Walkability: Which Measure to Choose, Where to Measure It, and How?

Abstract

The urban structure of neighborhoods has a decisive impact on active mobility, but this impact is hard to evaluate in a mode choice model because of the high collinearity between urban form variables and the uncertainty surrounding adequate spatial measurement parameters. Several composite scores, or walkability measures, have emerged from the literature, each using its own method and including different variables. No consensus has been reached on the size of the catchment area that should be used to measure walkability and most studies only measure walkability at the origin of the trip without considering other spatial units. In this paper, a series of four walkability measures: the Pedestrian Index of the Environment (PIE), the Walkability Index (WI), the Pedestrian Potential Index (PPI) and the Neighborhood Destination Accessibility Index (NDAI), are applied to the Greater Montréal Area to examine their correlation with the choice of walking for short trips. Several definitions of a neighborhood are tested for each measure, as well as several spatial units of measurement. A series of binary logistic regressions are then estimated using observed trip data from the 2013 Montreal Origin–Destination Survey to identify which measure, using which spatial parameters, offers the best performance in a mode choice modeling context. Measures using a diversity of urban form variables, the WI and the PIE, are found to offer the best performance, especially when measured at a scale smaller than a 1.6 km radius, while the spatial unit offering the best model fit varies between trip purposes.