A permit-issuing authority may issue annual permits authorizing a raw milk transporter to transport by motor truck raw milk to or from a milk plant, receiving station, or transfer station. The combined gross weight or gross weight on any axle or group of axles of the motor truck shall not exceed the limits established under section 321.463. The permit-issuing authority may specify weight limits or routes for each raw milk transporter or establish weight limits or routes under section 321E.8.