Effects of flicker with various brightness contrasts on visual fatigue in road lighting using fixed low-mounting-height luminaires

The flicker effect caused by the periodical succession of bright and dark bands on the road surface and tunnel walls can momentarily distract drivers and poses a safety concern. Low-mounting-height luminaires are typically used to illuminate long underground roads. However, the resulting flicker effects persist for longer duration, which can cause accidents. Although flicker frequencies have been extensively discussed, limited studies have focused on the effect of the ratio of background brightness to luminaire surface brightness on the flicker effect in road lighting. In this study, two experiments were performed to investigate the effect of reducing brightness contrast (BC) on human visual fatigue. BC can be decreased by reducing the surface brightness of the lamp (Experiment 1) and increasing background brightness (Experiment 2). The flicker frequencies in Experiment 1 were 4 and 6 Hz, and 6 Hz in Experiment 2. The study involved 49 participants. The results revealed that the blink rate and visual fatigue change rate (VFCR) decreased with a decrease in BC. The flicker frequency of 6 Hz is more effective than that of 4 Hz by reducing the surface brightness of lamps on the VFCR. This method is more effective in reducing the brightness of the surface of the lamp than increasing the background brightness to relieve eye fatigue. The proportion of time in a minute that the eyes are at least 80% closed (P80) increases as BC increases. This study may provide guidance for urban road lighting and road lighting product design.