Ohio Rev. Code § 5555.02
The board of county commissioners may construct a public road by laying out and building a new road, or by improving, reconstructing, or repairing any existing public road or part of an existing public road by grading, paving, widening, altering, straightening, vacating, changing the direction, draining, dragging, graveling, macadamizing, resurfacing, applying dust preventives, or otherwise improving the same, and, where an established road has been relocated, the board may construct and maintain connecting roads between the old and new locations as will provide reasonable access thereto. The board also may place a county road on nonmaintained status pursuant to section 5541.05 of the Revised Code. The board may purchase or lease, erect, and maintain automatic traffic signals at intersections of public highways outside municipal corporations as necessary for the protection of the public traveling upon those highways. Automatic traffic signals shall not be placed at intersections of public highways on the state highway system unless the board first obtains the approval of the director of transportation.
This section does not apply to roads or highways on the state highway system, except such portions as the board constructs under plans and specifications approved by the director and under the director's supervision and inspection.
R.C. §5555.02