One of those artists who actually improve the appearance of modern freight cars. Yes, I know, it's still vandalism, and illegal, but some do make good modern art.
One of the keys to keeping the railroads somewhat content to ignore the graffiti is very simple - leave the railroad lettering legible, or repaint it to fit the art, whichever works best. As long as the required stuff is there, most roads today don't care about another coat of paint.
Another is DON'T GET HURT, and don't endanger anyone else! An injury, or worse, is one of the quickest ways to bring the law down on you and others.