Analysis of the effects of urban area expansion owing to railway development in Asian megacities using optical satellite data

Abstract

For transit-oriented development (TOD) policy, understanding the relationship between urban railways and urban development is essential. In many Asian megacities, limited time-series land-use data impedes such analysis. This study introduces a rigorous method for assessing land-use changes every 30 x 30 m square area using optical satellite data, incorporating techniques to minimize errors and focus on physically developable land along railway corridors. Applying this method, a time-series analysis of Bangkok (2004–2023) across 41 zones—categorized by direction and distance—reveals that urbanization patterns vary significantly by location. Notably, developed areas along railway corridors expanded more rapidly than the metropolitan average, indicating a strong correlation between railway development and urban growth. Furthermore, the timing of development differs by section: in the purple line (Section I), urbanization accelerated post-construction, whereas in Section II, it increased following planning approval. These insights provide evidence to help policymakers optimize the timing and spatial focus of TOD initiatives.