4 ms·

Hits on a pet idea of mine: We have a major issue with rail transportation in the US. It's most useful in cities in a grade-separated form, but it's simultane

by mapt 11y ago

Hits on a pet idea of mine: We have a major issue with rail transportation in the US. It's most useful in cities in a grade-separated form, but it's simultaneously the hardest to build in cities in a grade-separated form. The number of existing pipelines, power lines, traffic reroutes, building permits, and private property consents required to check out grows to dizzying levels of complexity. One way to bypass this is to dig deep, deep tunnels. Tunnels far enough down that surface settling doesn't occur, tunnels far enough down to bypass skyscraper pilings. To do this well, though, you need to construct as much of each station as possible in the tube itself, and only sink shafts down to that level, not whole horizontal rooms. You can do that with a ~20m diameter TBM. You buy this monster of a machine for an exorbitant amount of money, and in exchange you get to leave the walls that it constructs in place, except for some vertical elevators and a vertical stairwell directly to the platform; No blasting, no extensive bit-by-bit excavation, no surface trenches, no access tunnels, no adjusting to separate mud and soil and rock. Just two tracks in a big tube with a bunch of space in between them, and maybe a second level for another pair with an express line.

deleted 11y ago
[deleted]
- mapt 11y ago
  Elon's hyperloop is extraordinarily different. It uses an electric hovercraft in an soft-vacuum sealed tube that is integral to the design in order to achieve high speeds for intercity travel. This is just using stock subway cars on a stock subway track with a stock compact subway station platform. Inna tunnel. In order to get a regular route travelling from inner suburb to city center to inner suburb. The only distinction from a normal subway is that it eliminates at-surface options like shallow trench-and-cover tunnelling, and near-surface concerns about subsidence, soil composition, and underground things, in favor of having the only horizontal cut being the deep tunnel, entering the Earth on one side of the city and exiting it on the other at terminal stations. Tunnel boring machines have only gotten big enough to fit both tracks and a station platform and elevators, recently, so previous deep-tube tunnelling had to do two or three single-train-diameter tunnels, and separate excavation of stations using manual techniques, which is a whole other degree of difficulty compared to digging the equivalent length of tube with the single TBM.
CPLX 11y ago
Of note, the further below the surface train stations are, the more inefficient they are, especially for daily use and commuting type lines. It takes time to get that far down in the ground from the street level. It's less of an issue for long haul transit of course, but in that case there's few stations and they can be big downtown stations anyways. As someone who grew up in Washington DC and moved to NYC, it was immediately and obviously noticeable. The ability to just hop down a few stairs and jump on a train is a major improvement to convenience. The multiple levels, elevators or long, long escalators, and so on, can double or triple the amount of minutes it takes to go 3-4 stops.
- mapt 11y ago
  We have available to us high-speed, high-capacity elevators now, standard in large buildings. The DC Metro's escalators were a lot of things, among them great big monumental architectural Statements; But as you and anyone else from the area knows, they were not particularly well thought-out (and we are still paying for that mistake in maintenance problems, wait times, expensive rain shelters, et cetera). Their progenitor, as I recall, went to the great lengths of riding them aboard a wheelchair every day in a pained attempt to prove to the planning committee that elevators, which would have spoiled his precious vaulted look, were not necessary.
  - dredmorbius 11y ago
    Elevators and the numbers of bodies you need to move with mass transit really aren't amenable. A ten-car train in an urban commuter rail system might have 40-80 passengers per car. That's up to 800 people deboarding (say, for a downtown terminal station), though generally you're looking at a low few hundred. Dumping that demand onto 3-4 escalators is doable, and the streaming is continuous. For elevators, I don't see it working. Too many people and elevators don't operate continuously as escalators do. Unless there've been tremendous advances I'm unaware of. Schindler's high-capacity elevators are rated for 6-21 people. It would take 38 elevator trips to empty the train I described above (divide among multiple shafts and/or car trips as you like, but realize that speed is 1-1.6 m/s (about 3.6 mph), or just over 60s to travel 100m, plus return and dwell time. If train service intervals were ten minutes, you'd need ten shafts assuming 3 minutes per round-trip to clear 800 passengers. http://www.schindler.com/content/pl/Internet/pl/modernizacja/_jcr_content/rightPar/downloadlist/downloadList/80_1351088438162.download.asset.80_1351088438162/SCHINDLER%205400%20(eng).pdf http://www.schindler.com/content/pl/Internet/pl/modernizacja...
