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A roundabout is a type of circular junction in which road traffic must travel in one direction around a central island. Signs usually direct traffic entering the circle to slow down and give the right of way to drivers already in the circle.[1]

These junctions are sometimes called modern roundabouts in order to emphasise the distinction from older circular junction types which had different design characteristics and rules of operation. Older designs, called traffic circles or rotaries, are typically larger, operate at higher speeds, and often give priority to entering traffic.[1] In some cases, the term "traffic circle" has been used to describe roundabouts in North America,[2] but generally "roundabout" is used by engineers.[3]

In countries where people drive on the right, the traffic flow around the central island of a roundabout is anticlockwise (counterclockwise). In countries where people drive on the left, the traffic flow is clockwise.

Statistically, roundabouts are safer for drivers and pedestrians than both traffic circles and traditional intersections.[4] Because low speeds are required for traffic entering roundabouts they are not designed for high-speed motorways (expressways). When such roads are redesigned to take advantage of roundabout principles, steps are taken to reduce the speed of traffic, such as curving the approaches.

Modern roundabouts are particularly common in Australia, People's Republic of China, Malaysia, Iceland, Denmark, France, Hungary, Ireland, Morocco, New Zealand, Qatar, Spain, the United Arab Emirates and the United Kingdom. Half of the world's roundabouts are in France (over 30,000 as of 2008).[5] The first modern roundabout in the United States was constructed in Summerlin, Nevada in 1990,[6] and roundabouts have since become increasingly common in North America.


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