Frequently Asked Questions (FAQ)

What is a modern roundabout?

Since modern roundabout technology only dates back some 40 years worldwide and about 15 years in this country, the term "modern roundabout" was used to distinguish design characteristics from other types of traffic circles that have existing for over 100 years in this country. With the increasing acceptance and encouragement of their use on all governmental levels in the U.S., modern roundabouts are now more commonly referred to simply as "roundabouts". Roundabouts are circular intersections with specific design and traffic control features. These features include yield control of entering traffic, channelized approaches utilizing splitter islands to separate entering and exiting traffic, and appropriate curvature to ensure that travel speeds on the circulatory roadway are low. Priority is given to circulating traffic rather than entering traffic. Roundabouts are designed to create a free-flowing, low speed environment at intersections. When used for the proper traffic volume range, roundabouts will increase intersection efficiency, thereby eliminating the need for storage lanes (approach lanes including left and right turn pockets at signalized intersections) such that right of way requirements can be minimized. Safety is enhanced by the elimination of the majority of conflict points. For example, the possibility of high speed and head on collisions is virtually eliminated. Both worldwide and U.S. statistics indicate a 90% reduction in deaths when compared to stop or signal controlled intersections. Major reductions in injury accidents are also documented. Los Angeles County is in the process of finalizing a document called "Roundabout Policy and Design Practices for the County of Los Angeles". A draft of this document can be made available by contacting Linda Ayers at (626)458-4927. The Federal Highway Administration publication "Roundabout: An Informational Guide" is available on the internet at