Crazy Transit Pitches

[Brattle Loop]

I also felt a bit that I was covering the most boring part of the series. The sense I get is that most people perusing this thread have already heard of extending the Blue Line to Kenmore -- usually in tandem with a Blue-to-Riverside extension, which I cover next week. Blue-to-Kendall gets less consistent attention, but once you get past Kendall, there is no consensus on where to go next, or what role the Blue Line should be playing in the network at that point. So I feel there isn't much to say.

Hello again and thank you for another well-written post. I agree that most of us in this thread have heard of most if not all of the ideas you discussed, but as with the previous posts in your series it is quite useful to have them compiled together for easy reference, so there's considerable value to even what you might think of as the "boring" part of the series.

I should also say -- transit geology is not something I'm super knowledgeable about. Individuals I respect have walked me through how a subway under Storrow would be feasible, so I feel confident in that proposal (even if I don't feel confident in my ability to explain it). The extensions to Cambridge, I feel much less solid about (no pun intended). Back in the day, F-Line was pretty insistent that tunneling under the Grand Junction was a non-starter, which would impact two of the three Cambridge alignments I discuss in my post. I make a handwaving comment regarding the challenges of working with landfill, but I'm not confident on it to speak authoritatively. However, if Grand Junction alignments are indeed ruled out, then the Cambridge options take a big hit.

I'm a touch too busy at the moment to go digging through this thread and the Green Line Reconfiguration thread for F-Line's posts, so I'm working from memory here. As I recall, the principal problem was that digging under the GJ means that any tunnel there has to go under the Red Line at Main Street, meaning that not only do you have a tunnel beginning in fill near the BU bridge (I don't think an MIT-vicinity jaunt over to Kenmore was ever discussed given F-Line's clear preference for Riverbank as a means of Blue to Kenmore, so I don't know if it necessarily shares quite the same concern), you've got a giant siphon (possibly with its own water-ingress issues) that poses a giant flood risk that doesn't currently exist to the Red Line tunnel which would be right above it. As I understood it at least part of the concern is that mitigating the flood risk would or at least could cost a fortune. I think it was less about landfill and more about the fact that any GJ tunnel is basically putting a giant potential pipe of water straight under the Red Line. I don't know if that renders any GJ alignments impossible or not, but F-Line for one was way down on the prospect.

Avoiding the Grand Junction by doubling up the Red Line under Main St and Mass Ave sounds like a tunneling nightmare, and I don't think tunneling to the north toward Somerville (e.g. under Hampshire St) fulfills a pressing transit need (my earlier crayon map of the Blue Line taking over GLX notwithstanding). So, if I'm being honest, I do believe that the Kendall option starts off at a disadvantage.

Leaving aside the question of how to interface the Blue to Kendall in the first place (I still don't understand what the plans area at Volpe to know if that's going to be a nasty problematic blocker or not), I agree that doubling up the Red Line's probably more trouble than it would be worth. I suspect that there isn't room for a side-by-side tunnel, especially under Main Street, meaning you'd have to either go under the existing tunnel and underpin it all the way to Central (including adding a second, lower level to that station), or try and bore deep and away from the street grid and building foundations if that's even possible there. All of that's hard, but I think you hit on the real problem in your post, which is that when the stations are distanced it forces line choice in advance and removes a lot of the flexibility of doubled service. If anything I think you underestimate the problem; unless something is done about the State Street curve and every platform on the line, the Blue Line is still going to have much smaller cars and trains than the Red, meaning that Red will have way more capacity on its more-frequent headways (though depending on where Blue went post-Cambridge, it might have more open space that partially negated the issue). Makes me think that studying how to deal with the Harvard curve (which I believe is ultimately the structural element that will put a ceiling on the Red Line's maximum headways), difficult as that would be, might be a better cost proposal than doubling Blue to Red.

One reason that I chose to sidestep the geology questions is because of where I go in the last two posts in the series after this. I think, when you take a step back and look at the big picture, the Kenmore option wins out without needing to take the geology into account -- ultimately I believe there are more compelling reasons in favor of a Kenmore alignment that render the geology question moot.

I agree with the assessment, looking forward to the remaining posts.

