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 S7 and S8 Stock The DMIs show destination and line, and can display other messages such as safety notices. There are also DMIs on the exterior, with text alternating between destination and line, and on S8 stock the type of service, i.e. fast, semi-fast or all stations. Another new feature is that to prevent accidental pressing of emergency alarms there are flaps over the alarm buttons where the wheelchair spaces are. The air-conditioning system, the first on London Underground trains, is supplied by Mitsubishi and has two circuits so that if one fails there is still 50% capacity. Through gangways from car to car