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
London Underground infrastructure London Overground – at New Cross and New Cross Gate. Of the boroughs that the Underground passes through, Hackney is served solely by Manor House station on the Piccadilly line in the very north-western edge of the borough. For the most part however some of the tube lines like the Central line skirt around the edge of the Hackney rather than going through it. Greenwich borough was unserved until North Greenwich station opened on the Jubilee line extension in 1999. The lines are electrified with a four-rail DC system: a conductor rail between the rails is energised at −210 V