Working paper 25. AUG 2010
Drink-driving convictions and the effect of lowering the BAC levels
Authors:
The Social Sector
The Social Sector
Driving while impaired (DWI) is a factor behind one in four fatal automobile crashes and one in six motoring casualties each year in Denmark. Drink driving is especially a problem for young men. The most important legal initiative has been lowering the blood-alcohol content (BAC) limit from 0.8‰ to 0.5‰ in 1998. The purpose of the paper is to evaluate if this initiative have had the intended effects on reducing young peoples’ drink-driving convictions.
Two nationwide birth-cohorts of young men are followed before and after lowering the BAC level. Using complete birth cohorts of men born in 1973 (N=36,540) and 1980 (N=29,944) the incidence of first-time drink-driving convictions was assessed using seven years’ experience before and seven years after the changed legislation while the young men were aged 17 to 24 years old. The preliminary results showed that young people (17-24 years old) are estimated to have 27 percent increased risk of DWI-conviction during 1997 to 2004 compared to young people in the same age group in the period 1990-1997.
Several risk factors known to be associated with the probability of being convicted of drink driving were included in the stepwise regression model (e.g. disadvantages during adolescence, severe psychological problems, prior criminal history, living in rural vs. metropolitan area, and their present social position, e.g. educational background). In order to evaluate the effect of changed legislation on the incidence of first-time drink-driving convictions among young people, the attributable-fraction and counter factual reductions of the known risk factors is estimated on the basis of a discrete time Cox model. Lowering the BAC-level in 1998 was not followed by an expected significant reduction in DWIconvictions. The overall risk of DWI-convictions was the same when the mentioned risk factors were included into the regressions model.
A part of the increased number of DWI-convictions during the observation period could be explained by an increase in numbers of young men exposed to risk factors associated with DWI and this was only partly compensated by increase in resilience factors such as education and employment factors. Lowering the BAC-limits seems not to be an effective measure to reduce DWI-convictions but DWI-behaviour must have changed according to the new BAClimits.
Two nationwide birth-cohorts of young men are followed before and after lowering the BAC level. Using complete birth cohorts of men born in 1973 (N=36,540) and 1980 (N=29,944) the incidence of first-time drink-driving convictions was assessed using seven years’ experience before and seven years after the changed legislation while the young men were aged 17 to 24 years old. The preliminary results showed that young people (17-24 years old) are estimated to have 27 percent increased risk of DWI-conviction during 1997 to 2004 compared to young people in the same age group in the period 1990-1997.
Several risk factors known to be associated with the probability of being convicted of drink driving were included in the stepwise regression model (e.g. disadvantages during adolescence, severe psychological problems, prior criminal history, living in rural vs. metropolitan area, and their present social position, e.g. educational background). In order to evaluate the effect of changed legislation on the incidence of first-time drink-driving convictions among young people, the attributable-fraction and counter factual reductions of the known risk factors is estimated on the basis of a discrete time Cox model. Lowering the BAC-level in 1998 was not followed by an expected significant reduction in DWIconvictions. The overall risk of DWI-convictions was the same when the mentioned risk factors were included into the regressions model.
A part of the increased number of DWI-convictions during the observation period could be explained by an increase in numbers of young men exposed to risk factors associated with DWI and this was only partly compensated by increase in resilience factors such as education and employment factors. Lowering the BAC-limits seems not to be an effective measure to reduce DWI-convictions but DWI-behaviour must have changed according to the new BAClimits.
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SFI - Det Nationale Forskningscenter for Velfærd
