Green Line Reconfiguration

[Riverside]

Surface? I suppose a Gold LRT surface terminal solves the problem of B's lack of access to the Kenmore loop, but if there's not room for some tail/pocket tracks there, that seems like it'd do...unpleasant...things to Gold's reliability (...like after Red Sox games...) unless you nuked half the cross roads for a reservation to the square. Not a reason to outright reject the idea, but it'd be one of the things I'd stick a pin in to scrutinize in any study as a potential danger spot.

Yeah, we've discussed this before... it's definitely a big open question. This is again where the heavy metro/light metro distinction becomes pertinent -- do you need to make staging track space (and platform space, for that matter) for a single 112' T10, or for a double 225' T10? That will impact design and feasibility. (I think I did out the math one time and concluded that it could still be done even for doubles, but need to check that...)

There are a few potential mitigations. First, there is the extant pocket track at Blandford St, which would still be accessible. Second, in a world where a subway is built under Comm Ave, the space currently occupied by the portal and descending tracks could be covered and reallocated for a pocket track or two (depending on how much of the pavement we're willing to reclaim). Third, specifically for the Red Sox game example, an alternate service pattern that temporarily reroutes services into the subway could be established for high-volume crowding periods. (A lot of ways this could be played with, but since it will usually be outside of peak hours, there would be more flexibility.)

Someone (unfortunately, can't remember whom, it may have been @davem) pointed out that it could be possible to build a connection from the BU Bridge under the Mass Pike to hook into the subway under Beacon St, and thus access the Kenmore loop. That is more capital intensive, but could be an interesting alternative.

And finally... in an early-build version of Grand Junction LRT, it may be feasible for a few years to just run Grand Junction trains through Kenmore beyond to Copley & Park St. This doesn't have to be solved on Day 1.

Would a new Back Bay need any provision for short-turns? Wouldn't it be possible to configure Bay Village to allow cars coming from BBY to turn back there? (Even as a flat junction it wouldn't be the end of the world for an extra-helping service pattern.) That'd at least save on having to design-build an additional turnback, and in a more-constrained environment to boot.

Yes, Back Bay would need some sort of short-turn provision to make that service pattern work. I am not 100% certain how that would be done, so I designed this build-out so that the Back Bay short-turn would not be vital.

For example, those short-turns could run to the Kenmore Loop instead (which could be a useful service pattern off-peak as well), and replace the Kenmore-Hyde Square branch (which is a fun idea but hardly vital).

Alternatively, those Back Bay short-turns could be rerouted to Seaport; in this build-out, the Transitway is full (ish) with Green to Park, Aqua to Huntington, and SL3 to Chelsea. But, SL3 can be rerouted to the service, freeing up capacity; and the Aqua to Boston College could instead be rerouted down the Highland Branch. So, Back Bay short-turns could be useful -- and I think would be worth looking at when designing that subway -- but aren't make or break.

Depending on how the Bay Village junction is constructed, short-turns could be done there; in @davem's original proposal, I believe the loopwork would enable that, but in my more recent proposal it would not be a viable turnback point. Given the complexity of the build at Bay Village, I'd rather offload the short-turn provision elsewhere.

In an ideal world, an LRT Back Bay station would be track-plat-track-plat-track: that would enable short-turn service, and also could be used for traffic regulation heading into Bay Village. But this is definitely not required if the footprint is constrained. Alternatively, I'm reasonably confident that space could be found for a pocket track somewhere between Back Bay and Bay Village.

(Finally... there will be about 400 feet of inactive double-track left connecting the Back Bay Subway with the Boylston Street Subway at Copley Jct. I'm not sure how useful this will be for short-turning at Back Bay, but it gives us an additional tool to play with.)

As a transit nerd, I agree with you on this. As someone who spent the entirety of my high school career commuting from Copley to North Station on the Green Line, I'm extremely happy you weren't designing surface patterns at that time . (I know, I could have taken the Orange Line, and I did in fact in the mornings, but the noxious BBY fumes weren't worth the trouble when I actually had to wait there.)

This is a valid critique. Ironically, Copley-North Station is most easily replaced by Back Bay-North Station via Orange/new Green. Hynes-Haymarket/North Station becomes a 2-seat journey, or a 1-seat-plus-walk, as do journeys from Arlington, and most journeys from Kenmore via Blue. (NSRL service from Lansdowne partially mitigates, but not fully.)

