Aligning Geometric Design with Roadway Context

Since 1984, AASHTO’s A Policy on the Geometric Design of Highways and Streets (the “Green Book”) and other roadway design criteria have been primarily based on a functional classification system of a hierarchical network composed of arterials, collector, and local roads. This classification was further assigned by an urban or rural designation. This system is described in detail in Highway Functional Classification Concepts, Criteria, and Procedures (FHWA-PL-13-026). The objective of this research is to draft Part IV (Facility Design in Context) of the proposed eighth edition of the Green Book (GB8), using a consistent structure for the context chapters and drawing content from the Green Book and research-based sources. This material should be suitable for direct use in a future project to develop the GB8, although the development of Parts I-III may prompt changes. One of the major changes is Part IV that will build upon the context classes in NCHRP Research Report 855 and Chapter 1 of the Green Book, seventh edition. Some of the reasons for this addition are: (1) The context classes better delineate the needs of all users of the roadway and provide a linkage to the land use. (2) The context class of the road will often influence design decisions more than the functional class of the road. (3) This approach better reflects the state of the practice and emerging design issues, including context-sensitive design, livable communities, practical design, and complete streets. (4) This organization could reduce redundancies in the existing Green Book text while also allowing more specificity in recommendations for design solutions and evaluation of tradeoffs. (5) These chapters should promote consistency in how these context classes are defined and applied across the United States. (6) The reorganization will allow a fresh look at the content of the Green Book and help identify areas for improvement. Research is needed to determine how the current design guidance in the Green Book and other good sources can be reorganized by context class. Production of the GB8 will be done in a larger, subsequent effort.

• Record URL:
  • http://apps.trb.org/cmsfeed/TRBNetProjectDisplay.asp?ProjectID=4766

Language

• English

Project

• Status: Completed
• Funding: $349,986.00
• Contract Numbers:

  Project 15-77

• 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
• Performing Organizations:

  Kittelson and Associates

  ,    
• Principal Investigators:

  Ray, Brian

• Start Date: 20200618
• Expected Completion Date: 20211217
• Actual Completion Date: 20211217

Subject/Index Terms

• TRT Terms: Context sensitive design; Geometric design; Highway design
• Subject Areas: Design; Highways;

Filing Info

• Accession Number: 01966176
• Record Type: Research project
• Source Agency: Transportation Research Board
• Contract Numbers: Project 15-77
• Files: TRB, RIP
• Created Date: Sep 18 2025 3:52PM