And the freeways can support this how?
We really need to stop assuming that people are going to make heavy freeway use, and permit more scalable transit. Run BART the short way between SF and SJ, build many clusters of high density along heavy transit routes. Let the current freeway dependent population continue to use them, but build housing so that people can get to jobs without using single-occupancy passenger cars.
I don't think we can stop that assumption until we have much better public transit. Cause if the trains aren't running where I need to go, when I need to get there, I have to drive.