(A) (1) 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 division (A)(2) below.
(2) 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 the motor vehicle exceeds 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 14 feet. The latter measurement shall apply to any size vehicle and also to any combination of vehicles.
(47 O.S. § 11-605) (`90 Code, § 20-56)
(B) All signals herein required given by hand and arm shall be given from the left side of the vehicle in the following manner and the signals shall indicate as follows:
(1) Left turn: hand and arm extended horizontally.
(2) Right turn: hand and arm extended upward.
(3) Stop or decrease speed: hand and arm extended downward.
(47 O.S. § 11-606) (`90 Code, § 20-57)