30 C.F.R. § 56.9319
Going over, under, or between railcars
Persons shall not go over, under, or between railcars unless:
(a) The train is stopped; and
(b) The train operator, when present, is notified and the notice acknowledged.
Persons shall not go over, under, or between railcars unless:
(a) The train is stopped; and
(b) The train operator, when present, is notified and the notice acknowledged.