Update of Highway Capacity Manual: Merge, Diverge, and Weaving Methodologies

Freeway congestion usually occurs at freeway merge, diverge, and weaving segments that have the potential to develop bottlenecks. To alleviate or mitigate the impacts of congestion at these segments, a number of active management operational strategies have been implemented such as ramp metering, hard shoulder running, managed lanes, etc. The current freeway merge and diverge methodologies in Chapter 14 of the 6th edition of the Highway Capacity Manual (HCM) were developed over 25 years ago using limited field collected data. Although weaving segment analysis was updated more recently, the relationship with the merge and diverge methodologies have not been clearly addressed. In addition to limited data, the methodology does not conform to the fundamental relationship of traffic flow, namely that flow is the product of speed and density. The HCM does not offer any methodology for lane drops or additions, which often occur in the vicinity of freeway merge/diverge segments. In the past decade, the data available to traffic engineers have expanded exponentially with ubiquitous sensor coverage of urban freeways and probe vehicle coverage of entire roadway networks. These new datasets provide a wealth of information to support the development of updates or changes to the merge, diverge, and weaving segment methodologies, and potentially complement traditional data sources. The objectives of this research were to (1) develop methodologies to update the HCM related to merge, diverge, and weaving methodologies; and (2) pilot the developed methodologies to demonstrate the full range of applicability of the proposed updates to the HCM.


  • English


  • Status: Completed
  • Funding: $400000
  • Contract Numbers:

    Project 07-26

  • Sponsor Organizations:

    National Cooperative Highway Research Program

    Transportation Research Board
    500 Fifth Street, NW
    Washington, DC  United States  20001

    Federal Highway Administration

    1200 New Jersey Avenue, SE
    Washington, DC  United States  20590

    American Association of State Highway and Transportation Officials (AASHTO)

    444 North Capitol Street, NW
    Washington, DC  United States  20001
  • Project Managers:

    Abu-Hawash, Ahmad

  • Performing Organizations:

    Kittelson & Associates, Inc.

    2 E. congress St.
    Ste 705
    Tucson, AZ  United States  85704
  • Principal Investigators:

    Schroeder, Bastian

  • Start Date: 20190610
  • Expected Completion Date: 20221231
  • Actual Completion Date: 20221231

Subject/Index Terms

Filing Info

  • Accession Number: 01672239
  • Record Type: Research project
  • Source Agency: Transportation Research Board
  • Contract Numbers: Project 07-26
  • Files: TRB, RIP
  • Created Date: Jun 18 2018 7:25PM