Are you sure?Roundabouts, in general, are great. They improve efficiency of movement and therefore fuel efficiency. They also cut down on the number of severe accidents. The number of minor accidents goes up, however.
Just a cursory search finds a report of 37% reduction in total collisions.
Sorry for the poor quality...
[video=youtube;puK5CwThaq4]http://www.youtube.com/watch?v=puK5CwThaq4[/video]