A Loughborough University study has revealed that even mild dehydration is equivalent to being over the drink driving limit in terms of driver errors.

Researchers at Loughborough University carried out a range of tests over two days on male drivers, using a laboratory-based driving simulator.  During the normal hydration test there were 47 driving incidents, but when the men were dehydrated that number more than doubled to 101 – a similar number to what might be expected of someone driving under the influence of drugs or alcohol.  These included lane drifting, late braking and touching or crossing the rumble strip or lane line.

Professor Ron Maughan, Emeritus Professor of Sport and Exercise Nutrition at Loughborough University and Chair of the European Hydration Institute Science Advisory Board led the study. He said: “We all deplore drink driving, but we don't usually think about the effects of other things that affect our driving skills, and one of those is not drinking and dehydration.

“There is no question that driving while under the influence of drink or drugs increases the risk of accidents, but our findings highlight an unrecognised danger and suggest that drivers should be encouraged to make sure they are properly hydrated.

“To put our results into perspective, the levels of driver errors we found are of a similar magnitude to those found in people with a blood alcohol content of 0.08%, the current UK legal driving limit. In other words drivers who are not properly hydrated make the same number of errors as people who are over the drink drive limit.”

With driver errors accountable for 68% of all vehicle crashes in the UK, the European Hydration Institute, who sponsored the research are urging drivers to be cautious and ensure they are adequately hydrated before setting off on journeys, especially during the warmer summer months.  The level of dehydration induced in the study was mild and could easily reflect that of individuals with limited access to fluid over a busy working day.

Jane Holdsworth, Director of the European Hydration Institute (EHI), said “Anecdotal evidence suggests that many drivers avoid drinking on long journeys to minimise bathroom stops, yet we know that even mild hydration can cause symptoms such as headache, tiredness and lethargy. Driver error is by far the largest cause of road traffic accidents and the EHI wanted to test whether mild hydration had an impact on the incidence of common driver errors.”

The research has been published in the medical journal Physiology and Behaviour.