Tunnels are our Transportation Future(austinvernon.eth.link)
austinvernon.eth.link
Tunnels are our Transportation Future
https://austinvernon.eth.link/blog/tunnels.html
48 comments
"Full autonomous driving" within a closed course set up like a metro system is 100% possible today. The hard part is all the weirdness of the real world and in this model you can shut most of that out.
Tunnels are simpler when you remove fossil-fuel exhausts and human drivers from the equation, ie. Teslas with FSD only.
You don't need as much ventilation since there are no products of combustion to exhaust, and the risk of crashes from human error are eliminated. Presumably the car software and the tunnels themselves can also be designed in a way where the risk of crash is near-zero.
You don't need as much ventilation since there are no products of combustion to exhaust, and the risk of crashes from human error are eliminated. Presumably the car software and the tunnels themselves can also be designed in a way where the risk of crash is near-zero.
One could even eliminate the heavy and potential dangerous battery with some sort of overhead wire or rail contact.
And since the cars can only move in one direction within a tunnel, one could eliminate the need for steering by placing them on a set of rails. And maybe use some sort of automatic control system to make sure the train stops when needed. Wait..
Yeah it's like you take a perfectly good argument "we should be able to make tunnels more efficiently" and then throw in Tesla fan-boyism and it just shuts off the critical thinking centers of the brain.
While I agree your argument sounds good and probably works for many cases, the fact is that I would use the system described in the Tesla scenario and I would never ride a subway in a place like Texas or Los Angeles.
Public transport is absolutely gross and legitimately scary in Los Angeles. However, if I could stay in my car I would totally use this system, also having your car at your destination is incredibly useful and not something you can do with a subway.
IMO they both serve different needs.
Public transport is absolutely gross and legitimately scary in Los Angeles. However, if I could stay in my car I would totally use this system, also having your car at your destination is incredibly useful and not something you can do with a subway.
IMO they both serve different needs.
Just make sure to update your rail cars once in a while so you don't end up with old pieces of shit that lose power every few km and give you tinnitus when traveling underground. Like some German cities.
Tunnels are hard because of fire risk, not just because of exhausts and electric vehicles simplify the one but complicate the other.
Just like software never crashes?
I'm not aware of any examples where car software 'crashed', in any vehicle, causing the vehicle itself to physically crash.
And if you're talking about FSD, most of those instances are from exceptions eg. unexpected pedestrian, parked truck, construction works.
Its fair to imagine that these tunnels will be custom-built for self-driving cars and will be totally controlled environments.
And if you're talking about FSD, most of those instances are from exceptions eg. unexpected pedestrian, parked truck, construction works.
Its fair to imagine that these tunnels will be custom-built for self-driving cars and will be totally controlled environments.
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It's just a matter of time as systems become more dependent on it.
> I'm not aware of any examples where car software 'crashed', in any vehicle, causing the vehicle itself to physically crash.
Toyota runaway acceleration caused by a stack overflow: https://en.wikipedia.org/wiki/2009%E2%80%932011_Toyota_vehic...
Toyota runaway acceleration caused by a stack overflow: https://en.wikipedia.org/wiki/2009%E2%80%932011_Toyota_vehic...
"On February 8, 2011, the NHTSA, in collaboration with NASA, released its findings into the investigation on the Toyota drive-by-wire throttle system. After a 10-month search, NASA and NHTSA scientists found no electronic defect in Toyota vehicles.
Driver error or pedal misapplication was found responsible for most of the incidents. The report ended stating, "Our conclusion is Toyota's problems were mechanical, not electrical." This included sticking accelerator pedals, and pedals caught under floor mats."
Driver error or pedal misapplication was found responsible for most of the incidents. The report ended stating, "Our conclusion is Toyota's problems were mechanical, not electrical." This included sticking accelerator pedals, and pedals caught under floor mats."
It's tiring seeing so many people imagining solutions to transport that look like "Cars, but...". Cars are large and cause congestion, even if you make them autonomous. They need to be stored when not in use, which requires turning over more and more inner city land to vehicle use. And it becomes a self fulfilling prophecy: the more space you allocate to large carparks and multilane roads, the more spread out your city becomes and the any alternatives become less viable.
