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GWR Route: Banbury to Wolverhampton
Olton Station: gwro4023
An extract on Track Circuits from the Great Western
Railway - Synopsis of Course of Instruction on the subject of Safe Working of
Railways and the Appliances used in connection therewith for the use of
Students of the Signalling Classes (dated October 1933).
Track Circuits were initially introduced to inform Signalmen
when trains were present on lines that were out of sight of the Signal Box.
Their presence also saved the need for Enginemen to go to the Signal Box to
inform the Signalman of the presence of their train as required by Rule 55.
These advantages had long been recognised as necessary at large stations like
Snow Hill where detection of trains was initially achieve by mechanical means
(i.e. fouling bars - see gwrbsh1131a), with these
later being replaced with DC electric track circuits. The introduction of locks
prevented Stop Signals in the rear of a track circuit being inadvertently
cleared, so providing an additional Safety feature. This greatly increased the
number of track circuits and the Safety advantages were further extended by
introduction of circuitry, which prevented operation of Block Instruments. The
next development was the use of track circuits to control intermediate block
signalling (IBS) as described on page 66 of the attached document.
Semi-automatic signalling was used at several locations on
the Great Western Railway. The first installation was in 1907 between
Pangbourne and Goring, allowing the Signal Box at Basildon to be dispensed
with. In Warwickshire the first use of semi-automatic signalling was in 1933 on
the Birmingham Main Line between Acocks Green and Solihull. The newly
quadrupled lines were provided with IBS allowing the Signal Box at Olton to be
dispensed with (see 'gwro4024').
Robert Ferris
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