Why don't they just build out BART between Millbrae and Santa Clara? Once the Silicon Valley Extension is finished, BART will be almost a loop around the Bay except for that gap.
Plus the fact that the citizens (through their representatives) voted against it decades ago, so it was removed from the original plan. Given the current fuss among the citizenry over similar problems with running the nascent high-speed rail up the Caltrain corridor, I’d guess a vote today on BART would have the same outcome.
Couldn't they build a tunnel? With a tunnel, the requirements for eminent domain would be relatively limited (portals, station entrances, maybe some ventilation/utility buildings)
Sydney, Australia's new metro system which is being built relies mostly on tunnels (plus some conversion of existing surface lines, and elevated rail in outer suburban areas where land is relatively cheap). Sydney's metro area (5.2 million) isn't hugely larger than the Bay Area's (4.7 million).
And we are out of money / unwilling to pay for such projects. Australia is still relatively swimming in its natural resource boom and has funds to do that. And political willingness to invest in public transportation that's clean and efficient.
In California, public transport seems to be relegated to the status of a homeless mobility system / shelter, that most people reluctantly take and have to wonder why it's so badly operated. I don't think the idea will get far to tunnel under the rest of the peninsula. We can't even sort out the remaining 1 mile of Caltrain that was planned to connect to downtown SF and the Transbay center.
Aside from that, I believe there's a groundwater level problem under most of the places where such a line would go? I'm not an expert on that though.
On a per capita basis, the US is richer than Australia. According to 2019 IMF estimates, US's nominal GDP per capita is US$65,111 (ranked 7th), Australia's nominal GDP per capita is only US$53,825 (ranked 10th) [1]. Similarly, the US's PPP GDP per capita (2020 IMF estimates) is US$67,426 (ranked 10th), while Australia's is only US$54,799 (ranked 19th) [2].
The US is a richer country than Australia in both relative (per capita GDP) and absolute (overall GDP) terms (and both nominally and at PPP). If Australia can afford tunnels, why can't a richer country like the US afford them too? (Especially in the Bay Area Peninsula, which is one of the wealthiest areas in the whole of the US.)
[1] https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nomi...
[2] https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)...
