Metropolitan form, transportation, and labor accessibility: Empirical evidence from four US metropolitan areas

Urban planners and economists have long debated the optimal size and spatial structure of metropolitan areas, including the question of whether low density development or sprawl is desirable or not. One aspect generally overlooked in the debate is whether sprawl enhances or reduces agglomeration economies. This thesis explores the extent to which jobs in metropolitan areas are concentrated in employment centers and whether those centers are accessible to large numbers of workers; both factors thought to contribute to agglomeration economies. These issues are explored by examining four metropolitan areas with similar populations but different spatial structures: Atlanta, Boston, Phoenix and Washington, DC. Boston and Washington DC are relatively dense while Atlanta and Phoenix are not.;Approximately 30 percent of the metropolitan employment is concentrated in centers either in the Central Business District (CBD) or the suburbs, but the size and location of these centers vary considerably. The employment centers are identified using the approach pioneered by Giuliano and her colleagues but with additional tests to confirm that the differences in the size of the analysis zones do not contaminate the result. While Boston's employment centers are dominated by its CBD, Atlanta and Washington DC are more polycentric having an important CBD and some strong and large suburban business districts (SBDs). Phoenix exhibits more dispersed pattern with a smaller CBD and smaller SBDs.;The labor accessibility to the employment centers also varies considerably and in unexpected ways. The CBDs are not the most accessible centers in their metropolitan areas. Moreover, the centers in Boston and Phoenix are much more accessible than the centers in Atlanta and Washington, DC. Although Atlanta and Washington DC enjoy the polycentric form many planners favor, their centers are relatively less accessible because they suffer both from a modest residential density and fairly low speeds. A statistical analysis suggests that increasing residential density would not increase the size of the accessible labor force proportionally because higher density makes it harder to maintain high commuting speeds. Public transit appears to have far less effect on labor market accessibility than highways, although its contribution is difficult to measure.