But instead this subject got 1 tiny paragraph near the end, in which this viewpoint "a form of degrowth".
"We can build more batteries, more cars, and more tunnels. And humans will be better off for it."
Honestly I just disagree with this take so much... I'm very far from a strident environmentalist but it should be obvious that this isn't the way forward.
But instead this subject got 1 tiny paragraph near the end, in which this viewpoint "a form of degrowth".
"We can build more batteries, more cars, and more tunnels. And humans will be better off for it."
Honestly I just disagree with this take so much... I'm very far from a strident environmentalist but it should be obvious that this isn't the way forward.
Cars give you point to point, personal space, and climate control. Even in cities with lots of trains like Beijing or Tokyo, the commute is not a fun experience - I got tired of it within just a handful of business trips.
Walking can give you point to point, with more personal space than the frequent crush of a train or bus, but I don't think it's realistic to expect people to want to live in cities small enough that "always have a walkable commute" is a realistic goal.
Electric bikes/scooters/skateboards/etc seem like the best option in coastal California, but are a harder sell in places that get extreme weather. And have some issues compared to a car for the less able or more fragile.
Self-driving cars make congestion and usage probably worse, in my expectation, because you've eliminated one of the big downsides of cars, so I expect more demand for them compared to buses and trains.
Environmentally, the more realistic win - short of strict laws that basically just force people to not go with their first choice - honestly seems like just figuring out remote work. Reduce how often people have to travel across town at all. (That, and I'm not convinced that moving away for "perpetual growth forever" is such a bad thing.)
Walking can give you point to point, with more personal space than the frequent crush of a train or bus, but I don't think it's realistic to expect people to want to live in cities small enough that "always have a walkable commute" is a realistic goal.
Electric bikes/scooters/skateboards/etc seem like the best option in coastal California, but are a harder sell in places that get extreme weather. And have some issues compared to a car for the less able or more fragile.
Self-driving cars make congestion and usage probably worse, in my expectation, because you've eliminated one of the big downsides of cars, so I expect more demand for them compared to buses and trains.
Environmentally, the more realistic win - short of strict laws that basically just force people to not go with their first choice - honestly seems like just figuring out remote work. Reduce how often people have to travel across town at all. (That, and I'm not convinced that moving away for "perpetual growth forever" is such a bad thing.)
Dedicated bus lanes are our transportation future. The capital expense and engineering are minimal (but not nothing), the capacity improvement is vast, and route to zero emissions clear (electric buses).
Taking the bus on a dedicated lane is a thing of beauty.
Taking the bus on a dedicated lane is a thing of beauty.
> capital expense and engineering are minimal
San Francisco voters passed Proposition K, mandating a BRT line on the heavily-used Geary corridor in 2003. Yes, 2003!
It's 2021 and the furthest they've gotten is upgrading some signals and painting some side lanes. They haven't even begun construction of the dedicated inner lanes, which won't even run the full length of the corridor, anyhow. In fact, last I heard there are plans to scale things back even further.
Our inability to build transit isn't an engineering problem. It's not even really a capital expense problem, though don't underestimate the expense of building out dedicated lanes at-grade. It's a political and governance problem.
Last time I looked at the project details, IIRC about half of the $60 million budget was simply going toward repaving Geary Blvd, a benefit inuring almost entirely to cars. (They've postponed repavement so it could be rolled into, and hidden, by the BRT project budget.) If the BRT-specific changes were left out, the project would have been approved, finalized, contracted out, built, and finished a decade ago. The only reason it's taken so long is because of all the infighting that occurs for any infrastructure project beyond building roads.
San Francisco voters passed Proposition K, mandating a BRT line on the heavily-used Geary corridor in 2003. Yes, 2003!
It's 2021 and the furthest they've gotten is upgrading some signals and painting some side lanes. They haven't even begun construction of the dedicated inner lanes, which won't even run the full length of the corridor, anyhow. In fact, last I heard there are plans to scale things back even further.
