Okla. Stat. tit. 47, § 47-11-201: Obedience to and required traffic-control devices

(a) The driver of any vehicle shall obey the instructions of any

official traffic-control device applicable thereto placed in

accordance with the provisions of this act, unless otherwise

directed by a traffic or police officer, subject to the exceptions

granted the driver of an authorized emergency vehicle in this act.

(b) No provision of this act 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.