This is another place where my idealized Emerald/Green division of labor potentially should be modified to be more nuanced. Of the branches out of Kenmore, I'd feel most excited about running the branch from Harvard/West Station on through past Park St, mostly because I believe that branch's reliability will be the highest, between being a modern new-build and likely have little street-running and fewer stops. I'd likely run it to North Station.

How to "pay" for those extra trains? Probably the easiest way would be to "steal" 1-2 tph from each Green Line branch and have them short-turn at Park St, and run 5-6 tph of the Harvard Branch's 10tph super-extended to North Station. (This of course would make the map look significantly more complicated, but we can't have everything in life!)

Don't send anything BRT from Nubian to downtown, don't even whisper that you might send it anywhere that LRT could conceivably go. You'd just be asking for trouble. "Sorry, you have to take a bus to South Station/Seaport or reverse-transfer at Park? Boylston? because we don't want the hassle of building another leg of the Bay Village interchange at Marginal" is going to raise eleven different kinds of hell with the people who had the Elevated stolen and replaced with a crappy silver bus. I don't disagree with you with respect to the better flexibility of BRT, and I share the concern about the fact that Nubian's branching so close in magnifies its effect on Tremont capacity: I just think it's worth considering that accepting that outsize impact and potentially some service-pattern compromises might be the cost of business in avoiding some potentially-very-nasty political problems. We've all seen specific constituencies kill projects before because they weren't satisfied, let's tread carefully lest we lose more.

(Most of that's just a messaging issue, or at least manageable as one. BRT as a legitimate add-on to places otherwise unreachable from Nubian, fine. So much of a whiff of it as the way out of a harder LRT option, that's gonna be a problem. Even if the actual plan is good and realistic, its sales pitch has to be modified to account for a repeatedly-screwed-over neighborhood's understandable wariness.)

Yes, you are totally right. I would only propose a Navy Line overlay (and yes, the rebranding is not accidental) when and if a robust LRT branch is in place/under construction. (I mean, I do think that the consolidated SL4/SL5 should be extended from South Station through downtown anyway, so in some ways this would just be a continuation of that service.) And we would need to have a strong success story (elsewhere) with true BRT to point to.

But I do think it's ultimately a messaging problem, and there are ways to frame it positively. In addition to an increase in OSRs, having dual layers of service would allow the Green Line to more properly replace the EL -- not as a local surface route, but as an express connection between Nubian and downtown.

And I should say -- Nubian-South Station BRT reduces the need for LRT infrastructure to support the same, but it doesn't necessarily eliminate it. And we can look at it systemically as well: redirecting some Nubian cars away from the Tremont Street Subway and instead to a Red Line connection at South Station would free up slots in the Central Subway, usable for any number of things discussed here. I am unconvinced that the cost-benefit calculation supports that particular solution, but it's something that can contribute overall.

Thanks again for the kind words and thoughtful feedback! I'm glad others find this as enjoyable as I do.

 

[Brattle Loop]

Haha yeah, as much as I love the poetry of an "Emerald Line", particularly given the connection to the Emerald Necklace, I will grant that it's probably more confusing than it's worth. (I'm not sure I made this explicit, but part of the schema is that the "less common" color names like Emerald, Silver, Gold, and Aqua are supposed to suggest the "light metro" tier of service I proposed a few months ago, distinguished from the "heavy metro" of Red, Orange, Green, and Blue.)

Yes, in an ideal world, the Kenmore ("Emerald") trains would run completely isolated on the inner tracks, and the Tremont ("Green") trains would operate independently on the outer tracks. In practice, I think the flexibility of two tracks in each direction available to each service and two loops available to Emerald trains would be important for reliability, particularly since the loop makes it harder to hold trains out of service as needed, etc etc.

