Traffic circle

"Rotary (intersection)" redirects here. For other uses of Rotary, see Rotary (disambiguation).
Not to be confused with Roundabout.
Columbus Circle in New York City. Unlike a modern roundabout, the circle is quite large and pedestrians have access to the center island. Access is controlled by traffic lights.

A rotary, sometimes nicknamed a traffic circle, is a type of intersection that directs both turning and through traffic onto a one-way circular roadway, usually built for the purposes of traffic calming or aesthetics.[1] Contrary to a roundabout, where entering traffic always yields to traffic already in the circle and merges in directly, the entrances to traffic circles are three-way intersections either controlled by stop signs, traffic signals, or not formally controlled.[2] Colloquially, however, roundabouts are sometimes referred to as circles.[3]

In the United States, traffic engineers typically use the term rotary for large scale circular junctions between expressways or controlled-access highways. Rotaries typically feature high speeds inside the circle and on the approaches.[4]

In New England, traffic circles are generally called rotaries and the traffic that is already driving in the rotary always has the right of way. For examples of where this is specified, in Massachusetts "Any operator of a vehicle entering a rotary intersection shall yield the right-of-way to any vehicle already in the intersection.".[5] In Rhode Island entering vehicles "Yield to vehicles in the roundabout." [6]

Distinct from roundabouts, traffic circles and rotaries may also have an interior lane that requires traffic on it to change lanes in order to exit the circle.[7]

DeSoto Fountain sits in the center of a traffic circle in the City of Coral Gables, Florida. The arterial, DeSoto Boulevard, has unrestricted right of way, while the intersecting streets are controlled by stop signs.


Design criteria include:

Traffic 10-abreast traverses the Place de l'Étoile. This traffic circle surrounds the Arc de Triomphe at the intersection of ten two-way and two one-way streets. It has no lane markings.


French architect Eugène Hénard was designing one-way circular intersections as early as 1877.[14] American architect William Phelps Eno favored small traffic circles. He designed New York City's famous Columbus Circle, which was built in 1905. Other circular intersections were subsequently built in the United States, though many were large diameter 'rotaries' that enabled high speed merge and weave maneuvers. These designs were doomed to failure for two primary reasons:

The experience with traffic circles and rotaries in the USA was almost entirely negative, characterized by high accident rates and congestion problems. By the mid 1950s, construction of traffic circles and rotaries had ceased entirely. The experience with traffic circles in other countries was not much better until the development of the modern roundabout in the United Kingdom during the 1960s.

Starting in the 1990s the USA saw a revival of mostly smaller traffic circles, termed "roundabouts".[15] The modern roundabout finally arrived in the United States in 1990 in Summerlin, a major Las Vegas residential subdivision.[16] As of December, 2015 there are about 4800 of these modern roundabouts in the United States. As an example, Washington State contains about 120 roundabouts as of October 2016, all having been built since 1997 with more planned.[17]

Examples of traffic circles

The Western Rotary in Zagreb, Croatia with tram lines passing underneath.

United States

Rotaries in parts of New England

Traffic circles are referred to as "rotaries" in Massachusetts as well as parts of Connecticut, New Hampshire & Vermont.

Traffic circles in other parts of the US


See also


  1. "Online TDM Encyclopedia - Traffic Calming".
  2. U.S. Department of Transportation: Roundabouts: an Informational Guide para 1.5
  3. Johnson, Jeffrey A. (6 August 2012). "Salem Four Corners traffic circle to start rounding into shape". The Day.
  4. U.S. Department of Transportation: Safety Aspects of Roundabouts presentation
  5. U.S. Department of Transportation: Technical Summary: Roundabouts
  8. Commonwealth of Massachusetts, Registry of Motor Vehicles. "Sharing the Road: A User's Manual for Public Ways". Retrieved 2009-05-13.
  10. 1 2 3 "Index - Roundabout: An Informational Guide, June 2000 - FHWA-RD-00-067".
  11. Shashi S. Nambisan, Venu Parimi (March 2007). "A Comparative Evaluation of the Safety Performance of Roundabouts and Traditional Intersection Controls". Institute of Transportation Engineers. Retrieved 2007-11-27.
  12. P. M. Wolf, Eugene Henard and the Beginning of Urbanism in Paris, 1900–1914, International Federation for Housing and Planning, The Hague, 1969, cited by Ben Hamilton-Baillie & Phil Jones, Improving traffic behaviour and safety through urban design, Proceedings of ICE – Civil Engineering, volume 158 Issue 5 May 2005 p. 41
  13. History of the Modern Roundabout, RoundaboutsUSA
  14. History of the Modern Roundabout, RoundaboutsUSA
  15. Washintong's Roundabouts, WS-DOT website
  16. William Kenny, New intersection could uproot Boulevard for two years, Northeast Times
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