Estimating the steps made by public transport commuters using a synthetic population enriched with smart card data

Background: Public transport use can contribute to daily physical activity recommendations through its associated walking components. However, without using travel surveys, it is chal-lenging to estimate walking associated with public transport use for the population of large cities.Methods: Big data, in the form of smart card data, combined with a synthetic population, was used to estimate the access, transfer and egress distance of public transport commuter journeys in Sydney, Australia. A spatial network analysis of the access, transfer and egress segments of commuter journeys was performed using Geographic Information Systems (GIS).Results: A mean step count of approximately 2400 steps (1915 m) weighted across modes was estimated for daily public transport commutes. The largest mean number of steps corresponds with ferry (3066 steps, 2436 m) and train use (2933 steps, 2340 m).Conclusion: Walking to public transport is an important contributor to meeting physical activity recommendations. The findings of this study can aid planners and health practitioners to un-derstand the pattern of physical activity associated with public transport commuter use and can influence future decision-making in land use planning and infrastructure provision, or for developing targeted interventions for the promotion of the benefits of physical activity and public transport use.