Comparison between Idealized and Realized Measures of Accessibility in GIS

Keywords: GIS, spatial analysis, accessibility, active transportation, bicycle
Abstract Type: Paper Abstract

Abstract

Measures of access, defined as the ease with which people can reach opportunities or services, are often based on proximity. Proximity measures of access are often unrealistic or idealized, ignoring many of the real barriers to access including social and economic barriers. There is a need to develop GIS measures of access that incorporate all aspects of access, which we term realized access. Our goal is to develop a conceptual framework of realized accessibility in active transportation, and compare idealized and realized measures of access to bicycling. We apply the framework to measure realized accessibility in a case study focusing on bicycling access in Santa Barbara County, and compare idealized and realized measures of access for four cities (Santa Maria, Lompoc, Santa Barbara, and Goleta). Changes in accessibility from idealized measures to realized measures are greatly increased in cities with lower median household income and a higher proportion of people identifying as Hispanic. Studies that aim to understand equity and access will benefit from more nuanced and realized measures of access, as idealized measures may overestimate access in underserved communities. In GIScience, especially as new data on mobility become more widely available, nuanced measures of accessibility should be the standards in analysis.