What is required for each train regarding radio communication?

A working radio on the leading end of the controlling engine is essential for maintaining effective communication throughout the train's operation. This radio ensures that the crew can receive crucial information from dispatchers, other trains, and trackside personnel. It is particularly important for safety and operational efficiency, allowing for timely updates regarding track conditions, signals, and any potential hazards along the route.

In this context, having a functioning radio at the leading end of the train is a regulatory requirement, as it enables the crew to maintain direct communication as they approach road crossings or other critical areas where timely communication is vital. This setup also allows the crew to communicate with each other and coordinate actions effectively.

While the other options might contribute to overall communication efficiency or support, they do not fulfill the specific requirement that the leading engine must be equipped with a working radio for operational continuity.