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Abstract
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ABSRACT Objective In some countries, per se laws for other drugs than alcohol are used to judge drunk and drugged drivers. These blood concentration limits are often derived from experimental studies on traffic relevant behavior of healthy volunteers. Knowledge about how results from experimental studies could be transferred to a real life setting is missing. The aim of this study was to compare impairment seen in experimental studies to the impairment seen at equivalent concentrations in apprehended drunk and drugged drivers.
METHODS Results from previously performed meta-analyses of experimental studies regarding impairment from alcohol, tetrahydrocannabinol (THC) and benzodiazepines were compared to impairment in apprehended drunk and drugged drivers as judged by a clinical test of impairment. Both experimental studies and real life cases were divided into four groups according to increasing blood drug concentration intervals. The percentage of impaired test results in experimental studies was compared to the percentage impaired subjects among drivers within the same blood drug concentration window.
RESULTS For ethanol, the percentage of impaired drivers (n=1223) increased from 59% in the lowest drug concentration group to 95% in the highest drug concentration group, compared to 7% and 72% in the respective groups in experimental studies. For THC, the percentage of impaired drivers (n=950) increased from 42% to 58%, the corresponding numbers being 11% and 42% for experimental studies. For benzodiazepines, the percentage of impaired drivers (n=245) increased from 46% to 76%, the corresponding numbers being 16% and 60% for experimental studies. The increased odds ratio for impairment between two concentration groups was comparable for experimental studies and impaired drivers.
CONCLUSIONS Fewer test results indicated impairment in experimental studies compared to impaired drivers in real life when influenced by similar blood concentrations of either ethanol, or THC or benzodiazepines. In addition, a comparable relationship between drug concentration and impairment was seen for both experimental studies and real life cases. We believe the present study strengthens the background for using experimental studies to establish fixed concentration limits for drunk and drugged drivers, but experimental studies in an impaired driver population could further expand our knowledge.
Keywords: Cannabis impaired driving
Language: en |