A.
Required. The operator of a vehicle shall obey the instructions of any official traffic control sign, signal, marking or device applicable thereto placed in accordance with the provisions of this chapter or of the Vehicle and Traffic Law, unless otherwise directed by a traffic or police officer, subject to the exceptions granted the operator of an authorized emergency vehicle in the Vehicle and Traffic Law.
B.
Signs. No provisions of this chapter or of the Vehicle and Traffic Law 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 or in place.