Evaluation of Roundabout Performance Using SIDRA

Abstract

This paper compares the performance of roundabouts with four leg intersections under yield control, two- and four-way stop control, and signal control for various traffic conditions using the SIDRA package. Such conditions include variations in volume levels, turning volume splits, number of approach lanes, and lane widths. The results from the analysis indicate that roundabouts are the best alternative designs for intersections with two-lane approaches that carry heavy through and/or left traffic turning volumes. The perfor- mance of roundabouts compares well to the performance of signalized intersections with one-lane approaches and heavy traffic volumes. Roundabout capacities are found higher than capacities of signal controlled intersec- tions with two- and three-lane approaches for any proportion of left-turning traffic volume. This study provides recommendations to traffic engineers on the conditions under which roundabouts perform better than controlled intersections and, thus, should be considered as design alternatives.