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Roundabouts: Trending Again

The construction of roundabouts is on the rise across the United States. The goal of a roundabout is to control heavy traffic and disperse cars in a safe and well-organized manner.  For many of us, navigating a roundabout is a fairly new experience. Let us help you gain a better understanding of how and why roundabouts are being constructed.
Many people confuse roundabouts with their unpopular counterparts, the traffic circle and the rotary. The main differences between a traffic circle and a roundabout are size and speed. Roundabouts tend to run between 25 and 70 feet in diameter, with a speed limit of 15 to 25 mph; traffic circles span between 300 and 600 feet, with speed limits of 30 to 50 mph. With cars traveling along a broader surface area at much faster speeds, traffic circles are viewed as a danger to drivers. A University of Maine study’s findings show crashes are 3.5 to 6.5 times more common in traffic circles than in modern roundabouts.

Like traffic circles, rotaries are larger and operate at significantly higher speeds than roundabouts and commonly feature two-directional traffic flow. Rotaries are also more likely to be two-lane, which allows for multi-lane weaving, and consequently, more opportunities for accidents. The universal issue with rotaries and traffic circles is traffic volume.  They operate well in low traffic situations, but become more dangerous in heavier traffic. This may explain the resistance to roundabouts in the United States.

In addition to the previously mentioned differences between roundabouts and rotaries/traffic circles, roundabouts have been statistically shown to reduce collisions and increase traffic efficiency. A recent study by the Insurance Institute for Highway Safety entitled "Crash Reductions Following Installation of Roundabouts in the United States" compared modern roundabouts to traditional four-way intersections. The results of this study were staggering.  The study shows roundabouts reduced injury collisions by 76%, incapacitating and/or fatal collisions by 90%, and collisions of all varieties by 39%. In the case of traditional intersections, “T-bone” and head-on collisions occur most often; whereas in a roundabout, a side-swipe or rear-end collision is the most common form of accident, which is much less likely to be fatal.
Roundabouts are also valuable from an economic standpoint.  On average, construction is the same as traditional intersections.  Initially, they require more open space than traditional intersections, but have fewer lanes and less possibility for expansion. Roundabouts cost less to operate and can be environmentally friendly with the addition of landscaping. Federal Highway Administration (FHWA) statistics show the public is likely to have a negative view of roundabouts before construction; however, opinions turn positive once experiencing the benefits a roundabout provides.  Roundabouts can be an attractive, safe, and cost-effective alternative to standard intersections.

When a community expresses interest in the installation of a roundabout, there are factors which must be considered before interest can become action. How do you know if a roundabout is the right choice for you and your community?  A roundabout feasibility study can be conducted to determine if the circumstances are appropriate, or feasible, for a roundabout. The roundabouts themselves are compact, but their constant circular motion requires them to be built with additional surrounding space.  Land space must be considered because distance between lanes and adjacent structures must be well thought out to avoid unnecessary impairment. This means if there are curbside businesses or buildings around an intersection, a roundabout may not be the best option. Consultants conducting a feasibility study must carefully analyze traffic volumes and patterns before they can recommend constructing a roundabout. According to Professional Engineer and head of our Rockford location’s Transportation Department, Mick Gronewold, the circumstances need to meet a specific set of criteria. There must be enough available land and right of way, as well as a balance between traffic management, patterns, and flow. “Transportation is a science,” Mick explains. “Variables fluctuate, and just because a township thinks a roundabout is the best option, does not mean it is.”  As a general rule, roundabouts are an effective solution to a congested, substandard intersection, but it is important to run the appropriate tests before diving in head first.

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For more information on roundabout feasibility studies, please contact us at 815-235-7643.  


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