One of their main attractions, says Mayor Brainard, is safety. The Insurance Institute for Highway Safety, an independent research group, estimates that converting intersections with traffic lights to roundabouts reduces all crashes by 37% and crashes that involve an injury by 75%. At traffic lights the most common accidents are faster, right-angled collisions. These crashes are eliminated with roundabouts because vehicles travel more slowly and in the same direction. The most common accident is a sideswipe, generally no more than a cosmetic annoyance.
What locals like, though, is that it is on average far quicker to traverse a series of roundabouts than a similar number of stop lights. Indeed, one national study of ten intersections that could have been turned into roundabouts found that vehicle delays would have been reduced by 62-74% (nationally saving 325,000 hours of motorists’ time annually). Moreover, because fewer vehicles had to wait for traffic lights, 235,000 gallons of fuel could have been saved.
While I'm a bit skeptical of the time and fuel savings estimates there at the end, I do agree with the overall safety and convenience of traffic circles instead of lights. Here in the Triangle they are becoming more and more common. I have to admit that sometimes people do seem very confused by them, trying to turn left instead of going around and so on. However, this is because most driver education programs in the United States don't educate people about traffic circles, a problem that should be relatively easy to overcome. I'd be interested to hear from people who have spent time driving in countries with lots of traffic circles as to whether or not they agree with the claims of safety or convenience.