Why is it essential for train crews to know running time and scheduled times at principal points?

Understanding running time and scheduled times at principal points is crucial for train crews primarily because it enables them to effectively communicate with passengers regarding arrival and departure times. When crew members are aware of the schedule, they can provide accurate information to passengers, enhancing customer service and overall travel experience. Being able to answer questions about timing helps manage passenger expectations and improves the reliability perception of the service.

While the other options present relevant objectives, none directly matches the core importance of communication regarding scheduled and running times. For instance, while managing crew shifts and coordinating with transport services are important operational aspects, these do not prioritize the immediate informational needs of passengers as effectively as keeping them informed about schedule adherence. Running ahead of schedule could be advantageous, but it is not a primary reason for understanding these times; it is more about maintaining the integrity of adherence to the set timetable. Thus, the ability to answer passengers' questions accurately stands out as the most essential reason.