Road lighting: A pilot study investigating improvement of visual performance using light sources with a larger gamut area

Many past studies investigating visual performance focused mainly on the effect of luminance contrast between the target and background. Other studies have suggested the importance of colour contrast on visual performance. This pilot study was designed to investigate whether visual performance in the context of road lighting can be improved by enhancing the chroma of targets. Observers were asked to detect an off-axis target with different levels of luminance, hue, and chroma on a uniform background at 1.5 cd/m². When the target and the background were set to the same luminance, a zero luminance contrast, the detection rates were significantly lower and the reaction times were significantly longer. Enhancing the colour contrast between the target and the background by increasing the target chroma level, however, was found to improve visual performance to similar levels as those when the target was revealed by luminance contrast against the background. Such an enhancement on colour contrast can be achieved in practice using light sources with a greater colour gamut size.