Visibility Evaluation of Expressway-Tunnel Lighting in Consideration of Vehicle Headlamps

Abstract

This paper quantitatively evaluates the visibility of an object on the road illuminated by vehicle headlamps under tunnel lighting based on Total Revealing Power (TRP). First, we derived the critical reflectance for drivers to detect an object on the road to calculate TRP. Then, we characterized optical property of vehicle headlamps in the real tunnel, and evaluated the visibility of objects under vehicle headlamps and tunnel lighting. As a result the high beam headlamps ensured the visibility of reverse silhouette vision. We have shown that the visibility of the tunnel lighting is mainly silhouette vision. It revealed that the visibility of an obstacle on the road is not changed greatly depending on headlamps.