21-02 — Leading Approaches to Implementing Context-Based Classification of Roadways in Planning and Design

Original Scope: The recently released 7th edition of the AASHTO “A Policy on Geometric Design of Highways and Streets (Green Book)” introduced the concept of context-based classification of roadways, intended to ensure that roadway designs are appropriate for the settings in which they are built and operated.  The new guidance introduced a broader set of land-use context classifications (including rural, rural town, suburban, urban, and urban core) to better match design solutions to specific contexts and provide flexibility in developing project scopes with traditional functional classifications of roadways (local roads and streets, collectors, arterials, and freeways).

The Green Book does not present specific methodologies or parameters for applying the new context classifications.  Some agencies seeking to take advantage of the flexibility made possible by these new classifications (for example Florida, New York, Connecticut, and the State of Washington) have implemented context classification in their own design guidance.  The objective of the scan is to describe the experiences gained in such leading states and lessons learned that may be valuable to others who have not yet implemented context-based classification.

The scan is planned to be conducted as a virtual peer exchange (Type 4 Scan). In addition to providing an opportunity to document and compare how leading states have implemented Context-Based Classification within their jurisdictions, the scan should encourage a more uniform implementation of guidance across the country and allow for a common language to develop nationwide, promoting greater cooperation and sharing among practitioners.  The scan also will provide information for the AASHTO Committee on Design to consider in the development of the next version of the Green Book.

Implementation and Impact

Three scan team members are serving on the steering committee to develop the 8th Edition of the AASHTO Policy on Geometric Design of Highways and Streets (Green Book}. This new version will be different from the previous version in that it will not be organized by roadway classification, but rather by context. 

Two scan team members are serving on the advisory committee for NCHRP 20-44 (51) Developing Training Materials to Implement Context Classifications. This project is a follow up to NCHRP 1022 Context Classification Application, which developed practical information to help agencies identify appropriate context classifications – and – was informed by this scan, which described states’ experiences with implementation of context classification. 

Tennessee DOT is updating its current roadway design guide, based on information gained from this scan. The updated version will include revised context classification. The plan is to publish this updated guide in September 2024. 

TRB hosted a webinar based on the outcomes of this scan entitled, Context-Based Classification in Roadway Planning and Design. To view the slides or obtain a copy of the recording, visit the webinar page on the National Academies website.

Please login to access additional content for scan members only.

Username or Email Address

Password

Remember Me