Regional Rail (RUR) & North-South Rail Link (NSRL)

Tallguy

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Going under the harbor, possibly?

Somewhere earlier in this thread (and/or in Crazy Transit Pitches) there was a discussion of a similar proposal. It hamstrings the entire works because now three Northside lines (well, four if you count Reading and Haverhill separately, but Reading has its own issues that make it a messy fit for NSRL pair-matching) have to feed off of one (two-track) tunnel. Maybe that problem can be mitigated (especially if the Eastern Route can take service equivalent to half a 4-track NSRL), but if the pair-matching isn't perfect it'd introduce a complication of having a subset of some Southside services not hitting the transfer nodes (or, at least, not doing it at the same place).



The OL doesn't go to Revere. I assume you're adding that as a prerequisite along with a Blue transfer station at Airport (probably feasible) and a Green Line connection to South Station (probably feasible, but expensive). It's a lot of prerequisites to solve the problems with a proposal that...solves a problem that doesn't exist. (If the Eastern Route couldn't be solved with a 4-track CA/T NSRL as has regularly been proposed, that would be one thing, but separating out the Eastern Route just because needs to actually justify itself beyond the cruddy crossings in Chelsea, because blowing all of those to smithereens would cost way less than another cross-harbor tunnel.)
It shaves 8-10 min off the trip to SS from ER
It gives more direct access to Logan from the west and south
It provides an inexpensive way of bringing OL to Everett,Chelsea, and Revere, which sorely needs it


Do you have any data to support your assertion that underwater tunneling is more expensive?
 

Brattle Loop

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Do you have any data to support your assertion that underwater tunneling is more expensive?
Well, that was more of a hunch. That said, the broader point (admittedly not made all that clear in my post) is that regardless of whether it's more expensive to tunnel underwater than on land, it's unquestionably going to cost a hell of a lot more to make two tunnels than one.

It shaves 8-10 min off the trip to SS from ER
Compared to what? The current alignment with the nasty speed restrictions plus a North Station-aligned NSRL? Just the North Station-aligned NSRL with the speed restrictions nuked through unspecified means?

It gives more direct access to Logan from the west and south
Valid goal, but an extremely expensive way of doing it (because of all the tunneling). (Hunch alert:) Probably doesn't make it on cost-benefit analysis if that's the main purpose.

It provides an inexpensive way of bringing OL to Everett,Chelsea, and Revere, which sorely needs it
Well, we've transited to Crazy Transit Pitches here. I assume this would involve running the Eastern Route CR tunnel route through the old industrial track route (whether on the surface or not) via airport into this new tunnel, meeting up with the existing Eastern Route somewhere around Revere Beach Parkway? Freeing up the existing ER to that point? Does this hypothetical OL extension end at the Parkway? Somewhere past there (if the ROW's wide enough)?

Just to do that Orange branch at all, you'd need to nuke the Chelsea grade crossings (admittedly not quite as hard on HRT as on RR), and you'd have to do something about the bridge by the casino, because CSX has freight rights to the produce market, so wholesale-mode-swapping that stretch is impossible without CSX relinquishing its rights lest the feds obliterate you from orbit. Not to mention the numerous reasons given in numerous threads and never to my knowledge actually refuted with data by anyone about why branching the Orange Line isn't a great idea.

Is is possible to do? Yeah, probably. I have yet to see anything close to convincing as to why it makes sense to do this rather than the base 4-track NSRL. I suppose I could be convinced by data if it showed a massive problem if NSRL didn't have a good Blue Line connection (though the much-needed BLX to Lynn would link Blue and the ER) and if building Central Station on a CA/T alignment blew out the cost worse than doing this would. But, absent that, I don't see why two tunnels is better than one. (Especially since if you take the Chelsea-inbound ER off the RR mode for OL conversion, you're chaining everything ER to the tunnel, which doesn't make pair-matching any easier.)
 

BosMaineiac

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I don't see why two tunnels is better than one.
Technically the 4-track CA/T requires two tunnels. It would take two 41’ diameter bores with two tracks each. I’m not sure if there’s a boring machine large enough to hold 4 tracks but there might be. Does anyone know if Crossrail or East-Side Access had 4-track single bores and if that would be feasible for NSRL?

