Case Study:

San Francisco Bay Area, California

Methodology

Accessibility Measures

In its accessibility analysis, MTC computed two types of measures, each describing the accessibility of households to employment:

1. A "threshold-based" measure, which is the number of jobs reachable within an X-minute travel time of a given zone. MTC selected a variety of thresholds, including 30, 45, 60, and 75 minutes, for comparison.
   
2. A "gravity-based" measure, in which the number of jobs in each zone is weighted in inverse proportion to travel time from the zone of residence (e.g., importance diminishes as distance increases).

To compute the overall regional accessibility for a given mode, the total number of jobs reachable from each zone is weighted by the population of that zone. The accessibility measures were computed on the basis of 2020 travel times forecast by the MTC's regional travel demand model and 2020 population and employment forecasts by the Association of Bay Area Governments (ABAG).

The Montgomery County case study provides another example of the use of threshold-based measures, while the Tren Urbano case study provides another example of the use of gravity-based measures.

[TOP]