TylerE 11y ago
The vast majority of american rail infrastructure is based on diesel, not electric trains, which vastly complicates tunnel constructure due to the level of ventilation required. For instance, the Cascade tunnel in eastern Washington (http://en.wikipedia.org/wiki/Cascade_Tunnel http://en.wikipedia.org/wiki/Cascade_Tunnel) can only handle ~one train per hour because they basically have to replace all the air in the tunnel every time, which takes about a half hour even with giant fans. Tunnels, especially deep ones, are also extraordinarily expensive, that's why modern rail is built on viaducts, not in tunnels, because it's just much much cheaper.
- drzaiusapelord 11y ago
  Urban light rail is almost universally electric. NYC, Chicago, DC, LA, BART, Seattle, Portland, etc. Sounds like a few places need to contemporize still, but in a lot of cities, electric has been the norm for a long time and we can trivially add more tunnels and not worry about exhaust.
  - TylerE 11y ago
    Urban light rail is such a small blip in terms of overall rail traffic that it probably barely even registers in ton/mile terms. It's like saying you could build all roads in tunnels because Tesla sells cars.
    - bobthepanda 11y ago
      Urban rail in general tends to lean more electric than diesel, especially if you go by passenger/mile. Something like 2/3s of US rail riders live in the New York metropolitan area, which runs mostly electric trains. In terms of intercity traffic, unless there is a compelling reason to tunnel it should be level or slightly raised, with the road crossings going over or under (since road vehicles are better at accelerating and decelerating when climbing or going down grades).
      - TylerE 11y ago
        Passenger traffic in general is a tiny fraction of freight. Freight drives the conversation.
Shivetya 11y ago
Here is a wonderful study on the costs of light rail and its efficiency versus other forms of mass transit. [1] Here is a telling quote about why digging deep is the wrong answer. "Seattle, however, is building an entire light- rail line underground from the University of Washington to downtown Seattle. When completed in 2016, the line is expected to cost $628 million per mile, yet it will not carry any more people per hour than San Diego’s original 1981 light-rail line that cost $17 million per mile. The total cost of the 3.1-mile subway would be enough to build almost 200 miles of elevated busways at $10 million per lane mile. Seattle’s first light-rail line, which opened in 2007, was also completely separated from streets, costing $175 million per mile (nearly $200 million per mile in today’s dollars)." [1] http://object.cato.org/sites/cato.org/files/pubs/pdf/pa750_web.pdf http://object.cato.org/sites/cato.org/files/pubs/pdf/pa750_w...
- meatysnapper 11y ago
  Seattle in all fairness has some of the most incompetent local government of all time. They couldn't govern themselves out of a crackerjack box, if their lives depended on it.
  - PhantomGremlin 11y ago
    No, Seattle is not unique. Check out the costs and delays of the 2nd Ave Subway in NYC. Closer to me, I've previously complained about the bridges across the Columbia river between Washington and Oregon. In 1982 a very fine bridge was built for $172 million.[1] What finally got scuttled in 2013 was a different proposed bridge that would have cost $2800 million.[2] Now I understand there was some intervening inflation, but there was a 16x cost increase (before inevitable cost overruns) between the two projects. Government at all levels, federal, state, municipal, is a very poor steward of Other People's Money. [1] https://en.wikipedia.org/wiki/Glenn_L._Jackson_Memorial_Bridge https://en.wikipedia.org/wiki/Glenn_L._Jackson_Memorial_Brid... [2] https://en.wikipedia.org/wiki/Columbia_River_Crossing https://en.wikipedia.org/wiki/Columbia_River_Crossing
vithlani 11y ago
The problem with you in the US, and indeed here in Australia, is not one of we-lack-technical-competence-or-ideas. The problem is a cultural and political one whereby governments would rather build in-efficient systems that allow a slow but steady trickle of tax and tolls into their coffers instead of something that will solve problems efficiently. It's not like we don't have the money. It's not like we don't have the expertise in digging holes. It's just that the general population has no idea about how to hold the political class to account for their lack of imagination and straight fraud perpetuated with tax payer money.
chrismcb 11y ago
Seattle thinks that is a great idea...

