This report presents a series of research findings from an investigation into roundabout operations. This includes a comparison of several analysis tools for estimating roundabout performance (the Highway Capacity Manual, SIDRA, ARCADY, VISSIM, and SimTraffic); a measurement of rejected headways for the purpose of analyzing critical headway; a review of roundabout lighting practices; and a review of considerations for roundabout site selection. It was found that VISSIM and SIDRA provided the most reliable predictions of roundabout performance for the test site analyzed herein. Additionally, the critical headways measured at this site were significantly lower (at a median value of 2.2 seconds) than other values published in the literature, with driving populations less acquainted with roundabouts. Additionally, a site selection procedure is developed based on a survey of peer agency practices and a checklist is provided for assisting in the determination of whether roundabout control is a feasible alternative for a location. Finally, based upon a review of the literature and practices commonly followed by peer states, we recommend that roundabouts be lighted.

Report Number



roundabouts, traffic control, roundabout lighting, roundabout software, roundabout capacity, gap acceptance

SPR Number


Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, Indiana

Date of this Version


Appendix A.pdf (2133 kB)
Appendix B.pdf (1532 kB)
Appendix C.pdf (1636 kB)
Appendix D.pdf (136 kB)
Appendix E.pdf (1177 kB)
Technical Summary.pdf (1431 kB)