Which option is true about how an extra train is designated?

The correct choice emphasizes that the designation of an extra train must include direction, which is essential for clarity in operations. Designating the direction ensures that all personnel involved, including conductors and dispatchers, are aware of where the train is heading, thereby maintaining safety and efficiency in train movements. Directional designation helps in coordinating with existing schedules, preventing conflicts and ensuring that the train will be effectively integrated into the rail network.

Other options do not reflect this requirement adequately. For instance, while a freight specification could apply to certain train types, it is not universally required for all extra trains. Referring to a specific schedule number is typically reserved for regular scheduled trains, while peak hour operations are not a stipulation for all extra trains; they can run at various times based on operational needs.