for the purposes of this chapter, means any device upon which a person may ride, which is propelled by human power through a system of belts, chains or gears having either two or three wheels (one of which is at least twenty inches in diameter) or having a frame size of at least fourteen inches, or having four or more wheels.
(Ord. 520 § 1, 1975; Ord. 689 § 1, 1988)