Case Studies - Crashworthiness of Mark 1 Rolling Stock

Mark 1 railway rolling stock was introduced on the UK rail network in the early 1950s. Its design is based on a very substantial underframe to which is attached a lighter constructed body.

In 1988 a collision occurred at Clapham involving three Mark 1 trains. During the collision one carriage underframe overrode another, penetrating the upper body, causing many fatalities and serious injuries.

One recommendation of Lord Justice Hidden's report on the accident pointed to the need for the crashworthiness of the rolling stock to be improved. In other words, the construction should be improved so that the energy of a collision is absorbed by the structure in a controlled way to minimise injuries to passengers.

HSE asked HSL to review Mark 1 vehicle crashworthiness. The HSL review revealed that, following the Clapham accident, two options had been put forward for improvement. One was to replace the complete carriage end, the other was to withdraw the rolling stock from service and replace it with more modern crashworthy designs. HSL's report concluded that it might be possible to improve crashworthiness more cost effectively by modifying the existing structure.

The modifications proposed were:

• to introduce carriage couplers which would break away on impact;
• to introduce cup and cone interlocking devices to engage on impact to prevent override; and
• to modify parts of the carriage underframe to obtain controlled energy absorption in the event of a crash.

In order to test these recommendations, a research programme was set up involving HSE, Halcrow Transmark as project managers, W S Atkins for their finite element modelling expertise and HSL for its large-scale testing and experimental capability.

Static and dynamic tests were carried out showing that individual components behaved as predicted. In addition, a full-scale dynamic underframe test showed that all the components worked in unison.

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