Vehicle emissions standards
ACT enforcement update
In response to manufacturer restrictions, we’ve temporarily updated our enforcement policy for certain vehicles covered by Advanced Clean Trucks and Heavy-Duty Low-NOx Omnibus to ensure state and local agencies can address public safety. For more information, see our statement.
Clean Vehicles Program rulemaking
Ecology is considering amendments to the Clean Vehicles Program rule. Visit our rulemaking page for more information, including upcoming virtual information sessions and recordings.
Washington is one of 17 states that adopt more stringent regulations on vehicle pollution from California known as “vehicle emissions standards.”
These standards apply to automakers — not individuals or businesses. Over time, they’ll increase the number of new clean vehicles available to Washingtonians. They also ensure that any new combustion-engine vehicles sold in our state produce less air pollution and fewer greenhouse gases. They don’t regulate used or off-road vehicles or ban the continued use of gas- or diesel-powered vehicles.
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Limiting greenhouse gas emissions
Our vehicle emissions standards are part of a strong suite of climate policies that work together to achieve Washington’s legal limits on greenhouse gas emissions. By law, we're required to reduce statewide emissions 45% by 2030, 70% by 2040, and 95% by 2050.
Transportation is our state’s biggest source of greenhouse gas emissions, so transitioning to clean vehicles is an essential part of addressing climate change. It also improves air quality.
Regulating new on-road vehicles
Under the federal Clean Air Act, states can either follow federal emissions standards or adopt California’s more stringent standards, but they can’t create their own.
In 2005, the Washington Legislature passed a law directing Ecology to implement California’s low-emission vehicle standards. In 2020, the Legislature passed another law requiring us to implement California’s zero-emission vehicle standards.
We’ve implemented four low- and zero-emission vehicle standards through the following regulations:
- Advanced Clean Cars
- Advanced Clean Cars II
- Heavy Duty Low-NOx Omnibus
- Advanced Clean Trucks
Together, these standards regulate all new on-road vehicles sold in Washington.
Low-emission standards vs. zero-emission standards
Washington has different low- and zero-emission vehicle standards for light-, medium-, and heavy-duty vehicles. These industry classifications are based on size and the maximum weight at which a vehicle can operate. Our standards also consider the expected pace of technological advancement for each vehicle class.
Washington’s LEV standards require that any internal combustion engine vehicle sold in our state emits less air pollution and fewer greenhouse gases. To comply, manufacturers must put their vehicles through California's emissions testing procedures.
Light-duty LEV standards were first adopted in Washington in 2005. Medium- and heavy-duty LEV standards were adopted in 2022 with the Heavy-Duty Low NOx Omnibus regulation.
ZEV standards require manufacturers to sell increasing percentages of new ZEVs in Washington or purchase credits generated by those who exceed sales requirements. ZEVs include battery electric vehicles and hydrogen fuel cell vehicles.
Certain plug-in hybrid electric vehicles may also count as ZEVs under Washington’s vehicle emissions standards, even though they aren't “true ZEVs.”
Plug-in hybrids can only make up a limited percentage of new vehicle sales and must meet all-electric range requirements that vary by the weight of the vehicle.
Light-duty ZEV standards were adopted through the Advanced Clean Cars rule in 2021 and the Advanced Clean Cars II rule in 2022. Medium- and heavy-duty ZEV standards were adopted through the Advanced Clean Trucks rule in 2021.
Related links
- Learn how we're planning for vehicle electrification
- States that have adopted California's vehicle regulations
- Responding to climate change
- Focus on medium- and heavy-duty low- and zero- emission vehicle standards
Contact information
Caroline Halter
Communications Manager
Caroline.Halter@ecy.wa.gov
564-669-8947
Dustin Watson
Mobile Source Air Quality Specialist
CleanVehicles@ecy.wa.gov