 

[Teban54]

Leaving aside the question of how to interface the Blue to Kendall in the first place (I still don't understand what the plans area at Volpe to know if that's going to be a nasty problematic blocker or not), I agree that doubling up the Red Line's probably more trouble than it would be worth. I suspect that there isn't room for a side-by-side tunnel, especially under Main Street, meaning you'd have to either go under the existing tunnel and underpin it all the way to Central (including adding a second, lower level to that station), or try and bore deep and away from the street grid and building foundations if that's even possible there.

I will probably sound stupid for asking this, but: is there any way for Blue Line to have the Kendall station somewhere near Broadway without underpinning Red Line there, then tunnel under Broadway and Prospect St to meet RL again at Central (underpinning RL here instead), before finally heading towards Allston and Watertown as per Riverside's post?

 

[Brattle Loop]

I will probably sound stupid for asking this, but: is there any way for Blue Line to have the Kendall station somewhere near Broadway without underpinning Red Line there

Only way to get there without going under the Red Line probably involves the river crossing going up Broad Canal and then tunneling under Broad Canal Way. The question I can't answer is whether the Blue Line can handle the curves from Broad Canal Way onto Third, and then Third onto Broadway, and handle them without punishing speed restrictions. If it can, then yes you could probably plop a station under Broadway somewhere away from the Red Line. If it can't, that means plowing through the Volpe site, which is often talked about here, but which I don't think has any provisions for tunneling through there, so by the time any momentum came for extending Blue that route could well be choked off.

then tunnel under Broadway and Prospect St to meet RL again at Central (underpinning RL here instead)

The Broadway-to-Prospect turn looks like it would be pretty brutal if not impossible. I've got no idea if deep bores not following the streetscape are possible in this area of Cambridge. It may or may not be doable, but it'd probably be pretty hard, and some of the gains from not encroaching the Red Line at Kendall would be given back in the extra tunneling to get to Central (especially problematic because that's not mission-critical; it'd be a better transfer than offset stations at Kendall, but you don't really need both, and Kendall better serves the high-demand area).

 

[luobo]

This is when I wish we had the willingness and ability to build subways like those Asian cities. I myself am originally from China and have witnessed all the cities opening new lines like crazy every year.

In that kind of alternate reality, we would have completed RBC, BLX and OLX, started construction of the Huntington-Seaport subway, and figured out a way to somehow make the entire Urban Ring LRT or even HRT with dedicated ROW...

100% this. One of the more radicalizing experiences of my life was living in Nanjing for several years and watching the city open an entirely new subway line every year for four years straight.

There are some legitimate reasons why it's harder here but 80% of it is really political will, status quo bias, inefficiency, and a general lack of vision. We managed to get all of those highways built, there are very few legal or technical barriers to doing so much better than we are currently doing on transit.

 

[Brattle Loop]

80% of it is really political will

We managed to get all of those highways built, there are very few legal or technical barriers to doing so much better than we are currently doing on transit.

Unfortunately the manner in which a lot of those highways got built (especially in urban areas) left a very bad taste in a lot of people's mouths. It's hard to build political will for a vision when there's hordes of NIMBYs (some of whom may have a point, some who don't) screaming at you over every possible change. I think a big part of the solution is re-conditioning the public/electorate to not reflectively recoil at transit/public works projects, which is not an easy thing to accomplish.

 

[luobo]

Those very same NIMBYs will scream even louder if you propose undoing the damage done by those very same urban highways. A lot of it is status quo bias and car dependency Stockholm Syndrome.

 

[Brattle Loop]

Those very same NIMBYs will scream even louder if you propose undoing the damage done by those very same urban highways. A lot of it is status quo bias and car dependency Stockholm Syndrome.

I agree with the fact that status quo bias has a big impact. That said, I don't necessarily agree with the Stockholm Syndrome comment about car dependency. The lack of transit options and over-focus on highways undoubtedly caused (and continues to cause) car dependency for many, in many places, but some of the discussion on that topic elides the degree to which car use is preferred, as opposed to being forced/conditioned ("Stockholmed"). There's nothing irrational about any given individual opposing a project or policy change that would negatively impact them (i.e., someone who prefers driving to transit opposing transit projects at the expense of road projects). I think both of those elements are relevant, and trying to categorize it all as simply status quo bias and road-Stockholming risks overlooking the other motivations that move in the same direction.

