The UA designation, which originated in the study request, proved to be a constraint. Census data are available by UA, but transit and school bus data are not; the boundaries of transit service areas and school bus districts are not coterminous with census-defined borders of the UAs. Even so, every effort was made to include the major transit properties and school districts in a UA. The focus on UAs, however, was useful from another perspective. UAs represent the most densely populated part of a region, where transit service is likely to be most extensive, and thus where the need for transit could be significant in an emergency evacuation.

The results of the statistical profile are summarized in Table 4-1 and shown in detail in Annex 4-1.¹ The profile, particularly the detailed statistics, reveals the variety of conditions even among the largest UAs—the 38 selected for this study. For example, population ranges in size from just over 1 million for New Orleans (pre-Katrina) to 17.8 million for the New York–Newark UA.² Even more relevant from the perspective of transit service provision, population density (population per square mile)—a good proxy for the levels of transit supply to be found in an area—ranges from