A driver was killed when his car struck a concrete bridge in a high-speed crash on the Bingley relief road.

The male motorist, believed to be married with young children, died at the scene after his red Citroen Xsara Picasso people carrier hurtled into the side of the new bridge carrying the A650 old Bingley road over the bypass at Crossflatts.

The car had apparently left the road just before the near-side crash barriers and travelled at high speed for about 100 yards along grass banking before hitting the bridge head-on ten feet above the carriageway.

The impact was described by one witness as sounding like two trains smashing into each other.

Police described the accident as "horrific" and said the cause was a mystery.

No other vehicle was involved in what was the first fatal accident on the £47.9 million bypass which opened shortly before last Christmas.

Emergency services were called to the scene shortly before 3.30pm on Saturday.

A passing paramedic was first to arrive and an ambulance crew attended soon after but they were unable to save the victim, who had suffered multiple injuries.

Firefighters from Bingley, Shipley and Keighley cut the man's body from the wreckage.

Police closed the Bradford-bound carriageway of the bypass while the debris was removed and an examination of the scene was carried out.

The dead man is understood to be from Saltaire, in his 30s and married with at least children of primary school age.

Inspector Steve Whitworth, of West Yorkshire Police, said: "It was an horrendous accident.

"The cause of the crash is a mystery. No other vehicle was involved and we are investigating how it happened. Nobody else was in the car."

Leading Firefighter Steve Dodd, of Bingley fire station, said the car had been travelling very fast and the cause of the crash appeared to be driver error.

"No other car was involved and the road conditions and visibility were good," he said.

"When we arrived, three minutes after it happened, the car was embedded in the concrete bridge.

"We stabilised the vehicle and used cutting gear to cut the driver out, which took about ten minutes.

"It was a very serious accident, quite horrendous."

Mr Dodd said it was the fifth accident crews from Bingley had attended on the bypass since it opened.

A witness, who works a few hundred yards from the scene, claimed the bypass was dangerous and said paramedics parked up in vehicles further down the road in case of accidents.

The man, who did not want to be named, said he was at work when he heard the impact of the crash.

"It sounded like two trains crashing into each other head on. The rail line is next to the bypass and that's what I thought had happened, the bang was so loud.

"I dashed outside and saw the car embedded in the bridge. We phoned for an ambulance straight away but just looking across at the damage to the car you could tell that you would be wasting your time trying to do anything to help.

"A paramedic car hangs around, parked up near the sewage works, and he was first on the scene but it was clear there was nothing he could do because he soon walked away."

The man said he believed speeding was becoming a problem on the dual carriageway which opened shortly before last Christmas.

"The speed limit is 50mph but people come past here at 70 or 80mph," he said.

A spokesman for West Yorkshire Ambulance Service confirmed a "responder" paramedic was first on the scene, followed by a crew about a minute later.

She said the responder was one of several in the county who were placed at locations where they were likely to be needed.

Police have appealed for witnesses to the accident to contact the Keighley Police help desk on (01535) 617059.