Mo. Rev. Stat. § 229.160
All persons owning, controlling or managing threshing machines, sawmills and steam engines or gasoline tractors are required, in moving the same over public highways to lay down planks not less than one foot wide and three inches in thickness on the floors of all bridges situate on the public highways, while crossing the same with such threshing machines, sawmills, steam engines or gasoline tractors, and in the event any person owning any such machinery shall cross or attempt to cross any bridge upon any public highway with such machinery who shall neglect or fail to lay down said planks as a protection to said bridge and who shall, by reason of such neglect cause injury to any such bridge, he shall be liable for double the amount of such injury to be recovered in the name of the county or any subdivision thereof, to the use and benefit of the road and bridge fund.
§ 229.160, RSMo