| On winter roads in cold、 snowy regions、 visibility in snowstorm conditions is measured using dedicated optical meters for the improvement of measures against poor visibility during snowstorms and for road traffic control. However、 current measurement of visibility on roads is based on the meteorological definition (the maximum distance from which a black target occupying 0.5 - 5 degrees of visual angle can be recognized)、 and does not necessarily correspond to the distance from which roads and objects on them are visible. Accordingly、 it is considered necessary to establish visibility measurement and assessment methods that are more suitable for roads during snowstorms.[*] In this study、 the differences and relationships between values measured using an optical visibility meter during snowstorms on a road and the actual visibility range of delineators and vehicles as targets on the road were investigated in order to present a method for assessing visibility during snowstorms on roads. [*] The survey results revealed that the visibility range of the delineating facilities (snow poles and fixed-post delineators with arrow-shaped pointers) tended to be similar to or shorter than the values measured using the visibility meter. The vehicle bodies、 taillights and headlights were not visible to the subjects at a distance similar to the visual range measured using the visibility meter、 and remained imperceptible to many drivers even when placed closer to them. This indicated that the actual vehicle visibility range tended to be shorter than the values measured using the visibility meter. |
