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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