Our inability to build transit isn't an engineering problem. It's not even really a capital expense problem, though don't underestimate the expense of building out dedicated lanes at-grade. It's a political and governance problem.
Last time I looked at the project details, IIRC about half of the $60 million budget was simply going toward repaving Geary Blvd, a benefit inuring almost entirely to cars. (They've postponed repavement so it could be rolled into, and hidden, by the BRT project budget.) If the BRT-specific changes were left out, the project would have been approved, finalized, contracted out, built, and finished a decade ago. The only reason it's taken so long is because of all the infighting that occurs for any infrastructure project beyond building roads.
I agree that it requires political will and good governance. Bus lanes aren’t easy most places. However, I don’t think one should ever generalize about municipalities from examples set by San Francisco.
Or even separated bus-only roads. Pittsburgh does this under the name Bus Rapid Transit.
https://en.m.wikipedia.org/wiki/Bus_rapid_transit
Edit: BRT seems to more generally refer the systems you propose!
https://en.m.wikipedia.org/wiki/Bus_rapid_transit
Edit: BRT seems to more generally refer the systems you propose!
BRT is often a higher class of service. It’s great! But there’s a lot to be said for taking a two lane street in a city and giving one of the lanes to the bus route that goes down it.
Most cities are not dense enough to support commuter trains or subways. Building them where they are not appropriate will ensure citizens will have to pay decades bailouts to keep them running.
Dedicated bus lanes in downtown areas and variable-rate tolls on highways. The tolls would probably pay for the entire build-out in a couple of years.
Dedicated bus lanes in downtown areas and variable-rate tolls on highways. The tolls would probably pay for the entire build-out in a couple of years.
It may not be sexy, but it works! I love simple solutions like this when they're actually practical. Even at partial capacity it's still a way lower carbon footprint than any normal sized personal car.
I just spent a week in Chicago - and the lack of a bus lane made buses our last choice. Traffic is terrible so bus travel is egregiously slow compared to the metro or trains. I'm used to Budapest where a bus is a great way to beat traffic.
A lot of US mass transit systems have developed existential problems due to decades of poor maintenance and under-investment. As a result they’ll take years and billions to get into a state of good repair. Bus lanes are a great way to expand capacity while that happens.
I don't think the "right of way" for tunnels is as simple and easy as the author claims. Many land rights include the soil beneath the land. While tunnels could be built below existing Federal and State owned land, many of the problems outlined for railroads by the author would happen again with acquiring the land required for tunnels.
Many of the other points in the article seem glossed over and error prone as well (e.g., simplifying the comparison between trains and trucks efficiencies to a rolling resistance coefficient and ignoring the discrepancies in weight of the vehicle an all other efficiency factors).
Many of the other points in the article seem glossed over and error prone as well (e.g., simplifying the comparison between trains and trucks efficiencies to a rolling resistance coefficient and ignoring the discrepancies in weight of the vehicle an all other efficiency factors).
You're right that property rights underground can be complicated in the US, but generally speaking the easement rights needed for underground are likely to be much easier and cheaper to acquire. Someone comes and wants to give you $5000 to tunnel under your land and you don't have to move or be disrupted in any way is a much tastier proposition than losing the family farm. That's not even counting tunneling under existing road and rail rights of way which would be even easier.
It'll take a lot more than $5000 to get my permission to tunnel under my house. I'm not sure what the number would be but $5k isn't even in the ballpark. I would be concerned about things such as vibration, structural integrity, ventilation, and potential noise through the ventilation. Probably more things if gave it much thought. Depends on how deep the tunnel is, also.
Looks 5k is just a number I pulled out of my ass. The Boring tunnels are generally deep enough that these things aren’t a concern but if it’s $x plus named protection on an insurance policy, that’s still a lot cheaper than surface rights of way.
One of the things I wish we had done in earnest was focus on tunneling more for the last century - specifically for power infra-distribution.
If we had put the effort into trenching/tunneling for power dist - we would have saved quite a lot on fires and problems caused by downed powerlines. Fires, etc...
Further, power lines are FN Ugly.