 

[Riverside]

Just wanted to briefly respond to some of @Brattle Loop's comments (and much appreciation for your kind words and engagement!):

I'm a touch too busy at the moment to go digging through this thread and the Green Line Reconfiguration thread for F-Line's posts, so I'm working from memory here. As I recall, the principal problem was that digging under the GJ means that any tunnel there has to go under the Red Line at Main Street, meaning that not only do you have a tunnel beginning in fill near the BU bridge (I don't think an MIT-vicinity jaunt over to Kenmore was ever discussed given F-Line's clear preference for Riverbank as a means of Blue to Kenmore, so I don't know if it necessarily shares quite the same concern), you've got a giant siphon (possibly with its own water-ingress issues) that poses a giant flood risk that doesn't currently exist to the Red Line tunnel which would be right above it. As I understood it at least part of the concern is that mitigating the flood risk would or at least could cost a fortune. I think it was less about landfill and more about the fact that any GJ tunnel is basically putting a giant potential pipe of water straight under the Red Line. I don't know if that renders any GJ alignments impossible or not, but F-Line for one was way down on the prospect.

Thanks for this. Yes, this is my general recollection as well, although in my review of some of the oldest posts in (I think) this thread, I believe there were concerns raised about the fill itself.

For my part, I also just believe that Grand Junction is infinitely more useful as a surface-running LRT spine than anything else. I've spent way too much time thinking about possible topologies of an expanded Green Line, and the availability of the Grand Junction makes a night-and-day difference.

Leaving aside the question of how to interface the Blue to Kendall in the first place (I still don't understand what the plans area at Volpe to know if that's going to be a nasty problematic blocker or not), I agree that doubling up the Red Line's probably more trouble than it would be worth. I suspect that there isn't room for a side-by-side tunnel, especially under Main Street, meaning you'd have to either go under the existing tunnel and underpin it all the way to Central (including adding a second, lower level to that station), or try and bore deep and away from the street grid and building foundations if that's even possible there. All of that's hard, but I think you hit on the real problem in your post, which is that when the stations are distanced it forces line choice in advance and removes a lot of the flexibility of doubled service. If anything I think you underestimate the problem; unless something is done about the State Street curve and every platform on the line, the Blue Line is still going to have much smaller cars and trains than the Red, meaning that Red will have way more capacity on its more-frequent headways (though depending on where Blue went post-Cambridge, it might have more open space that partially negated the issue). Makes me think that studying how to deal with the Harvard curve (which I believe is ultimately the structural element that will put a ceiling on the Red Line's maximum headways), difficult as that would be, might be a better cost proposal than doubling Blue to Red.

Thanks for this also -- yes, you anticipated my points about tunneling under the Red Line (in an earlier draft, but trimmed in the final revision). It's a lot of headache for an improvement that I think is insufficient. And yes, improving the Harvard curve strikes me as a better cost-benefit calculation.

That's actually a good point about Blue Line cars vs Red Line cars, I hadn't considered that explicitly. But yeah, I think that goes back to an idea I introduced earlier in this series, and which I'll come back to later -- the Blue Line has a long history of siblinghood with the Green Line, which is reflected in their routings but also in their rolling stock.

 

[Brattle Loop]

That's actually a good point about Blue Line cars vs Red Line cars, I hadn't considered that explicitly. But yeah, I think that goes back to an idea I introduced earlier in this series, and which I'll come back to later -- the Blue Line has a long history of siblinghood with the Green Line, which is reflected in their routings but also in their rolling stock.

Mildly off-topic but a neat historical footnote: [Crazy?] Transit Pitches existed long before ArchBoston, such as this 1903 Boston Transit Commission plan to connect the East Boston Tunnel to the Central Subway. The Blue-Green Connector that never was (and we're probably much better off for it.)

 

[Charlie_mta]

Mildly off-topic but a neat historical footnote: [Crazy?] Transit Pitches existed long before ArchBoston, such as this 1903 Boston Transit Commission plan to connect the East Boston Tunnel to the Central Subway. The Blue-Green Connector that never was (and we're probably much better off for it.)

I remember reading on here a long time ago that the reason the connection shown above didn't happen is because the Green and Blue lines were under different agency jurisdictions. and couldn't agree on this proposal.

