The Impact of Road Intersection Topology on Traffic Congestion in Urban Cities

Due to the dramatic increase in population and the rapid developments of the automobile industry, tremendous issues have emerged in road traffic systems, such as traffic congestion. In some big cities, traffic congestion occurs due to several factors, such as roadworks, car accidents, and drivers' behaviour. Consequently, it negatively impacts on environment and economy as well as on the behaviour of drivers and passengers. In this paper, we first identified the factors that may increase the journey time and listed the traffic congestion measurement metrics. Then, we investigate to reveal the relationship of road network topology to the traffic congestion level regarding travel time and the number of affected vehicles in case of traffic incidents. The open source traffic simulator SUMO (Simulation of Urban MObility) was used to simulate vehicular traffic and to generate traffic jams on the roadmap under various scenarios. These scenarios involve three road topologies which were: crossroads in Denver (CO, USA), roundabouts in Nantes (France), and hybrid topology, which is the combination of intersections and roundabouts, in Northampton town (UK). The results showed that the delayed time is less in the roundabout traffic map topology, and the number of affected vehicles in the case of traffic incidents is less likely to happen in the hybrid topology.