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 has found.

The research, led by the University of Glasgow and published in The Lancet, evaluated the impact of the change in legislation which occurred in Scotland in December 2014, when the blood alcohol concentration limit for drivers was reduced from 80 mg/dL to 50 mg/dL.

Prof Jim Lewsey talks about his research

Driving under the influence of alcohol is a major risk factor for road traffic accidents (RTAs). There is strong evidence that the risk of RTAs increases with blood alcohol concentration level.

The study, which was undertaken in collaboration with partners at NHS Health Scotland, the University of Stirling and the University of East Anglia, suggests that lowering the legal blood alcohol concentration limit on its own does not improve RTA outcomes.

To conduct the study, the researchers used data from the whole of 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. The study design allowed the researchers to isolate 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.

Jim Lewsey, Professor of Medical Statistics, at the University’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.”

Prof Lewsey 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.”

The results from concurrent research led by the University of Stirling, and with Prof Lewsey as a co-investigator, are imminent and will help explain how the public interpreted and acted upon the change in drink-drive legislation.

The study also looked at alcohol sales and found the legislation reduced on-trade alcohol sales (e.g. in bars and restaurants, etc.) by less than 1%, and did not have an impact on off-trade sales (e.g. from supermarkets and convenience stores, etc.), which count for approximately three-quarters of total alcohol sold in Scotland.

In Great Britain there were at least 6,070 RTAs involving a drink-driver in 2016. It has been 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’ is published in The Lancet. The study was funded by the National Institute for Health Research (NIHR).

In Europe, only England & Wales and Malta, have a 0·08 g/dL blood alcohol concentration limit (BAC). Such limits, and higher, are the norm in many other jurisdictions including many states in the USA, despite long-standing calls for reductions. According to European Commission recommendations, BAC limits should be set at 0·05 g/dL. The British Road Safety Act (BRSA) introduced a legal limit of 0·08 g/dL in 1967, which is still in place today. An exception is Scotland where the BAC limit was reduced to 0·05 g/dL on 5th December 2014. Weekly RTA rates are higher in England & Wales than Scotland (broadly, the rates are between 5 to 9 RTAs per 1000 traffic count in Scotland, with the corresponding figures being 6 to 10 for England & Wales).

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Enquiries: ali.howard@glasgow.ac.uk or elizabeth.mcmeekin@glasgow.ac.uk / 0141 330 6557 or 0141 330 4831

First published: 12 December 2018