HALF of drinkers cannot tell when they have reached the drink/drive limit, scientists have warned.

The more alcohol people drink, the worse they become at judging whether it is safe for them to get behind the wheel, according to a new study.

Drink driving remains a major problem worldwide, despite decades of warning people about the risks of getting behind the wheel after one too many.

Road traffic accidents have become the leading killer for young people aged between five and 29, with booze being one of the main causes.

Now researchers at Cambridge University have found people's poor judgement is part of the problem.

Author Dr Kai Hensel said: "In countries with legal alcohol limits, it's usually the driver who makes a judgement about how much they've drunk and how fit they are to drive.

"But as we've shown, we are not always good at making this judgement.

"As many as one in two people in our study underestimated how drunk we are - and this can have devastating consequences."

In 2019, between 240 and 320 people were killed in a crash in Britain where at least one driver was over the limit - the highest level since 2009.

A two day experiment involving 90 students was carried out in Germany to determine if they recognised when to stop drinking before driving.

Participants were split into two groups, and given beer and wine until they reached a maximum breath alcohol concentration (BrAC) of 0.11per cent.

The drink-driving limit in Germany is 0.05 per cent, which is 0.03 per cent lower than in England and Wales.

Participants were told they would be switched from beer to wine or vice versa once they had reached 0.05 per cent, but not that it was the legal driving limit.

Breathalysers were used to keep track of how much the students drank throughout the exercise.

With each measure, they were asked to guess the concentration of alcohol in their breath and come forward once they thought they had reached the driving limit.

More than a third of students - 39 per cent, had exceeded the drink-driving limit by the time they stepped forward.

On the second day this proportion increased to more than half (53 per cent).

Also, the more alcohol students consumed the worse they became at guessing their level of intoxication. Dr Hensel said: "This could have serious consequences in England and Wales, where the legal driving limit is higher, as it suggests that a significant number of people might misjudge how drunk they are and consider themselves fit to drive when in fact they have a potentially dangerously high level of alcohol in their blood."

Their finding could help come up with new and more effective ways of reducing the number of deaths from drink driving accidents.

Dr Hensel said: "Drinking and driving is a major risk fact for road traffic accidents.

"Anything that can be done to reduce these numbers is worth trying.

"With guidance, our participants were able to improve their judgement.

"It could be that pop-up stalls set up around drinking establishments that help people understand their breath alcohol concentration might help people."

How much people can drink before safely driving away depends on a wide range of factors.

Dr Hensel said: "Really, the best advice is that if you're driving, just don't drink.

"But if you really do feel like a drink, then look into your own alcohol tolerance.

"This differs from one person to the next, depending on your sex, weight and age, and there are some reliable apps out there than can help guide you."

The findings were published in the Harm Reduction Journal.