Evaluating Neighborhood Accessibility: Issues and Methods Using Geographic Information Systems

Several different trends in the 1990s have led to increased efforts to improve the alternatives to driving. In response, planning agencies have been taking a new look at both transportation and land use policies in an effort to enhance transportation choices. Their efforts have been hampered by a lack of practical planning tools. What's needed are practical measures of accessibility that can be used to evaluate the proximity to and adequacy of activities and the availability of alternative modes in neighborhoods throughout the city. The goals of the project described in this report were to identify the factors that contribute to accessibility at the neighborhood level and to explore the variety of ways that planners can evaluate neighborhood accessibility using existing data sources and the capabilities of geographic information systems (GIS). Rather than developing a single measure of accessibility, we set out to design and build a neighborhood accessibility database that would allow planners to assess a wide range of accessibility factors and identify specific kinds of deficiencies in either land use or transportation systems. Despite limitations in both data availability and GIS capabilities, several useful and insightful measures of neighborhood accessibility in terms of proximity to retail and services and the simple and practical database can be calculated. These measures, calculated for seven neighborhoods in Austin, TX enabled a comparison of accessibility between different kinds of neighborhoods that highlighted potential deficiencies and inequities. The development of a database to monitor and assess neighborhood accessibility is the first step towards developing policies that will enhance accessibility and guarantee an adequate range of choice. 17.