Railway signal

A device that conveys instructions or information to train operators or railway control systems. Signals help regulate train movements and maintain safe separation on railway lines.

Railway signal aspect: The visual indication displayed by a railway signal, conveying a defined instruction or warning. An aspect is the visible message operators interpret when responding to a signal.
Railway block signalling: A method of controlling train movements by dividing track into sections and limiting occupancy within them. It is the operating principle behind many lineside signal systems.
Railway colour-light signal: A railway signal that conveys indications using colored lights. This widely used form presents signal aspects clearly at a distance.
Fixed-block signalling: A signalling method that divides track into fixed sections and restricts train entry according to section occupancy. It contrasts with systems that calculate separation continuously rather than by fixed sections.
Railway signalling failure: A malfunction or incorrect operation of equipment or procedures used to control railway movements. A failure can cause a signal to convey unsafe information or lose its protective function.
Railway signalling block: A section of railway track whose occupancy is managed to prevent conflicting train movements. Block occupancy determines whether a signal can authorize a train to proceed.
Railway signal indication: A message conveyed by a railway signal, such as stop, proceed, or proceed with a restriction. Indications are interpreted according to the railway's operating rules.
Semaphore railway signal: A railway signal that conveys an indication through the position of a movable arm. Mechanical arms provided a prominent visual language before color-light systems spread.
Moving-block signalling: A train-control method that maintains safe separation using continuously updated positions and braking limits instead of fixed track sections. It can reduce dependence on conventional block boundaries and lineside signals.
Hixon rail crash: A 1968 collision in England between a train and a heavy road transporter on a level crossing. The crash exposed limitations in warning arrangements and railway operating procedures.

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