Pedestrian alertness during the evening is not affected by lighting conditions typically used for road lighting

Alshdaifat, A; Fotios, S · 2026 · Crossref

DOI: 10.1177/14771535251408746

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Summary

This study investigates whether lighting conditions typical of road environments affect pedestrian alertness during the evening. While light is known to influence non-image-forming physiological responses, such as melatonin suppression and vigilance, previous research using realistic road lighting levels yielded null results. To determine if these negative findings were due to insufficient experimental sensitivity or a genuine lack of effect, the authors conducted a controlled laboratory experiment. The study aimed to replicate prior work but included an "extreme" lighting condition to verify that the experimental design was capable of detecting physiological changes if they existed. The experiment involved 40 healthy participants aged 18–30, who underwent a 3-hour session starting at 21:00. Participants first adapted to indoor-like lighting (25 lx photopic, 10.7 lx melanopic equivalent daylight illuminance [EDI]) while seated. They then transitioned to walking on a treadmill at moderate intensity (50–70% of maximum heart rate) for one hour under one of four lighting conditions: L1 (<0.5 lx melanopic EDI), L2 (3.4 lx melanopic EDI), L3 (10.4 lx melanopic EDI), and L4 (98.8 lx melanopic EDI). Conditions L1–L3 represented typical road lighting ranges, while L4 served as an extreme control. Alertness was measured via auditory reaction time (RT), self-reported sleepiness using the Karolinska Sleepiness Scale (KSS), and salivary melatonin levels. The results demonstrated that only the extreme condition (L4) produced significant physiological and behavioral changes. Participants exposed to L4 showed significantly reduced reaction times, decreased subjective sleepiness, and significant melatonin suppression compared to the adaptation phase. In contrast, the three conditions representing typical road lighting (L1, L2, and L3) had no significant effect on any of the dependent variables. The inclusion of L4 confirmed that the experimental protocol was sensitive enough to detect lighting-induced effects, thereby validating the null findings for the lower illuminance levels. The study concludes that lighting conditions typically used for road lighting do not significantly affect pedestrian alertness, melatonin levels, or subjective sleepiness during the evening. This suggests that standard road lighting intensities are insufficient to trigger acute non-image-forming responses in pedestrians. The findings imply that while higher-intensity lighting can modulate alertness, the levels currently employed in street lighting are unlikely to provide these benefits, nor do they pose a risk of disrupting circadian rhythms through acute alertness mechanisms in this context.

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-26; verification: verified.

Topics

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• roadway lighting effects
• circadian factors
• dark adaptation mesopic
• visibility analysis litigation