Train Crash: Signals could be key to cause of fatal collision

Speculation on the cause of Britain's worst rail disaster in nearly 10 years will centre on why the freight train was in the path of the high speed train travelling at close to 90mph.

All the eye-witness accounts and early reports suggest that the empty freight train was crossing the track blocking the line where the high speed train was travelling, and that the HST hit the eighth wagon out of the 20 on the freight train.

The accident was similar to Britain's last fatal train accident at Watford in August 1996, when a commuter train travelling from London smashed into an empty train that was crossing its path in the other direction. The subsequent inquiry revealed that the driver of the commuter train had ignored a red signal and smashed into the empty coaching stock.

There will be immediate suggestions that the same scenario took place yesterday. The freight train clearly "had the road" - in other words it was on the right tracks. Otherwise it would have been derailed because the points would have been set against its route.

The HST hit the freight train with a glancing blow because of the geometry of the crossover and the leading power car was relatively undamaged. But then the next three carriages, carrying the first-class passengers, smashed into various parts of the freight train causing the resulting carnage.

The extent of the damage suggests that the passenger train was travelling at around its permitted speed, between 60 and 90mph. Therefore, the investigators will consider two main possibilities - either the driver of the HST went through a red, or there were signalling faults, like in the Clapham disaster.

On the railways, red signals are always preceded by a double yellow and a yellow signal. Each time a driver goes through these, he receives both a visual warning on his display panel and a hooter sounds in the cab. Each time, the warning has to be cancelled by the driver.

If the driver did ignore all these warnings, it may have been because he was following another train going at the same speed ahead of him and therefore "was running the signals". In other words, he was travelling fast through a succession of yellow signals and then suddenly came upon a red but noticed it too late.

The inquiry team will want to look at several other questions:

Why was the freight train allowed to pass in front of the HST, while normally it would not have been allowed to pass?

If the HST did not go through the red, and the signal for it was green, why was the freight train still on the fast track? Did works in the area, for the Heathrow Express line being constructed, cause the signals to fail?

Railtrack was not prepared to speculate on the cause of the crash. "The incident occurred a quarter of a mile east of Southall station where the passenger train travelling towards London struck the side of the freight train," said a spokesman.

Piecing together the events will be the job of the Health and Safety Executive's Railways Inspectorate. It will also be looking at the possibility of signal failure. Joginder Bhatia, who was one of the first on the scene, said that one of the rescuers told him a signal had apparently failed on the line, adding: "The [HST] train was given a green light when the other train had still not cleared the track."

One former British Rail safety manager pointed out that lives might have been saved had the railways installed automatic train protection (ATP) systems. Peter Rayner, who led safety investigations for BR, pointed out that the systems , which had been recommended after the Clapham train inquiry, had been dropped because of cost considerations.

Ironically, the line was being used as test for ATPs but Railtrack last night was unable to say last night whether the trains were fitted with them.

Roger Ford, editor of Rail Privatisation News, said that this "side-swipe" type of accident was the worst kind of railway disaster. "Unlike a head to head collision where the energy is absorbed by the structure, this type of glancing hit produces the most damage."

However, Mr Ford said the passengers were fortunate that they were in relatively modern Mark 3 coaches. He said: "These offer very good protection to people travelling in them. Unlike older coaches their body design stops them from crumpling and concertina-ing."