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

Abstract

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.

Effective Lighting Factors for Improving Visibility of Fallen Objects on the Road in Expressway Tunnels

“…More recently, pro-beam luminaires have provided reverse silhouette views of bright objects against the dark road surface. Kimura et al (2019) verified that improving the vertical illuminance using a pro-beam improves the view of the trailing vehicles. Several measures for quantifying visibility have been proposed.…”

“…Recently, several studies have improved the visibility in tunnels using light-emitting diode (LED) luminaires (Kimura et al, 2014(Kimura et al, , 2019Hirakawa et al, 2014Hirakawa et al, , 2015. LEDs provide more freedom in the lighting design than conventional light sources.…”

Road marking BRDF model applicable for a wide range of incident illumination conditions

“…Traditional road lighting is not designed to contribute to the retroreflection of these materials. However, a road lighting concept called "Probeam" [7,8] shows promising advantages over other, more common, road lighting concepts such as symmetrical road lighting. With Probeam, luminaires direct most of their luminous flux forward parallel to the driving direction; as such, their light contribution might become relevant at distances beyond the reach of car headlights.…”

Determining scalar illuminance from cubic illuminance data. Part 1: Error tracing

“…In the 1960s and 1970s, the concept of light flow was proposed to describe the subjective assessments of the strength and direction of lighting and the potential of light in producing distinct illumination patterns, either at a point or within a light field. [3][4][5][6] Since then, various threedimensional illuminance metrics have been proposed for quantification purposes, including mean cylindrical and semi-cylindrical illuminance, [7][8][9] scalar illuminance (spherical illuminance), 3,10 vectorial illuminance, 11,12 vector-to-scalar illuminance ratio, 4 cylindrical-to-horizontal illuminance ratio, 13 vector-to-cylindrical illuminance ratio 14 and so on. [15][16][17] However, the lack of commercial three-dimensional illuminance metres has limited the interest of lighting designers in vector illuminance-based metrics.…”