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Hillary Isebrands, P.E.
Iowa State UniversityCenter for Transportation Research and Education
Rural Roundabouts: An International Perspective
Photo Credits: Isebrands unless otherwise notedPaola, KS
Iowa State UniversityTransportation Seminar, Spring 2007
January 12, 2007
o Traffic Circles – 1905
o Modern Roundabout – UK 1960’s
o Europe
o Midwest – 1990’s
Kingston, NY Source: McCulloch
History of Circular Intersections
Modern Roundabouts
Source: Roundabouts: An Informational Guide, FHWA, 2000
o Reduction in crash severity
o Speed reduction
o Improved capacity
o Reduction in queues and delays
o Reduction in emissions
o Maintenance costs lower
o Aestheticso Suitable for most
locations and traffic volumes
o Traffic calming
Benefits of Modern Roundabouts
Paola, KS
o Crash Reduction in the US (Persaud et al, 2001)
o 23 Intersections
o All crashes - 40%
o Injury Crashes - 80%
o Consistent with internationally studies
Safety
Operations
Safety
Rural Urban
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United Kingdom
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France
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France
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France
Italy
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United States
States Actively Implementing Rural Roundabouts
Source: NE Roundabouts
Kansas DOT
Paola, KS
Paola, KS Paola, KS
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Paola, KS Garnett, KS
Minnesota DOT
New Prague, MN
State Highway 13 and County Rd 2 - Scott County, MN
Source: FHWA/MnDOT
Medford, MN Rising Sun, MD
Maryland DOT
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Rising Sun, MDRising Sun, MD Rising Sun, MD
Rising Sun, MDHarford County, MD
Lothian, MD Lothian, MDLothian, MD
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Lothian, MD
Verboot, OR
Washington County Oregon
Washington DOT
Duvall, WA Duvall, WA
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Duvall, WA Duvall, WA
1 Maycock and Hall, “Accidents at 4-arm Roundabouts” 19842 WSDOT Accident Records and WSDOT Traffic Counts3 Projections from RODEL Ltd.Source: Washington DOT
19.1916.522.540.13ProjectedRoundabout3
13,700192.262.329.90.0Novelty Hill Road,Existing2
20,400851.539.211.80.56Signals45-55 mph2
27,8001128.724.73.80.19Roundabouts50–70 mph1
AverageDaily Traffic
Number ofSites
TotalSlightSeriousFatal
Injury Accidents per 100 Million VehiclesCategory
Injury Accident Statistics High-Speed Roundabouts vs. High-Speed Signals
Duvall, WA Source: WA DOT
Discussion/Questions
Hillary N. Isebrands
Thank You
Gratzie
Merci
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