A POLICE officer tried desperately to avert the Berkshire train crash in which seven people died, it was revealed last night.

The off-duty officer saw a saloon car on the crossing and then watched as the barriers moved into the prevent-entry position with the vehicle still there.

The Thames Valley officer ran to the emergency phone at the crossing to summon help - but the London to Plymouth First Great Western express train struck the car before he could get through.

The car driver - a man - was one of people killed in Saturday night's accident at the automatic half-barrier outside the village of Ufton Nervet, near Reading.

A police spokeswoman said that officers had not ruled out the possibility that the car driver was attempting to commit suicide.

When asked whether officers would be looking at the man's medical history, he said: ''We never jump to conclusions, but obviously this is a major line of inquiry when you get such unusual behaviour. We won't make any assumptions.

"One of the reasons why we're going to examine the motor vehicle in such detail is to see if there are any other explanations for what might have happened."

The Queen expressed her sympathy to Transport Secretary Alistair Darling, saying she was shocked and saddened to learn of the crash in which 150 of the 300 passengers were hurt, with 19 people still in hospital.

As rail unions and safety experts called for a review of level crossing policy, Mr Darling promised a full investigation into the tragedy - the first at a level crossing to involve rail passenger deaths since the Lockington disaster, in Yorkshire, in 1986, in which nine lives were lost.

As workers prepared to clear the tracks of the derailed eight-car train, Deputy Chief Constable Andy Trotter, of the British Transport Police, described the events involving the off-duty officer.

Mr Trotter said: "An off-duty Thames Valley police officer was driving along the lane.

"As he approached the crossing he saw a stationary saloon car on the crossing, and he was obviously concerned about what was happening.

"He stopped his vehicle and before he could do anything the barriers came down.

"Realising there was a potential disaster he ran to the emergency phone to call the signal box, but before he got a response, the train came through."

The officer was on the phone for a matter of seconds, said Mr Trotter.

Mr Trotter denied reports that the officer had talked to the driver, who was alone in the car.

The driver of the Great Western train, which had left London at 5.35pm, was among the dead.

Passenger Jonathon Stace, 21, from London, who suffered an arm injury, said: "The lights went out. I felt like we spun over and after that I could feel bodies going on top of me and being thrown different places.

"It was pitch-black. We couldn't see anything."

When a train is due at a barrier such as the one in Berkshire, the barrier's amber lights come on for about three seconds and then red lights flash for four to six seconds before the barriers lower into place - a process that takes six to ten seconds.

A train travelling at 100mph would reach the crossing about 27 seconds after the barrier came down.

According to statistics from Rail magazine, there were 18 fatalities at level crossings last year, including five occupants of cars.

Network Rail said there were 24 collisions between trains and road vehicles at crossings last year - up from the figure of 16 in 2002.

RMT union leader Bob Crow yesterday called for all level crossings on high-speed lines to be removed, while train drivers' union Aslef said advanced cab warning systems should be installed in trains.

Royal Berkshire Hospital said medics treated 61 patients on Saturday night. Fifteen were still being treated. Four were serious but stable and one remained in a life-threatening condition.