Cannabis, alcohol and fatal road accidents

• Published in: PloS one 2017-11, Vol.12 (11), p.e0187320-e0187320
• Main Authors: Martin, Jean-Louis, Gadegbeku, Blandine, Wu, Dan, Viallon, Vivian, Laumon, Bernard
• Format: Article
• Language: English
• Subjects: Accidents; Accidents, Traffic - statistics & numerical data; Alcohol; Alcohol Drinking - epidemiology; Alcohol use; Alcoholic beverages; Amphetamines; Analysis; Automobile Driving - statistics & numerical data; Biology and Life Sciences; Cannabis; Cannabis - adverse effects; Cocaine; Coding; Consumption; Drinking and traffic accidents; Driving; Driving ability; Driving Under the Influence - statistics & numerical data; Drug abuse; Drugs; Drunk driving; Drunkenness; Epidemiology; Ethanol - adverse effects; Ethanol - blood; Fatalities; France - epidemiology; Hazards; Health aspects; Humans; Illegal drugs; Life Sciences; Marijuana; Medicine and Health Sciences; Mortality; Narcotics; Odds Ratio; Opiates; Opioids; Physical Sciences; Police; Prevalence; Research and Analysis Methods; Risk assessment; Risk Factors; Santé publique et épidémiologie; Studies; Traffic accidents; Traffic accidents & safety; Traffic information
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0187320

This research aims to estimate the relative risks of responsibility for a fatal accident linked to driving under the influence of cannabis or alcohol, the prevalence of these influences among drivers and the corresponding attributable risk ratios. A secondary goal is to estimate the same items for three other groups of illicit drugs (amphetamines, cocaine and opiates), and to compare the results to a similar study carried out in France between 2001 and 2003. Police procedures for fatal accidents in Metropolitan France during 2011 were analyzed and 300 characteristics encoded to provide a database of 4,059 drivers. Information on alcohol and four groups of illicit drugs derived from tests for positivity and potential confirmation through blood analysis. The study compares drivers responsible for causing the accident, that is to say having directly contributed to its occurrence, to drivers involved in an accident for which they were not responsible, and who can be assimilated to drivers in general. The proportion of persons driving under the influence of alcohol is estimated at 2.1% (95% CI: 1.4-2.8) and under the influence of cannabis at 3.4% (2.9%-3.9%). Drivers under the influence of alcohol are 17.8 times (12.1-26.1) more likely to be responsible for a fatal accident, and the proportion of fatal accidents which would be prevented if no drivers ever exceeded the legal limit for alcohol is estimated at 27.7% (26.0%-29.4%). Drivers under the influence of cannabis multiply their risk of being responsible for causing a fatal accident by 1.65 (1.16-2.34), and the proportion of fatal accidents which would be prevented if no drivers ever drove under the influence of cannabis is estimated at 4.2% (3.7%-4.8%). An increased risk linked to opiate use has also been found to be significant, but with low prevalence, requiring caution in interpreting this finding. Other groups of narcotics have even lower prevalence, and the associated extra risks cannot be assessed. Almost a decade separates the present study from a similar one previously conducted in France, and there have been numerous developments in the intervening years. Even so, the prevalence of drivers responsible for causing fatal accidents under the influence of alcohol or narcotics has stayed remarkably stable, as have the proportion of fatal accidents which could in theory be prevented if no drivers ever exceeded the legal limits. The overall number of deaths from traffic accidents has dropped sharply durin