What action must be taken when a flagman is stationed on a leading flat?

When a flagman is stationed on a leading flat, it's essential to ensure communication with the motorman. This is because the motorman relies on clear instructions and information from the flagman to safely navigate the train, especially in areas where visibility may be limited or where specific safety protocols need to be adhered to. Effective communication helps in preventing accidents and ensuring that the train operates smoothly, particularly during maneuvers such as approaching blind curves, entering stations, or navigating areas with potential hazards.

Other options, while important in their own right, do not adequately capture the primary responsibility in this scenario. Monitoring the whole train involves a broader scope that goes beyond the immediate duties of the flagman. Checking safety procedures is generally a part of routine operations but does not specifically address the immediate actions required when a flagman is present. Similarly, indicating with a flashlight might be necessary in certain situations, but it is not the primary action that ensures the safety and coordination required in this context. Therefore, ensuring communication is paramount for operational safety and efficiency.