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
Urban rail in the United Kingdom example Amersham and , but some stations much closer to the Greater London boundary, like and , are not in any zone. London has an integrated ticketing system via the Travelcard or Oyster Card for buses, Docklands Light Railway, suburban rail, tram, Underground and Overground. Unlike cities like Liverpool/Merseyside, Sydney and Paris, several operators provide suburban rail services. Most stations are served at least every 20 minutes, with many stations and routes having four, six or more trains per hour. c2c runs from London Fenchurch Street through east London via Basildon (or Grays and Tilbury) to Southend Central and Shoeburyness,