| Roundabouts |
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Background
ODOT, local jurisdictions and consultants are looking for alternative intersection control methods and roundabouts have been proposed as a solution. The Department has recognized a need for additional knowledge in the design and operation of roundabouts. To better evaluate the potential of this form of intersection control, ODOT began a research effort in July, 1997. A synthesis of the most current information relating to roundabouts was made. The report was completed and published in June, 1998. Additional information gathering included observation and data collection on existing roundabouts in Colorado.
Research
The Oregon Department of Transportation Research Unit has published the report
‘Modern Roundabouts for Oregon’ (#98-SRS-522). The Preliminary Design Unit led the research effort, overseen by a multi-disciplinary group. This report reviews current research and practice on modern roundabouts, both in the US and other countries. The report compares the advantages and disadvantages of roundabouts, summarizes safety implications, and discusses pedestrian and bicyclist considerations. Guidelines from other states on the geometric design of roundabouts is reviewed, as are studies and formulas used to evaluate roundabout performance, measuring capacity and delay. Software models for roundabouts are reviewed. The report makes recommendations for considering and using roundabouts in Oregon, as well as identifying further research needs in this area.
Roundabouts in Brief
The roundabout concept was first invented in the early 1900’s and deployed throughout Europe and America. During the 1950’s there was a loss of confidence in roundabouts, due mainly to the problem of traffic locking and the increasing number of accidents. Many were replaced by traffic signals.
In 1966, the offside priority rule (an entering vehicle gives way to vehicles in the roundabout) and the yield at entry operation enhanced roundabout capacity and safety performance. The success of the modern roundabout provoked renewed interest in roundabouts worldwide.
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| Roundabout Images |
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Pictures
Use the following link to view a Photo Gallery of before and after pictures of the roundabound at Bend, Oregon.
 Oregon Roundabout
Video Clips
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Video Clip #1 - This video clip covers the operation of an interchange ramp terminal in Avon, Colorado. The intersection is a two-lane roundabout. The operation was viewed mid-day, during off peak hours.
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Video Clip #2 - This video clip covers the operation of a two lane roundabout at the intersection of an arterial street with a suburban state highway in Avon, Colorado. The operation was viewed mid-day, during off peak hours.
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Instructional Video on how to use a roundabout
We have produced a video on how to use a single lane roundabout. The video covers instructions for drivers (including trucks), bicyclists and pedestrians. To order a copy, send a check or money order for $11.00 to:
Photo & Video Services, Support Service Branch
355 Capitol Street NE #14-A
Salem OR 97301-3871
(503) 986-3702
- ask for the video 'A User's Guide to Roundabouts'.
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| Resources |
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Here are a few related sites and resources that may be of interest:
General Information and Driving Instructions (pdf)
Modern Roundabouts - Research Report (pdf)
New York's Roundabout Site
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