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Roundabouts
The Virginia Experience
Purpose of Briefing
• Background on Roundabouts
• How they pertain to Virginia
• Definition & Operational Characteristics
• Roundabouts Vs. Traffic signals
• Considerations for Roundabouts
• Review Process
Misconceptions
• Roundabouts have been around forever
• Roundabouts are unsafe to Pedestrians and Bicyclists
• The public avoids using Roundabouts
• They are unsafe next to schools
1900’s - 1940’s Rotaries and Traffic Circles Used
1950’s Circular Intersections fell out of favor
1963 Great Britain redesigns the Circular
Intersection
1980’s “Modern Roundabout” used throughout
Europe and Australia
1990’s “Modern Roundabout” utilized in the U.S.
» More than 1000 now built in U.S.
» Over 300 more to be built this year alone
Circular Intersection History U.S. Modern Roundabout HistoryU.S. Modern Roundabout HistoryU.S. Modern Roundabout HistoryU.S. Modern Roundabout History
1990 First Modern Roundabout in Nevada
1992 Florida’s first Modern Roundabout
1993 Maryland’s first Modern Roundabout
1995 Vermont’s first Modern Roundabout
2000 New York’s first Modern Roundabout
2004 Pennsylvania’s first Modern Roundabout
2004 New Jersey’s first Modern Roundabout
2004 Delaware’s first Modern Roundabout
2004 Virginia’s first Modern Roundabout
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Leading Roundabout States
Colorado > 150
Washington > 95
Utah > 90
Oregon > 50
Florida > 40
Kansas > 35
California & Nevada > 20 each
North Carolina > 15
New York > 18
What Is a Roundabout?
• A circular intersection joining
two or more streets
• All turns are to the right
• The SAFEST at-grade intersection
Not a RoundaboutDifferences Between Roundabouts and Circles / Rotaries
• Yield at the approach
• Vehicle Deflection
• Splitter Island to control speeds
Is a Roundabout the Right Tool ?
• History of Accidents
• High proportionate of left turns
• Irregular Geometrics
• Vehicle Queues
• Less expensive means of control
• Sufficient Right-of-Way
Operational Comparison of
Roundabouts Vs. Signals
• Enhanced safety • Intersection efficiency – traffic
moves• Potential air quality benefits• Lower cost to build & operate• Fuel Savings• Improved aesthetics• U-turns are allowed
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Vehicle-Vehicle Crossing Conflicts
Signalized Intersection
Diverging 8
Merging 8
Crossing 16
Total 32
Roundabout Design
Diverging 4Merging 4Crossing 0Total 8
INSURANCE INSTITUTE FOR
HIGHWAY SAFETY
CRASH REDUCTIONS FOLLOWING INSTALLATION OF ROUNDABOUTS IN THE UNITED STATES – MARCH 2000
• Reduction of Total Crashes by 39%
• Reduction of Injury Crashes by 76%
• Reduction of Fatal and Incapacitating Crashes by 89%
On the web at: www.highwaysafety.org
Safety Benefits
Based on 15 Single Lane Roundabouts in Maryland in 2004
• Fatal Crashes down 100 percent
• Total crash rate down 60 percent
• Injury crash rate down 82 percent
• Property damage down 27 percent
Construction Time
DEPENDING ON THE TECHNIQUES USED, IT MAY TAKE FROM THREE WEEKS TO THREE MONTHS TO COMPLETE CONSTRUCTION OF A ROUNDABOUT
Special Considerations/Concerns
• Public Acceptance
• Driver Inexperience
• Pedestrians / ADA concerns
• Bicycles
• Emergency vehicles
• Lighting Concerns
• Right of Way requirements
Public Attitude Toward Roundabouts -
Before and After Construction
Attitude Before After
Construction Construction
Very Negative 23% 00%
Negative 45% 00%
Neutral 18% 27%
Positive 14% 41%
Very Positive 0% 32%
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Public Involvement
• Public resistance is common
• Before construction: 2 to 1 against roundabout
• Education is crucial
• After construction: 3 to 1 in favor of roundabout
• Visualizations & traffic simulations are very helpful
Community Acceptance
Main Vail - Diamond Interchange $2M (8,200 vph)
Community Acceptance
Vail, CO Constructed Oct. 1995
Voted Best Public Works Project
5 Years Straight
Public Opinion WILL Change
The director of the Charles R. Wood Theater said she was skeptical when the Greenwich roundabout was first talked about.
