Abstract: The inner wall of tunnel is an important part for the tunnel′s lighting environment. The existing lighting calculation methods cannot accurately describe the reflective characteristics of the sidewall materials when solving the reflective enhancement of the inner wall of tunnel, the deviation between the results of calculation method and the measured data is large, which is not conducive to tunnel lighting safety and energy saving. To address these problems, an improved lighting calculation method is proposed. With the help of discreteelement thinking, the tunnel sidewall is considered as a number of reflective units, the bidirectional reflectance distribution function (BRDF) of the sidewall is introduced, and based on which the effect of sidewall reflection brightening on the path surface is calculated. The results show that: (1) Compared with the calculation methods in the related specifications of tunnel lighting, the difference between the calculated results and the measured values of the improved method is much smaller, only 3.5%. (2) The auxiliary lighting effect of different materials used as tunnel sidewall materials is evaluated in terms of the illumination and evenness of the pavement wall and sidewall; and compared with the dedicated putty material, the energy storage reflective luminescent material on tunnel sidewall is more conducive to energy saving.

Key words: highway tunnel, lighting calculation, light reflecting enhancement, bidirectional reflectance distribution function (BRDF), energysaving