Ohio Rev. Code § 5535.06
In all cases where a county or township has constructed or improved any intercounty road, the director of transportation, upon request, shall, within sixty days, indicate what changes or improvements will be required in the road in order to bring it up to the approved standard of construction of such roads. In any case where such road is about to be constructed, reconstructed, or improved, the director shall, upon application, indicate within sixty days what changes will be required in the plans and specifications to bring the road up to the standard required by the state for the construction of intercounty highways. Whenever the changes specified by the director have been made, or when such roads have been constructed according to the plans and specifications approved by him, the roads shall at once become state roads.
The board of county commissioners, upon application by the board of township trustees, shall specify in like manner what changes are required in any township road in order to bring it up to the standard of construction maintained for county roads, or, in case of the construction of any new improvement, the board of county commissioners shall indicate what changes in the plans and specifications will be required to bring the road up to the standard of construction required for county highways, and when a township highway is so improved or constructed, in accordance with the standard fixed, it shall be a county road.
R.C. §5535.06