Highway driving safety the day after using sleep medication: the direction of lapses and excursions out‐of‐lane in drowsy drivers

Verster, Joris C.; Mooren, Loes; Bervoets, Adriana C.; Roth, Thomas · 2018 · Crossref

DOI: 10.1111/jsr.12622

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Summary

This study investigates the safety implications of highway driving the day after using sleep medication, specifically focusing on the directional characteristics of two distinct driving errors: lapses and excursions out-of-lane. While the Standard Deviation of Lateral Position (SDLP) is the traditional gold standard for measuring driving impairment, its direct relationship to crash risk remains unclear. The authors sought to determine whether lapses and excursions are conscious or unconscious events by analyzing the direction in which drivers deviate from their lane—either toward the adjacent traffic lane (left) or the road shoulder (right). Understanding this distinction is critical for assessing the nature of drowsiness-induced impairment and its associated accident risks. The researchers re-analyzed data from 240 on-road driving tests conducted in two previous studies involving healthy volunteers aged 21–65. Participants drove 100 km on a public highway in normal traffic, maintaining a steady speed of 95 km/h, one hour after waking up following bedtime or middle-of-the-night administration of hypnotic drugs (zolpidem, zaleplon, ramelteon, zopiclone) or placebo. A lapse was defined as a lateral deviation of at least 100 cm lasting 8 seconds or more, while an excursion out-of-lane was defined as crossing the lane delineation. The study identified 628 lapses and 401 excursions out-of-lane across all conditions. Statistical analyses compared the frequency and direction of these events to determine if drivers exhibited awareness during loss of vehicle control. The results revealed a significant difference in the directionality of the two error types. Lapses occurred almost equally to the left (49.4%) and right (43.3%), indicating a random distribution with no statistical preference for direction. In contrast, excursions out-of-lane were overwhelmingly directed to the right, into the safer road shoulder (97.3%), with only 2.7% directed into the adjacent traffic lane. Furthermore, the frequency of lapses showed a clear dose-response relationship with the sedative properties of the drugs, occurring significantly more often after hypnotic administration than placebo, whereas this effect was not significant for excursions. These findings suggest that lapses represent unconscious periods of inattention or micro-sleep, as drivers are unaware of the deviation and thus steer randomly, posing a high risk by potentially entering oncoming traffic. Conversely, excursions out-of-lane appear to be conscious events where drivers, aware of losing control, instinctively steer toward the safer road shoulder. The authors conclude that lapses are a critical indicator of impaired driving safety because the driver’s lack of awareness prevents corrective action. This distinction highlights the need for further research, such as EEG monitoring during driving, to validate the physiological basis of these events and better understand the mechanisms underlying drowsy driving accidents.

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Topics

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• lane positioning
• sleep deprivation
• drowsiness
• human error taxonomy
• microsleep
• vigilance

Information type

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• Empirical Findings: behavioral performance data, crash risk outcomes, observational prevalence