Proposing the Super DDI Design to Improve the Performance of Failing Service Interchanges in Denver Metro, Colorado

This study evaluates two versions of the new super diverging diamond interchange (Super DDI) design as a possible alternative to improve the performance of failing service interchanges in the Denver, Colorado, metro. Three interchanges, Interstate 225 and Mississippi Ave, Interstate 25 and 120th Ave, and Interstate 25 and Hampden Ave, were identified in Denver as the potential candidates to model for future retrofit. Several microsimulation models were created to test four interchange designs. i.e., existing conventional diamond interchange (CDI), diverging diamond interchange (DDI), Super DDI-1, and Super DDI-2. The traffic operation, safety, and pedestrian performance were evaluated using the combination of VISSIM, Synchro, and Surrogate Safety Assessment Model (SSAM) analyzing tools. As an important finding from this research, Super DDI designs outperformed DDI in terms of vehicular operation and safety when considering adjacent signals and when higher traffic demand exists, while DDI performed similarly or sometimes insignificantly better compared with Super DDI if no adjacent intersections were located in the vicinity and if the demand was lower than DDI’s capacity. On the other hand, the analysis of pedestrian performance showed that a relatively safe condition is expected for pedestrians in the proposed new Super DDI designs compared with CDI and DDI.

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  • Supplemental Notes:
    • This document was sponsored by the U.S. Department of Transportation, University Transportation Centers Program.
  • Corporate Authors:

    University of Wyoming, Laramie

    Wyoming Technology Transfer Center
    1000 East University Avenue, Department 3295
    Laramie, WY  United States  82071

    University of Mississippi, University

    Department of Civil Engineering
    University, MS  United States  38677

    Mountain-Plains Consortium

    North Dakota State University
    Fargo, ND  United States  58108

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Authors:
    • Haq, Muhammad Tahmidul
    • Molan, Amirarsalan Mehrara
    • Ksaibati, Khaled
  • Publication Date: 2022-6


  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos; References; Tables;
  • Pagination: 65p

Subject/Index Terms

Filing Info

  • Accession Number: 01852743
  • Record Type: Publication
  • Report/Paper Numbers: MPC-22-461
  • Contract Numbers: MPC-573
  • Created Date: Jul 25 2022 11:50AM