Shelters for the convenience and comfort of persons waiting for buses or other public transportation may be placed and maintained within the right of way of any street or highway, including right of way for streets and highways within municipalities, after a license or permit for the shelter and location is obtained from the highway authority having jurisdiction. Placement and location of shelters on any street or highway within a municipality shall be subject to the approval of the corporate authorities of such municipality. The owners may place advertising on the shelters if authorized by the license or permit, provided, however, that no political advertising shall be placed on any shelter on any street or highway at any time and further provided that advertising on shelters shall be limited to one-third of the vertical surface of the shelter. Shelters shall not be placed or maintained on that portion of the right of way designed and used for vehicle traffic and further shall not be so placed as to impair the street or highway or interfere with the free and safe flow of traffic.