By increasing capacity and reconfiguring the Interstate 435/Route 210 interchange in Kansas City, Missouri, the Missouri Department of Transportation (MoDOT) anticipates less congestion and improved safety at this critical location. 

“We are addressing multiple issues with this project,” says James Pflum, P.E., Resident Engineer for MoDOT. “When it’s done, the whole area will benefit.”

The $18.3 million project includes constructing a diverging diamond interchange, replacing twin bridges on I-435 above Route 210, which will allow for three lanes of traffic in each direction. The Statewide Transportation Improvement Program funded the project.

“The bridges were getting older, built 40 to 50 years ago, and they needed to be replaced,” Pflum says. “That interchange was not optimized for the amount of truck traffic coming through.”

Currently, about 100,000 drivers use the I-435/Route 210 interchange daily. Route 210, an important freight corridor, with several multimodal freight hubs in the vicinity, was recently widened to four lanes. This project will help accommodate the additional traffic.  

“In the morning, I-435 brings traffic into the city, and in the evening it takes people leaving the city back to the suburbs,” Pflum explains. “It was a bottleneck for traffic moving through.”

CDM Smith of Boston designed the project. Clarkson Construction Co. of Kansas City, Missouri, received the multiphased construction contract. The company, founded in 1880 by G.G. Clarkson as a grading company, has grown to become a major heavy contractor. In addition to road and bridge projects, the company performs site development and grading, power plant, airport, railroad and sewer construction. The company continues to be family owned and is now in its sixth generation of leadership. Bill Clarkson is the current CEO, Bill Clarkson Jr. is President and Billy Clarkson is Vice President. About 300 people work full time for Clarkson, during the peak construction season. 

Achieving the Common Goal

“We have turned the challenges into opportunities,” says Bryan Wilkerson, Senior Project Manager for Clarkson, who credits the job’s success to “engaging all the stakeholders to achieve a common goal – to deliver a high quality project and bring it in ahead of schedule and under budget.”

Clarkson began working on the project in fall 2016 with modifications to two surface roads. Construction of the northbound I-435 bridges was completed in 2017, and this year final construction of Route 210, the southbound I-435 bridges and the west half of the diverging diamond interchange will take place. The entire project is about half complete. 

During construction, Clarkson has kept two lanes of I-435 open to traffic and two lanes of Route 210 open to traffic during the peak periods, except while removing and reconstructing the bridges. Northbound I-435 was constructed in two phases last fall while maintaining all lanes of traffic, Wilkerson reports. Then the northbound and southbound traffic will be moved to the new northbound structure.

The two bridges are using concrete box girders, selected because of the clearance is greater with box girders, which are shallower than a steel structure. The bridges are topped with a standard reinforced deck. I-435 in that area is curved. 

“Building a bridge in a curve creates some challenges,” Pflum says. “It’s a lot of geometry. Nothing is typical.”

Wilkerson explains that the box girders are straight, and crews are varying the overhang width from 1 foot to 3.5 feet to accommodate the curve. 

During the weekend removal of a flyover bridge, all traffic on the interstate had to be diverted to city streets, which Pflum says required a lot of coordination. Crews used excavators to hammer the bridge down. MoDOT has provided notices to the public to keep people aware of the changes taking place.

Crews took a winter break from construction, starting in November 2017, when Clarkson returned the intersection to its original configuration and resumed work at the end of February. 

The project has required moving more than 140,000 cubic yards of dirt, and placing more than 60,000 square yards of concrete pavement. 

The Diverging Diamond

The diverging diamond interchange (DDI), now under construction, will create a smoother flow of left-turning traffic. Many of the trucks using the intersection make left turns onto the interstate. 

“In areas where we have a lot of left turning movements, the DDI provides a huge advantage,” Pflum says. “In the state of Missouri, diverging diamonds have become popular. We have seen good success with them in other parts of the area.”

The diverging diamond moves traffic to the left side of the roadway between the on and off ramps. As a driver approaches the intersection, the road will bend to the left, and cars coming from the opposite direction will be on the right. A concrete median will separate the opposing lanes. 

The cars entering the interstate will be able to drive onto the interstate ramps without facing oncoming traffic or stopping. Through traffic will cross back to the right side of the road at the next traffic light, explains MoDOT, which reports a diverging diamond interchange can reduce congestion by 50 percent and eliminate left-turn accidents and all type of crashes by 50 percent. 

“The main challenge is attempting to construct a DDI under traffic,” says Wilkerson, explaining that has required cooperation from the stakeholders and finding a balance between constructability, shutting the road down and enabling the traveling public to continue using the road. 

“We are working together to find solutions,” Wilkerson adds. 

Managing traffic while crews construct the diverging diamond is one of the project’s challenges, Pflum agrees. 

“We have to get the pavement built, go to a temporary DDI through striping to get drivers in the configuration we need,” Pflum says. “From there we will build the islands and hard surfaces that will separate the traffic. It’s a phased approach to getting the DDI open to traffic.”

Wilkerson says that the actual construction of a DDI consists of typical road work, with some complexity to sloping of the pavement in the bowties for drainage, but maintaining traffic during construction adds to the complexity. 

The projected is scheduled for completion later this year. 

“Once we get done, I think we are going to have a product that everyone will enjoy,” Pflum says. “It will help the area develop and keep growing.”

Project Partners

• Owner: Missouri Department of Transportation
• Design Engineer: CDM Smith, Boston, Massachusetts
• Contractor: Clarkson Construction, Kansas City, Missouri

Photos courtesy of Clarkson Construction