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Old May 22nd, 2007, 10:18 PM   #641
UrbanBen
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Quote:
Originally Posted by Jaxom92 View Post
There was an article in the Seattle Times this morning about the south lake union street car. (Get it here.) While it's not directly related to the light rail, there has been discussion in this thread about the streetcar. The article brings up some good points of concern about the line.

Of particular interest to me is the fact that the line will not be in it's own R.O.W. This has the potential to make, as the article said, walking just as quick and less expensive than taking the car. With Seattle weather, perhaps it might be better off, and you're not having to huff it however many blocks. Still, it does slow down the speed at which the car can travel and get stuck in the same traffic. I'm extremely disappointed that it was developed this way.

Incidentally, the statement about Tacoma's link being traffic separated is only half true. On busy Pacific avenue, the line is in the median, however once it starts running on commerce street, the traffic lanes are shared in certain places, causing delays. I've personally been on the train when there was a "snarl" between inattentive motorists and the train. Nothing serious, but the train was unable to move until the traffic cleared out.

To me, shared right of way is the worst thing to do when you're trying to maximize the competitiveness of transit versus other forms of transportation, namely the car.
You can't reduce car capacity in that corridor, or you'd never get the support to build it. But like the Portland streetcar, it'll offer an alternative that drives development. They didn't pick major thoroughfares - there'll be less mess than in downtown Tacoma.
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Old May 22nd, 2007, 10:23 PM   #642
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Interesting videos... I like elevated one better... More style than tunnel one. I don't really like the idea to build a floating light rail bridge at all. I'm no fan of floating bridges in the general. I like to see light rail suspension bridge to get built across Lake Washington. I doubt it will get built because of engeering and financial issues.
There's no "building" of a bridge to take place. The bridge is in place already; it's just a conversion.

Floating is safer in this case than suspension - in fact, the floating bridge moves less, even in inclement weather, than the skytrain suspension bridge over the Fraser River in BC. This whole "oh my god it floats!" fearmongering is baseless.
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Old May 23rd, 2007, 12:34 AM   #643
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They have not come close to averaging 50ft/day - in fact, I suspect they averaged more like 10-15ft/day. They're not digging through rock - Seattle's hills are unstable glacial till - mostly clay.

The station platforms are center - between the two tunnels. Using a double borer as shown in an earlier post would have necessitated a different and much more expensive Beacon Hill station design - as it is, they have a primary and ancillary shaft sunk between the two tunnels, making the amount of work having to be done underground (and this station is 165-180 feet down) minimal.
Like I said, based on the launch and exit time of the TBM and the distance traveled, the average was between 34 and 43 feet per day, all other things being equal. They might have piqued at 50 feet per day at one point, and they might have dipped to 115 feet per day. But the straight up average is 34-43.

I'm not so much concerned about the safety of the floating bridge. It's as safe as it has ever been, and it was tested to see if it could handle the load of trains. It is an interesting engineering problem having stationary rails that must connect to moving rails on the bridge. Having variable water levels will create the most significant movement. Perhaps this issue is where the "fear mongering" comes from - because of the challenge and the idea that a train will be on a moving structure. I have confidence in the technique, as it's been demonstrated safe in other places in the world, namely Canada. It's very creative, incidentally, but engineers are creative people.

As for reducing capacity on the street car corridor, I do no know enough about the local street politics of the route to argue yes or no. From a purely long-term technical and competitive standpoint, it's somewhat foolish. Politics makes all the difference though, as demonstrated for years in Seattle with various projects.
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Old May 23rd, 2007, 02:45 AM   #644
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Like I said, based on the launch and exit time of the TBM and the distance traveled, the average was between 34 and 43 feet per day, all other things being equal. They might have piqued at 50 feet per day at one point, and they might have dipped to 115 feet per day. But the straight up average is 34-43.

I'm not so much concerned about the safety of the floating bridge. It's as safe as it has ever been, and it was tested to see if it could handle the load of trains. It is an interesting engineering problem having stationary rails that must connect to moving rails on the bridge. Having variable water levels will create the most significant movement. Perhaps this issue is where the "fear mongering" comes from - because of the challenge and the idea that a train will be on a moving structure. I have confidence in the technique, as it's been demonstrated safe in other places in the world, namely Canada. It's very creative, incidentally, but engineers are creative people.

As for reducing capacity on the street car corridor, I do no know enough about the local street politics of the route to argue yes or no. From a purely long-term technical and competitive standpoint, it's somewhat foolish. Politics makes all the difference though, as demonstrated for years in Seattle with various projects.
I'm not sure where you're getting your numbers. TBM launch was in January of 2006, and breakthrough was in May 2007. That's over 450 days - an average of less than 10ft/day.

From a long-term technical and competitive standpoint, it's not foolish to put the streetcar on the street at all! It's not a high capacity transit system - it's a streetcar, intended to help spur development in a generally non-pedestrian-friendly area. Someone said it would be faster to walk? That's bunk. It'll be 5-10 minutes on the streetcar compared to 30-40 walking, end to end, even in poor traffic.
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Old May 23rd, 2007, 07:45 AM   #645
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2006? Ooops. I did that for 2007. What a silly mistake.

