Ohio Rev. Code Ann. § 5555.23

The boards of county commissioners of two or more counties, acting as a joint board, may, by a resolution passed by unanimous vote, order the construction, reconstruction, improvement, or repair of any road located in said counties, or extending from one of said counties into or through adjoining counties, or along the line between said counties, and the joint board shall thereupon proceed with the improvement as if it were constructed upon a petition filed therefor.