Red lights, often used in traffic signals, indicate that vehicles must stop. This warning helps prevent accidents by controlling the flow of traffic at intersections. When a red light is illuminated, drivers should remain stationary until the light changes to green, signaling that it is safe to proceed. In addition to traffic signals, red lights can also serve as warnings in various contexts, such as in electrical systems or safety equipment. For example, a red warning light on a machine may indicate a malfunction or the need for maintenance, alerting users to take immediate action to ensure safety.