GNER locomotive was involved in Hatfield crash

The engine

In a bizarre twist of fate, the locomotive in yesterday's crash - engine 91023 - was also involved in the Hatfield disaster four months ago.

In a bizarre twist of fate, the locomotive in yesterday's crash - engine 91023 - was also involved in the Hatfield disaster four months ago.

The locomotive was powering the trains in both accidents - yet escaped serious damage itself. Experts said it was not a freakish coincidence because there were only 31 of the class 91 engines in service. They were introduced in 1988, having been specifically designed for the east coast route.

In October's Hatfield crash, the engine was pulling from the front when the rear of the train slipped off the rails. Yesterday it was pushing from the back, and it was almost the only part of the train left on the track. It appeared to be undamaged.

The carriages involved were also built in the 1980s specifically for the east coast route. The design is now outdated, yet the carriages withstood forces they were never intended to survive - and good engineering probably reduced the number of deaths, experts said.

"These carriages are made to last 40 years. They are very robust," said Nigel Harris, editor of Rail Magazine. "Before the 1950s, carriages were made out of timber and, if they had crashed like this, they would have been turned into matchwood.

"These are mark IVs and are a solid steel monocoque tube with windows cut out. They are solid and protective, and it is a tribute to them that not more people have been killed."

Crushing of the carriage is potentially the most dangerous effect of a rail crash because extricating victims from the wreckage becomes a complex, time-consuming task thatcan make treatable injuries such as internal bleeding life-threatening.

The steel carriages are designed to ensure that the body shell remains intact in a crash, with an integrated crumple zone to protect passengers. But although they can cope with an impact of up to 70mph, the train in the Selby crash is thought to have been travelling at 125mph.

If the carriage is not crushed in an impact, it absorbs less of the energy of the crash - which means that people inside will be thrown around more and will suffer broken limbs and other injuries.

That is still preferable to the alternative, said Pip Dunn, of Rail Magazine. "There may be the risk of banging your head, but you've got a better chance of survival," he said. "If you're in a car in a car crusher and it crunches down, you're dead. But if the car can't be crushed, you survive."

He praised the design of the carriages. "If you look at the way [the carriages] stood up to the impact - where there was a closing speed [between the two trains] of about 180 miles per hour - you had a carriage thrown into the air and landing on its end, and yet it didn't buckle. Compared with the Southall accident [in 1997], you can see that these carriages were much stronger than those."

However, another expert said there had been too little investment since privatisation to replace carriages which were only designed to withstand 70mph crashes.

Murray Hughes, editor of Railway Gazette, said: "The train will have had a crumple zone to protect passengers, and unlike older carriage designs, which had an under-frame and separate sides which could come apart, these are designed to keep the body shell intact, with a load-bearing roof, sides and floor. Hence the fact that pictures show the vehicles in the field as relatively intact."

The design also incorporates systems to stop the carriages smashing through each other. But Mr Hughes said: "It is very unreasonable to expect the carriages to stay intact at such a speed. They are designed to deal with a maximum impact of 60-70 mph.

"After Paddington and Southall, designers have been made aware of what happens at great speed, and these crashes have contributed to their knowledge of high-impact effects. There are still some of the oldest carriages in use, which are not due to be phased out until 2004."

Mr Hughes claimed that after the disasters at Southall and Paddington, carriage designers were aware that modifications to existing designs were needed to cope with higher speed collisions.

He said: "With investment, British Rail could have kept on modernising the service and making use of what they had found - but then privatisation came along."