In the latest ST3 study concept, with a one-seat ride from Ballard to the Rainier Valley, there are a total of 14 sensible transfers in Seattle: two at Sodo, between West Seattle and Rainier Valley; four at International District/Chinatown, between Redmond and either West Seattle or Rainier Valley; two at Westlake, between Ballard and Everett; and six equally appropriate at two or more of those stations, because the direction of travel through downtown is the same. In a discussion with ST spokesman Geoff Patrick and other ST staff, STB learned about some preliminary concepts for how these transfers might work.

Of course, these concepts are very preliminary. The Board hasn’t even committed to a second tunnel, much less accepted detailed transfer concepts. But they do indicate a staff thinking hard about how to avoid the transfer mistakes of the past.

Image Courtesy Sound Transit

At International District, Sound Transit would excavate a cut-and-cover station under 5th Ave S, directly east of the current station (see the figure at right). The new station mezzanine would connect directly with the northbound platform in the existing stop. From the existing southbound platform, riders would climb to the surface, decline to the northbound platform, and then work over to the Green Line mezzanine without having to cross the street.

Image by Oran
Image by Oran

This concept is miles ahead of past station designs, and significantly reduces the frustration of Sound Transit’s refusal to consider a center platform at the current ID station. Direct street access to the Green Line Mezzanine would be a nice addition. But then Oran developed a far better concept, with a tweak from me, shown at right. The beauty of this configuration is that it maximizes the ease of the most important transfers at International District, which are between East Link and either West Seattle or the Rainier Valley. I imagine a setup like this would be a substantially more complicated project, probably more expensive and with more service disruptions during construction, and I suspect Sound Transit will find a reason not to do it. But it’s worthwhile to put the optimal configuration on the record.

Although the all-surface transfer at Sodo is much more straightforward, switching Central Link to the Green Line and a new tunnel will require significant work in the busway corridor. As Geoff Patrick put it:

Subject to refinement during the environmental review and design processes, the existing tracks north of Massachusetts would be reconfigured to connect with a new alignment proceeding north to the vicinity of the current location of Stadium Station where it transitions into a new tunnel. The existing Stadium Station would be relocated to the west side of the E3 Busway and would serve the West Seattle to Everett line through the existing Downtown Seattle Transit Tunnel. All of the specifics will be subject to close review during the preliminary design and environmental review process, during which alternatives will be developed in consultation with the public, impacts will be evaluated and mitigation will be identified.

Image Courtesy Sound Transit

At Westlake, the Green Line will be traveling (roughly) North towards South Lake Union while the Blue and Red lines travel (roughly) East towards Capitol Hill.  As you can see in the figure below, the green line tunnel would pass to the  and below of the existing station. Stairs or escalators would connect the (mined) new mezzanine with either platform of the existing station. A transfer of this quality is crucial, as a decent Westlake transfer in this context fulfills the longtime wonk dream of a congestion-free transit connection between Lower Queen Anne, South Lake Union, and Capitol Hill, the informally discussed “Metro 8 Subway.”

97 Replies to “The Green Line: Downtown Seattle Transfers”

  1. Ugh. Platform transfers are horrible. Nothing like shoving your way through a crowd just to get to a staircase.

    We have these gigantic mezzanines; it’s a shame not to find a way to connect them directly!

    1. (I’m sorry, by “platform transfers” I mean “platform-to-platform transfers”. Same-platform transfers are great!)

    2. I’m very curious what the purpose of a mezzanine is in the new International District station. The current station has no mezzanine, which I consider a good thing! Just go down one flight of stairs and you’re at the platform. Why excavate a level deeper, making everyone go down an extra flight of stairs to transfer between trains or go straight to the new line from the surface?

  2. The informally discussed “Metro 8 Subway.” did not stop at the Capitol Hill Station. It kept going to First Hill and the Central District, thus connecting the largest contiguous high density area in Washington State. I really don’t know anyone who thought a subway would only serve the western end. I don’t think anyone who promoted the WSTT ever thought it was a “Metro 8 subway” even though it serves the same area (and then some) as this subway.

    By referring repeatedly to a couple stops west of Capitol Hill as the “Metro 8 subway” you imply that there will never be a Metro 8 subway. This implies that the Central Area and First Hill will never receive adequate service from Sound Transit, while far less urban and far less important areas receive billions in infrastructure.

    1. If we move the downtown Madison St stop to the East Side of I-5, we can do a lot to correct the mistakes of ST-2.

      Eventually we will also have to find a way to correct the lack of a north Capitol Hill Stop, but that will require a 2nd line.

      1. Yes, I agree. Before the WSTT article was published in the Seattle Times, the folks doing the writing ran it by me and a few other people who regularly comment on this blog (or know a thing or two about transit). A guy who goes by “d.p.” suggested exactly that (a station up the hill on Madison). I think that would add considerably to the cost, and was not considered for the article because the WSTT was based on research done by Sound Transit (and they haven’t researched that option).

