Suburban new towns are currently facing distinct challenges in the context of a transition away from rapid growth, coupled with processes of re-urbanization. Few studies have examined the transformation of new towns, particularly in relation to compact-development policies and in non-Western settings. The main contribution of this study is the construction of composite spatial indexes that quantify both compactness and shrinkage and enable the characterization of multi-faceted transformation of urban space in new towns. Using new towns in megacities of China and Japan as empirical cases, the framework allows identification of diverse spatial restructuring associated with city-region dynamics and processes of decentralization and recentralization. We identify four distinct types of spatial transformations closely related to demographic changes, urban land expansion, and the elasticity of expansion within the city-region. Chinese new towns are exhibiting a trend towards moderate intensification characterized by slowing compactness alongside expansive growth, whereas Japanese towns are predominantly dispersing and, in some cases, shifting from dispersion to hollowing. A process of de-compaction occurring prior to the onset of shrinkage is suggested. Notably, the shrinking of new towns is linked to their maturity and the centralization of the city-region, whereas compacting does not exhibit this relationship. By providing a metric system for measuring transformations of urban spaces in new towns, this study contributes both a methodological advance for urban spatial analysis and actionable insights for policy and planning interventions in post-growth suburban contexts.
