Module 1 Introduction

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Roundabouts Intersections Designed for Safety
Photo Mt. Horeb, WI
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Roundabout Workshop
Module 1 - Introduction Instructors Fred Ranck,
Safety Engineer fred.ranck_at_fhwa.dot.gov
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Self Introductions

• - Who you are
• - Who you work for and what you do
• - What roundabout issues are you currently
  working on or looking for more information on?

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Logistics

• Workshop materials
• Please turn off cell phones/pagers
• Breaks and Lunch
• Please ask questions
• Other site-specific issues

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Workshop Overview

• Module 1 - Introduction
• Module 2 - Safety
• Module 3 Planning and Policy Considerations
• Module 4 - Operations
• Module 5 - Geometric Design
• Module 6 Signing and Marking
• Module 7 - Lighting and Landscaping
• Module 8 - System Considerations

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The Evolution of the Modern Roundabout

• 1900s to 1940s Rotaries and Traffic Circles
• Columbus Circle in NYC was the first
• 1950s Circular intersections out of favor
• 1963 Great Britain redesigns circular ints.
• 1980s Modern Roundabouts used extensively in
  Europe and Australia
• 1990s Modern Roundabouts built in US

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What is a Roundabout?

• MUTCD Definition
• a circular intersection with yield control of
  all entering traffic, channelized approaches, and
  appropriate geometric curvature, such that travel
  speeds on the circulatory roadway are typically
  less than 50 km/h (30 mph).

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Another Reference
AASHTO Policy on Geometric Design (The Green
Book)

• Modern roundabouts are defined by two basic
  operational and design principles
• - Yield-at-Entry
• - Deflection of Entering Traffic

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Roundabouts are a subset of circular intersections
All circularintersections
Roundabouts
Others
Rotaries
Neighborhoodtraffic circles
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Elements of a Roundabout
Source Kansas Roundabout Guide
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Rotaries are not Roundabouts
Dupont Circle, Washington, DC (Not a Roundabout)
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Reconstruction of Rotaryto a Roundabout
Kingston, NY - Photo Source NYSDOT
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Large Traffic Circles are not Modern Roundabouts
Tallmadge Circle
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Traffic Calming Circles are not Roundabouts
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Examples of traffic calming circles
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Examples of traffic circle inconsistencies
Parking
Stop Control
Right-of-Way Control of traffic on circular
roadway
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Roundabouts An Informational Guide

• Chapter 1 - Introduction
• Chapter 2 - Policy Considerations
• Chapter 3 - Planning
• Chapter 4 - Operation
• Chapter 5 - Safety
• Chapter 6 - Geometric Design
• Chapter 7 - Traffic Design and Landscaping
• Chapter 8 - System Considerations

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State Supplements to FHWA Guide

• Several states have developed state standards or
  supplementary material to FHWA Guide, including
• Arizona
• Kansas
• Maryland
• Missouri
• New York
• Oregon
• Pennsylvania
• Washington
• Wisconsin

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Other References

• NCHRP Project 03-65 Applying Roundabouts in the
  United States
• Highway Design Handbook for Older Drivers and
  Pedestrians (FHWA-RD-01-103)
• The Illumination of Roundabout Intersections
  Technical Guide

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Roundabout Categories Based on environment, size,
and number of lanes
Urban / Suburban Mini-Roundabout Compact Single
Lane Double Lane Rural Single Lane Double Lane
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Comparison of Roundabout Categories
Page 13
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Mini-Roundabout
Max Entry Design Speed15 MPHICD 45 80 ft
Splitter Island Raised if possibleVolume
(4-leg) 10,000 vpd
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Mini Roundabouts
Germany
Dimondale, MI
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Urban Compact Design
Entry Design Speed15 mphICD 80 - 100 ft
Splitter Island Raised w/cutVolume (4-leg)
15,000 vpd
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Urban Compact RoundaboutExamples
West Boca Raton, FL
Santa Barbara, CA
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Urban Single-Lane
Entry Design Speed 20 mphICD 100 - 130 ft
Splitter Island Raised w/cutVolume (4-leg)
20,000 vpd
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Urban Single-Lane Roundabout Examples
La Jolla, CA
Summit County, Ohio
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Urban Double-Lane Design
Entry Design Speed25 mphICD 150 - 180 ft
Splitter Island Raised w/cutVolume (4-leg)
40,000 vpd
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Urban Double- and Multi-Lane Roundabout Examples
Coral Gables, FL
Avon, CO
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Rural Single-Lane
Entry Design Speed25 mphICD 115 130 ft
Splitter Raised, extended w/cutVolume (4-leg)
20,000 vpd
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Rural Single-Lane Roundabout Examples
Lisbon, MD
Leeds, MD
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Rural Multi-Lane
Entry Design Speed 30 mphICD 180 - 200 ft
Splitter Island Raised, extended w/cutVolume
(4-leg) 40,000
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Rural Multi-Lane Roundabout Example
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QUESTIONS?