213.123—Tie plates.
        
        (a) 
         In Classes 3 through 5 track where timber crossties are in use there shall  be tie plates under the running rails on at least eight of any 10 consecutive ties.
    
    
        
        (b) 
         In Classes 3 through 5 track no metal object which causes a concentrated load by solely supporting a rail shall be allowed between the base of the rail and the bearing surface of the tie plate. This paragraph (b) is applicable September 21, 1999.)