I offer this perspective without extraneous comment, save for the observation that there isn't very much meat on the bone.
The Other Side of Roundabouts: More Crashes, by John Metcalfe (CityLab)
Traffic circles are great at preventing fatal wrecks. But what can be done about the crashes they do provoke?
Roundabouts are easy to love. They’re elegant in design, reduce traffic deaths compared to traditional intersections, and can support some gnarly public art.
But Americans hate them anyway, and one reason may be becoming clearer: While roundabouts are great at preventing serious crashes, they may bring on more non-fatal wrecks, to believe the latest in traffic-circle research coming from the fecund roundabout reserve of Wisconsin.
Past monitoring of 30 of the state’s 300-plus roundabouts revealed these particular intersections, which used to be traffic-signal controlled, experienced a 38 percent drop in car deaths and injuries. At the same time the total number of crashes jumped 12 percent. These additional accidents caused mainly property damage, and are thought to be a result of confused or unprepared drivers trying to navigate the unfamiliar roadway design.