INTRODUCTION
In spite of the great advantages of standard roundabouts over signal or stop intersections, roundabout’s properties cannot deal with both the safety and capacity issues of each intersection. Priority roundabout can be considered as a suitable design for any intersection that has high ratio of turning vehicles, in which the roundabout could improve their safety and traffic flow. However, due to its disadvantages, for example the pedestrian’s uncontrolled crossings and its insufficiency under the existence of unbalanced traffic flows, when sometimes could cause intersection redesign. In this situation, there is a good solution to integrate signal control systems with roundabout geometry in order to achieve both of the strengths signalization and roundabout geometry simultaneously. In spite of the fact that roundabouts signalization has the potential to enhance the traffic condition at plenty of the existing roundabouts, in reality, it has not been used extensively yet.
In addition, among the few signalized roundabouts, the design of these roundabouts has been with little or no formal experience (Stevens, 2005).