A safety feature designed to keep trains stable during a derailment actually contributed to the Selby disaster.
Memories of the Selby crash were revived this week when a freight train hit an articulated lorry cab that had ploughed off a bridge in the wet near Ardleigh in Essex.
Outside the public domain
In the same week it has emerged that an investigation by AEA Technology on behalf of the Selby inquiry found that retaining straps, fitted to prevent bogies veering off in a different direction from the rest of the train during accidents, actually helped pull the bogies off the rails when the GNER 225 hit a Land Rover at Great Heck last year.
However, this fact was not included in the Health and Safety Executive report into the crash and until today it has remained outside the public domain.
The AEA Technology investigation found that when the train hit the vehicle it ran over the Land Rover’s engine block, causing the train’s body to lift.
As the body lifted the suspension springs extended, reducing the force holding the wheels to the track until only the weight of the bogies was keeping them on the rail. Bogies weigh between five and six tonnes, so their own mass could have helped to keep the wheels on the track, while the space created between the bogies and the body allowed the train to simply travel over the engine.
Tragically, though, at this point the retaining straps tightened, pulling the wheels upwards and off the rails, according to Richard Gostling, technical director of the Railway Industry Association. ‘Not only was the force not encouraging the bogies to stay on the track, the weight of the body was now actually encouraging them to go upwards,’ said Gostling.
‘It was a monumental misfortune. The chances of a train hitting something and derailing are actually very small.’
Retaining straps, a standard design feature, were developed to stabilise trains in the case of a derailment. They attach the body of a train to its bogies, and are long enough to allow a certain degree of flexibility, so wheels are not lifted off the track when a train bounces over a slight bump. But in a derailment they tighten to prevent the bogies running too far from the direction of travel, which could destabilise the train and cause it to flip on to its side.
No comment from HSE
‘People within the rail industry had introduced these [the retaining straps] to make trains safer, but in this particular case it made things worse,’ said Gostling.
Many are likely to question whether the design of trains should be changed to prevent a repeat of the disaster, and this week The Engineer calls on the HSE to reopen its investigation into the Selby crash and explain why the AEA Technology findings were not included in its verdict of the disaster.
However, the HSE said this week that it was not available for comment.
Meanwhile, a spokesman for GNER said it would take into account any reports if they revealed that alterations or modifications to trains were required.
The controversy is also likely to revive concerns over the use of Driving Van Trailers on the East Coast main line. The GNER 225 was powered by a locomotive at the rear, with a lighter DVT at the front. With DVTs around one-third lighter than locomotives, there was less weight keeping it down when the train hit the Land Rover’s engine, said Gostling. ‘Obviously somewhere along the line this must have made a difference, but it seems unlikely it was the most significant factor.’