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Post by rayinla on Jun 22, 2010 15:55:10 GMT -8
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Post by Gokhan on Jun 23, 2010 10:55:00 GMT -8
I don't want to dismiss it right away but the single large tunnel with in-tunnel stations doesn't seem to make sense in comparison to the well-established conventional dual-tunnel subway with station boxes.
I think single bore would be more expensive (more tunnel cross section, deck holding the upper level in the tunnel, more underground structures) and much more incovenient for the passengers (100-ft-deep). Also, the in-tunnel stations look ugly. Stick with what is known and tried.
I wonder how much problem the methane and tar field and the fault line will impose.
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Post by James Fujita on Jun 23, 2010 13:19:54 GMT -8
ugh, I hate that deep-bore single tunnel idea.
looks like it was designed to make NIMBYs happy (less surface digging) while inconveniencing transit riders with super-deep elevator rides.
it would also kill my favorite type of TOD, the "subway station connects to a building's basement" idea. it hasn't been tried in Los Angeles yet, but it has been a hit in Tokyo.
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Post by jejozwik on Jun 23, 2010 13:23:00 GMT -8
these plans make me wonder how long a trip on the escalators would take along with the time spent waiting in line to take the escalator.
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Post by bobdavis on Jun 23, 2010 18:51:14 GMT -8
Some of the Washington DC Metro stations have escalators that must approach the Guinness Book of Records "world's longest escalator" title. Fans of musical oldies would have their mental jukeboxes playing "Working in a Coal Mine (goin' down, down)"
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Post by Justin Walker on Jun 23, 2010 19:55:36 GMT -8
Some of the Washington DC Metro stations have escalators that must approach the Guinness Book of Records "world's longest escalator" title. Some of the Washington DC Metro Red Line stations are quite the engineering feats. As you point out, the Wheaton Metro station has the longest escalators in the Western Hemisphere, with a vertical rise of 140 feet. The Forest Glen Metro station, however, is so deep (196 feet!) that it could not have escalator access; all passenger access is by high-speed elevator. Both stations were so deep that they were mined rather than built by cut-and-cover. |
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Post by trackman on Jun 23, 2010 20:03:19 GMT -8
Why is the single tunnel being studied by Metro? Is it cheaper to build? Or, faster to build? Are those known right now? Trains running atop each other at stations seems weird; how does that work? Is a larger tunnel an option that could have the trains run side by side throughout the tunnel?
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Post by wad on Jun 24, 2010 4:10:39 GMT -8
Trains running atop each other at stations seems weird; how does that work? The way the Wilshire/Vermont station works now, only without the branching. |
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Post by jeisenbe on Jun 24, 2010 6:04:06 GMT -8
Barcelona has built subways with single large-bore tunnels at low cost, but all the subways built in Madrid and Barcelona recently have been much cheaper than those in the USA and the rest of Europe. Seattle is talking about a huge single-bore tunnel to replace the Alaska Way Viaduct (Highway 99) along the waterfront. But transit advocates there are concerned that 4 billion may not be enough for the project (which is less than 2 miles long).
I would also prefer continuing with proven technology, and stations built as shallow as possible. If it takes 5 minutes to get up from the platform (say, for an elderly person or someone carrying luggage or a bike up the escalator), short trips on the subway are no faster than taking a bus.
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Post by jdrcrasher on Jun 24, 2010 6:35:14 GMT -8
it would also kill my favorite type of TOD, the "subway station connects to a building's basement" idea. it hasn't been tried in Los Angeles yet, but it has been a hit in Tokyo. That's my favorite, too. ;D And it's what should've happened to the Westin Boneventure Hotel. |
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Post by rubbertoe on Jun 24, 2010 7:28:31 GMT -8
Speaking of Barcelona, this set of pictures (really amazing, post #23) gives a pretty clear idea of how the single deep tube with multiple high speed elevators would look, and also the footprint required for the elevator shaft: www.skyscrapercity.com/showthread.php?t=1096659&page=2I suspect that there will be much debate concerning whether this would work here in LA for the Purple line extension. I guess it comes down to: 1) how much could be saved by digging a single tunnel, 2) whether the station designs can be done so that the large access shaft required can be located at each of the stations versus having a couple entrances with simple escalators, 3) the reliability of the high speed elevators over time. Metro should be watching the Barcelona system after it opens to see how it plays out. Assuming the single tunnel is much cheaper, and the elevators can work without exorbitant maintenance costs, I would think that the biggest problem with using that system in LA would be the large access shaft. RT |
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Post by metrocenter on Jun 24, 2010 8:30:04 GMT -8
My biggest concern is the elevators. The elevators in LA's Metro are frequently out-of-service. Having constantly broken elevators will not be acceptable if the elevators are the only access to the stations.
Also, if possible I would hope Metro would put the ticketing and fare gates before the elevators, to reduce the chance of the homeless setting up camp in the elevators.
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Post by Justin Walker on Jun 24, 2010 15:58:24 GMT -8
it would also kill my favorite type of TOD, the "subway station connects to a building's basement" idea. it hasn't been tried in Los Angeles yet, but it has been a hit in Tokyo. That's my favorite, too. ;D And it's what should've happened to the Westin Boneventure Hotel. You say that as if the Westin-Bonaventure-not-getting-basement-access has already happened. Last time I checked, the Regional Connector has not been built yet...  |
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Post by darrell on Jun 24, 2010 17:42:15 GMT -8
That's my favorite, too. ;D And it's what should've happened to the Westin Boneventure Hotel. You say that as if the Westin-Bonaventure-not-getting-basement-access has already happened. Last time I checked, the Regional Connector has not been built yet... Los Angeles' original subway tunnel was cut by the construction of the Bonaventure Hotel.... |
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Post by Justin Walker on Jun 24, 2010 18:14:09 GMT -8
You say that as if the Westin-Bonaventure-not-getting-basement-access has already happened. Last time I checked, the Regional Connector has not been built yet... Los Angeles' original subway tunnel was cut by the construction of the Bonaventure Hotel.... Indeed.  (It's extra unfortunate that the Regional Connector will have to be built through a portion of the old PE subway.) |
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Post by jdrcrasher on Jun 25, 2010 14:32:17 GMT -8
The belmont tunnel is what I was referring to. And as far as I know, there isn't going to be an RC station inside of the Boneventure Hotel.
