Effects of daylight and darkness at daytime versus nighttime on driver sleepiness: A driving simulator study

Meyerson, Amanda; Eklind, Johanna; Fischer, Florian; Aramrattana, Maytheewat; Fredriksson, Ingemar; Ahlström, Christer · 2024 · Crossref

DOI: 10.1016/j.trip.2024.101087

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Summary

This study investigates the impact of ambient lighting conditions on driver sleepiness, specifically comparing simulated daylight versus darkness during both daytime and nighttime driving. Motivated by the need to disentangle the effects of light exposure from circadian rhythms and homeostatic sleep pressure, the research addresses previous inconclusive findings regarding whether lighting interventions effectively mitigate fatigue. The authors hypothesized that darkness would increase sleepiness, particularly during nighttime when drivers are sleep-deprived. The experiment utilized a within-subject 2 × 2 design involving 20 participants who drove in a fixed-base driving simulator. Participants completed four 60-minute drives on a monotonous rural road: two during the day (alert condition) and two during the night (sleep-deprived condition, after being awake since early morning). Lighting conditions were manipulated by pairing visual simulator graphics with ambient room lighting. The "daylight" condition featured daytime visuals in a room lit with 212 lx of LED light, while the "darkness" condition featured nighttime visuals in a dark room with 1 lx. Sleepiness was assessed using subjective ratings (Karolinska Sleepiness Scale), divided attention performance, driving metrics (lateral position deviation), physiological markers (heart rate variability, blink behavior), and psychomotor vigilance tests (PVT). The results demonstrated significant differences in all sleepiness indicators between daytime and nighttime drives, confirming that drivers were significantly sleepier at night. Sleepiness also increased with time-on-task. However, no significant main effects were found for lighting condition across any sleepiness indicator. While there were minor interaction effects—such as slightly higher subjective sleepiness ratings in daylight during the day and worse lateral control in darkness during the night—these did not support the hypothesis that darkness inherently exacerbates sleepiness compared to daylight in this controlled setting. The PVT results also showed no significant effects for lighting condition. The study concludes that, under the tested conditions, ambient lighting did not significantly alter driver sleepiness levels. The authors suggest that the lack of effect may be due to the specific spectral composition of the light or the modest intensity used, noting that previous studies often used different illuminance levels or spectral profiles. The findings imply that darkness may affect specific driving behaviors, such as lane positioning, without necessarily altering overall alertness levels as measured by the indicators used. The authors recommend further longitudinal research in realistic settings to better understand the specific cognitive and behavioral impacts of driving in darkness versus daylight.

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Topics

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• dark adaptation mesopic
• circadian factors
• drowsiness
• sleep deprivation
• shift work driving

Information type

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• Empirical Findings: physiological data