According to the Insurance Institute for Highway Safety, modern roundabouts reduce motor vehicle crashes. Their July 2001 Status Report noted "most serious kinds of crashes at conventional intersections are virtually eliminated by roundabouts…Crashes that do occur tend to be minor because traffic speeds are slower." The study reviewed 24 intersections around the U.S. that have been converted from stop signs or traffic signals to modern roundabouts. At those intersections, all crashes were reduced by 39%. Serious crashes were reduced by 76%. At the time of the study, there had been no fatalities at any of the new roundabouts. So, the study estimates that fatal or incapacitating injuries will be reduced by 90% at those intersections.

Why are modern roundabouts safer? For two reasons, they reduce speeds and they reduce the number of potential conflicts. The following graphics illustrate these points.

High-speed crashes are more likely to result in serious injury or death.

Fewer conflicts lower the crash potential. The following figure from a Michigan State University case study entitled "Converting Old Traffic Circles to Modern Roundabouts" shows the conflict points for a typical two-way, cross intersection (32 conflict points) and a roundabout intersection (8 conflict points)