Okay, so I guess I'm seeing the streetcar with a different goal in mind.
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Old May 23rd, 2007, 08:16 AM   #646
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Quote:
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The station platforms are center - between the two tunnels. Using a double borer as shown in an earlier post would have necessitated a different and much more expensive Beacon Hill station design - as it is, they have a primary and ancillary shaft sunk between the two tunnels, making the amount of work having to be done underground (and this station is 165-180 feet down) minimal.
May I ask why you would think you need a more expensive design using a double borer?

Bear in mind that you need to enlarge the cavity at the station site to create staircases, platforms, leadways, service tunnels, and so on whatever boring machine is used.
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Old May 24th, 2007, 01:44 AM   #647
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I believe it's mainly soil conditions and the fact that they don't have to do as much work underground that would increase the cost. The tunnel alignment is also used to create as favorable conditions in these two areas while also on a politically viable station site.

But UrbanBen should probably answer, cause I don't know for sure.
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Old May 24th, 2007, 02:53 AM   #648
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Quote:
Originally Posted by UrbanBen View Post
...
From a long-term technical and competitive standpoint, it's not foolish to put the streetcar on the street at all! It's not a high capacity transit system - it's a streetcar, intended to help spur development in a generally non-pedestrian-friendly area. ...
The recent trend is to justify the expense of streetcar lines based on attracting development. There have been some recent successes; however, there have also been some failures. In Baltimore, the trains still roll past boarded-up buildings fifteen years after the light rail line opened:

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Old May 24th, 2007, 03:05 AM   #649
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Quote:
Originally Posted by UrbanBen View Post
There's no "building" of a bridge to take place. The bridge is in place already; it's just a conversion.

Floating is safer in this case than suspension - in fact, the floating bridge moves less, even in inclement weather, than the skytrain suspension bridge over the Fraser River in BC. This whole "oh my god it floats!" fearmongering is baseless.
I have read about engineering studies that examined the movement at the joints between floating bridge segments and experiments performed with lines of tractor trailer rigs. The problem of the relative motion between floating segments seems to be well understood. The main issue that appears to remain a concern is the relative movement between the floating bridge and the ramps that connect the bridge to the shore. This is where all the motion due to the change in water level of the lake must be accommodated. A couple of years ago, I remember a government official being quoted by one of the Seattle newspapers as stating that this remains a concern. I have asked about this on other forums and have received no reply. If you have any information on the studies that are being performed regarding the relative movement between the approach ramps and the floating bridge, please share.
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Old May 24th, 2007, 11:50 PM   #650
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That is very sad to see Bailtmore that hasn't boosted by developments after streetcars get installed.

By the way, this thread is supposed to focus on Seattle Light Rail System not Streetcars... We have a thread that focus on Seattle Streetcars...

http://www.skyscrapercity.com/showthread.php?t=450749
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Old May 25th, 2007, 12:16 AM   #651
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Quote:
Originally Posted by CrazyAboutCities View Post
By the way, this thread is supposed to focus on Seattle Light Rail System not Streetcars... We have a thread that focus on Seattle Streetcars...
My apologies. I didn't realize we had one especially for that and the streetcars were being discussed here at some point. I think they're related enough not to throw the topic off too much. Besides, the conversation was dying there for a bit. But yeah, it'd be good to send the streetcar discussion that way.

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Originally Posted by greg_christine View Post
I have read about engineering studies that examined the movement at the joints between floating bridge segments and experiments performed with lines of tractor trailer rigs. The problem of the relative motion between floating segments seems to be well understood. The main issue that appears to remain a concern is the relative movement between the floating bridge and the ramps that connect the bridge to the shore. This is where all the motion due to the change in water level of the lake must be accommodated. A couple of years ago, I remember a government official being quoted by one of the Seattle newspapers as stating that this remains a concern. I have asked about this on other forums and have received no reply. If you have any information on the studies that are being performed regarding the relative movement between the approach ramps and the floating bridge, please share.
I think once the November initiative is passed, the money from that will be put to use on further study on specifics of engineering the floating bridge connection. My understanding at this point is that the rail sections between the ramp to the bridge and the bridge itself (along with the land connect) will actually have two sets of rails that slide past each other as the bridge moves. The train wheels treat these two rails as one, because of the way it's designed, but it can also accommodate the movement.
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Old May 25th, 2007, 12:18 AM   #652
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Will this thing eventually link with Tacoma's LRT line?
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Old May 25th, 2007, 09:36 AM   #653
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Yes, the next package to be put before the voters includes 50 new miles of light rail part of which will link to Tacoma's Link at the Tacoma Dome Station.

A full news release can be seen here regarding the final signing by the board today of the ST2 package.
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Old May 26th, 2007, 01:26 AM   #654
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May I ask why you would think you need a more expensive design using a double borer?

