Re:Really bad idea. (Score 5, Informative)

Although it seems like traffic circles should be more dangerous, I'm not sure the data backs this up. This article, for example, cites several studies that show a significant decrease in accidents and an even more significant decrease in "severe injury" crashes when roundabouts replace traffic lights. The latter, at least, makes sense since roundabouts virtually remove the possibility of head on crashes.

However, as other posters have pointed out, there are several kinds of intersection, each with their own factors that must be accounted for, (traffic volume, etc.) and it is unclear if the studies have taken into account the differing characteristics of the intersections that were replaced.

Additionally, the IIHS, for one, considers roundabouts distinct from rotaries. Since many others do not make this distinction, it is difficult to tell what kind of traffic circles were studied, and what kind of traffic circles are being installed in the US's "roundabout revolution."

Either way, the knee-jerk reaction of "rotaries are dangerous" at the least needs a conditional and at best is quite false.