Washington Revised Code Title 46. Motor Vehicles § 46.09.360. Regulation by local political subdivisions or state agencies

(1) Notwithstanding any of the provisions of this chapter, any city, town, county, or other political subdivision of this state, or any state agency, may regulate the operation of nonhighway vehicles on public lands, waters, and other properties under its jurisdiction, and on streets, roads, or highways within its boundaries by adopting regulations or ordinances of its governing body, provided such regulations are not less stringent than the provisions of this chapter. However, the legislative body of a city or town with a population of less than three thousand persons may, by ordinance, designate a street or highway within its boundaries to be suitable for use by off-road vehicles. The legislative body of a county may, by ordinance, designate a road or highway within its boundaries to be suitable for use by off-road vehicles.

(2) For purposes of this section, “off-road vehicles” does not include wheeled all-terrain vehicles.