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Post by Justin Walker on Jun 25, 2010 16:49:38 GMT -8
The belmont tunnel is what I was referring to. And as far as I know, there isn't going to be an RC station inside of the Boneventure Hotel. Gotcha. I assumed you were referring to the proposed 5th/Flower Regional Connector station. As currently planned, it will be built alongside the basement of the Bonaventure. I hope Metro looks closely at directly linking the station mezzanine level with both the Bonaventure and the 505 Flower underground shopping complex underneath City National Plaza.  |
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Post by jdrcrasher on Jun 26, 2010 18:20:37 GMT -8
^ Interesting. I've never seen that before.
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Post by wad on Jun 27, 2010 4:45:19 GMT -8
I hope Metro looks closely at directly linking the station mezzanine level with both the Bonaventure and the 505 Flower underground shopping complex underneath City National Plaza. The shopping center connection would be a good idea for 505 Flower. The Bonaventure, though, uses its basement for parking. Its shopping center, located within the concrete podium, is all above-ground. |
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Post by jeisenbe on Jun 27, 2010 11:07:35 GMT -8
The Bonaventure, though, uses its basement for parking. Its shopping center, located within the concrete podium, is all above-ground. A connection to the parking garage will still be advantageous for people who want to get to higher levels of the Bonaventure. With a same-level connection to the garage, it would be possible to walk right over to the main elevators and take them up to the floor you want. Otherwise, you would need to go up the escalator, exit to the street, and reenter the Bonaventure at street-level before getting to the elevator. The direct connection would save one or two minutes. |
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Post by wad on Jun 28, 2010 4:14:32 GMT -8
A connection to the parking garage will still be advantageous for people who want to get to higher levels of the Bonaventure. With a same-level connection to the garage, it would be possible to walk right over to the main elevators and take them up to the floor you want. Otherwise, you would need to go up the escalator, exit to the street, and reenter the Bonaventure at street-level before getting to the elevator. The direct connection would save one or two minutes. I don't know where the access elevator is for the basement garage of the Bonaventure, or whether there is one. The hotel elevators, the famous glass ones you see from the outside, only go to the first floor. Also, they don't provide access to the even floors of the mall. |
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Post by metrocenter on Jun 28, 2010 8:17:48 GMT -8
If a Metro rider is going to the Bonaventure, they can just as easily come to the surface on Flower Street and then enter the Bonaventure. There is no destination (like shopping) down there. Therefore, a connection to the Bonaventure's garage is all cost but no benefit. It's not like we have super-cold weather, as they have in Montreal or Stockholm, where people want to avoid the outside air.
Anyway, all of this is way off topic. The topic here is design of the Purple Line tunnels heading to Westwood. As a rider, I much prefer shallow tunnels for usability. However, if there is a significant cost savings to deep-bore tunnels, it's hard to argue against them.
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Post by rajacobs on Jun 28, 2010 10:10:29 GMT -8
Can't help but wonder if there is an earthqueake safety factor to consider associated with either a deep-bore single tube or dual-bore shallow tubes.
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Post by James Fujita on Jun 28, 2010 11:56:37 GMT -8
If a Metro rider is going to the Bonaventure, they can just as easily come to the surface on Flower Street and then enter the Bonaventure. There is no destination (like shopping) down there. Therefore, a connection to the Bonaventure's garage is all cost but no benefit. It's not like we have super-cold weather, as they have in Montreal or Stockholm, where people want to avoid the outside air. Anyway, all of this is way off topic. The topic here is design of the Purple Line tunnels heading to Westwood. As a rider, I much prefer shallow tunnels for usability. However, if there is a significant cost savings to deep-bore tunnels, it's hard to argue against them. it's not that far off-topic. the Bonaventure (and 505 Flower) is just one example of where it might be advantageous to have basement-level links from a subway tunnel to a building, and that sort of link would be much harder with a deep bore tunnel. (which I also oppose because of the elevator factor. I refuse to believe that we can build a high-speed elevator that won't break down under rush hour conditions when we can't even keep our normal elevators in operation) our subway system, such as it currently exists, lacks that sort of linkage, which is unfortunate. direct linkage gives potential subway riders a better sense that a subway line actually goes someplace. when the subway entrance is on the sidewalk or in a plaza, you don't get that same sense of connectedness. and no, we don't get the cold weather. but how about hot weather? or, in the case of Figueroa, how about all of the traffic, noise and car exhaust that you would avoid if the Regional Connector station had a direct, underground link to either the Bonaventure or 505 Flower? |
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Post by rubbertoe on Jun 28, 2010 12:00:57 GMT -8
rajacobs,
It is my understanding that in case of a large earthquake, subway tunnels are one of the safest places to be. The MTA had a chart in a recent powerpoint presentation on the purple line extension showing what recent earthquakes have done to various train systems, including subways. There was never any serious damage to subways.
AFAIK, the only consideration when tunneling is that when you tunnel directly through an earthquake fault line, you leave extra room on the sides so that any vertical and/or horizontal shearing would still allow the current tunnel to be used after some degree of repair.
RT
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