Drivers can poorly predict their own driving impairment: a comparison between measurements of subjective and objective driving quality

Verster, Joris C.; Roth, Thomas · 2011 · OpenAlex-citations

DOI: 10.1007/s00213-011-2400-7

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Summary

This study investigates whether drivers can accurately perceive their own driving impairment when treated with central nervous system (CNS) drugs. The research addresses a critical public health concern: if drivers are unaware of their impairment, they cannot make safe decisions to avoid driving. While previous studies suggested drivers often overestimate their abilities, this paper specifically examines the correlation between subjective self-assessments and objective driving performance under the influence of various medications. The researchers analyzed data from three clinical trials involving 96 healthy volunteers who underwent standardized 100-km on-the-road driving tests in normal traffic. The primary objective measure of driving impairment was the Standard Deviation of Lateral Position (SDLP), which quantifies the vehicle's lateral "weaving." Subjective measures included pre-drive alertness ratings, post-drive perceived driving quality, and the mental effort required to perform the drive. Participants were administered various CNS-acting treatments, including alcohol, hypnotics (zolpidem, zaleplon), anxiolytics (alprazolam), analgesics (oxycodone/paracetamol), and antihistamines (diphenhydramine, levocetirizine), alongside placebo controls. Statistical analyses compared the difference scores from placebo for both objective SDLP and subjective assessments. The results revealed that while significant correlations existed between subjective measures and objective impairment, the predictive validity was low. Perceived driving quality accounted for only 24.8% of the variance in SDLP, mental effort accounted for 16.6%, and pre-drive alertness accounted for a negligible 1.3%. Crucially, the relationship between subjective awareness and objective impairment varied significantly by drug. For instance, drivers taking zolpidem were generally aware of their impairment, correlating subjective ratings with objective deficits. In contrast, drivers taking alprazolam or alcohol showed poor correlation between their subjective feelings and actual driving impairment, indicating they were often unaware of their degraded performance despite significant objective deficits. The study concludes that subjective assessments are unreliable indicators of actual driving impairment, particularly pre-drive alertness. This finding challenges the common medical advice for patients to "listen to their body" when deciding whether to drive after taking medication. The authors argue that physicians must take a more proactive role in educating patients about specific drug-related driving risks, as patients may not recognize impairment even when it is present. The results underscore the necessity of relying on objective testing rather than patient self-reporting to assess fitness to drive under the influence of CNS drugs.

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Topics

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• prescription meds
• polydrug
• decision making risk perception
• mci dementia driving
• sleep deprivation
• situational awareness

Information type

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• Empirical Findings: physiological data
• Methodological Resource: validation psychometrics
• Theoretical Contribution: theory or model