30 CFR § 57.9200
TRANSPORTATION OF PERSONS AND MATERIALS
Persons shall not be transported--
(a) In or on dippers, forks, clamshells, or buckets except shaft
buckets during shaft-sinking operations or during inspection, maintenance and
repair of shafts.
(b) In beds of mobile equipment or railcars, unless--
(1) Provisions are made for secure travel, and
(2) Means are taken to prevent accidental unloading if the
equipment is provided with unloading devices;
(c) On top of loads in mobile equipment;
(d) Outside cabs, equipment operators' stations, and beds of mobile
equipment, except when necessary for maintenance, testing, or training
purposes, and provisions are made for secure travel. This provision does not
apply to rail equipment.
(e) Between cars of trains, on the leading end of trains, on the
leading end of a single railcar, or in other locations on trains that expose
persons to hazards from train movement.
(1) This paragraph does not apply to car droppers if they
are secured with safety belts and lines which prevent them from falling off
the work platform.
(2) Brakemen and trainmen are prohibited from riding
between cars of moving trains but may ride on the leading end of trains or
other locations when necessary to perform their duties;
(f) To and from work areas in overcrowded mobile equipment;
(g) In mobile equipment with materials or equipment unless the items
are secured or are small and can be carried safely by hand without creating a
hazard to persons; or
(h) On conveyors unless the conveyors are designed to provide for
their safe transportation.