Operating Performance of Diverging Diamond Interchanges

2018Final ReportPDFTech ReportFHWA-GA-18-1228, 2006U97\ua00011746Diverging trafficDemonstration projectsDiamond interchangesInterchanges and intersectionsConventional\ua0Diamond\ua0Interchange (CDI)Operational\ua0EvaluationTraffic PatternsUnited StatesGeorgiaGeorgia. Dept. of Transporation. Office of Performance-Based Management and ResearchGeorgia. Dept. of TransportationGuin, AngshumanHunter, MichaelRodgers, MichaelGeorgia Institute of Technology. School of Civil and Environmental EngineeringGeorgia. Dept. of TransportationUnited States. Federal Highway AdministrationGeorgia. Dept. of Transportation. Office of Performance-Based Management and ResearchPark, Sun JunAnderson, JamesUS Transportation CollectionAs the result of changing traffic patterns, many conventional intersections and interchanges can no longer accommodate growing traffic volumes and heavy turning movements. In response, there are various innovative intersection and interchange designs proposed and implemented to better accommodate these changes, and the diverging diamond interchange (DDI) is one of these alternatives. This effort conducts a sensitivity analysis of conventional diamond interchange (CDI) and DDI operational performance under various interchange lane configurations, including the selected study area of the Jimmy Carter Blvd. and I-85 interchange in Norcross, Georgia, under varying traffic demands and turn-movement ratios. The sensitivity analysis explores the detailed conditions in which one interchange configuration provides superior performance over the other. The sensitivity analysis is structured into a two-step process with a critical lane volume (CLV) analysis as the first step, followed by a VISSIM microscopic simulation study as the second step. Overall, the study found that a CDI is likely the preferred option at locations with traffic volumes well below capacity and cross-street left-turn traffic proportions below 30% of the total cross-street demand, and a DDI is likely preferred at locations with traffic volumes near capacity and cross-street left-turn proportions exceeding 50% of the total cross-street demand.75