If you don’t drink enough water while driving, it can be just as dangerous as being over the alcohol drink-drive limit.

It seems that drivers make far more mistakes when they are even mildly dehydrated, compared with when they are well hydrated, according to recent research.

A study found that drivers who drank only 25ml of water an hour more than double the number of mistakes that they make at the wheel, compared to drivers who drink 200ml an hour.

In fact, the dehydrated drivers compare well with drivers who have been drinking alcohol.

The study at Loughborough University, published in Physiology & Behaviour, found that dehydration can result in impaired mental functioning, changes in mood and reduction in concentration.

The errors of those who were dehydrated more than doubled, and ranged from lane drifting, late braking and touching or crossing the rumble strip or lane line.

The researchers also warn that warm weather leads to significant losses of water, and that too many drivers restrict fluids so as to avoid lavatory stops. 68 per cent of all vehicle crashes are due to driver error.