No pedestrian or driver of a vehicle shall disobey the instructions of any traffic control device placed in accordance with the provisions of this Traffic Code, unless at the time otherwise directed by a police officer.
No provisions of this Traffic Code for which signs are required shall be enforced against an alleged violator if at the time and place of the alleged violation an official sign is not in proper position and sufficiently legible to be seen by an ordinarily observant person. Whenever a particular section does not state that signs are required, such section shall be effective even though no signs are erected in place.
(ORC 4511.12)