We could have had specialized machines that dig a trench, lay/build conduit/tunnel hosings and then them up at the same time.
Also, if you look at how well Singapore has done in building 'down' -- they have massive underground causeways, malls etc - and its a shame that we are too shortsighted in our cities to give up such a HUGE % of the wonderful surface of the earth for things like cars and power distribution.
Every single building built should have underground parking and access. Cars, in dense urban environments should be relegated to subterranean transit only.
If we had put the effort into trenching/tunneling for power dist - we would have saved quite a lot on fires and problems caused by downed powerlines. Fires, etc...
Further, power lines are FN Ugly.
We could have had specialized machines that dig a trench, lay/build conduit/tunnel hosings and then them up at the same time.
Also, if you look at how well Singapore has done in building 'down' -- they have massive underground causeways, malls etc - and its a shame that we are too shortsighted in our cities to give up such a HUGE % of the wonderful surface of the earth for things like cars and power distribution.
Every single building built should have underground parking and access. Cars, in dense urban environments should be relegated to subterranean transit only.
New development generally does this, as far as I've seen and read. https://www.sparkenergy.com/why-dont-more-communities-bury-p...
Retrofitting is much more expensive than original construction, though, so older US cities and developments are at a big disadvantage. So somewhere in-demand but older like California coastal cities give you the delightful result of paying more for crappier buildings and infra - because you're paying for the location, not the condition of the infra.
Retrofitting is much more expensive than original construction, though, so older US cities and developments are at a big disadvantage. So somewhere in-demand but older like California coastal cities give you the delightful result of paying more for crappier buildings and infra - because you're paying for the location, not the condition of the infra.
If there is a tunnel that moves a lot of vehicles quickly then that will generate problems at the entrance where vehicles line up to enter and at the end where vehicles exit. This may work out, but it is likely that all tunnel interfaces will, like bridges, require a complex array of interfaces to surface roadways. That adds a lot of expense and takes up a large amount of space, but there is no other way to make fast tunnels actually work to anywhere near their capacity. This implies that making fast tunnels work involves much more than the fast tunnels alone.
That's what https://www.youtube.com/watch?v=4dn6ZVpJLxs focuses on primarily. Increased capacity is completely useless if you can't get cars in and out.
and you can't.
and you can't.
I like the part of this Tesla fan fic where the author says to, just build the tunnel the size of the car no bigger.
I guess bulldozers will be the preferred first responder vehicle then.
I guess bulldozers will be the preferred first responder vehicle then.
"Source: energy.gov"? Are you trying to keep readers from checking your work? Use hyperlinks.
Okay, the Loop proposal is absolutely bonkers, so let's go over why their "benefits" aren't so:
> Make the tunnel smaller.
The actual project costs of tunnel bores for the sizes of subway tunnels run closer to linear in diameter, not quadratic as you might imagine. A lot, indeed most of them, of tunneling costs aren't about the volume of fill you're extracting.
Furthermore, there's a massive cost to making them smaller: you're now limiting the interoperability of tunnels with other infrastructure. It becomes bottlenecks that requires things like unloading cargo in a warehouse and reloading them onto different infrastructure, or suffering reduced throughput on the existing infrastructure because you don't have as much capacity in the existing infrastructure. In the US, the freight trains have basically standardized on Plate H double-stacked cargo for all their plans, and any new freight mainline will have to support that anyways.
> Use above-ground stations.
Comparing with NYC 2nd Avenue Subway is somewhat disingenuous, because this is literally the most expensive subway in the world for construction costs. And there's several reasons for this, but they can largely be summarized as "the MTA is utterly incompetent at any form of cost control and nobody, not even the political overseers, cares two whits about holding them to task for their incompetence."
We actually know how to build subways cheaply. One of the great ways to cheapen their costs is to switch to cut-and-cover for construction, especially for stations which already have to be near the surface. Of course, cut-and-cover is incredibly disruptive, but because the stations still need access to the surface anyways, you end up with much of the disruption for longer periods anyways (because you need to move materials into and out of the underground construction area, so surface access is needed throughout construction).