        Even if that was added, at some point it would makes sense to cover the area between Madison and I-90 with high speed rail. The gap as it currently exists is huge and means that just about everyone in the area has to go downtown to access Link (while Link itself is primarily focused on getting people downtown). A stop up on Madison would help immensely, but still leave a pretty big gap. Judkins Park will help to a certain extent, but another subway should leverage that stop, instead of the region being dependent on it.

      2. @RossB Eventually we’ll need something like Seattle Subway’s Yellow line (and an Aurora line).

        If We could manage to get LQA-SLU-Westlake-First Hill alignment in the first round though, it would go a long way to unclogging our transportation mess.

        Add in a UW-Ballard line and we might even want to consider just running the eventual aurora line through the East Side of Capitol Hill instead of downtown… as long as it connects on the hill, a third downtown line would seem unnecessary.

      3. You really should not deprive Green Line riders of their Financial District stop. While there may be some validity to an argument that mid-day and evening riders would find more value in a stop somewhere around Eighth Avenue on First Hill, peak hour ridership is the reason that a new tunnel is needed at all.

        While it’s reasonable to force a transfer to the Red/Blue line for Ballard riders at Westlake, the clumsy in-direction transfer at IDS — in either the ST proposal or Oran’s — would make Southend to Financial District trips quite unpleasant. Now perhaps you would argue that riders living in the Rainier Valley and South King County are not likely to be bound for the Financial District, and demographically that is probably true to some degree. But do remember that a Green Line tunnel under Fifth would have the better connection to Madison BRT.

        Another issue is that the diagram shows the tracks of the Green Line as being “one story” deeper than those of the Red/Blue at IDS if ST’s design is adopted. That means a railhead elevation of perhaps 10 to 15 feet below MSL. Starting from that elevation and rising to a reasonable station depth at Fifth and Madison is going to be a pretty steep grade in and of itself. Adding the additional two hundred feet or so to Eighth would mean that the station there would have to be quite deep, requiring several banks of “folded” escalators to fit within a reasonable station footprint.

      4. I was assuming a transfer for everyone headed to the financial district (as you call it). As far as connecting to BRT, both stops would work (since Madison BRT will go along all of Madison).

        Good point about depth, that would add to the cost and make it even more time consuming to reach the surface.

      5. I’m not sure if an Aurora line will ever be necessary. The key is to simply remove the congestion. Vancouver has a bus line that carries 55,000 people a day (or more than Link). An Aurora light rail wouldn’t carry that.

        Now, it may be that the only way to eliminate the congestion is to build on top of Aurora. Elevated rail (presumably) at that point makes sense (BRT experts can chime in and correct me). But in terms of volume and leveraging the existing infrastructure, then BRT (Gold BRT, not the Rapid Ride crap along that corridor we have now) is probably the way to go.

        But the Central Area doesn’t have anything to leverage, nor does Ballard to UW. Center running, taking lanes and all that will only get you so far because you have lots and lots of intersections. Intersections, by the way, that have major traffic flows the other direction (unlike Rainier Valley).

        Oh, and Seattle Subway’s Yellow line is flawed for a couple reasons. First it is ridiculous to add a second line to the airport. Second, it is too true to the current routing. I really can’t criticize them that much for that flaw, though. It is tough to go into much detail on that map when it extends from Everett to Tacoma. Their routing is presumably rather vague in the area. Besides, skipping First Hill and following the Metro 8 to the letter would still be much better than most of what Sound Transit is considering for ST3.

    2. Ross,

      First Hill already got its “Sound Transit Coaster” service; it will be opening any time now…..

      With the enormous increase in property taxes which will follow the opening of the new towers going up throughout downtown, Belltown and SLU, the city should be able to build the Metro 8 itself and should contract with ST for engineering and construction, but not design.

      1. Seattle could and would build its own light rail system but the state won’t let it.

        I’m not sure what a coaster is in this context. It that like a bus, only slower, less frequent, and with less capacity?

      2. The “coaster” is being unpowered on the descending run.

        I cannot believe that an Eighth Avenue (or farther east) station would be worth sacrificing direct access to the office core.

        Obviously that’s a minority opinion.

        But I really fail to see what enormous volume of now driving potential riders exists between either Ballard and First Hill or the RV/South King County and First Hill.

      3. Do you really think that the transfer at Westlake is that onerous? If you have the station at First Hill and connection points at Westlake, I. D., and Sodo, then you connect the entire network to First Hill. That means folks from Rainier Valley, the south end, the east side, South Lake Union, Uptown and Ballard all can get there. Even people from the UW and points north may prefer that transfer over the surface route.

        If that transfer really is horrible, then can’t you say the same thing about South Lake Union? That has been suggested by many as one of the big selling points (finally — a way to get to South Lake Union!). But if the transfer is bad enough that you are willing to walk up a steep hill (to First Hill) then it is certainly bad enough to walk across flat land (to get to South Lake Union). Meanwhile, South Lake Union will get the same sort of high end, high frequency (and we hope — very fast) service from a Link station that Madison will get. But if you think that this South Lake Union stop will only be used by folks from Ballard, RV/South King County, then it certainly limits its value.

