Roundabouts, circular intersections where drivers travel counterclockwise around a center island, have no traffic signals or stop signs. Instead, drivers yield at entry and exit at the desired street. Though less common than signal light and stop sign counterparts, roundabout intersections are safer than lights and signs, and less expensive to maintain, according to a report by the Washington State Department of Transportation (WSDOT). 

Citing a study released by the Insurance Institute for Highway Safety (IIHS), the WSDOT says roundabouts typically reduce injury crashes by 75 percent at intersections where stop signs or signals were previously used. The WSDOT says roundabouts deliver:

  • a 37 percent reduction in overall collisions,
  • a 90 percent reduction in fatality collisions and
  • a 40 percent reduction in pedestrian collisions.

According to the WSDOT, the reasons for the reduction of serious collisions at roundabouts are three-fold.

Travel speeds are low in a roundabout. Drivers must slow down and yield to traffic before entering a roundabout. Speeds in a roundabout are typically 15 to 20 mph. Because of this, the few collisions that occur in roundabouts are typically minor.

A roundabout has no light to beat. Roundabout intersections are designed to promote a continuous, circular flow of traffic. Since traffic never stops in a roundabout, drivers have no incentive to speed up to “beat the light,” as they might in a traditional intersection.

Traffic only flows one way through a roundabout. Roads leading into a roundabout are gently curved to direct drivers to travel counterclockwise through the intersection. The curve in the road and single direction of travel eliminate the possibility for a T-bone or head-on collision.

According to WSDOT materials, drivers are hesitant to when it comes to using roundabouts; however, after using one, the number of drivers who favor them more than doubles. The IIHS study found that, before construction, the number of drivers in favor of a roundabout was 31 percent, with 41 percent strongly opposed. After driving on the roundabout, 63 percent were in favor with 15 percent strongly opposed. 



The WSDOT reports that after installing a roundabout, delays at an intersection can be reduced by 50 percent or more, fuel consumption can be reduced by up to 30 percent and with no traffic signal upkeep, a roundabout intersection can save up to $5,000 per year in maintenance costs.