The first underground railway - was opened January 10, 1863 in London. Its length amounted to around seven kilometers and connected stations Bishops Road and Farringdon Street. Originally steam traction, unsuitable for underground operations requiring a powerful ventilation system, later underwent electrification. Railcars were energized by collectors from another side rails, which is a principle that is at the underground railway is still used today. In place of the former station Bishops Road today is significant to London Paddington. Trains contemporary London Underground runs on twelve color-coded routes. They exist as underground, saved about five meters below ground level and underground, which are located at a depth of about two dozen meters. Trains on both routes at first sight differ in height, which is due to the smaller diameter underground tunnels. On underfloor route follows almost one hundred kilometers long track surface.