Roundabouts require traffic to circulate counterclockwise around a center island. Unlike Traffic Circles, roundabouts are used on higher volume streets to allocate right-of-way between competing movements.

Good for:

• Locations with a history of accidents;
• Intersections where queues need to be minimized
• Intersections with irregular approach geometry
• Providing inexpensive-to-operate traffic control as an alternative to a traffic signal
• Handling a high proportion of U-turns
• Locations with abundant right-of-way

Advantages:

• Roundabouts can moderate traffic speeds on an arterial
• They are generally aesthetically pleasing if well landscaped
• They enhanced safety compared to traffic signals
• They can minimize queuing at the approaches to the intersection
• They are less expensive to operate than traffic signals

Disadvantages:

• They may be difficult for large vehicles (such as fire trucks) to circumnavigate
• They must be designed so that the circulating lane does not encroach on the crosswalks
• They may require the elimination of some on-street parking
• Landscaping must be maintained, either by the residents or by the municipality

Effectiveness:

• Average 29% reduction in accidents, with a reduction from 9.3 to 5.9 accidents per year (from a sample of 11 sites; source: Roundabouts: An Informational Guide).

Similar Measures:

• By constructing a small island in a neighborhood intersection and leaving the existing curbs, you have a Traffic Circle

Cost Estimate(s):

• Varies by materials used and the amount of area covered