DSC_0335-02smlA “controlled roundabout” — also known as a “metered roundabout” and sometimes nicknamed a “SuperCircle” in North Carolina — strives to combine the best features of a traditional signalized intersection and a roundabout. A controlled roundabout enables the flows and operation of a roundabout to remain in control during peak periods, through the provision of a part-time traffic signal on one or more approaches to the circle enabling traffic to move more efficiently and reduce delay.

When the signal is activated and displaying red, this creates additional space in the circulating flow in the roundabout downstream of the signal-controlled entrance, and enables downstream travelers to enter the roundabout more readily.

Whenever the traffic volumes entering a roundabout are below the threshold where signal assistance is required to maintain flow for all approaches, the entry signals can remain dark or blank.  This will typically be the vast majority of the day.

Current RTA focus

Encourage the consideration and installation of roundabouts — either uncontrolled or controlled — at approprate locations across the region.

Highlight the benefits of controlled roundabouts to increase the number of possible locations where roundabouts can be considered and/or retained.

Recent successes of RTA and partners

RTA developed, funded, and coordinated a study of controlled roundabouts (i.e., “metered roundabouts” or “supercircles”) during 2012 and 2013.

The results of RTA-funded and coordinated research on controlled roundabouts were presented at the RTA Solutions Forum at Research Triangle Park, NC in August 2013 and at the Transportation Research Board in Washington, DC in January 2014.

RTA-funded and coordinated research on controlled roundabouts will be published in Transportation Research Record:  The Journal of the Transportation Research Board in 2014.

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