# Effects of Sidewall Brightness on LED Lighting Environment and Visual Performance in Road Tunnels
## 3 Tunnel Lighting Environment Parameters  
### Luminance and Illuminance in Tunnel  
The measured luminance and illuminance in tunnel when the sidewalls decorated with energy-storage and luminescent coating and gray cloth are shown in Tables 1 and 2, respectively. It can be seen from Table 1 that when the LED lamps turned on at the electric power of 10 W, in the tunnel decorated with energy-storage and luminescent coating, the  
Figure 5: Visible distance test for a small object in tunnel. Figure 6: Acquisition of a driver’s pupil diameter data. (**a**) Eye tracker, (**b**) the driver wearing eye tracker. average luminance values of the nine measuring points on pavement corresponding to the LED lamps with color temperatures of 2500 K, 3500 K, 4500 K, 5500 K and 6500 K were 2.7 cd/m\({}^{2}\), 2.7 cd/m\({}^{2}\), 2.8 cd/m\({}^{2}\), 2.7 cd/m\({}^{2}\) and 2.9 cd/m\({}^{2}\), respectively, and the average luminance values of the six measuring points on sidewalls corresponding to the LED lamps with color temperatures of 2500 K, 3500 K, 4500 K, 5500 K and 6500 K were 3.6 cd/m\({}^{2}\), 3.6 cd/m\({}^{2}\), 3.8 cd/m\({}^{2}\), 3.7 cd/m\({}^{2}\) and 3.9 cd/m\({}^{2}\), respectively. It can be seen from Table 2 that in the tunnel decorated with gray cloth when the LED lamps turned on at the same power, the average luminance values of the nine measuring points on pavement illuminated by the LED lamps with five different color temperatures were 2.1 cd/m\({}^{2}\), 2.2 cd/m\({}^{2}\), 2.3 cd/m\({}^{2}\), 2.1 cd/m\({}^{2}\) and 2.2 cd/m\({}^{2}\), and the average luminance values of the six measuring points on sidewalls illuminated by the LED lamps with five different color temperatures were 1.3 cd/m\({}^{2}\), 1.3 cd/m\({}^{2}\), 1.4 cd/m\({}^{2}\), 1.3 cd/m\({}^{2}\) and 1.4 cd/m\({}^{2}\). For the tunnel illuminated by the LED lamps with five different color temperatures, the luminance and illuminance distribution in the tunnel is basically the same. The luminance and illuminance distribution in tunnel illuminated by the LED lamps with the electric power of 18 W is similar to the above situation and will not be repeated here. As for the relationship between illuminance and luminance of pavement in the tunnel, the lighting specification of _\"Guidelines for Design of Lighting of Highway Tunnels_ (JTG/T D70/2-01-2014)\" [27] specifies that the conversion relationships between the illuminance and luminance are 10 and 15 on concrete and asphalt pavements, respectively. The pavement of the test tunnel is concrete pavement, and the relationships between pavement illuminance and luminance was 8.4-10.3 (see Tables 1 and 2). These values were close to the value specified in the specification, which verified the rationality of the test. \"Guidelines for Design of Lighting of Highway Tunnels_ (JTG/T D70/2-01-2014)\" [27] specify that the average luminance of the tunnel sidewalls, up to at least a height of 2 m, must be at least 60% of the average road surface luminance at the relevant location. The ratios of sidewall luminance to pavement luminance in the tunnel decorated with energy-storage and luminescent coating and gray cloth measured in the test were 1.3-1.4 and 0.6-0.7, respectively (see Tables 1 and 2), which meets the above specification requirements. When the pavement luminance in the tunnel having the sidewalls with gray cloth was in the range of 2.1-2.3 cd/m\({}^{2}\), the pavement luminance in the tunnel having the sidewalls with energy-storage and luminescent coating increased by 20-30% on the premise of the electric power of LED lamps keeps unchanged (see Table 1). On the same premise, when the pavement luminance in the tunnel with gray cloth was in the range of 3.4-3.7 cd/m\({}^{2}\), the pavement luminance in the tunnel with energy-storage and luminescent coating increased by 40-50% (see Table 2). The application of energy-storage and luminescent coating for auxiliary lighting can increase the brightness in tunnel [28; 29].