49 CFR 220.311: Railroad operating employees in deadhead status.

(a) Notwithstanding any other restrictions in this subpart, a railroad operating employee who is in deadhead status and not inside the cab of a controlling locomotive may use an electronic device only if the employee is not using the device in such a way that interferes with any railroad operating employee's personal safety or performance of safety-related duties.

(b) A railroad operating employee who is in deadhead status and located inside the cab of a controlling locomotive must have each electronic device turned off with any earpiece removed from the ear—

(1) When on a moving train;

(2) When any member of the crew is—

(i) On the ground, or

(ii) Riding rolling equipment during a switching operation; or

(3) When any railroad employee is assisting in preparation of the train for movement.