Most signs are governed through the Ohio Department of Transportation and information can be found on their website. The entire sign code document can be found here.
Chapter 2J:
Specific Service Signs
“… guide signs that provide road users with business identification and directional information for eligible services and attractions. Eligible service categories shall be limited to gas, food, lodging, camping, and attractions.”
Chapter 2K:
Tourist-Oriented Directional Signs
“A facility shall be eligible for tourist-oriented directional signs only if it derives its major portion of income or visitors during the normal business season from road users not residing within 10 miles of the facility and attendance at which is no less than 2,000 in any consecutive twelve month period.”
Additional information can be found here and here.