by mapt 11y ago

deleted 11y ago

[deleted]

mapt 11y ago
Elon's hyperloop is extraordinarily different. It uses an electric hovercraft in an soft-vacuum sealed tube that is integral to the design in order to achieve high speeds for intercity travel. This is just using stock subway cars on a stock subway track with a stock compact subway station platform. Inna tunnel. In order to get a regular route travelling from inner suburb to city center to inner suburb. The only distinction from a normal subway is that it eliminates at-surface options like shallow trench-and-cover tunnelling, and near-surface concerns about subsidence, soil composition, and underground things, in favor of having the only horizontal cut being the deep tunnel, entering the Earth on one side of the city and exiting it on the other at terminal stations. Tunnel boring machines have only gotten big enough to fit both tracks and a station platform and elevators, recently, so previous deep-tube tunnelling had to do two or three single-train-diameter tunnels, and separate excavation of stations using manual techniques, which is a whole other degree of difficulty compared to digging the equivalent length of tube with the single TBM.

CPLX 11y ago

Of note, the further below the surface train stations are, the more inefficient they are, especially for daily use and commuting type lines. It takes time to get that far down in the ground from the street level. It's less of an issue for long haul transit of course, but in that case there's few stations and they can be big downtown stations anyways. As someone who grew up in Washington DC and moved to NYC, it was immediately and obviously noticeable. The ability to just hop down a few stairs and jump on a train is a major improvement to convenience. The multiple levels, elevators or long, long escalators, and so on, can double or triple the amount of minutes it takes to go 3-4 stops.

mapt 11y ago
We have available to us high-speed, high-capacity elevators now, standard in large buildings. The DC Metro's escalators were a lot of things, among them great big monumental architectural Statements; But as you and anyone else from the area knows, they were not particularly well thought-out (and we are still paying for that mistake in maintenance problems, wait times, expensive rain shelters, et cetera). Their progenitor, as I recall, went to the great lengths of riding them aboard a wheelchair every day in a pained attempt to prove to the planning committee that elevators, which would have spoiled his precious vaulted look, were not necessary.
- dredmorbius 11y ago
  Elevators and the numbers of bodies you need to move with mass transit really aren't amenable. A ten-car train in an urban commuter rail system might have 40-80 passengers per car. That's up to 800 people deboarding (say, for a downtown terminal station), though generally you're looking at a low few hundred. Dumping that demand onto 3-4 escalators is doable, and the streaming is continuous. For elevators, I don't see it working. Too many people and elevators don't operate continuously as escalators do. Unless there've been tremendous advances I'm unaware of. Schindler's high-capacity elevators are rated for 6-21 people. It would take 38 elevator trips to empty the train I described above (divide among multiple shafts and/or car trips as you like, but realize that speed is 1-1.6 m/s (about 3.6 mph), or just over 60s to travel 100m, plus return and dwell time. If train service intervals were ten minutes, you'd need ten shafts assuming 3 minutes per round-trip to clear 800 passengers. http://www.schindler.com/content/pl/Internet/pl/modernizacja/_jcr_content/rightPar/downloadlist/downloadList/80_1351088438162.download.asset.80_1351088438162/SCHINDLER%205400%20(eng).pdf http://www.schindler.com/content/pl/Internet/pl/modernizacja...

