Municipal transit vehicle includes every motor vehicle, streetcar, train, trolley vehicle, and any other device, which (1) is capable of being moved within, upon, above, or below a public highway, (2) is owned or operated by a city, county, county transportation authority, public transportation benefit area, regional transit authority, or metropolitan municipal corporation within the state, and (3) is used for the purpose of carrying passengers together with incidental baggage and freight on a regular schedule.
RCW 46.04.355
Unlawful conduct in a transit vehicle: RCW 9.91.025.