Study Details

Study Title: Turbo Roundabouts: Design Principles and Safety Performance

Authors: Fortuijn

Publication Date: JAN, 2009

Abstract: While concentric two-lane roundabouts have a higher capacity than single-lane roundabouts, they have the disadvantage of a higher driving speed through the roundabout. They also reintroduce the possibility of lane changing on the roundabout, hence raising the risk of accidents. The author developed the "turbo roundabout" in 1996 in an attempt to deal with these drawbacks. This type of roundabout has the following features: - no lane changing on the roundabout; - no need to yield to traffic on more than two lanes; - low driving speed through the roundabout by the presence of raised lane dividers. The paper deals with the concept of the turbo roundabout and the details determining success. Studies have shown that the risk of accidents associated with injury is greatly reduced on turbo roundabouts: an 80% reduction has been measured. In view of the known safety trends on single-lane roundabouts, it is ecommended that a slightly lower reduction in the accident rate (70%) should be assumed in the long term. Another great advantage of the turbo roundabout is the fact that the traffic flow can be divided over the lanes of the roundabout in a much more balanced way. Since 2000, 70 turbo roundabouts have been built in the Netherlands. The Dutch Information and Technology Platform CROW published its guidelines on Turbo roundabouts in April 2008 (CROW, 2008).

Study Citation: Fortuijn, L. "Turbo Roundabouts: Design Principles and Safety Performance." TRB 88th Annual Meeting Compendium of Papers CD-ROM. Washington, D.C., 2009.


CMFs Associated With This Study

Category: Intersection geometry

Countermeasure: Install single lane roundabout

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.213 78.7 2 Stars All All Not Specified
0.319 68.1 2 Stars All All Not Specified

Countermeasure: Install turbo roundabout

CMF CRF(%) Quality Crash Type Crash Severity Roadway Type Area Type
0.239 76.1 2 Stars All All Not Specified