(1) The county board of each county shall select and designate, from the laid out and platted public roads within the county, certain roads to be known as primary and secondary county roads. Primary county roads shall include (a) direct highways leading to and from rural schools where ten or more grades are being taught, (b) highways connecting cities, villages, and market centers, (c) rural mail route and star mail route roads, (d) main-traveled roads, and (e) such other roads as are designated as such by the county board. All county roads not designated as primary county roads shall be secondary county roads.

(2) As soon as the primary county roads are designated as provided by subsection (1) of this section, the county board shall cause such primary county roads to be plainly marked on a map to be deposited with the county clerk and be open to public inspection. Upon filing the map the county clerk shall at once fix a date of hearing thereon, which shall not be more than twenty days nor less than ten days from the date of filing. Notice of the filing of the map and of the date of such hearing shall be published prior to the hearing in one issue of each newspaper published in the English language in the county.

(3) At any time before the hearing provided for by subsection (2) of this section is concluded, any ten freeholders of the county may file a petition with the county clerk asking for any change in the designated primary county roads, setting forth the reason for the proposed change. Such petition shall be accompanied by a plat showing such proposed change.

(4) The roads designated on the map by the county board shall be conclusively established as the primary roads. If no agreement is reached between the county board and the petitioners at the hearing, the county clerk shall forward the map, together with all petitions and plats, to the Department of Transportation.

(5) The department shall, upon receipt of the maps, petitions, and plats, proceed to examine the same, and shall determine the lines to be followed by the said county roads, having regard to volume of traffic, continuity, and cost of construction. The department shall, not later than twenty days from the receipt thereof, return the papers to the county clerk, together with the decision of the department in writing, duly certified, and accompanied by a plat showing the lines of the county roads as finally determined. The county clerk shall file the papers and record the decision, and the same shall be conclusive as to the lines of the county roads established therein.