It's definitely confusing to some extent, because it confused me! Actually, what I think confused me was the forum software's limited text color selection, because in the table of routes it looked (on my screen, anyway) like the "Green" lines were darker than the "Emerald" lines, but the map was the other way around, I think, hence my confusion over which color-line used which Boylston-Tremont tracks (the map version made sense but didn't comport with my interpretation of the table). I do like the idea of related colors for related service, and I wonder if there's some way to accomplish it without excessive confusion (like how the Disney World monorails mark some of the trains with 'deltas' that are actually trapezoids to distinguish between similar colors, though, of course, colors are not line-specific there).

That last parenthetical point is actually one reason why I'd like to give the Kenmore branches a separate color and line identity altogether. A separate trunk, a separate service pattern, very little overlap...

Yes, in an ideal world, the Kenmore ("Emerald") trains would run completely isolated on the inner tracks, and the Tremont ("Green") trains would operate independently on the outer tracks. In practice, I think the flexibility of two tracks in each direction available to each service and two loops available to Emerald trains would be important for reliability, particularly since the loop makes it harder to hold trains out of service as needed, etc etc.

Again the transit nerd in me agrees, and my high school self would have hated that. (Largely on account of how people's ignorance of how the line worked meant that they'd crowd onto the Lechmere train clogging everything up, I'd wait at Copley for the C train behind it, and have a very comfortable ride to North Station one train behind the sardine can.)

Yeah, this is a good question that I have not contended with. I've been thinking in terms of TPH, not CPH, and really more specifically in terms of "occupied signal blocks". I'm not too concerned about Type 10 singles, but agree that Type 10 doubles are potentially a different beast.

Figured that, it makes sense from a looking from now to the future perspective. T10 doubles are definitely a different beast (and much further off), so it makes sense to roughly translate current TPH to T10 CPH.

Yeah, we've discussed this before... it's definitely a big open question. This is again where the heavy metro/light metro distinction becomes pertinent -- do you need to make staging track space (and platform space, for that matter) for a single 112' T10, or for a double 225' T10? That will impact design and feasibility. (I think I did out the math one time and concluded that it could still be done even for doubles, but need to check that...)

Which I might have thought of if I had remembered that discussion about light and heavy metro before my post. This is what I get for winging it
I don't disagree that it's worth considering, so much as I see "surface terminal" and alarm bells go off for "that's something to really keep an eye on" in any study, but absolutely merits consideration given the inevitable future need to carefully manage Kenmore-Park capacity, the potential difficulty or impossibility of giving Commonwealth/GJ access to the Kenmore loop, and GJ's relatively-low-on-the-pecking-order status with respect to access to inbound capacity from Kenmore.

Depending on how the Bay Village junction is constructed, short-turns could be done there; in @davem's original proposal, I believe the loopwork would enable that, but in my more recent proposal it would not be a viable turnback point. Given the complexity of the build at Bay Village, I'd rather offload the short-turn provision elsewhere.

It was davem's proposal that was in my head at the time. I figure the precise design and layout of the Bay Village interchange would be one of those particularly complex ones, so it does make sense to make provisions for turnbacks elsewhere if BV doesn't work out. I like the idea of the three-track BBY LRT station...just don't do what the CTA did at O'Hare and line a stub track up with an escalator.

Yes, you are totally right. I would only propose a Navy Line overlay (and yes, the rebranding is not accidental) when and if a robust LRT branch is in place/under construction. (I mean, I do think that the consolidated SL4/SL5 should be extended from South Station through downtown anyway, so in some ways this would just be a continuation of that service.) And we would need to have a strong success story (elsewhere) with true BRT to point to.

But I do think it's ultimately a messaging problem, and there are ways to frame it positively. In addition to an increase in OSRs, having dual layers of service would allow the Green Line to more properly replace the EL -- not as a local surface route, but as an express connection between Nubian and downtown.

And I should say -- Nubian-South Station BRT reduces the need for LRT infrastructure to support the same, but it doesn't necessarily eliminate it. And we can look at it systemically as well: redirecting some Nubian cars away from the Tremont Street Subway and instead to a Red Line connection at South Station would free up slots in the Central Subway, usable for any number of things discussed here. I am unconvinced that the cost-benefit calculation supports that particular solution, but it's something that can contribute overall.

