A portrait of accessibility change for four US metropolitan areas

Accessibility is a key objective of regional planning, one requiring the coordination of transportation and land use. Several metropolitan planning organizations in the United States and Europe have started to incorporate accessibility metrics into their evaluation of future regional scenarios. This paper describes changes in accessibility to employment by auto and transit for four contrasting metropolitan areas between 2000 and 2010. The effect of changing residential locations, changing employment locations, and changing travel speeds on accessibility change is decomposed and analyzed. Residential locations are generally shifting toward low-accessibility locations, degrading regional accessibility. Shifting employment locations have differential effects across metros, improving the accessibility of central locations in some metros while improving the accessibility of peripheral locations in others. Travel speeds also show strongly contrasting patterns across metros, with speed-related accessibility benefits concentrated in high-density locations for some metros (Chicago), while low-density locations are the primary beneficiary in other metros (Charlotte and St. Louis).