Four-way intersections are a ubiquitous aspect of transportation infrastructure, particularly in the U.S. These familiar stops are directed by traffic lights, which prevent collisions. However, an alternative intersection called the roundabout or traffic circle improves this design in several ways. They have been proven to be even safer, without stopping the flow of traffic, and on top of that they are more cost effective to maintain than stoplights. The implementation of roundabouts is a necessary step for America’s safety, though it should ideally remain gradual and focused on particularly dangerous crossings.
In Insurance Institute for Highway Safety (IIHS) released a study of 24 intersections before and after the switch to a roundabout was made. The results indicated that a roundabout has a 39% decrease in the incidence of collision. This doesn’t paint the whole picture though, as roundabout collisions see a 90% reduction in lethal or incapacitating injury. However, this is just an average. The most significant improvement is made with single lane intersections. When scaling up this design, there are diminishing returns. The roundabout only begins to fare worse than the alternative when sizing up beyond double laned roads, or when placed in tandem with other hazards such as railroads. In a majority of cases, the roundabout saves lives otherwise lost on four-way intersections.
A follow-up study measuring the effects on traffic flow and public opinion was published in 2006, which proves that roundabouts are faster on average. The IIHS determined, “Average intersection delays during peak hours at the three sites were reduced by 83-93%. Traffic congestion, as measured by the vehicle-to-capacity ratio, was reduced by 58-84%.” Additionally, the study finds that although only 38% of drivers approved of roundabouts before implementation in their town, this number rose to 50% after the project was completed.
Although the benefits of roundabouts are apparent, they are not as favorable as the stoplight to a large portion of the population. This reasoning cannot be overlooked when installing infrastructure intended for the public at large. A key point of backlash faced by cities that make the switch is the construction process. Although the traditional intersection and roundabout take a similar length of time, the phase of construction in which the intersection is entirely blocked off can extend past ten weeks. This estimated timeline has been provided by the Federal Highway Administration. Since they are unable to partially open until more than halfway finished, roundabouts are perceived as taking much longer than typical intersections to build. Another point is that other drivers are not always to be trusted. While the current curriculum of driver’s ed in the U.S. does include concepts such as yielding and merging, one can keep their license renewed for a lifetime without having to review this material. It is inevitable that unfamiliar drivers will run across roundabouts for the first time on the road. These considerations mean that measures like clear signage and public awareness campaigns are necessary to ensure drivers approach the road with confidence.
All together, the roundabout is best utilized alongside standard four-way intersections. Not every situation has a better outcome when they are implemented, but when placed with intention, lives can be saved.