Signal Passed At Danger
In railway terminology, a Signal Passed At Danger or SPAD describes an event where a train has run beyond its allocated signal block, as indicated by a lineside signal showing red. It is a term primarily used within the British Railway Industry although can be applied worldwide. Most SPADs occur at low speed where braking distance has been misjudged, and the train can subsequently be stopped within a safety overlap area either by the driver or by an automatic application of the emergency brakes by a safety system such as TPWS. In some situations where a signal cannot be seen due to obstruction sufficient braking may not have been achieved, and the train will continue to run a significant distance beyond the danger light. Such an incident was determined as the main cause of the Ladbroke Grove rail crash at a time when TPWS was not in operation.
Accidents involving SPADs
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