49 C.F.R. § 215.15
(a) After June 30, 1980, a railroad may not place or continue in service a freight car that has not received an initial periodic inspection in accordance with 49 CFR 215.25, as in effect on October 6, 1976 (41 FR 44044), unless—
(c) As used in this section, “high utilization car” means a car—