Tow Pro: Do Not Overtake Turning Vehicle signs

I saw the question about the signs in the topic title in the latest edition of CW, so thought I would go have a look at the outcome. The answer that was supplied to Des seems to me to be based on the law as it applies to a particular state. Here in WA it is optional to have either the graphic or the words. I believe it would be more helpful when giving an answer to a question like this to provide the legal position for the different states. I assume the target audience is the entire country not a single state? As an aside it took a while for me to track down the exact topic that was referred to in the magazine, there seems no easy way to make the connection.

John Geling, WA