Grocery store accessibility: Different metrics – Different modal disparity results and spatial patterns

Most accessibility studies focus on within transport mode travel performance variations. However, modal
accessibility disparity analysis adds value to the single-mode analysis by assessing the interaction between
different transport modes and land use. A review of modal disparity studies shows that different accessibility
metrics lead to different results, and so it is unclear how this impacts modal accessibility disparity variation.
Moreover, the correspondence of the disparity spatial pattern between the different metrics is unclear. This
research examines how three typical accessibility metrics (closest facility, cumulative opportunity, space-time
constrained) impact modal disparity of grocery store accessibility in Warsaw, Poland. Further, local indicators
of spatial association are used to identify areas of similarity and difference between the metrics. This study finds
that cumulative opportunities during non-rush hours indicate the best car advantage for all travel times but
indicate the best transit advantage during rush hours for 15 min. Generally, the space-time metric indicates
better transit accessibility than the closest facility metric which in turn shows better transit accessibility than
cumulative opportunities. The city center has significant spatial similarity while peripheral, especially dense,
areas have significant spatial difference. Similarity areas have higher transit stop and population densities, while
difference areas have average-to-low stop, population, road and store densities.