Is our track record being derailed?

And less than a fortnight after passengers and rail staff stood in silence to mark the first anniversary of the Ladbroke Grove crash which claimed 31 lives, attention is again being focused on safety on the trains.

While investigators are anxious not to speculate on why the train was derailed until their inquiries are complete, experts highlighted three possible causes of the tragedy.

"Either something was left on or near the line, there was something wrong with the line itself or there was a problem with the train," says Anthony Smith, national director of the Rail Passengers Council.

"Rail accidents are so rare it is difficult to say if one is more likely but the most catastrophic incidents are usually caused by a combination of circumstances.

"It is very rare you get one thing that goes wrong in an accident and normally there are failsafes in place to stop things happening. It is usually that A did something, B didn't do something and C broke."

Although the inquiry into last year's Ladbroke Grove crash has not yet been completed, it appears to have been the result of just such a combination.

"There have been concerns about the adequacy of the driver training, about the siting of the signal and the driver going through a red light when a train was coming in the opposite direction," says Mr Smith.

"On their own they might not have caused a problem but when you get a poorly trained driver going through a red light when visibility is poor and another train is coming there is the potential for a crash."

Chris Milner, deputy editor of Railway Magazine, says attention is likely to focus on the possibility of problems with the track or the train itself.

"From what we know of the incident, it was the rear part which was derailed. I would have thought that if any debris was placed on the line, it would have either been pushed away or caused the front part of the train to derail.

"That suggests a failure in the train's wheels or axles, or a track defect, and that will be for the investigators to look into," he says.

The same type of rolling stock, Mark Four coaches, was involved in a derailment two years ago, when the 17.30 from King's Cross to Edinburgh came off the tracks at Sandy in Bedfordshire, train operator GNER confirmed last night.

Following the incident, in which nine people were hurt, GNER removed all the Mark Four coaches from service to check their wheels, after discussions with Railtrack and the Health and Safety Executive.

Investigations found metal fatigue in the wheels of the rolling stock, which is operated only by GNER and which was introduced in 1989.

Rail magazine's Pip Dunn says: "Broken wheels and broken axles are really fantastically rare on the railways but when they do happen they can be catastrophic.

"It was very fortunate that the incident at Sandy two years ago did not result in any serious injuries. Although vandalism can never be discounted, it appears to be unlikely in this incident and the fact that the stretch of track was continuously welded also suggests that a broken rail is not the cause either."

The line had been the subject of a bomb threat two days before the crash, although police said the initial examinations suggested the damage was not the result of an explosion.

According to the Health and Safety Executive, the number of significant derailments is running at a fairly constant level of between 22 and 29 a year.

But even though vandalism appears to be less likely as the cause of yesterday's crash, it is still the most common cause of rail incidents. About 55 per cent of all train accidents are the result of vandalism, with provisional figures of 198 incidents of arson last year, 277 of obstructing the line and 518 of missile damage.

Rail vandalism costs an estimated £250m a year in repairing damage and in delays. And, according to an HSE spokeswoman, even a small object on the line can pose a serious problem to a train travelling at high speed.

Railtrack and the British Transport Police tour schools and youth clubs to try to get the message home about keeping away from the lines. And the last 12 months has seen improved safety fences erected along part of the East Coast Main Line in the North-East, mainly around built-up areas.

The rail industry is also starting to fit improved warning systems in the wake of a number of crashes in the 1990s. The Train Protection Warning System, which automatically halts trains travelling at up to 70mph if they go through a red light, is now being installed. And this is expected to be followed by the Automatic Train Protection, which works for all trains at all speeds.

But the Rail Passengers Council is keen to emphasise the relative safety of travelling by train. "Statistically it is 20 times safer than going by car," says national director Anthony Smith.

"It is a safe way of getting around and we do have to remember that. If people stop travelling by trains because they think they're unsafe they are putting themselves at greater risk."

Figures from the Royal Society for the Prevention of Accidents show train passengers are considerably safer than those who fly, with one death for every 148 million rail journeys, compared with one for every ten million air passengers.

"An absolutely safe railway would involve nothing moving at all," Mr Smith says. "We're looking at a system that is as safe as it reasonably and practically can be.

"There is always room for improvement and the spate of accidents over the last few years has shown there are issues which need to be seriously addressed.

"Obviously, our thoughts are with the people who are injured and bereaved, but the railway is a safe way of getting around."

But, despite rail travel's safety record and even as the investigators piece together the circumstances of the crash, one thing is certain - yesterday's tragedy has added another day to the calendar of commemorations.