Governor Wolf, PennDOT Announce Completion of State’s First Diverging Diamond Interchange

August 17, 2017

Washington, PA –  Governor Tom Wolf today joined the Pennsylvania Department of Transportation, as well as local and elected officials, to mark the completion of the state’s first Diverging Diamond Interchange, or DDI, an innovative safety enhancement that upgraded and rehabilitated Interstate 70 from the north junction with I-79 to the Route 136 (Beau Street) Interchange.

“Our transportation mission is to keep people and goods moving safety and efficiently, and this project brings some of the latest industry improvements home for Pennsylvanians,” Governor Wolf said. “This interchange improves travel for the public and businesses, a goal that I’m committed to across the state.”

As part of its efforts to increase safety and mobility on I-70 in Washington and Westmoreland counties, PennDOT chose the DDI design because it could use much of the same footprint as the previous, substandard cloverleaf interchange, it minimized impacts to area businesses, and it would increase mobility and safety on I-70 and Route 19.

The first of its kind in the state and 73rd in the country, the DDI is similar to a standard diamond interchange but has three distinct differences:

  • Traffic on Route 19 crosses over to the opposite or left side of the roadway within the interchange area.
  • The left turn movements from Route 19 to the I-70 on ramps occur from the far-left side of the roadway eliminating the need to cross opposing travel lanes. The benefit is free flow left turns onto the I-70 ramps.
  • The left-turn movements from the I-70 exit ramps to Route 19 do not need to cross opposing travel lanes to gain access to the desired lanes on Route 19.

“As we maintain and upgrade our infrastructure across the state, we continually look for opportunities to put improved practices to work,” PennDOT Secretary Leslie S. Richards said. “This project brings together sorely needed improvements to safety and traffic movement alike.”

The interchange features guiding signage, pavement markings and additional arrows in the travel lanes to guide motorists through the DDI. Curbed islands were constructed to help guide motorists through the cross-overs and a concrete glare screen was installed between the cross overs along Route 19 to prevent distraction by motorists travelling in the opposite direction on the motorist’s right side. Also, traffic signals have two phases, unlike three or more phases at other interchanges and intersections, improving traffic flow due to fewer traffic cross points.

The department also developed a video simulation to show the DDI’s traffic flow to the public. The video and information on other I-70 improvements are available at

The $51.6 million project complements PennDOT’s work to improve safety and mobility in the area, including reconstructing I-70 between the junctions with I-79, adding a third lane in each direction and improving the interchange with Route 19 (Murtland Avenue) in South Strabane Township, Washington County.

Richards noted that the interchange upgrade is an example of how more work is needed on roads across the state, especially low traffic roads and Interstates. In February, Governor Wolf and PennDOT announced PennDOT’s Road Maintenance and Preservation initiative, or Road MaP, which will invest $2.1 billion in maintenance and highway and bridge capital projects over the next 10 years. Of the projects, $500 million will be allocated to an Interstate preservation and reconstruction program, bringing that total program, begun in 2016, to $1 billion over the next 10 years.

For more information on projects occurring or being bid this year, those made possible by or accelerated by the state transportation funding plan (Act 89), or those on the department’s Four and Twelve Year Plans, visit

Motorists can check conditions on more than 40,000 roadway miles by visiting 511PA, which is free and available 24 hours a day, provides traffic delay warnings, weather forecasts, traffic speed information and access to more than 825 traffic cameras.

511PA is also available through a smartphone application for iPhone and Android devices, by calling 5-1-1, or by following regional Twitter alerts accessible on the 511PA website.

For more PennDOT information, visit Follow local PennDOT information on Twitter at

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