30 CFR § 57.14109
Unguarded conveyors with adjacent travelways.
Unguarded conveyors next to travelways shall be equipped with
(a) Emergency stop devices which are located so that a person falling
on or against the conveyor can readily deactivate the conveyor drive motor;
(b) Railings which
(1) Are positioned to prevent persons from falling on or
against the conveyor;
(2) Will be able to withstand the vibration, shock, and
wear to which they will be subjected during normal operation; and
(3) Are constructed and maintained so that they will not
create a hazard.
For more information: See MSHA'S Program Policy Manual