How should protection be provided when workmen are on a main track?

When workmen are on a main track, the appropriate method of protection is to display a blue signal at each end of the rolling equipment. This is crucial because the blue signal serves as a visual warning to oncoming train crews that workmen are present on or near the tracks, ensuring their safety. The display of these signals alerts operators that they must not move any rolling stock within the protected area.

Having a blue signal at both ends ensures that coverage is complete, and it provides clear communication to all rail personnel regarding the presence of work crews. This proactive measure is essential for maintaining a safe working environment on the main track, thus preventing accidents that could occur if a train were to unexpectedly approach while workers are engaged in their tasks.

Other options do not meet the safety standards required for this situation, such as using a single blue signal, displaying a red flag at track intersections, or simply keeping trains stationary without defined communication through signals. Each of these alternatives lacks sufficient protection and fails to communicate clearly to all train crews, which is why they do not fulfill the requirements for safeguarding workmen on the tracks.