Mo. Rev. Stat. § 61.240: General duties (second, third and fourth class counties).

The county highway engineer shall, personally or by deputy, inspect the roads, culverts and bridges of every district in the county as often as practicable, and upon written complaint of three registered voters in any district of the bad or dangerous condition of the roads, bridges or culverts of the district, or of the neglect of duty by any road overseer of the district, or of neglect of any contractor on roads let by contract, the county highway engineer at once shall visit the road and investigate the complaint, and if found necessary at once shall direct the overseer of the district to place the road in good condition.