I don’t think you understand how this concept works. Because commuting by car after increasing the road capacity gets easy again, and because it’s also the most co convenient and (for a brief moment) fastest way to commute from point A to B, people switch over from using other means and the roads get saturated again soon after. You cannot increase the capacity to accommodate everyone driving, and everyone absolutely would want to drive if possible. It has nothing to do with the city’s ability to deliver, it’s about human condition and our innate need to make lowest effort possible.

Also, this is such a wildly American take, from a European perspective. No one expects city to somehow make driving cars easy here, not anymore. Would also be wild from NYC or Chicago perspective. Having lived in NYC I would not replace Subway with a car in that large of a place. Even without traffic it would take too long to move about.