Traffic circle

A traffic circle or rotary is a type of intersection that has a generally circular central island. Entering traffic must typically alter direction and speed to avoid the island, creating a circular flow in one direction. In most applications, traffic circles replace the stop lights and traffic signs that regulate flow in other intersections.

In English-speaking countries other than the United States, traffic circles are called roundabouts. U.S. traffic engineers use "roundabout" for intersections in which entering traffic must yield to traffic already in the circle, reserving "traffic circle" for those in which entering traffic is controlled by stop signs, traffic signals, or is not formally controlled.[1]

Contents

Design

Design criteria include:

History

French architect Eugène Hénard was designing one-way circular intersections as early as 1877.[8] 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 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

United States

Massachusetts

Other States

Elsewhere

Sources

  1. ^ U.S. Department of Transportation: Roundabouts: an Informational Guide para 1.5
  2. ^ http://www.state.nj.us/mvc/manuals/chap_04_06.html
  3. ^ http://www.state.nj.us/mvc/pdf/Licenses/Driver%20Manual/Chapter_4.pdf
  4. ^ Commonwealth of Massachusetts, Registry of Motor Vehicles. "Sharing the Road: A User's Manual for Public Ways". http://www.mass.gov/rmv/dmanual/index.htm. Retrieved 2009-05-13. 
  5. ^ :http://www.safeny.com/rowa-vt.htm#1145
  6. ^ a b c Modern Roundabouts, an Informational Guide
  7. ^ Shashi S. Nambisan, Venu Parimi (March 2007). "A Comparative Evaluation of the Safety Performance of Roundabouts and Traditional Intersection Controls". Institute of Transportation Engineers. http://findarticles.com/p/articles/mi_qa3734/is_200703/ai_n18755716/pg_1. Retrieved 2007-11-27. 
  8. ^ 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 http://www.hamilton-baillie.co.uk/papers/ICE_paper_April05.pdf

See also