5 ms·

I feel like the article covers the advantages. But, most notably, the tunnel is much cheaper and faster (to build).

by issa 8y ago

apsec112 8y ago
At this stage of a project, claims like that should be regarded as pure speculation. Elon Musk is not known for rigorously meeting deadlines. But even assuming that all the claims are accurate, what good does it do to build it more quickly if you have to kill >95% of the project value?
- erikpukinskis 8y ago
  No, smaller tunnels are objectively cheaper.
  - michaelt 8y ago
    Smaller diameter tunnels mean lower cost of boring, certainly. But some of the costs of satisfying external stakeholders, like buying land; getting approval from regulators, politicians and the local community; and so on would be independent of tunnel size. IMHO the main reason not to install a conventional metro line is Musk wants to demo something going 150mph, and I've never seen a metro line going that fast.
    - jcranmer 8y ago
      > IMHO the main reason not to install a conventional metro line is Musk wants to demo something going 150mph, and I've never seen a metro line going that fast. It may seem counterintuitive, but higher speeds mean less throughput. Most metro systems are concentrated on trying to move high numbers of people, so bumping train max speeds to 150mph just makes no sense. The sweet spot for speed appears to be around 50-70mph, which most metro trains will do when they're cruising between stations. But anyways, anyone who is complaining that local mass transit ought to be going 150mph is someone who hasn't looked at why local mass transit can't go 150mph or is someone who doesn't want the "mass" in "mass transit".
- JoshCole 8y ago
  Taking the concession as a given as you requested: It's like the difference between running everything on one very beefy server versus having a horizontally scaling architecture on commodity hardware. Each have pros and cons, so its not as simple as supposing that just because one is less beefy than the other, the total value of running on a supercomputer versus a cluster is >95% value for the supercomputer relative to the cluster. If you have the goal of being able to scale to an arbitrary amount of traffic, building one very fast and expensive computer doesn't meet the traffic needs as well as building a lot of computers. A lot of things start leading to this conclusion. Economies of scale which come in when doing tons of a particular thing rather than just doing it once. Benefits of automation starting to factor in heavily for repeated projects rather than one off projects. Amortized costs of resources for repeated projects rather than one off projects. Another way you can approach understanding the differences in benefit of this project compared to a subway is by thinking about above ground transportation. Why are roads good, since we already have highways? Why are lifts at ski resorts good, when we have airports? What benefit is there to a boat, when we have cargo ships? Why have cars, when we have trains? All of these questions are intended to point toward there being some value in a cheaper solution relative to a much more expensive but less practically extensive solution. Yet another way you can understand the potential benefit relative to other transport costs is to imagine trying to optimize sign up for a site. If you reduce the number of fields in a sign-up form with the goal of making it easier to register, it is alike to reducing the cost of adding additional transport. In one case, the probability of a register increases. In the other case, the probability of a project which increases transport capacity increases. This analogy is imperfect, but I'm trying to give a analogy that technology people will understand through their experience: drive down cost, increase usage. Finally and I think this is one of the key things that needs to be understood about the proof of concept: its intended to be a first and not a last. The idea in driving down costs in tunneling is that there is an arbitrary amount of untapped transport capacity going unused beneath us. Making use of the tiniest fraction of it will only have a tiny benefit, much like making use of a single commodity computer will only have a tiny benefit. Making use of a hundred thousand tiny fractions of it will have a much more pronounced impact, much like making use of thousands of computers can have substantial benefits. You need to keep in mind the end goal, because a journey isn't its first step: one of the superhuman evaluations of a position supposes that the value of a position is the value of the expectation of where you end up, not where you are
- SideburnsOfDoom 8y ago
  > At this stage of a project, claims like that should be regarded as pure speculation. Sure. At some point it's worthwhile to actually built it in order to test the projections. And it looks like that point is now.
legolas2412 8y ago
Umm, then build the cheaper tunnel for a subway?
- txcwpalpha 8y ago
  You can't. The tunnel is cheaper because it's not for a subway. The tunnel for this 'Dugout Loop' is a simple tunnel lined with concrete and possibly some lamps for lighting. That's it. It doesn't require any of the expensive things that a subway requires like tracks, electrical systems like a third rail or overhead cable, fire suppression systems, etc. The dugout tunnels can probably also be steeper and have sharper angles, which allows more possibility for routing that a subway wouldn't be able to do (vehicles on train tracks can't go up very steep inclines or take very sharp corners). Another substantial part of this is that the Dugout Loop vehicles ascend to the surface through an elevator or ramp, which allows the station platforms to be built above ground. The platforms can also be smaller (they only need to fit a couple car-sized vehicles, not an entire train). This reduces cost substantially, as building out a large underground train platform is often one of the most expensive parts of a subway build.
  - semi-extrinsic 8y ago
    It will definitely have some sort of tracks. They've shown demos of a Model X on tracks in their demo tunnel. The project will also have to deliver on the same demands wrt. fire suppression as any other tunnel. The station building iself must be sized according to the number of people per hour, not the train length; the physical platforms that you use to step on/off trains on subways typically extend into the tunnels.
    - txcwpalpha 8y ago
      >It will definitely have some sort of tracks. They've shown demos of a Model X on tracks in their demo tunnel. The website linked specifically says that it will not have tracks. The concrete itself acts as the 'guide' for the skates without needing any type of other tracks (such as traditional metal train tracks). >The project will also have to deliver on the same demands wrt. fire suppression as any other tunnel. This is also address by the website. Fire suppression isn't needed because the tunnel is made only of concrete. There is no concern about other materials (asphalt, high-voltage electrical, etc) catching on fire. >The station building iself must be sized according to the number of people per hour, not the train length; the physical platforms that you use to step on/off trains on subways typically extend into the tunnels. I'm not sure what you mean. Train stations are definitely sized according to train lengths. In my hometown, a significant roadblock to expanding our public train system is that we started off with short trains (and short stations to match), and it is very expensive to extend the length of the stations now that we use longer trains.

