TWO EMPLOYEES WERE ENGAGED IN DROPPING AN EMPTY HOPPER DOWN TRACK 5. AS TACKMOBILE APPROACHED, THE BULK LOADER REMOVED THE RAIL AND RELEASED THE BRAKES ON THE RAIL CAR. THE RAIL CAR COLLIDED W ITH THE TRACKMOBILE SOME 35 PACES DOWNGRADE FROMITS ORIGINAL POSITION. AT IMPACT THE OPERATOR'S LEFT LEG STRUCK THE TRACKMOBILE STEERING COLUMN.