The National Academies

NCHRP 20-07/Task 423 [Active]

Planning for a Comprehensive Update and Restructuring of AASHTO’s A Policy on Geometric Design of Highways and Streets (8th Edition)
[ NCHRP 20-07 (Research for AASHTO Standing Committee on Highways) ]

  Project Data
Funds: $99,986
Staff Responsibility: B. Ray Derr
Research Agency: Kittelson & Associates
Principal Investigator: Brian Ray


This project will develop a detailed roadmap to develop and implement the 8th Edition of the Green Book that supports a flexible, multimodal, performance-based, and context-sensitive design process. A key element of this work will be to identify and engage a diverse set of stakeholders to vet the recommendations in the report, better identify the challenges that will be faced in development and implementation, explore solutions to those challenges, and build support for this radical change. These stakeholders will include AASHTO committees dealing with related topics and external stakeholders, including professional societies, such as ITE, AMPO, and NACTO. It is expected that many tasks in the roadmap will be submitted in the future for funding by the NCHRP, though alternative development approaches and funding sources should be identified where appropriate.

Since many state and local agencies are eager to begin to implement aspects of the process described in NCHRP Report 839, the plan should seek to support early adopters and benefit from their experiences.




The contractor has made presentations and solicited feedback from the AASHTO Council on Highways and Streets, Committee on Design, Council on Active Transportation, and NACTO. They are synthesizing the feedback and a meeting is planned for November 2018.




In 2016, the AASHTO Standing Committee on Highways passed a resolution that the Green Book should provide guidance to state DOTs and other users regarding flexibility in design. The resolution (Direction on Flexibility in Design Standards) also directed the guidance to address designing for a multi-modal transportation system and that changes should be coordinated with other AASHTO publications. The resolution recognized that both short-term and long-term steps would be needed to meet the goals of the resolution. 

AASHTO recently published the 7th Edition of A Policy on Geometric Design of Highways and Streets (the Green Book). The basic format, structure, and design philosophy are essentially unchanged since the 1984 edition which combined AASHTO’s rural and urban design policies (the Blue Book and Red Book, respectively). It does include some major changes in the Foreword and Chapter 1 that address issues raised in the AASHTO resolution (e.g., separate design approach for new vs. existing alignment, performance-based design, new land use context zones). Some key references for these changes are NCHRP Reports 785, 839, and 855.

To create a link to this page, use this URL: