What is the procedure if a red flag is displayed?

When a red flag is displayed, the correct procedure is to stop and wait for permission. This is a critical safety measure in railroad operations as it indicates a danger or obstruction on the tracks that requires immediate attention. Stopping allows for assessment of the situation before taking further action, thereby ensuring the safety of train operations and personnel.

The need to stop ensures that operators do not inadvertently proceed into a hazardous situation, as moving forward without permission might lead to accidents or collisions. It is essential to adhere to this protocol, as it reinforces the importance of communication and clearance before proceeding, which is vital in the context of railroad safety.

The other options suggest either cautious movement or continuing at a restricted speed, which could result in unsafe conditions if the underlying reason for the red flag is not fully understood or resolved. Therefore, stopping and waiting for permission is the appropriate response to ensure all risks are assessed and safety is prioritized.