Okla. Stat. tit. 47, § 47-11-605: Signals by hand and arm or signal lamps

(a) Any stop or turn signal when required herein shall be given

either by means of the hand and arm or by signal lamps, except as

otherwise provided in paragraph (b).

(b) Any motor vehicle in use on a highway shall be equipped

with, and required signal shall be given by, signal lamps when the

distance from the center of the top of the steering post to the left

outside limit of the body, cab or load of such motor vehicle exceeds

twenty-four (24) inches, or when the distance from the center of the

top of the steering post to the rear limit of the body or load

thereof exceeds fourteen (14) feet. The latter measurement shall

apply to any single vehicle, also to any combination of vehicles.