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Table 1 McGrail and Humphrey’s rules to define the variable application of distance-decay to service catchments (Step 1)

From: Spatial accessibility of primary health care utilising the two step floating catchment area method: an assessment of recent improvements

Rule Explanation Outcome
1. Population within 10 minutes of the service Initial (local neighbourhood) catchment without distance decay No decay
2. Population linked to their nearest 25 services Services likely to provide access to populations (beyond 10 minutes) that have few alternative options No decay
3. Population <5000 and < 0.5 population of the Service town Services in larger towns likely to provide access to significantly smaller nearby populations, but not vice-versa No decay
4. All other scenarios Services less likely to provide access to populations as distance increases. Decay