We have two in my town, we need more! They're so, so much more efficient for traffic, especially with odd-ball 5-way intersections and no one can ever make up their mind whose turn is next. Problem is, people aren't used to them and consider them like stop-sign or red-light intersections. They wait until the entire circle is clear before they enter! Bastards! Just aim for the back wheel of the car in the circle when you arrive and hop on in! Sometimes, I do laps around it in my car or bike to bug those people who are waiting for the entire thing to clear...
One of my friends in England says her town has 4 stoplights and
176 roundabouts! 