Test Drives in the Daimler-Benz Driving Simulator with Drivers under Diazepam

Friedel, B.; Joo, S.; Reker, K.; Kading, W.; Klostermann, P.; Saturnus, K. S.; Schneider, V. · 1990 · ROSA P / United States. National Highway Traffic Safety Administration

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Summary

This study investigated the impact of diazepam, a widely used psychopharmaceutical frequently found in fatally injured drivers, on driving performance. Motivated by the difficulty of quantifying drug-related driving risks through epidemiological data alone, the research aimed to determine how specific dosages of diazepam impair driving ability in a controlled, realistic environment. The project was a joint effort between the U.S. National Highway Traffic Safety Administration (NHTSA) and German institutions, including the Federal Highway Research Institute and Daimler-Benz AG. The experimental design utilized the Daimler-Benz Driving Simulator, selected for its high degree of realism. Sixty male students aged 22–26 with moderate driving experience were divided into three groups of 20: a control group receiving no drug, a medium-dosage group (0.11 mg/kg), and a high-dosage group (0.22 mg/kg). Subjects underwent rigorous medical screening and personality assessments to exclude those with health issues or extreme personality traits. Each participant completed a 20-minute test drive comprising ten standardized scenarios, ranging from normal everyday responses to emergency situations requiring quick reactions. Driving variables such as speed, following distance, braking, and collision frequency were recorded. Additionally, subjects underwent psychometric tests assessing attention, perception, and mood, as well as blood serum analysis for diazepam levels. The primary finding was that no significant differences in driving performance existed between the three groups across any of the ten scenarios. Individual variability within groups exceeded differences between groups. However, trends emerged in specific scenarios: in two quick-response scenarios, there was a tendency toward potentially hazardous behavior in the drug groups, while in one quick-response scenario, the opposite trend appeared. Notably, twice as many subjects in the medium-dosage group engaged in potentially hazardous maneuvers compared to the control group in six of the ten scenarios, with the high-dosage group falling between the two. Psychometric tests showed no significant performance differences, though mood assessments indicated that the medium-dosage group felt calmer and the high-dosage group felt more withdrawn than the control group. The authors concluded that driving ability is not solely dependent on drug dosage but is influenced by compensatory mechanisms. They hypothesized that subjects in the high-dosage group, aware of their impairment, exerted extra concentration to maintain performance, whereas the medium-dosage group, underestimating the drug’s effects, failed to compensate and thus made more errors. The study highlights the complexity of assessing drug impairment, suggesting that while simulator results indicate potential risks, the extent to which drivers can successfully compensate in real-world traffic remains an open question.

Key finding

No significant differences in driving performance were found between control, medium dosage, and high dosage diazepam groups across ten standardized simulator scenarios.

Methodology

simulator

Sample size: 60

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

Topics

Ranked by relevance to this paper. Hover a topic for its definition.

• prescription meds
• simulator validity fidelity
• polydrug
• simulator sickness
• alcohol
• situational awareness

Information type

What kind of knowledge this paper contributes, grouped by family — independent of topic (what it is about) and method (how it was studied).

• Empirical Findings: behavioral performance data
• Methodological Resource: validation psychometrics, tool software