A 'live look' at a DDI intersection

July 17, 2014
A diagram showing the layout of the planned diverging diamond interchange at Murtland Avenue (Route 19) and Interstate 70

Washington commuters can't merge onto Interstate 70 from Route 19 via the planned “diverging diamond interchange” just yet, but they can take a virtual ride without leaving their homes.

Pennsylvania Department of Transportation unveiled local residents expressed overwhelming support for the new DDI design. The interchange is scheduled to open in spring 2017.

“This is the first use of this innovative design in Pennsylvania, and the new interchange will move traffic more efficiently while enhancing safety,” Joseph Szczur, district executive for PennDOT's District 12 region, said in a news release. “We wanted to give drivers an early view since the traffic patterns are not what people are accustomed to.”

The video shows both a bird's eye view of how traffic will move along the interchange and a driver's perspective. The interchange configuration requires traffic to cross over and switch lanes, with traffic signals directing the flow to allow motorists passage through the area or onto the interstate going in either direction.

Barry Lyons, PennDOT project manager, said PennDOT got the idea for the simulation video from similar projects in New York and North Carolina.

“We can try to explain to folks when you have a paper and a drawing in front of you and explain what it is, but the video itself gives you an aerial view and shows how it works, and you actually see the cars moving,” Lyons said.

Lyons said there are 35 DDIs in operation in 15 states, and about 100 more are currently being planned across the country. He said the average intersection has about 26 “conflict points,” or areas where accidents commonly occur, and the DDI has only about 13 conflict points.

“In theory, you'd think 50 percent less conflict points, crashes should be (cut by) 50 percent,” Lyons said, adding that studies revealed those exact results occurred at the first DDI constructed in Springfield, Mo., in 2009.

“In the end, we decided it was the way to go,” Lyons said of PennDOT's decision to construct a DDI in Washington.

Construction on the $57 million project begins in September. It also will increase traffic to three lanes in each direction on I-70 from the I-79 north junction to East Beau Street exit.

To view the DDI simulation, visit PennDOT's YouTube channel at www.youtube.com/pennsylvaniaDOT.

Emily Petsko joined the Observer-Reporter as a staff writer in June 2013. She graduated from Point Park University with a dual bachelor's degree in journalism and global cultural studies.

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