The specific focus of this survey has been the prevalence of illicit drug use in road traffic in thirteen European counties. The literature search conducted to accomplish this survey included the relevant scientific journals, institutes' reports published over the last decade and the proceedings of the last two conferences organized by the International Council on Alcohol, Drugs and Traffic Safety in 1995 and 1997. In a total of thirty studies have been critically reviewed in order to present the prevalence of illicit drug use alone and in combination with alcohol as well as multiple drug use. The prevalence of licit drug use is also presented, since this has been frequently reported in most studies. The different scope of the various studies entails prevalence being presented in different driver populations, such as `general driver population', `drivers suspected of driving under the influence of alcohol and/or drugs' and `collision-involved drivers'. Different methodological problems arise with sample collection and data collection in many studies, thus most study outcomes do not allow comparisons across different European in countries. Differences may occur especially in selecting the sample of drivers if police forces in one country focus more on detecting drugged drivers than in other countries. One general problem for all categories of driver populations is the representativeness of the sample under examination, which is also a problem if small sample sizes are included and/or selection criteria are not clear. Only four large scale studies have been published, one German study focusing on the general driver population, one Norwegian study involving drivers suspected of driving under the influence of drugs, and two studies, from Belgium and Italy, in which collision-involved drivers were screened for drugs. The results from these studies are not expected to completely reflect the situation in other countries, for one thing because of societal and cultural differences that determine drug use patterns (licit and illicit drug use) and the impact of public campaigns, which is mostly unknown. Consequently the conclusions from these studies are intended to be indicators for further discussion. In the general driver population the prevalence of illicit drug use will probably fall in the range of 1%-5% (cannabis and opiates being most frequently observed), whereas licit drug use will fall in the range of 5%-15% (with benzodiazepines being most frequently detected). The prevalence of the combination of illicit drugs with alcohol reflects much more of a problem than the combination of licit drugs with alcohol, probably because patients tend to be much more aware of impairing effects of this combination. The prevalence of multiple drug use in the general driver population is very low if the German results are taken as an indicator. In populations of drivers suspected of driving under the influence of drugs high prevalences of licit drug use (primarily benzodiazepines) are reported ranging from 14%-74%. The prevalence of illicit drug use is lower than for illicit drugs (9%-57% for cannabis, 8%-42% for opiates, and 1%-20% for amphetamines). These findings depend on the perception and awareness of police officers in the different countries who decide on the inclusion of a driver in the sample. Remarkable differences between countries are observed, for example the prevalence of the use of amphetamines in Norway is relatively high, while in contrast the use of opiates is rather low. The combination of licit and/or illicit drugs and alcohol is expected to be high in samples selected for suspicion of driving under the influence of drugs/alcohol. However, in most studies the data for separating the prevalence of combinations of drugs (including alcohol) are lacking. The prevalence in drug positive cases is 25% in Norway, whereas the prevalence in all drivers in the sample in two Swiss studies ranged from 18%-28%. The prevalence of multiple drug use is reported in a few studies for all licit and illicit drug use together. A high prevalence (62%) has been observed by Swiss researchers. In collision-involved drivers the prevalence of illicit drug use ranged from 10%-25% in the different studies. Cannabis and opiates are about equally divided among the samples (6% and 7.5% respectively) and are detected about two to three times more frequently than amphetamines. Cocaine has been detected with a very low prevalence (0.5%-0.7%) in Belgium and Italy, whereas in Spain a high prevalence (5%-7%) has been reported. The prevalence of the combination of drugs (licit and illicit together) and alcohol use in drug positive drivers ranged from 27%-65% in most studies. The prevalence of multiple drug use is also reported in most studies for licit and illicit drugs together and ranged from 20% in the Belgian study to 36% in a Norwegian study in drug positive cases. When considering the complete driver sample in some other studies, the prevalence is lower, from 5% in the study in the United Kingdom to 17.5% in an Italian study. It should be stressed that knowledge about the prevalence of drug positive drivers in different driver populations cannot prove that the use of drugs is a serious safety problem. Ideally, a study to determine accident risks needs to match collision-involved drivers for case-control comparisons. In most countries (except for Germany) there is a lack of data on the prevalence of drugs among the normal driver population. The high prevalence of drugs found in representative samples of collision-involved drivers supports the assumption that there is a serious road safety problem. However, Europe does not have an approach in which standardized methodologies are applied in repeated studies during a given period of time in each country for cross national comparisons. It is recommended that such studies should be embarked upon and that national laws prohibiting roadside surveys should be abolished or modified to permit the same surveys to be conducted on a pan-European basis. (A)
Abstract