When a member of the police department or members of the fire department or a person authorized by the chief of police or a person authorized by law are present, nonauthorized persons shall not direct or attempt to direct traffic by voice, hand or other signal except that persons may operate when and as provided in this title, any mechanical push-button signal erected by order of the city traffic engineer. Violation of this section is a misdemeanor as provided in Chapter 1.12. (Ord. 433 § 2, 1982).