Effects of spectral composition, illuminance and environmental complexity on walking performance, prefrontal cortex activity and subjective experience in younger and older adults: A multimodal study of pedestrian lighting

Lighting affects not only visual performance but also cognitive engagement and mobility, particularly in older adults navigating complex pedestrian environments. However, evidence linking lighting spectrum and intensity to real-world walking behaviour and the underlying cognitive mechanisms remains limited. This study examined how illuminance (5 vs. 500 lux), spectrally distinct lighting conditions (2700 K vs. 6000 K), and environmental complexity (obstacle presence) influence walking performance, prefrontal cortical activity, and subjective experience in younger and older adults under mesopic lighting conditions. Thirty-eight participants completed structured walking tasks in a full-scale pedestrian laboratory under systematically varied lighting conditions. Walking duration was used as a functional indicator of mobility performance. Functional near-infrared spectroscopy (fNIRS) was employed to index prefrontal cortical activation as a marker of cognitive engagement during walking, and participants provided repeated subjective ratings of visual comfort and perceived physical and mental effort following each condition. Results showed that dim and warmer lighting reliably slowed walking, whereas blue-enriched lighting and higher illuminance supported faster walking across environments. Older adults walked more slowly overall but derived greater benefit from blue-enriched lighting in visually and cognitively demanding settings, particularly under dim conditions. Neurophysiological findings revealed selective modulation of prefrontal engagement by lighting and environmental complexity, consistent with changes in attentional support rather than global increases in cognitive load. Subjective ratings indicated higher perceived effort under dim lighting, without reductions in comfort under blue-enriched light. These findings inform evidence-based pedestrian lighting design by showing that blue-enriched light can support safe, comfortable mobility in ageing populations environments.