Roundabout

A roundabout is a type of circular intersection or junction in which road traffic is slowed and flows almost continuously in one direction around a central island to several exits onto the various intersecting roads. In a modern roundabout, entering traffic must always yield to traffic already in the circle, and roundabouts have additional restrictions on the junction layout to give high safety. Elimination of the opportunity for the most deadly crashes at intersections (T-bone or perpendicular crashes), is the greatest asset of the intersection design. Pedestrians are routed away from the intersection into which automobiles enter to separate crosswalks located at least one full car length outside of the intersection, where they have a refuge between lanes of traffic. This enables pedestrians to only have to cope with traffic coming from one direction at a time, which is travelling slowly enough for visual engagement with drivers and encourages deference toward the pedestrians. Roundabouts, in their modern form, were standardised in the U.K., improving on the experience of traffic circles built in the U.S. following WWII, Modern roundabouts are now common in many countries around the world.

The word roundabout dates from the early twentieth century, In the U.S., the term traffic circle is used where entering traffic is either controlled by stop signs, traffic signals, or is not formally controlled at all and speed of vehicles may remain unchanged. The term, roundabout, is reserved for circular flow intersections where entering traffic must yield to traffic already in device, with the intention to calm the traffic and enable the highest flow possible through the intersection along with the highest safety for pedestrians and cyclists. Not all modern roundabouts are strictly circular, some being elongated to include several former intersections, but the traffic always follows a circular flow.