IDENTIFICATION OF RURAL AMERICA
A rural area is a Census block group with its centroid outside of the area defined by the U.S. Census Bureau as an urbanized area or urban cluster. A Census block group is a cluster of Census blocks having the same first digit of their four-digit identifying numbers within a Census tract. Urbanized areas are towns, cities, or other places, or more than one contiguous place, with a population of 50,000 or more. Urbanized areas generally, but not always, are located around large cities. Urban clusters are places of 2,500 to 50,000 lying outside of urbanized areas. These adjacent communities are considered to be urban in character even though they often may be located far from a major metropolitan area and thus may be considered by some people as rural. As there is no clear indicator as to which urban clusters may be considered rural, all urban clusters are treated as urban in the analysis.
The Census Bureau updates Census block groups and urbanized areas during the decennial Census. BTS used the 2000 boundaries in conjunction with the 2006 intercity transportation facilities and the 2010 boundaries in conjunction with the 2012 intercity facilities. For 2018 and 2021, BTS used the Census Tigerline files for the year matching the population data (2018 and 2021, respectively). The vintage of the boundaries match those used in the population data.
IDENTIFICATION OF RURAL AREAS WITH INTERCITY TRANSPORTATION ACCESS
A Census block group identified as rural has access to intercity transportation if its centroid lies within a 25-mile radius around a small- or non-hub airport, bus stop, or intercity rail facility or within a 75-mile radius around a medium- or large-hub airport . BTS used these parameters in the previous reports and they are consist with the distance used in other studies .
BTS determined the size of airports from FAA's enplanement data for 2006, 2012, 2018, and 2021, respectively.
DETERMINATION OF POPULATION SERVED
Population data come from Census. BTS used Census 2000 SF 1 population data to determine the population with access in 2006, Census 2010 data to determine the population with access in 2012, American Community Survey data for 2014-2018 (the 2018 5 year estimates) to determine the population with access in 2018, and American Community Survey data for 2017-2021 (the 2021 5 year estimates) to determine the population with access in 2021. For block groups identified as rural, BTS summed the population data to county level to estimate the total rural population (see figure). In each county, an airport, intercity bus stop, and/or intercity rail facility were within the predetermined distance from the centroid of each block group identified as rural. For those within the predetermined distance, BTS summed the population data to county level to estimate the rural population with access to the transportation mode(s). BTS included facilities outside of the county itself in measuring access.
For all facilities, BTS made no adjustment to coverage areas to account for natural boundaries such as lakes, deserts, mountains, bays, etc., which may significantly increase the distance between a block group and the facility when traveling along the transportation network.
The interactive map shows the 2021 Census county boundaries. For counties that did not exist in 2006, 2012, or 2018 or experienced significant boundary changes, the map shows only the 2021 data.