238.236.  Sales tax for transportation development district on all retail sales authorized — ballot form, content — rate of tax collection — fund created, lapse to general revenue prohibited — distribution — procedure to repeal tax. — The portion of Interstate 44 from State Highway 360 west to State Highway PP in Greene County shall be designated as "Captain Aaron J. Eidem Memorial Highway".  The department of transportation shall erect and maintain appropriate signs designating such highway, with the costs of such designation to be paid by private donations.