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
Central line (London Underground) Ilford carriage depot. The extension transferred to London Underground management in 1949, when Epping began to be served by Central line trains. The single line to Ongar was served by a steam autotrain operated by British Rail (BR) until 1957, when the line was electrified. BR trains accessed the line via a link from Temple Mills East to Leyton. The Central line stations east of Stratford kept their goods service for a time, being worked from Temple Mills, with the Hainault loop stations served via Woodford. The BR line south of Newbury Park closed in 1956 and Hainault loop stations