AASHTO Green Book 7th Edition (GDHS-7) - Highway and Street Geometric Design Policy, 2018 with 2019 Errata

The AASHTO Green Book, officially titled "A Policy on Geometric Design of Highways and Streets," is a comprehensive guide for highway and street design published by the American Association of State Highway and Transportation Officials (AASHTO)

The current edition is the 7th Edition, released in 2018, with errata published in October 2019.

The Green Book is used by transportation engineers, urban planners, landscape architects, and policymakers involved in the design and construction of highways and streets.

The book is divided into chapters covering various aspects of geometric design, including:

• New Framework for Geometric Design
• Design Controls and Criteria
• Elements of Design
• Cross Section Elements
• Local Roads and Streets
• Collector Roads and Streets
• Rural and Urban Arterials
• Freeways

Key updates include:

• A new first chapter on the framework for geometric design
• Updated research and practices
• Expanded guidance on context-sensitive solutions and design flexibility
• Introduction of contextual classifications

The 7th Edition presents a more flexible, multimodal, and performance-based framework for geometric design compared to previous editions.

The traditional functional classifications are:

• Local roads and streets
• Collectors
• Arterials
• Freeways

The new contextual classifications are:

• Rural
• Rural town
• Suburban
• Urban
• Urban core

The 7th Edition introduces a new approach for using functional and context classifications together to create more flexible and performance-based designs for both new projects and existing roads.

The book provides guidance on selecting appropriate design speeds based on functional classification, terrain, and other factors.

The Green Book offers detailed information on designing curves, grades, and sight distances for various road types and speeds.

The book covers intersection design, including types, sight distance, channelization, and special considerations for different intersection configurations.

The 7th Edition includes expanded guidance on accommodating pedestrians and bicyclists in road design, reflecting a more multimodal approach.

Yes, the book provides information on designing for transit operations, including bus stops and dedicated transit lanes.

The 7th Edition emphasizes a performance-based approach, allowing designers to tailor solutions to specific project contexts and needs.

Context-sensitive solutions refer to designs that consider the surrounding environment, community needs, and multimodal users, not just vehicular traffic.

While the book provides guidance on cross-section elements, it emphasizes that designs should be tailored to specific project needs rather than using a one-size-fits-all approach.

The book covers clear zone requirements, roadside barriers, and other safety considerations for the area adjacent to the traveled way.

While not inherently a legal standard, many jurisdictions adopt the Green Book as part of their design standards, potentially giving it legal weight.

AASHTO typically releases new editions every 5-10 years, with the 7th Edition published in 2018.

The errata document addresses technical revisions and corrections to the 7th Edition.