Over the last few decades, city planners and engineers have increased the usage of roundabouts over traditional intersections to improve traffic flow. While studies generally agree that roundabouts result in a dramatic decrease in motor vehicle collisions, the consequences to bicycle traffic is less consistent. And less encouraging.
The use of roundabout traffic controls has grown exponentially in the United States since the early 1990s. By removing stop signs and traffic signals, the roundabout reduces the various conflict points that drivers might face in a traditional intersection. Additionally, the roundabout generally reduces the speed of the traffic flow by having drivers follow a circular path. However, with these natural conflict reductions in place, introducing cyclists to the traffic flow can have dangerous consequences. A team of researchers from Utah State University did a literature review to uncover roundabout safety trends. Many of their findings were shocking:
- Installing a roundabout at a higher-speed intersection decreased the amount of cyclist collisions. Installing a roundabout at a lower-speed intersection increased the number of crashes involving cyclists.
- Multi-lane roundabouts tend to lead to more frequent and more severe collisions.
- Roundabouts with painted bike lanes within the traffic control increased collisions by nearly 33% in one study compared to roundabouts with no bike facilities.
- Nearly all (between 67% and 82%, depending on the study) collisions occur when the bicyclist is already in the roundabout and the motor vehicle is entering or exiting the traffic control.
While the roundabout might provide clear benefits for motorists, bicyclists often struggle with safety in this type of traffic control. According to the literature review, roundabouts with painted bike lanes are almost universally seen as less safe than other forms. It is important that city planners take all types of traffic into account when deciding on the format the intersection control will take.
