Sensitivity analysis of operational performance under conventional diamond interchange and diverging diamond interchange

Rapidly growing traffic volumes and changes in traffic patterns over time have forced many intersections and interchanges into sub-optimal operation. Diverging diamond interchange (DDI) is one of many innovative interchange designs currently being proposed and implemented to better accommodate these changes. This study compares the operational performance of a conventional diamond interchange (CDI) and a DDI at different traffic volumes and turning movement combinations, and explores conditions for which one interchange design may be more advantageous over the other. To achieve this objective, traffic simulation models built using the microscopic simulation software, VISSIM, and procedures involving the Critical Lane Volume (CLV) method were used to conduct sensitivity analyses at different traffic conditions and to explore differences in delay, travel time, queue length, number of stops, and volume-to-capacity ratio between the two interchange designs studied. The results of the study show that the DDI will have better operational performance at high cross street traffic volumes with high left-turn ratio (above 50%), while the CDI will perform better at low cross street traffic volumes with low left-turn ratio (below 30%). The through/left proportion where the CDI and DDI has similar performance is dependent to the cross street cross sections. This study is one of the first to examine in detail the parameters and conditions that are best accommodated by the DDI related to conventional interchanges. Findings from this study can support planning and decision making processes associated with the implementation of DDIs.M.S