        I’m not saying it is worth the money to serve First Hill in that manner, necessarily, but it is worth looking into. Transfers are a key part of a light rail system. To build a completely redundant line simply because you want to give some people a one stop ride to a particular area is very silly (which is why the new line won’t have the same stops, despite the fact that all the stops are certainly warranted).

      4. Ross – Based on what I know now, I’m opposed to building the line through First Hill. I-5 undercrossings are expensive, the elevation change is disturbing, and the routing would be far longer. I’d want to serve First Hill on a future line that doesn’t need to loop back to downtown on both ends.

        However – sure, I’m not opposed to studying the issue. Maybe my guesses will be proven wrong.

      5. If there could be a high pedestrian skyway from Harborview Park over I-5 to city or county property between 5th and 6th Avenue, combined with elevators or maybe a set of escalators that could provide an elevation change to below the street …


        If the Madison Station mezzanine went further south to Columbia Street to link with this shaft…


        At least the Harborview/First Hill area could have a pretty sweet connection to rail.

        Is that an option?

        I know it doesn’t serve the CD, but I’ve observed that the Harborview complex seems to be the major trip attractor in this area, and this connectivity could also benefit Yesler Terrace.

      6. I think the elevation change and i-5 are exactly why you want to do it. These are real barriers that cut off first hill from downtown. A bored subway requires an escalator or elevator anyway, so we’re really talking about a marginal cost to extend them a bit in a place where they’re particularly valuable. The hills almost turn the city into an archipelago and mined tunnels may be the only way to connect the islands in a meaningful way.

  3. I think that for this whole project, tunnels and stations alike, biggest design consideration will not be ” facts on the ground”so much as “facts under the ground.”

    The chief reason for most of the complications in the Downtown Seattle Transit Tunnel- including the lack of center platforms, was due to the fact that we had to work with the space and complexity of either a dental inlay or a root canal.

    Pittsburgh had the same problem, probably the reason so much of our design team came off their system. On the surface, they’d been doing joint-use transit ways for years, built on old freight lines, of which they have many.

    Look at maps from 100 years ago. Jackson Street used to be the north shore of a lagoon. The ground is really water with some dirt in it. Just across Jackson, we had to pump cement into the ground for months until we could start boring.

    All the way up Third Avenue, we’ve got utilities and building foundations to deal with. The BN tunnel swings northwest toward the Waterfront. The machines suddenly encountered an underground creek at Century Square.

    This is not to say “don’t do” or “can’t do.” But I think meaningful discussion needs to start with a look at the soils and utility maps from DSTT design engineering.

    If the late Monorail project ever got that far, some good soil and hydrology studies might pay back a lot of damage to transit finance and reputation.

    And our engineering team needs people from both Switzerland and New York City. Can anybody else think of places with some serious underground complications?

    Mark Dublin

      1. Charles, there are probably thousands of underground transit miles around the world.

        But Japanese engineers could doubtless quickly find some specific conditions here that they never had to contend with.

        Because of our extremely crowded space, for starters, this could be one of the world’s hardest. I’m surprised that the December 5 post, and its subject received so little attention.

        Today’s STB readers will be very proud to have been involved in transit here when that red, blue, and green map came out. In these pages.

        Word “lifetime” come to mind. For more than one of our own generations.


  4. Thanks for putting out this concept!

    One major tweak I would like to see studied is having the red/blue line moved to the new tunnel, which will be able to deal with higher throughput, not just because of wider stop spacing, but also because the new stations can be built in a way that takes advantage of all-door boarding and alighting.Yes, I realize this could require a lot of re-work at Westlake, but it should push out the time it takes Link to reach peak capacity by decades.

    1. Absolutely impossible. What you call “a lot of work at Westlake” would involve changing track levels by at least thirty-five feet.

  5. Any reason why Sound Transit has such poor images? They are really tiny (e. g. 227 × 139) and the font is fuzzy. In contrast, Oran’s image is outstanding and very easy to read.

    1. Agreed, these look like screenshots of thumbnails, blown up.

      Clearly there are originals somewhere…

    2. I’d bet it’s pixel vs. vector art. Someone took a low-res screenshot or exported a png or jpeg rather than sticking with a vector based format. (and I’d bet Charles B is right – it’s a blown up thumbnail rather than the original file)

      1. Yeah, not that I necessarily need to see a PDF. I’m not trying to print the thing. Just convert it to decent (high res) jpeg or png (instead of this really low res png). I agree, someone probably did a scan (and a poor one at that).

  6. Oran’s layout is reasonable! I wonder if shifting the platform a bit south would make it easier or harder.

    ST is not adverse to buying adjacent buildings, like they have done with Capitol Hill Station. There are times when that is cheaper than building track. Whatever gets considered should have connectivity as its main objective.

    1. Could it work without a Westlake like mezzanine, though? It took me a few minutes to figure out the diagram, so I’d imagine the average person would need a lot of way finding.

