THE DRIVER SLIPPED FROM THE TOP OF THE TRAILER WHILE CLOSING ONE OF THE DOME LIDS, SLIDING UNDER THE SAFETY RAIL AND CATCHING ONTO A SAFETY RAIL ON THE TRAILER. AFTER HOLDING ON FOR A TIME HE LOST HIS GRIP AND FELL ABOUT SEVEN FEET TO THE PAVEMENT AND LAY THERE FOR ABOUT ONE AND ONE-HALF HOURS UNTIL HE WAS FOUND.