ABSTRACT
For in-service roundabouts where traffic volume has changed since design, road marking is an important factor affecting the safety and capacity of roundabouts. The principal aim of this study is to investigate the influence of road markings, truck apron, and shape of the central island on total and truck accidents. The results indicate that, the highest rate of total and truck accidents for the selected roundabouts were recorded for concentric-spiral marking, followed by spiral, partial- concentric, concentric, and roundabouts with no markings. The majority of the selected roundabouts have oval shape and they have higher rate of total accidents and truck accidents, than circular shape roundabouts. In addition, only three of the selected roundabouts have truck aprons and the rate of truck accidents are high in these locations.
