INFRASTRUCTURE PLANNING REVIEW
Online ISSN : 1884-8303
Print ISSN : 0913-4034
ISSN-L : 0913-4034
Visibility of Illuminated Delineator during Fog in the Daytime
T. HagiwaraR. TokunagaY. OnoderaR. Imazu
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Keywords: ITS
JOURNAL FREE ACCESS

2001 Volume 18 Pages 809-816

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Abstract

In dense fog, sufficient visibility of road delineators is important for providing the driver with road alignment cues. However, few studies have addressed the luminance of targets in fog. The present study proposes a model to determine the luminance of a luminous delineator and the background luminance in fog. An experiment was performed over a period of 25 days at Nissho Pass on National Highway Route 274 in Hokkaido, Japan, in 1998. A vehicle equipped with two luminance meters and a data-recording system was used as a data measuring station. Luminance, illuminance and transmissivity in fog were simultaneously recorded at intervals of 1 minute. The car headlights were kept on throughout the experiment. The luminous delineator used in the experiment was one used in Hokkaido, and the observation distance between the luminous delineator and the luminance meter was 31.5 meters. A black board was used as the background. 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. R-squared was 0.878. The luminance of the luminous delineator was estimated by adding the attenuated luminance to the background luminance. The value of R-squared was 0.883. No distortion was visible, and errors were distributed normally. It was found that the visibility level of the luminous delineator under various conditions in daytime fog can be derived using this model if the visual range, illuminance and observed distance are given. For example, at a visual range of 50 meters, observation distance of 50 meters and illuminance of 50001x, the visibility level of the luminous delineator was less than 1. The present study indicated that the luminance of the targets in daytime fog could be estimated using a model that accounted for background luminance. In addition, according to the model, the luminous delineators should be closer to the driver in order to reduce the required lamp power, and should be arranged at short intervals.

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© by Japan Society of Civil Engineers
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