A large majority of company motorists drive while tired and even fall asleep while on the road.

Research by insurance company Norwich Union has found that 86% of motorists claim to have nodded off or got behind the wheel while sleepy. Investigations show that tired drivers are as dangerous as drink-drivers.

Bill Pownall, motor risk manager for Norwich Union, said: “Although fatigue and tiredness are both factors in driver safety, it is important to differentiate these signs from excessive sleepiness, including the symptoms of irritability or restlessness that could be due to the medical condition, known as Obstructive Sleep Apnoea (OSA).

“In recent incidents, we have seen fleet drivers exceeding their hours or simply ignoring the symptoms of being tired. Fleet managers need to be vigilant when it comes to vetting the driver’s health conditions and take notice if a driver complains of tiredness,” he added.

Mr Pownall said that up to 27% of drivers with OSA have had an accident after falling asleep at the wheel. Worryingly, most sufferers of OSA do not realise they even have the condition.

“Fleet managers can identify OSA through detecting its hallmark symptoms,” Mr Pownall said.

Symptoms to watch out for include restless sleep, loud snoring with periods of silence followed by gasps, morning headaches, trouble concentrating due to lack of restful sleep, irritability, forgetfulness and mood or behaviour changes due to poor sleep patterns over long periods.

“While the symptoms are persistent, avoiding driving altogether will reduce the risk of road accidents,” Mr Pownall said.

“It is the responsibility of the fleet manager to assess the safety of the driver’s ability to drive on a day-to-day basis.”