Driving while even moderately dehydrated could put you in the same risk category as someone on the drink-drive limit.
The current heatwave makes research into the link between dehydration (even a mild form of it) and concentration by Loughborough University hugely relevant.
It found that drivers who took just 25ml of water an hour made twice the number of mistakes compared with those who took enough liquid.
The findings, published some time back, have since prompted experts to say that dehydration is an unrecognised danger for drivers. The increase in errors due to driver dehydration was found to be similar to what would have been the case if someone was driving under the influence of drugs or alcohol.
Increased driving errors included dangerous lane drifting and late braking - a sure sign of diminished concentration.
It is a timely, if slightly bizarre, reminder to all drivers during these heatwave days, with scorching temperatures forecast, that if you don't drink enough water you are likely to drive as badly as if you've consumed too much alcohol.
So get those water bottles on board.