 

[Riverside]

The Blue-Green Connector that never was (and we're probably much better off for it.)

Yeah, it's been on my to-do list for a while now to game out how a system like that would've developed over the ensuing 100 years. (I actually did it once already, but misunderstood the proposal and thought it was supposed to be a total reroute away from Haymarket... but it's clear it was meant to be a branch-off.) It certainly would have been wildly different from what we have today. I'm not sure I'm convinced that it would have been wildly worse, though.

 

[Charlie_mta]

Yeah, it's been on my to-do list for a while now to game out how a system like that would've developed over the ensuing 100 years. (I actually did it once already, but misunderstood the proposal and thought it was supposed to be a total reroute away from Haymarket... but it's clear it was meant to be a branch-off.) It certainly would have been wildly different from what we have today. I'm not sure I'm convinced that it would have been wildly worse, though.

The Blue line as an LRV branch of the Green Line would have provided the option of making the Silverline to Chelsea an LRV line, branching off an LRV Blue Line just beyond Airport Station. I think it would have been a good thing.
However, I thing 4-tracking the GL between GC and Park Street would be needed for this much loading of lines and branches.

 

[Brattle Loop]

I remember reading on here a long time ago that the reason the connection shown above didn't happen is because the Green and Blue lines were under different agency jurisdictions. and couldn't agree on this proposal.

Interesting. I'm pretty fuzzy on the history of who built, owned, and operated what in that era.

The Blue line as an LRV branch of the Green Line would have provided the option of making the Silverline to Chelsea an LRV line, branching off an LRV Blue Line just beyond Airport Station. I think it would have been a good thing.
However, I thing 4-tracking the GL between GC and Park Street would be needed for this much loading of lines and branches.

Especially with a double-branch LRT Blue Line, and no meaningful room for a turnback at Scollay/Government (and no easily-identifiable place for one until possibly Kenmore or maybe somewhere around the Pleasant Street portal), then, yes, expanding the Tremont Street Subway main trunk between GC and Park to 4 tracks would probably have been required. Don't know if that would have been much less difficult digging way back when (though the NIMBYism would probably have been less and/or more easily ignored).

 

[Riverside]

Don't forget -- these Blue-Green connections pre-date the proposals for the subway extension to Post Office Square. So in this counterfactual alternate history where the East Boston Tunnel was hooked into the Tremont Street Subway, it's possible that the Post Office Square Subway would later have swallowed (for example) the trolleys that had been entering the subway at the Public Garden, which might have negated the need for quad-tracking the Tremont. Then at that point, it would be a relatively short extension to connect Post Office Square to the tunnel at Adams Square. (Plus, if the Riverbank Subway had been built, that would have diverted the Kenmore trolleys out of the Tremont Subway altogether.)

I spent entirely too much time mocking this up:

The precise "date" of this mock-up is iffy, so don't look too hard... for example, it's probably "anachronistic" to show the Red Line extended beyond South Station Under, but no biggie.

Blue is streetcars through the East Boston Tunnel. Green is streetcars from the Public Garden portal, via Post Office Square, then to points north (following the same northerly routes as the streetcars did in real-life).

Dark Green are the "foreign" streetcars, which in this "timeline" continued to use the precursor to the Brattle Loop at Scollay Upper. (Note that the streetcar tunnel was quadtracked between the Brattle Loop and the Haymarket portal, and that Adams Square was directly under what would become the Orange Line, which is how the Post Office Square Subway would've been relatively easy to line up to the tunnel north of Adams.)

Lime Green is the Riverbank Subway. (If this "timeline" were to be built out further, perhaps we would have seen the tracks connected between the Riverbank and Tremont lines... originally the Riverbank was just going to end in a loop, level with the rest of Park Street Upper, but it would have been easy to create a level junction.)

The dotted Orange is the Atlantic Ave El, which I believe even by this point was already starting to see reduced service.

