Circle line (London Underground) with the other London Underground sub-surface lines: the Hammersmith & City line from Hammersmith to just before Aldgate; the Metropolitan line from Baker Street to Aldgate; and the District line from Tower Hill station to Edgware Road station. The line is electrified with a four-rail DC system: a central conductor rail is energised at and a rail outside the running rail at , giving a potential difference of . The running rails are not electrified. Much of the double track railway from the Hammersmith terminus to Westbourne Park station is on a high brick viaduct. East of Westbourne Park the
West Croydon to Wimbledon Line West Croydon to Wimbledon Line The West Croydon to Wimbledon Line was a railway line in south London. It was built by the Wimbledon and Croydon Railway (W&CR) over part of the trackbed of the Surrey Iron Railway. It opened on 22 October 1855 connecting the South West Main Line of the London and South Western Railway (LSWR) to the London Brighton and South Coast Railway (LB&SCR). National Rail services ceased and the line eventually shut down in 1997 for it to be changed over into a new route for the Tramlink network which eventually rolled into passenger service in