What is an absolute signal?

An absolute signal refers to a specific type of block signal that conveys clear information to train operators about the status of a track section. In this context, it is identified as a block signal without a number plate. The absence of a number plate generally indicates that the signal is conveying absolute authority — essentially meaning that the train must stop if the signal is displaying restrictive aspects. This ensures safety by preventing trains from entering sections of track that are occupied or unsafe to traverse.

The other options do not accurately represent the definition and purpose of an absolute signal. A signal with a number plate typically provides information about the milepost of the location, which is not the primary function of an absolute signal. A special warning signal might indicate caution but does not provide the same absolute authority for stopping. Lastly, a signal indicating the end of a track serves a distinctly different purpose by alerting train crews to the termination of a rail line, rather than conveying stop or proceed instructions based on track occupancy.