The Oregon Department of Transportation, local jurisdictions and consultants continue to look for traffic control methods that provide ways to safety manage the flow of traffic, bicycles and pedestrians through intersections large and small. Roundabouts are one such method.
ODOT's Research Unit has published the report "Modern Roundabouts for Oregon" (#98-SRS-522).
- 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 are 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.