Roundabouts are increasingly recognized as an intersection control strategy that can fulfill multiple performance goals related to traffic operation and safety, and meet societal goals related to sustainability, livability, complete streets, context sensitive design, economic development, and others. Some transportation agencies have recently constructed or approved the use of a series of roundabouts on an arterial rather than the traditional solution of coordinated signalized intersections. While there are anecdotal reports suggesting that functionally interdependent roundabouts on a corridor are successful in meeting performance goals, little research has been conducted to determine objectively the efficacy of this alternative as compared to signalized intersections. The performance of traffic signal systems on arterials is well researched and documented, and methods to predict their performance are well established. Performance measures for isolated roundabouts exist and safety research has consistently shown that signalized intersections have higher injury crash rates when compared to roundabouts. In contrast, qualitative and quantitative information on the performance of a set of functionally interdependent roundabouts on arterials is lacking.
The objective of this research was to provide traffic engineers, transportation planners, and other practitioners with performance measurement and evaluation methods to evaluate comprehensively the performance of functionally interdependent roundabouts on arterials, thus enabling a comparison with signalized intersections, in order to arrive at a design solution. For purposes of this research, a "series of roundabouts" includes at least three roundabouts that function interdependently on an arterial.
STATUS: The research has been published as NCHRP Report 772 Evaluating the Performance of Corridors with Roundabouts and is available HERE. Presentation materials that provide an overview of the research and the results may be downloaded HERE
Appendices containing detailed field data are available:
Appendices B through J are available HERE
Appendix K is available HERE
Appendices L through O are available HERE