When can a train make a reverse movement within the same block, according to dispatcher protocol?

A train can make a reverse movement within the same block when it is preceded by a crew member who is able to stop any opposing movement. This is crucial for safety, as the crew member acts as an assurance that if there is any unexpected movement, they can intervene and mitigate risks. The presence of a crew member in this scenario provides an additional layer of safety and oversight.

It is important to note that while the other scenarios present conditions that may be related to train movements, they do not guarantee the necessary safety net as option C does. For example, blocks under investigation or verbal permission from a dispatcher may not account for the immediate risk of opposing movements. Likewise, even if all signals are green, which indicates that the track is clear, that does not provide the specific oversight needed to reverse into a potentially hazardous situation. Therefore, ensuring that a qualified crew member is in place to halt any opposing movement is key to safely conducting reverse movements in the same block.