Utility poles along the public highway may be used for the purpose of attaching thereto or placing thereon, signposts, guideposts, warning signs, or other signs when prescribed by the director of transportation or county engineer.
Attaching guideposts or signs to utility poles
Ohio Rev. Code Ann. § 5515.04, under Chapter 5515 | State Highways - Use; Obstruction.
Ohio Rev. Code Ann. § 5515.04