Ken'etsu UCHIDA Research Associate

Abstract: In dense fog, the visibility of a vehicle's rear lamps is of fundamental importance. However, few studies have addressed the visibility of rear fog lamps in daytime fog. The present study evaluates the contrasts of tail lamps, brake lamps and rear fog lamps. An experiment was performed in 2001 at a parking lot on Mt. Fuji Parkway in Japan. A vehicle equipped with a data-recording system was used as the data measurement station. Luminance, illuminance and transmissivity in fog were simultaneously recorded at intervals of 2 minutes. Three types of tail lamp, three types of brake lamp and two types of rear fog lamp were used, with an observation distance of 50.0 m. The recorded data showed the background luminance in fog to be affected by illuminance and transmissivity in the daytime. A multiple regression model was applied to determine the background luminance. Contrasts were calculated using this model. Tail lamp visibility was low in deep fog in daytime. Under the same conditions, the rear fog lamps had higher visibility than both the tail lamps and the brake lamps. It was found that the rear fog lamps could provide sufficient visibility in daytime fog