Generally, restrictions on cars make public transport better automatically, as they make buses work better.

Alternatives naturally become more viable over time as more and more people find car use impossible, but its kind of hard to tell in advance which lanes of public transport are most necessary to improve. So imo the best solution is just to do it, and then see what happens and adapt. It's too hard to plan out everything in advance, and if you try you get deadlocked politically and nothing ends up happening. So you just find the best lever you can to reduce traffic immediately, and just start pressing it. But you warn everyone that you're pressing it, and when you do so you do it slowly.

The reality is that a lot of traffic is simply unnecessary, and dissipates once you add some friction. The most extreme example of that is the rise of remote work during and after Covid. As it turns out, none of these people actually needed to go anywhere.

And more generally, cars induce their own demand simply by virtue of being the fastest and most comfortable option, and they shape the environment around them to depend on them. Small local shops get outcompeted by distant behemoths due it being more convenient to drive. People move to a large house in a distant suburb rather than a small apartment because they know it's just thirty minutes away from work by car anyways. The easier it is to drive, the more entrenched driving becomes. And any way you slice it, undoing that process will cause pain, so you might as well go ahead and start, because you're never going to find a way to prevent the consequences anyway.

None of the changes in the comment make owning a car impossible, they just make driving marginally less privileged over walking and biking.