I feel like the article covers the advantages. But, most notably, the tunnel is much cheaper and faster (to build).

by issa 8y ago

I feel like the article covers the advantages. But, most notably, the tunnel is much cheaper and faster (to build).

At this stage of a project, claims like that should be regarded as pure speculation. Elon Musk is not known for rigorously meeting deadlines. But even assuming that all the claims are accurate, what good does it do to build it more quickly if you have to kill >95% of the project value?

erikpukinskis 8y ago
No, smaller tunnels are objectively cheaper.
- michaelt 8y ago
  Smaller diameter tunnels mean lower cost of boring, certainly. But some of the costs of satisfying external stakeholders, like buying land; getting approval from regulators, politicians and the local community; and so on would be independent of tunnel size. IMHO the main reason not to install a conventional metro line is Musk wants to demo something going 150mph, and I've never seen a metro line going that fast.
  - jcranmer 8y ago
    > IMHO the main reason not to install a conventional metro line is Musk wants to demo something going 150mph, and I've never seen a metro line going that fast. It may seem counterintuitive, but higher speeds mean less throughput. Most metro systems are concentrated on trying to move high numbers of people, so bumping train max speeds to 150mph just makes no sense. The sweet spot for speed appears to be around 50-70mph, which most metro trains will do when they're cruising between stations. But anyways, anyone who is complaining that local mass transit ought to be going 150mph is someone who hasn't looked at why local mass transit can't go 150mph or is someone who doesn't want the "mass" in "mass transit".
JoshCole 8y ago
Taking the concession as a given as you requested: It's like the difference between running everything on one very beefy server versus having a horizontally scaling architecture on commodity hardware. Each have pros and cons, so its not as simple as supposing that just because one is less beefy than the other, the total value of running on a supercomputer versus a cluster is >95% value for the supercomputer relative to the cluster. If you have the goal of being able to scale to an arbitrary amount of traffic, building one very fast and expensive computer doesn't meet the traffic needs as well as building a lot of computers. A lot of things start leading to this conclusion. Economies of scale which come in when doing tons of a particular thing rather than just doing it once. Benefits of automation starting to factor in heavily for repeated projects rather than one off projects. Amortized costs of resources for repeated projects rather than one off projects. Another way you can approach understanding the differences in benefit of this project compared to a subway is by thinking about above ground transportation. Why are roads good, since we already have highways? Why are lifts at ski resorts good, when we have airports? What benefit is there to a boat, when we have cargo ships? Why have cars, when we have trains? All of these questions are intended to point toward there being some value in a cheaper solution relative to a much more expensive but less practically extensive solution. Yet another way you can understand the potential benefit relative to other transport costs is to imagine trying to optimize sign up for a site. If you reduce the number of fields in a sign-up form with the goal of making it easier to register, it is alike to reducing the cost of adding additional transport. In one case, the probability of a register increases. In the other case, the probability of a project which increases transport capacity increases. This analogy is imperfect, but I'm trying to give a analogy that technology people will understand through their experience: