Two-step floating catchment area method

The two-step floating catchment area (2SFCA) method is a special case of gravity model of spatial interaction that was developed to measure spatial accessibility to primary care physicians (Luo and Wang 2003a, b). 2SFCA can also be used to measure other accessibility such as accessibility to jobs, to cancer care ficilities, etc. It was inspired by the spatial decomposition idea first proposed by Radke and Mu (2000). 2FSCA not only has most of the advantages of a gravity model, but is easy to implement in a GIS environment (Luo and Wang, 2003; Wang and Luo, 2005; Wang, 2006: 80-95). In essence, the 2SFCA method measures spatial accessibility as a ratio of primary-care physicians to population: it first assesses “physician availability” at the physicians (supply) location as the ratio of physicians to their surrounding population (i.e., within a threshold travel time from the physicians), and then sums up the ratios (i.e., physician availability derived in the first step) around (i.e., within the same threshold travel time from) each residential (demand) location.also intuitive to interpret, as it uses essentially a special form of physician-topopulation ratio.