The study by Strathclyde University found that the lower limit for blood alcohol content (BAC) had not been followed by a statistically significant overall drop in road fatalities, including during the peak accident periods of night-time and weekends.
There was also little change in the death rate for young drivers aged 16-25, who are seen as one of the highest-risk groups for drink-driving.
The legal alcohol limit for driving was reduced from 80mg to 50mg in every 100ml of blood in 2014.
The researchers, from Strathclyde’s Department of Economics, are clear that they are not suggesting that previous BAC limit reductions had not been ineffective only that the most recent reduction had not had a material impact on road safety.
The study assessed data on more than 1.1 million accidents, leading to 1.5 million casualties and more than 14,000 fatalities, between 2009 and 2016, with prevailing weather conditions also taken into account.
They found that, in the two years leading up to the lower BAC limit, Scotland had monthly accident rates of 740.63 and fatality rates of 14.96.
In the two years after the new limit was introduced, the rates were 704.13 for accidents and 15.25 for fatalities. This was consistent with England and Wales, where the BAC limit remained unchanged.
The change in policy did not appreciably affect overall accident rates, which statistically increased slightly by 0.18 accidents per 100,000 of population, although this is not statistically significant.
The researchers said: “While there may be other reasons to pursue a reduction in the BAC limits, our results suggest that this further BAC limit reductions has not achieved all that might have been hoped for it in terms of road safety.
“This is not to say that previous BAC limit reductions have been an ineffective means of preventing traffic fatalities. Instead, our results indicate that the marginal returns to further BAC reductions in terms of road safety are small, which is result that policy makers should take into account when weighing the costs and benefits of alcohol-control policies.”
Brigid Simmonds, chief executive of the Scottish Beer & Pub Association, said: “The change in the drink-driving limit may not have affected road accidents, but it has definitely affected the nation’s pubs. Since its introduction, rural pubs have been squeezed with many closing their doors for good as a direct result of the policy.
“What we would like to see from the Government is a commitment to working with the pub sector to address the range of issues which are badly impacting our industry. This includes acknowledging the key social and economic benefits pubs bring to our cities, towns and villages.
“We firmly believe the key to reducing incidents on our roads is through education and awareness. That is why our industry continually partners with a range of stakeholders to promote education through campaigns such as THINK and designated drivers.”