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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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