Although polycentrism is widely promoted by city planners and policymakers as a potential solution for alleviating the sprawl of central urban areas, there is no sufficient empirical evidence to verify the validity of this claim. Our study aims to complement this experience by providing solid evidence on whether polycentric urban structures can mitigate the problem of urban sprawl. In this study, the corresponding evaluation factors are selected from four perspectives: socioeconomic, spatial form and organization, and ecological environment, to measure the performance of Hangzhou’s polycentric spatial development. The results show that the performance in Hangzhou has improved significantly, and the performance improvement is more prominent over the 2010–2020 period. Third, the changing characteristics of the spatial development performance of the city centers show a significant diversity. During the study period, the development of Jiangnan city started early, but the development performance of Xiasha city improved significantly, and the development of Linping city was relatively the weakest. Fourth, socioeconomic and urban spatial organization are the main factors causing the temporal stage and spatial variability of the performance in Hangzhou. It can be seen that market-driven endogenous factors are more conducive to improving spatial development performance than government-led exogenous factors.

Given cities’ different development backgrounds, the spatial evolution of each city has a path-dependent development track. Understanding the characteristics of urban spatial structure evolution in contemporary China is essential for sustainable urban development. By establishing a theoretical framework comprising a macro-background, planning tool, and resource allocation, this paper takes Hangzhou as an example to analyze the evolutionary process of the polycentric spatial structure and reveal the formation characteristics of its polycentric urban spatial form. The results show that (1) its institutional background and planning tools are the driving forces behind the formation of the polycentric structure in Hangzhou, i.e., the evolution of the polycentric structure mainly relies on planning guidance and government forces rather than being market-driven. (2) Under the government-led mode of polycentric formation, urban elements, such as education, medical care, transportation, and green space, are still concentrated in the main urban center, while subcenters lack the necessary public facilities and are underdeveloped. (3) The spatial distribution of the population and nightlights also shows the trend of diminishing concentric circles with the main center at the core. Therefore, it is impossible to implement polycentric cities by decentralizing the population and industries alone. The comprehensive consideration of capital investment, production services, and the supply of life service facilities is also required. This empirical study can complement empirical evidence in order to verify the validity of polycentrism as a potential solution that can alleviate the sprawl of central urban areas.

Reduction planning has been implemented to mitigate urban sprawl in Chinese megacities. However, few studies have focused on the spatial implementation of urban land consolidation, and tools to estimate and simulate urban land consolidation are still lacking. To address the critical gap in urban land consolidation modeling, this study develops a bidirectional cellular automata model as a novel geospatial tool for quantifying consolidation potential and simulating future construction land dynamics under reduction planning. Our framework uniquely integrates high-resolution (30 m) simulation of simultaneous construction land expansion and reduction, overcoming limitations of conventional unidirectional models like the Future Land Use Simulation (FLUS) system, with validation confirming better accuracy. Using Beijing as a case study, the model identifies hotspots for land consolidation and, based on neighborhood-scale land transformation probabilities, delineates the spatial distribution of expansion and reduction zones, highlighting priority areas for consolidation. This provides the first operational tool for evidence-based urban reduction planning and land consolidation, offering a transferable methodology for optimizing land use efficiency and curbing disorderly expansion in megacities globally.