Ultimately, I agree with you on the merit of the plan, and in most cases I wouldn't even bring up the messaging at this stage, but given the specific history of that neighborhood when it came to getting screwed by false transit promises, I figured it was worth mentioning just how careful it'd be sensible to be on the messaging, especially if (as here) some of the other moving parts have some dependence on Nubian being served with its specific outlined patterns (i.e., if Nubian forces a disproportionate share of the TPH as a political consequence of bad messaging, it screws up the functioning of the rest of the plan, so it's not even a separate-spheres consideration like it would be more of in places without such a long memory of the transit decisionmakers screwing them).

 

[BosMaineiac]

Yeah, we've discussed this before... it's definitely a big open question. This is again where the heavy metro/light metro distinction becomes pertinent -- do you need to make staging track space (and platform space, for that matter) for a single 112' T10, or for a double 225' T10? That will impact design and feasibility. (I think I did out the math one time and concluded that it could still be done even for doubles, but need to check that...)

I know I’m just jumping in to a long conversation… but this has been on my mind for a while now. Considering we’ve been discussing a “Gold Line” for a bit now as a circuitous route, why not make Gold Line stations long enough for 3 Type 10’s (336’) for long-term capacity? I’ve always thought that would be a good justification for a GJ-Chelsea train not hitting Kenmore and terminating at West Station. I’m also a fan of having a Green Loop train from Park>GJ>Kenmore>Park

 

[Brattle Loop]

I know I’m just jumping in to a long conversation… but this has been on my mind for a while now. Considering we’ve been discussing a “Gold Line” for a bit now as a circuitous route, why not make Gold Line stations long enough for 3 Type 10’s (336’) for long-term capacity?

A quick Google Maps glance doesn't seem to show anywhere on the LRT section of the Urban Ring (which Riverside's Gold Line is at least in part) that looks immediately problematic for a 336' platform anywhere where they'd want to plop a station. Probably wouldn't make sense to make them all full-monster-length from the get-go unless ridership projects extremely high, but absolutely worth a GLX-style provisioning for future extension of the platforms.

I’ve always thought that would be a good justification for a GJ-Chelsea train not hitting Kenmore and terminating at West Station.

Problem is that West is a distinctly inferior node than Kenmore is. There's no meaningful way to have a subway/rapid transit transfer at West that isn't either a.) off the Grand Junction, b.) a spur out from Kenmore, or c.) involving Crazy-ish Transit Pitches for extending the Blue Line past Kenmore, meaning that it doesn't matter all that much how much capacity the GJ has if it just dumps people where they don't need to be or forces a transfer to the Red Line at a point where it's overloaded. One of the secondary benefits of a GJ service that hits Kenmore is that branch riders heading to Kendall would have an easy transfer that takes them off the Red Line, one of several network-level benefits that gets lost if Kenmore's sacrificed from the GJ service in favor of West.

I’m also a fan of having a Green Loop train from Park>GJ>Kenmore>Park

Maybe it's just my username, but I feel like such a service would wind up an almost-loop running Park->Kenmore->GJ->Government then looping at the Brattle Loop and heading back, to avoid touching the nasty-crowded and excruciatingly-hard-to-expand tunnel between Park and GC. No meaningful difference as no stop in the Central Subway would lose GJ service, you'd just need to sign the Park and GC platforms appropriately.

 

[Riverside]

I know I’m just jumping in to a long conversation… but this has been on my mind for a while now. Considering we’ve been discussing a “Gold Line” for a bit now as a circuitous route, why not make Gold Line stations long enough for 3 Type 10’s (336’) for long-term capacity? I’ve always thought that would be a good justification for a GJ-Chelsea train not hitting Kenmore and terminating at West Station. I’m also a fan of having a Green Loop train from Park>GJ>Kenmore>Park

Well, the "why not" would be whether it's possible to fit 336' platforms at the desired stop locations, and what sacrifices elsewhere would be required. I agree in principle that it would be good to design futureproofed stations that could handle that long-term capacity increase! But it may not be the top priority. For example, to me, being able to serve Grand Junction - Kenmore with two car trains is worth more than serving Grand Junction - West Station with three car trains -- but that's just my gut reaction, so we'd need to see the data on it. And like @Brattle Loop said, the name of the game probably is provisioning for future expansion, as opposed to full-builds on Day 1. (And I agree with Brattle's other points, as well.)

