ROUNDABOUT INTERSECTIONS: EVALUATION OF GEOMETRIC AND BEHAVIOURAL FEATURES WITH VISSIM

Abstract

In the literature, there are many methodologies that allow the evaluation of roundabout performances (Capacity, Levels Of Service, etc): analytical models (HCM, HBS etc.), statistical models (TRRL, SETRA) etc. Each technique considers some aspects of the roundabout in comparison to others (geometric elements, vehicular flow and behavioural parameters). Obtained results are often not comparable among themselves because of distinctive peculiarities of each method. Today, the best way to solve this problem is by using a refined simulation software of vehicular circulation. In this paper the authors introduce the results of a wide survey conducted on an ample range of roundabout scenarios by the use of the simulation software VISSIM. Each scenario describes a fixed roundabout phenomenon using the following variables: geometric elements (inscribed circle radius, circulatory roadway, central and splitter islands etc.); characteristics of the traffic flow (dynamic traffic assignment, approach speed, circulatory speed and reduced speed zones, etc.); behavioral features (priority rules, minimum gap, minimum headway, etc.). The results are presented from the evaluation of stop-line delays.