For an underground system, the choice of traction method does not really exist since whatever experience may have been gained in the past with steam traction, modern standards of amenity require that railways operated wholly or largely in tunnel should be free from the fumes inevitably produced by steam or diesel operation. There is not, therefore, the same opportunity for economic studies of electrification compared with diesel operation to be made. For other compelling reasons, for example absolute limits on space and practical ones of cost, the necessity of using some form of rail pick-up system rather than overhead wire electrification is needed on underground lines. It must not be overlooked that tunnelling costs of main running tunnel vary very broadly with the square of the diameter of the tunnel, and unless any increase is used to improve the carrying capacity of the stock, provision of additional tunnel space just for overhead supply is generally uneconomical in short distance dense service operation, unless through running with other existing transport systems is to be envisaged. London Transport uses a 600 volt d.c. (nominal) 4th rail system. The reason for using four rather than three rails are somewhat complex and are adequately reviewed elsewhere.

  • Corporate Authors:

    Institution of Electrical Engineers

    Savoy Place
    London WC2R 0BL, NY  England  10016-5997
  • Authors:
    • Manser, A W
  • Publication Date: 1968

Media Info

  • Features: Figures; References; Tables;
  • Pagination: 25 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00054355
  • Record Type: Publication
  • Source Agency: Institution of Electrical Engineers
  • Report/Paper Numbers: #50 Conf Pub
  • Files: TRIS
  • Created Date: Jun 10 1974 12:00AM