Abstract:  In order to optimize the design of lightreducing shed of highway tunnels, the height of lighttransmitting area on both sides of lightreducing shed is studied. Firstly, numerical analysis is used to study the direct irradiance area and brightness variations of the road surface under different configurations of lightingreducing shed. By establishing numerical analysis models for lightingreducing shed with topdiffusing plate and hollowdesign on both sides, various optical parameters of lightingreducing shed and the brightness distribution of road surface are analyzed under different conditions. According to the requirements of direct irradiance area, illuminance of road surface under the shed, and brightness uniformity, a comparative analysis of two conditions is conducted. The lighttransmitting area height of lightreducing shed are determined to be three meters for the north side and two meters for the south side, which can mitigate the sudden brightness change when entering and exiting the tunnel, and reduce the glare effect at the tunnel entrance. Driving safety and comfort are enhanced with the improvement of driving environment at the tunnel entrance.

Key words: highway tunnel, lightreducing shed, lighttransmitting area, skeleton height, illuminance, brightness uniformity, driving safety