Divergabout Design Wins Several Awards

The American Public Works Association Kansas City Chapter announced that the US-50 @ MO-291S Interchange was chosen for its Public Works Project of the Year (Transportation Project category – over $5 million but less than $25 million) and the American Council of Engineering Companies of Missouri announced the interchange was selected for its Engineering Excellence Competition Honor Award. The innovative divergabout design used in GBA’s winning entries was a joint effort with the Missouri Department of Transportation and the city of Lee’s Summit.

Aerial view of US-50 and MO-291S during the construction phase.

What started out as a simple bridge replacement project became an innovative interchange concept to improve mobility and facilitate future growth through a heavily traveled corridor. The concept used, a divergabout, is a brand-new layout which includes a diverging diamond interchange (DDI) at one ramp terminal and a roundabout at the other.

Originally, a DDI, which is less than a decade old concept, was considered for this project because of its ability to ease congestion in areas where there are heavy left turn volumes. However, the proximity of an outer road and a nearby water park made a cross-over at the north ramp terminal impractical. A common solution for such closely spaced intersections is a roundabout and thus, one of the first divergabouts in the state of Missouri was born.

“MoDOT is well-known for developing cutting-edge interchange configurations,” said Anne Schroer, GBA’s project manager. “GBA’s experience and expertise in developing and optimizing innovative designs made this a successful partnership from the start.”

Using a roundabout and diverging diamond interchange prevented any additional renovation to outer roads, while improving traffic issues.

GBA was hired by MoDOT to refine and optimize this unique concept. The scope of the team’s role included development of preliminary, right-of-way and final plans, which included detailed design of the interchange layout, designing two bridges, four retaining walls, ramp and intersection improvements, a frontage road realignment, storm sewer design, pavement marking and signing. All of this was done while ensuring the project was easily constructible and had minimal impact to traffic. GBA partnered with TREKK Design Group for lighting and signal design and Radmacher Brothers Excavating for construction. The project was completed six months early, with the divergabout fully open to traffic in just one year.

The divergabout design opens the door to outside-the-box thinking when compared to traditional, often symmetrical interchange types. In this case, the design provided long-term time and cost savings by reducing the number of traffic signals in the interchange and avoiding any outer road relocation. It also decreased the number of conflict points in the interchange, which will lead to fewer crashes.

In addition to APWA KC Chapter’s Project of the Year, this project also received an Excellence in Concrete Award from Concrete Promotional Group and Engineering Excellence Honor Award from the American Council of Engineering Companies Missouri. The US-50 @ MO 291S Interchange (divergabout) will serve as a model for unique and innovative solutions that serve our nation’s growing transportation needs.

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