Study On The Influence Of Color Temperature Of LED Light Source On Tunnel Exit Adaptation

The research content of this paper is based on the National Natural Science Foundation Project "applicability research of LED light source spectrum/color temperature to tunnel lighting".As the "throat" of expressway,the tunnel is a semi-circular arch structure,and its interior is dark or even almost no light.Therefore,unlike ordinary road lighting,the tunnel should not only provide lighting at night,but also during the day.According to the lighting design rules of highway tunnel(JTJ 026.1-2014),the tunnel is divided into four sections:entrance section,transition section,middle section and exit section.Different lighting brightness is designed for each section to ensure the driver's driving safety.At the exit of the tunnel,the human eye enters the bright environment from the dim environment.The huge difference of light environment will make the human eye appear the phenomenon of light adaptation.The length of the light adaptation time will directly affect the driver's driving safety,and improving the brightness of the tunnel exit lighting is the most effective way to shorten the light adaptation time.However,with the rise of new lighting LED,as one of the important parameters of LED,the influence of color temperature on light adaptation has not been studied.Based on the characteristics of human vision,this paper first analyzes the lighting difference between the middle section and the exit section of the tunnel in theory.The exit section of the tunnel is mainly illuminated by sunlight.Therefore,this paper analyzes the differences in brightness,color temperature and spectrum between LED and sunlight with seven different color temperatures.The results show that the difference of color temperature and spectrum between 4500k led and sunlight is the smallest.Based on the theoretical analysis and experiment,taking the adaptation time of human eyesight as the evaluation standard,7 kinds of common color temperature(3000k-6500k),3 installation angles,2 installation heights of LEDs,and 60 observers of different ages were selected for the experiment in a 9-meter-long,5-meter-wide and 2.8m-high simulated tunnel.The experimental results show that:the greater the brightness difference inside and outside the tunnel,the longer the light adaptation time;when the brightness is the same,with the increase of LED color temperature,the light adaptation time first decreases and then increases,and the light adaptation time is the shortest at about 4500k;the installation angle and height of LED have little effect on the light adaptation time;the older the observer,the longer the light adaptation time.The conclusion of this study will provide data and theoretical support for the selection of color temperature of exit LED light source in the design and application of tunnel lighting.