LUNCHTIME drinkers are a potential menace if they take to the road even after a legally safe amount of alcohol, new research suggests.

Experts say far less alcohol is needed during the middle of the day than at night to have a serious affect on driving ability.

The study found that a small alcohol level - one that would easily pass a police breathalyser test - could be dangerous for lunchtime drinkers because of its impact on the natural afternoon dip in mental alertness.

But the findings were met with a mixed reaction from lunchtime drinkers in the pavement bars and cafes of Manchester yesterday.

Some poured scorn on the research, believing they would be fit to drive after a lunchtime tipple while others agreed and called for a total ban on drinking any alcohol before driving.

The effect of lunchtime booze is even greater on drivers who have not slept well the night before, according to sleep experts.

Drivers who fall alseep cause around one in ten road crashes in the UK.

Experts from the Sleep Research Centre at Loughborough University tested the alertness of 12 young men who had to drive for two hours in the afternoon in a fully functioning stationary car on a simulated motorway.


The drivers were aged between 20 and 26 years old, the age group most at risk of road crashes.

The young men's driving skills were tested after drinking small amounts of alcohol or a non-alcoholic equivalent after a night of normal sleep and after a night of disturbed sleep.

The research team assessed the amount of lane drift, the participants' subjective levels of sleepiness and graphs of brainwave activity.

Both the afternoon dip in alertness, caused by fluctuations in the body clock and a disturbed night's sleep, and alcohol independently increased the amount of lane drift, which typifies road crashes caused by driver sleepiness.

But lane drift was significantly worse when sleepiness and alcohol were combined.

The drivers themselves did not seem to notice the additional effect of alcohol on their sleepiness.

The researchers warn that the impact of the natural afternoon dip in alertness, even after a good night's sleep, will be worsened by a modest alcohol intake at lunchtime at levels that would pass a roadside breathalyser test.

Professor Jim Horne, who led the research, said: "Alcohol has a soporific effect which may accentuate any underlying sleepiness in drivers having a blood alcohol level well within the legal limit.

"Because of the natural dip in alertness in the afternoon, drivers are more liable to be sleepy at this time, especially after a disturbed night. Under these conditions, alcohol at lunchtime may be particularly potent.

"Motorists are placing themselves at a greater risk of having a sleep-related crash if they choose to drink any alcohol before they drive."