| Recently、 modern roundabouts have been actively introduced in various countries. Single-lane[*] roundabouts help to prevent serious accidents because vehicles tend to slow down due to 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、 while a large diameter helped[*] them to stay on course and reduced travel position variations. 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、 while the island diameter had a smaller[*] impact. It was thus 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 winter in snowy cold regions. |
