[hyeonwho2]

While that density is impressive, Japan is the only place where that density happens. Here in Korea, we generously run a train only every twenty minutes on the Seoul-Busan corridor. I would argue that this is much higher than what is likely to be attained in California, as both Seoul and Busan have well-developed public transit infrastructure and a comparatively low rate of car ownership, which reduces the burden on riders at both ends.

(Even ignoring the TSA, 6B in ridership fees to be made up, and general messiness of American commuters.)

So now your 1300 passengers, generously, are spread out over 20 miles of freeway, instead of three.

(2600 passengers/20 miles) * (1 car / passenger) * (250 lane-ft/car) * (1 mile/5280ft) = 6.1 lanes.

Now, that was assuming one passenger per car. Add a single bus per mile-lane (seated passengers only) and this drops to four lanes. With self-driving cars and more busses, you could safely add only a single dedicated self-driving car lane and a sigle dedicated bus lane in each direction, and still have room to increase "ridership". For the price, I think that is ridiculous.