Case Study: Capacity Characteristics Comparison of Single-lane Roundabout and Turbo-roundabouts

Turbo-roundabouts are new type of roundabouts that recently become more popular for their significant advantages. Due to their specific geometry of spiral leading circulatory lanes and raised lane dividers provide a high level of traffic safety while a relatively large capacity maintain. To compare with conventional double-lane roundabouts, turbo-roundabouts ensure above all a reduced number of conflict points moreover without waving and lower driving speed through the intersection. Challenge of this paper is to transfer existing single-lane roundabout into configuration models of basic and egg turbo-roundabouts and compare their capacity characteristics. Case study is placed in Zilina, the city on the north of Slovakia, where the single lane roundabout has a great congestion problem not just during peak hours. Configurations of the roundabout are evaluated and compared from their performance parameters using microsimulations and theoretical models. For calibration procedure of microsimulation, complex data obtained from survey of existing roundabout were used and derived as input variables for two new configurations. This example is to demonstrate the capacity increase of turbo-roundabouts comparing with single-lane roundabout and the comparison of microsimulation model and theoretical models to determine capacity of turbo-roundabouts.