  7. there should be a connection between the East Link tracks and the Green Line as well … that would allow for future system flexibility and allow both lines to have service to the East Side (maybe Green Line connection to Issaquah)

    It’s important to note that there is actually a lot of space in the current bus layover portion of IDS + IDS Station + the space between the platforms and the tunnels to the north

    1. Building this would be strategic, especially if the switching can be designed quickly and implemented with East Link as a change order. Westound Eastlink connections to the northbound new tunnel would seem to be particularly easy for non-revenue access. If it is done by 2023, the disruption to revenue service won’t be required.

  8. also it is a bad idea to have one line running backwards like Japan (running on the left) compared to every other system in the US (and station in Seattle) …

    Northbound Green line should be on the right of the illustration and southbound on the left.

    1. Concur. I hadn’t noticed that in the diagram.

      Making that switch would put both northbound tracks accessible by plateform 3 and both southbound tracks accessible by platform 1. Not a bad concept.

      Still have to find a way to incorporate holding tracks somehow. But there must be a way.

      1. Maybe delete Platform 2 and put a holding track in its place? You’d still be able to board both northbound tracks from Platform 1, and both southbound tracks from Platform 3.

    2. If the NB Green Line is on the east side it messes up the cross-platform transfer. It must be adjacent to SB blue/red.

      1. @Martin,

        Na, that is far from clear. Probably the dominant transfer will be NB Green to NB blue/red and vice a versa. So having the NB and SB lines clustered should work well

      2. +1 to Lazarus. There’re definitely going to be some NB/SB transfers, but they won’t be the dominant direction at all. (It’ll be different at Westlake.)

      3. The transfers you describe can be done at Sodo or Westlake if they’re not prioritized here. These have to be done at Chinatown.

      4. @William C,

        It hadn’t occurred to me, but the other reason to group NB and SB lines together is that it greatly simplifies the holding track design. One holding track located south of the stadium can now feed all the NB red/green/blue lines. This is a great simplification.

        The holding track feeding the SB lines is a bit more complicated. I’m not sure of the geometry in the area, but it might be necessary to split the holding tracks.. Obviously the holding track feeding the SB Green line could be located adjacent and to the west of the active track, but the holding track feeding the SB red/blue is still an issue that would require some thought.

      5. @Martin,

        Yes, of course these transfers could also be done elsewhere in the system, but as configured by Oran the new IDS really becomes the key transfer station in the system – care should be taken to get it right.

        As drawn, with the NB green line on the far west, the configuration of the green line really represents poor engineering. Nobody in this country would expect the NB line to be to the far west and the SB line to be to the far east. Additionally the alternating of directions is just plain confusing and unnecessary.

        Additionally having the NB green line on the west and the SB green line on the east will necessitate some tricky engineering. The NB green line already has to dive quickly to pass under the existing DSTT tunnels while avoiding the BNSF tunnel to the west, but now it will also have to dive under its own green line SB line to get back to American style right hand running for the rest of the system. Such underground braiding of N and S bound lines is possible, but why do it

        The situation for the SB lines is worse. Somehow the SB green line will need to get from the eastern most lane to the western most line, and will have to do it quickly because it theoretically shares the Stadium Station with the west Seattle line. Diamonds are operationally non-starters, so an overpass or underpass is required. Do we want to go there? I think not.

        Keep it simple, keep it understandable, keep it functional, cluster the NB and SB lanes.

        But there still needs to be a solution to the SB holding track issue that doesn’t affect the station. That is the hard part.

      6. My idea was inspired by the cross platform interchanges in Hong Kong’s MTR system. So the way I drew it originally facilitated transfers between the N and S legs of the spine, so one going south from Northgate or Ballard can continue to the Airport or West Seattle (and vice versa) with a same platform transfer. There are a few ways such a transfer could be configured. Of course, the Hong Kong example actually stacks the platforms instead of placing them side by side which likely simplifies the tunnel work but I don’t know if that’s an option for IDS. Also, Hong Kong pairs two similarly configured stations to enable easy interchange in all directions instead of trying to cram it into a single station.

        Martin wanted to use a similar arrangement to facilitate transfers from the Eastside. His original suggestion was to run the SB Green on the far west side and NB Green on the far east side of the station but in order to make that work, the DSTT tracks would have to cross over themselves entering and exiting the station, which is impossible. So I suggested reversing the order of the tracks to fix that but that meant the line was running the wrong way.

        Under ST’s proposal, the Green Line tunnels start at Green Line Stadium Station, which is separate from the Red/Blue Line Stadium Station. I feel that it is easier to do such crisscrossing of tracks underground than overground for some reason.

        If the direction is swapped to pair N and S tracks, then that cross over requirement goes away and the southern approach to IDS is treated like a super wide island platform.

        As for the northern approach of the Green Line tunnels, the DSTT dives down leaving IDS at a steep 5.4% grade, curving toward 3rd Ave and reaching its lowest point under 4th & Washington about 750 feet from the portal in IDS (near the BNSF tunnel). Depending on whether it is possible to bore a tunnel under existing buildings directly north of IDS, you would not make the western Green Line tunnel dive under the DSTT. Instead it would parallel it for about 400′ until there’s enough clearance for it to go over the DSTT, around Main St, completely avoiding the BNSF tunnel. The eastern Green Line tunnel has no issues as it would be built under 5th Ave.

