Evaluating the Usability of the TOPODATA DEM to Measure Cyclist Accessibility: A Case Study of a Small Town

Abstract

Devising urban mobility plans for Brazilian cities, especially small ones, lacks technical support, such as altimetric surveys that allow the representation of the terrain accurately, causing many transportation planners to benefit from Digital Elevation Models (DEMs). This study aims to evaluate the usability of TOPODATA DEM to measure the accessibility of cyclists to their potential travel destinations. A case study was conducted in the city of Bariri-SP (Brazil), where altimetric data collected using GNSS technology was previously available. Expected speeds for cyclists were assigned to the road segments as a function of their respective TOPODATA and GNSS slopes, allowing the identification and comparison of the shortest homologous paths between the units of analysis and bicycle Trip Attractors (TAs). The homologous accessibilities in each unit of analysis were also compared with each other, and the differences between them were evaluated according to their spatial autocorrelation, in addition to their spatial dependence on TOPODATA altitudes and slopes. The impact on the overall accessibility of different population groups in the city when using the DEM was also observed. The results suggest the shortest homologous paths that are quite similar to each other, although the accessibility samples for both sources of altimetric information differ statistically. A strong spatial autocorrelation was observed between differences in homologous accessibilities, but moderate to weak spatial dependences were observed between this variable and TOPODATA altitudes or slopes. The overall accessibility of each evaluated population group is similar regardless of the criterion used.