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
Romford–Upminster line saw an end to years of speculation about its future. There is only one intermediate station, at Emerson Park. At the connection west of the station to the main line was severed in 1968. The branch has just one signal, on approach to Romford. There were plans to link the line from platform six at Upminster to the reception tracks of the London Underground depot there. This would have allowed the transfer of London Underground D78 Stock units onto the main line to be hauled away by diesel locomotive for refurbishment at the Ilford depot. These plans were scrapped when