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Vehicles
Transportation is the largest source of greenhouse gas emissions in King County, accounting for nearly half of all local emissions.
In response, the County is transitioning its fleets to zero-emission vehicles powered by electricity, while also adopting cleaner fuels and more efficient operating practices across King County Metro and other County vehicles to reduce emissions.
Policy and Goals
From King County’s 2025 Strategic Climate Action Plan (SCAP) and 18.22 Electric Vehicles for County.
- 18.22.01 Electric vehicles. King County’s vehicle electrification goals are:
- 100% zero-emission bus fleet by 2035
- 67% zero-emission ADA paratransit fleet by 2030
- 100% zero-emission rideshare fleet by 2030
- Install 125 chargers at County park-and-rides by 2030
- Transition 50% of light-duty vehicles to electric by 2025 and 100% by 2030
- Transition 50% of medium-duty vehicles to electric by 2028 and 100% by 2033
- Transition 50% of heavy-duty vehicles to electric by 2038 and 100% by 2043
- Install 450 chargers in County facilities by 2030
The SCAP includes measurable goals to hold the County accountable:
| Focus Area | Policy Target | Examples |
| Renewable Fuels | 50% renewable fuel use in diesel fleets by 2030 | Renewable diesel in transit/water taxis; blending older diesel vehicles |
|---|---|---|
| Zero-Emission Vehicles | 100% electric revenue buses by 2035 | Metro EV buses, EV charging rollout |
| EV Charging Infrastructure | 450 EV charging ports by 2030 | County facilities |
| GHG emission reduction in fleets | Reduce fleet GHGs by 70% by 2030 (vs 2017) | Combines fuels + electrification |
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| Alternative Fuel | Description |
| Electric (EV) | Runs entirely on batteries that power the motor. Offers lower fuel costs and reduces greenhouse gas emissions. |
|---|---|
| Hybrid-Electric (HEV) | Uses both gasoline and a battery that recharges during braking. Improves fuel efficiency and reduces emissions. |
| Biodiesel (B99-B100) | Made from animal or vegetable fats mixed with alcohol. Can be blended with petroleum diesel, such as B20 (20% biodiesel, 80% diesel). |
| Biodiesel (B20) | A common blend: 20% biodiesel and 80% petroleum diesel. Reduces emissions compared to conventional diesel. |
| Liquefied Natural Gas (LNG) | Natural gas cooled into a liquid. Modern engines achieve emissions similar to gasoline or diesel vehicles. |
| Ethanol (E85) | Made from corn or other plant materials. Usually blended with gasoline for a cleaner burn; lower energy content reduces fuel economy. |
| Compressed Natural Gas (CNG) | Natural gas compressed to less than 1% of its volume. Mostly methane; colorless, odorless, and tasteless. Offers emissions similar to gasoline and diesel. |
| Propane (LPG) | Liquefied petroleum gas stored as a liquid. Often used in high-mileage vehicles; can reduce maintenance costs. |
| Renewable Diesel | Produced from fats or vegetable oils, alone or blended with petroleum, and refined through hydrotreating. Provides a lower-emission diesel alternative. |
Fuel Guidance
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The U.S. Environmental Protection Agency (EPA), U.S. Department of Energy, and U.S. Department of Transportation certify the fuel economy labels for new vehicles sold in the U.S., which outline the vehicle’s fuel economy, fuel cost, greenhouse gas rating, and smog rating. |
U.S. Department of Energy: Alternative Fuels Data Center
High Performance Buildings Guide: Transportation and Automotive
Western Washington Clean Cities: Alternative Fuels
Atlas Public Policy: Fleet Procurement Analysis Tool