49 CFR § 228.101
The Hours of Service Act, as amended (45 U.S.C. 6164b), makes it unlawful for any common carrier engaged in interstate or foreign commerce by railroad to begin, on or after July 8, 1976, the construction or reconstruction of sleeping quarters for employees who perform duties covered by the act within or in the immediate vicinity (as determined in accordance with rules prescribed by the Secretary of Transportation) of any area where railroad switching or humping operations are performed. 45 U.S.C. 62(a)(4). This subpart sets forth (1) a general definition of immediate vicinity ( 228.101(b)), (2) procedures under which a carrier may request a determination by the Federal Railroad Administration that a particular proposed site is not within the immediate vicinity of railroad switching or humping operations ( 228.103 and 228.105), and (3) the basic criteria utilized in evaluating proposed sites ( 228.107).