Any road established by petition and any road improved by petition under this chapter shall be administered and maintained by the county under chapters 306, 309, 314, 317, and 318. However, the fact that right-of-way is donated by property owners for the establishment of a road or a portion of the cost of a road improvement is paid by property owners under this chapter, does not preclude the board of supervisors from exercising its responsibility over these roads as secondary roads.