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Are mini roundabouts coming to your neighborhood?

Sarah Gengler, PE, PTOE | with 0 Comments

Are mini roundabouts coming to your neighborhood?

Another tool in traffic engineers' design toolbox is popping up in the Midwest. Two new mini roundabouts, similar to compact roundabouts, recently opened in Michigan. Designers placed these mini roundabouts at heavy-traffic intersections located only a few hundred feet from one another. Here's why these mini designs are gaining popularity:


Mini roundabouts offer a smaller footprint

Mini roundabouts are smaller in diameter than conventional modern roundabouts and have a fully traversable central island and splitter islands, making them easy for heavy vehicles to navigate. These smaller-scale roundabouts offer most benefits of modern roundabouts with the added value of a smaller design footprint. The UK has been using this kind of design for years, but this is a fairly new concept in the US that's most recently emerged in Michigan and Maryland.

Mini roundabouts keep traffic moving

Two mini roundabouts recently opened in Washtenaw County, Michigan. These intersections were previously controlled by all-way stops, which resulted in peak-hour delays and backups. All-way stop controlled intersections are held to the same standard level of service (LOS) as roundabouts, per the Highway Capacity Manual (HCM). The Transportation Research Board (TRB) generally recommends that stop-controlled intersections with wait times greater than 36 seconds be slated for improvement. In Washtenaw County's case, these new mini roundabouts accommodate the vehicle volume more efficiently, resulting in reduced traffic delays for commuters.  

Mini roundabouts are budget-friendly

The limited availability of right-of-way and budget can have a major impact on the feasibility of infrastructure improvement projects. In circumstances where a new traffic signal or a modern roundabout might require too much land or too many resources, mini roundabouts provide a viable, cost-conservative alternative.
Traffic engineers provide design solutions that promote safe and efficient traffic flows at intersections. Contact Sarah Gengler, PE for more information on planning a safe intersection.

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