Can in situ urbanization alleviate infrastructure inequality? Evidence from the Yangtze River Delta, China

Counties along the Yangtze River Delta of China have achieved significant in situ urbanization (ISU), leading to regional infrastructure improvements. Nevertheless, inequalities persist in the infrastructure development process, receiving limited systematic attention. We comprehensively assessed 149 counties' ISU rate (ISUR) using the entropy-based TOPSIS model. A novel inequality model was introduced to measure counties’ infrastructure inequality. Spatiotemporal dynamics of ISU and infrastructure inequality were examined from 2000 to 2020, and the impact mechanisms of ISU on infrastructure inequality were explored encompassing regional differences using the two-way fixed effects model. Results indicate: (1) ISURs are initially higher in the eastern coastal region, but the west gradually catches up. (2) Infrastructure inequality shows an overall increasing trend, with specific trends varying according to terrain and grain-producing areas. (3) ISU significantly influences infrastructure inequality, exhibiting an inverted “U” relationship. When ISUR is less than 0.316, infrastructure inequality levels continue to increase with ISUR growth, while ISUR is greater than 0.316, inequality tends to alleviate. (4) Heterogeneity analysis reveals distinct different impact mechanisms across terrains and different grain-producing areas. This study provides empirical evidence on infrastructure inequality under the backdrop of similar rapid economic development regions undergoing ISU, contributing to regional coordination and spatial justice.