Paddington crash Q&A

The latest report into the Paddington rail crash which claimed 31 lives says the track itself could have contributed to the disaster. The inquiry has focused on one of the two trains involved - the Thames train - and its apparent failure to stop at a red signal. Our transport correspondent Tim Hirsch answers the vital questions.

What does the report say could have happened in the cab of the Thames train ?

It says the driver may have heard a bell sound in the cab indicating that the signal ahead was green, instead of a horn warning of a red or yellow signal. It is "conceivable", according to the inspectors, that vibration caused by a misaligned track joint could have produced a false reading from the trackside magnet linked to the train's warning system.

What was unusual about signal 109 - the visual signal - which may have confused the driver?

Instead of being placed one above the other as normal, the lights on the gantry were arranged like a backwards "L", with the red light over to one side - it would not have been at the centre of the driver's vision as he looked at the signal. The inspectors are still assessing the significance of this.

Which signal should a driver act on - the visual signal or the one that sounds in the cab ?

Ultimately the visual signal is the instruction to the driver - the horns and bells in the cab are just warnings of what lies up ahead. If a horn does sound, the driver must acknowledge it by pressing a button in the cab, otherwise the brakes will come on automatically.

If the "all-clear" sound in the cab was triggered incorrectly does this mean the driver was not to blame for the crash?

It would shift much of the responsibility away from him, explaining why he would have been confused - this was only his tenth shift since qualifying. However the two signals ahead of 109 showed double yellow and yellow, indicating a red light up ahead, and there is no doubt that the red light itself was working.

There are a number of different warning systems in use - would another type of system have prevented this crash ?

Both the system being installed across the network by 2003, the Train Protection Warning System, and the more sophisticated Automatic Train Protection, already in place in much of Europe, would have forced the Thames train to stop after running the red light, and would have prevented the crash.

What are the chances of this fault occuring on other trains?

The Railway Inspectorate are still describing it as a "theoretical possibility" - it has never been known to happen before, even though the system has been in operation for several decades. They are carrying out further tests to discover how much of a risk this might be.

Are there any safety systems in the pipeline which can make trains completely safe ?

No transport system is ever 100 per cent safe - the ATP system, which will eventually be installed on most high-speed lines in Britain, should make it far more difficult for crashes to happen, but it is worth remembering that the 1998 train disaster in Germany which killed more than 100 people was caused by a faulty wheel. Signals and the response to them are not always at the root of train accidents.