"I'm not an expert on traffic, but I was convinced it wasn't going to work out," she said.
Now, she describes driving through the circular intersection as an “awesome” experience.
"I guess sometimes you just have to trust the opinions of traffic experts," she said.
Pedestrian Consideration
Benefits:• Easy to determine gaps
• Cars only coming from one direction
• Fewer lanes to cross
• Splitter Island provides refuge
• Slower Speeds
Trade Offs:• Must assess gaps
• No protected phase ? ? ?
Unless “All Red” Signals Provide No
“Protected” Pedestrian Phase
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SUMMARY-Why Safer for Pedestrians?
Much lower number of conflict points. – Because all vehicles travel the same direction in a roundabout, the
number of vehicle/pedestrian conflict points is much lower than at intersections controlled by traffic signals.
Vehicles [are forced] to approach and travel through slowly.
– This maximizes the time that pedestrians and motorists have to avoid conflicts.
Non-attentive driving eliminated.– For example, vehicle/pedestrian crashes that occur when motorists run
red lights and ignore stop signs do not happen at roundabout intersections. The horizontal curvature of the roundabout forces drivers to pay attention to their surroundings as they approach and passthrough the intersections.
Pedestrian exposure to traffic is much lower.
2003 Legislative Action
House Joint Resolution 594…….
Resolved, That the Department of Transportation be encouraged to construct more roundabouts instead of signalized intersections;
“Roundabouts;
An Informational Guide”
FHWA Document Publication FHWA Document Publication
Number RDNumber RD--0000--067067
““SIDRASIDRA”” SoftwareSoftware
Used to determine Used to determine
feasibility, appropriate feasibility, appropriate
geometric configuration and geometric configuration and
functional capabilities in functional capabilities in
regards to volumes and level regards to volumes and level
of service.of service.
Roundabout Informational Pamphlet
Roundabouts in Virginia
Why Use a Roundabout?
How to Drive Roundabouts
Review and Approval Process
• District
Existing & Proposed Subdivisions
Secondary System – up to Design
Volume of 10,000 VPD
• Roundabout Review Committee
Secondary System – over
10,000 VPD
All Urban and Primary Systems
Items the Committee Reviews
• Approach Grades and sight distances
• All Geometrics
• Pedestrian crossing locations
• Pavement markings
• Signing
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Items the Committee Reviews
• Roadway Lighting (desirable)
• Nearest entrance locations and nature of property use
• Initial or present and projected design year traffic counts on all approaches
• Turning movements for all directions
When to Submit
• Early on, as soon as the preliminary plans are completed or a proposed site is selected.
• The Committee will assist the Districts in their review when asked.
Review Time
• Typical, allow two weeks for the Committee’s review.
ROAD DESIGN MANUAL
The information that we have mentioned today regarding the Roundabout Approval Process and the Data to be Submitted for Review will be included in the July 2006 Revision of the Road Design Manual.
Roundabouts in Virginia
Charlottesville Airport
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Gloucester Powhatan Courthouse
City of Richmond Christopher Newport
Va Tech Campus Town of Amherst
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Amherst Circle 1940 Plan Sheetamherst.jpg (882 KB)
amherst.jpg (882 KB) Gordonsville Circle
Roundabouts – Yes or No
Moving
Virginia
We Keep
Roundabout Review Committee
Terry Knouse, PE - Location & Design
Steve Edwards – Traffic Engineering
Walter Pribble – Transportation & Mobility Planning
QUESTIONS
? ?Roundabouts
The Virginia Experience