Case Study:

San Francisco Bay Area, California

Methodology

Definition of Disadvantaged Groups

The MTC measured equity in terms of accessibility changes to "disadvantaged" relative to "not disadvantaged" neighborhoods. Definitions of disadvantaged neighborhoods are from a 1997 report by the San Francisco-based NCCC. Using 1990 Census data, the NCCC identified 38 "disadvantaged" neighborhoods, comprised of 142 census tracts, based on median household income, public assistance income, and median gross rent as a percentage of household income. The NCCC methodology flags local neighborhoods that are 80 percent or less of each county's median household income. MTC then identified the 133 regional travel analysis zones (out of 1,099 total zones) that correspond to these 142 census tracts.

Population forecasts for 2020 prepared by the Association of Bay Area Governments (1998) indicate that 959,000 persons will reside in the 133 neighborhoods identified as disadvantaged. This compares to the 6.8 million persons expected to reside in the rest of the Bay Area in 2020 (the total population of the Bay Area is projected to be nearly 7.8 million persons.) The locations of the disadvantaged TAZs are shown in Figure 2.

Accessibility could also be compared based on other definitions of socioeconomic groups at the census tract level. Tracts containing relatively high levels of low-income or minority populations could be identified, for example, based on some locally agreed-upon threshold. Socioeconomic characteristics and mobility limitations could also be used in combination to develop a locally preferred measure of "disadvantaged" populations. Regardless of the methodology used, dividing tracts and corresponding TAZs into a "disadvantaged" group and a "not disadvantaged" group allows the difference in accessibility between these two groups to be compared. Differences among multiple groups (e.g., three or more average income categories) could also be defined and measured with appropriate statistical tests.

Figure 2. TAZs Corresponding to "Disadvantaged" Neighborhoods

Source: Adapted from Metropolitan Transportation Commission data.

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