Comparison of Single Point Urban Interchange and Diverging Diamond Interchange Through Simulation

Date of Award


Degree Name

M.S. in Civil Engineering


Department of Civil & Environmental Engineering & Engineering Mechanics


Advisor: Deogratias Eustace


In 1960, there were 74,431,800 vehicles registered in the United States. Looking at the most recent data currently available shows that in 2016 there were 268,799,083 registered vehicles in the United States. Roadway facilities constructed in the 1960s were not designed to handle vehicular traffic of these proportions. The ever increasing volumes of motor vehicle traffic at heavily traveled interchanges and intersections heighten the risk of single or multiple vehicle crashes particularly when they are not designed to manage high volumes. Traffic engineers from state and federal departments of transportation have responded to calls for safer roads and interchanges in some areas that have been identified as dangerous because of an increase in fatal and non-fatal motor vehicle crashes. In the road network the highway system and the local street system are related. According to the Federal Highway Administration, "the term interchange means the junction of two or more streets requiring partial or complete grade separation." Interchanges located in urban areas are utilized to facilitate traffic flow between arterial roadways and freeways on- and off-ramps. Congestion and safety are the two main objectives traffic engineers consider while remodeling an interchange design. Several types of renovated interchanges are normally considered to meet the growing population mobility needs. The Single Point Urban Interchange (SPUI) is one of the solutions has been considered since 1974 but it was flourished and implemented in the 1990s. The other innovative interchange solution appeared first in France in the mid-1970s known as Diverging Diamond Interchange (DDI). Likewise, the DDIs did not gain popularity back then until in the 2000s. The first DDI in the United States was constructed in 2009 in Springfield, Missouri.The main aim of this study is to compare the performance of traffic flow between SPUI and DDI based on existing traffic data for a peak hour retrofitting an existing Conventional Diamond Interchange (CDI). The analysis of the two interchange designs in conjunction with the existing design are used in the comparison study to identify which interchange design performs best among each other. The Measures of Effectiveness (MOEs) used in this study include queue delay, queue length, vehicle delay and stopped delay. This study obtain traffic turning movements and signal timing data from the Ohio Department of Transportation (ODOT). The turning movement counts (TMC) were taken from ODOT's Transportation Data Management System for the year 2017. VISSIM version 11 software was used for microscopic simulation. The optimum signal phasing for the three interchange designs were obtained from SYNCHRO 10 software based on the PM peak hour traffic data. The virtual interchange network design geometry in both software programs were almost identical. Several assumptions were made to stay consistent as much as possible while comparing the three designs since they have completely different geometric layouts. For example, the existing CDI data included the through movements from off-ramps to on-ramps. Since the two alternative designs (SPUI and DDI) exclude the through movements from off-ramps to on-ramps, their data were added to the right turn movements. Moreover, the speed limit was set to be in the range of 30 mph while driving in the interchange to meet all three design specifications.The analysis of results show that there are significant advantages and disadvantages associated with each design (CDI, SPUI and DDI). During implementation, various factors such as cost, efficiency, safety, delay, etc., need to be considered when attempting to select the best design, which would be the most appropriate method as these may vary from situation to situation. However, in the current study, a DDI performed best, followed by a SPUI, and then CDI was last. Moreover, CDI with its signal timing optimized very highly improved all MOEs considered when compared with the CDI with existing signal timing.


Civil Engineering, Transportation, Traffic simulation, Interchange, Conventional Diamond Interchange, Single Point Urban Interchange, Diverging Diamond Interchange

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