It's definitely confusing to some extent, because it confused me! Actually, what I think confused me was the forum software's limited text color selection, because in the table of routes it looked (on my screen, anyway) like the "Green" lines were darker than the "Emerald" lines, but the map was the other way around, I think, hence my confusion over which color-line used which Boylston-Tremont tracks (the map version made sense but didn't comport with my interpretation of the table). I do like the idea of related colors for related service, and I wonder if there's some way to accomplish it without excessive confusion (like how the Disney World monorails mark some of the trains with 'deltas' that are actually trapezoids to distinguish between similar colors, though, of course, colors are not line-specific there).

Ooh yeah the text color problem is real... Like I said, "emerald" is actually a vaguely defined color, which as we've seen has upsides and downsides!

Yeah I do think the LRT system would need to adopt numbers and/or letters and use a more NYC-style system where the colors are used to group individual services. Part of me wants to be really crazy and just go London style: I'm talking "the Garden Line" ("Gahden Line"), the "Ocean Line", the "River Line", the "Central Line", from which we can branch out (no pun intended) even further.

Which I might have thought of if I had remembered that discussion about light and heavy metro before my post. This is what I get for winging it
I don't disagree that it's worth considering, so much as I see "surface terminal" and alarm bells go off for "that's something to really keep an eye on" in any study, but absolutely merits consideration given the inevitable future need to carefully manage Kenmore-Park capacity, the potential difficulty or impossibility of giving Commonwealth/GJ access to the Kenmore loop, and GJ's relatively-low-on-the-pecking-order status with respect to access to inbound capacity from Kenmore.

No worries, I certainly don't expect you to remember everything I write. And full agreement here, particularly with regard to "something to keep an eye on".

Full agree on the delicate situation vis a vis Nubian.

 

[Brattle Loop]

Yeah I do think the LRT system would need to adopt numbers and/or letters and use a more NYC-style system where the colors are used to group individual services. Part of me wants to be really crazy and just go London style: I'm talking "the Garden Line" ("Gahden Line"), the "Ocean Line", the "River Line", the "Central Line", from which we can branch out (no pun intended) even further.

Do an opposite Chicago. They went from named lines (mostly destination based) to colors, we'd do the inverse, and help maintain Boston's reputation for confusing navigation .

In reality, we already use a weak NY-style system on the Green Line, with the color assigned to services sharing the Central Subway, and specific services designated by letters, one that's actually gained importance with GLX opening up given that now the letters really matter going north/eastbound. I go back and forth on whether it'd make specific sense to separate Tremont and Boylston Street services by color given that they both serve the core, but definitely for anything not hitting the Lechmere->Park->Boylston stretch it'd be a good idea to separate out by color.

No worries, I certainly don't expect you to remember everything I write. And full agreement here, particularly with regard to "something to keep an eye on".

I just felt like I wrote all that response and then you mentioned the light metro concept again and that's when I remembered we'd had that whole Kenmore discussion not that long ago. That's a dang-it on me, because that was a very interesting discussion and absolutely validated the Gold Line idea I quibbled with because I forgot about it.

 

[Teban54]

Actually, what I think confused me was the forum software's limited text color selection, because in the table of routes it looked (on my screen, anyway) like the "Green" lines were darker than the "Emerald" lines, but the map was the other way around, I think, hence my confusion over which color-line used which Boylston-Tremont tracks (the map version made sense but didn't comport with my interpretation of the table).

You can actually choose your own color by entering its Hex code. More tedious, but doable.

 

[Riverside]

Today’s post on my blog gives a name to a concept we’ve discussed multiple times in this thread, under various names like “flexi-junction” and “three-way junction”. For various reasons (some of which are outlined in my post in the Fantasy T Maps thread), I propose a dedicated name to describe this kind of interchange: the Aldgate Junction.

The Aldgate Junction concept forms the heart of the Green Line Reconfiguration idea. By shifting away from an exclusively trunk-and-branch model, the Green Line can be transformed into a fully fledged distributed network with capacity to stretch across Metro Boston.

Over the years, the Reconfiguration concept has identified several locations for possible Aldgate Junctions. Some of these are integral, and some are not required but would significantly enhance the system. Several locations have multiple proposals for how to achieve an Aldgate Junction, but the functional requirements are largely the same.

