Spatial organization and accessibility: a study of US counties

Commuting is a phenomenon that widely affects contemporary societies confronted with the opportunity to work in places that are sometimes located at a considerable distance from residential districts. The areas in which we live are organized to allow for the daily movement of workers and students, calling for efficient transportation systems in order to minimize costs. In regional science, accessibility is often used to evaluate, among other characteristics, the effectiveness and quality of transportation systems. This multifaceted concept encapsulates the ability of a certain category of people to reach a given location and clearly depends on the logistics of transportation infrastructures. In literature accessibility is assessed by means of several indicators, whose functional structure is generally related to two factors: job opportunities and the transport costs that people sustain to reach a location. Whatever accessibility measure is applied, the level of accessibility often depends on spatial location. In this chapter we apply spatial autocorrelation analyses to investigate the spatial distribution of commuters’ accessibility across US counties. Commuting is a mushrooming phenomenon in the US: approximately 25 per cent of the total US labour force (about 32 million people) commute from a distance radius of 25 minutes, according to the dataset on commuting behaviour provided by the US Census Bureau (www.census.gov). This information refers to commuting trips in the counties of the 50 states and the District of Columbia (DC). We consider inbound and outbound movements to and from each of the 3141 counties on the US mainland