Majority of drivers wrongly judge drink-drive limit

Researchers asked 90 people to drink beer or wine or both and say when they thought they had surpassed the limit. 

Worryingly, 53% of participants incorrectly believed they were safe to drive after drinking – not a promising figure at any time, but especially not in the run-up to Christmas.

The study’s authors are urging drivers to think more about the amount of alcohol they’ve drunk, rather than just how they perceive themselves to feel, in order to make better judgements about getting in the driver’s seat.

Dr Kai Hensel, who led the study from Cambridge University and Witten/Herdecke University in Germany, told the Harm Reduction Journal: “These findings show the importance of thinking carefully about getting behind the wheel.”

Ahead of the festive period, police are cracking down on drink- and drug-driving and targeting hotspots where the problem is rife. Last year 6,730 drivers were caught breaking the law.

Dr Hensel added: “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 they were – and this can have devastating consequences.”

Drinking alcohol affects drivers’ motor function – the more alcohol consumed, the worse this becomes. Motorists could struggle to keep their vehicle in lane, have slow reaction times and be more likely to take risks, leading to more accidents.

The number of people killed or seriously injured (KSI) in drink-drive crashes on Britain’s roads reached an eight year high in 2019, Department for Transport (DfT) figures show.

There were roughly 2,050 KSI casualties in collisions where at least one driver was over the alcohol limit, an 8% increase on the previous year and the highest level since 2011.

Participants of the alcohol study became worse at estimating their breath alcohol concentration the drunker they became, according to the German researchers.

Dr Hensel warned this could have “serious consequences” in countries with higher legal driving limits.

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The limit in England, Wales and Northern Ireland is 80mg of alcohol per 100ml of blood, while no other part of Europe has a limit above 50mg/100ml.

In 2014, the Scottish Government reduced the limit to 50mg/100ml.