Build better transportation to support density, then add density. But to add density first on the promise of improved transportation has led to the traffic mess of today.
Yeah, you need transport. Historically speaking, this has been a chicken-and-egg problem; to get density high enough for reasonable public transit, it needs to be practical to get by without a car. To get by without a car, you need reasonable public transit. Usually people build transit nobody will use in hopes that people will then build housing.
We've got an opportunity right now in silicon valley to do it the other way around, because ridsharing in silicon valley is so good that it's totally practical for an upper middle class person to live without a car (I got rid of mine about a year ago) - this means that you can talk me into renting a place that doesn't have parking.
Now, hear me out. Yes, I know uber being cheap is temporary, but this presents a unique, i think, opportunity to build housing without parking first, and then generate demand for public transit, rather than the other way around as you suggest. Now, remember that in Silicon Valley, at least, the people who get into new housing are usually well off. If you can afford the rent on a newly built unit, uber is cheap for you, and you have the political power of an upper middle class person.
Build the housing on a rail line; which I think is standard practice, but right now we build housing and a giant parking structure. The opportunity right now is that the rail line is not an alternative to a car, but uber + the rail line is - you can use that to start with the egg rather than the chicken. Build the housing next to transit without car parking spaces, and then let the residents agitate for better public transit once uber starts charging profitable prices.
I wouldn't know, but either way, not all your housing needs to be built for parents with small children. You set it up so that those of us without kids don't have to drive, and especially in the bay area, you've solved a lot of the traffic problem.
Anecdotal, but everyone I know with kids already lives some distance out and commutes in. New, expensive apartment buildings in this area seem to be mostly the domain of people without kids.
to add to my other comment, I in no way want to say that ride sharing is for everyone; just like driving, there's a lot of reasons why a lot of people don't want to do it. I'm just saying that ride sharing is cheap and convenient enough for a lot of people, probably even the majority of people who inhabit the newly built apartments around here, which can't be said, really, for public transit.
That certainly is an ideal, however, consider it in an economics point of view:
There's no need to spend more money on transportation if there's not the amount of people to pay and ride on it. The unknown here is if the population density will ever go up to support a new system being paid for, now.
Adding density first proves demand, and although messy, transportation would NEED to improve somehow.
