According to the agency, similar circumstances contributed to each of the accidents, and common factors identified across all four included limited visibility in lower seam heights, low equipment operator seat position, moving machinery in the direction of batteries, and stacking and storing supplies on machines. The use of opaque or non-transparent ventilation curtains was also a commonality.

MSHA is asking mine operators to evaluate the potential for similar accidents at their mines and implement preventive measures.

Some of those best practices include the utilization of clear ventilation curtains, as well as ceasing the practice of stacking or storing anything on top of a unit of mobile equipment. Additionally, when mobile operators are moving through vent curtains, the agency is urging the use of audible warning devices and the practice of stopping the machine before sounding that alarm.

The use of intrinsically safe strobe lights and reflective material on personnel can assure optimum visibility for all when mobile equipment operators meet with pedestrian miners, MSHA said.

Finally, officials recommended in the alert that mines install engineering controls, including permissible camera systems and proximity detection systems mounted on mobile equipment to improve an equipment operator’s visibility and prevent other miners from being struck.