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X Signal

An X signal is the last automatic signal before a controlled area and must be treated by the driver as if it is a semi-automatic signal.  This example shows a Track Renewal X signal, which is used where longer term engineering works take place and a crossover has been installed to permit movement of trains on what is normally a straight line.  Since local signals will be automatic, it is necessary to protect the crossover during use.  To that end, the protecting signal is changed, its A replaced by a TR to denote track renewal and an X to denote that it must not be passed at danger without authority. The signal will usually have an illuminated A sign for use during traffic hours, during which time the emergency crossover will not normally be used and train operators can revert to treating the signal as automatic.  Photo by Tube Troll.

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