Rethinking Compact City Strategies in Shrinking Cities: Evidence from Commuting Patterns in South Korea

Compact city policies have been promoted as a mechanism for improving commuting efficiency through higher density and spatial concentration. However, their effectiveness in small and medium-sized cities that experience population decline, such as in small and medium-sized cities in South Korea remains unclear. This study examines how urban compactness and employment spatial structure influence commuting time across different urban contexts in South Korea, with particular attention to contrasts between the Seoul Capital Region and non-capital cities. Using the 2021 Korean Individual Travel Survey, we examine multilevel mixed-effects models that link individual commuting trips to neighborhood-level built environment characteristics and city-level employment spatial structure. The findings reveal systematically different effects of residential and employment density on commuting times. Higher residential density is generally associated with longer commuting times, whereas higher workplace employment density reduces commuting time only in non-capital regions. In the Seoul Capital Region where urban form is already highly compact, further employment densification does not improve commuting efficiency and may even increase commuting time. Instead, shorter commutes are observed primarily where job–housing balance is relatively high and employment is strongly concentrated in a dominant center. Moreover, the contrasting effects of employment Moran’s I and the employment concentration index indicate that employment dominance and spatial clustering capture distinct dimensions of urban spatial structure, with commuting efficiency depending critically on the internal configuration of employment clusters rather than density alone. These findings suggest that, in shrinking cities, compact city policies should be reframed not as strategies of residential densification, but as strategies of functional consolidation, focusing on sustaining viable employment cores and aligning them with transport networks and residential areas.