PennDOT completes state’s first diverging diamond interchange

Updated Sep 7, 2017
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Sr70 T20 3 LgThe Pennsylvania Department of Transportation has completed the state’s first diverging diamond interchange located at the junction of Interstate 70 and Route 19.

“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,” says Gov. Tom Wolf said. “This interchange improves travel for the public and businesses, a goal that I’m committed to across the state.”

DDIs eliminate left turns that have to clear opposing traffic, a design that is useful in high-traffic areas. They can cut down on congestion, improve safety, and move traffic along faster than traditional interchanges. The Missouri Department of Transportation installed the first DDI in the country in Springfield in 2009.

PennDOT says it selected a DDI design for the interchange because the agency 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.

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

This DDI offers a few differences from a standard version of the interchange:

  • 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.