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Roundabout intersection

A roundabout, rotary or gyratory circus is a type of road junction at which traffic streams circularly around a central island after first yielding to the circulating traffic. Roundabouts are used for traffic calming and are updated forms of the much simpler traffic circles of Europe.

British engineers reengineered the traffic circle in the mid-1960s to overcome its limitations of capacity and for safety issues. Unlike traffic circles, roundabouts operate with yield control to give priority to circulating traffic and eliminate much of the driver confusion associated with traffic circles and driver wait associated with signalized intersections[?]. Roughly the same size as signalized intersections with the same capacity, roundabouts also are significantly smaller in diameter than traffic circles, separate incoming and outgoing traffic with pedestrian islands and therefore encourage slower and safer speeds (see traffic calming).

Roundabouts are safer than both traffic circles and traditional intersections -- having 40% fewer vehicle collisions, 80% fewer injuries and 90% fewer serious injuries and deaths (compared with a sampling of roundabouts in the United States with the intersections they replaced). Roundabouts also significantly reduce potential points of conflict between pedestrians and motorized traffic and are therefore considered to be safer for them. Roundabouts, especially large fast moving ones, are however unpopular with, and can be dangerous for cyclists.

In addition to improved vehicle and pedestrian safety, and in spite of lower speeds, roundabouts dramatically outperform traffic circles in terms of vehicle throughput and, because circular traffic is always moving, in roundabouts, they outperform signalized traffic signals as well.

However, due to the fact that vehicle traffic must yield instead of stop, there are some safety concerns for bicyclists who ride on pedestrian walkways and especially for persons with visual impairments. Safety concerns for the second group of people is especially important in countries that have legislation protecting the rights of people with disabilities.

A town in Wiltshire, England famous for its roundabouts is Swindon. It has a 'Magic Roundabout' which is made up of one large center roundabout and five smaller (mini) roundabouts around the center.


A diagram showing the movements of a roundabout in a country where traffic drives on the left.

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