        The key question is what transfers do we want to make really easy? N/S is an obvious one, which is why I went with that first to mitigate the splitting of the spine.

      7. In all honesty I do not see why there is any need for a “southbound holding track” on the Red Line. The line goes five stations beyond IDS; when will four car trains on such a short line be overloaded?

      8. @Orin,

        The only time any tracks have to cross over themselves is if you try to force alternating N and S bound tracks.

        As you have drawn it the existing DSTT tracks don’t need to cross over themselves, but the GreenLine tracks certainly would. After all how would you expect to get the NB green line on the west side of the station when everywhere else on the line it is on the other side?

        Additionally, since the red and green lines are interlined at Stadium station this crossing over of the GreenLine would need to happen quickly as you just can’t mix RH and LH running lines at the same interlined station.

        All this mess is avoided if you keep the SB GreenLine to the west and the NB to the east. Yes, someone going from Columbia City to Microsoft would need to change platforms to transfer, but someone is going to need to do such a transfer regardless of how the station is configured. The best approach is to design a station that works for everyone instead of designing it around our own favorite commutes.

        Regarding the west most GreenLine track crossing over the existing DSTT tracks – good point. This really simplifies things in this area. Unfortunately your drawing shows it going under, which I think is the source of the confusion.

      9. Lazarus, I was referring to my original sketch and intermediate sketches on Twitter, not the final one you see in the post. But you’re right that simply swapping the SB and NB Green Line tracks would simplify things greatly at the expense of Eastside to Southend trips. My original sketch attempted to make at least one way of that trip same platform while accommodating the N/S flow but due to the crossing tracks, it is less constructible.

        Where are you reading that Stadium station will be interlined i.e. Red/Blue/Green sharing same tracks and platforms? From the ST3 sheets, it looks like they’re building new tracks on the Busway parallel to existing Link with an at grade Stadium station and an elevated SODO station. ST on its blog mentions transfers at the “surface level” SODO station.

      10. @Orin,

        I was assuming that red and green would be interlined south of IDS sEnse and have the lowest construction costs. Track on existing ROW and simple stations might be cheaper than the alternative, but they still aren’t cheap.

        The reason ST might take the E3 busway and run 2 pairs of side by side non-interlined tracks is that it solves their cross over problem. They are intending to run both directions of the GreenLine to the east and both directions of the RedLine to the west, thus they don’t need a crossover.

        Your method with the SB GreenLine on the west solves this problem by putting s single tunneled crossover north of IDS. South of the IDS the red and green could be interlined at some cost savings, and with retention of the E3 for buses (if that is still useful).

        However, the disadvantage of interlining the green and red south of IDS is that it ties all the lines together operationally. With red and green interlined south of IDS, and with red and blue interlined north of IDS, it becomes sort of tricky operationally.

  9. Oran’s ID Station concept is great. The all center platform configuration is much better than side platform configs, and the fact that LRV’s using tracks 2 and 3 have all door boarding is a bonus.

    Construction cost and complication is of coarse an issue, but the big problem is that it doesn’t address the reason that ST stated for not considering a center platform at IDS. ST claims they need a holding track at IDS to feed the lines going south and east.

    Whether that problem is solvable with Oran’s configs I don’t know, but it is worthy of more thought.

    Good job Oran.

    1. Hat holding track is probably to reverse trains, since they don’t show a direct south to east connection.

      Portland decided to install a through track for getting trains to the yellow line. Then again, there are several through routed yellow to blue line trains each day so it works better that way.

      1. I certainly hope that as plans develop there are provisions for through-routing North Link trains to the Rainier/Sea-Tac line, perhaps as a Northgate or 145th-Airport line. Otherwise, for anyone not living within walking distance to one of the scattered stations in NE Seattle (and north), getting to the airport becomes a three-seat ride. Absolutely nobody is going to do that. The airport is a major regional destination and employer and should not be cut off from a large area of the city that, until the ST3 lines are built, will already have direct service.

  10. It’s telling how ST defaults to side platforms in its IDS transfer diagram. Basic subway design usually defaults to center platforms. It cuts the costs of escalators and elevators down as well as increases directional platform capacity (overflow space in the off-peak direction).

    I also don’t get why there is an extra mezzanine at Westlake. Simply extending the current mezzanine to have longer shafts to the next platform would be all that is needed, with a second connection between the two lines’ platforms. It’s a 50-foot overkill vault of a station!

    I don’t have much confidence in ST in-house staff that they understand generic subway design.

    1. Either I’m not understanding your idea, or one of us has a bad picture of the track design. One story below the current mezzanine, the Red/Blue Line is going east-west. So, the Green Line has to be two stories below the current mezzanine (or else on the same story as the mezzanine… but ST didn’t consider that idea.) Either you’ll need a two-story escalator and stairs, or a second mezzanine at the same level as the Red/Blue Line.

