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Traffic Circle

 
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Traffic circle
 
 
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A traffic circle is an intersection with a circular shape and, usually, a central island.






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Columbuscirclefromtimewarnercenternyc20050807
Desotofountain
Route 34 Circle
A traffic circle is an intersection with a circular shape and, usually, a central island. Traffic is allowed to go in one direction only around a central island. Traditionally, traffic entering a circle has the right-of-way
Traffic

Traffic on roads may consist of pedestrians, ridden or herded animals, vehicles, streetcars and other conveyances, either singly or together, while using the public way for purposes of travel....
, although some circles give right-of-way to the primary roads. In roundabout
Roundabout

A roundabout is a type of road junction at which traffic enters a one-way stream around a central island. In the United States it is commonly known as a "rotary" or a "traffic circle", but sometimes is technically called a modern roundabout, in order to emphasize the distinction from the older, very much larger type of traffic circl...
s and often rotaries
Rotary (intersection)

A Rotary is a variation of a traffic circle or a roundabout.Most common in the Northeastern United States and often called a traffic circle outside New England, a rotary is primarily a mid-twentieth-century roadway design defined as a circular, one-way, often multi-lane roadway, similar to a traffic circle or a roundabout, but with key diff...
, as opposed to traffic circles, entering traffic must yield to traffic already in the circulatory roadway.

History

French architect Eugène Hénard was designing one-way circular intersections as early as 1877. American architect William Phelps Eno
William Phelps Eno

William Phelps Eno was an United States businessman responsible for many of the earliest innovations in road safety and traffic control. He is sometimes known as the "Father of traffic safety", despite never having learned to drive a car himself....
 favored small traffic circles. He designed New York City's famous Columbus Circle
Columbus Circle

Columbus Circle, named for Christopher Columbus, is a major landmark and point of attraction in the New York City borough of Manhattan. Completed in 1905 and renovated a century later, it is located at the intersection of Broadway , Central Park West, Central Park South , and Eighth Avenue, at the southwest corner of Central Park, with coord...
, which was built in 1905. Other traffic circles were subsequently built in the United States. Many were large diameter 'rotaries' that enabled high speed merge and weave, and gave priority to the traffic entering the circle. 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 weren't 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.


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 had ceased entirely. The experience with traffic circles in other countries was not much better until the development of the modern roundabout
Roundabout

A roundabout is a type of road junction at which traffic enters a one-way stream around a central island. In the United States it is commonly known as a "rotary" or a "traffic circle", but sometimes is technically called a modern roundabout, in order to emphasize the distinction from the older, very much larger type of traffic circl...
 in the United Kingdom during the 1960s.

Among the most famous traffic circles in the world is that of Canberra
Canberra

Canberra is the List of Australian capital cities of Australia. With a population of over 340,000, it is Australia's largest inland city and the eighth largest Australian city overall....
, Australia
Australia

Australia, officially the Commonwealth of Australia, is a country in the southern hemisphere comprising the Australia of the world's smallest continent, the major island of Tasmania, and numerous list of islands of Australia in the Indian Ocean and Pacific Oceans....
, where a large traffic circle encircles Parliament House
Parliament House, Canberra

File:Parliament House, Canberra.jpgParliament House is the meeting place of the Parliament of Australia. It is located in Canberra, the capital of Australia....
. This circle has traffic lights at each major intersection within the circle.

The largest traffic circle in the world is claimed to be one of those in the Dammam
Dammam

Dammam is the Capital of the Eastern Province, Saudi Arabia in Saudi Arabia. Dammam is the largest city in the Eastern Province; Dammam Port is one of the largest on the Persian Gulf....
 coastal road, Al-Khalij Street, in Saudi Arabia
Saudi Arabia

The Kingdom of Saudi Arabia, KSA , is an Arab country and the largest country of the Arabian Peninsula. It is bordered by Jordan on the northwest, Iraq on the north and northeast, Kuwait, Qatar, Bahrain, and the United Arab Emirates on the east, Oman on the southeast, and Yemen on the south....
 with a length of approximately 1.9 km (1.20 miles)

Composition

Traffic circles are often composed of concrete or asphalt although more recently rubber curbing is being used to create traffic circles as well, primarily in residential areas. Rubber curbing consists of units of flexible rubber that are bent and installed around a landscaped area to create traffic circles.

Pop Culture

Traffic circles are currently featured in the 2009 Mathematical Contest in Modeling
Mathematical Contest in Modeling

The Mathematical Contest in Modeling is a multi-day mathematics competition held annually, during the first or second weekend in February, since 1985 by COMAP and sponsored by SIAM, the NSA, and INFORMS....
. The problem is to determine an optimal design for a traffic circle in terms of traffic flow. This includes technical reports to engineers interested in implementing the models.

Source


See also

  • List of traffic circles in New Jersey
    List of traffic circles in New Jersey

    This is a list of traffic circles in New Jersey. The U.S. state of New Jersey at one point had a total of 101 traffic circles, 44 of which were part of State highway....
  • List of Circles in Washington, D.C.
    List of Circles in Washington, D.C.

    The Streets and highways of Washington, D.C. in Washington, D.C. consists primarily of numbered streets along the north-south axis and lettered streets followed by streets named in alphabetical order along the east-west axis....
  • Roundabout
    Roundabout

    A roundabout is a type of road junction at which traffic enters a one-way stream around a central island. In the United States it is commonly known as a "rotary" or a "traffic circle", but sometimes is technically called a modern roundabout, in order to emphasize the distinction from the older, very much larger type of traffic circl...