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Elon Musk is boring a tunnel to skirt gridlock

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Re: Elon Musk is boring a tunnel to skirt gridlock

#181

Post by lmm »

Brakenshire wrote: post #142
lmm wrote: post #110

Earlier quoted context omitted.

Right, so what we need to do is take into account value of space that roads will take up (that could otherwise be used for houses, businesses, parks...), and only build more roads if the value they produce outweighs the value they consume. That's not an induced demand issue though.

I would say that's a pretty clear example of induced demand and the problems arising from it. You build the motorway, people build low density suburbs outside the city to drive and take the motorway to commute into the centre, that delivers hundreds of thousands of cars into the centre which crashes the road-space efficiency of the central area, which damages not just the people driving into the centre, but also the…

> which crashes the road-space efficiency of the central area, which damages not just the people driving into the centre, but also the people who live close in, who are using much more efficient and scalable forms of transport.

More traffic on the central roads is induced demand, but as jessriedel said, that's likely a sign of added value. Cars from outside displacing cars from the centre should only happen when it's a net gain - the limited road space is being used by those who gain the most value from it. People who live nearby and use trains etc. are unaffected by traffic on the central roads and can live exactly as they would if the motorway hadn't been built. Cars displacing more efficient buses is a real issue, but a general one not really related to building motorways (an increase in local car traffic would cause the same issue), and can be solved with e.g. bus lanes, congestion charges...

Re: Elon Musk is boring a tunnel to skirt gridlock

#182

Post by rwhitman »

metafex wrote: post #26

This is just a wild guess, but could there be more to it than just solving traffic problems? I mean, the best solution for a permanent settlement on Mars would be underground, as to shield from radiation etc. It's a funny thought, but it would make sense to aquire experience with large earth-moving operations to improve on the technology and study the feasibility.

Ah, the underground Mars colony. It was confusing to me as to why this was so relevant to SpaceX that they'd not only take away engineering resources from other projects, but also start ripping up their parking lot to experiment.

If you want to build a radiation-shielded settlement on Mars, the best bet is to dig. But how do you dig on Mars? Just as Tesla & SpaceX solve the question of electric power in space, this project starts to solves the underground colony question...

Re: Elon Musk is boring a tunnel to skirt gridlock

#183

Post by oblio »

itp wrote: post #65
wyldfire wrote: post #52

Earlier quoted context omitted.

s/earth/dirt/ ;)

I think it'll be neat to continue to use the word "earth" as a quaint anachronism in some long distant future. A great opportunity to explain to kids that humanity was once limited to a single astronomical body... (The optimist in me is leaking out.)

Heh... Horsepower. Candela. We have a lot of precedents ;)

Re: Elon Musk is boring a tunnel to skirt gridlock

#184

Post by rwhitman »

I don't understand how he gets away with digging that big of a hole in the ground in Los Angeles County without some serious assessment and permit filing being done first. The rock is very soft and we have earthquakes here. It took decades to approve the subway line down Wilshire Blvd. I'm assuming SpaceX gets special permission to do anything it wants, but it's still very surprising that they can just start digging a giant hole in the parking lot without some opposition

Re: Elon Musk is boring a tunnel to skirt gridlock

#185

Post by saalweachter »

agumonkey wrote: post #173
cozzyd wrote: post #162

Earlier quoted context omitted.

https://en.wikipedia.org/wiki/Chicago_Tunnel_Company

Yes, but an interpolis version.

Interpolis is the worst place to start with your transportation networks.

1. We don't really have an interpolis transportation problem in most of the US. You jump on the interstate everything is fine. We've got freight rail, barges, and air freight. You only run into congestion when your poleis have grown together like between Boston and DC or around the Bay Area.

2. Your interpolis transportation networks are useless without first having an intrapolis transportation network. If your system just dumps people or packages at a depot in each city, they won't bother using it in the first place.

3. You trade the political challenges of building in the cities for the engineering challenges of building thing hundreds of miles long and the political challenges of building things that go through dozens of municipalities without benefiting any of them.

Re: Elon Musk is boring a tunnel to skirt gridlock

#187

Post by ozborn »

Can somebody who is an engineer or is familiar with the tunneling process explain why boring machines are used for tunneling rather than explosives? It seems to me the primary energy costs of tunneling are associated with converting hard earth/boulders/bedrock into rubble and then transporting that rubble out of the tunnel. Thus explosives (if properly and efficiently delivered) could deliver far more energy than a boring machine in the same time period.

