A novel tunnel lighting method aided by highly diffuse reflective materials on the sidewall: Theory and practice

Abstract

Interior surfaces of tunnels can reflect light when a highly diffuse reflective material is used on the sidewalls. This study introduces a novel energy-saving method that uses the reflected light effectively. To validate the proposed method, the brightening effect of a highly diffuse reflective material is measured based on the bidirectional reflection distribution function (BRDF) of the sidewall materials. The BRDF specifies the reflective properties of the sidewall materials, and the incremental reflection is then quantified. The proposed method offers better computational certainty and sidewall material adaptability than those of existing methods. For different materials selected as test objects, the error between the calculated and measured values was controlled to be less than 5.35%. In addition, the relative error between the calculated and measured values, obtained using the proposed method, was 3.62% on average, and the corresponding errors obtained using China's lighting design rules and the Recommended Practice for Tunnel Lighting presented by the Illuminating Engineering Society of North America (IESNA) were 18.02% and 7.98%, respectively. Overall, the proposed method provides a theoretical basis to help realize the unification of tunnel lighting with safety, energy savings, and comfort.