Study Details

Study Title: Performance Evaluation of Roundabouts for Traffic Flow Improvements and Crash Reductions at a Highway Interchange in Oxford, MS

Authors: Uddin, Headrick, and Sullivan

Publication Date: JAN, 2012

Abstract: Due to increased traffic volume and congestion, conflicting movements, and capacity limitations, two roundabouts have been constructed by converting the existing signalized intersection in the north and stop controlled intersections in the south side on South Lamar Boulevard and MS Highway 6 Interchange in Oxford, MS. The overall objective of this study was to assess the performance of the roundabouts in Oxford with respect to traffic flow, capacity, safety improvements, and a public opinion survey. Detailed post-roundabout traffic movement volume and crash data were collected and compared with the pre-roundabout data to assess the in-service performance of these roundabouts. The results of the Oxford roundabout study showed significant improvement in traffic flow, crash reduction, and reduction in vehicle emissions. It was found that the conversion of the intersections to roundabouts improved traffic flow by reducing average delay by 24%, idling time by 77%, and fuel wastage by 56%. Overall vehicle emissions from idling were reduced significantly. The roundabout conversion increased the mean speed on the South Lamar interchange by 67% and improved level of service for both roundabouts. The roundabout junctions improved safety performance through: a 37.5% reduction in crashes and a 60% reduction in the number of crashes resulting in injury. The reduction in overall crashes in the study area reduced comprehensive cost by 54.4%. Additional user cost savings of $806,071 were calculated annually from reductions in travel time and fuel wastage. These benefits paid off the total construction cost of the roundabouts within two years. The anonymous public opinion survey overwhelmingly shows favorable results and provides support to build more roundabout junctions in place of stop-controlled intersections. The study results indicate that roundabouts are performing well as intended. It is a preferable solution to improve capacity and safety compared to signal control and stop controlled intersections.

Study Citation: Uddin, W., J. Headrick, and J.S. Sullivan. "Performance Evaluation of Roundabouts for Traffic Flow Improvements and Crash Reductions at a Highway Interchange in Oxford, MS." Transportation Research Board 91st Annual Meeting Compendium of Papers, Washington, D.C., 2012.

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Intersection geometry

Countermeasure: Convert signalized intersection to modern roundabout

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.625 37.5 3 Stars All All Principal Arterial Other Rural
0.4 60 3 Stars All A,B,C Principal Arterial Other Rural