It shall be unlawful for any person unnecessarily to drive at such a slow speed as to impede or block the normal and reasonable movement of traffic, except when reduced speed is necessary for safe operation. Police officers are hereby authorized to enforce this provision by directions to drivers, and in the event of apparent willful disobedience to this provision and refusal to comply with the direction of an officer in accordance herewith, the continued slow operation by a driver shall be a misdemeanor.

(Code 1964, § 12.215)