The permanence or durability of outdoor signage and fleet graphics depends on three main factors. These factors are the construction, the application, and the environment in which the graphic is exposed. Fade resistance is but one property that determines the permanence. More printing of outdoor signage is being done more by digital printing and less by screen printing. The fade resistance of graphics printed by piezo ink jet inks is approaching that of graphics printed by conventional screen printing methods. Retained solvents, though, are limiting the permanence of some demanding graphics printed by solvent-based piezo ink jet inks.
Ronald R. Adkins, "Image Permanence: Commercial Signage/Fleet Graphics" in Proc. IS&T Int'l Conf. on Digital Printing Technologies (NIP17), 2001, pp 162 - 165, https://doi.org/10.2352/ISSN.2169-4451.2001.17.1.art00033_1