Developing a capacity model of normal roundabouts based on simultaneous geometric and traffic parameters using microscopic simulation

Document Type : Research Paper


1 M.Sc graduated, Department of civil engineering, Kharazmi University, No.43.South Mofatteh Ave. Tehran, Iran,

2 University of Kharazmi,Faculty of Engineering


One of the types of unsignalized intersections is roundabout, which usually has an advantage in terms of efficiency and safety in low to medium traffic conditions. In general, roundabouts are created as a solution to solve traffic problems at intersections, as well as to create ease and safety in weaving movements. As the volume of traffic increases and according to the dimensions and geometric design of the roundabout, its efficiency gradually decreases. Considering the issue of road traffic due to its globalization, it is necessary to develop a transportation network that can be efficient now and in the future. To this aim, proper design and analysis of various infrastructures are performed. One of these infrastructures created in the road network to increase the efficiency of intersections by reducing delay is roundabout. At present, a strong model for Iran's traffic conditions is not available to determine the performance of roundabouts; Therefore, in this research, an attempt has been made to prepare a model to determine the performance of roundabouts based on geometric characteristics. Among the available global models, it has been observed that the geometric characteristics of roundabouts play an important role in roundabout capacity. Therefore, concerning this issue as a basis, a model for roundabout entry capacity has been produced for heterogeneous traffic conditions in Iran. According to the research results, the entry capacity model, which is described by the variables 1- circulating flow, 2- central island diameter, and weaving width, is the best in terms of statistics has been the best model statistically. It was observed that with each meter increase in the diameter of the central island, the entry capacity of the roundabout increased by 6%. Also, with each meter of weaving width, the entry capacity has increased by 35%.


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