I-70, Section T20 Reconstruction and Widening

The design and implementation of the DDI means that traffic now crosses over to the left side of the roadway within the interchange. It also means that left turn movements from Route 19 to the I-70 entrance ramps are free flowing, occurring from the far left side of the roadway, and left turns from the I-70 exit ramps are directly into the Route 19 travel lane. Because of these features, traffic conflict points are reduced to 14 compared to 26 in conventional diamond interchanges. The DDI also reduces traffic platooning on I-70 entrance ramps. To adapt the configuration to the local topography, the design team provided a 2 percent superelevation to Route 19, which was on a reverse curve alignment. The team also developed a traffic control plan that kept vehicles moving safely along I-70 and through the interchange as it was being rebuilt. Because the DDI fits primarily within the old interchange footprint, right-of-way impacts were minimized, and no businesses were displaced.

The design retained the existing I-70 bridges over Route 19, saving millions of dollars by avoiding replacement. Both bridges were redecked to extend their service lives. The westbound bridge was raised to increase the vertical underclearance from 14 feet, 2 inches to 16 feet, 6 inches. Improvements to I-70 included widening the highway to four lanes in each direction between the Route 19 and Route 136 interchanges, which provides auxiliary lanes between the interchange ramps. A new decision lane at the widened I-79 North Junction interchange offers motorists easier access to I-70 westbound and I-79 northbound. All of the improvements result in a safer trip for tens of thousands of motorists every day.

• Third travel lane in each direction for added capacity on I-70, with a fourth lane added between the closely spaced Route 19 and Route 136 interchanges, improving traffic flow.
• To sustain its longevity, I-70 was replaced with a concrete pavement structure expected to extend the service life of the interstate system.
• A new major fork condition created a decision lane along I-70 westbound approaching the I-79 North Junction interchange, which improves traffic flow.
• Existing bridges over Route 19 were redecked to extend service lives, provide bridge barriers that meet interstate safety requirements, and avoid costly mainline bridge replacement.
• Widened the existing I-70 westbound bridge over Route 1009 (Locust Avenue) adds third travel lane for increased capacity.
• Decorative stone in ramp island areas reduce the amount of impervious surface in the project, which prevents flooding and lessens stormwater runoff.
• Aesthetic treatments include colored concrete in islands and median areas.

• Award of Merit/Highways and Bridges, MidAtlantic Region, 2018, Engineering News-Record (ENR), Regional Best Projects.
• Community Connection Award, 2018, Associated Pennsylvania Constructors (APC).
• Project of the Year Award, 2018, American Society of Highway Engineers (ASHE) Northeast Region.
• Project of the Year Award, 2017, American Society of Highway Engineers Southwest Penn Section.
• Civil Engineering Achievement Award, 2017, American Society of Civil Engineers (ASCE) Pittsburgh Section.
• No. 7 Road, 2017, Roads & Bridges, Top 10 Roads.
• Excellence in Concrete Award, 2017, PA Aggregates and Concrete Association (PACA).

• DDI has 12 fewer traffic conflict points than a traditional diamond interchange.
• Added travel lane in each direction means less congestion and improved safety.
• Minimal impacts to private property, including commercial development.
• Vehicle access maintained during construction.
• Saved millions by avoiding dual three-span mainline bridge replacement.