Almost four in five motorists risk exceeding the drink-drive limit by miscalculating the alcoholic content of pub measures, a new study suggests.
Some 80 percent underestimate the unit content in a pint of lager and 55 percent get it wrong on a large glass of wine, the Daily Mail reported.
It is commonly thought a man can consume up to four units before going over the limit - 80mg of alcohol per 100ml of blood - while a woman can only have between two and three.
But medical experts stress this is not a safe guide, as much depends on factors such as age, weight, gender and metabolism.
Police say that the only infallible rule is: If you drive, don't drink, and if you drink, don't drive.
Road safety campaigners say confusion over units makes it almost impossible for drivers to calculate whether or not they are under the legal limit.
Carole Whittingham, national secretary of the Campaign Against Drinking and Driving said: "Most people do not have a clue about how many units they have consumed."
"There is so much confusion. Not even a mathematician could work out how many units you have had," she said. (ANI)