These rules and regulations are adopted pursuant to R.C. § 711.09. The provisions of R.C. Chapter 711 shall apply to all plats, subdivisions, and conveyances of land in the city or within three miles of the corporate limits thereof. There is adopted a plan for the major streets or thoroughfares, for the parks and other open public grounds of the city and for all territory within three miles of the corporate limits thereof, such plan consisting of all existing state highways and other major streets or thoroughfares and parks and other open public grounds in the city and such territory.
(`63 Code, § 1111.01)