The two main laws on the use of turn signals are set out below. These laws are good to review, especially in the case that you see other drivers with their arms out the window and are wondering what they might be doing. These signals are important if break lights or turn signals are not properly working in a car.
55-8-143. Signals for turns.
(a) Every driver who intends to start, stop or turn, or partly turn from a direct line, shall first see that that movement can be made in safety, and whenever the operation of any other vehicle may be affected by such movement, shall give a signal required in this section, plainly visible to the driver of the other vehicle of the intention to make such movement.
(b) The signal required in this section shall be given by means of the hand and arm, or by some mechanical or electrical device approved by the department of safety, in the manner specified in this section. Whenever the signal is given by means of the hand and arm, the driver shall indicate the intention to start, stop, or turn, or partly turn, by extending the hand and arm from and beyond the left side of the vehicle, in the following manner:
(1) For left turn, or to pull to the left, the arm shall be extended in a horizontal position straight from and level with the shoulder;
(2) For right turn, or pull to the right, the arm shall be extended upward; and
(3) For slowing down or to stop, the arm shall be extended downward.
(c) These signals shall be given continuously for a distance of at least fifty feet (50′) before stopping, turning, partly turning, or materially altering the course of the vehicle.
(d) Drivers having once given a hand, electrical or mechanical device signal, must continue the course thus indicated, unless they alter the original signal and take care that drivers of vehicles and pedestrians have seen and are aware of the change.
(e) Drivers receiving a signal from another driver shall keep their vehicles under complete control and shall be able to avoid an accident resulting from a misunderstanding of the signal.
(f) Drivers of vehicles, standing or stopped at the curb or edge before moving these vehicles, shall give signals of their intention to move into traffic, as provided in this section, before turning in the direction the vehicle shall proceed from the curb.
55-8-144. Signals by hand and arm or signal device.
(a) Any stop or turn signal required by this chapter shall be given either by means of the hand and arm or by a signal lamp or lamps or mechanical signal device approved by the department of safety as provided in § 55-8-143, except as otherwise provided in subsection (b).
(b) Any motor vehicle in use on a highway shall be equipped with, and required signal shall be given by, a signal lamp or lamps or mechanical signal device approved by the department 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 twenty-four inches (24”), 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 feet (14′). The latter measurement shall apply to any single vehicle, also to any combination of vehicles.