Comparing Traffic Performances of Turbo-roundabouts and Conventional Roundabout (Case Study)

Roundabouts are often have high traffic volume. it requires a more complex design for easy passage of the traffic flow. In the current two-track vehicles crossing roundabouts, vehicle are forced to slow down according to a geometric curvature and size of the central island, which is one of the common problems related to driver behavior along the way passing. Due to transmission lines being apart, or lack of the use of signs for route selection, the possibility of lane-changing comes up, that the percentage of side-by-side encounters increase and reduce road safety [3]. In order to reduce these problems, a new concept called the Turbo-roundabout was introduced in the Netherlands in 1996 by lambertus Fortujin, which often directional flows separated by physical separations. For these reasons, drivers have to choose their own route before entering roundabouts, so the potential of collision reduce and safety of route goes up [4]. Compared to conventional schemes, the main advantages of a turbo roundabout are:• limited number of potential conflict points among vehicular trajectories; (which you can see in Figure 1) • slower speed along the ring; • low risk of side-by side accidents. The main disadvantages are: • presence of through conflict points in left-turning maneuvers (see Fig. 2);• higher values of the critical gaps along the road, and left-turning maneuvers; • generally lower capacity than conventional double lane oundabouts [5].