Development of a Roadmap for the Future of the Highway Capacity Manual to Support Multimodal Project Planning and Prioritization

Roadway capacity is an important issue to state departments of transportation (DOTs). Agencies routinely use the Highway Capacity Manual (HCM) to conduct multimodal planning studies for intersections, corridors, or small areas, and the results of HCM analyses feed into project prioritization and asset management programs. The HCM is also used frequently for quick turnaround analysis of work zone impacts and other operations scenarios. Recent feedback from state DOTs and other users of the HCM indicated that the current edition does not always meet the needs of agencies because of the increasing complexity of the methods, lack of easy-to-use look-up tables for capacity or back-of-the-envelope computations suitable for planning applications, and the sheer size of the manual, with over 2,500 pages not read or understood by the majority of users. With capacity and operations analysis remaining a critical need for state DOTs and local agencies, it is urgent to better align the content, length, and style of the HCM to address the needs of states. The needed tools and methods need to be re-envisioned to streamline state DOT analysis processes through a roadmap for the future of the HCM. The HCM was first published in 1950. It has evolved over the decades into the current 7th Edition, which is 2,563 pages supplemented by an online Applications Guide (Volume 4). Throughout its evolution, the HCM has continued to grow in breadth (e.g., more methods for more user types and facility types) and complexity (e.g., more detailed and complicated analyses). This growth has resulted in (1) a decreased understanding by many users of what is included in the manual and (2) a reliance on “black box” software tools without understanding the assumptions or limitations of the methods. The HCM has shifted away from providing the basic answers to “what is the capacity of XYZ?” and instead has produced increasingly complex methods that can hardly be completed by hand. There is a need to explore the purpose and vision of the HCM with users and stakeholders. The research should consider alternative structures and processes to meet transportation industry needs. The research also needs to consider alignment and coordination with companion documents, including the AASHTO Highway Safety Manual, AASHTO Policy on Geometric Design of Highways and Streets (Green Book), FHWA Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD), TCRP Report 165: Transit Capacity and Quality of Service Manual (TCQSM), FHWA Traffic Analysis Toolbox, and so forth. This project does not include an evaluation of recommendations for ownership and management of the resulting tool. A separate effort will address these issues based on the technical recommendations of this proposed project. The objective of this research is to outline the vision of and create a roadmap for the best future of, evolution of, or replacement for the next HCM.

• Record URL:
  • http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=5868
• Supplemental Notes:
  • Contract to a Performing Organization has not yet been awarded.

Language

• English

Project

• Status: Proposed
• Funding: $350,000.00
• Contract Numbers:

  Project 15-87

• Sponsor Organizations:

  National Cooperative Highway Research Program

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

  American Association of State Highway and Transportation Officials (AASHTO)

  444 North Capitol Street, NW
  Washington, DC  United States  20001

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Project Managers:

  Wadsworth, Trey

• Start Date: 20250526
• Expected Completion Date: 0
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Highway capacity; Multimodal transportation; Transportation planning
• Identifier Terms: Highway Capacity Manual
• Subject Areas: Highways; Planning and Forecasting;

Filing Info

• Accession Number: 01956609
• Record Type: Research project
• Source Agency: Transportation Research Board
• Contract Numbers: Project 15-87
• Files: TRB, RIP
• Created Date: May 28 2025 2:08PM