Performance analysis of roundabout junction in Duhok with proposed si̇gnali̇zed one through VISSIM software

Traffic congestion is one of the major sources and reasons of traffic delay, and with increasing number of vehicles annually, this further complicates the situation. While Roundabouts have the unique advantage and capability of contributing to the reduction of congestion by providing traffic flow in one direction around central island and giving priority to the circulating flow, at the same time they were originally designed to accommodate intersections and junctions that had moderate traffic volumes, so with increasing number of vehicles and thus traffic, this situation raises further questions about whether roundabouts will be suitable for accommodating certain junctions in the foreseeable future. In the United Kingdom, for example, after many researches and studies many roundabouts have been converted to signalized junctions over the past decade as the growth of vehicles and population made it overwhelming for them to accommodate traffic. In this research, a decision will be made regarding Gali Roundabout in Duhok, Iraq, whether this junction should be converted to a signalized junction or remain as it is. To reach this aim, several objectives are required to be carried out manually such as obtaining geometrical properties of the Roundabout, obtaining hourly Traffic Volume Count, and via the ever reliable VISSIM software, Average queue length, travel time delay and so on. After triggering some simulations through VISSIM, the software, will aid in the projection. Hypothetic simulations will also be conducted on VISSIM where it is assumed if the number of vehicles entering the roundabout in the future increases by 15%, this will compare with the performance of the roundabout in present time and will thus provide a breakthrough whether the usage of roundabout will be sustainable or not. VISSIM analysis ultimately projects that this roundabout, if it were to be converted to a signalized junction would cause more congestion and increasing travel time delay. It does however also recommend that the roundabout should have a much wider ICD in 5 years time but due to the roundabouts location, which is being nearby a mountain, topographic reasons will likely be an obstacle of performing any changes to its geometrical properties. So this roundabout may be shifted or displaced 200-300m from its original location and then changes to its geometrical elements and properties can be then applied.