Road tunnels exist and have been built all around the world, these kinds of ideas have been tried and ultimately general underground road tunnels are just not economical or particularly safe.
Thunderf00t has done a series of videos debunking these claims [0,1,2]. Unfortunately Elon has a habit of frankly lying which I think does serious harm to public perception of these things.
These kind of infrastructure problems are just hard and have a ton of trade offs, there is no silver bullet.
[0]:https://www.youtube.com/watch?v=HBtL3qDvdZc [1]:https://www.youtube.com/watch?v=0ezF7NmwQZs [2]:https://www.youtube.com/watch?v=Hyy-19qyNWE
In the same vein, why underground instead of light rail?
See, open air systems like those are much easier to service. Removing a crashed car from that requires just a big crane.
Cost also vastly increases, likelihood of total failure as well. Big tunnels need big supports and big service ducts.
It seems like such a waste of time for people to try and debunk these claims from people who are very competent and have access to the best in people and technology. Do they want a world where people don't try new things and make great improvements? One should really encourage people with a track record of getting people together to do amazing things to continue to do so. Elon Musk has stated that he thought that SpaceX had a 10% chance of success. I'm glad he could look at that chance of failure and tried anyway.
Blue Origin is building a large re-usable rocket like the Starship called the New Glenn, but its first launch date keeps slipping. I would guess that Starship will be launching first but it is really cool that two groups are working on such rockets.
There are fields where physical limits were already reached, for example rocket engines specific impulse has barely improved since the 60s because of fundamental chemistry, but this is not the case for tunnels.
Provided enough funding it should be possible to dig faster, and cheaper per km.
> the safety issues of a car breaking down in a tunnel
The cars have front radar and can break. It would stop the line but I don't see how it is a safety issue. Most danger in tunnels is from bidirectional traffic that Boring avoids.
> the enormous cost with digging deeper tunnels
The same could have been said about other Elon Musk projects. Nobody is surprised that an electric car can have better performance and power and yet a diesel driven tunnel boring machine can not be improved? Tunneling is incredibly conservative and uses both diesel driven tunnel boring and diesel driven locomotives to transport out the dirt. The inherent problems of having lots of diesel engines a tunnel are quite clear and eliminating it has clear operational advantages.
> underground road tunnels are just not economical or particularly safe
What the evidence for underground one-way tunnels not being safe?
> These kind of infrastructure problems are just hard and have a ton of trade offs, there is no silver bullet.
Therefore we should try to improve it with modern technology from other fields? Its not a silver bullet, it is tacking new technology from automotive and aerospace and applying it to tunneling and mass transportation.
!? I'm not a tunnel building specialist, but a cursory search seems to indicate that tunnel boring machines commonly already are electrically powered by simply using a very long high voltage cable stretching all the way from the tunnel entrance. Whether that cable then connects to the electricity grid, or to a bunch of temporary diesel generators stationed outside of the tunnel is a different matter, which in any case doesn't bear on the tunnel boring itself.
It's unfathomable to me that people believe car tunnels are the future of anything.
Right now The Boring Company is trying to recreate an underground train in Las Vegas, and is already behind schedule and running into issues people predicted before this started:
https://www.theverge.com/2020/10/16/21519692/elon-musk-borin...
One system is cheaper because the units are mass produced far more often and the system is more flexible.
Carrying around a battery rather then having complex high power electronics along the tunnel seems like a no brainier as well.
Las Vegas is literally a first of its kind system, being a few month behind is not surprising or concerning. And the problems have to do with specific fire codes, not any inherent flaw in the system.