Bear in mind that you need to enlarge the cavity at the station site to create staircases, platforms, leadways, service tunnels, and so on whatever boring machine is used.
I know you'd need a more expensive design. The station has two (large and small) sunk shafts between the two directional rail tunnels. The platforms were sequentially mined, from the central shaft, with a single primary entry/exit point at the surface. Here's a graphic of what's being constructed:

http://www.soundtransit.org/x1715.xml

Now, all of this has to be ADA compliant: Wheelchair accessibility is required: There must be elevators to plaform level. So if your two tunnels are together (with the platforms on the outside edge rather than an inside), you'd have two choices: Either you'd have to have elevators all the way to the surface on both sides of the tunnels, or you'd have to have some passengers transfer between two elevators (so you had only one shaft going to the surface). Both possibilities would require significantly larger and likely non-cylindrical excavation at a significant depth in poor conditions.

Separating the two tunnels at the station allows for easier transfers between one direction and the other, and much simpler and cheaper access to the surface. In addition, I suspect that having to distribute the weight of the soil above the tunnel across two tunnel diameters instead of one would reduce the overall structural integrity of the rail tunnel. That's just speculation - but the station design problems are not.
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Old May 26th, 2007, 01:29 AM   #655
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Will this thing eventually link with Tacoma's LRT line?
A transfer will be required - the systems are very different technology. Tacoma Link is just a streetcar; Central Link will probably continue farther south as a grade-separated system.
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Old May 26th, 2007, 01:30 AM   #656
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My apologies. I didn't realize we had one especially for that and the streetcars were being discussed here at some point. I think they're related enough not to throw the topic off too much. Besides, the conversation was dying there for a bit. But yeah, it'd be good to send the streetcar discussion that way.



I think once the November initiative is passed, the money from that will be put to use on further study on specifics of engineering the floating bridge connection. My understanding at this point is that the rail sections between the ramp to the bridge and the bridge itself (along with the land connect) will actually have two sets of rails that slide past each other as the bridge moves. The train wheels treat these two rails as one, because of the way it's designed, but it can also accommodate the movement.
Again: The joints between the SkyTrain bridge (and others) and the ramps leading to them move more than the joints between the I-90 bridge floating section and the fixed section. This is a non-issue - it's a strawman argument used by anti-transit groups in the area. There is a Sound Transit study to this effect. There's no new technology or research required here.
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Old May 26th, 2007, 01:33 AM   #657
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Originally Posted by greg_christine View Post
The recent trend is to justify the expense of streetcar lines based on attracting development. There have been some recent successes; however, there have also been some failures. In Baltimore, the trains still roll past boarded-up buildings fifteen years after the light rail line opened:

Baltimore isn't seeing a growth boom like Seattle and Portland have been. That's rather an apples to oranges comparison.

By the way, on that expense: A local taxing district around the line pays for it. Paul Allen owns about half the value of property in the district, and was a strong supporter. I would say that if the primary landowner paid for half of it (and the rest of the businesses involved signed off), "justifying the expense" wasn't really an issue.
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Old May 26th, 2007, 01:42 AM   #658
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A transfer will be required - the systems are very different technology. Tacoma Link is just a streetcar; Central Link will probably continue farther south as a grade-separated system.
Very Different Technology???? I thought Tacoma is light rail also...both are low-floor cars if I'm not mistaken.
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Old May 26th, 2007, 03:13 AM   #659
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Very Different Technology???? I thought Tacoma is light rail also...both are low-floor cars if I'm not mistaken.
The term "light rail" doesn't actually refer to a technology (other than implying steel wheels on steel rails) - it just refers to a general idea of capacity and service level.

There are a lot of differences between the two systems. I believe vehicle heights/clearances are different, voltages are different, and minimum turning radius is different (and vehicle length is different). Central Link vehicles could not be used on Tacoma Link.

This isn't a bad thing, they're just different systems, and were never intended to connect.
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Old May 26th, 2007, 03:20 AM   #660
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Very Different Technology???? I thought Tacoma is light rail also...both are low-floor cars if I'm not mistaken.
Indeed, Tacoma Link is called light rail, but it looks more like a streetcar. I don't think it's that different a technology. I've ridden both the Tacoma Link and "true" light rail in Portland. The only difference from a layman's point of view is scale. There are technical differences, but I don't think they're "very" different.

UrbanBen is right that there will be a transfer required because of these technical differences. I imagine that the central link extension will be put onto Puyallup Ave and therefore be only a block away from the last Tacoma Link stop. The transfer will be a breeze, so no worries on confusion at that point. Furthermore, Tacoma Link is free, so there's only a ticket purchase one way (transfer to Central Link).

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Again: The joints between the SkyTrain bridge (and others) and the ramps leading to them move more than the joints between the I-90 bridge floating section and the fixed section. This is a non-issue - it's a strawman argument used by anti-transit groups in the area. There is a Sound Transit study to this effect. There's no new technology or research required here.
I don't have a problem with it going across the bridge as long as it's well engineered and designed. I have full confidence that Sound Transit and the contractors will do so. And the precedents set in places such as Canada do inform my confidence. The only new research required is site specific to the bridge. As you say, the technology's there.
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