Name one signal used for train control.

The semaphore signal is a critical component in train control systems, historically used to communicate operational status to train crews. It consists of a movable arm that is raised or lowered to indicate different commands. For instance, a raised arm typically signals "stop," while a horizontal arm means "proceed." Semaphore signals are strategically placed along the tracks, allowing engineers to receive real-time information on whether they should stop or continue movement based on track conditions and safety protocols.

This method of signaling is particularly important in maintaining safe distances between trains, managing traffic at junctions, and ensuring adherence to operational procedures. Its distinct visual representation makes it easier for locomotive engineers to quickly interpret the signals during various weather conditions or at night.

In contrast, traffic lights and stop signs are more associated with road traffic control, while crossing gates are safety mechanisms used at rail crossings to prevent vehicles from entering the track area when a train is approaching. They do not provide the comprehensive and direct communication needed for train operation that semaphore signals do.