As a stylistic choice more than anything else, I've chosen to depict the subway stations as BERy treated them -- off-set station pairs. One notable feature of the Post Office Square extension proposal was the lengthy underground walking transfers:

• the two subway stations at Boylston would be connected by a east-west platform between them,
• the complex that became Downtown Crossing (but at the time were Winter, Summer, and Washington stations) would be expanded to include a station at the far end of the Red Line platform, at Otis Street,
• and then the complex that became State station would have been expanded to encompass the Blue Line Devonshire station, the Orange Line northbound State station, the Orange Line southbound Milk station, and the new station at Post Office Square

Anyway, my point is just that an East Boston-Tremont connection would have made significant impact on the topology of the network, and there would have been a lot of ripple effects -- easy to imagine good ones and bad ones alike.

P.S. I fell deep deep down the rabbit hole, and mocked up the modifications they would have needed to make to Adams Square to connect a Post Office Square Subway. (Original source here.) Light grey indicates new tunnel, including under Devonshire, and then cutting into the loop at Adams itself. I think the turn radius for the foreign streetcars (in the darker green) would still have been within acceptable limits, although just barely. (This of course being an utterly useless exercise, since all of the infrastructure pictured here has been long demolished.)

 

[F-Line to Dudley]

Hello again and thank you for another well-written post. I agree that most of us in this thread have heard of most if not all of the ideas you discussed, but as with the previous posts in your series it is quite useful to have them compiled together for easy reference, so there's considerable value to even what you might think of as the "boring" part of the series.



I'm a touch too busy at the moment to go digging through this thread and the Green Line Reconfiguration thread for F-Line's posts, so I'm working from memory here. As I recall, the principal problem was that digging under the GJ means that any tunnel there has to go under the Red Line at Main Street, meaning that not only do you have a tunnel beginning in fill near the BU bridge (I don't think an MIT-vicinity jaunt over to Kenmore was ever discussed given F-Line's clear preference for Riverbank as a means of Blue to Kenmore, so I don't know if it necessarily shares quite the same concern), you've got a giant siphon (possibly with its own water-ingress issues) that poses a giant flood risk that doesn't currently exist to the Red Line tunnel which would be right above it. As I understood it at least part of the concern is that mitigating the flood risk would or at least could cost a fortune. I think it was less about landfill and more about the fact that any GJ tunnel is basically putting a giant potential pipe of water straight under the Red Line. I don't know if that renders any GJ alignments impossible or not, but F-Line for one was way down on the prospect.



Leaving aside the question of how to interface the Blue to Kendall in the first place (I still don't understand what the plans area at Volpe to know if that's going to be a nasty problematic blocker or not), I agree that doubling up the Red Line's probably more trouble than it would be worth. I suspect that there isn't room for a side-by-side tunnel, especially under Main Street, meaning you'd have to either go under the existing tunnel and underpin it all the way to Central (including adding a second, lower level to that station), or try and bore deep and away from the street grid and building foundations if that's even possible there. All of that's hard, but I think you hit on the real problem in your post, which is that when the stations are distanced it forces line choice in advance and removes a lot of the flexibility of doubled service. If anything I think you underestimate the problem; unless something is done about the State Street curve and every platform on the line, the Blue Line is still going to have much smaller cars and trains than the Red, meaning that Red will have way more capacity on its more-frequent headways (though depending on where Blue went post-Cambridge, it might have more open space that partially negated the issue). Makes me think that studying how to deal with the Harvard curve (which I believe is ultimately the structural element that will put a ceiling on the Red Line's maximum headways), difficult as that would be, might be a better cost proposal than doubling Blue to Red.



I agree with the assessment, looking forward to the remaining posts.

There's 2 big frictions working against each other here. . .

• Yes, the water mitigations for the under-GJ 'spigot' are particularly nasty. Especially since the tuck under the Red Line is unfortunately placed right on a sharp curve, meaning the long descent needs to happen well before the curve to prevent crippling speed restriction (apply same calculus to any depth-v.-curve games with turning BLX-Volpe onto the GJ alignment). Meaning, it's a whole lot of tunneling feet to waterproof given how long this deeper-bored spigot is going to end up being. Given that the Urban Ring alignment already has a Major Investment Study detailing mega ridership at very attractive cost-per-rider figures, HRT tunneling carries with it a daunting tally of gold-plating cost premium that needs a revenue avenue for cost amortization. Yes, in absolute feasibility you could do it if you went balls-out on the active flood mitigation...but what makes that a baseline requirement for doing anything? Surface UR LRT's cost-per-rider projection studied out sooooo incumbently good, without engaging any of the risk. Is there truly an order-of-magnitude benefit above and beyond to be found by changing it up to BLX that pays for the difference? If so, what is it? Nobody has yet to cite it in concrete/non-wishful terms.

