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.

Interchanges are a particularly important focus in transportation because of the high level of interacting cross-traffic. Often, traditional diamond interchanges are limited in their ability to provide adequate safety and operational needs. Alternative interchanges are a common solution that involve using innovative designs which work well with specific site characteristics. Because there are often many alternative designs to consider and because it can be time-consuming to model and evaluate each alternative, there is a need to expedite the process using a designated screening approach and evaluation. This thesis contains an interchange study for a corridor located in Columbia, Missouri that uses a screening process which incorporates analytical and simulation tools. Several interchanges are analyzed including: diamond, single point urban (SPUI), partial cloverleaf, diverging diamond interchange (DDI), displaced left turn (DLT), roundabout, and an innovative displaced left roundabout (DLR). The results of operational analysis show that: the DDI performs the best on the interchange for high demand; the DLR performs best for the interchange only at low demand; the current design is sufficient with the given growth volume, so an alternative is not warranted. One contribution of this thesis is the development of a systematic procedure that first screens for promising designs and then conducts an extensive simulation analysis to compare their performance.

Tight diamond interchanges (TDI) and single point urban interchanges (SPUIs) are generally types of interchanges that can be used interchangeably in areas where right-of-way is constrained. There are limited amount of research conducted regarding the operational analysis and comparison of these two interchanges. The research that has been done regarding this topic are outdated and generally conclude that SPUIs perform better or about the same. Without knowing the true performances of the two interchange designs, it would make it difficult for engineers and planners to choose between the two interchanges. This research study will use the current updated version of the micro-simulation software, PTV VISSIM to analyze and compare the performance of the SPUI and the tight diamond interchange. The research will look at reconstructing a current tight diamond interchange into a SPUI in Wilsonville, Oregon to see how it will perform. The analysis was conducted for 7 varying volume levels for both the interchanges including the existing volume conditions. The volume conditions include multiplying the ramp volumes by 0.75, 1.25, and 1.4 as well as doing the same for the eastbound and westbound movements. The results of the analysis shows that the SPUI performs similarly compared to the tight diamond interchange for lower volume conditions, but perform very poorly for higher volume conditions. The SPUI in this location is more sensitive to volume change and does not perform as well as the tight diamond interchange. The SPUI performs better than the TDI by only 1.4 seconds for low ramp volume conditions with regards to average delay per vehicle and performs 31.2 seconds worst for high ramp volume conditions. Therefore, the SPUI should not be implemented at this location as it is not feasible for high volumes and not cost effective. SPUIs should be implemented carefully as it is not suitable for all places.

This research compares two interchange types, the Tight Urban Diamond Interchange (TUDI) and the Four Phase Single Point Urban Interchange (40SPUI). The 40SPUI is referred to in this report as a Single Point Urban Interchange with Frontage Roads (SPUI/F). The objectives of this research were to: (1) evaluate the SPUI/F based on available accident data and conflict analysis techniques, right-of-way and construction costs, and operating efficiency; (2) compare the performance of the SPUI/F and the TUDI; (3) evaluate current SPUI/F design assumptions and operation and recommend design and/or operational changes to enhance performance; and (4) evaluate the interchange form selection (pre-design) process and recommend changes where appropriate. The research found no significant difference in the safety aspects of the two interchange types. The SPUI/F generally did not perform as well operationally as the TUDI, with increased SPUI/F delay as the distance between frontage roads increased.