Objective Geographic Information System-Based Context Classification Approach Using Nationally Available Data

Abstract

For decades the functional classification system (FCS) has guided roadway planning and design in the U.S.A. However, the FCS has a narrow focus, is auto centric, and because of its reliance on a binary classification scheme it lacks the resolution needed to develop context-sensitive designs. National Cooperative Highway Research Program (NCHRP) Report 855, An Expanded Functional Classification for Highways and Streets, introduced an expanded context classification system that supports more integrative and context-adapted roadway designs. This system was subsequently adopted in the seventh edition of the Policy of Geometric Design for Highways and Streets ( Green Book). Transitioning from the FCS to context classification entails a major shift in design practices. The context sets expectations for each setting and informs project development. Despite its advances, NCHRP Report 855 lacks guidance on quantitative measures for performing roadway classification. This paper resolves this issue by presenting an objective geographic information system (GIS)-based process transportation agencies can adopt to define contexts and weave context classification into the entire project development process. The proposed classification is based on measures that can be computed using readily available data, such as the TIGER/Line roadway data, U.S. Census urban-area data, U.S. Census population and employment data at the tract level, building polygon data, and GIS-derived intersection and street data. The application process outlined here provides the basic steps for implementing context classification at the state, regional, or project level.