• Volpe redevelopment is proceeding with full institutional knowledge of that UR Major Investment Study. The numbers have all been crunched for what megadeal the UR's travel patterns would do for the Kendall area's future, and the Volpe folks have stone-cold baked those future projections and who'll be using it into the end vision for this site redev. Hard MIS ridership numbers for a project that doesn't require them to reserve space in their basement for anything special. BLX-Volpe, being just a blogger creation that got some temporary notoriety on the Internet, doesn't have any hard numbers attached to it. It's basically a bog-standard definitionally "Crazy" pitch, in that it's pitching a testable theory without any prior study's worth of testable data. Ari O. at the time of his post was pressed in comments (on his blog and on Twitter): "What exactly does this do that the Urban Ring doesn't do well enough?" And he didn't have any real answer for that. Crickets, actually. The fact that he hasn't written any more about it in the ensuing 3+ years kind of says something there. Maybe, just maybe, this feast already gets substantially cooked by the UR MIS and forging ahead with that. Since any notion of a BLX here would have to have Volpe reserving space around actively proceeding heavy redevelopment to provision for it, time's a-wasting to quantify exactly what the gold-plating cost premium for BLX translates to in the real world vs. the known-known cost of doing the Urban Ring. Because Volpe's already taken into account the UR's potential impacts with their overall plans; the above-and-beyonds for BLX-instead are still completely unstated despite them being the ones tasked with hazard avoidance for it.

So, it's a very asynchronous one-on-one debate. One's an unfunded mandate with a toothy MIS on-the-books already informing everyone's future projections throughout the neighborhood, one is an unfollowed-up napkin sketch. Napkin sketch with attention-seeking build dependencies under Volpe's property, and a clock that keeps ticking while Volpe redev actively infills itself. I for one can't imagine what the gold-plating premium for BLX actually brings that's revolutionarily above-and-beyond UR LRT. Blue seats 210 per 6-car train at minimum 3-minute headway. Green over the Ring will seat about 135 on a 2-car train of Type 10's, with identical 3-minute headway by virtue of overlapping 2 alternating radial vs. Downtown-oriented patterns on the line (Red, by contrast, does 279 seats per 6-car train at minimum 3-minute headway...capacity king of the heap by a lot). More total routings afforded by the UR mode, with a difference of 6- vs. 3-min. headways to Eastie/Airport (i.e. if every other UR frequency stays radial). Each line would have its own particular efficiencies for some audiences, but there's not really a "WOW!" audience's worth of disparity between the two. The napkin sketch has a ton of hand yet to show itself if it's going to successfully alert the Volpe developers to contour their buildout while it's already in motion and start weighing the pros/cons of provisioning space for a pathway. That's an incredibly large burden to have to overcome in short order. Again, the very well credentialed original author of the scheme apparently wasn't feelin' it enough after being faced with these same questions to keep developing the scheme further in the ensuing years, so that kind of says something about what the likely endpoints are going to be here with this debate.


I broadly agree about BLX-Kenmore (then points TBD...though I'm personally way warmer to Allston/Watertown than HRT'ing the D) being a clear head-to-head winner if we're going to be BLX'ing anything past Charles. Bigger bang, trailblazes some new ground not adequately covered by other near-equally good studies on the books, and fewer (but not zero, because of the whither-Storrow factor) dependencies that have to break just so for it to work right. As well as not being under any truly punitive time crunch for making its own provisioning decisions.

 

[Riverside]

Great to see you again, F-Line, and thanks as always for the great info. As for where to go after Kenmore, I think you’ll like the next two posts I’ve got coming…

 

[Riverside]

This week's post gets into the "fun stuff" -- specifically, where do we go after Kenmore or Kendall?

There are three major ideas that get thrown around, and which all, in my opinion, are somewhat "crazy" but still "reasonable" enough to distinguish them from (for example) replacing GLX with the Blue Line: Blue to Highland Branch, Blue to B&A, and Blue to Watertown & Waltham. I think all of these have significant merit, and I think all present significant challenges.

