Effectiveness of unconventional roundabouts in the design of suburban intersections

The paper focuses on the use of non-conventional roundabouts, such as turbo-roundabouts and flowerroundabouts, for the reduction of both functional and safety critical issues. The aim is to evaluate the effectiveness of non-conventional design schemes compared to conventional solutions through the implementation of vehicular traffic microsimulation techniques and swept path analysis. The work proposes two case studies in suburban areas characterized by the presence of road intersections affected by high traffic criticality. The study compares the performance in terms of average speed, queues length, time loss, vehicle manoeuvring size, etc., between the actual state and two design solutions, respectively conventional and non-conventional. The results obtained highlight the effectiveness of the non-conventional schemes adopted for both the improvement of traffic and safety parameters and for the containment of polluting emissions into the atmosphere. The work also proposes a methodological approach that can be pursued by the road designer, for the choice between alternative design solutions of conventional and non-conventional roundabout intersections.