Roundabouts are the devil's own invention. Such might work in Paris or London or Rome this very day... BUT, I suggest to you that they do so IN SPITE of their inherent nature of evil. I submit to you the hypothosis thusly... The roundabouts in Paris and London and Rome "appear" to work well because they have been in existance for a long time AND, everyone knows the the guy on the right has the right of way ...... BUT, we are talking about North America where the bigger vehicle has the right of way. Here in the land of "My truck's bigger'n yers.", that can be a problem.
I am serious. I'm not only a transportation engieer, I am a redneck with an old, scratched up, pickup truck. NNWW!!