If a train stops less than one engine length beyond an interlocking signal, what must occur before it can move?

When a train stops less than one engine length beyond an interlocking signal, it is crucial for operational safety that the train receives permission from the Dispatcher or Operator before it can move. This requirement ensures that the train is cleared to proceed, as there may be other trains within the same block or conflicting movements in the vicinity.

This protocol helps maintain safe distances between trains and prevent potential collisions. The Dispatcher or Operator has the necessary situational awareness of track conditions and any other movements that might affect the train's path, which is why this communication is essential.

Other options do not provide the necessary safety checks or procedures that are critical in this scenario. For instance, simply alerting all crew members or allowing the train to move after a set time, such as a minute, does not ensure that the track is clear and safe. Similarly, waiting for another train to clear is not always applicable or practical, as operations may need to continue based on real-time assessments from the Dispatcher or Operator. Thus, obtaining permission is the most comprehensive requirement for ensuring safety in this situation.