Incorporating diminishing returns to opportunities in access: Development of an open-source walkability index based on multi-activity accessibility

In this paper, we argue for an explicit decoupling of “walkability” and “walking behavior” and for the advantages of a definition of walkability based on access. This provides impetus for a new approach to constructing and using walkability indices, combining accessibility theory with a goal of comprehensiveness and communicability. Diminishing returns-to-opportunities can be used to map the infinite origin-destination gravity potential space to a finite scale thus creating an easily communicable metric, or metrics. In addition, this method can be applied to any mode and applied to multiple destination types singly or combined. Application of this theoretical approach is demonstrated through the creation of a novel comprehensive open-source transport walking potential index, WalkTHERE. A 0-100 scale is used to represent the percentage of people’s total needs potentially accessible by walking. The index is applied to eight Australian and two European cities, and the specific data considerations and parameters chosen are described. Significant disparity is shown in walking access between different destinations within cities, and in walking access between cities. Walking access to recreational opportunities is highest, followed by education and shopping, with very little employment access for most residents. Avenues for expansion and further validation are discussed.