Overview
This study identifies 58 roundabout corridors in the United States as of 2011. There is diversity among these corridors in terms of length, roundabout spacing, number of lanes, surrounding land use, previous control (if not a new facility), and reasons for the selection of roundabouts. From this set of 58 corridors, nine were selected for more detailed study:
- MD 216 in Scaggsville, Maryland
- La Jolla Boulevard in San Diego, California
- Old Meridian Street in Carmel, Indiana
- Spring Mill Road in Carmel, Indiana
- Borgen Boulevard in Gig Harbor, Washington
- SR 539 in Whatcom County, Washington
- Golden Road in Golden, Colorado
- Avon Road in Avon, Colorado
- SR 67 in Malta, NewYork
Safety evaluations of roundabouts from other research projects indicate conversion of individual signalized and two way stop controlled intersections to roundabouts results in a reduction in the frequency and severity of crashes. Although safety data were not collected for this project, corridor interviews revealed that safety improvements with roundabout applications were generally consistent with documented research. As a result, the research team found no evidence suggesting the safety performance of a roundabout in series differs from the safety performance of an isolated roundabout. The following subsections highlight key findings for four topic areas:
- Corridor interviews
- Travel time collection, analysis, and modeling
- Comparison to equivalent signalized corridors
- Development of a Corridor Comparison Document