Abstract
Recently, modern roundabouts have been actively introduced in various countries. Single-lane roundabouts help to prevent serious accidents because vehicles tend to slow down as a result of the transverse acceleration that acts on them during movement on the circulatory roadway. However, as the boundary between the circulatory roadway and the truck apron becomes unclear during winter in snowy cold regions, it is necessary to verify the practicality of roundabouts in consideration of winter road surface and meteorological conditions. This study examined a method of guiding vehicles on circulatory roadways in winter. Driving experiments were conducted at a roundabout with different road surface conditions and central-island diameters to allow analysis of the positions of vehicles traveling under each set of conditions. The results indicated that vehicles were able to stay on course regardless of the central-island diameter in dry road surface conditions. With winter road surface conditions, however, the number of vehicles mounting the truck apron increased when the island diameter was small, whereas a large diameter helped them to stay on course and reduced travel position variance. An examination of driving behavior under different road surface conditions and with different central-island diameters revealed that surface conditions affected travel speed and transverse acceleration, whereas the island diameter had a smaller effect. However, it was found that the adoption of a large central-island diameter in a constant inscribed circle diameter was effective in reducing travel position deviation and helped vehicles to stay on the circulatory roadway even during the winter in snowy cold regions.
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