Zooming in and out of compact city agenda: A multi-scale investigation of compact urban centers

Compact city policy in rapidly developed metropolitan areas increasingly seeks balanced urban development through compact multi-centred planning. Cities such as Seoul have pursued a more even distribution of liveability opportunities by expanding public transport networks and promoting multiple socio-economic hubs around key transit nodes. Yet, tools for critically evaluating whether these strategies align macro-scale connectivity with micro-scale everyday service accessibility remain limited. Drawing on the concept of isobenefit cities, this study develops and applies Multi-Scale Investigation (MSI) as a spatial diagnostic framework for evaluating the social outcomes of compact multi-centred planning. MSI “zooms in and out” of strategic urban centres by jointly assessing two non-substitutable dimensions: city-wide public transport connectivity and local service accessibility. The framework is applied to three selected policy-designated centres in Seoul, an exemplar of rapid urban growth followed by compact polycentric policy and major transit investment. The analysis reveals differentiated macro–micro configurations across the selected cases. All three centres occupy relatively prominent positions within the wider subway network while local service accessibility often fell below policy expectations. The selected Central Business District node exhibited the clearest scalar imbalance, combining the highest city-wide connectivity with the lowest local accessibility. The selected Quarter Centre node showed a connectivity-constrained configuration, suggesting its limited consolidation as a local hub. In contrast, the selected District Centre node displayed a more coherent macro–micro alignment, achieving the strongest overall MSI profile among the three cases. These findings show how MSI can reveal scalar tensions within policy-designated centres and generate case- specific planning feedback. Rather than offering a universal index, MSI provides a calibrated diagnostic logic for identifying where compact polycentric strategies require centre-specific adjustment to better align with isobenefit conditions. The MSI procedure—centre-hierarchy identification, node selection, and scalar tension diagnosis—can be recalibrated and applied in other transit-intensive metropolitan contexts with comparable planning conditions.