As a retired civil engineer specializing in highway and traffic enginerring, methinks this idea would do much more harm than good. It would serve no purpose except for pedestrians, who would likely get a false sense of security and then get run over by paying more attention to the light than learning to judge the speed of the approaching vehicle. And turning vehicles? Why would a driver approaching pay any attention? The turning vehicle doesn’t necessarily brake and must yield the right of way anyhow. Has such a system ever been tested anywhere?
Just my two cents based on my over 50 years of experience.
so it does make sense. So much that you wonder if it has ever been tested. Is it possible that much like signal lights on both front and back, it contributes to more available and usable info transmitted at light speed . Just like any other signal light. While you have 50 years, perhaps you never thought of this before and are just now starting to examine the idea. I think if you look very closely at certain assumptions you are making you will find there is at least a case to be investigated here
I was taught in driver’s ed in high school not to pull out until the vehicle flashing its turn signal commits to the turn. Has always served me well.