BACKGROUND 

The Highway Capacity Manual (HCM) was first published in 1950 to address highway planning, design, and operations. Throughout its 75-year history, the HCM has evolved to meet transportation planning and engineering needs, especially as agencies attempt to incorporate modes beyond motor vehicles. This evolution has resulted in additional methods, increased complexity with analyses, and results that can be difficult to convey. The scope and scale of the current (7th) edition of the HCM seems to be lessening rather than increasing many users’ understanding of the contents, including methods and calculations, and there is growing concern that practitioners are increasingly relying on proprietary software to help with analyses. Often, practitioners must use more than one proprietary tool in tandem, or seek methods developed outside the scope of the HCM to conduct their analyses.  

The dilemma for the HCM user community is that the software or methods underpinned by the HCM can be used without understanding the assumptions or limitations of the methods. Further, practitioners' ability to use the HCM for basic analyses has diminished and they can no longer complete these analyses by hand in certain instances. Training on the HCM in university or on-the-job settings is also increasingly difficult. With planning, design, operations, and traffic impact analyses remaining a critical need for transportation agencies, research is needed to target the content, scope, scale, and format of the HCM to user needs. 

OBJECTIVE 

The objective of this research is to collaboratively develop the vision for the next generation of the HCM and prepare a roadmap to implement the vision. 

Accomplishment of the project objective will require at least the following tasks. 

TASKS 

Task descriptions are intended to provide a framework for conducting the research. The NCHRP is seeking the insights of proposers on how best to achieve the research objective. Proposers are expected to describe research plans that can realistically be accomplished within the constraints of available funds and subaward time. Proposals must present the proposers' current thinking in sufficient detail to demonstrate their understanding of the issues and the soundness of their approach to meeting the research objective. 

The sequencing of tasks and associated deliverables such as technical memoranda or summary reports shall be structured in the same cadence as quarterly progress report (QPR) submissions so that technical content can be reviewed at the same time as a QPR. The overall research plan must be organized into three phases. The first phase shall be for background research to inform the proposed second-phase tasks. The third phase shall be reserved for preparing the final deliverables and should not exceed 6 months. At the end of each phase, the research team shall deliver an interim report and updated research plan for the next phase. One month shall be reserved for review of each report followed by an in-person meeting for the first-phase report and a virtual interim meeting after the second-phase report. NCHRP approval is required to advance to the next phase.

The proposer shall plan to engage the HCM community of practice throughout the research project, with a focus on the TRB Intersection and Roadway Capacity and Quality of Service Committee. An engagement plan shall be included in the proposal. Engagement activities should help the research team identify HCM user types, capture and synthesize user needs, and establish the vision and roadmap as stated in the project objective.

Note: NCHRP discourages using survey questionnaires for this project and suggests guided interviews, virtual focus groups, or other methods as appropriate. 

The tasks in the proposed research plan should address/include:

• A literature and practice scan focusing on capacity analysis and its future prospects. Similar international manuals should be explored for format, usage, and agency implementation.
  
  
• Engagement of the HCM community of practice throughout the research plan.
  
  
• Identification of the user groups and their respective uses for the HCM.
  
  
• Exploration of the HCM’s role in the future planning, design, and operations of the various transportation modes.
  
  
• The HCM’s relationship to other transportation specifications, manuals, or guides used by transportation planners and engineers.
  
  
• Identification of components of the HCM that currently meet user needs, where gaps exist in addressing needs, and components that have been superseded by progress in research and practice and need to be updated or removed. 
  
  
• Exploration of the organization of the HCM to better meet user needs. Consider solutions that could improve access to and navigation of the HCM, such as creating modules; cross-referencing sections, methods, or calculations inside the manual; or clarifying the HCM's place/intended use in the context of other reference manuals transportation planners and engineers use for planning, design, and operations.
  
  
• Knowledge management techniques to retain methods and background material on the theories and concepts in prior versions of the HCM. 

