Reduction in drink-drive limit has not reduced the number of accidents, study finds

The lowering of the legal blood alcohol limit for drivers in Scotland has had no impact on the number of road traffic accidents, a new study involving the University of Stirling has found.

The research evaluated the impact of legislation, introduced by the Scottish Government in December 2014, which reduced the blood alcohol concentration limit for drivers from 80 milligrams per decilitre (mg/dL) to 50 mg/dL.

Driving under the influence of alcohol is a major risk factor for road traffic accidents (RTAs) and there is strong evidence that the risk increases with blood alcohol concentration level. However, the new study – led by the University of Glasgow and involving Stirling, the University of East Anglia and NHS Health Scotland – suggests that lowering the limit on its own does not improve RTA outcomes.

Dr Niamh Fitzgerald, of the Institute of Social Marketing at Stirling, co-authored the paper, which is published in The Lancet. She said: “It is difficult to say what is behind the lack of impact in this case, but it may be that the limit change failed to change people’s behaviour, or that it was not implemented or promoted sufficiently. We are exploring the reasons for this finding in further research which will be released in 2019.”

The researchers used data from Scotland, as well as England and Wales, and compiled counts of RTAs from police accident records, combined with alcohol consumption rates from market research data. They isolated the effect of changing the legal limit and assessed the sole effect of change in legislation without any enhanced law enforcement measures, such as random breath testing.

The findings could have significant policy implications for other international countries and jurisdictions considering similar legislation.

Dr Niamh Fitzgerald, of Stirling's Institute of Social Marketing, is a co-author on the study.

Jim Lewsey, Professor of Medical Statistics, at the University of Glasgow’s Institute of Health and Wellbeing, said: “Our findings are surprising, given what we know from previous international evidence, which generally supports a reduction of RTAs following the same lowering of a blood alcohol concentration limit.

“However, the results of our high-quality study are unequivocal – they indicate that the reduction in Scotland’s drink-drive limit in December 2014 simply did not have the intended effect of reducing RTAs.”

He added: “In our view, the most plausible explanation for our findings is that the change in legislation was not backed up with additional police enforcement, nor sustained media campaigning. It is also perhaps an indication of the safety of Scotland’s roads more generally, following continual improvements in recent years, and the fact that drink-driving is increasingly socially unacceptable.

“Drink-driving remains highly dangerous and against the law. It is important to stress that these findings should not be interpreted to imply that any level of drink-driving is safe.”

Dr Fitzgerald is leading concurrent research, which will help explain how the public interpreted and acted upon the change in legislation, how it was implemented, and the reasons for the lack of impact.

The Glasgow-led study also looked at alcohol sales and found the legislation reduced on-trade alcohol sales – for example, those in bars and restaurants – by less than one percent. They found it did not have an impact on off-trade sales – those bought in convenience stores and supermarkets – which count for approximately three-quarters of total alcohol sold in Scotland.

In the UK, there were at least 6,070 RTAs involving a drink-driver in 2016 – and it is estimated that drink-driver injury accidents cost the Scottish economy £80m per year.

The paper, ‘Evaluating the impact of lowering blood alcohol concentration limits for drivers on road traffic accident rates and alcohol consumption: a natural experiment’ was funded by the National Institute for Health Research.