I confess that the genesis for this series actually came from wanting to avoid repeating myself regarding the challenges of Blue-to-Riverside, which is probably the most common "crazy transit pitch" I come across. And to be clear, sending the Blue Line to Riverside is itself a solid idea, which has been around since at least 1971, from what I can tell.

What I've tried to illustrate in my post, however, are the knock-on effects of such an extension. To put it perhaps provocatively: "Future Commuter Rail riders in New Bedford would rue the day the Blue Line was extended to Riverside."

On a different note, though I spend a good amount of time outlining why such extensions would be challenging, I personally find an extension to Watertown the most promising, at least on a 100-year timescale. It would require a generation of advocacy. Moreover, I think it is even further down the road than "Phase 2", as I believe that an intermodal West Station, with transfers to circumferential service and regional rail, would itself be a logical "second phase" destination point, in that it would provide valuable service, would still leave options open for the future, and would potentially be a modestly low-impact build.

I believe that @Charlie_mta has put forth proposals for a largely-elevated ROW between West Station and Watertown Square, and while obviously very expensive, I do think it's a compelling proposal, but again, on a 100-year timescale. I do think building further to Waltham is hard to imagine, in any century. And, as I outline in the post, I believe a better alternative to serve Watertown is a combination of LRT and Regional Rail. I could also envision an elevated extension along the Mass Pike to a major transfer center at Newton Corner; replace the Boston Landing commuter rail station with a Blue Line stop, and then add extra stops at Blue Line-spacing at Market St, Parsons St and Bigelow St, and allow Regional Rail service to run express between Newton Corner and West Station. I like both of these ideas, but I also don't think either of them is a surefire winner. Better to lay the groundwork with extensions to Kenmore or maybe West Station, and add Regional Rail service, and see where that lands us first.

That all being said -- if we want to talk about truly crazy transit pitches, imagine what a Blue-to-LMA extension would set you up for. Kenmore to LMA to Roxbury Crossing to Nubian to Newmarket to Seaport to Logan to Airport to Chelsea to Everett to Wellington. (Yes, I made a map of this, yes, it is ridiculous, yes, I will post it at some point. I named the file "Project Blue Lace", to rhyme with "shoelace" because the Blue Line looping back on itself looks a bit like a shoelace. Yes, I was way too happy with myself for the pun.)

 

[Brattle Loop]

I confess that the genesis for this series actually came from wanting to avoid repeating myself regarding the challenges of Blue-to-Riverside, which is probably the most common "crazy transit pitch" I come across. And to be clear, sending the Blue Line to Riverside is itself a solid idea, which has been around since at least 1971, from what I can tell.

What I've tried to illustrate in my post, however, are the knock-on effects of such an extension. To put it perhaps provocatively: "Future Commuter Rail riders in New Bedford would rue the day the Blue Line was extended to Riverside."

It's unfortunate that the Needham Line's best replacement option effectively precludes the option of HRT on the Highland Branch, at least without screwing over at least one of the other CR services. That said, if SCR Phase II gets killed off by Phase I collapsing under the weight of its born-brokenness, or if the Corps of Engineers never allows a solution to the lunatic trestle through the wetlands, might there be enough spare NEC capacity to keep the Needham Line and therefore permit Blue-to-Riverside? (I kind of doubt it, but someone might know more.)

That all being said -- if we want to talk about truly crazy transit pitches, imagine what a Blue-to-LMA extension would set you up for. Kenmore to LMA to Roxbury Crossing to Nubian to Newmarket to Seaport to Logan to Airport to Chelsea to Everett to Wellington. (Yes, I made a map of this, yes, it is ridiculous, yes, I will post it at some point. I named the file "Project Blue Lace", to rhyme with "shoelace" because the Blue Line looping back on itself looks a bit like a shoelace. Yes, I was way too happy with myself for the pun.)

I love it as a Crazy Transit Pitch, though it's bringing flashbacks of F-Line's epic dismantling of LRT tunneling for the southern half of the Urban Ring in the Green Line Reconfiguration thread. I'm guessing the same infeasibility and absurd cost would presumably apply to this pitch as well (but of course we don't need to bother as much with those considerations in this thread).

Fascinating post as usual, Riverside, I look forward to the conclusion of the series.

