The impact of LED spectrum and correlated color temperature on driving safety in long tunnel lighting

Abstract

According to the Chinese Guidelines JTG/T D70/2-01-2014, there are many long tunnels in China, especially in mountainous areas. In long tunnels, tunnel lighting influence not only visual performance but also non-visual effects. Non-visual effects has enhanced the importance of some factors directly related to driving safety, such as pupil constriction and visual fatigue which seriously affect reaction time of driver. In this work, the relationship between LED spectrum, correlated color temperature (CCT) and reaction time, pupil area difference are analyzed respectively by the experiment of reaction time. Five LEDs with different CCT and short-wave relative spectral value (RSV) are compared to HPS and MH under different tunnel lighting conditions. Experimental results show that, in the threshold and transition zone of long tunnel at luminance160cd/m2, 80 cd/m2 and 24 cd/m2, reaction time is the shortest and pupil constricted the most for LED lighting with CCT 5100 K and short-wave RSV 0.312. While in the interior zone of long tunnel at luminance 4.5 cd/m2 and 2.5 cd/m2, reaction time is the shortest and pupil constricted the most for LED lighting with CCT 3800 K and short-wave RSV 0.215. Based on the results, combining the impacts of visual performance and non-visual effects in long tunnels, this work proposed the recommended values of CCT and short-wave RSV for LED light sources that are suitable for the luminance level of different zones. In this way, the precise lighting can be implemented to meet the needs of long tunnel lighting for driving safety and energy saving.