This buffer stop is designed to move up to 7 metres (23 ft) to slow down a 850 tonnes (840 long tons; 940 short tons) passenger train from 15 km/h (9.3 mph) without damaging the train or injuring passengers.
A buffer stop or bumper (US) is a device to prevent railway vehicles from going past the end of a physical section of track.
The design of the buffer stop is dependent in part upon the kind of couplings that the railway uses, since the coupling gear is the first part of the vehicle that the buffer stop touches. The term "buffer stop" is itself of British origin, railways in Great Britain principally using buffer-and-screw couplings between vehicles.
Buffer stops with traditional "buffers" on either side
Hydraulic buffer stops
Friction buffer stops (bolted down to the rail)
If there is extra room behind the bumper block, there is usually a sand or ballast drag that is designed to further retard a runaway train. One such accident occurred when a Northern Line train powered past the bumper block at Moorgate station in 1975 on the London Underground system.
Due to its mass, a train transfers an enormous amount of kinetic energy in a collision with a buffer stop. Rigid buffers can only safely cope with very low-speed impacts (i.e., nearly stationary). To improve stopping performance, a way of dissipating this energy is needed, through compression or friction. Following a buffer stop accident at Frankfurt-am-Main in 1902, the Rawie company developed a large range of energy-absorbing buffer stops. Similar hydraulic buffer stops were developed by Ransomes & Rapier in the UK.
When it is desired to slow or stop moving trains, without erecting a solid buffer stop, dowty retarders may be employed. They press upwards against the wheels, and may optionally be turned off as required.
4 April 1901 – at the Top Points of the Lithgow Zig Zag, a train lost control on the 1 in 42 (2.381%) gradient and failed to stop at the buffer stops, coming to rest overhanging Ida Falls Gully, with an immediate 200 ft (61 m) drop in front of the engine.
1902 – Frankfurt am Main, Germany – Serious buffer stop collision inspires development of Rawie range of energy-absorbing buffer stops.
28 February 1975 – Moorgate Underground rail crash – 43 killed, 74 injured – buffer stop collision made far worse by small size "tube" train running into large dimensioned dead-end tunnel beyond. The tunnel could accommodate full-size surface stock thus permitting the smaller train to concertina inside the tunnel.
13 April 1978 – Budapest, Hungary – commuter train overruns a buffer stop owing to brake failure and crashes into the station building. 16 killed, 25 injured.
8 November 1986 – Hua Lamphong, Bangkok, Thailand – 5 killed, 7 injured – buffer stop collision made by an unmanned train at a speed of 50 km/h (31 mph).
26 October 2006 – Kuala Lumpur, Malaysia – a Star LRT train goes through buffer stops at the end of a stabling area (turnback perhaps) and ends up dangling over street. The train appears to have been empty of passengers.
21 December 2009 – Zagreb, Croatia – commuter train number 5100 from Sisak Caprag crashes into the platform bumper. The cause was antifreeze fluid in the locomotive's braking system which had frozen because of the extremely low outside temperature (−22 °C or −7.6 °F). Luckily, the speed of the train was only between 15 and 20 km/h (9.3 and 12.4 mph). 60 people from the train (including train's engineer) were injured, 7 of them seriously. There were no injuries among people on the platform. The engineer leaned out of the cab window to warn people on the platform that his brakes had failed and that the train would crash at the end of the platform.
25 July 2010 – Stavoren railway station, the Netherlands – A maintenance train collided with a buffer stop at the single-track terminus station. The train rammed a small shop, passed through it and stopped at the square behind it. Only two people were injured, out of four people on the train. The accident happened late at night, when passenger services had already finished. The cause is being investigated.
15 January 2013 – Saltsjöbaden, Sweden – A cleaning lady accidentally set a four-car EMU commuter train in motion while cleaning it at the Neglinge depot. It reached 80 km/h and demolished a buffer stop at Saltsjöbaden station before crashing into a small apartment block about 25 m beyond the end of the track, badly injuring the cleaning lady.
31 January 2013 - Brisbane, Australia - A train failed to stop at the end of the line at Cleveland railway station. The train overshot the buffer stop and ran into station building. A number of people were treated for minor injuries.