WORTHINGTON — In the more than six years Worthington has had its trio of roundabouts, the northernmost traffic control circle has seen the largest share of rollover crashes.

From leaking milk to wayward hogs, tipsy tankers and livestock trailers alike have had the unfortunate experience of overturning.

The crashes — and the shared experiences of truck drivers — have had engineers with the Minnesota Department of Transportation (MnDOT) working on a better design for the big rigs. Changes to the shape and type of curb between the truck apron (the paved ring around the island in the middle of the roundabout) and the lane of travel are making the new roundabouts easier for truckers to navigate.

“The first number of roundabouts that MnDOT constructed, we weren’t nearly as aware of how important that curb was. It does look so intimidating to semi drivers,” said Scott Thompson, MnDOT District 7 traffic engineer.

While a lot of truck drivers try to avoid using the apron, Thompson said that defeats the purpose. So, MnDOT worked on improving the design.

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“We’ve continued to refine that curb shape and type,” he said. “We think we finally do have a good design that balances; allowing the trucks to use that truck apron with a minimal- to no-load shift.”

With all three of Worthington’s roundabouts featuring the higher curb, MnDOT is considering a return to the city to make the necessary curb modifications to improve maneuverability for big rigs.

The project would entail removing the two-foot-wide section of curb around the truck apron and replacing it with a modified curb design to better facilitate the truck’s transition to and from the truck apron.

Thompson said the modifications will help truckers feel more comfortable using the truck apron, while also minimizing or preventing load shift that’s currently happening when they take the curb.

While plans are still being developed for the Worthington roundabouts, the alterations likely wouldn’t be done this construction season.

“If something would happen, it would most likely be during the summer of 2021,” Thompson said.

Even with the curb retrofits in the roundabouts, drivers will still need to travel at a reasonable speed to navigate them.

“I think that a lot of the turning over we’re seeing (in Worthington) is either … high speed as well as wind,” Thompson shared.

While Worthington’s roundabouts will eventually be modified, others in the state may not be.

“I think it’s going to be on a case-by-case basis,” Thompson said. “In District 7, we are incorporating this new curb design in all of our roundabout construction projects that are coming up.”

District 7, which spans 13 counties in south-central Minnesota, has 28 roundabouts on the state highway system — more than any other district outside the Twin Cities metro area, according to Rebecca Arndt, MnDOT District 7 public information officer. Statewide, there are 96 roundabouts on the state highway system, with more being developed.

Thompson sees roundabouts as an important tool in the tool box for MnDOT, but notes it isn’t a one-size-fits-all solution.

A traffic safety study of roundabouts conducted by the state agency in 2017 shows an 86% reduction in fatal crashes and an 83% reduction in serious injury crashes at intersections where roundabouts have been installed.

“They really are a great tool to get traffic through an intersection while doing it safely,” Thompson said. “We would much rather have a couple more fender-benders than have someone lose their life or have serious injury.”

For more information on roundabouts, visit dot.state.mn.us/roundabouts.