Final answer:
Train crews need to know the running time and scheduled times to ensure efficient train operations and prevent delays or collisions.
Step-by-step explanation:
The most logical reason for train crews to have knowledge of the running time and scheduled time due at principal points and terminals is to ensure efficient train operations. By knowing the running time and scheduled arrival times, train crews can make adjustments and coordinate with other trains to prevent delays or collisions. For example, if a train is running late, the crew can communicate with the control center to make necessary arrangements, such as changing the platform or giving priority to another train.