THE COAL DISCHARGE HAD BECOME STOPPED UP WITH LOOSE MATERIAL. THE MACHINE'S WHISPER SWITCH HAD BEEN DEPRESSED BY THE MATERIAL DEACTIVATING THE CONTROLS. AFTER CLEARING MATERIAL, HE STEPPED ONTO THE GUIDE RAIL FOR MACHINE'S DOLLY. WITH THE WHISPER SWITCH IN NEUTRAL, THE OPERATOR TRIED TO RESTART MACHINE. WHEN IT MOVED, IT CAUGHT HIS FEET BETWEEN RAIL WIPER BAR AND DOLLY RAIL.