Members of the police department, special police, auxiliary police and marshals assigned to traffic duty are authorized to direct all traffic in accordance with the provisions of this title, or in emergencies, as public safety or convenience may require, and it is unlawful for any person to fail or refuse to comply with any lawful order, signal or direction of a policeman, and except in case of emergency, it is unlawful for any person not authorized by law to direct or attempt to direct traffic. (Prior code § 24-2-1)