Olsson Associates


Springfield’s diverging diamond sparkles with innovation

Wednesday, April 22, 2015

Mary Sullivan, Communications

Schematic of Springfield's Route 65 and Battlefield Road diverging diamond interchangeSometimes it takes a couple of times to get things just right when doing something the first time. A few details are tweaked here and there, lessons are learned, and feedback is responded to. After a few trial runs, methods are perfected until a product is produced seamlessly. But every once in a while—through the persistence of a detail-oriented team—the nail is hit right on the head. Such was the case for Project Manager Kelly Turner and his team’s work on the Route 65 and Battlefield Road diverging diamond interchange (DDI) project in Springfield, Missouri. The project is scheduled to be complete by this fall.

It was the Transportation team’s first time working with a DDI, an up-and-coming design that improves interchange flow. A DDI uses traffic signals, gentle curving lanes, and striping to route drivers to the opposite side of the road. DDIs eliminate left turns against traffic, and, once through, brings drivers safely back to the correct side of the road.

Not many consultants have worked with the DDI design since it is still a relatively new concept in the transportation industry. However, upon delivering the design to the contractor and a third-party reviewer, Olsson received high praise for its work on the plans.

“We now certainly have a chip to play in future DDI project pursuits, and we have the ability to confidently present ourselves as experts,” Kelly said. “We should also remember this as a potential recommendation or solution to projects.”

The bridge at Route 65 and Battlefield Road had been scheduled for replacement because of deterioration and non-compliant freeway clearance. Kelly said the DDI design was requested for several reasons that included the following:

  • DDIs provide excellent capacity and traffic operations benefits, predominantly for areas with high left-turn volumes.
  • DDIs provide safety benefits by minimizing the likelihood of right-angle crashes, and they also reduce speeds through the interchange.
  • The two-phase operation effectively makes the left-turn movement a free-flow movement, rather than requiring a separate phase-and-yield condition.
  • Finally, for capacity improvement projects, the lower costs and shorter construction times are also selling points.

In addition to being the lead consultant for the project, Olsson provided the following design elements:

  • Urban interchange geometrics
  • Freeway
  • Bridge structural
  • Traffic operations analysis
  • Traffic signals
  • Intelligent Transportation Systems
  • Traffic maintenance
  • Construction phasing/constructability

Kelly also noted four specific design solutions the team developed that provided great benefits to the project:

  • The team developed a design that would allow for three lanes of traffic in each direction across the bridge. This provided even more added capacity than what the Missouri Department of Transportation (MoDOT) originally planned.
  • To accommodate a traffic signal east of the bridge, the team modified the profile to provide a flatter slope through the intersection, while still avoiding negative impacts to the adjacent properties and utilities. This solution went a long way in creating goodwill and public support for the project.
  • The team designed a temporary DDI configuration to be used throughout construction to accommodate the area’s high traffic volumes. It allowed for a tremendous increase in capacity and reduced delays from what would have occurred with traditional, reduced-interchange operations during construction. The temporary DDI is currently in place and performing very well.
  • Olsson’s design to replace the existing bridge will require installing new piers in the freeway median, which will necessitate closing the inside traffic lanes. Recognizing the continued need for six lanes of traffic throughout construction, Olsson’s design replaces the existing shoulder beneath the bridge with a wider, full-depth pavement shoulder that could be used as a third lane and would maintain the needed freeway capacity.

“I am so proud of the job the team has done and continues to do during construction,” Kelly said. “Both MoDOT and the contractor have heaped praise and thanks upon our team for our work on this project.”

Update December 2015: Springfield's Diverging Diamond project was completed in the fall of 2015.

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