The Impact of LED Light Color on the Dark Adaptation of Human Vision in Tunnel Entrances

For the study of dark adaptation at the entrance section of a tunnel, the effects of photopigments in rod cells and luminance can be disregarded because the luminance of this section is in the range of photopic vision. Instead, light color characteristics can be considered. This paper focused on the impact of light color, including correlated color temperature (CCT), color rendering, and spectrum, on dark adaptation at the entrance section of a tunnel. An experiment was performed based on seven kinds of high-power LEDs with different CCTs (3000-6500 K). The experimental results showed that the light color characteristics of LEDs significantly affected dark adaptation. Specifically, the better the color rendering and the lower the absence of blue light, the shorter the dark adaptation time. Among various LEDs with different CCTs, the 4000 K-4500 K LEDs have better light color characteristics and can shorten dark adaptation times. Therefore, LEDs with CCTs of 4000 K-4500 K are preferable for lighting tunnel entrances.