A buffer stop, bumper, bumping post, bumper block or stopblock (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, on 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 of British origin, since railways in Great Britain principally use buffer-and-screw couplings between vehicles. Types Several different types of buffer stop have been developed. They differ depending on the type of coupler used and on the intended application. Buffer stops with anticlimbers. These are particularly important for passenger railway applications, because the anticlimbers reduce the likelihood of telescoping of the railroad cars during a head-on impact. Buffer stops for a knuckle coupler or an SA3 coupler (centrally positioned between the two rails) 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 City Line train powered past the bumper block at Moorgate station in 1975 on the London Underground system. Energy-absorbing Largely because of its mass, a train transfers an enormous amount of kinetic energy in a collision with a buffer stop. Rigid buffers can safely cope only 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. Examples Raja Trains Depot in Tehran Stopping speed: Stopping distance: . Wheel stop Wheel stops or car stops are used to stop small numbers of light vehicles at the end of level storage tracks or to chock individual railroad cars on shallow grades. Gallery Examples of accidents 22 October 1895 – Gare Montparnasse, Paris, France – An express train overran the buffer stop and fell into the street below. 1902 – Frankfurt am Main, Germany – Serious buffer stop collision inspires development of Rawie range of energy-absorbing buffer stops. 27 July 1903 –