Roundabouts have proved to be effective in urban and suburban environments in the United States, but little has been reported on the effectiveness of roundabouts in rural environments on high-speed roadways. There is no question that roundabouts reduce the speeds of all vehicles at intersections and reduce the frequency of fatal and injury-related crashes. This research is the first comprehensive look at roundabouts in a rural environment with high-speed approaches. Nineteen intersections had ample comprehensive crash data to be evaluated and analyzed for safety performance. The findings validated the hypothesis that roundabouts in a rural environment as well as roundabouts in urban and suburban environments outperformed other intersection safety improvements. A before-and-after crash analysis was conducted for the 19 intersections by using a negative binomial regression model. Results showed statistically significant reductions for the total number of crashes (63%) and injury crashes (88%) when roundabouts were implemented. A before-and-after empirical Bayes estimation was also conducted, and the results were consistent, indicating a 62% to 67% reduction in total crashes and an 85% to 87% reduction in injury crashes at these rural intersections. Furthermore, results showed that injury-producing crash types, such as the angle crash, were reduced by 91%, and were statistically significant. Finally, this research produced crash prediction models at planning level for total and injury crashes at rural roundabouts on high-speed roadways. This supplements the models produced in NCHRP Report 572: Roundabouts in the United States and reported in the AASHTO Highway Safety Manual.
Statistical Analysis and Development of Crash Prediction Model for Roundabouts on High-Speed Rural Roadways
Transportation Research Record: Journal of the Transportation Research Board
2012-01-01
Article (Journal)
Electronic Resource
English
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