Conceptualizing and Measuring Accessibility within Physical and Virtual Spaces

The study of accessibility in geography and related disciplines has a distinguished history dating back to Ravenstein’s work over a century ago. In the late 1940s to the 1960s, scholars such as Zipf, Stewart, Warntz, and Wilson theorized about the way individuals and aggregates of individuals respond to the constraints of cost, time, and effort to access work, shopping, recreation, and other spatially distrib­uted opportunities. Since that time accessibility has been closely related to but also distinguished from such key geographic concepts as mobility, nearness, and the friction of distance. The models developed for its study belong for the most part in a large class of constructs known as spatial interaction models because they repre­sent the patterns and intensity of interactions among locations in geographic space. Different forms of spatial interaction models have been successfully used to study accessibility at the aggregate level, while the study of individual movements in space-time has provided insights into the significance of accessibility in people’s daily lives. One of the most robust findings of modern quantitative geography has been that interactions decline sharply with increasing distance, which is another way of saying that there is less and less contact between or among people or places as these become less and less accessible from one another.