Introducing the Super DDI as a Promising Alternative Service Interchange

Abstract

The diverging diamond interchange (DDI) is in widespread use all around the United States and is the most popular alternative design for failing conventional interchanges. While the DDI does well in efficiently moving large left-turn demands, it is not the best design for through traffic or pedestrians. This paper proposes the new super DDI as a substitute for service interchanges which can mitigate the limitations of the typical DDIs. Our study of the new super DDI included a comprehensive series of simulation tests in VISSIM to consider different aspects of the traffic operation. We also estimated the costs of constructing a super DDI and compared those costs to other interchange designs. The results confirmed that the proposed super DDI could perform significantly better than the existing designs under the conditions tested. Overall, the super DDI showed an 18% lower travel time and a 49% higher rate of completed tests (as an indicator of the capacity) when compared with a typical DDI. However, the construction cost was estimated to be higher. Hopefully, the results show that the proposed super DDI has potential as a promising alternative design and will inspire further research and testing.