Northeast Operating Rules Advisory Committee (NORAC) 300 Practice Test

A Block is a defined length of track with defined limits on which train movements are governed by block signals, cab signals, or Form D. This means the track section itself has clear boundaries and its movements are controlled by the signaling system or dispatcher authority for that segment. The block protects train separation by making entry and movement within that section conditional on the applicable signal or Form D clearance.

Why this is the best description: it captures the essential idea that a block is a specific portion of track with defined limits whose movements are controlled to ensure safe operation. The other options describe signaling devices, worker indicators, or the dispatch office, not the defined section of track that constitutes a block.