Unguarded conveyors next to the 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; or

(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.