Accessibility based on Gravity-Radiation model and Google Maps API: A case study in Australia

Accessibility is the foundation of urban planning and road network construction, and measurement indicators can be simply divided into travel cost and related potential population flow. Web mapping services provide a new mechanism to acquire the travel cost indicators directly, saving significant time for data collection and complex calculations. Meanwhile, the spatial interaction model gives the opportunity to estimate the traveling probability and population at the macro scale without actual mobility data. In this study, we introduce population grid data into the new Gravity-Radiation model for population flow estimation, and utilize Google Maps API to acquire travel costs at grid level. Then, the new estimated potential traveling population (EPTP) weighted travel costs are proposed to measure the overall accessibility at multiple scales. The results show that the EPTP is strongly correlated with the resident population at both the SUA (significant urban area, roughly equal to city) and state levels in Australia. The national EPTP weighted travel time to SUAs with maximum traveling probability is 0.26 h with an average speed of 42.53 km/h. For different SUAs or states, larger populated regions tend to have a higher-level EPTP weighted travel time with a lower-level average speed. These results can provide valuable and accurate accessibility patterns for various researches and applications, such as policymaking, urban planning, epidemic spreading, and environment protection.