Spatiotemporal patterns and drivers of population and transport coordination in the Pearl River Delta

The demographic-transport nexus is central to regional integration, but remains insufficiently studied in rapidly urbanizing contexts. Taking China's Pearl River Delta (PRD) as a representative megaregion, this study uses panel data from nine PRD cities spanning 1990 to 2020. We construct an entropy-weighted indicator system and apply a coupling-coordination model in combination with a panal data regression to trace the co-evolution of population and transport systems and identify their driving forces. Findings reveal that: (1) the regional coupling-coordination index rose from 0.21 to 0.54 but still shows a clear core-periphery gradient-Guangzhou and Shenzhen already display high coordination, whereas ZhaoQing and Jiangmen lag behind; (2) economic growth, a consumption-oriented economic structure and technological progress significantly enhance coordination; (3) the 2009 PRD Master Plan mainly benefits core cities, with limited policy spill-overs; (4) medical-service provision improves coordination, while basic-education supply is not significant, highlighting service-level disparities. We recommend strengthening peripheral inter-city corridors, building 30- to 60-minute commuting rings, and linking transport investment to real-time coupling metrics and coordinated industry relocation to advance the region toward higher-level integration.