But this also brings up another point: vertical circulation (moving people vertically). Vertical circulation is extremely challenging to do at high volume; it's one of the biggest bottlenecks in large passenger stations today. The proposed Loop tunnels would have to be underneath existing infrastructure--in NYC, the 7 is at 60 feet below ground--and now you have to somehow get that stuff to the surface expeditiously. A car elevator? That's going to handle about one car a minute. Or you can do ramps, at say 4% grade--that requires 1500 feet of horizontal displacement. Those ramps start eating up a lot of space quickly, and you're supposed to be doing cost stations by eliminating underground infrastructure.
> Use existing electric cars as vehicles instead of specialized train rolling stock.
What a horrible idea. The capacity of a free-flowing highway lane is roughly 2,000 cars per hour, and cars are not particularly easy to get lots of people in and out of them quickly. The typical capacity of a subway line is about 24 trains per hour, with each train able to carry roughly 1,000 people or so. If you plan your subway system well (which means having limited branching, so systems like DC's and NYC's are horribly, horribly screwed), you can push that up to Moscow's 45 trains per hour. Do the math as to how many people that can carry.
Operating costs of subways are likely to be much cheaper than Loop because there's fewer moving parts. And steel-on-steel is more efficient to move on than rubber-on-pavement.
And... I could keep going on tearing down the information here, but it's really low-quality. It's based on hopes and promises of what Musk says Loop could develop, with the convenient fact that it doesn't have any demonstrations of its actual capacity (since COVID-19 means that there's not really any demand for the Las Vegas Convention Center to stress-test it). But the technologies that it is most similar (Personal Rapid Transit) that have been developed and deployed in practice haven't lived up to its hype in the past. Why should we expect this new gadgetbahn to break the model of all the previous ones?
> Make the tunnel smaller.
The actual project costs of tunnel bores for the sizes of subway tunnels run closer to linear in diameter, not quadratic as you might imagine. A lot, indeed most of them, of tunneling costs aren't about the volume of fill you're extracting.
Furthermore, there's a massive cost to making them smaller: you're now limiting the interoperability of tunnels with other infrastructure. It becomes bottlenecks that requires things like unloading cargo in a warehouse and reloading them onto different infrastructure, or suffering reduced throughput on the existing infrastructure because you don't have as much capacity in the existing infrastructure. In the US, the freight trains have basically standardized on Plate H double-stacked cargo for all their plans, and any new freight mainline will have to support that anyways.
> Use above-ground stations.
Comparing with NYC 2nd Avenue Subway is somewhat disingenuous, because this is literally the most expensive subway in the world for construction costs. And there's several reasons for this, but they can largely be summarized as "the MTA is utterly incompetent at any form of cost control and nobody, not even the political overseers, cares two whits about holding them to task for their incompetence."
We actually know how to build subways cheaply. One of the great ways to cheapen their costs is to switch to cut-and-cover for construction, especially for stations which already have to be near the surface. Of course, cut-and-cover is incredibly disruptive, but because the stations still need access to the surface anyways, you end up with much of the disruption for longer periods anyways (because you need to move materials into and out of the underground construction area, so surface access is needed throughout construction).
But this also brings up another point: vertical circulation (moving people vertically). Vertical circulation is extremely challenging to do at high volume; it's one of the biggest bottlenecks in large passenger stations today. The proposed Loop tunnels would have to be underneath existing infrastructure--in NYC, the 7 is at 60 feet below ground--and now you have to somehow get that stuff to the surface expeditiously. A car elevator? That's going to handle about one car a minute. Or you can do ramps, at say 4% grade--that requires 1500 feet of horizontal displacement. Those ramps start eating up a lot of space quickly, and you're supposed to be doing cost stations by eliminating underground infrastructure.
> Use existing electric cars as vehicles instead of specialized train rolling stock.
What a horrible idea. The capacity of a free-flowing highway lane is roughly 2,000 cars per hour, and cars are not particularly easy to get lots of people in and out of them quickly. The typical capacity of a subway line is about 24 trains per hour, with each train able to carry roughly 1,000 people or so. If you plan your subway system well (which means having limited branching, so systems like DC's and NYC's are horribly, horribly screwed), you can push that up to Moscow's 45 trains per hour. Do the math as to how many people that can carry.
