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Speth et. al., (2008) compares the operational benefits of the DDI to a diamond and a single point urban interchange. was used Synchro program to develop an optimum timing plan for each scenario. The traffic signals were coded as pre-timed to reduce the variability in results that can occur when simulating semi or fully actuated signal control. Speth found that the diamond interchange concept has significantly fewer conflict points, and most notably, only two crossing points. Table 2 shows the total number of conflict points that where found for each interchange design.Speth noted that the number of simultaneous points of conflict, which do not exist in the diverging diamond interchange concept, as any vehicle entering the intersections can only be struck one direction. The paper stated that the conflict points of a DDI require significantly less yellow and all red time to control, which in turn give less lost time and more green time and more capacity. In this study, the traffic operations of the three interchange designs were compared for four different volume scenarios in order to get a good understanding of the conditions that affect each of the interchange types.The conclusions extracted by these study was that the DDI configuration increases in value of different MOEs with more volume, especially with the increase of ramp volume. The least beneficial scenario was found to be when the arterial volumes are heavy, and the ramp interchange traffic is lower. The DDI operated better than a conventional diamond in all scenarios, in spite of having fewer lanes in the bridge area, and as the volume increased, the more benefit the DDI became over the conventional diamond, even when running with fewer lanes and having the diamond having protected-permitted phasing. Some of the recommendations were that a comparison of the diverging diamond interchange concept to other interchange configurations, including partial clover leaf and diamond interchanges with roundabout ramp terminal intersections should be conducted.
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