Tex. Transp. Code § 201.705

The department may enter into agreements with local governments, convention and visitors bureaus, chambers of commerce, or other governmental or nongovernmental entities for the purpose of purchasing supplies and materials to be used for aesthetic entrances to municipalities or census designated places along interstate highways or highway corridors or ornamental decorations along overpasses, provided that the department may not expend appropriated funds solely to plan, design, or construct aesthetic entrances to municipalities or census designated places along interstate highways or highway corridors or ornamental decorations along overpasses.