EVALUATION OF PERFORMANCE OF MODERN ROUNDABOUTS USING PARAMICS MICRO-SIMULATION MODEL

Use of modern roundabouts as a viable traffic control measure instead of traffic signals or priority intersections is increasing in many jurisdictions in North America. Their strength lies in their ability to reduce the number of vehicular conflicts at intersections and thereby enhance intersection capacity and safety. There are additional intangible benefits of roundabouts such as their traffic calming effect, gateway feature and aesthetics. Although on the rise, adoption of modern roundabouts as a common intersection form is hindered by the general lack of suitable analysis tools that can be used to evaluate their operational performance and thereby facilitate an objective comparison between them and other intersection control strategies. This study investigated the viability of using Paramics micro-simulation model in evaluation of operational performance of roundabouts. The Paramics model is an advanced micro-simulation tool with capabilities of modelling both roundabout and traffic signals to acceptable level of detail. Motion of an individual vehicle is simulated in small time steps and each vehicle is followed from the time it is generated into the network to the point of its exit. Vehicular behaviour at roundabouts is modelled on the basis of a gap acceptance approach. Drawing from recent experiences, the paper reviews the practical steps and efforts required to model a modern roundabout and compare it with a traffic signal alternative in a typical Canadian urban environment using the Paramics model. It describes the model’s ability to capture the effects of various geometric and traffic features like approach angle, inscribed circle, number of circulatory lanes, position of the stop line and proportion of turning flows, and evaluates their impacts on the resulting capacities. However, because Paramics is a lane based model, it was unable to analyze the effects of entry width. Evaluation of the results indicates that the model is able to capture most of the important features of a roundabout and provides a good basis for comparing their operational performance to that of other intersection forms. KEY WORDS: Roundabout, traffic analysis, micro-simulation modeling