In December 2014, the legal blood alcohol limit for drivers in both Scotland and New Zealand was reduced from 80 to 50 mg/100 mL. This paper reports a retrospective study comparing changes in the toxicological findings in deceased drivers and motorcyclists before and after the limit change in both jurisdictions.
A year of fatal motor vehicle crashes prior to and following the limit change was examined for both countries. In Scotland, there was an increase in drug prevalence among fatally injured drivers and motorcyclists, with the use of all drug groups increasing after the limit change, with the exception of cannabinoids. In New Zealand, there was a reduction in cases involving drugs only, but increases in the numbers of deceased drivers and motorcyclists positive for alcohol only and co-using alcohol and drugs.
Source: The Effect of Lowering the Legal Drink-Drive Limit on the Toxicological Findings in Driver Fatalities: A Comparison of Two Jurisdictions,. Hamnett, H. J. and Poulsen, H. (2018). J Forensic Sci.