(a) No advertising matter or sign whatever shall be displayed upon any bench except upon the front and rear surfaces of the backrest, and not more than 75% of each such surface shall be so used. No pictures or representations in irregular contour shall appear on any such bench. All advertising shall be subject to the approval of the Board.
(b) No advertisement or sign on any bench shall display the words “STOP,” “LOOK,” “DRIVE-IN”, “DANGER” or any other word, phrase, symbol or character calculated to interfere with, mislead or distract traffic.