Construction Begins on $7 Million Diverging Diamond Interchange in Delaware

DDI Groundbreaking 188X168
April 29, 2016Location: New Castle County, Delaware

On April 29, JMT joined Delaware Governor Jack Markell and Delaware Department of Transportation (DelDOT) Secretary Jennifer Cohan to celebrate the groundbreaking of Delaware's first diverging diamond interchange (DDI).

This $7-million project includes the design and construction of a modification to the existing SR1/SR72 interchange from a diamond interchange to a DDI, and the design and construction of Wilson Road connector and improvements to McCoy Road. JMT will serve as designer of record for this project, which is our first design-build in Delaware.

"When I became Secretary of Transportation a little more than a year ago, I made a commitment to innovation, and the diverging diamond interchange is one of the most innovative concepts in road design," Cohan said, according to a DelDOT press release. "Only 64 diverging diamond interchanges have been constructed in the United States, and the one at Route 72 and SR 1 will be the first one in Delaware. The diverging diamond here will enable vehicles to enter and exit SR 1 without having to cross lanes of oncoming traffic, improving safety and decreasing congestion, and it will cost a lot less than more traditional interchange arrangements. That is the sort of innovation we will continue to pursue at DelDOT."

The diverging diamond interchange is an unusual, yet innovative traffic engineering technique. According to DelDOT, “…it requires traffic on a freeway overpass to briefly drive on the opposite side of the road to make uninterrupted left turns. There is a significant improvement in safety, since vehicles [no longer need to] clear opposing traffic and all movements are discrete, controlled by traffic signals. The design has been successfully applied in other states, and is recognized as a cost-effective method [to improve] traffic flow and safety without widening an existing overpass.”