Olsson Associates


Temporary diverging diamond configuration improves traffic congestion during construction

Wednesday, November 16, 2016

Reid Catt, Transportation

 It’s not often in the transportation industry that you get to work on a truly unique project—an approach that, to your knowledge, has never been taken before. With the U.S. 65 and Battlefield Road diverging diamond interchange (DDI) in Springfield, Missouri, Olsson was given that opportunity and designed a temporary DDI configuration as a form of traffic control. 

Before the project began and throughout the public involvement process, the major stakeholders and adjacent property owners made it clear that some form of temporary access across U.S. 65 was necessary. Without such access, the impacts to their businesses would be devastating. With this knowledge in hand, Olsson set out to investigate ways that we could go beyond the typical approach and achieve the goal of maintaining access during construction. 

Olsson knew that a DDI configuration works after construction, so it would likely serve the traveling public well during construction. We also estimated that using the temporary DDI configuration would increase the interchange capacity during construction between 60 and100 percent compared to what the traditional, split-phased traffic control configuration would have provided. 

Throughout the design process, we constantly revisited how the final design configuration would work with the temporary layout. For those looking at a DDI design in the future, here are a few things to consider:

  • Review the up-and-over movement on the ramps during the bridge demolition phase. Ensure that the existing and temporary traffic signals don’t conflict with this movement.
  • Even if no trucks are allowed, plan for them. This beckons to a twist on an old saying, “While you build it, they will come.”
  • Closely evaluate the effects on grade change on temporary pavement, excavation, and embankment and on overhead signal clearance.  

Another unique aspect of this project was that Olsson was allowed to work on “both sides of the fence” to help support the contractor, Hartman Construction. During construction, Olsson made adjustments to the traffic control plan to accommodate changes necessary from field observations. This highlights the level of trust Olsson developed with Missouri Department of Transportation (MoDOT) staff, proving that we have the professional integrity to serve all parties involved in a project.

At Olsson, we always seek to gather feedback, especially the type of information that is noted in the field. We followed up with the contractor to gain insight on what worked well, adjustments made in the field, and what they would have changed. Some of the notable benefits that the temporary DDI configuration includes are:

  • Increased capacity (over traditional split phase)
  • High level of control of the queue lengths on the off-ramps (contractor could switch the signal to flashing red to help clear ramps quickly)
  • Easy movement of construction equipment around the project site 

Some important lessons learned from this project include:

  • Allow for a reasonable amount of time during bridge demolition and the temporary DDI setup. Flying debris can lead to an unsafe situation.
  • Use water-filled or concrete barriers instead of temporary guardrail because it allows for greater flexibility for access and adjustments.
  • Use directional signing and temporary pavement markings, such as “cat tracks,” which are extremely helpful.
  • Consider bidding delineators and separator curb as separate colors. Also, consider bidding the price of each relocation.

Olsson’s design team worked across multiple offices and regions to bring the best resources possible to the project to ensure its success.

Also, it’s important to give credit where credit is due. MoDOT and Project Manager Stacy Reese were very open to trying an innovative approach. A temporary DDI wouldn’t have been a possibility without their support. The project went on to win the Best Use of Innovation in the small project category (less than $25 million) at the Mid-America Association of Transportation Officials awards and has been featured in Equipment World magazine.

If you have questions about the temporary DDI, please contact Reid Catt at 913.381.1170, or email him at rcatt@olssonassociates.com.

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