The department may designate interstate safety rest areas, as appropriate, as locations for memorial signs to prisoners of war and those missing in action. The department shall adopt policies for the placement of memorial signs on interstate safety rest areas and may disapprove any memorial sign that it determines to be inappropriate or inconsistent with the policies. The policies shall include, but are not limited to, guidelines for the size and location of and inscriptions on memorial signs. The secretary shall adopt rules for administering this program. Nonprofit associations may have their name identified on a memorial sign if the association bears the cost of supplying and maintaining the memorial sign.