Optimizing the Performance of Traffic Squares by Simulating Different Scenarios of adding Traffic Signals (Case Study: Valiasr and Ferdowsi Square, Tehran)

Control of traffic performance just via right of way regulations, causes the forming of long queues along the entry approaches of roundabout while results in decreasing the capacity of roundabout and also increasing the delay time of network. The idea of signalization of roundabouts can be useful as a counteraction for this problem, especially during peak hours. In this case, determining the type of control, phasing and timing of the traffic signals and also defining a pattern in signalization of roundabouts in order to select the best alternative of traffic signals operation in roundabout and reach to optimal results, is the one of the problems that seems to be facing traffic engineers when signalizing roundabouts. In this paper, to evaluate the performance of traffic signals at roundabouts with high flow rates and in order to find the suitable scenario for signalization of roundabout to improve the traffic condition, Valiasr-square which is one of the densest roundabouts in Tehran, as main case study model and Ferdosi-square, as validation case study model, are modeled and simulated in traffic simulator software AIMSUN. According to the results obtained for valiasr-Square includes a 32% reduction in delay time, 17% reduction in density, 13% increase in flow, 48% increase in speed and 17% reduction in total travel time while installation of traffic signal in its optimal scenario, it can be said that the use of traffic signals at roundabouts with high traffic volumes is a good choice to get more traffic flow and fewer delays.