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There is considerable evidence for the negative effects of driver distraction on road safety. In many experimental studies, drivers have been primarily viewed as passive receivers of distraction. Thus, there is a lack of research on the mediating role of their self-regulatory behavior. The aim of the current study was to compare drivers' performance when engaged in a system-paced secondary task with a self-paced version of this task and how both differed from baseline driving performance without distraction. Thirty-nine participants drove in a simulator while performing a secondary visual"manual task. One group of drivers had to work on this task in predefined situations under time pressure, whereas the other group was free to decide when to work on the secondary task (self-regulation group). Drivers' performance (e.g., lateral and longitudinal control, brake reaction times) was also compared with a baseline condition without any secondary task. For the system-paced secondary task, distraction was associated with high decrements in driving performance (especially in keeping the lateral position). No effects were found for the number of collisions, probably because of the lower driving speeds while distracted (compensatory behavior). For the self-regulation group, only small impairments in driving performance were found. Drivers engaged less in the secondary task during foreseeable demanding or critical driving situations. Overall, drivers in the self-regulation group were able to anticipate the demands of different traffic situations and to adapt their engagement in the secondary task, so that only small impairments in driving performance occurred. Because in real traffic drivers are mostly free to decide when to engage in secondary tasks, it can be concluded that self-regulation should be considered in driver distraction research to ensure ecological validity.
Chronic non-cancer pain (CNCP) is a major health problem. Patients are increasingly treated with chronic opioid therapy (COT). Several laboratory studies have demonstrated that long-term use of opioids does not generally impair driving related skills. But there is still a lack of studies investigating on-the-road driving performance in actual traffic. The present study assessed the impact of COT on road-tracking and car-following performance in CNCP patients. Twenty CNCP patients, long-term treated with stable doses of opioid analgesics, and 19 healthy controls conducted standardized on-the-road driving tests in normal traffic. Performance of controls with a blood alcohol concentration (BAC) of 0.5 g/L was used as a reference to define clinically relevant changes in driving performance. Standard Deviation of Lateral Position (SDLP), a measure of road-tracking control, was 2.57 cm greater in CNCP patients than in sober controls. This difference failed to reach statistical significance in a superiority test. Equivalence testing indicated that the 95% CI around the mean SDLP change was equivalent to the SDLP change seen in controls with a BAC of 0.5 g/L and did not include zero. When corrected for age differences between groups the 95% CI widened to include both the alcohol reference criterion and zero. No difference was found in car-following performance. Driving performance of CNCP patients did not significantly differ from that of controls due to large inter-individual variations. Hence in clinical practice determination of fitness to drive of CNCP patients who receive opioid treatments should be based on an individual assessment.
Abstract: The number of accidents that can be attributed to driving under the influence of psychoactive substances (alcohol, drugs, and certain medicines) is constantly on a high level with drugs and medicines proportionally increasing over the years. The overall objective of the EU 6th Framework Programme project DRUID is to gain better knowledge of the various aspects of driving under the influence of drugs, alcohol and medicines. DRUID wants to offer scientific support to EU transport policy makers by suggesting guidelines and measures to combat impaired driving. To reach this ambitious aim a wide range of studies is conducted. The various studies are divided into seven work packages with complex interdependencies. There are experimental studies assessing the effects of single and combined psychoactive substances on driving performance (WP1) as well as epidemiological studies aiming to assess the situation in Europe regarding prevalence of alcohol and other psychoactive substances in drivers (WP2).The principal objective of these studies is to gain relative risk estimates for traffic accident involvement of drivers impaired by psychoactive substances and to recommend substance concentration thresholds. A theoretical framework which allows the integration of the experimental and epidemiological findings serves as a fundament for developing these recommendations. WP3 aims at improving the possibilities of detecting drug driving in Europe. Police forces evaluate practically (under realistic enforcement conditions) oral fluid screening devices. A scientific evaluation of oral fluid screening devices and other methods (i.e. roadside checklists of signs of impairment) is done as well. The outcome of the practical and scientific evaluations serves as input to cost-benefit analyses of enforcement.