Description: FHWA and the Census Bureau differ in defining and describing urban and rural areas. The Census Bureau defines urban areas solely for the purpose of tabulating and presenting Census Bureau statistical data. A number of Federal agency programs use the Census definitions as the starting point (if not the basis) for implementing and determining eligibility for a variety of funding programs.Federal transportation legislation allows for the outward adjustment of Census Bureau defined urban boundaries (of population 5,000 and above) as the basis for development of adjusted urban area boundaries for transportation planning purposes. By Federal rule, these adjusted urban area boundaries must encompass the entire Census-designated urban area (of population 5,000 and above) and are subject to approval by the Secretary of Transportation (23 USC 101(a) (36)-(37) and 49 USC 5302(a) (16)-(17)).10 According to 23 U.S.C. 101(a)(33), areas of population greater than 5,000 can qualify as urban, in contrast to the Census Bureau’s threshold of 2,500. There are also differences in the terminology used to describe sub-categories of urban areas. FHWA refers to the smallest urban area as a “small urban area”, while the Census Bureau refers to “urban clusters”. The Federal government does not require Census urban boundary adjustments. States may adopt the Census boundaries as is, or adjust them for transportation planning purposes. The only official requirement is adjusted boundaries must include the original urban area boundary defined by the Census Bureau in its entirety. In other words, any adjustment must expand, not contract, the Census Bureau urban area boundary. The adjusted urbanized area boundaries can also include other areas that are “urban” in character but do not meet the Census Bureau’s population threshold (e.g., high density industrial or commercial areas, urban parks, etc.). The adjusted boundaries can also be expanded to ensure major roads do not alternate between urban and rural designations. This geography, called the “adjusted urbanized area” boundary, includes locations with a population of 50,000 or greater.