The actual proportion of road fatalities due to alcohol; Update of the estimation method. Alcohol is one of the most important factors in road crashes. Alcohol reduces driving skills, heightens the risk of crashes and increases the risk of sustaining severe injury in a road crash. is available in The Netherlands has no reliable data on the proportion of road crash casualties related to alcohol. Although hospitals and police register alcohol use among road crash casualties, the registration is not complete. Therefore the official data leads to an underestimation of the problem. In 2011, SWOV developed a methodology to estimate the actual proportion of serious road injuries with a blood alcohol content (BAC) the 0.2 g/l or above. This method is based on the results of the Dutch hospital studies for the European research projects DRUID and IMMORTAL and on data on the proportion of alcohol offenders in weekend nights provided by the Dutch national study into driving under the influence (ROI). This SWOV estimation method, however, did not use confidence intervals. An update of the methodology and making the necessary changes, made it possible to include confidence intervals in the estimation method. This will illustrate the uncertainty of this estimation. This method, based on ROI data, estimates the changes in the proportion of car drivers with a BAC of 0.2 g/l or higher. The proportion of severely injured car drivers turns out to be largely determined by the small group of serious alcohol offenders with a BAC of 1.3 g/l and above). The uncertainty in the estimate has been translated into two variants: 1. a variant with a less steep decline (the 'cautious' variant); 2. a variant with a stronger decline. The cautious variant indicates (with 95% reliability) that in 2013 16.4% to 23.9% of the severely injured car drivers were under the influence of alcohol. The second variant indicates that in 2013 the proportion of severely injured car drivers in alcohol-related crashes was between 10.9% and 18.1% (with 95% reliability). The estimation of the proportion of road deaths due to alcohol is based on estimates regarding the role of alcohol among severely injured car drivers. Assumptions have been made for the difference between the proportion critically injured car drivers related to alcohol use and (all) fatalities directly due to alcohol consumption on the basis of available data and literature. It turns out that the effects of these assumptions more or less outweigh each other. We therefore estimate the current proportion of alcohol fatalities among all road users on the basis of the variant with a cautious assessment of the decline to be about 16%-24.0%. For the total number of fatalities of 570 in 2013, the estimated number of road fatalities due to alcohol use in the traffic is about 90 to 135. The second variant result in a range of 11% to 18%, which corresponds with about 60 to 100 deaths due to alcohol use in the traffic. Depending on the variant chosen, the number of alcohol-related fatalities in 2013 was roughly between 60 and 135. There is a considerable uncertainty about the current estimate. This uncertainty translates into two estimation variants and a number of assumptions of which the correctness cannot be established with absolute certainty. For better understanding of which variant ultimately gives the most accurate estimate, a large-scale hospital study needs to be carried out in the next few years which always measures the BAC of severely injured car drivers is measured. This data can be used to evaluate the current estimate so that the current estimate can be adjusted or worked out further, where necessary.
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