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 1973 Stock London Underground 1973 Stock The London Underground 1973 Stock is a type of rolling stock used on the Piccadilly line of the London Underground. It was introduced into service in 1975 with the extension of the line to Hatton Cross, followed by a further extension to Heathrow Central in 1977. The trains were built by Metro-Cammell between 1974 and 1977, and were refurbished by Bombardier Transportation between 1996 and 2001. They are some of the oldest trains running on the Underground, second only to the 1972 Stock running on the Bakerloo line. In the early 1970s London Transport placed an