So far about every state except pa and wv use the flashing yellow arrow traffic signal to improve safety on the road for other drivers and pedestrians. From what I understand pa rejected it in 2011 but will it by any chance be seen on the roads sometime soon here in pa because they may have reconsidered it.
I haven't heard anything official recently, but for the most part, PA doesn't seem to do any of the weird phasing that necessitates a FYA. There may be a few exceptions, but for most of the permissive/protected movements, the doghouse is still being put in. One of the things I gotta give PennDOT credit for.
I don't picture PA (or the rest of the northeast) getting many of these, as there was never an indication that these signals are intended to replace. In addition to that, it's confusing for people who aren't used to such a movement. Heck, the FYAs outside of Rochester, NY were inactive when I was there in mid-July, likely because people don't know how to react.
That being said, there's been nothing from PennDOT that I can find about the introduction of FYAs.
Frankly, as a PA native, the ones I see in CA just seem stupid.
Your statement "improve safety" is specious. FYA have a specific application regarding safety, and that's to prevent the "lagging green" trap when left-turners are stuck in the intersection after their direction turns red. It provides notice that the other direction is still proceeding on green, so do not complete your turn. FYA also have another application that is unrelated to safety. They allow flexibility to switch from protected-only phasing to protected-permitted or just plain permitted phasing during the day, by having a four-section left-turn arrow. G-Y-R would be the standard progression for protected, G-FY-Y-R would be protected-permitted, and FY-Y-R would be permitted only.
Now, FYA are MISUSED more than enough in most states, like NC or MI. Their intent is narrowly defined for the two purposes above. Some people seem to think that a green ball isn't good enough, and you need an FYA as well to convey that you must yield to oncoming traffic. I, for one, rail against the dumbening* of America, and refuse to support using a redundant traffic control device to aid the stupid.
* It's a word.
^ You didn't mention the option of allowing permissive lefts without bringing up the adjacent thru phase, which could be used for shorter cycle lengths.
I can see the flashing yellow arrow confusing drivers but at the same time it seems like something nice to have. I was surprised that pa still uses doghouses myself. At least most of the new traffic signals are switching over to red arrows instead of the red ball because that can throw off out of state drivers who are use to the red arrow.