Safety evaluation of lighting at very long tunnels on the basis of visual adaptation

Purpose: The present study aims to carry out safety evaluation of lighting at very long tunnels on the basis of visual adaptation in one of long tunnels in Ilam province. Methods: The required lighting in both lines of the tunnel was designed by considering equivalent veiling luminance, atmosphere luminance and windshield luminance. Moreover, luminance of different zones was measured using IESNA LM-71-96 and IESNA LM-50-99 standards in order to compare the designed values with measured values. Results: Veiling luminance in northern and southern lines of the tunnel are 116.7 and 127.5 cd/m(2), respectively. Moreover, windshield luminance are, respectively, 220 and 238.4 cd/m(2). In addition, atmosphere luminance are 290 and 307 cd/m(2) for northern and southern lines. According to these data, the designed luminance in threshold zone are 548 and 576 cd/m(2) for two northern and southern lines of the tunnel. Accordingly, the selected tunnel is very long, the required lighting in the first section of entrance zone are 6 and 6.2 cd/m(2), and 2 and 2.3 cd/m(2) in the second section of entrance zone for northern and southern lines. Furthermore, the required lighting at the end of exit zone are 10 and 11.5 cd/m(2) for northern and southern lines. Eventually, designed values of luminance (cd/m(2)) in the studied tunnel were compared with measured values of luminance (cd/m2). Conclusions: Using surfaces with low reflection coefficients and planting trees and meadows in surroundings of the tunnel can decrease the required lighting.