      1. I think we are on the same page, William. All I’m suggesting is an extension of the existing mezzanine to only a track level station platform. The green line station is already deep and this would make it even deeper. Add to that a Bertha-sized station cavern and it seems overkill. All of this would get assessed in value engineering so maybe ST is starting with the most expensive station construction option so that they can say that they saved money later.

      2. Okay, I looked at the diagram again, and I’m totally wrong about what ST is actually planning. You’re right; their plan is wrong and should be changed.

    2. If you look closely at ST’s Westlake diagram it becomes clear that the Green Line track would be under Sixth Avenue. The existing platforms at Westlake extend from a bit west of Fourth to mid-block between Fifth and Sixth Avenues. That’s probably to facilitate the curve to Westlake Avenue.

      If the tracks could be under Fifth your proposal for direct access from the existing Mezzanine might be possible, but it doesn’t reach to Sixth so there would need to be a new north-south one for that line. That makes direct Red/Blue platform-to-Green mezzanine transfers possible with just a moderate change in elevation.

      1. A level pedestrian tunnel south of the current tracks to Sixth (not a full mezzanine extension) is only a short distance. Once over a center platform, escalators and elevators can be added. There is no need for a second green line mezzanine.

      2. For whatever reason it seems that ST is planning for a pretty deep tunnel at Pine. It’s not clear why that is necessary to underrun the existing trackage, but there must be some reason for placing them so deep. Using the passages only design you outlined would indeed be much less expensive.

  11. I like the concept a lot, but we already see two people saying that northbound has to be on the right.

    The alternative is to use ST’s layout, but put in the still needed center platform at ID station.

    Until ST acknowledges that the center platform is required, suspect we’re just proposing things to be ignored.

    Example of the vast quantity of space that has no room for center platform or Spanish solution.

    The existing side platforms need to go. The elevators and stairs protrude into the platform area in a way that wastes a ton of width, and makes it an uncomfortable space late at night.

    1. It would be nice to see ST recognize the advantage of staying below ground by adding an underpass to the southbound Red/Blue platform to their diagram. It would have to be mined, but they’ll probably be mining the passageway between the existing northbound platform and the new station anyway.

  12. I feel like ST’s Westlake diagram leaves something to be desired in terms of actually getting to the surface. You already have to go up 2-3 (depending on how you count) flights of stairs to get to the surface from the current tunnel. This diagram would have you take 5 from the new green line.

    Is there no clearance between the DSTT and the foundations above it?

    1. I doubt there are any foundations above it. It basically exists within the right-of-way of Pine including the sidewalks.

  13. The problem with Oran’s design is that the westernmost track (shown as Rainier Valley to Ballard) would have to dive very quickly to pass under the existing tracks before they start to dive themselves to pass under the BNSF tracks. It’s probably not geometrically possible.

      1. I think that would run afoul of the foundations of both of the buildings directly north of IDS

      2. That might work, depending on how far east of the BNSF tunnel wall the DSTT tubes reach the underrunning depth. Obviously I don’t know where that is, but I’d bet they didn’t make the grade any steeper than necessary to get that 4.5 feet right at the wall (projected downward of course).

        Better than having them side by side at the same level as you suggest OR side-by-side at different levels as ST suggests would be to have new side platforms directly below the existing ones. I know, I know, “center platforms are better”.

        But center platforms for the Red/Blue at IDS have been embargoed by ST.

        However, it just occurred to me that nobody has asked why if the Green Line is to be the “connection to the RV, Airport and South King County” the Red/Blue still needs layover trackage at IDS. Surely there will be no four station “extras” to West Seattle after football games. Any layover capacity will need to be northbound from somewhere south of SoDo,

      3. I didn’t finish the previous post. So, IF the reason for layover capacity at IDS is in fact specials for football and soccer games southbound on the Rainier Valley line then a center platform becomes possible for IDS — somebody just needs to remind ST that they’ve changed their story and it no longer adds up — so the Red/Blue could have Spanish platforms and directly under the center platform the Green Line platform could facilitate transfers between either direction on that line to either direction on the Red/Blue.

        The track level would need to be no deeper than shown in the ST diagram, Now there might be some usability degradation of IDS during construction because the existing tracks would have to be on a Market Street style structure as the tracks were during the BART/Muni Metro tunnel construction,

        It’s a bit ugly but it works.

        And it would require making the “Mezzanine” at ground level the full width of the station to access the center platforms.

        The escalators would need careful thought because the loads from the center platform would be heavy, Red/Blue riders who aren’t transferring could be urged to use the side platforms.

  14. And include an underground passageway from this ID superstation under King Street (roughly) to connect to King Street Station, Sounder, Amtrak, Union Station and Pioneer Square.

  15. Any route under 5th Avenue is going to greatly impact the Monorail columns at Westlake as they are located in the 5th Avenue ROW. This would also be a good opportunity to think how the monorail can be a greater part of the downtown transit system and how it would tie into the Westlake superstation with its tracks needing to be rebuilt from McGraw Square to Pine again (this time remove the pinch point). Having the monorail accept ORCA will be the first big step in transforming its role to be less tourist-only and that’s happening soon.

