German have been battling this phenomenon with technology and got pretty far as public transport is concerned. Railway sidings and bridges are left, and as things are repainted and renewed these will go away soon (our company among many many other things makes paint additives geared for that, so I know). Sadly the idiots are upgrading their arsenal and (especially in Berlin) move on to other non sense like scratching windows with patterns. (We have something for that too )

The NYC principle that graffiti sets the stage for other crime has been studied in Germany and proven not be the case. Sadly we are far too self policing.