The Pleasant Hill Road Diverging Diamond Interchange (DDI) is the first operating DDI in Gwinnett County, the second operating DDI in the state of Georgia and one of only a dozen that have been constructed in the United States. AECOM designed a DDI at the intersection of Pleasant Hill Road over I-85.
A DDI, or double crossover, is a type of interchange where the two directions of traffic on the secondary road cross to the opposite side of the road on both sides of the bridge to enter or exit the freeway. It requires traffic on the freeway overpass to briefly drive on the opposite side of the road from what they are accustomed. This unique design reduces traffic congestion and improves safety at the interchange for both vehicles and pedestrians.
The DDI configuration is a viable option due to its high cost-to-benefit ratio and minimal impacts to surrounding properties. The lower cost will be realized in construction, right-of-way, and staging activities.