Here’s the cross-section from the MassDOT study:
F7AD1B17-C833-4DE7-B195-99BBAB5B693F.jpeg

I've seen a proposal (probably here) for a NSRL North Station roughly between the Green/Orange North Station and Haymarket. So you could still connect to North Station proper (albeit with kind of a long walk) but be closer to downtown at the other end.
The same study also had a rendering for the CA/T 2-track NS and it did indeed have a connection at the southern end to Haymarket:
CCE40C53-FAA4-4CCF-8D8F-EF52C456026C.jpeg


As much maligned as the study is, it does have some pretty cool renderings, including a 4-track Central Station:
ADAD0BFF-68DF-49E7-8F53-A0C275619EE6.jpeg


Here’s a link to the study documents if anyone’s interested in digging into them:

 

Brattle Loop

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Technically the 4-track CA/T requires two tunnels. It would take two 41’ diameter bores with two tracks each. I’m not sure if there’s a boring machine large enough to hold 4 tracks but there might be. Does anyone know if Crossrail or East-Side Access had 4-track single bores and if that would be feasible for NSRL?
Yeah, but that's two tunnels on the same alignment. The idea of running an Eastern Route tunnel up and out across the harbor would at minimum mean more portals, more non-shared tunneling. (I'm assuming that even two bores would share some of the prep and construction work, especially around the portals, which would have to be duplicated for non-shared alignments.)
 

Charlie_mta

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Yeah, but that's two tunnels on the same alignment. The idea of running an Eastern Route tunnel up and out across the harbor would at minimum mean more portals, more non-shared tunneling. (I'm assuming that even two bores would share some of the prep and construction work, especially around the portals, which would have to be duplicated for non-shared alignments.)
The Highway 99 deep bored tunnel under downtown Seattle has 4 roadway lanes, (two 2-lane roads stacked in the same tube) roughly comparable to the space that would be needed for 4 tracks. So I'm guessing a 4 track bored tunnel is feasible with 2 tracks stacked over two tracks, all in one tube.
 

Teban54

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I'd like to quote Riverside's reply in the 2020 discussion regarding a RuR tunnel to Logan Airport, which pretty much sums up all arguments against it:

First of all, welcome to the board @BosMaineiac! Always great to see new faces around here.



Likewise, always great to see another supporter of NSRL! And I like the imaginativeness you've brought to the topic -- that's always an important part of the discussion.



I share your interest in resurrecting that straightaway along the Eastern Route that runs pretty much directly from Lynn (!) all the way to the current Airport station. It is incredibly tempting, especially from a "neat and tidy" perspective. It's just right there.



And as others have noted, there once in fact was a proposal for exactly the kind of cross-harbor tunnel you are describing here between South Station and East Boston. You can see a map of that here on Wikipedia (although ironically they would have hooked this tunnel into today's Blue Line, rather than into the straightaway).



I like the thinking behind incorporating an East-West dimension into the Rail Link concept, but I think it's ultimately unnecessary for a few different reasons.



First, the time/distance savings just aren't that much; I did some back-of-the-napkin math, and from what I can see the best case scenario is shaving a 15-minute journey into a 10-minute journey (with non-trivial drawbacks -- see below).



Second: you argue that this East-West link would reduce the need for BLX to Lynn, but I'm skeptical. One of the arguments in favor of a North-South link is that it would allow northside riders better access to downtown, which North Station is more removed from than South Station. But South Station itself still isn't the be-all-end-all. Many riders have destinations outside of the Financial District (which is better served by the Blue Line than South Station anyway), and the Blue Line (assuming a Blue-Red connector) offers much better transfer opportunities than an East-West tunnel to South Station would; such a tunnel would dump all of its riders on to the Red Line, who would then need to traverse the already-most crowded section of the line. Plus, South Station-Longwood Medical Area is a significantly more awkward journey than State/Gov't Center-Longwood Medical Area (and more on that in a second, too).



And that brings us to another drawback of a cross-tunnel routing -- it avoids a transfer node at Sullivan which can distribute Cambridge- and Somerville- (and maybe even Allston-) bound riders without going downtown, and it actually results in a trajectory that, overall, misses downtown much more than a Chelsea-Sullivan-North Station-South Station alignment would.



Third (and I'm surprised this hasn't been brought up yet): how exactly would things work at South Station in terms of that X-shaped network you've drawn? Is it a Camden Town-style double flying junction, with essentially two stations allowing all trains to go everywhere? Is it like District Line Earl's Court with a single unified station with flying junctions before and after? Or do you abandon "all trains go everywhere" and split the network into a North-South network and an East-West network with separate superimposed stations à la Notting Hill Gate? Or with cross-platform transfers akin to Finsbury Park?



The reason this matters -- aside from the potential for an incredible amount of spaghetti under there -- is that you have to trade-off between the network comprehensiveness of "all trains everywhere" and the speed reductions incurred by crossovers, curves and capacity constraints. Plus, it impacts passenger journeys: you could mitigate some of that Red Line transfer crush if you can guarantee some x % of trains will travel Airport-Back Bay, Airport-Ruggles and Airport-Lansdowne, but again, that is going to entail a much more complicated build. (Plus, addressing the needs of incoming Airport riders impacts riders from the other direction as well, shunting away trains that might otherwise serve downtown more directly.)



