The number of Dutch drivers who drive under the influence of alcohol is lower than the European average. Driving after having taken medication also shows a lower average in the Netherlands than in the other EU countries. Driving after the use of cannabis and amphetamines, however, is higher in the Netherlands than the EU average. These are findings of the European study called DRUID, which the Institute for Road Safety Research SWOV participated in and which publishes its results today. The research indicates that driving under the influence of alcohol is still a much larger problem than driving under the influence of drugs.
Less than one percent (0.7%) of Dutch drivers drives with a blood-alcohol content (BAC) of 0.5 ‰ or more. The EU average is estimated to be twice as high (1.5%). In the Netherlands, the percentage of drivers who are under the influence of benzodiazepines or tranquillizers is 0.6% (EU: 1.4%). The use of cannabis and amphetamines among drivers is somewhat higher than the EU average in the Netherlands: 1.67% for cannabis (EU: 1.32%) and 0.19% for amphetamines (EU: 0.08%). For other drugs (cocaine, heroin) the use in Dutch traffic equals the EU average.
Increased risk
Although 0.7% of alcohol offenders seems a small number, SWOV estimates that in practice this means that alcohol is involved in 20% of the traffic fatalities in the Netherlands: in 17% of these cases it is just alcohol, and in 3% of the cases a combined use of alcohol and drugs is involved. The use of amphetamines in traffic appears to increase the risk of a serious injury with a factor of 5 to 30. The same is the case for a BAC of 0.8‰ to 1.2‰ and for drug-drug combinations. A BAC of 1.2‰ or higher and drug-alcohol combinations result in an extremely high risk increase (20-200). The use of cannabis on its own gives a risk increase that is comparable to a BAC of 0.1‰ to 0.5‰. The risk increase for benzodiazepines and tranquillizers is between a factor of 2 to 10. This is comparable with a BAC 0.5‰ to 0.8‰.
Enforcement and legislation
The DRUID study also investigated the practical use, reliability, and cost-effectiveness of several saliva testers to establish drug use. Although the testers that were investigated cannot trace all separate drugs in the saliva, they have been found suitable to be used as a preselection tool. The saliva test indicates whether a driver has used drugs, after which a blood test is necessary to establish which and how much of a substance has been used.
It must be observed that, although the use of drugs is known to increase the risk, it has as yet not been possible to establish how the use of these substances exactly relates to the increased risk of a crash (four risk classes, but no precise figures known). The study does, however, show how these substances affect driving ability. This provides a good basis for legislation against the use of drugs in traffic; such legislation is now being prepared in the Netherlands.
Recommendations
SWOV is positive about the legislation mentioned, which as yet will make use of drugs concentrations that affect driving ability. When more is known about the extent of risk increase this will have to be included in the legislation.
Although the use of only cannabis does not seem to lead to a serious increase in risk, SWOV does stress the very high risks of cannabis in combination with alcohol and in combination with other drugs. SWOV therefore recommends the use of public information to especially point out the dangers of using these combinations.
Results in other EU countries
The DRUID study has totalled and averaged the use of alcohol, drugs and medicines in traffic in the participating EU countries. It was then investigated to what extent a country or European region deviates from this average. Some striking results
Northern EU: the use of medicine in traffic is higher than the EU average (especially benzodiazepines and tranquillizers);
Eastern EU: the use of alcohol in traffic is lower than the EU average;
Southern EU: the use of alcohol, drugs and medicines is higher than the EU average;
Western EU: the use of alcohol, drugs and medicines (especially benzodiazepines) is equal to the EU average.
About DRUID
A total of thirteen EU countries participated in the DRUID research project which started in 2006. SWOV, Maastricht University, University of Groningen, the Netherlands Organization for Applied Scientific Research TNO, the Netherlands Forensic Institute NFI, the National Police Services Agency KLPD and six police regions participated for the Netherlands. All results of the research project can be downloaded from www.druid-project.eu
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