<P> Because of the requirement for low speeds, roundabouts usually are not used on controlled - access highways, but may be used on lower grades of highway such as limited - access roads . When such roads are redesigned to take advantage of roundabouts, traffic speeds must be reduced via tricks such as curving the approaches . </P> <P> The word roundabout dates from early 20th century United Kingdom . </P> <P> In U.S. dictionaries the terms roundabout, traffic circle, road circle and rotary are synonyms . </P> <P> The U.S. Department of Transportation adopted the term modern roundabout to distinguish those that require entering drivers to give way to others . This article follows that convention and refers to other types as traffic circles or rotaries . Many old traffic circles remain in the northeastern US . Some modern roundabouts are elongated to encompass additional streets, but traffic always flows in a loop . </P>

Who has the right of way in a round a bout