Converting the functionally obsolete cloverleaf interchange connecting I-70 and U.S. Route 19 into Pennsylvania’s first diverging diamond interchange required a traffic control plan to minimize disruptions to the tens of thousands of motorists who travel through the area daily. The project team says a carefully implemented three-phase strategy of temporary ramps, traffic signals and multiple interchange configurations during construction allowed the new interchange to take shape gradually during the more than three-year project without detours or major traffic delays.

The $49.1-million project in western Pennsylvania included adding eastbound and westbound travel lanes to a 1.5-mile stretch of I-70. It also involved redecking two existing bridges over Route 19 to extend their service life, an approach that eliminated the costs and complications of demolition and reconstruction. Along with offering proven safety and capacity benefits, the diverging diamond configuration proved to be the ideal solution for this location, the team says, because most of the construction work took place within the existing interchange right-of-way. The need for only two-phase traffic signals at ramp intersections also improves traffic flow.

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