Red Mage
Boney
All it takes is one idiot in the circle, what you call roundabouts, and it screws up the whole mess. Unfortunately, more often than not you will find one of those idiots.
They recently put several circles up near my house. I hate them.
There was one of those traffic circles near my college. It was awful and caused so many traffic issues. Fortunately, they converted it to a normal 4 way intersection during my junior year and just like that all the traffic problems went away.