The National Academies

NCHRP 15-72 [Active]

Identification of AASHTO Context Classifications

  Project Data
Funds: $300,000
Staff Responsibility: Christopher McKenney
Research Agency: University of Kentucky
Principal Investigator: Dr. Nikiforos Stamatiadis
Effective Date: 8/14/2020
Completion Date: 11/14/2021



NCHRP Research Report 855: An Expanded Functional Classification System for Highways and Streets served as a key reference informing the seventh edition of AASHTO’s A Policy on Geometric Design of Highways and Streets (Green Book). The new Green Book introduces a change in guidance for state transportation officials by introducing a broader set of land use context classifications (i.e., rural, rural town, suburban, urban, and urban core). These context classifications provide a mechanism for better targeting design solutions to specific contexts while providing needed flexibility to address planning and design needs.


The AASHTO Committee on Design has begun planning for the eighth edition of the Green Book and envisions a major restructuring. This includes organizing design guidance by the context classifications listed in the seventh edition with the addition of a context classification, "Industrial, Warehouse, or Port Roads." NCHRP Project 15-77, "Aligning Geometric Design with Roadway Context" will be drafting these chapters.


Many state, regional, and local transportation and planning agencies are interested in applying the new context classifications in their jurisdictions. The existing research and guidance, however, does not point to specific methodologies or parameters for implementing these context classifications. Research is needed to help agencies proceed efficiently and consistently.




The objective of this research is to develop practical guidance to assist state, regional, and local planners in identifying the appropriate context classification(s) for an area or a transportation project. Critical questions are (1) what are the context(s), (2) how will those context(s) change (spatially and temporally), and (3) what are the implications for the various travel modes.


The guidance should include:

  • Review of the six context classifications that are planned for inclusion in the eighth edition of the Green Book.
  • Discussion of development typologies (with illustrative graphics) that are often seen in these contexts.
  • A concise approach that uses readily available quantitative and qualitative data to identify a context. The approach should be defensible, replicable, and promote consistency while retaining flexibility for the user to address the particular needs of the area or project. The approach should be applicable at different scales (e.g., project-specific, corridor, regional and statewide planning).
  • Discussion of how areas that are on the border between two contexts and those whose development is changing (either planned or spontaneously) should be addressed. Greenfield projects and infill redevelopment efforts should be addressed.
  • Discussion of situations that may call for special considerations during design (e.g., schools, campuses, tourist destinations, areas with seasonal dynamics, historic neighborhoods, intermodal hubs).
  • Implications of the context classification for the various modes (i.e., automobiles, bicyclists, pedestrians, transit vehicles, trucks), including micromobility options, automated vehicles, and other emerging technologies.
  • Information that should be carried forward into a project’s purpose and need statement (as defined in the Green Book, Section 1.2), including modal priorities and considerations, project performance metrics (e.g., safety, target speed), and expected changes in land use to help align design decisions with planning objectives.
  • Implications of a context classification decision for an area or road on other departmental functions, such as demand modeling, access permitting, multimodal network connectivity planning, and system operations.
  • Approaches to calibrate the approach based on the specific characteristics of the region and agency, including possible subdivisions of the AASHTO context classifications.
  • Approaches to involve stakeholders and present results to decision-makers, developers, and the public that help to promote multidisciplinary collaboration and a common vision of the road and its surroundings.
  • Recommendations on how often a road’s context should be reviewed or updated.
  • At least three real world case studies illustrating the utility and limitations of the guidance using a range of project types, context classifications, and data sources.

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