The National Academies

NCHRP 20-07/Task 423 [Final]

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
Research Agency: Kittelson & Associates
Principal Investigator: Brian Ray
Effective Date: 6/14/2018
Completion Date: 6/13/2019


This project developed 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 was 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 included AASHTO committees dealing with related topics and external stakeholders, including professional societies, such as ITE, AMPO, and NACTO. .




The contractor's final report has been submitted to the AASHTO Technical Committee on Geometric Design and have been incorporated into their plans for the 8th Edition of the Green Book.




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.

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