Effects of vehicle headlights on target contrast in road lighting environments

Abstract

In this study road lighting measurements were made to Investigate the impacts of vehicle headlights on luminance contrasts of various targets located on the road. Altogether seven different studies were made to investigate the contribution of halogen and high-intensity discharge headlights to road lighting. The measurement results indicate that in general, the use of dipped vehicle headlights, in the presence of road lighting, does not improve the visibility of various targets located on the road. In fact, in most occasions when the targets were seen darker than the background, dipped headlights reduced target contrasts and in some cases they even made the target merge into the background. The impacts of vehicle headlights are highly dependent on the vehicle, headlights type, target reflection factor, position of the target, position of the vehicle and road lighting conditions. As assumed, the effects of HID headlights on targets luminance contrasts were more significant compared to the ones of halogen headlights.