The department is authorized to install or provide for the installation of and to operate or provide for the operation of vending machines in safety rest areas constructed on or located on the rights of way of the state highway system. The vending machines may dispense nonalcoholic beverages, snacks, candy, cigarettes, and other articles as determined by the department to be necessary or desirable for the traveling public at reasonable prices. The prices charged for these products shall approximate the prevailing rate within the area for similar items so as not to compete unfairly with private enterprise, such prices to be set by the department.