23 CFR § 470.105 - Urban area boundaries and highway functional classification.
(a) Urban area boundaries. Routes on the Federal-aid highway systems may be designated in both rural and urban areas. Guidance for determining the boundaries of urbanized and nonurbanized urban areas is provided in the FHWA's Functional Classification Guidelines. 1
1 The Functional Classification Guidelines can be viewed at http://www.fhwa.dot.gov/planning/fctoc.htm.
(b) Highway functional classification.
(1) The State transportation agency shall have the primary responsibility for developing and updating a statewide highway functional classification in rural and urban areas to determine functional usage of the existing roads and streets. Guidance criteria and procedures are provided in the FHWA's Functional Classification Guidelines. The State shall cooperate with responsible local officials, or appropriate Federal agency in the case of areas under Federal jurisdiction, in developing and updating the functional classification.
(2) The results of the functional classification shall be mapped and submitted to the Federal Highway Administration (FHWA) for approval and when approved shall serve as the official record for Federal-aid highways and the basis for designation of the National Highway System.
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