Integral:

• Bay Village, between Tufts Medical Center, the Pleasant Street Portal, and Back Bay, to enable:
  • Park St - Back Bay
  • Park St - Nubian/South Station
  • Back Bay - South Station
• BU Bridge, to enable:
  • Kenmore - Harvard
  • Kenmore - Grand Junction
  • Harvard - Grand Junction
• Brickbottom Junction, at the intersection of GLX and the Grand Junction, to enable:
  • Lechmere - Grand Junction
  • Lechmere - Union
  • Lechmere - Medford
  • Lechmere - Sullivan
  • Grand Junction - Sullivan
  • Union - Sullivan

Enhancing:

• Brookline Village, to enable:
  • Kenmore - Riverside
  • Kenmore - Huntington
  • Riverside - Huntington
• Riverway, to enable:
  • Kenmore - Heath
  • Kenmore/Riverside - Huntington
  • Heath - Huntington
• Bay Village East, to enable:
  • Park - Nubian
  • Park/Back Bay - South Station
  • Nubian - South Station
• Cleveland Circle & Chestnut Hill Ave, to improve flexibility for non-revenue moves at that end of the network

(I should also note that we have at times discussed the possibility of modifying Kenmore to serve as a highly-compressed Aldgate Junction to enable “wraparound” service between the B and D Lines. This particular Aldgate Junction may be physically impossible, given current space constraints. All others described here are believed to be theoretically possible, though Brickbottom Jct – supporting the largest variety of journeys – presents difficulties.)

The introduction of Aldgate Junctions – particularly at the three integral locations – opens up radical possibilities for new kinds of LRT service in Boston, including circumferential services in Cambridge and reverse-branching to link Back Bay and points west with the Seaport, without reducing capacity or service within the existing system.

But – perhaps even more importantly – Aldgate Junctions will entirely reshape the resilience and flexibility of the network, both over the long-term as commuting patterns evolve, and in the short-term in the event of service disruptions.

The key to these successes lies in the logical properties of the Aldgate Junction concept itself. Recognizing – and naming – that concept allows us to recognize similar deployments around the world and learn from them.

 

[Brattle Loop]

(I should also note that we have at times discussed the possibility of modifying Kenmore to serve as a highly-compressed Aldgate Junction to enable “wraparound” service between the B and D Lines. This particular Aldgate Junction may be physically impossible, given current space constraints. All others described here are believed to be theoretically possible, though Brickbottom Jct – supporting the largest variety of journeys – presents difficulties.)

Fascinating post per usual, and I like the idea of naming the junction concept for ease of reference. I might have more to add later, but off the bat I'm curious about Brickbottom's difficulties. My read is that the Grand Junction <--> Sullivan and Lechmere -> Sullivan legs already have viable/identifiable paths for completion (via the carhouse leads), and it's mainly the Sullivan->Lechmere inbound leg that doesn't have a quasi-pre-provisioned solve (though there are available options). Just checking if that's what you're referencing or if there's another complication I've missed somewhere on that one?

 

[Riverside]

Fascinating post per usual, and I like the idea of naming the junction concept for ease of reference. I might have more to add later, but off the bat I'm curious about Brickbottom's difficulties. My read is that the Grand Junction <--> Sullivan and Lechmere -> Sullivan legs already have viable/identifiable paths for completion (via the carhouse leads), and it's mainly the Sullivan->Lechmere inbound leg that doesn't have a quasi-pre-provisioned solve (though there are available options). Just checking if that's what you're referencing or if there's another complication I've missed somewhere on that one?

Yeah, that is indeed what I was referencing -- discussed upthread starting here: https://archboston.com/community/threads/green-line-reconfiguration.5003/page-43#post-430430

It also becomes a lot more challenging to incorporate Union <--> Sullivan through the spaghetti than it looks zoomed out on paper.

 

[Riverside]

The Green Line turns 100 today!

No really, I'm serious -- what we know as the Green Line meaningfully began 100 years ago today with the opening of the transfer station at Lechmere. I go through the history and significance of this event in today's blog post.

Why does this matter? Several reasons.

