Anti-sprawl policies in a system of congested cities

摘要

Armed with recurring analyses since the mid 1960s, economists believe that the under-pricing of traffic congestion in urban areas causes not only excessive travel but also excessively low land use densities and excessively spread out cities, a condition popularly known as urban sprawl. This conclusion is derived from analyses of a single monocentric city. We extend the analysis to a system of two asymmetric monocentric cities closed in aggregate population, differing by their amenity. In this setup, we analyze the effect of optimally tolling traffic congestion, or of optimally determined urban growth boundaries (UGBs), a constrained optimum regime that can also be implemented by taxes and subsidies on land. We prove that either policy regime may expand aggregate urban land use relative to laissez-faire. This is certainly true when the elasticity of substitution between lot size and other goods is sufficiently small and/or the cities are sufficiently asymmetric in their amenities. In both cases, the inter-city expansive effect of tolling, or of the UGB regime on aggregate urban land use outweighs the contractive intra-city effect (which is the only effect considered in earlier studies). Only when the elasticity of substitution is sufficiently large and/or the cities are sufficiently symmetric, the intra-city contractive effects of tolling or of the UGBs on aggregate land use, dominate the inter-city expansive effect, validating the earlier belief. These, properties are illustrated in simulations which supplement our proofs.