Operating costs of subways are likely to be much cheaper than Loop because there's fewer moving parts. And steel-on-steel is more efficient to move on than rubber-on-pavement.
And... I could keep going on tearing down the information here, but it's really low-quality. It's based on hopes and promises of what Musk says Loop could develop, with the convenient fact that it doesn't have any demonstrations of its actual capacity (since COVID-19 means that there's not really any demand for the Las Vegas Convention Center to stress-test it). But the technologies that it is most similar (Personal Rapid Transit) that have been developed and deployed in practice haven't lived up to its hype in the past. Why should we expect this new gadgetbahn to break the model of all the previous ones?
What's up with the timestamps in this thread? The submission is from the 3rd, but shows as "3 hours ago" and comments from days ago show as "2 hours ago"? https://news.ycombinator.com/item?id=28079363
My favourite (physics) teacher in high school once told us that "you can get anywhere on this planet in 44 minutes".
The caveat being that you need to drill straight through the earth to get there and jump inside.
The caveat being that you need to drill straight through the earth to get there and jump inside.
Is it plausible to build a tunnel from China to the US through the ocean? Just a wild idea.
https://en.wikipedia.org/wiki/Transatlantic_tunnel: “The main barriers to constructing such a tunnel are cost first estimated $88–175 billion, now updated to $1 trillion-20 trillion, as well as limits of current materials science.“
China-USA would be a bit longer and go through the ring of fire (https://en.wikipedia.org/wiki/Ring_of_Fire), making it a bigger challenge to build.
I would guess a bare tunnel itself is less of a challenge than its ventilation (even if you build a parallel tunnel tube for ventilation, pumping it out over thousands of kilometers will be challenging. The alternative would be to build ventilation towers every x km) and safety (how long will it take to get an ambulance to a traffic accident? To get people out?)
China-USA would be a bit longer and go through the ring of fire (https://en.wikipedia.org/wiki/Ring_of_Fire), making it a bigger challenge to build.
I would guess a bare tunnel itself is less of a challenge than its ventilation (even if you build a parallel tunnel tube for ventilation, pumping it out over thousands of kilometers will be challenging. The alternative would be to build ventilation towers every x km) and safety (how long will it take to get an ambulance to a traffic accident? To get people out?)
A semi-bouyant tunnel that sits ~100 meters below the surface with anchors to the floor and floats above might be ideal. Imagine if it was a conveyance even for just "packets" (cargo conatiners that are shot through the tunnel, no humans...)
The next downside is whether anyone would use such a tunnel, given that plane travel would be much quicker, probably safer, maybe cheaper (tolls on such a tunnel plus gas would be quite expensive), and possibly more enjoyable (better views in a plane, it’d probably be depressing and claustrophobic being down under for so long)
I imagine it would be used for shipping primarily.
Simpler to have rail to alaska and cross the Bering Strait by various means I would guess.
I guess I am unsurprised that this started out as an interesting read and then evolved into a full-on advertisement for Elon Musk companies.
When mankind started burning Gasoline they never contemplated that burning fossil fuels would damage the atmosphere and lead to runaway warming ...
It's the law of UNINTENDED consequences.
This seems like it could be even WORSE. I fear damage to the earth in unknown ways. Let's NOT make more tunnels ...
It's the law of UNINTENDED consequences.
This seems like it could be even WORSE. I fear damage to the earth in unknown ways. Let's NOT make more tunnels ...
I work in a related industry. The article makes good points about the cost of tunneling and I think the boring company has some great ideas.
That said: * It's incorrect to think that there's nothing underground and this space is empty especially in urban areas. In Manhattan it's extremely difficult to find locations for new tunnels with the existing subway system, buildings, water supply, storm drains, power, things that aren't even on a map. Yes you could go deeper and deeper at great expense, but you still at some point need to tunnel to the surface.
