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The density is calculated in a county level base, which produces a homogeneous density through the entire county while the real densities are higher at some zones and lower at other ones. A better approach is to estimate densities with a smaller spatial unit, like census tracks, which leads to improved estimates.
Two important data sources can be added to the analysis: construction type of the possible relief sites and streets. The former one would help in the selection of sites with more resistant construction materials (e.g. concrete) and the later one would help in the identification of possible evacuation routes to the selected relief sites.