The Maryland State Highway Administration (SHA) began implementing modern roundabouts (RAB), circular at-grade intersections, in 1993. They are an effective intersection design which reduces the numbers of intersection conflict points while operating at slower speeds. This type of intersection has successfully replaced many traditional intersections that had exhibited recurring crash problems and/or operational problems. Roundabouts operate continuously, but at much slower speeds than traditional intersections and normally result in very little delay. Normal operating speeds within roundabouts are between 20 and 30 mph.