What must a train do when following a Signal Yellow over Green?

When a train is following a Signal Yellow over Green, it indicates that the train is to prepare for a potential stop while being allowed to proceed towards the next signal. The yellow aspect signifies that the train must maintain approach speed, which allows the operator to be ready to stop for a signal that may be red or at the next limit of their movement.

This is crucial for ensuring safety on the rail network, as it allows the train to slow down in anticipation of a stop at the next signal. The yellow signal acts as a warning, indicating the need for caution. If a subsequent signal is indeed red, the train needs to be prepared to stop safely, thereby minimizing the risk of violations or accidents.

The proactivity encouraged by the yellow signal ensures that operators are always prepared for changes in conditions ahead, maintaining safe operational protocols. Thus, the correct approach in this situation is to maintain approach speed and be alert for the next indication, which aligns perfectly with the rules governing signal interpretations in rail operations.