Freeways move a tremendous amount of cars. Average traffic counts for Hwy 5 in SD-LA range between 10k-20k per hour!
Agree with NorCAl idea of starting with the ends first. But… even with a terrific rail system I’m not sure how much a dent you would put in those traffic counts.
Wider freeways is my vote both in cost and effectiveness.
Thumbs down to the transit folks who has not invested and expanded the freeway system to keep up with So Cal growth.