Eventually they will reinvent trains! (:
To my understanding the idea of the white light is that self-driving cars will at some point be able to coordinate well enough between each other that standard traffic control at intersections would be unecessarily inefficient - not a crutch to assist self driving cars' reliability in some way (it'd be a more challenging navigation scenario than just waiting). Don't think it'd work out in practice any time soon, though.
It’s already unecessarily inefficient! I can’t count the number of times I’ve stopped at a red light and waited for 35 seconds with no cross traffic only to be allowed to cross just as a cohort of 50 vehicles has to transition from highway speed down to idle. So much fuel and time is wasted due to bad arbitration schemes!
Not that we don't lose the plot sometimes too... there are plenty of light-controlled roundabouts near me. One has to wonder why.
Sometimes, however, the purpose of traffic lights is to keep the flow of traffic slower to improve safety for pedestrians, bicycles, and other drivers. Especially in down towns when it seems like the light cycles are specifically designed to thwart your desire to simply cruise through at the speed limit, that might literally be happening.
This will be used as a special sign to indicate to drivers that autonomous vehicles are controlling the road at that moment. Today, traffic lights tell us when to stop or go on, but autonomous cars can communicate among themselves and with these traffic lights to organize the traffic flow in a faster and more precise way than humans.
in other words corporate interests cant develop a tech that works reliably so they take over a public chattel to change the standard for everyone so they can operate a weak tech development.