Does polycentric and compact development alleviate urban traffic congestion? A case study of 98 Chinese cities

Abstract

Despite a growing interest among policymakers and urban planners in promoting polycentric and compact development to mitigate traffic congestion, empirical studies have often documented mixed and indirect evidence on the impacts of polycentricity and compactness on congestion. Drawing upon a direct and big-data-based measure of congestion and gridded (1 km × 1 km) population data of 98 Chinese cities, this study investigates how polycentricity and compactness may affect congestion in these cities. The degrees of polycentricity and compactness are measured through fine-grained identification of population centers. All else being equal, the empirical results show that congestion is positively associated with the degree of compactness but negatively associated with that of polycentricity. However, increasing the degree of polycentricity by developing more than four population centers may also lead to more congestion. Furthermore, the negative impact of polycentricity on congestion becomes weaker with the increase in a city's population and even turns positive for large cities with more than six million inhabitants within urban districts. The paper concludes with spatial planning implications.