What I am proposing is that instead of using a boring machine to use some kind of mobile gun platform instead. The platform would analyze with GPR the best place to fire an explosive round (through the partially cleared rubble) into the untouched earth behind it. It would then analyze the placement of the round and (depending on the ability of the round to adjust the direction of the explosive charge) detonate to increase the tunnel size. The rubble would act as a buffer to lessen the effects of the explosion inside the tunnel. Rubble could be cleared by conventional means, although electric trucks would be superior from a toxic fumes perspective. Tunnel stability would have to be handled separately.

Appreciate any feedback on where I am going wrong. I am guessing there may be cost issues with the explosive, inability for rounds from the gun to penetrate very far or accurately into the earth or safety issues with explosives that would slow things down. The latter could be dealt with though if the gun platform and trucks were self-driving.

Re: Elon Musk is boring a tunnel to skirt gridlock

#188

Post by goatforce5 »

HUSSTECH wrote: post #137
owenversteeg wrote: post #119

Ok, so one thing I've noticed reading the 120 comments in this thread and the article is that literally nobody knows anything about boring, or tunnels. Musk knows nothing, he put someone in charge who knows nothing, the reporter knows nothing, and the commenters here even admit they are completely guessing and know nothing about boring/tunnels. I definitely don't know anything about tunnels. It's a joke that came to…

I can speak somewhat for the UK, but I assume the same can be said for most of Continental Europe, Japan and China where (deep) underground tunnels for have been around for a long time. The deeper tunnels of the London Underground are "bored", that is a full circular profile is cut for the tunnel path. This is contrasted with the "cut and cover" method, which just digs a pit, builds a support structure, and covers it…

Slight tangent:

The world's first tunnel under a river was completed by Brunel in 1843 and is still in use today by Transport for London for as part of the London Overground network (ignore the confusing naming - the Overground is like the Underground, but the service operates at longer intervals).

The Wikipedia page has a lot of detail about how it was constructed:

https://en.wikipedia.org/wiki/Thames_Tunnel

Re: Elon Musk is boring a tunnel to skirt gridlock

#189

Post by sethhochberg »

HUSSTECH wrote: post #149
Nav_Panel wrote: post #140

Earlier quoted context omitted.

> I'd be interested to know if any US cities have deeper tunnels Some NYC subway stations and lines were built with boring as opposed to cut and cover. 90% of the new 2nd Avenue line, for example, is planned to be bored[1]. Here[2] is an article with more details about the tunnel boring machine used -- the comments also have a lot of good discussion. Also, Los Angeles has done some boring for its new subway lines[3].…

That 2nd Avenue line looks awesome! Also, one BIG thing the NYC subway has over on the London Underground...extensive Air Conditioning! hat-tip

Only in the handful of most recently constructed stations (like the 2nd Ave line, or the new Hudson Yards extension of the 7 line). The overwhelming majority of the station network is 80+ years old and has no climate control.

Re: Elon Musk is boring a tunnel to skirt gridlock

#190

Post by maxsilver »

elbigbad wrote: post #34
jessriedel wrote: post #31

Earlier quoted context omitted.

Induced demand often happens, but certainly not always. It just depends on latent demand and network effects. More importantly, the appearance of induced demand is not a general argument against building roads! People get value out of getting to places. If we build road B intending to relieve congestion on road A, but road A stays just as congested, we nevertheless have enabled people to get places with road B that t…

Do you happen to have any examples of where induced demand has not happened? My understanding is that it is pretty much guaranteed, especially in larger cities. I think New York's bridges and tunnels are the canonical examples of this. I say pretty much because I assume there must be cases where it didn't happen, but I am unaware of them.

> My understanding is that it is pretty much guaranteed, especially in larger cities.

Induced demand can only happen when there is a non-trivial amount of people who have and use some other option. (NYC, for example, where there is a large subway network. A new freeway might convince some subway-users to switch, inducing demand)

For a city with no alternatives (like no meaningful public transit), it's impossible to induce traffic demand, because demand is already at 100%. Traffic still grows as population grows, but a person can only physically drive one car at a time, it's currently impossible to induce any higher demand than that.

> Do you happen to have any examples of where induced demand has not happened

https://en.wikipedia.org/wiki/M-6_(Michigan_highway)

"A year after the freeway opened, traffic volumes along parallel roads like 44th, 56th and 68th streets dropped 40–50%"

That's pretty typical for proper freeway construction/expansion. It's just that we stopped doing that 20-30 years ago, but population growth hasn't stopped in the meantime, so we're way behind on our urban transit infrastructure (all of it, freeways, rails, and public transit).

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