The incident happened at 10.05pm on October 18 when a contractor truck driver, with more than five years of truck-driving experience was removing top soil ahead of the East Elk coal pit in Colorado.

MSHA advised coal mining companies to standardise and post traffic rules, signals, and warning signs and provide and maintain adequate berms and other barriers that are at least mid-axle high on the banks of roadways where a drop-off exists.

They should also train all employees on the equipment they operate, on safe job procedures, hazard recognition, and on hazard avoidance and maintain control of equipment at all times during operation. Driver should know the truck's capabilities, operating ranges, load-limits, and safety features.

“Monitor work activities and examine work areas to assure safe work practices are followed,” it said.

“Monitor contract employees adequately at all job sites to ensure that safe work procedures are being followed.

“Conduct pre-operational checks to identify and repair any defects that may affect the safe operation of equipment before it is placed into service.”