    I like the idea of extending the monorail to the Queen Anne Link station for a transfer point there and adding an infill station to serve Belltown on the existing tracks, since Belltown is being skipped for Link to Ballard, something like this… Westlake-Belltown-SeattleCenter-QueenAnne. A QA-Downtown shuttle.

    1. probably would have minimal impact … tunnel will be deep enough and monorail support column foundations are only 25 feet deep, on one side of a 5 lane avenue

  16. the real bugaboo in this whole plan … is the turn back track planned for the middle of IDS

    However, if they’re going to mine a new station to the east of IDS … why not instead mine it UNDER IDS … which would allow for equally convenient cross-line transfers


    this would also create an underpass for the existing side platforms of the RED/BLUE line at IDS

    1. Gordon,

      See my post above. That “turnback track” is NO LONGER NEEDED! The Red Line will have only five stations at the most so it’s not going to need “special service” after football games. There seems to be no reason at all that East Link would need to turn back at IDS. So they don’t need the track!

  17. I think that Seattle Transit Blog has earned itself a place in transit history when the last key clicked to post the red, blue, and green schematic.

    I also wonder who exactly, probably more than one name and agency, actually created this plan. Which is a good thing. The less huge efforts get launched with major bragging, the better their chances.

    For the working life of whole present STB readership, our job will be the hardest and least-recognized: keeping passengers moving during a lifetime of construction.

    We’re going to have to set up a whole succession of transit systems while the main one is getting built. With strong chance which one is main will change.

    DSTT? Sandbox by comparison, cats and all. But:
    The SF MUNI got a light rail subway out of BART. We’re in line for some high speed regional transit too.

    Whose bore could also handle an LRT tunnel, green or whatever. Meantime, the sweaty thankless careers ahead entitle us to three things.

    1. Only one damned Agency building and operating the whole system. Work doesn’t start till we have one.

    2. A permanent labor-management employee advisory group working with project engineers.

    And 3. At every public meeting, every single Event Planner replaced with a project engineer. Likely same arguments and conflicts- but less power-point and much better informed arguments.

    Mark Dublin

  18. On my tiny laptop screen, I can’t make out any details on the ST images. My question:

    If someone is traveling between Northgate/UW and the airport with suitcases, would their best transit point be Westlake, International District or SODO? The ID diagram seems to involve multiple staircases, not sure about Westlake. This would also apply to people with disabilities or families with young children who might have a strong preference for a level transfer or ramps over elevators.

    Counterintuitively, SODO seems like the easiest transfer since it’s on the surface. But that would mean doubling wait time since you’d have to wait for a Red line train over a Blue line train. Though if the trains are every 6 minutes, skipping a Blue train wouldn’t be a big deal.

  19. The STB concept is ambitious but I see some flaws with it. One is what others have noted in that the westernmost line would have to duck to get underneath the existing DSTT tracks and while I don’t know the grade I’d be willing to be asking the new tunnel to is likely too much not to mention the grades between that and the proposed Madison St location. Secondly though is the crisscrossing you’re asking all the lines to do to get to Stadium Station out of the tunnel. That’s just bad engineering. I would however add a ped tunnel beneath IDS connecting the west platform to keep all transfers internal to the station.

    1. @lowkey,

      There is no “crisscrossing” of lines south of the ID Station. The East Link lines climb up on the existing bus ramps and cross over the other lines on preexisting overpasses. This is no different than ST’s current plan. So no operational complications at all south of the station – each line has its own uninterrupted ROW

  20. Martin, one really important thing I may have missed: What’s the time-frame we’re talking about here? Does anyone have any idea at all?

    I have a feeling that any question of “when are we going to start digging and building” is itself a long way off. Also, based on the history of our present transit system, it’s likely that after we’ve started work, there is time for more than one economic cycle, negative or positive.

    Same with elections.

    But as a general rule I also think that no matter how much time there is before the work seriously starts, it would be good to start talking with the kind of people who are going to build our system.

    Whenever it’s time to start, some basic understanding of what’s really involved in building this project will make our own pre-preliminary designing a lot more productive.


  21. Toronto’s St. George subway station has the perfect transfer. There are two lines running in the same direction, both have center platforms, and one line is directly above the other line. This means any transfer is simply going up/down the stairs, escalators, or elevator. There is no walking down hallways, or going up then down nonsense.

    1. This. If ST is going to “mine” the track box for the new Green Line at the great depth shown in the image they’ve provided, just “mine” it under the existing station, do whatever is necessary for a layover track for the Green Line north of the station and add a central platform to the Red/Blue level. There’s no need for “layover” for a four station line and East Link is forecast to be rather underused.

      That gives people transferring between Red/Blue and Green trains in either direction the opportunity to do so by changing levels between the center platforms of the two lines.

      It’s not likely to cost more than a couple score million million more to have a TBM bore a 500 foot tunnel to the north of the lower level. To get decent transfers for the duration of the system it’s cheap at ten times the price!

      1. I keep seeing people mention a “layover” track. What do they mean exactly? I’m not familiar with that term, and can’t figure it out from the context.