drive down cost, increase usage. Finally and I think this is one of the key things that needs to be understood about the proof of concept: its intended to be a first and not a last. The idea in driving down costs in tunneling is that there is an arbitrary amount of untapped transport capacity going unused beneath us. Making use of the tiniest fraction of it will only have a tiny benefit, much like making use of a single commodity computer will only have a tiny benefit. Making use of a hundred thousand tiny fractions of it will have a much more pronounced impact, much like making use of thousands of computers can have substantial benefits. You need to keep in mind the end goal, because a journey isn't its first step: one of the superhuman evaluations of a position supposes that the value of a position is the value of the expectation of where you end up, not where you are
SideburnsOfDoom 8y ago
> At this stage of a project, claims like that should be regarded as pure speculation. Sure. At some point it's worthwhile to actually built it in order to test the projections. And it looks like that point is now.

legolas2412 8y ago

Umm, then build the cheaper tunnel for a subway?

txcwpalpha 8y ago
You can't. The tunnel is cheaper because it's not for a subway. The tunnel for this 'Dugout Loop' is a simple tunnel lined with concrete and possibly some lamps for lighting. That's it. It doesn't require any of the expensive things that a subway requires like tracks, electrical systems like a third rail or overhead cable, fire suppression systems, etc. The dugout tunnels can probably also be steeper and have sharper angles, which allows more possibility for routing that a subway wouldn't be able to do (vehicles on train tracks can't go up very steep inclines or take very sharp corners). Another substantial part of this is that the Dugout Loop vehicles ascend to the surface through an elevator or ramp, which allows the station platforms to be built above ground. The platforms can also be smaller (they only need to fit a couple car-sized vehicles, not an entire train). This reduces cost substantially, as building out a large underground train platform is often one of the most expensive parts of a subway build.
- semi-extrinsic 8y ago
  It will definitely have some sort of tracks. They've shown demos of a Model X on tracks in their demo tunnel. The project will also have to deliver on the same demands wrt. fire suppression as any other tunnel. The station building iself must be sized according to the number of people per hour, not the train length; the physical platforms that you use to step on/off trains on subways typically extend into the tunnels.
  - txcwpalpha 8y ago
    >It will definitely have some sort of tracks. They've shown demos of a Model X on tracks in their demo tunnel. The website linked specifically says that it will not have tracks. The concrete itself acts as the 'guide' for the skates without needing any type of other tracks (such as traditional metal train tracks). >The project will also have to deliver on the same demands wrt. fire suppression as any other tunnel. This is also address by the website. Fire suppression isn't needed because the tunnel is made only of concrete. There is no concern about other materials (asphalt, high-voltage electrical, etc) catching on fire. >The station building iself must be sized according to the number of people per hour, not the train length; the physical platforms that you use to step on/off trains on subways typically extend into the tunnels. I'm not sure what you mean. Train stations are definitely sized according to train lengths. In my hometown, a significant roadblock to expanding our public train system is that we started off with short trains (and short stations to match), and it is very expensive to extend the length of the stations now that we use longer trains.