Measuring Accessibility: A Review and Proposal

An attempt is made to clarify some of the confusion about the notion of accessibility by examining the limitations, strengths, and conceptual bases of distance, topological, gravity, and cumulative-opportunity measures of accessibility. In their aggregate and disaggregate states the measures are practical, enabling measurement into the future and measurement with a minimum of data, but the assumptions that all nodes are potential destinations and that all origins are known severely restrict the meaning and uses of the measures. Time—space measures of accessibility do not make these assumptions although they are data hungry, retrospective, and share with the other measures the narrow conception of accessibility as a property of the built environment. It is proposed that accessibility be thought of as a vacancy in an activity routine and that it be measured in terms of the disruption involved in creating it.