Unraveling post-socialist urban expansion: Long-term built-up dynamics in Polish and Romanian urban regions

Post-socialist urbanisation in Central and Eastern Europe is often described through common processes of decentralisation, land-market formation and suburban expansion, yet the spatial outcomes of transition have diverged substantially across countries. This study examines how contrasting land-ownership reforms and planning instruments shaped long-term built-up dynamics in six second-tier Polish and Romanian urban regions. Using fine-grained Global Human Settlement Layer data from 1975 to 2020, the study applies time-series clustering to identify recurrent trajectories of built-up expansion and compares their spatial distribution, built-up intensity and population-adjusted land consumption. The results show that both countries experienced dispersed peri-urban growth, but in different forms. Romanian urban regions display faster, more fragmented and more land-intensive post-2000 expansion, especially in the newest and lowest-density classes. Polish urban regions also show dispersed development and weak coordination, but their observed spatial signatures are relatively less atomised and more frequently associated with existing settlement structures. These differences are interpreted as the cumulative outcome of ownership reform, parcel structure and development-right allocation within a broader post-2000 context of housing demand, credit expansion, mobility and infrastructure constraints. The paper contributes to comparative post-socialist urban studies by showing that shared socialist legacies did not produce a single urban-regional trajectory and by linking institutional divergence to micro-spatial, multi-decadal evidence beyond capital-city cases.