First, it makes clear that the T's effort to get street-running trolleys out of the subway dates back earlier than the temporary suspensions of the Arborway and Watertown Lines, earlier than the post-war embrace of the automobile suburb, but in fact dates all the way back to the early 1920s -- almost as soon as motorbuses became commercially feasible, and likely was under consideration even without the availability of motorbuses. The 1920s and 30s saw a massive winnowing of the subway-streetcar network, a decline which in fact slowed following World War II. (It's remarkable that the Arborway Line survived as long as it did.) There is massive institutional inertia at play here, which has consequences for future proposals.

Second, it illustrates that the Tremont Street Subway was built for a purpose that was abandoned less than one generation after its construction; since then, the T and its predecessors have used a variety of techniques to reshape it for fundamentally different use -- largely with success, but with continued vestiges of its original (and very different) intended use.

Finally, I argue this gives a bit more perspective to those photos showing all the different destinations that could be reached from Park Street in the Tremont Street Subway's early days; our modern experience of the Green Line skews our imagination, picturing that early system in a form that did not exist until 20 years later. To us, the early Tremont Street Subway would have been more like today's Harvard Busway than what we are familiar with at Park Street.

Happy birthday to the Green Line!

~~~

This post ended up spinning out several side projects, and actually served as the impetus to start the blog itself. I have more content coming on the streetcar network of this era, as well as one or two other items of interest. (I have also added a "Library" section to my site, with a back catalogue of some of my posts here, as well as a few additional pieces of updated content.)

 

[Arlington]

Not sure where this goes, but I thought Green Line fans should see where the tunnels at Gov Center are "in real life" This picture, from the Ode to Brutalism thread shows the tunnel-tops being re-waterproofed, including how City Hall bridges over the "outbound" D & E coming from the glass box station (at right) downhill toward Haymarket (off the left edge)
Photo Credit: @dshoost88

 

[Arlington]

Roughly?

 

[Arlington]

I am guessing the little bridge in the infield is about where the inner loop is?

 

[Brattle Loop]

I am guessing the little bridge in the infield is about where the inner loop is?

Looks to be in the right vicinity.

 

[Tallguy]

So, if Seaport is to connect to GL we seem to mostly agree that, from the I-93 tunnel to SS at least, needs to go under Essex St. Is there enough distance between the tunnel and the surface to use a TBM, or is cut and cover necessary?

 

[Brattle Loop]

So, if Seaport is to connect to GL we seem to mostly agree that, from the I-93 tunnel to SS at least, needs to go under Essex St. Is there enough distance between the tunnel and the surface to use a TBM, or is cut and cover necessary?

Per Google Maps it's something like 650-700 feet between the Transitway at Essex and Atlantic to the insertion point under the over-wide plaza at the intersection of Surface and Essex. I don't know if that's TBM length or not, though there's also the potential complicating factor that the 93 tunnel is two different levels at that point.

 

[Tallguy]

Per Google Maps it's something like 650-700 feet between the Transitway at Essex and Atlantic to the insertion point under the over-wide plaza at the intersection of Surface and Essex. I don't know if that's TBM length or not, though there's also the potential complicating factor that the 93 tunnel is two different levels at that point.

Sorry, I am assuming that the rest of the route(in my case, Marginal Way) is TBM. I am asking if there is enough between the surface and the top of the tunnel to have the TBM go over the tunnel or will C&C be necessary

 

[Brattle Loop]

Sorry, I am assuming that the rest of the route(in my case, Marginal Way) is TBM. I am asking if there is enough between the surface and the top of the tunnel to have the TBM go over the tunnel or will C&C be necessary

Don't know, but the answer might not be the same for the two halves of 93. I think 93 South is pretty shallow through there.

 

[ceo]

So, wait, are you going under Boylston/Essex St from Boylston station, or reusing the abandoned Tremont St tunnel and looping around under Marginal St? If the latter, Essex St doesn't figure in at all, the tricky part is getting into the Transitway alignment under Atlantic Ave. I-93 northbound dives deep under here to get under the Red Line, but I don't know if the MassDOT District 6 building would be in the way.
If the former, I-93 southbound here reuses the old Dewey Square Tunnel and is barely deep enough to grow flowers over it; you'd have to go under.
In any case, I'm pretty sure the distances are too short for a TBM to make sense; it'd have to be cut and cover the entire way.