Allow higher density housing to be built without opposition (for example up zoning 1 level should be automatically approved: single family home can be torn down to build a duplex, etc). Then reduce and remove parking requirements.
Once that's done density will just go up on its own and... cars don't scale. Traffic will absolutely murder everyone and they'll start demanding public transit.
However this whole path is killed via NIMBY.
I see so many new residential projects with small lots or apartments. That's great! But still the zoning forces just housing, so its just homes on homes on homes for miles.
Where does the bus go? If you have dense city cores with business, commercial, and shopping it makes sense.
Living near Austin, I could take a bus to a place like the domain and have shaded walkways where I could walk to most shops without dying of heat stroke.
If I'm not going to the domain, I'm looking at businesses with huge parking lots strung along stroads. Walking from the bus drop off to a store might just kill you on a day like yesterday where it was 108F, and parking lot temps are closer to 130F.
Also getting to where you want to go over the huge spread out cities may involve waiting for 5 or 6 different busses.
And then hopefully your park and ride is being watched and you're windows aren't broken out.
Car culture builds car cities. Once you have a car city it's nearly impossible to fix it... it's too big and expensive and low density to fix.