49 C.F.R. § 234.3
(a) With the exception of § 234.11, this part applies to all railroads except the following:
(3) Tourist, scenic, historic, or excursion operations conducted only on track used exclusively for that purpose (i.e., there is no freight, intercity passenger, or commuter passenger railroad operation on the track) and only on track inside an installation that is insular; i.e., the operations are limited to a separate enclave in such a way that there is no reasonable expectation that the safety of the public—except a business guest, a licensee of the railroad or an affiliated entity, or a trespasser—would be affected by the operation. An operation will not be considered insular if one or more of the following exists on its line:
[77 FR 35190, June 12, 2012]