In addition to roadside rests provided for by any other act of Assembly, the board of county commissioners of each county and each board of township commissioners and each board of township supervisors are hereby authorized and empowered to construct, erect and maintain roadside rests adjacent to county and township roads for the health, safety, welfare and accommodations of the traveling public. The location and size of such roadside rests shall be determined by the county or township constructing it. No roadside rests shall be constructed or erected pursuant to this act unless surrounded on all sides, except that side which fronts on a county or township road, by at least twelve hundred feet of Federal or State-owned lands in which no commercial signs or other advertising media are situated or authorized, or by privately owned lands the owners of which have irrevocably agreed in writing with the board of county commissioners or the board of township commissioners or the board of township supervisors, as the case may be, that no commercial signs or other advertising media or commercial enterprises will be permitted thereon or within twelve hundred feet thereof without the written permission of the board of county commissioners or the board of township commissioners or the board of township supervisors, as the case may be, or by an area of at least twelve hundred feet which is zoned to prohibit the erection of commercial signs or other advertising media or commercial enterprises thereon. Three such roadside rests may be erected in each county.