Development of an Illuminated Delineator using in Laser Beams

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Delineation helps to guide drivers along roadways, particularly at night or in adverse weather conditions. In dense fog, adequate visibility of the delineator is important for providing the driver with road geometry cues. The present paper proposes a new illuminated delineator that employs laser beams. Very little data has been published with regard to the visibility of laser beams in fog. However, laser beams can be expected to be highly visible in dense fog due to their high intensity, high energy, and directivity that is both monoclinic and strong. The present study was conducted in order to evaluate the visibility of laser beams in fog. The experiment was conducted in the Traffic Sign Laboratory, Public Works Research Institute, in Tsukuba, Japan. The laboratory is equipped with an observation room capable of generating artificial fog. The dimensions of the observation room are : length, 30m ; width, 10m ; and height, 10m. The effectiveness of two types of laser heads and an illuminated delineator containing two 10 W glow lamps was investigated. The dependent variables were luminance at a specific point on the laser beam and estimated brightness. The major independent variables were fog density and illuminance in the observation room. The laser beams were observed as sharp lines of light in dense fog. The visibility of the laser beams in fog had an inverse relationship to that of normal light, as indicated by Prichard and Blackwell [3]. In addition, subjects reported that the directivity of the laser beams could effectively indicate the direction of the highway. However, the visibility of the laser beams was strongly affected by the illuminance in the observation room, and care must be taken in order to prevent drivers from looking directly at redundant laser beams [7]. Based on the results of the present study, we conclude that laser beams may be useful lighting sources in dense fog if this safety problem can be overcome.