How should a train operator respond to a signal indicating "proceed with caution"?

When a train operator encounters a signal indicating "proceed with caution," the correct response is to move slowly and maintain vigilance. This signal is a warning that something may not be normal along the track ahead, such as potential hazards, track conditions, or other operational issues that require the train to operate at a reduced speed.

By traveling slowly, the operator has the opportunity to react appropriately to any unforeseen circumstances, such as obstacles on the track or signals requiring further action. Maintaining vigilance is crucial, as it allows the operator to observe the environment closely and respond quickly if needed.

This response ensures the safety of the train and its passengers by prioritizing cautious operation over maintaining full speed, which would be inappropriate given the warning expressed by the signal.