TylerE 11y ago

The vast majority of american rail infrastructure is based on diesel, not electric trains, which vastly complicates tunnel constructure due to the level of ventilation required. For instance, the Cascade tunnel in eastern Washington (http://en.wikipedia.org/wiki/Cascade_Tunnel http://en.wikipedia.org/wiki/Cascade_Tunnel) can only handle ~one train per hour because they basically have to replace all the air in the tunnel every time, which takes about a half hour even with giant fans. Tunnels, especially deep ones, are also extraordinarily expensive, that's why modern rail is built on viaducts, not in tunnels, because it's just much much cheaper.

drzaiusapelord 11y ago
Urban light rail is almost universally electric. NYC, Chicago, DC, LA, BART, Seattle, Portland, etc. Sounds like a few places need to contemporize still, but in a lot of cities, electric has been the norm for a long time and we can trivially add more tunnels and not worry about exhaust.
- TylerE 11y ago
  Urban light rail is such a small blip in terms of overall rail traffic that it probably barely even registers in ton/mile terms. It's like saying you could build all roads in tunnels because Tesla sells cars.
  - bobthepanda 11y ago
    Urban rail in general tends to lean more electric than diesel, especially if you go by passenger/mile. Something like 2/3s of US rail riders live in the New York metropolitan area, which runs mostly electric trains. In terms of intercity traffic, unless there is a compelling reason to tunnel it should be level or slightly raised, with the road crossings going over or under (since road vehicles are better at accelerating and decelerating when climbing or going down grades).
    - TylerE 11y ago
      Passenger traffic in general is a tiny fraction of freight. Freight drives the conversation.

Shivetya 11y ago

Here is a wonderful study on the costs of light rail and its efficiency versus other forms of mass transit. [1] Here is a telling quote about why digging deep is the wrong answer. "Seattle, however, is building an entire light- rail line underground from the University of Washington to downtown Seattle. When completed in 2016, the line is expected to cost $628 million per mile, yet it will not carry any more people per hour than San Diego’s original 1981 light-rail line that cost $17 million per mile. The total cost of the 3.1-mile subway would be enough to build almost 200 miles of elevated busways at $10 million per lane mile. Seattle’s first light-rail line, which opened in 2007, was also completely separated from streets, costing $175 million per mile (nearly $200 million per mile in today’s dollars)." [1] http://object.cato.org/sites/cato.org/files/pubs/pdf/pa750_web.pdf http://object.cato.org/sites/cato.org/files/pubs/pdf/pa750_w...

meatysnapper 11y ago
Seattle in all fairness has some of the most incompetent local government of all time. They couldn't govern themselves out of a crackerjack box, if their lives depended on it.
- PhantomGremlin 11y ago
  No, Seattle is not unique. Check out the costs and delays of the 2nd Ave Subway in NYC. Closer to me, I've previously complained about the bridges across the Columbia river between Washington and Oregon. In 1982 a very fine bridge was built for $172 million.[1] What finally got scuttled in 2013 was a different proposed bridge that would have cost $2800 million.[2] Now I understand there was some intervening inflation, but there was a 16x cost increase (before inevitable cost overruns) between the two projects. Government at all levels, federal, state, municipal, is a very poor steward of Other People's Money. [1] https://en.wikipedia.org/wiki/Glenn_L._Jackson_Memorial_Bridge https://en.wikipedia.org/wiki/Glenn_L._Jackson_Memorial_Brid... [2] https://en.wikipedia.org/wiki/Columbia_River_Crossing https://en.wikipedia.org/wiki/Columbia_River_Crossing

vithlani 11y ago

The problem with you in the US, and indeed here in Australia, is not one of we-lack-technical-competence-or-ideas. The problem is a cultural and political one whereby governments would rather build in-efficient systems that allow a slow but steady trickle of tax and tolls into their coffers instead of something that will solve problems efficiently. It's not like we don't have the money. It's not like we don't have the expertise in digging holes. It's just that the general population has no idea about how to hold the political class to account for their lack of imagination and straight fraud perpetuated with tax payer money.

chrismcb 11y ago

Seattle thinks that is a great idea...