Which signal indicates that a train must stop?

The signal indicating that a train must stop is represented by Red over Red. In railway signaling, a red light is universally recognized as a stop signal. When a train operator sees this signal, it means they must bring the train to a complete halt immediately before proceeding.

Understanding the importance of such signals is critical for safety and operational efficiency on the railway. Trains are required to respond to these signals to avoid collisions and maintain proper spacing between trains on the track. Signals serve as vital communication tools, conveying information about track conditions, speed restrictions, and actions that must be taken by the train crews.

In contrast, other signal combinations like Yellow over Green, Yellow over Red, and Green over Yellow indicate different conditions, such as caution or performance actions, rather than an immediate requirement to stop.