Resumen
Due to the development of globalization, transnational activities are more frequent and evaluations of current accessibility are the basis for accessibility improvements. Accessibility evaluation indices generally contain two parts: travel time and travel probability. However, complex transnational processes involve the multimodal transport system, including air and land transport networks, which makes the calculation of these indices more difficult because large quantities of fundamental data, in addition to suitable models, are needed. In this study, residential areas were set as the basic evaluation unit for fine-scale and whole-process analysis. Then, multiple web-sourced platforms were introduced to acquire the travel time between each pair of residential areas. The temporal-range radiation model was applied to calculate transnational travel probability by considering spatial interactions of populations. Finally, the weighted-average travel time to South Asia and Southeast Asia (SA&SEA) countries was generated to represent the overall accessibility for each populated area in China. The results showed that China had better accessibility to SEA than SA, and countries with high accessibility were Thailand, Singapore, and Malaysia. In China, southwest, south, and southeast regions showed larger accessibility to SA&SEA. Improvements of accessibility were also indicated by conjoint analysis of airport nodes. The proposed framework can help to delineate the spatial patterns of transnational accessibility and guide the enhancements of accessibility.