Hi, traffic engineer here.
That's never going to happen. It's nothing but a tech-bro bullshit fantasy.
Why? Because cyclists and pedestrians exist. In order to make it possible for the kinds of gains you're talking about to happen, every road user has to be an autonomous vehicle, but (aside from freeways) streets simply do not work that way and never will.
(Oh, and also: even at the limit, the best it can ever accomplish is to be an inferior approximation of a train.)




No, that's not how traffic works. That's like saying a pipe can flow an infinite amount of fluid when you used a liquid instead of a gas because you got rid of the empty space between particles.
Even with theoretically-perfect timing and control, the road still has a finite capacity because cars take up a certain amount of space, both stationary and moving (following distance is still a thing even with computer control because of the mechanical limitations of brake performance). Moreover, it isn't that much higher than we can manage with humans driving the vehicles already.
The only ways to exceed that limit are to make the vehicles smaller (e.g. bikes) or pack more people into them (e.g. buses or trains).