1. Active Traffic Alternatives
Modern Roundabouts
James H. Ito, P.E.
11/20/2018
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2. Active Traffic Alternatives
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.
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3. Active Traffic Alternatives
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
Today, I want to introduce you to Modern Roundabouts
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4. What is a Modern Roundabout?
Modern Roundabouts are part of the Family of Circular Intersections
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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
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7. Active Traffic Alternatives
French Roundabout
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8. Why Build Modern Roundabouts? They Enhance Safety & Reduce Delay
Conflict Points Reduced
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10. Why Build Modern Roundabouts? They Enhance Safety & Reduce Delay
Conflict Points Reduced
Crash Reduction Statistics
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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
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13. Why Build Modern Roundabouts? They Enhance Safety & Reduce Delay
Conflict Points Reduced
Crash Reduction Statistics
Traffic Delays Minimized
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What Do They Look Like?
Howard Roundabouts
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Cardinal Lane (N-S) and Lineville Road, County Trunk M (E-W)
Forest Glen Elementary School
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Cardinal Lane and Lineville Road looking NE
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Rockwell Lane (N leg) and Lineville Road, County Truck M (E-W)
Bayview Middle School to the east and New High School to the north
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What Do They Look Like?
Howard Roundabouts
Proposed Roundabout in Milwaukee
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21. Active Traffic Alternatives
What Do They Look Like?
Howard Roundabouts
Proposed Roundabout in Milwaukee
Proposed Roundabout in Mount Horeb
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What Do They Look Like?
Howard Roundabouts
Proposed Roundabout in Milwaukee
Proposed Roundabout in Mount Horeb
Proposed Roundabout in Brookfield
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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
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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
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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
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Who To Contact?
Ray Smith, Brown County Highway Department,
Mark Johnson, Wisconsin DOT, District 1,
James Ito, City of Milwaukee, DPW,
Your BOTS Regional Program Manager
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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
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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.
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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.
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50. Active Traffic Alternatives
QUESTIONS?
COMMENTS?
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