 

[The EGE]

No, Needham conversion is a necessity no matter what. West Roxbury and Needham desperately need the frequency, and the line is always going to have an outsized impact on NEC operations. Inbound Needham trains either have to run on the west track - thus effectively turning the Southwest Corridor into a two-track line for Amtrak + Providence + Franklin + Stoughton (and heavily limiting Needham frequency) - or they have to cross over at Forest Hills and block other traffic.

The Highland Branch wouldn't be the right choice for the Blue Line regardless. Past Brookline Village, there's not that much density - it's mostly small village centers save for the Cleveland Circle area, which is also served by the B and C. It does great as a light rail line, and there's simply not the population to need heavy rail. All the other western possibilities - Allston, Brighton, Watertown, Waltham, and the north part of Newton - have much more population and all-day demand possible.

You have to convert every station - not just building high platforms, but a lot of crossover bridges to replace the current crossings - and find a new Green Line yard and maintenance facility to replace Riverside. All that cost and disruption, for what? Brookline and Newton don't have a significant improvement in their service, they lose direct North Station service, and trade Copley for a station further from the High Spine. Needham gets nothing. The only real win - elimination of a transfer to Longwood and Brookline Village - is equally achievable with D-E connector and Blue to Brookline Village, and it's pretty minor anyway.

 

[F-Line to Dudley]

On a different note, though I spend a good amount of time outlining why such extensions would be challenging, I personally find an extension to Watertown the most promising, at least on a 100-year timescale. It would require a generation of advocacy. Moreover, I think it is even further down the road than "Phase 2", as I believe that an intermodal West Station, with transfers to circumferential service and regional rail, would itself be a logical "second phase" destination point, in that it would provide valuable service, would still leave options open for the future, and would potentially be a modestly low-impact build.

I believe that @Charlie_mta has put forth proposals for a largely-elevated ROW between West Station and Watertown Square, and while obviously very expensive, I do think it's a compelling proposal, but again, on a 100-year timescale. I do think building further to Waltham is hard to imagine, in any century. And, as I outline in the post, I believe a better alternative to serve Watertown is a combination of LRT and Regional Rail. I could also envision an elevated extension along the Mass Pike to a major transfer center at Newton Corner; replace the Boston Landing commuter rail station with a Blue Line stop, and then add extra stops at Blue Line-spacing at Market St, Parsons St and Bigelow St, and allow Regional Rail service to run express between Newton Corner and West Station. I like both of these ideas, but I also don't think either of them is a surefire winner. Better to lay the groundwork with extensions to Kenmore or maybe West Station, and add Regional Rail service, and see where that lands us first.

The easiest way to build to Watertown is probably tunneling under the B&A to Newton Corner, then turning north in a Galen St. tunnel to the Square and unifying the awkwardly async NC+H2O bus hubs into true load-bearing West Region last-mile feeders. The B&A doesn't have utility relocation or a utilities sandwich layer like any under-street alignment would. You could essentially make it a miles-long Wellington tunnel with the bare tunnel roof functioning as the replacement Worcester Line trackbed and nicely wide-open construction windows to blitz it since the staging of the trench is all right-lane closures on the Pike and some sliding-scale pain threshold of temporary Commuter Rail/Amtrak disruption. And then Galen, while being a conventional (if mercifully short) street cut-and-cover, already features the live ex-A Line 600V DC feeder trunk running underneath it (currently used as a B Line-to-71 power interconnect). You'd save some considerable cash on BLX's substation construction by glomming off the existing power interconnects on the corridor and boosting some pre-existing 600V subs on the system instead of building at least one wholly new substation on a greenfield alignment.

Excludes Newtonville-Auburndale but would functionally re-create the densest majority of the "Riverside 2" rapid transit line from the 1945 BTC map, shotgunned onto the densest outside-of-Boston portion of the ex-A Line. And pitched that way...not quite so "Crazy"-sounding a cleanroom pitch because of the liberal appropriating of well-trodden study & prior-service ground. I agree you probably ain't ever getting direct to Waltham from there because of myraid technical challenges and middling intervening density, but for what NC+H2O would do overall for West Region bus connectivity Waltham might not truly need to be a link on that specific chain (plus Waltham can always be GLX'd as a 6-min. frequency branch out of Porter when Regional Rail isn't enough for them).