Modeling Highway Capacity and Level of Service for High-Volume Freeways: Multiple Weaving Areas

The Highway Capacity Manual provides concise, well-defined procedures for estimating capacity and level of service for most types of roadways and intersections. While not perfect, these procedures allow for a quick comparison of roadway geometries when making design decisions. The current Highway Capacity Manual (HCM 2016) does not provide procedures for evaluating multiple weaves, which occur when three ramps are close enough to each other. The goal is to create simple-to-use macroscopic models of multiple weaving segments. The research team is using microscopic simulation (VISSIM) to find relations between the macroscopic variables flow, density, and speed. Capacity is estimated by gradually raising flows for a range of geometries and flow ratios. Models are developed to express capacity in terms of lane configuration, flow ratios, truck percentage, and overall flow rate. Also, the impact of distances between the ramps and the percent trucks on the quality of service will be measured. VISSIM provides point measurements, such as flows and time mean speeds as well as link measurements, such as density and space mean speeds. There are three indications that capacity has been reached, (1) measured flow is less than that specified, (2) a drop-in space mean speed with increasing flows, and achieving a density defined as capacity. The team plans to provide a procedure to allow analysts to evaluate capacity and quality of service in multiple weaves without having to resort to simulation. A benefit of this research is to minimize total travel time per month for families. Implementing this research results will help individuals and families not only to save on travel time, but also gas and car maintenance costs in the long term. Once the research results are ready, the data could be useful to Texas Department of Transportation (TxDOT), North Central Texas Council of Governments (NCTCOG), and other agencies to assist in their planning function. Furthermore, the research results can significantly help in reducing traffic congestion over road networks. It is anticipated that people who are benefitting from these research results will live a less stressful life due to reduced travel time and cost.


  • English


  • Status: Active
  • Funding: $15000
  • 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:

    TREC at Portland State University

    1900 SW Fourth Ave, Suite 175
    P.O. Box 751
    Portland, Oregon  United States  97201
  • Performing Organizations:

    University of Texas at Arlington

    Box 19308
    Arlington, TX  United States  76019-0308
  • Principal Investigators:

    Khademi, Sheida

  • Start Date: 20201102
  • Expected Completion Date: 20210831
  • Actual Completion Date: 0
  • USDOT Program: University Transportation Centers

Subject/Index Terms

Filing Info

  • Accession Number: 01758783
  • Record Type: Research project
  • Source Agency: National Institute for Transportation and Communities
  • Contract Numbers: NITC-1463, 69A3551747112
  • Files: UTC, RIP
  • Created Date: Nov 23 2020 3:31PM