Lorry driver Ian Lawrence has been told he faces prison after falling asleep at the wheel and killing another motorist.

And a court heard it was the fourth time in just over 18 months Lawrence, of Browning Close, Exeter, had crashed into the back of other vehicles in mid afternoon.

The 60-year-old was driving a lorry which careered into the back of a truck killing road maintenance worker Nick Hall.

Other road users were so concerned about his driving they stopped to tell police who went to pull the lorry over but found the wreckage of the crash.

Only five weeks before the fatal crash, which Lawrence can't remember, he crashed into a marked police car which was stationary, with its lights flashing, directing traffic on a motorway.

Mr Hall, 44, from Marlborough, was described in court as a shy, quiet, hard-working, family man who was devoted to his wife and two sons, aged four and eight.

He was on his way back to the Ringway depot, Wiltshire County Council's highway contractors, after painting white lines on the roads when the accident took place.

Ian Glen QC, prosecuting, told Swindon crown court: "This is a case highlighting the problem of falling asleep at the wheel."

On the day of the crash, July 23 last year, Lawrence was working for Weston-super-Mare-based Complete Delivery, taking goods to a chain of convenience stores in Wiltshire.

Mr Hall had pulled over his lorry and trailer on the A350 at Upton Scudamore between Westbury and Warminster and was standing between them when the lorry hit. He was killed instantly.

Lawrence's day began at 4.41am when he drove to Avonmouth depot to make deliveries.

Mr Glen QC said: "At two shops staff said he looked tired. He even told one staff member he was 'knackered'."

He left Collerne and headed to the store at Amesbury on the A350. He was followed by the Gillingham family who observed his driving.

Mr Glen QC said: "After seeing him clip the kerb and hit the bank at the side of the road the family decided to call the police. They spotted a patrol car and pulled over. One member of the family said 'He's going to kill someone'."

An off-duty firefighter driving behind the lorry said he was concerned when it stopped at a green traffic light. He then saw the lorry increase speed and drive straight into the back of Mr Hall's trailer.

The chasing police car encountered the traffic jam caused by the accident.

Mr Glen QC said Lawrence should have seen the lorry he hit for 34 seconds before the impact which took place at about 2.30pm.

He said Lawrence had a habit of nodding off between 2pm and 4pm which is a time of day when people feel sleepy.

Simon Morgan, defending, said his client did not feel tired before the accident but accepts he 'fell asleep briefly' before the crash.

The court heard Complete Delivery has filed for bankruptcy and is being investigated for its part in the accident.

Releasing Lawrence on bail for pre-sentence reports, Judge John McNaught told him to expect a jail term.