Roundabouts
The modern roundabout is a type of circular intersection defined by the basic operational principle of entering traffic yielding to vehicles on the circulatory roadway and certain key design principles to achieve deflection of entering traffic by channelization at the entrance and deflection around a center island. Modern roundabouts have geometric features providing a reduced speed environment that offers substantial safety advantages and excellent operational performance.
Roundabouts are the preferred safety and operational alternative for a wide range of intersections. Roundabouts shall be considered as an alternative for all intersections that are being reconstructed, including those where a traffic signal is being proposed. This is especially true for intersections that have been identified as needing major safety or operational improvements.
Roundabouts may not operate well if there is too much traffic entering the intersection or if the percentage of traffic on the major road is too high. Candidate intersections shall be analyzed to determine whether a roundabout will perform acceptably.
Roundabout Video From FHWA