FRENCH CONNECTION

Engineers from Utah and Idaho recently took a close look at UDOT’s innovative interchanges during the Tour de DDI.

Engineer Gilbert Chlewicki, far right chats with Robert Miles, UDOT Region Two Area Engineer and David Stevens, UDOT Research Project Manager on the Tour de DDI.

A group of engineers gathered for a lessons-learned discussion and tour of UDOT Diverging Diamond Interchanges. Participants met at the Calvin Rampton Complex for review of the UDOT DDIs, then traveled to the SR 201, Pioneer Crossing and SR 92 DDIs stopping briefly at each location.

The event was held to coincide with a visit by Gilbert Chlewicki, a nationally known expert and proponent of the DDI. Chlewicki designed what he believed to be the first DDI in graduate school, then was surprised to find that a similar design was in operation in Versailles, France. Chlewicki spoke briefly about what circumstances make the DDI a better choice than a traditional Single Point Urban Interchange and about how to promote public knowledge and acceptance.

Though it’s “not a silver bullet” that will solve any traffic problem, Chlewicki believes the design is best used in an urban or suburban environment. In fact, Chlewicki predicts that the design should be considered first in an urban or suburban environment and will “make the SPUI extinct.”

Public perception of the DDI can be positive when communication stresses two messages, according to Chlewicki. Communicators need to explain how the DDI can reduce delay and make life better for road users and focus on how the design can actually improve safety. “As long as you explain it well” public acceptance is high.

Other presenters included:

  • Richard Miller, with Parsons Transportation Group lead designer of the Pioneer Crossing DDI
  • HG Kunzler with Lochner Engineering who designed the retrofit DDI at SR 201 and Bangerter Highway
  • Michael Lasko with CH2M Hill who designed the SR 92 DDI
  • Glenn Blackwelder, UDOT who discussed operations in Region Three
  • Marjorie Rasmussen, UDOT who discussed operations in Region Two

Designers gave an overview of the DDI design process and discussed lessons learned along the way, reviewed issues associated with “retrofit” DDIs, discussed “wrong way fear” and mitigations to help the driving public.  Glenn Blackwelder and Marjorie Rasmussen discussed current operations.

Blackwelder said the DDI is “the sportscar of interchanges,” because it’s fast, flexible and well-tuned. As a traffic engineer, he finds DDIs “fun to operate.” Although initial coordination can be tough and time consuming, operational changes make improvements and improve traffic flow.

Engineers from Idaho attended the event to prepare to design and construct a DDI in Chubbuck, Idaho. “We took some valuable information from the events of the day,” wrote Jesse Barrus in an email thank-you to UDOT following the event. “Being the engineer of record on this project I really appreciate the confidence I got from the operational standpoint of these innovative designs.”

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