[tedsuo]

One of the big arguments against public transit is that it's infeasible to dig tunnels. If this project succeeds, I wonder what kind of contorted logic will arise, arguing that digging tunnels for cars is feasible, but digging tunnels for subways is still infeasible?

[marcell]

I thought the reduced diameter needed for cars allows lower cost/faster tunneling. Also, making it for cars solves the "last mile" problem that makes public transit unusable in suburban settings.

[yongjik]

Not so sure about that. Some subway tunnels are barely wide enough to fit a single train. I don't think a car tunnel can be much smaller, even if you only allow sedans and somehow find another way to send an ambulance in case of emergency.

[wahern]

I think all the subway tunnels in the U.S., including those in Boston, Chicago, and NYC, are >24 feet in width. The London Underground's deep-level tubes are less than half that at <12 feet in diameter.

That said, I don't think American cities could run subway cars as small as in the London Underground even if they wanted to because of the Americans with Disabilities Act (ADA).

Also, it might be difficult to make cars that small that pass muster under Federal safety regulations. AFAIU, Federal regulations basically require subway cars to be built like tanks.

EDIT: >24 feet just seems too wide for the old, deep tunnels in the U.S., but I can't find any references that aren't from books at the turn of the 20th century, which have very inconsistent numbers. I said >24 because that seem to be the width of old cut-and-cover tunnels and newer deep tunnels. I'm going to go out on a limb--based on random sources--and guess that the really old tunnels still in use might be closer to 16 feet in diameter. Feel free to correct me.

[capkutay]

The most expensive part of subway construction - both time and cost - is building the stations...which get significantly more expensive the lower they are underground.

Also modern subway tunnels are typically constructed with a larger diameter than what the Boring company supports.

[pas]

The problem is, that it's veeeery low density if only a few people sit in one car.

Sure, with increased efficiency and better energy economics, that's not a problem.

[cracell]

Couldn't you just make smaller trains that fit in the same tunnels?

Sure tons of cost for R&D but just because the tunnels are smaller doesn't mean they could only be used for cars in the long term.

[adventured]

That appears to be the intention of sorts. Sleds that hold numerous passengers (8-10?).

You can see one in the CG demo, in the first few seconds of the video, on the right:

https://www.youtube.com/watch?v=u5V_VzRrSBI

[pas]

also at 0:48

[pas]

And rewatching the video, I wonder... currently a subway / metro car holds 50-100 people (and there are about 5-7 carriages linked), but subways follow each other at best 3-5 minutes. (Or ~1-2 in Japan in rush hour.)

So about 250 - 700 people are moved in 3 minutes, that's 80-230 per minute. If sleds follow each other by let's say 2-3 seconds, and each car holds 1-8 people, then that's 20-240 people per minute. With the added benefit better granularity, and you don't have to switch lines, metros, you don't even have to leave your seat.