What should you do when encountering an unexpected signal change?

When encountering an unexpected signal change, the appropriate response is to stop as soon as possible. This action is crucial for ensuring safety on the railway, as unexpected signal changes can indicate various conditions that may require immediate attention, such as a train ahead, track issues, or other potential hazards.

Stopping promptly allows for a thorough assessment of the situation and ensures that any necessary safety procedures or communications can be enacted effectively. It prevents the risk of proceeding under uncertain conditions, which could lead to accidents or collisions. Therefore, recognizing the importance of a signal as a directive for safe operation and prioritizing safety by stopping is vital in these situations.