      2. They’re talking about what ST calls the “turn-back track”, which is going to be built in the empty space between the existing tracks at the side-platform Intl Dist Station. ST’s stated purpose of the track is to improve movements between the Eastside and the main train yard (OMF) on Central Link and to stage trains going into and out of service.

        It has nothing to do with the Green Line since it doesn’t go to the Eastside. The track connection for OMF access between the old (to Airport) and new (to West Seattle) lines is likely to be somewhere in the south of downtown.

      3. Oran,

        OK, so you’re saying that ST thinks that it MUST build an interchange track right in the middle of the second most important station in the system, because once in a blue moon some Blue Line train scheduled for maintenance will be SO disabled that it can’t leave service by becoming a Red Line in Lynnwood and heading down to Lander Street? Or enter service from Lander by running as a Red Line to Lynnwood?

        And you’re defending that?

        As I understand it, the fight between Bellevue and Lynnwood was whether East Side trains would go into service at the North End or the East End of the line and ST decided that it gave greater flexibility to have the MF in Bellevue, even though it’s more expensive.

        And yes, I expect that once in a blue moon there WILL be cars that are too disabled to make it to Lander for heavy maintenance. But unless there are exactly four of them or they can’t be coupled for some reason, they can go dead in tow between operable cab cars between 1 and 5 AM.

        There does need to be provision for side-tracking non-operable rolling stock in any railroad system. It’s just not a good idea to do it at the most useful points.

      4. No, I’m not defending it; I’m pointing out links to someone who is unfamiliar with the project. I didn’t even include a siding in my concepts so I have no idea why you even think I’m defending it.

    2. Except St George would be even better if they paired the tracks going in the same direction so you have:

      Upper Platform: Line 2 to Kipling / Line 1 to Downsview
      Lower Platform: Line 2 to Kennedy / Line 1 to Finch via Union

      No level changes for a lot of trips and still the easy up/down one level for the rest.

  22. The complexity of this topic at a major transfer station is apparent. Can we agree to one thing: There is no clearly optimum solution and things like this deserve multiple alternatives to get it right? I hope to see ST look at 10-20 alternatives, rather than pick one or two early in the process.

  23. I’m finding this whole thing too complicated to decide what I like best or which parts are the most necessary. With the Red/Blue Line configuration I had a definite sense that ST was underestimating the demand from the Eastside to the airport and the south end to the Eastside and that people would continually curse about having to go to the surface to transfer every time, and it really needs a center platform and down escalators. With ST’s split spine I’m a bit concerned that connecting Ballard to the south end and West Seattle to Everett which is great for West Seattle but shortchanges Ballard, which more likely goes to West Seattle than the south end, but at the same time I accept that it balances tunnel capacity downtown and a 2-minute transfer is no big deal. But then we get to the two transfer scenarios, ST’a and STB’s, and it gets so complicated I can’t tell whether the best transfers match the highest-volume trips or whether some area is getting shortchanged (if its transfer choices match its destination priorities) because there are so many lines and transfer directions.

    1. The biggest challenge to Eastside-Airport trips is what to do with roller luggage. At the very least, escalators are necessary. With escalators, walking distance is substantially reduced. It’s cheaper to pay to change elevations for people than for trains.

      If the IDS platforms were turned into two center platforms with new Green Line tracks on the outsides (all north bound on one platform and all south-east bound on the other) , ST would see many operational advantages.
      1. Timed transfers would be possible for Green-Red lines or Green-Blue lines. While not needed in peak times, it would be great for midnight trains.
      2. With a cross-over tracks (one in each direction) south of IDS, ST could use the outer (Green Line) platforms if needed in either direction, even for Blue or Red line trains. That flexibility could be handy when operational stoppages happen.

      There would still need to be a southbound Green Line crossover tunnel under the existing DSTT north of IDS, and the steep slope up to 5th or 6th would need to be assessed. Overall, this would appear the least cost construction solution and that savings could be spent on several up and down escalators, maybe a pedestrian underpass of some sort or some other expensive engineering challenge in the area.

      1. Speaking of midnight trains, they need to run each line every 10 minutes until close. The 15 minute headways after 9pm is terrible. I don’t care if the demand for 10 min service exists yet. Improve frequency so they wait is never more than 10 minutes and you’ll induce more late night demand.

    2. Another option would be to hold the two Blue Line and the two Green Line trains at the four platforms for 2 minutes using the three platforms that Oran diagrammed (but have the southbound trains on the east as Tracks 1 and 2 and the northbound trains on the west as Tracks 3 and 4). Then, instruct the riders to walk through one train to reach the next one (Track 1 to Track 3; Track 2 to Track 4).

      Of course, the tail track would have to be eliminated in this option, but if there was a switching track installed between Blue Line I-90 tracks and the outer Green Line tracks the need for the switching track goes away.

      1. It really would be trains from Track 3 to Track 1 (arriving from East King County and leaving towards South King County) and Track 4 to Track 2 (arriving from South King County an leaving towards East King County). A rider would only need to walk through one train to get to the next one.

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