Grünpfeile were really new in West Germany after the reunification. My brother told an anecdote from when he once drove through Hamburg and saw a Grünpfeil there, which had a sign below it explaining how it worked (something like: "Grüner Pfeil = Stoppschild für Rechtsabbieger", "green arrow = stop sign for right-turning drivers"). He quipped that this was probably the only traffic sign ever to come with its own manual.