Importance of a Vector Component and the Vertical Illuminance in Road Lighting for the Obstacle Visibility of the Road

The authors introduce LED tunnel illumination for improving the vertical illuminance by considering the light as vectors when designing the light distribution. This new illuminating devices installed and evaluated the visibility of the road at Hanzan Tunnel for the down line of Takamatsu Expressway. As the result, the vertical illuminance is improved by 40% when increasing the ratio of vector component of light by using the Pro-bean. Actually, according to the questionnaire result of subjects who had a driver’s licence were different by gender, ages and driving experience, by increasing the vertical illuminance the visibility of the leading vehicle are improved significantly. Therefore, it is expected that the Pro-Beam illumination for improving the visibility by increasing the vertical illuminance is effective in reducing traffic accidents in tunnel.