RCW 46.20.500
Special endorsement -- Exceptions.
(1) No person may drive either a two-wheeled or a three-wheeled motorcycle, or a motor-driven cycle unless such person has a valid driver's license specially endorsed by the director to enable the holder to drive such vehicles.
(2) However, a person sixteen years of age or older, holding a valid driver's license of any class issued by the state of the person's residence, may operate a moped without taking any special examination for the operation of a moped.
(3) No driver's license is required for operation of an electric-assisted bicycle if the operator is at least sixteen years of age. Persons under sixteen years of age may not operate an electric-assisted bicycle.
(4) No driver's license is required to operate an electric personal assistive mobility device or a power wheelchair.
(5) No driver's license is required to operate a motorized foot scooter. Motorized foot scooters may not be operated at any time from a half hour after sunset to a half hour before sunrise without reflectors of a type approved by the state patrol.