What is a Roundabout?

A roundabout is a type of circular intersection in which traffic can flow almost continuously in one direction around a central island. If multiple vehicles are suing the roundabout, then incoming vehicles yield to vehicles already in the roundabout.


  • Reduction of traffic conflicts (for example, left turns) that are frequent causes of crashes at traditional intersections
  • Facilitation of traffic flow - allowing more cars to pass at any given time than a traditional intersection
  • Reduction of fuel consumption, as most vehicles are not required to stop

For these reasons, roundabouts are gradually being adopted into communities across the US, including Sonoma County.

Video: Aerial footage of Arnold Drive at Agua Caliente Road Roundabout

Video: Modern Roundabouts (Federal Highways Administration)

Read More: Federal Highway Administration > Roundabouts

Arnold Drive at Agua Caliente Road

The Sonoma County Department of Transportation & Public Works constructed its first roundabout at the intersection of Arnold Drive and Agua Caliente Road in 2013.

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Contact Information

Business Hours
Monday – Friday
8:00 AM – 5:00 PM
Contact us by Phone
Office Location
La Plaza B
2300 County Center Drive
Suite B 100
Santa Rosa, CA 95403
38.462023, -122.725381


Manual for Uniform Traffic Control Devices


Find out about standard design and placement requirements for traffic control infrastructure.