Research on the classification of brightness environment outside highway tunnel and the applicability of tunnel entrance luminance calculation method

This study is based on the relationship between the azimuth angle of the sun and the position of the tunnel entrance, as well as the theory of human eye glare, to classify the light environment outside the tunnel entrance, and collected images of the light environment outside the actual tunnel site. By using image analysis technology and using image gradient amplitude and three-dimensional distribution of image grayscale as quantitative parameters, the clarity and visibility of three different light environment scenes outside the tunnel were analyzed. The study concluded that the L20 method is suitable for scenes where the sun is obstructed by mountains and vehicles are driving towards the sun (Scene 3), The perceived contrast method is applicable to scenes where the sun is directly shining on the entrance of the tunnel (Scene 1) or scenes where the entrance is facing away from the sun (Scene 2). Based on the comprehensive analysis of the results, this study proposed principles for calculating the luminance of different tunnel entrance lighting environments. These principles can improve the lighting design of tunnel entrances, enhance the visibility and driving comfort of tunnel entrances.