Formal Inquiry: Derailment of train 1T60, 1245 hrs Kings Cross to Kings Lynn at Potters Bar on 10 May 2002 - Final Report

"The derailment of 1T60, 1245 hrs Kings Cross to Kings Lynn, was caused by the closure of the RH switch rail of 2182A points against its stock rail as the third vehicle of the train was passing over the points. This occurred with the LH switch rail closed and locked against its stock rail. As a result, a number of wheelsets met both switch rails simultaneously, and were then squeezed into derailment.

The RH switch rail of the points closed against its stock rail because the lock stretcher bar, which had fractured at its RH end, became detached from its RH insulating channel at a time when the switch rail was not restrained by the front or rear stretcher bars. As a result, the switch rail became completely unrestrained, and its natural elasticity caused it to straighten, and in doing so to move towards its stock rail.

The Panel has not established with certainty exactly how the nuts on the front and rear stretcher bars were configured before or after the points were attended on 1 May 2002, and was therefore unable to say precisely how 2182A points came to be in the condition in which they were found on 10 May 2002.

However, the method in common use before the accident by maintenance and renewal staff for positioning and securing the nuts in adjustable stretcher bar assemblies has been shown to contribute to the loosening of these assemblies, and could have been a factor in this case. This method had emerged because managers within the industry did not understand the importance of adopting a tightening procedure that would fulfil the requirements of the design of adjustable stretcher bars. This had occurred because, from the first introduction of these assemblies, the mechanics of the system used to secure the nuts were not fully understood by those responsible for installing and maintaining the assemblies.

The staff interviewed by the Panel had not been trained specifically in the assembly and maintenance of adjustable stretcher bars, because no relevant training programme had been developed or delivered. The lack of a training programme was the result of the failure to produce a procedure for the installation of adjustable stretcher bar assemblies, despite the stated intention in 1993 to do so."

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