* The proposal is to start the tunnel from the surface instead of from an open pit. Why are open pits needed for projects like the Purple Line in LA? Because even getting that pit built and opened is a major project, and you simply can't start it a thousand feet to the east, north, south, or west. The idea of not drilling in a pit is great if you can do it, but you can't ignore the advantages of drilling in a pit.
* Tunneling with a surface level entrance needed for cars will take more above ground infrastructure than a subway entrance. Once more, you'll need to allow cars to exit, so this will be repeated all along the tunnel. Subway stations are expensive, but the alternative is dismantling skyscrapers. It could be argued that all roads should be moved underground, Boston big-dig style, to free up space, but if you do that, you're spending lots of money on the surface as well.
* Tunnels need to stay dry and they can't make extreme angles and turns.
* Tunnels need to allow for evacuation and ventilation for the possibility of a fire. You can't get away from this with EVs.
* The "only" advantage of trains is not their low rolling resistance. The air resistance per passenger is also obviously much lower. You also reduce the amount of air and space between vehicles which increases your passenger capacity in terms of passengers per hour that can be carried in your tunnel during rush hour. Contrary to popular belief the space between cars cannot go away with FSD - the cars still need a safety margin to provide a safe braking distance from the car ahead. * In terms of safety, trains are much safer than automobiles per passenger mile traveled. It hardly even shows up in 2019 and they're only getting safer. https://injuryfacts.nsc.org/home-and-community/safety-topics...
* Trains have many downsides, but they're mostly related to being constrained to a fixed infrastructure. By putting cars in a tunnel you get many of the same downsides - freedom to change route, reverse, skip locations, avoid obstacles, etc.
In terms of future far-out infrastructure, I'd argue that "flying cars"/VTOL are a more likely solution that tunnels everywhere full of automobiles.
That said: * It's incorrect to think that there's nothing underground and this space is empty especially in urban areas. In Manhattan it's extremely difficult to find locations for new tunnels with the existing subway system, buildings, water supply, storm drains, power, things that aren't even on a map. Yes you could go deeper and deeper at great expense, but you still at some point need to tunnel to the surface.
* The proposal is to start the tunnel from the surface instead of from an open pit. Why are open pits needed for projects like the Purple Line in LA? Because even getting that pit built and opened is a major project, and you simply can't start it a thousand feet to the east, north, south, or west. The idea of not drilling in a pit is great if you can do it, but you can't ignore the advantages of drilling in a pit.
* Tunneling with a surface level entrance needed for cars will take more above ground infrastructure than a subway entrance. Once more, you'll need to allow cars to exit, so this will be repeated all along the tunnel. Subway stations are expensive, but the alternative is dismantling skyscrapers. It could be argued that all roads should be moved underground, Boston big-dig style, to free up space, but if you do that, you're spending lots of money on the surface as well.
* Tunnels need to stay dry and they can't make extreme angles and turns.
* Tunnels need to allow for evacuation and ventilation for the possibility of a fire. You can't get away from this with EVs.
* The "only" advantage of trains is not their low rolling resistance. The air resistance per passenger is also obviously much lower. You also reduce the amount of air and space between vehicles which increases your passenger capacity in terms of passengers per hour that can be carried in your tunnel during rush hour. Contrary to popular belief the space between cars cannot go away with FSD - the cars still need a safety margin to provide a safe braking distance from the car ahead. * In terms of safety, trains are much safer than automobiles per passenger mile traveled. It hardly even shows up in 2019 and they're only getting safer. https://injuryfacts.nsc.org/home-and-community/safety-topics...
* Trains have many downsides, but they're mostly related to being constrained to a fixed infrastructure. By putting cars in a tunnel you get many of the same downsides - freedom to change route, reverse, skip locations, avoid obstacles, etc.
In terms of future far-out infrastructure, I'd argue that "flying cars"/VTOL are a more likely solution that tunnels everywhere full of automobiles.
"The cost of loop stations is so cheap that you can place them next to any number of desirable locations."
This also feels wildly handwavey. You need a LOT of them if you want this to be a viable point to point network vs just a higher-risk way to build a subway. With individual vehicles going to individual stations at user request, too, we seem to have brought in "full autonomous driving" as a prereq.