AASHTO Green Book (GDHS-7)

A Policy on Geometric Design of Highways and Streets, 7th Edition, 2018, commonly referred to as the Green Book, contains the current design research and practices for highway and street geometric design. This edition presents an updated framework for geometric design that is more flexible, multimodal, and performance-based than in the past. The document provides guidance to engineers and designers who strive to make unique design solutions that meet the needs of all highway and street users on a project-by-project basis. Not only are the traditional functional classifications for roadways (local roads and streets, collectors, arterials, and freeways) presented, but also an expanded set of context classifications (rural, rural town, suburban, urban, and urban core) to guide geometric design. The completely rewritten Chapter 1: A New Framework for Geometric Design, introduces the updated approach to design, with specific design guidance throughout each chapter.