World Library  
Flag as Inappropriate
Email this Article

Traffic circle

Article Id: WHEBN0000184757
Reproduction Date:

Title: Traffic circle  
Author: World Heritage Encyclopedia
Language: English
Subject: Florida State Road 820, Tiorati Brook Road, Bethpage State Parkway, Intersection (road), Ontario Highway 420
Collection: Road Junction Types, Roundabouts and Traffic Circles
Publisher: World Heritage Encyclopedia

Traffic circle

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.
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.
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.

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 3-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, roundabouts 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]


  • Design 1
  • History 2
  • Examples of traffic circles 3
    • United States 3.1
      • Massachusetts 3.1.1
      • Other states 3.1.2
    • Elsewhere 3.2
  • See also 4
  • References 5


Design criteria include:

  • Right-of-way—whether entering or circling vehicles have the right of way. The New Jersey Driver's Manual recommends that, in the absence of flow control signs, traffic yields based on "historically established traffic flow patterns",[8] and there are no set rules.[9] In New England,[10] Washington, D.C. and New York State,[11] entering traffic yields, as is the norm in virtually all countries outside of the U.S.
  • Angle of entry— Angles range from glancing (tangential) that allow full-speed entry to 90 degree angles (perpendicular).[12]
  • Traffic speed—High entry speeds (over 30 mph / 50 km/h) require circulating vehicles to yield, often stopping, which lowers capacity and increases crash rates compared to modern roundabouts.[13]
  • Lane changes— Allowed or not
  • Diameter—The greater the traffic, the larger the circle.[12]
  • Island function—Parking, parks, fountains, etc.[12]


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:

  • It takes a large diameter circle to provide enough room for merging at speed. Although some of these circles were huge (many were in excess of 100 meters or 300 feet in diameter), they were not large enough for high-speed merging.
  • Giving priority to entering traffic means that more vehicles can enter the circulatory roadway than it can handle. The result is congestion within the circle which could not clear without police intervention.

The experience with traffic circles and rotaries in the US 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.

Examples of traffic circles

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

United States


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

Other states


See also


  1. ^ Victoria Transportation Policy Institute Online TDM Encyclopedia: Traffic Calming (modern roundabouts section)
  2. ^ para 1.5Roundabouts: an Informational GuideU.S. Department of Transportation:
  3. ^ Johnson, Jeffrey A. (6 August 2012). "Salem Four Corners traffic circle to start rounding into shape".  
  4. ^ U.S. Department of Transportation: Safety Aspects of Roundabouts presentation
  5. ^ [3]
  6. ^ [4]
  7. ^ Technical Summary: RoundaboutsU.S. Department of Transportation:
  8. ^
  9. ^
  10. ^ Commonwealth of Massachusetts, Registry of Motor Vehicles. "Sharing the Road: A User's Manual for Public Ways". Retrieved 2009-05-13. 
  11. ^ :
  12. ^ a b c Roundabout: an Informational Guide
  13. ^ 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. 
  14. ^ 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
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.