A person operating a motorcycle, motor scooter or a motor bicycle shall ride only upon the permanent and regular seat attached thereto and the operator shall not carry any other person nor shall any other person ride on the vehicle unless it is designed to carry more than one person, in which event a passenger may ride only upon the permanent and regular seat if designed for two persons, or upon another seat firmly attached to the rear or side of the operator.
(`90 Code, § 20-84)