• Articulation of a clear vision and preparation of a roadmap for the next generation of the HCM that can be sustained and updated over time with changes in mobility (e.g., e-scooters, e-bikes, connected or autonomous vehicles), technology (e.g., artificial intelligence), and transportation policy and priorities (e.g., community-oriented transportation concepts or the safe systems approach).

• Exploration of implementation techniques to educate or train the user community on the next generation of the HCM.
  
  

Note: The roadmap should sufficiently outline the format and contents of the next version of the HCM. At a minimum, it should identify the content to keep, improve, promote, or move to an appendix. The roadmap shall also include a draft research problem statement for the TRB Intersection and Roadway Capacity and Quality of Service Committee to consider submitting to the NCHRP to fund the implementation of both the vision and roadmap.

At a minimum, the final deliverables are:

• A conduct of research report that documents the entire research effort, and the vision and roadmap for the next generation of the HCM. 
• A PowerPoint presentation with speaker notes that summarizes the project and illustrates for a broader audience how the research can be applied.

Note: Following receipt of the draft final deliverables, the remaining 3 months shall be for NCHRP review and comment and for research agency preparation of the final deliverables.

SPECIAL NOTES

A. The proposer should consider the following resources when preparing the research plan:

• Kondyli, A., M. Tabatabaei, and K. Mahajan. 2025. NCHRP Synthesis 652: Traffic Capacity Level of Service: Adaptations and Usage. Transportation Research Board, Washington, DC. https://doi.org/10.17226/29143.

• Perrin, R. J., T. H. Boggio, J. J. Winebrake, and E. H. Green. 2018. NCHRP Synthesis 529: How Transportation Agencies Assess the Value of Added Capacity Highway Projects Versus Other Modal Projects and Strategies. Transportation Research Board, Washington, DC. https://doi.org/10.17226/25222.

• Dowling, R. G., and A. Elias. 2012. NCHRP Synthesis 427: Extent of Highway Capacity Manual Use in Planning. Transportation Research Board of the National Academies, Washington, DC. https://doi.org/10.17226/13537. 

< < < IMPORTANT > > >

I.   The brochure Information and Instructions for Preparing Proposals for the Transportation Research Board’s Cooperative Research Programs includes extensive guidance on the preparation of proposals for submission to CRP. Revisions to these instructions are highlighted in yellow within that document.

II.  Proposals will be rejected if any of the proposed research team members work for organizations represented on the project panel. The panel roster for this project can be found at https://www.mytrb.org/OnlineDirectory/Committee/Details/7235. Proposers may not contact panel members directly; this roster is provided solely for the purpose of avoiding potential conflicts of interest.

III. The text of the final deliverable is expected to be publication ready when it is submitted. It is strongly recommended that the research team include the expertise of a technical editor as early in the project timeline as possible. See Appendix F of the Procedural Manual for Subawardees Conducting Research in the Transportation Research Board’s Cooperative Research Programs for technical editing standards expected in final deliverables.

IV. The required technical memorandum (no more than 10 pages) titled “Implementation of Research Findings and Products” should address the following implementation frameworks: (1) Effective Products; (2) Implementation Stages; (3) Implementation Drivers; (4) Implementation Teams; and (5) Product Feedback. For more information on the frameworks, read the TR News article “Active Implementation at the National Cooperative Highway Research Program: Frameworks for Moving Research into Practice,” available at https://www.nationalacademies.org/osdocs/NCHRP20-44_ActiveImplementation-TRNews.pdf.

VI. The National Academies have an ethical and legal obligation to provide proper attribution whenever material from other sources is included in their reports, online postings, and other publications and products. TRB will review all Cooperative Research Programs draft final deliverables using the software iThenticate for potential plagiarism. If plagiarized text appears in the draft final deliverable, the research team will be required to make revisions and the opportunity to submit future proposals may be affected.