Co-evolution of public transport access and ridership

While transport infrastructure and travel demand are known to be correlated, their causal relationship has not been systematically investigated. Granger causality tests have been conducted in the context of transport infrastructure and economic growth, and land use and transport. This research extends their application to network investments and travel demand by examining the co-evolution of public transport access and ridership in the Greater Sydney region for a period spanning over a century, from 1855 onward. We hypothesise a mutual feedback between public transport ridership and access, and corroborate the hypothesis in all causal models estimated – between aggregate public transport ridership and access, station ridership and access, and mesh block public transport shares and access. The causality was more evident in disaggregate models and was stronger between ridership and access to jobs than with access to population when employment data were available. Ours is the first longitudinal investigation into the causal relationship between public transport access and ridership. The findings strengthen the case for using access as a planning measure and lay the groundwork for evolutionary strategic transport modelling.