Iowa Code § 327G.2: Crossings — signs.

Every corporation constructing or operating a railway shall make and construct at all points where such railway crosses any public road good, sufficient, and safe crossings and erect at such points, at a sufficient elevation from such road as to admit a free passage of vehicles of every kind, a sign with large and distinct letters placed thereon, to give notice of the proximity of the railway, and warn persons of the necessity of looking out for trains. Any railway company neglecting or refusing to comply with the provisions of this section shall be liable for all damages sustained by reason of such refusal or neglect, and it shall only be necessary, in order to recover, for the injured party to prove such neglect or refusal.