In rail transport, a derailment occurs when a rail vehicle such as a train comes off its rails. Although many derailments are minor, all result in temporary disruption of the proper operation of the railway system and they are a potentially serious hazard. A derailment of a train can be caused by a collision with another object, an operational error (such as excessive speed through a curve), the mechanical failure of tracks (such as broken rails), or the mechanical failure of the wheels, among other causes. In emergency situations, deliberate derailment with derails or catch points is sometimes used to prevent a more serious accident. History The first recorded train derailment in history is known as the Hightstown Rail Accident in New Jersey that occurred on 8 November 1833. The train was traveling between Hightstown and Spotswood New Jersey and derailed after an axle broke on one of the carriages as a result of a journal box catching fire. The derailment resulted in one casualty and twenty-three injuries, and it was recorded that both New York railroad magnate Cornelius Vanderbilt and former U.S president John Quincy Adams were on the train as it took place, in which Adams wrote about the event in his journal. During the 19th century derailments were commonplace, but progressively improved safety measures have resulted in a stable lower level of such incidents. In the United States, derailments have dropped dramatically since 1980 from over 3,000 annually (1980) to 1,000 or so in 1986, to about 500 in 2010. Causes Derailments result from one or more of a number of distinct causes; these may be classified as: the primary mechanical failure of a track component (for example broken rails, gauge spread due to sleeper (tie) failure) the primary mechanical failure of a component of the running gear of a vehicle (for example axlebox failure, wheel breakage) a fault in the geometry of the track components or the running gear that results in a quasi-static failure in running (for example rail climbing due to excessive wear of wheels or rails, earthworks slip) a dynamic effect of the track-vehicle interaction (for example extreme hunting, vertical bounce, track shift under a train, excessive speed) improper operation of points, or improper observance of signals protecting them (signal errors) as a secondary event following collision with other trains, road vehicles, or other obstructions (level crossing collisions, obstructions on the line) train