In this study, focus was placed on fog as a factor's role in reduced visibility, and an experiment was conducted to evaluate the visibility of LED delineators under natural foggy conditions. The experiment was conducted over a period of the two months of July and August 2004 on Marine Street, a municipal thoroughfare public road in Shiranuka, Hokkaido, using three types of LED delineator. Twenty subjects were tested in three cases each during the day and at nighttime (one under clear and two under foggy conditions). The subjective visibility and glare of LED delineators were evaluated using seven- and five-level scales respectively. Based on the test results, the luminous intensity of LED delineators required under differentfog conditions was simulated depending on the road service speed. It wasrevealed that, at a service speed of 60 km/h in fog with a visibility of 100 m, the recommended luminous intensity was found to be approximately 2.2 - 102 to 8.5 - 102 cd during the day and 1.2 - 10 to 4.3 - 10 cd at nighttime.
Abstract