Tiredness can have more effect on drivers' reactions than a couple of drinks according to new research.

But insurers do not keep records of incidents.

“There are no records for habitual snoozers,” said a spokesperson.

The authors of a study published in Occupational and Environmental Medicine put 39 volunteers through a series of reaction, co-ordination and attention-span tests.

They found that those who had been awake for 17 to 19 hours did worse in tests than those tested in the morning with 50mg of alcohol in their bloodstream. The UK drink driving limit is 80mg.

Tiredness is a recognised cause of road accidents but a number of insurers said they did not keep figures on accidents caused by driver fatigue.