All rights of way of state highways shall be used exclusively for public highway purposes: Provided, The secretary of transportation may authorize such other uses of such rights-of-way as will not interfere with public travel thereon and which are in conformity with applicable state and federal laws, rules and regulations relating to highways. The secretary of transportation is authorized to remove unauthorized structures, objects and facilities which are located upon the rights-of-way of state highways. Nothing herein shall be construed to affect the rights of public utilities and persons or associations maintaining facilities on state highway rights-of-way pursuant to law.