London Underground at +420 V, giving a potential difference of 630 V. On the sections of line shared with mainline trains, such as the District line from East Putney to Wimbledon and Gunnersbury to Richmond, and the Bakerloo line north of Queen's Park, the centre rail is bonded to the running rails. The average speed on the Underground is 20.5 mph. Outside the tunnels of central London, many lines' trains tend to travel at over 40 mph in the suburban and countryside areas. The Metropolitan line can reach speeds of 62 mph. The London Underground was used by 1.379 billion passengers in
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,