Final answer:
When vehicle turn indicators are not functioning, hand signals must be used to communicate directional intentions to other drivers as they are the correct alternative to indicate turns.
Step-by-step explanation:
If the turn indicators are not operating, hand signals must be used. Hand signals are an important form of communication for drivers when vehicle turn indicators fail. Using the correct hand signals can help communicate your intentions to other drivers while ensuring that you comply with traffic laws.
When the vehicle's indicators are not working, extend your arm straight out through the window to signal a left turn, and for a right turn, extend your arm out with the elbow bent upwards at a 90-degree angle. To indicate slowing or stopping, extend your arm out with the palm facing down and move the arm slightly up and down.
Using a horn is not a substitute for indicators as it does not signal direction, and headlights and brake lights cannot substitute for turn indicators because they do not indicate the intention to turn. Therefore, hand signals are the correct alternative to use.