No railroad, railroad company, railway company, or person, firm, or corporation operating any line of railway in this state shall be required by the commission, or otherwise, to alter its tracks at any underpass, railroad trestle, or bridge; to alter the grade of any public road or highway at any such underpass, railroad trestle, or bridge; or to otherwise relay or reconstruct any portion of its tracks, or other structures, or any portion of any public road or highway, in order to accommodate any motor vehicle exceeding 12 feet six inches in height.