Improving Safety with a Mini Roundabout in Waterloo

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The intersection of W 9th Street and South Street in Waterloo – a busy intersection a few blocks from Highway 218 – was two-way stop sign controlled, with continuous traffic on one road. With stopped vehicles having trouble finding gaps to cross or join traffic, and several crashes at the intersection, it was determined that a mini roundabout would solve these traffic flow and safety issues while staying within the existing intersection footprint. Shive-Hattery provided concepts and a cost estimate for the City’s successful Traffic Safety Improvement Program (TSIP) application. The Iowa DOT funds covered more than half the cost of the project.

While the mini roundabout would provide a low-maintenance solution, education on roundabouts in general and the benefits of this mini roundabout was necessary, with multiple meetings with the City Council and public. While traffic counts showed minimal truck movements at the intersection, Shive-Hattery responded to concerns about large trucks’ ability to navigate the roundabout by including truck apron pavement behind the curbs at each corner.

The single-lane mini roundabout’s center island is fully traversable for larger trucks, while also forcing regular traffic to naturally slow down and preventing crashes. Drivers coming from all four directions are more easily able to find gaps to enter the intersection, decreasing idling time. Lighting design was also done, greatly increasing the street lighting for improved safety for pedestrians and vehicles. Pedestrians are also able to cross at all four legs, and a bench on the NE corner was added.