Effect of Large Vehicles on Left Turn Gap Acceptance at Signalized Intersections

Driver gap acceptance behavior is a function of geometric and operational factors. An essential measure of gap acceptance is the critical gap. At signalized intersections with permissive left turn movements, the critical gap is the foundation to estimate left turn capacity. Several studies have identified geometric, temporal, spatial, and operational effects on the critical gap estimates. However, recommended critical gap values have remained unchanged for decades. The Highway Capacity Manual recommended critical gap for left turns at signalized intersections is 4.5 seconds and the follow-up headway is 2.5 seconds. Most conventional signal optimization software (PASSER, SHYCHRO, VISSIM, SIDRA, HCS) use these outdated critical gap and follow-up headway estimates without accounting for specific traffic conditions such as large vehicles affecting gap acceptance. As part of this study, observational data and gap acceptance estimates with the presence of large vehicles will be integrated with microsimulation and signal optimization software to evaluate the effect of large vehicles in operational performance of left turning vehicles at signalized intersections.


  • English


  • Status: Completed
  • Funding: $ 74977
  • Contract Numbers:


  • Sponsor Organizations:

    Office of the Assistant Secretary for Research and Technology

    University Transportation Centers Program
    Department of Transportation
    Washington, DC  United States  20590
  • Managing Organizations:

    University of Iowa, Iowa City

    National Advanced Driving Simulator, 2401 Oakdale Blvd
    Iowa City, IA  United States  52242-5003
  • Performing Organizations:

    University of Wisconsin, Madison

    Department of Civil and Environmental Engineering
    1415 Engineering Drive
    Madison, WI  United States  53706
  • Principal Investigators:

    Noyce, David

  • Start Date: 20200601
  • Expected Completion Date: 20210531
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers

Subject/Index Terms

Filing Info

  • Accession Number: 01738859
  • Record Type: Research project
  • Source Agency: Safety Research Using Simulation University Transportation Center (SaferSim)
  • Contract Numbers: 69A3551747131
  • Files: UTC, RIP
  • Created Date: May 7 2020 12:53PM