Energy Savings in Tunnel Lighting by Improving the Road Surface Luminance Uniformity—A New Approach to Tunnel Lighting—

The authors propose a new method for tunnel illumination using LED lights. The luminous characteristics of tunnel lighting employing LED luminaires were measured in the Shiratori tunnel on the Japanese expressway. The results show that this method achieves over 0.9 of luminance uniformity. Moreover, the visual impression evaluation that was conducted using 29 subjects, shows that roads with over 0.9 luminance uniformity and luminance of 2.3 cd/m2, have equivalent or better visibility than roads with low uniformity and luminance of 3.5 cd/m2. This result suggests that the High Luminance Uniformity Method which we propose could save up to 20% of the energy used for illumination and improve safety due to