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Posted by Nathan Currie, P.E.
Although Alabama does not have as many roundabouts as some of its neighboring states, such as Florida or Georgia, these intersections are becoming more common throughout the state. This could be due to the Alabama Department of Transportation (ALDOT)’s 2015 release of a Roundabout Planning, Design, and Operations Manual providing the framework and guidance for bringing more roundabouts to the state.
As opposed to traditional signalized or stop-controlled intersections, roundabouts are a circulatory intersection in which entering traffic yields to vehicles which are either circulating around a central island or exiting the roundabout. Once entering the roundabout, traffic moves in a counter-clockwise direction. When driving a roundabout, it’s important to remember to yield to traffic approaching from your left.
Roundabouts have several great benefits: they can increase efficiency, have a more pleasing aesthetic appearance, and require less maintenance. In many cases, roundabouts are also less costly to construct. But the greatest benefit of selecting a roundabout for intersection control is safety performance. According to the American Association of State Highway and Transportation Officials (AASHTO) Highway Safety Manual, roundabouts reduce the potential for fatal or injury crashes by close to 80%, when compared with traditional signal or stop-controlled intersections. This reduction in serious crashes is the result of the roundabout’s unique design characteristics that remove left-turn movements and keep vehicles traveling at similar low speeds through the intersection.
The Federal Highway Administration (FHWA) and American Association of State Highway and Transportation Officials (AASHTO) have written informational guides about design and analysis of roundabouts. These are generally recognized as the industry standard. ALDOT’s Roundabout Planning, Design, and Operations Manual provides guidelines and recommended practices for planning and designing roundabouts within Alabama.
I have worked on roundabout projects in Georgia and now in Alabama. I have seen first-hand how an effective roundabout can be well-received by the surrounding community and produce improvements to traffic efficiency and safety. More roundabouts in Alabama will be a good thing.