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Federal Highway Administration

The modern roundabout is an intersection with a circular configuration that safely and efficiently moves traffic. Roundabouts feature channelized, curved approaches that reduce vehicle speed, entry yield control that gives right-of-way to circulating traffic, and counterclockwise flow around a central island that minimizes conflict points. The net result of lower speeds and reduced conflicts at roundabouts is an environment where crashes that cause injury or fatality are substantially reduced.

"A multilane roundabout with four approach legs. Each approach leg is a four-lane divided highway. Each approach leg yields to circulating traffic within the roundabout and features a high visibility crosswalk. Several pedestrian safety countermeasures are visible, including tactile curb ramps and multiuse path facilities."

Illustration of a multi-lane roundabout. Source: FHWA

Roundabouts are not only a safer type of intersection; they are also efficient in terms of keeping people moving. Even while calming traffic, they can reduce delay and queuing when compared to other intersection alternatives. Furthermore, the lower vehicular speeds and reduced conflict environment can create a more suitable environment for walking and bicycling.

"A single-lane roundabout where each of the four legs approaching the roundabout is a yield-controlled, two-lane roadway. Each approach leg features a high visibility crosswalk. Raised medians are present in the vicinity of the roundabout but not beyond the extents of the roundabout. The roundabout island appears to be traversable by trucks and other large vehicles.

Example of a single-lane roundabout. Source: FHWA

Roundabouts can be implemented in both urban and rural areas under a wide range of traffic conditions. They can replace signals, two-way stop controls, and all-way stop controls. Roundabouts are an effective option for managing speed and transitioning traffic from high-speed to low-speed environments, such as freeway interchange ramp terminals, and rural intersections along high-speed roads.


1. (CMF ID: 211, 226) AASHTO. The Highway Safety Manual, American Association of State Highway Transportation Professionals, Washington, D.C., (2010).