Sunday, 1 March 2015

Railway signals

When I was nowt but a lad I liked watching trains.  A short walk to line side would be rewarded with a succession of goods trains interspersed with passenger trains to far-away destinations  London, Manchester, Glasgow, Edinburgh, Newcastle, Bristol,  Leeds to name but a few.  Acquisition of a map of  railway lines soon provided me with a detailed knowledge of the location of towns and cities.  Then came the Beeching Report, followed by the axing of  many lines, although one large system, the Midland and Great Northern Joint, closed in 1959.

The trains and steam locomotives fascinated me: Streaks, Jubilees, Crabs, A3s, Black 5s, 8Fs, Compounds, Directors...the list could go on and on.  What I was not aware of then was the thermal inefficiency of steam locomotives and the waste associated with their operation.

To keep the show on the road railways use signals to keep trains apart.  When I was a youngster railways used for the most part semaphore signals operated from signal boxes. A box kept in touch with adjoining boxes by bell codes.  Some boxes were very busy with trains passing every few minutes, but others might see only one or two trains an hour.  These signal boxes were known as mechanical boxes.  The signalman operated signals by pulling levers attached to wires which ran to the signal post.  Signals were lit at night by oil lamps.  Foggy weather obscured the signals and the lights, so on foggy days a man would be posted at signals to assist drivers to identify signals and decide if it was safe to proceed.

The advent of colour light signals obviated the need for fog men, although it did not stop all accidents caused by lack of signal sighting.  The Lewisham crash was caused by the failure of a driver and fireman to see two colour light signals.

The railway is now mostly operated by colour light signals from boxes which cover many miles of track.  Far more efficient.

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