No person shall ride in or jump into or upon any vehicle without the consent of the driver, and no person shall, when riding, allow any part of the body to project beyond the limits of any motor vehicle, except when signaling according to law, nor shall any person board or alight from, nor hang onto any motor vehicle, when such motor vehicle is in motion. This section shall not apply to authorized emergency vehicles.
(`89 Code, § 120.060) Penalty, see § 10.99