HAND SIGNALS are legally recognized substitutes for vehicle turn signals in all US states and are required knowledge for every driver's license applicant.
When to use hand signals: When turn signals are inoperative (bulb out, electrical fault); when driving a vehicle not equipped with turn signals (antique vehicles, bicycles, etc.); in some situations where signals might not be visible. THE THREE HAND SIGNALS — USING THE LEFT HAND OUT THE WINDOW:
Left turn: Arm extended straight out horizontally to the left.
Right turn: Arm bent upward at the elbow — forearm pointing straight up, hand pointing up.
Stop/slow down: Arm bent downward at the elbow — forearm pointing straight down, hand pointing down.
How to use them: Roll down the window; extend the left arm out before the maneuver (same timing as turn signal); after completing the turn, withdraw the arm and resume normal driving.
Practical limitations: Hand signals can be difficult to see in heavy rain, at night, or in bright sunlight; they require taking one hand off the wheel; they are legally sufficient but less practical than vehicle signals.
Important: A broken turn signal should be repaired as soon as possible. Driving regularly with inoperative signals is a vehicle equipment violation in most states, separate from the signaling obligation.