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Modern Roundabouts

Modern Roundabouts. James H. Ito, P.E. Introduction. Modern Roundabouts became an effective Traffic Control strategy in 1966 when the British adopted the “Yield upon Entry” rule.

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Modern Roundabouts

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  1. Modern Roundabouts James H. Ito, P.E. Active Traffic Alternatives

  2. Introduction • Modern Roundabouts became an effective Traffic Control strategy in 1966 when the British adopted the “Yield upon Entry” rule. • I am currently the Traffic and Lighting Traffic and Lighting Design Engineer for the City of Milwaukee and the President of Active Traffic Alternatives. Active Traffic Alternatives

  3. Topics of Discussion • I will identify the distinguishing features of Modern Roundabouts • You will learn why Modern Roundabouts are being built • You will see images of Wisconsin’s Modern Roundabouts, those in use and some of those proposed Active Traffic Alternatives

  4. What is a Modern Roundabout? • Modern Roundabouts are part of the Family of Circular Intersections Active Traffic Alternatives

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  6. What is a Modern Roundabout? • Modern Roundabouts are part of the Family of Circular Intersections • Distinguishing Features • Yield at Entry • Speed Control by Deflection Active Traffic Alternatives

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  8. Why Build Modern Roundabouts?They Enhance Safety & Reduce Delay • Conflict Points Reduced Active Traffic Alternatives

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  10. Why Build Modern Roundabouts?They Enhance Safety & Reduce Delay • Conflict Points Reduced • Crash Reduction Statistics Active Traffic Alternatives

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  12. Before and After Results for 24 Intersections in US Converted from Stop Sign or Traffic Signal Control to Modern Roundabouts • 89% Reduction in Fatal and Incapacitating Injury Crashes • 76% Reduction in All Injury Crashes • 39% Reduction for All Crashes Active Traffic Alternatives

  13. Why Build Modern Roundabouts?They Enhance Safety & Reduce Delay • Conflict Points Reduced • Crash Reduction Statistics • Traffic Delays Minimized Active Traffic Alternatives

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  15. What Do They Look Like? • Howard Roundabouts Active Traffic Alternatives

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  19. What Do They Look Like? • Howard Roundabouts • Proposed Roundabout in Milwaukee Active Traffic Alternatives

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  21. What Do They Look Like? • Howard Roundabouts • Proposed Roundabout in Milwaukee • Proposed Roundabout in Mount Horeb Active Traffic Alternatives

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  23. What Do They Look Like? • Howard Roundabouts • Proposed Roundabout in Milwaukee • Proposed Roundabout in Mount Horeb • Proposed Roundabout in Brookfield Active Traffic Alternatives

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  25. Traffic Control Panacea? • Modern Roundabouts should not be used in a Traffic Signal System • Modern Roundabouts can be installed next to Signalized intersections • Modern Roundabouts complement Traffic Calming Devices • Modern Roundabouts enhance Street Landscaping and are often used to create Area Gateways Active Traffic Alternatives

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  28. What This Means • Modern Roundabouts offer Communities and Neighborhoods an Attractive, Safe, and Efficient form of Traffic Control • Modern Roundabouts can be more Efficient and Safer than traffic signals • Modern Roundabouts should not be used in a Traffic Signal System Active Traffic Alternatives

  29. What Has Happened • Wisconsin Department of Transportation, Bureau of Transportation Safety funded Training, 1998 through 2001 • Howard Modern Roundabouts have been constructed • Roundabouts have been designed for several Wisconsin locations • Wisconsin DOT has an Engineer on staff with Modern Roundabout Design Experience from Colorado Active Traffic Alternatives

  30. Who To Contact? • Ray Smith, Brown County Highway Department, 920-492-4925 • Mark Johnson, Wisconsin DOT, District 1, 608-246-3842 • James Ito, City of Milwaukee, DPW, 414-286-3263 • Your BOTS Regional Program Manager Active Traffic Alternatives

  31. Geometric Design Recommendations • Iterative Process • Hand Sketching Preliminary Designs • Fastest Vehicle Paths • Truck Swept Paths • Radial Alignment of Entries • Vehicle Path Overlap • Extended Splitter Island Treatment • Successive Curves on HS Approach Active Traffic Alternatives

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  48. Capacity Software • ARCADY – British method with 50 % confidence limits. Capacities predicted have been measured. Has crash prediction module. • RODEL – Same as ARCADY but with user specified confidence limits. • SIDRA – Australian method based on gap acceptance processes. Active Traffic Alternatives

  49. Simulation Models • Simulation model results are best used for relative comparisons. • Do not conclude that the values found from the model are the same as field data. • Perform sensitivity analysis by changing selected parameters over a range and comparing results. Active Traffic Alternatives

  50. QUESTIONS? COMMENTS? Active Traffic Alternatives

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