The future 8th Edition of A Policy on Geometric Design of Highways and Streets (Green Book 8) will reflect the dramatic evolution of the nation’s transportation systems.
In 1984, the American Association of State Highway and Transportation Officials (AASHTO) published the first edition of the Green Book, a compilation of specifications and guidelines for geometric design. Keeping pace with the industry, AASHTO publishes new editions every few years – the most recent being the 7th edition, just released in 2018. AASHTO is now conducting a visioning effort to consider the 8th edition.
Over the years, the Green Book has been a primary reference to provide design guidance on highways and streets. Continued shifts toward increasingly multimodal transportation networks, however, make it natural for this industry resource to shift too. Responding to a resolution to integrate further flexibility into design standards, even before the 7th edition was finalized, AASHTO knew the 8th edition had the potential for a comprehensive update. As transportation planners and designers work to meet the full range of road users, they need more than structured dimensional guidance; they need performance metrics that embrace a comprehensive and flexible design approach to support project decision-making.
Green Book 8th Edition Visioning Process
Last March, AASHTO selected Kittelson & Associates, Inc. (Kittelson) to lead the Green Book 8 Visioning Project. Kittelson conducted outreach and an information review to first establish a “Green Book 8 Vision,” then a “Roadmap” to bring the vision to reality.
As part of the literature review, the team evaluated substantive documents/resources related to or applying performance-based approaches to planning and design. Kittelson compiled a summary that will serve as a foundation and bibliography for future efforts to advance Green Book 8 visioning. In the outreach effort, Brian Ray, Senior Principal Engineer, and Julia Knudsen, Senior Engineer, conducted numerous visioning sessions and gathered feedback from transportation professionals across the industry.
National conferences, webinars, conference calls, and additional supplemental meetings were critical components of this visioning process. Discussions held outside of primary in-person meetings enhanced the conversations initiated during conference events, introduced the Green Book 8 Visioning Project and focus areas to enhance future discussions, and provided continuous opportunities for a variety of stakeholders to engage.
The meetings were set to accomplish the following goals:
- Acquire performance-based evaluation approaches and processes suggested for the Green Book 8 framework.
- Find possible concepts and applications from the literature review to be integrated into ideas for the Green Book 8 vision and roadmap for implementation.
- Gain input from national professionals to help create a coherent and cohesive structure for forming the Green Book 8 vision.
- Assess content from in-person meetings and validate information to create concepts for a common Green Book 8 vision.
“Essentially, we are taking what we heard and learned and presenting that as the Green Book 8 Vision. The Roadmap is a prioritized plan, topics and actions we see as working towards attaining this vision, leading to the eventual publishing of Green Book 8,” Brian said.
The goal of the visioning process is to help move the industry toward a true, performance-based approach in establishing roadway designs that are adaptive to their specific contexts.- Brian Ray, Senior Principal Engineer
“It’s moving to integrate performance metrics that meet the full range of users and consider metrics that inform project decision-making comprehensively. This is a change from historical approaches of following published dimensional guidance. Instead, we can develop facilities that reflect the best way to meet various user needs,” he said.
TRB 2019 and Beyond
Kittelson will lead a workshop on the Green Book 8 Vision and Roadmap during the Transportation Research Board’s (TRB) 2019 Annual Meeting in January. The TRB workshop will be the last primary in-person meeting of the visioning process. It will be focused on sharing and validating the draft Roadmap and visioning ideas.
Kittelson’s recommendations will be published in the spring, and Brian pointed out this is just the beginning for how TRB attendees can participate in helping to make the changes outlined in the Vision and Roadmap.
“Attendees can seek to be early adopters to first understand and try to integrate the principles and values from the Green Book 8 visioning. As early adopters, they could change up and advance how they conduct their work,” said Brian, adding that while Green Book 8 may not be published for a few years, states and agencies can adapt and revise their guidance and practices much faster. They can do so while considering the Green Book 8 vision.
Collectively, the industry can begin moving toward practicing in the Green Book 8 Vision so that when Green Book 8 actually is developed and published, it's validating and supporting where the industry is already heading.- Brian Ray, Senior Principal Engineer