In this online engineering PDH course, an alternative form of multi-lane roundabout, called a “turbo roundabout,” is described. Though most roundabouts in the United States are single-lane roundabouts, multi-lane roundabouts are becoming increasingly common. Some of these multi-lane roundabouts have experienced higher than expected frequencies of sideswipe—same direction crashes. In the Netherlands in the 1990s, the turbo roundabout was introduced with the goal of influencing driver behavior and reducing lane change conflicts in a way that would address the crash types occurring in multi-lane roundabouts. In recent years, the Netherlands, Germany, Poland, and Canada have implemented turbo roundabouts with positive effects on safety. The turbo roundabout has the same general operating characteristics as modern roundabouts but utilizes notably different geometrics and applications of traffic control devices. This course describes turbo roundabouts, highlighting the design and traffic control features, operational capabilities, and potential safety benefits.

Topics: Characteristics of a turbo roundabout Potential benefits of turbo roundabouts User considerations Location considerations Safety analysis methods and results Operational analysis Design considerations Costs.

Intended Audience: This course is intended for civil and transportation engineers concerned with the design and construction of intersections. 

Publication Source: This course is based on the U.S. Department of Transportation FHWA Safety Program document, FHWA-SA-20-019, titled “Turbo Roundabouts”.