Walking accessibility to public transport: an analysis based on microdata and GIS

In this paper we analyse the role of walking accessibility to transit facilities. Microdata and GIS tools have been used to calculate distances walked by different population groups in accessing Metro stations. Distances walked by the population were used to determine the threshold distances of the station service areas and calculate the population covered by the Metro network. With respect to Metro ridership, different distance-decay functions were adjusted and the sensitivity of the population groups to the distance was measured. Two indicators were proposed, based on the distance-decay functions, to measure access quality and potential demand. The Madrid Metro network was used as the study area. Results show that young people and adults, men, immigrants, and public transit captives are willing to walk longer distances and are less sensitive to the effect of distance. When walking distances have been used in order to fix the limit of catchment areas, the amount of the population covered is lower than when a standard threshold (0.5 miles) is used, but overestimations affect each age group in a different way. The access quality indicator shows that the population group in the worst situation is children and that stations in the centre of the network have higher access quality values. However, the synthetic accessibility indicator shows that potential demand is lower for the most central and most peripheral stations than for the stations located in the intermediate areas. It has been proved that both indicators are sensitive to changes in the spatial distribution of population groups within the catchment areas. These results demonstrate some of the advantages of the proposed methodology and argue in favour of its use in public transport planning.