Performance analysis of parallel flow intersection and displaced left turn intersection designs
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[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT REQUEST OF AUTHOR.] The displaced left turn (DLT) (also known as the continuous flow intersection (CFI)) design has proven to be a superior alternative to the conventional intersection in terms of handling heavy volumes during peak periods. In locations where the availability of additional right of way and driveway access is not a major concern, the DLT design is a cost effective and time saving option compared to the expensive option of grade separated interchanges. Recently, a new non-traditional intersection design called the parallel flow intersection (PFI) has been proposed. The PFI is also an at-grade design and operates with the same number of signal phases as a DLT. This research compares the operational performance of DLT and PFI designs based on the maximum through and left turn movement throughputs for three different high volume scenarios using traffic simulation. The results indicate that maximum throughput values of through movement in PFI were very close to the values obtained for DLT. The designs produced similar results mainly because both operate as two-phase signals (at the main intersection) with equal green times for through movements. The left turn movement throughputs in PFI were found to be lower than those at DLT. In particular, for two study cases, the DLT was able to process 180 and 80 more vehicles per hour per lane than the PFI. This can be attributed to the fact that, on average, the left turning vehicles experience greater number of stops in a PFI than they would in a DLT.
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