Approximately a week ago I was notified by the Governor’s Office that the Perimeter Community Improvement District (CID) will be receiving a grant of $800,000 and a loan of $684,000 from the state infrastructure bank to construct a “diverging diamond” interchange at the junction of Ashford Dunwoody Road and I-285. The project will span as far south as the Ashford Green building and as far north as Perimeter Mall.
This begged the question: What is a diverging diamond interchange?
The answer: It’s an unusual interchange design where the traffic on the non-highway road (Ashford Dunwoody) drives on the opposite side of the road (the left-hand side) as it passes over the highway. It appears that this design will greatly improve traffic flow over I-285 and will be a remarkable improvement over the current layout.
Dunwoody City Councilman John Heneghan has posted more information on his blog, and there is a good article about the redesign in the Dunwoody Crier (click for links). You can find diagrams of the new layout in both places.
Construction is anticipated to begin in 2011.