Roundabouts are without question the safest form of intersection traffic control, as concluded by a recent FHWA study. Statistics indicate that roundabouts can reduce intersection injury accidents by as much as 95% compared to signalized controls.

They are the only type of intersection that forces all vehicles to slow down. Crash rates are very low and crash severity is also less than other types of intersections. The Barry Crown Report states that the U.S. has about six times the population of the U.K., but sixteen times as many fatalities per year. The low rates in the U.K. (the lowest in the developed world) arise largely from the extensive use of roundabouts at high volume intersections and interchanges.

Source: FHWA Office of Safety.

Roundabouts are an effective traffic calming device since they force vehicles to reduce their speed upon approaching the intersection, thereby creating safer intersections for all users, including pedestrians and bicyclists. An important design characteristic of modern roundabouts is that every approach to the intersection must have a deflection, so that no vehicle path travels straight through the intersection without a reduction in speed. "Splitter islands" provide a storage area for pedestrians and crosswalks are usually located one to two car lengths behind the yield sign. A Dutch study of 181 intersections converted to roundabouts reported a 73% reduction in all pedestrian crashes and an 89% reduction in pedestrian injury crashes (FHWA-RD-00-067).

After three years of research, a Kansas State University research team has concluded that the modern roundabout is the safest and most efficient form of intersection control available today. In a recent Insurance Institute for Highway Safety (IIHS) study of 24 intersections in the U.S. where stop control and traffic signals were replaced with modern roundabouts, there was a 39% overall crash reduction, a 76% injury crash reduction and a 90% fatal crash reduction. These intersections were a mix of urban, suburban and rural environments. This study conclude, "results are consistent with numerous international studies and suggests that roundabout installation should be strongly promoted as an effective safety treatment for intersections." (Crash Reduction Following Installation of Roundabouts in the U.S., Insurance Institute for Highway Safety, Arlington, VA March 2000).

The Federal Highway Administration publication, Roundabouts: An Informational Guide, reports that "experience in the U.S. shows a reduction in crashes after building a roundabout of about 37% for all crashes and 51% for injury crashes." If only small to moderate single-lane roundabouts are considered, the reductions are 73% for injury crashes. Mean reductions in crashes after converting to a modern roundabout from other traffic control devices have been similar in other countries: Australia 41-61% for all crashes and 45-87% for injury crashes; Germany 36% all crashes; United Kingdom 25-39% injury crashes.

The state of Maryland has been a leader in the U.S. for modern roundabouts on state highways. The Maryland Office of Traffic Safety in 2001 reported on eight of the roundabouts which had been in use long enough for a before and after safety comparison. In spite of traffic growth, since conversion to roundabouts, the annual crashes dropped from an average of 5.0 crashes per year (before) to an average of 1.8 crashes per year afterwards, a 64% reduction. Crash severity dropped from an average of 3.0 injury crashes before to 0.5 crashes annually afterwards, an 83% reduction (details can be found at www.ksu.edu/roundabouts).