THE EMPLOYEE WAS BRINGING LOAD OF BLOCK INSIDE ON A FLAT-CAR WHEN THE FLAT-CAR GOT AWAY FROM CO-WORKER HAD STOPPED ON MOTOR & WOULD NOT STOP SO HE JUMPED OFF OF FLAT-CAR CAUSING CONCUSSION & C ONTUSIONS. THIS HAPPENED AT THE END OF TRACK. THIS WAS REPORTED TO SAFETY DEPT ON 5-22-03.