Any board of county commissioners may grant to any person the right to build and maintain tramroads and railway roads upon county roads under such regulations and conditions as the board may prescribe, and may grant to any person the right to build and maintain cattleguards across the entire right-of-way on any county road, under such regulations and conditions as the board may prescribe: PROVIDED, That such tramroad or railway road shall not occupy more than eight feet of the county road upon which the same is built and shall not be built upon the roadway of such county road nor in such a way as to interfere with the public travel thereon.