They were reading, chatting - then an almighty bang turned their world over

Collision on a crossover

Collisions such as last night's at Watford Junction are usually caused by one of two factors - either the driver of one of the trains missed a red light, or there was a signalling error.

In this case the accident happened at a point where there are four lines, two up to London and two northwards. The two fast lines, on which InterCity trains normally travel, are on the western side, while the two slow lines, used by North London commuter services, are on the east. The empty train, which was travelling from Bletchley to Euston, appears to have been crossing from the right-hand up-slow line to the up-fast. This meant it had to cross the down-slow line on which the 5.04pm train, which was running six or seven minutes late, was travelling. It appears that this was where the trains collided. From the initial pictures it looks as if the empty train struck the commuter train a glancing blow.

The spotlight will be on Railtrack, as last night's accident comes only months after the company was privatised on the stock exchange for pounds 1.9bn. In the run-up to privatisation there was a series of leaks revealing senior managers' fears over the safety of the new regime.

Railtrack has defended its safety record since it was separated from British Rail two years ago. In fact, 1995/6 was one of the safest on the railways.

If there is any question of a driver having jumped a red light, the crash is bound to increase demands for automatic train protection, which stops a train if the driver goes through a red light. While the universal application of ATP was recommended by the inquiry into the Clapham Rail disaster, British Rail and Railtrack have refused to do the work, saying the money would be better spent on other improvements. The demand for ATP is likely to be overtaken by newer technologies. The West Coast Main Line where the crash happened is due for an overhaul in the next few years.

Passengers might be grateful that the rolling stock was just 10 years old. Newer rolling stock is designed to crush on impact. Therefore, lives may have been saved.

The Watford crash is the second major rail disaster this year. In March, one man was killed when a derailed freight train near Stafford was hit head-on by a mail train.