What must a dispatcher verify before allowing a train to reverse in the same block?

Verifying that the track is clear of opposing movements is crucial for ensuring the safety of train operations. Before allowing a train to reverse in the same block, the dispatcher must ensure there are no other trains or conflicting movements in that section of track. This is to prevent potential collisions and ensure that the reversal can be performed safely.

The other options, while important in different contexts, do not directly address the immediate safety concern of opposing movements on the same track. Monitoring fuel levels, informing crew members, and managing train speeds are operational considerations, but they do not supersede the necessity of ensuring that the track is clear for safe movements. Safety protocols prioritize preventing accidents, which is why confirming the absence of opposing traffic is the critical step in this scenario.