TRUCK DRIVER WAS PROCEDING OUT OF PIT WITH A LOAD OF COAL WHEN HE LOST POWER, ROLLLED BACKWARDS ABOUT 30 FT AND STRUCK THE SIDE OF THE HAUL ROAD. HE THEN PROCEEDED TO TIP OVER ON THE PASSENGER SIDE OF TRUCK. WHEN HE UNBUCKLED HIS SEAT BELT HE FELL TOWARDS THE PASSENGER SIDE OF TRUCK. AS HE FELT HE HIT HIS HEAD ON A CLOTHES HOOK AND SHOULDER STRUCK THE DOOR.