Railway Signalling on London Transport

Abstract

ACCORDING to a paper read recently in London by R. Dell before the Institution of Electrical Engineers, the power-signalling installation on the railways of the London Passenger Transport Board now covers 160 miles of double track. There are 3,281 stop signals, 2,726 of which are fitted with train-stops. Track circuits number 4,347 and there are 1,326 pairs of points. Although automatic signals are used wherever possible, 112 signal cabins are in use at junctions or connexions in the track layout. The passenger-train car-miles run each year total approximately 159,150,000. Power signalling has been in use practically throughout the system since it was electrified. The electrification of the District Line and the installation of power signalling commenced in 1904 and was completed by the end of 1905. The London Electric Tube Lines were equipped with power signalling from the start—the Bakerloo and the Piccadilly Lines in 1906 and the Hampstead Line in 1907. The Central London Railway was converted to power signalling in 1913 and the City and South London Railway in 1919. Except for these last two installations, the whole of the signalling system was originally operated on D.C. and track circuits were of the D.C. type with polarized relays in order to avoid improper operation by stray current from the traction system.