The board of county commissioners of every county shall cause to be inspected every county road upon which United States mail is carried and the highway commissioners of every township shall inspect, or cause to be inspected, every mail route within their township which is not located on a county road, after the occurrence of every storm, and as soon as possible after complaint is made, and shall at such times inspect the conditions of the culverts and bridges, and within a reasonable time repair the same, and remove from the highway all obstructions that may have been caused by the elements, and do everything reasonable to keep such mail routes clear and free for the distribution of the mail.