers must comply with each of the following applicable standards specified in California Code of Regulations, Title 13 adopted by reference in WAC 173-423-030:
(A) Section 1956.8 (a) - (f) and (i) Exhaust Emission Standards and Test Procedures - 1985 and Subsequent Model Heavy-Duty Engines and Vehicles. Except that California Code of Regulations, Title 13, Section 1956.8 (a)(2)(F) "Transit Agency Diesel-Fueled Bus Engine Exemption Request" must be disregarded and is not incorporated by reference;
(B) Section 1971.1 On-Board Diagnostic System Requirements - 2010 and Subsequent Model-Year Heavy-Duty Engines;
(C) Section 2036 Defects Warranty Requirements for 1979 Through 1989 Model Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles; 1979 and Subsequent Model Motorcycles and Heavy-Duty Vehicles; and Motor Vehicle Engines Used in Such Vehicles; and 2020 and Subsequent Model Year Trailers;
(D) Section 2121 Penalties;
(E) Section 2137 Vehicle, Engine, and Trailer Selection;
(F) Section 2139 Testing;
(G) Section 2139.5 CARB Authority to Test for Heavy-Duty In-Use Compliance;
(H) Section 2140 Notification and Use of Test Results;
(I) Section 2166 General Provisions;
(J) Section 2166.1 Definitions;
(K) Section 2167 Required Recall and Corrective Action for Failures of Exhaust After Treatment Devices, On-Board Computers or Systems, Urea Dosers, Hydrocarbon Injectors, Exhaust Gas Recirculation Valves, Exhaust Gas Recirculation Coolers, Turbochargers, Fuel Injectors;
(L) Section 2168 Required Corrective Action and Recall for Emission-Related Component Failures;
(M) Section 2169 Required Recall or Corrective Action Plan;
(N) Section 2169.1 Approval and Implementation of Corrective Action Plan;
(O) Section 2169.2 Notification of Owners;
(P) Section 2169.3 Repair Label;
(Q) Section 2169.4 Proof of Correction Certificate;
(R) Section 2169.5 Preliminary Tests;
(S) Section 2169.6 Communication with Repair Personnel;
(T) Section 2169.7 Recordkeeping and Reporting Requirements;
(U) Section 2169.8 Extension of Time;
(V) Section 2423(n) Exhaust Emission Standards and Test Procedures - Off-Road Compression-Ignition Engines; and
(W) Section 2485 Airborne Toxic Control Measure to Limit Diesel-Fueled Commercial Motor Vehicle Idling.
(iii) Each manufacturer of new 2026 and subsequent model year ((on-highway))on-road medium- and heavy-duty engines and trucks and trailers must comply with each of the following applicable standards specified in California Code of Regulations, Title 17 adopted by reference in WAC 173-423-030:
(A) Section 95660 Purpose;
(B) Section 95661 Applicability;
(C) Section 95662 Definitions; and
(D) Section 95663 Greenhouse Gas Exhaust Emission Standards and Test Procedures for New 2014 and Subsequent Model Heavy-Duty Vehicles.
(3) Recalls. Any order issued or enforcement action taken by the California Air Resources Board to correct noncompliance with any section of California Code of Regulations, Title 13, that results in the recall of any vehicle as required under California Code of Regulations, Title 13, sections 2109 - 2135, for a vehicle subject to the requirements adopted by reference in WAC 173-423-030, will be prima facie evidence concerning vehicles registered in Washington. If the manufacturer can demonstrate to ecology's satisfaction that the order or action is not applicable to vehicles registered in Washington, ecology will not pursue a recall of vehicles registered in Washington.
(4) Inspections and Information Requests.
(a) Ecology may inspect new and used motor vehicles and related records for the purposes of determining compliance with the requirements of this section. Ecology inspections will occur during regular business hours on public property or on any premises owned, operated, or used by any truck dealer or truck rental agency for the purposes of determining compliance with the requirements of this division.
(b) For the purposes of determining compliance with this section, ecology may require any truck dealer or truck rental agency to submit to ecology any documentation that ecology deems necessary to the effective administration and enforcement of this section. This provision does not require creation of new records.