No person shall erect or maintain at any grade crossing advertising signs, billboards, unauthorized warning, danger or stop signs, or signs of any kind except those authorized by law or by this Commission, or signs incident to railroad operation, and insofar as it has power, every railroad company shall keep its right-of-way at every such crossing clear of such billboards or unauthorized signs.
Ill. Admin. Code tit. 92, § 1535.210