Whenever, in the opinion of the board of county commissioners of any county, any road or part of road then established and maintained as a public highway is not needed, or the repairs of the same are burdensome and in excess of the benefits therefrom, they may at a regular meeting appoint a board of commissioners of three freeholders of the county as viewers, to view such road or part of road, and make report thereof to the board of county commissioners at their next regular meeting, setting forth fully their finding, and if they recommend a discontinuance of such road or part of road, then the board of county commissioners may order the same vacated: provided, that if such road runs on the county line between two counties, the county commissioners of both the counties interested shall appoint viewers and the concurrence of the county commissioners of both counties shall be necessary to vacate it.