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Roundabout how-to

Roundabouts

A roundabout is a type of intersection that is proven to keep traffic moving safely and efficiently. St. Louis County Public Works just completed constructing a roundabout near Chisholm as part of the Highway 5 re-alignment project. Meanwhile, a roundabout is in the final design stage for the intersection of Midway Road and Maple Grove Road in Hermantown.

Why use a roundabout instead of a traffic signal?
Traffic signals are not safety devices. Most serious crashes within Duluth, Hermantown and Proctor occur at signalized intersections. This is because traffic signals do not eliminate high speed, right-angle conflict points. By definition, crashes at traffic signals are due to drivers running the red light.

Roundabouts are designed to virtually eliminate high speed, right-angle crashes. This is because vehicles enter the roundabout at an angle and low speeds. Overall, a roundabout creates an environment of lower speeds and reduces conflict points compared to a standard intersection. The lower speeds and reduction of conflict points creates a safer intersection, especially in terms of crash severity.  

Additionally, traffic signals are inefficient when there are few vehicles driving through an intersection. Drivers commonly find themselves waiting at a red light when no other vehicles are arriving on the street with a green light. When approaching a roundabout, if there are no other vehicles in the roundabout, drivers simply continue into the roundabout and on their way. 

Learn more about Roundabouts from the MN Department of Transportation.


Hermantown Roundabout - project overview

St. Louis County completed an Intersection Control Evaluation (ICE) study for the intersection of Midway and Maple Grove Roads. The ICE study recommended that a single-lane roundabout is the best form of traffic control for this intersection to improve safety and reduce delay/congestion.

The crash rate for this intersection is above the statewide average for similar intersections. The most common type of crash at this intersection is a right-angle crash. These types of crashes have the greatest potential for resulting in serious crashes. In addition to the crash concerns, there is also excessive delay on Maple Grove Road during the afternoon peak hours (4 to 6 p.m.)

PowerPoint presentation from Public Meeting

Animated rendering of roundabout at Midway and Maple Grove Roads

 
Proposed Design
The proposed roundabout includes a northbound to eastbound right-turn bypass lane. The bypass lane is intended to provide right-turning traffic on Midway Road to Maple Grove Road an opportunity to do so in advance of the intersection. Occassionally there are long platoons of vehicles making this movement, and the bypass lane facilitates moving vehicles through the intersection.
Artist rendering of proposed Hermantown roundabout
The proposed roundabout also includes bike ramps, which provide bicyclists the option to exit onto a bike slip ramp and bypass riding through the roundabout on the roadway.
 
Project Benefits
St. Louis County’s goal is Toward Zero Deaths on all county roadways. Roundabouts are proven to significantly reduce serious crashes because they eliminate high speed, right-angle conflicts that usually result in severe crashes. A roundabout at this intersection is expected to reduce serious crashes by nearly 90 percent.

A roundabout is also expected to significantly decrease the delay for traffic on Maple Grove Road. Overall, the single lane roundabout will provide the lowest delay compared to all other options, including a traffic signal and side-street stop control.

The proposed roundabout is designed to accommodate all modes of traffic, including large vehicles. Larger trucks are allowed to track upon the interior truck apron to negotiate the intersection.  


Additional Questions?

If you want to learn more about what's being proposed or want to offer input, and are unable to attend the public meeting, contact Traffic Engineer Vic Lund at (218) 625-3873. 

 

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