Luminance coefficients of road surfaces for low angles of illumination

This paper describes research on forward and backward light reflection of road surfaces for typical vehicle-related illumination and observation conditions. The aim is to improve luminance simulation in order to include quality criteria of headlamp light distributions that correspond to visual perception under night driving conditions. Measurements were performed under full scale conditions instead of the usual laboratory tests. Traffic safety requires tests under dry and wet conditions. The experimental data can be described by luminance coefficient-based models. Due to its fixed geometry, backward reflection can be covered with a single luminance coefficient. For forward reflection an angular dependent reflection model is described with which headlamp light distributions can be improved for their impact on automatically detected oncoming traffic even under wet conditions.