Researchers studied crashes and injuries at 24 intersections before and after construction of roundabouts, and the study showed a 39 percent decrease in crashes and a 76 percent decrease in injury-producing crashes. Collisions involving fatal or incapacitating injuries fell as much as 90 percent. The use of roundabouts also reduced delays in traffic by as much as 75 percent. Roundabouts, also referred to as traffic circles, have triangular islands at each entrance, which slows down approaching vehicles. No stopping is required as vehicles approaching yield to circulating traffic.
Roundabouts allow all cars to move continuously through intersections at the same low speed.
The speed in roundabouts depends on the intersection, but generally it remains at about 15 mph. At that speed, drivers and others on the road have more time to react, resulting in a smaller chance of collision. When crashes do happen, most will be minor. Indiana has eight metropolitan areas included in the study. Many cars have bumpers that prevent some of the damage that can lead to expensive repairs after low-speed collisions, but this is not true for most sport utility vehicles and pickup trucks.