Literature consistently finds a higher level of safety at roundabouts compared to other types of intersections. However, some studies indicate that there is still a lack of safety on rural roundabouts. Particularly high approaching speeds combined with insufficient perceptibility of roundabouts can cause accidents when drivers lose control of their vehicle (especially during nighttime). The goal of this study is to analyze correlates of safety at rural roundabouts in Germany and to investigate opportunities to improve their safety. The analysis of accident characteristics in data from official statistics shows that 60% of all accidents happen in twilight and at night time and that four out of ten accidents are single-vehicle accidents. Single-vehicle accidents have the highest severity and usually end up on the central island of roundabouts. For detailed accident analysis of 109 roundabouts, information on road design, signage, traffic volumes, and accidents was collected for each approach. Using generalized linear models, the following effects of roundabout design on accident risk were found: • Approaches with a curvilinear alignment or a chicane have significant lower accident rates than approaches with straight alignment; • Approaches with high angles of deflection have higher accident rates than approaches with moderate angles of deflection; • Wide splitter islands with triangle shape provide lower accident rates than narrow splitter islands with straight curb.4. Finally, observations of driving behavior and photometric studies were conducted at more than 30 approaches of rural roundabouts. The influence of approach alignment on speed behavior and the shape of splitter islands on track behavior proved the results obtained by the accident analysis. Photometric studies showed that the usage of retroreflective elements on the curb of the splitter island increase the visibility of rural roundabouts during the night. (Author/publisher)
Samenvatting