Entrances and exits road tunnel are high-risk areas for traffic accidents. The average energy cost for the lighting in road tunnels is estimated to be around 900,000 RMB (c.a. 150,000 US dollars) per kilometer annually. Safety and energy saving are always hot issues of road tunnel lighting.
Recent studies show that the design of operation lighting for road tunnels should not only focus on the brightness and uniformity of the road, but also minimize the “black hole” and “white light” phenomenon at entrances and exits respectively. It was shown when the main peak wavelength of the illumination light falls in the range of 490 to 570 nm, the visibility of small objects to human eyes to is significantly increased. Such a visual reference frame suitable for human vision helps to mitigate visual fatigue.