It applies before with the goal of not getting to the point that all the lanes are full of cars.

Roads have a carrying capacity, or bandwidth, which at after a certain speed say 80mph, doesn't increase. Traffic is unavoidable once enough cars come onto the road at the same time such that they exceed this limit, and so you get traffic where people are speeding up and slowing down and that cascades back.

At the end of the day, there is no amount of rules that will bypass the fact that there is a hard limit to how many cars can pass through any given point at a certain speed.

That's true but the rules get us closer to that theoretical maximum.