49 CFR § 214.521
Flagging equipment for on-track roadway maintenance machines and hi-rail vehicles
November 18, 2020
Each on-track roadway maintenance machine and hi-rail vehicle shall have on board a flagging kit that complies with the operating rules of the railroad if:
(a) The equipment is operated over trackage subject to a railroad operating rule requiring flagging; and
(b)
(1) The equipment is not part of a roadway work group; or
(2) The equipment is the lead or trailing piece of equipment in a roadway work group operating under the same occupancy authority.
[69 FR 8839, Feb. 26, 2004]