The portion of Interstate Highway 70 between mile marker 69 in any county of the fourth classification with more than twenty-three thousand seven hundred but less than twenty-three thousand eight hundred inhabitants and east to mile marker 123 in any county of the first classification with more than one hundred thirty-five thousand four hundred but less than one hundred thirty-five thousand five hundred inhabitants, except where otherwise designated, shall be designated the “U.S. Submarine Veterans’ Memorial Highway”, and shall represent in its fifty-four-mile stretch the fifty-four submarines lost during war and the Cold War. The department of transportation shall erect and maintain appropriate signs designating such highway, with the cost of such signs to be paid by the Submarine Veterans’ Association.