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In a railway accident, telescoping occurs when the underframe of one vehicle overrides that of another, and smashes through the second vehicle's body. The term is derived from the resulting appearance of the two vehicle bodies: the body of one vehicle may appear to be slid inside the other like the tubes of a collapsible telescope - the body sides, roof and underframe of the latter vehicle being forced apart from each other.
Telescoping often results in heavy fatalities if the cars telescoped are fully occupied. The car riding on top will often be destroyed by the structure of the car below (physics of the incident can often reverse this damage), leaving very little survivable space. The chances of telescoping can be reduced by use of anticlimbers and crash energy management (CEM) structural systems.
Accidents where telescoping occurred are numerous and include:
- 1972 Chicago commuter rail crash
- 1957 Lewisham rail crash
- 1975 Moorgate tube crash
- 1981 Seer Green rail crash
- 2008 Chatsworth train collision
- June 2009 Washington Metro train collision
- 2012 Buenos Aires rail disaster
To reduce the chance of telescoping, rail and tramway vehicles are often provided with an anticlimber: a horizontally ridged plate at the end of the chassis, which in a collision will engage with the anticlimber on the next car.
- Solomon, Brian (2001). The Heritage of North American Steam Railroads. London: Amber Books. p. 101. ISBN 1-897884-75-3.
- Einat Rozenwasser (25 February 2012). "Un operativo que resultó eficaz pero que ahora revela fallas". Clarín. Retrieved 25 February 2012.(Spanish)