well, first 30mph is a little fast to be going in the turning lane approaching the intersection.it does not give you enough time to stop at that speed. but if the traffic light turn signal light turns yellow while you are in the intersection, or you pass that line you said. you proceed thru it. there should be no one else coming from any other direction because you had the turn arrow. so, you should have no problem making it through before turning red.
That was the case before we had flashing left yellow arrows. Now the solid yellow arrow comes after both the solid green and the flashing yellow arrows. If you didn’t see what it was, which could easily be the case if you just looked at the green light changed in to the turn lane and entered the intersection to make a left, then you suddenly notice the solid yellow arrow, it can lead someone to think that they didn’t notice the green arrow, or that the green arrow is burned out, and that they have a protected turn, when they actually don’t.
You know what I noticed last week? We now have a flashing right yellow arrow at an intersection. Apparently they think people don’t know that you can make a right turn on green now, or that people won’t know that right turn on red is a thing.
Saw one today, flashing yellow arrow, then solid yellow arrow, maybe 5 seconds then red arrow. I would still pull into the intersection to turn if no one is there, if it is stacked up I would stop at the light if safe to do so. .
Probably to remind drivers of the need to yield to cross traffic. If your light is anything other than green, you don’t have the right of way. For that matter, I got honked at once because I had a green light to make a right turn but there were pedestrians in the crosswalk. Apparently the driver behind me couldn’t see them.