Misunderstanding of roundabouts is widespread in the U.S.-- not suprising since the only experience Americans have historically had with traffic circles has not been with roundabouts but, instead, with either scary large diameter rotaries (with high speed merging and weaving) or highly inefficient traffic circles (controlled by stops sign, yield signs or signals).

But the fact that Americans don't understand roundabouts does not mean that roundabouts aren't a good idea.

The modern roundabout is an animal most Americans have not seen until very recently, and they simply don't understand the concepts-- specifically, yield at entry and slow down even if you don't need to stop.

Some of the new roundabouts I've seen seem to lack a key feature of a well-designed roundabout, namely, deflection at entry (intended to force motorists to slow down). A motorist can pretty much blow through some roundabouts without slowing, and that is simply wrong.

From what I've read, a well-designed roundabout is often more efficient than either a stop-controlled or signal controlled intersection. And roundabouts seem to reduce accidents for motorists. But roundabouts don't seem to reduce the number of accidents involving bicycles (and may present some serious problems for pedestrians). How accident severity is affected I don't know.

Another problem is that a roundabout is likely to take up more space than an intersection-- and space costs money.