Yikes, read through this article on intersections and see if you can make sense of everything- http://www.slate.com/id/2300425/pagenum/2 (someone reading this provided a link to a youtube video that does a much better job of presenting the solution this article provides)
In a nutshell, many believe that left turns are the big no-no for proper traffic flow. But why go to so much trouble, all manner of examples of complex traffic re-engineering to solve this problem, and *no* mention of traffic circles? I have both cycled and driven in areas that make extensive use of traffic circles, and they require very little retraining. They’re not entirely intuitive; it takes a little getting used to the idea that, at least in some cultures, making eye-contact means you’re yielding to the other person, but that’s likely more cultural than an aspect of the traffic circle itself.
Yes, they require real estate, but the center of the circle presents significant opportunity for visual enhancement (park accessible via underground or overground passageway, gateway signage, etc). They also offer opportunities for traffic calming without the complication of signals and other electro-mechanical devices that don’t work when there’s a power outage. In other words, very low maintenance.
Perhaps part of the issue is that, in the US, there’s a belief that a blank space must be filled. It should have parking, or office space, or something. You can’t just have a piece of land (the center of the circle) that people can’t park or walk or trash. Darn, once again, life imitates life. It’s just like a retail bike shop. You get too large an open space and you want to put something there, instead of recognizing the value of reducing clutter and making things more open and spacious to set people at ease.