The New Zealand Railways Magazine, Volume 9, Issue 2 (May 1, 1934.)
Modern Signalling Methods
Modern Signalling Methods.
On the route of the “Flying Scotsman” between London and Scotland, the L. and N.E. Railway has just opened an interesting new signal control tower at Thirsk. This new signalling centre is the last word in modernity. The tower controls 4 1/2 geographical miles of track, and takes the place of five signal-boxes. One man at an electrically controlled switchboard controls the whole of the working over this distance. Altogether 28 1/2 geographical miles of track have been resignalled with colour lights and the control of the signals and poweroperated points is carried out by means of small thumb switches.
The electrical signalling system introduced at Thirsk is of the colour light searchlight type, with alternating current track circuit. The signal indications given include red for “stop,” yellow “proceed with caution,” two yellows “proceed but prepare to pass the next signal-box at restricted speed,” and green “all clear.” Even in the brightest sunlight, the signals are clear for a distance of 1,000 yards, and the installation entirely eliminates detonator working during foggy weather or falling snow. An interesting feature of the double yellow signal is that it advises the driver when he is being diverted off the main track page 12 page 13 on to a parallel running line. Alternating current track circuits of the type installed mark an entirely new departure so far as Britain is concerned.