Ohio Rev. Code § 5535.07
The director of transportation shall take over, for maintenance purposes such mileage of the system of intercounty highways outside of municipal corporations, as has not been constructed by the state or taken over by the state for maintenance. All such portions of the intercounty highway system not at present under state maintenance shall be first improved by the county to an extent which in the opinion of the director will permit economical maintenance for the purpose of making them passable for traffic.
The director shall maintain said roads and highways, and the respective counties and townships of the state in which such roads and highways are located shall be relieved of the duty of their maintenance. For the purpose of this section, maintenance does not include the construction of any new bridges or culverts or the replacement of any bridges or culverts destroyed by the elements or by natural wear, nor any construction work changing the type of construction existing on said roads at the time the same are taken over in accordance with this section.
This section does not prevent the authorities of any county or township from co-operating with the state in the construction, maintenance, or repair of any section of such highways within such county or township.
R.C. §5535.07