Nebraska LTAP


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Khattak, A., Thompson, E., Zhao, E. "Investigation of Rural/Suburban High-Speed Multilane Roundabouts" (2014) Nebraska Department of Roads Research Report


This research was focused on two issues related to multilane roundabouts on high-speed highways (speed limit 45 mph or greater) in rural and suburban areas. The first was the tradeoff between converting a traditional stop-controlled or signalized intersection to a multilane roundabout while the second was the safety of newly constructed high-speed multilane roundabouts in rural and suburban areas. The research team reviewed information from diverse published documents and conducted a survey of state and local transportation agencies. Crash data on multilane rural roundabouts were not available for this research. Therefore, the research team relied on crash and other data for single lane roundabouts that were constructed to replace rural two-way stop-controlled intersections in Kansas. To gain further insights into the safety of rural multilane roundabouts, the research team focused on investigating the safety of urban multilane roundabouts from published sources. Results of the survey indicated the need for proper design of roundabouts including signage and lighting and the potential for gaining benefits from public informational campaigns. Results of the Kansas data analysis of single lane roundabouts showed that overall all types of crashes were reduced after conversion of TWSC intersections to modern single lane roundabouts. Total crashes decreased by 58.13%; fatal crashes were reduced by 100% at all locations and non-fatal injury crashes were reduced with an overall reduction rate of 76.47%. Property-damage-only crashes were reduced by 35.49% as a whole, but two out of the four analyzed sites experienced increases in property-damage-only crashes after conversion to roundabouts. The annual value of the reduction in comprehensive crash costs from conversion of a two-way stop-controlled intersection on a rural, high-speed highway to a single lane modern roundabout was between $1.0 million and $1.6 million in 2014 dollars. A review of multilane roundabout conversions (mostly in urban areas) showed safety improvements compared to signalized and two-way stop-controlled intersections. Recommendations are presented in the report.