What defines a block in railway terminology?

A block in railway terminology is defined as a length of track governed by block limit signals or cab signals. This concept is essential for maintaining safe train operations by ensuring that trains do not occupy the same section of track at the same time, which helps prevent collisions. The system of blocks is crucial for the efficient dispatching and routing of trains, as it allows for segmenting the track into manageable areas where signals can control train movements effectively.

Block limit signals indicate the limits of a block, informing train operators when it is safe to proceed or when they must stop. Cab signals work similarly but deliver information directly to the locomotive's cab, providing real-time updates to the engineer about the status of the blocks ahead. This integration of signals and track sections is vital for overall safety and coordination within the rail network, ensuring that trains operate in a systematic and predictable manner.

While other terms in the options describe various aspects of railway operations, they do not specifically capture the definition and function of a block as it pertains to train safety and signaling.