What is signal failure and why does it cause train delays?

Signal failures are almost as old as the railway itself – with the first primitive wayside signalling systems being introduced in 1832.

These days signalling relies on a combination of movable sections of track (known as points), track circuits that detect the position of the train and the signals themselves, which look like traffic lights positioned above or beside the track.

These three elements must be routed via cables to a signalling centre where each signal change must be co-ordinated. With such a complex system, the reasons for a signal failure could be anything from power outages and circuit failures to track points freezing or the increasingly widespread problem of stolen cables and vandalism.

Identifying the cause of the problem often takes longer than fixing it.

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