Driver's visual luminance model considering the reflection characteristics of a tunnel’s inner wall: Theory and practice I

Abstract

A driver's visual luminance value under one-time stopping sight distance is the basic value for highway tunnel lighting design and quality evaluation. Currently, the driver's visual luminance value is obtained using the pavement reflection coefficient method with or without considering the diffuse reflection coefficient of the sidewall. This does not fully consider the influence of the reflection characteristics of the tunnel’s sidewall and pavement materials, potentially resulting in a large discrepancy between the measured and theoretically calculated values of driver’s visual luminance, which significantly affects the lighting design and quality evaluation of highway tunnels. Therefore, this study first establishes a driver's visual luminance theoretical model considering the reflection characteristics of the tunnel sidewall and pavement and uses the five-parameter model to fit the measured eigenvalues of the tunnel sidewall and pavement reflection to obtain a bidirectional reflectance distribution function. Theoretical calculation and actual measurement verification are performed using a 1:10 tunnel simulation model. Finally, the theoretically calculated value of visual luminance and the calculated values of the JTG and IESNA specifications are compared with the measured data of the tunnel simulation model. The results show that the mean error between the theoretically calculated value of visual luminance and the measured data remains at 6.0%, which is significantly lower than the corresponding errors in the JTG and IESNA specifications. After calculation, when a high diffuse reflection coating is applied to the sidewall of the tunnel, the driver's visual luminance can be increased by 16.8% on average.