Quantifying urban sprawl and investigating the cause-effect links among urban sprawl factors, commuting modes, and time: A case study of South Korean cities

This study aims to create a detailed urban sprawl index, investigate the relationship between density and other urban sprawl factors, and analyze how these factors affect commuting mode time in South Korean cities using structural equation modeling and multiple linear regression. Urban sprawl factors are categorized from various individual perspectives into density, urban landscape, land-use mix, centeredness, and street connectivity. We show that while scores for urban landscape, density, and centeredness were high in cities with large populations, scores for land-use mix and street connectivity were high in cities with medium and small populations. We found that density had significant effects on urban landscape, centeredness, and street connectivity. The indirect effects of density on commuting modes and time counterbalance the direct effects, indicating that while the indirect effects do not change the direction of the direct effects, they reduce their magnitude, making the total effect smaller than the direct effect. A higher density was associated with fewer commuters using cars and higher numbers of public transit, but the reduction in cars was limited to less than 30 min of commuting time. In addition, high density was positively associated with commuting time. High scores for urban landscape, land-use mix, and street connectivity were associated with a reduction in commuting time but did not have an effect on the conversion from cars to public transit for the journey to work. High scores for urban landscape and street connectivity were associated with more walking commuters but were limited to commuting for less than 60 min. This study shows that urban sprawl factors are mutually complementary for commuting mode changes and time. This study provides evidence for establishing sustainable transportation plans. In addition, the urban sprawl index can be used in future research to investigate the effects of urban sprawl on various social and environmental phenomena.