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Posted: May 22, 2012

Diverging Diamond Interchange

A redesign of the the I-285 Interchange at Ashford Dunwoody Rd.

Video simulation for the Perimeter Diverging Diamond traffic interchange


Can you DDI?  Employees, residents and visitors in the Perimeter area may soon be asking each other that question.

Beginning Monday, June 4 there will be a new way to travel through the I-285 Interchange at Ashford Dunwoody Road.

The Perimeter Community Improvement Districts (PCIDs) and the Georgia Department of Transportation (GDOT) have launched a project to radically redesign this busy interchange near Perimeter Mall to improve safety and traffic flow.  The new configuration is called a Diverging Diamond Interchange or DDI.   

The innovative DDI design shifts the flow of traffic to the opposite side of the road to reduce points of traffic conflict. 

“The DDI is a proven, cutting-edge, low-cost design that provides immediate traffic relief,” said PCIDs President and CEO Yvonne Williams.  “The DDI is being used successfully in four other states, but this will be the first DDI in Georgia.

“We’re expecting that under normal, free-flowing traffic conditions on surrounding highways, the I-285 and Ashford Dunwoody DDI will reduce traffic delays in evening rush hours up to 20 percent,” Williams said.  “There are significant safety improvements also with DDIs,” Williams noted. 

The PCIDs initiated Georgia’s first DDI when they hired Moreland Altobelli Associates to conduct pre-engineering studies and find a new concept for the I-285 and Ashford Dunwoody Interchange, which is a major gateway to Central Perimeter, the largest office market in Metro Atlanta.

DeKalb County and the State Road and Tollway Authority provided funding to the PCIDs for the pre-engineering and project design and the GDOT is funding the $4.6 million construction cost. 

GDOT has indicated that the DDI could become a model for congested interchanges throughout the state.

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