If the turn indicators are not working, what must be used instead?

Using hand signals is the correct approach when the turn indicators are not functioning. Hand signals provide a clear and visible way to communicate your intentions to other drivers on the road, ensuring that they understand when you plan to turn or change lanes. This method is particularly useful since it is universally recognized and can be seen easily by surrounding traffic, even if the vehicle's signals aren't operational.

While other options like sounding the horn or using hazard lights serve different purposes, they do not effectively convey the specific message of turning or lane changing. Hazard lights indicate a temporary stop or a warning situation, and emergency flares are used to signal a breakdown or hazard on the road, not for turning. Therefore, hand signals are the most effective and appropriate alternative to convey turning intentions when turn indicators are unavailable.