What does a block refer to in railway terminology?

In railway terminology, a block refers to a length of track that is controlled by signals or restrictions, making it crucial for the safe operation and dispatch of trains. The primary purpose of a block system is to prevent collisions by ensuring that only one train occupies a block at any given time. When a block is occupied, signals will indicate to other trains that they should stop or wait until the block becomes available. This system enhances safety and efficiency by managing train movements based on the occupancy of the track.

The other options describe different railway concepts but do not accurately define what a block is. A track with revolving signals is related to signal systems but does not capture the full definition of a block. A designated area for unloading passengers refers to a station or platform area, while a maintenance zone is specific to track inspection and repairs, neither of which pertains to the concept of a block in terms of signal governance and train operations.