OBSERVATIONAL STUDY OF DRIVERS' LIGHTING BEHAVIOR AT DUSK: PSYCHOPHYSICAL THRESHOLD AND EFFECTS OF PASSING TUNNELS
 
Yoshida, S., Tohoku Gakuin University, Japan
 
Drivers' lighting behavior was observed at dusk on five fine days and a cloudy day in April, July and November in Japan. The three types of lighting were classified into no light, side lights and headlights. Their percentage of the videotaped cars was counted per five minutes. The psychophysical threshold model fits along logarithm of brightness (lux) rather than the time of sunset. Switching on side lights corresponded to "neither (equal)" in the method of three categories. On the equally bright spot lighting rates and the threshold differed in two streets, one of which was an exit of a tunnel and the other was an opposite lane or a parallel street. Passing through a tunnel increased the lighting rate and lowered the threshold of lighting. The tunnel effect was detected 1.5km far from the tunnel. The increased lighting rates by passing a tunnel didn't enhance the lighting in opposite lanes over a central reservation against Klebelsberg's (1982) prediction. Once drivers pass the dark spots, they switch on lights and don't lower the optimal level of lighting even when brightness recovers.