Meanjoe hit on #1 in my experience - anticipation, as in see it coming, let off and pick a path before you get there. That has to have a X10 importance over other considerations. Even with a constant hard rain, complete snow pack or complete ice, there will be occasional bad spots where the anticipation, and time to react. gives a safety cushion.
I’m aware that the system measures either wheel speed or drive train speed, not actual car speed.