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Regulatory guidance and rulemaking

Ecology is temporarily pausing portions of Advanced Clean Cars II, Advanced Clean Trucks, and Heavy-Duty Low NOx Omnibus implementation in response to recent federal actions. Read more here.  

During this pause Ecology will continue our current rulemaking for amendments to Advanced Clean Trucks and Heavy-Duty Low NOx Omnibus. 

Transportation is our state’s biggest source of greenhouse gas emissions and a leading source of air pollution. Transitioning to clean vehicles is an essential part of addressing climate change. It also reduces health risks, like asthma, by improving air quality.


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Washington is one of 17 states, in addition to Washington D.C., that adopts 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, on-road vehicles available to Washingtonians and ensure that any new combustion-engine vehicles sold in our state produce less air pollution and fewer greenhouse gases. 

They won't affect the used car market or prohibit people from continuing to use gas- or diesel-powered vehicles. 

Frequently asked questions

How the standards work


How the standards affect drivers


Common misconceptions


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