The use of space-time constraints for the selection of discretionary activity locations

Abstract

The development of methods of studying individuals' selection of discretionary activity locations remains a challenge for empirical analysts and transport modelers. Time geography and, in particular, the concept of space-time constraints provides a useful framework for these selction processes. In this work we empirically determine space-time constraints from the Chilean household and travvel survey. Based on a specific activity pattern example, where trips are made from home to work to a discretionary activity and back home, we estimate detour factor. Detour factors describe the spatial deviations that are made from the home-work axis to conduct the discretionary activity. Using GIS we estimate potential path areas (PPAs), where discretionary activities may be located. Within the PPAs, applying a time constraint that is the maximum daily travel time refines the selection of discretionary activity locations. The thresholds of the daily travel time vary according to the PPA-size and mode combinations. We were able to reproduce between 38% and 72% of the discretionary location choices observed in the survey (according to the rigor of the constraints applied).