[ndr42]

One-lane-roundabouts are very safe. I lived in Hannover (Germany) in the 80s and 90s, they had 2 or 3 lanes in the roundabouts. There were large signs that counted the accidents (200+/year) to raise awareness and during the trade fairs (anybody remembers Cebit?) the number of accidents peaked. Today they are all a lot safer because of a lot of traffic lights.