^ Okay, so there are challenges with this -- any infrastructure proposal has challenges; the question is whether it's worth the benefit.



And that brings us to this (emphasis mine):







This lurks in the background of your proposal, and I want to examine it further. What exactly is the benefit of creating all this infrastructure for the benefit of the Eastern Route? (Setting aside access to the airport.)



Put another way, why would Amtrak run trains along the Eastern Route? The Western Route ends up getting you to the same place in Southern Maine, and has the benefit of hitting Haverhill/Lawrence and UNH along the way. Newburyport is practically a seaside village by comparison. Moreover, when leveraged with the Wildcat Branch, as the Downeaster currently does, a Western Route alignment can bootstrap itself to the Main Line (Lowell Line), which is the much stronger candidate for Amtrak expansion into New Hampshire (Nashua, Manchester and Concord).



(And, indeed, on the 100-year timescale, an alignment via Lowell is where Boston should be looking for its northern expansion -- follow that alignment long enough and you hit Montreal; there's nothing comparable north of Newburyport and there almost certainly never will be.)



So, in summary, while I like the idea for its creativity and imagination, I'm pretty skeptical of its ultimate benefit.



An alternative:



So the one big benefit that I haven't addressed is better access to the airport. There's a larger political and theoretical debate here that I'm not qualified to weigh in on (about the merits of intercity rail-airport connections). But I will happily and generally agree that better public transit access to Logan is a Good Thing, even if I'm agnostic on where it should rank on the priority list.



Your proposal calls for a massive investment in a cross-harbor tunnel to provide transfer-minimal public transit access to Logan. Let me propose an alternate version of the same.



Instead of a mainline rail tunnel hooked into the NSRL, construct a roomy third tunnel along the Ted Williams Tunnel alignment that can support light rail, BRT and intercity buses. Hook it in directly to the existing Silver Line Transitway tunnel (along with a connection to the I-90 tunnel for those Greyhounds and a surface portal) and convert the Transitway to dual BRT/LRT running. If you have extra money, expand the Transitway into "four tracks/four lanes" to support non-stop South Station-Airport Terminals services.



On the other end, hook the tunnel into the mode of your choice -- continue running BRT to the terminals at street level, build an elevated LRT in lieu of the APM, construct an APM/LRT transfer station along Harborside Dr, what have you. Personally I think the ideal would be integrated LRT all the way -- not saying that you use long-haul South Station-Chelsea LRT service as a terminal shuttle -- you probably want to have some dedicated short-turns -- but that seems like it would give maximum flexibility.



For local public transit, a third TWT would obviously be a boon, speeding access and reliability to Logan from the Seaport, Southie and the South End, closing the one section of the Urban Ring Corridor that's Really Hard™ to put rail into. Moreover, a dual LRT/BRT tunnel would give maximal flexibility for metropolitan connectivity -- the downside of a mainline rail tunnel is that you can only put electrified mainline rail through it. A properly designed dual-mode tunnel could support a veritable smorgasbord of urban and suburban and regional services.



For regional access to the airport, a third TWT would I think ultimately be more beneficial than an East-West Rail Link. Assuming an NSRL, all suburban quadrants would have direct access to South Station, from which it'd be a single transfer to direct terminal access; by contrast, under an EWRL, only North Shore riders and whichever service(s) from the south get paired would have access to Airport Station, from which they'd still need to transfer to the APM.



A dual-mode tunnel also gives you a lot more flexibility with alignments and grades. When working with mainline rail, you have to deal with longer platforms, gentler grades and therefore longer approach tunnels. A dual-mode tunnel gives you a lot more flexibility both at South Station and at the airport.



Finally, it's worth pointing out that while South Station may seem far away from the airport, it really isn't. An express South Station-Airport service would only travel ~2.75 miles. The JFK AirTrain from Jamaica Station in NYC travels a bit less than twice as far. (And, of course, Jamaica Station itself is already between 20 and 60 minutes from Manhattan, depending how you travel.)
TL;DR:
  • Time savings from Eastern Route (Lynn) to South Station is insignificant
  • BLX is still needed
  • Direct ER-to-SS connection, in addition to missing North Station access, also misses connections at Chelsea and Sullivan (e.g. buses and Urban Ring to Kendall)
  • Pair-matching between northside and southside Commuter Rail lines become significantly more challenging, both in engineering and operations. (This also means most southside lines won't get frequent access to Logan, while other northside lines don't get Logan access at all.)
  • A RuR cross-harbor tunnel only gets you to Airport Station and still requires a transfer to Massport buses or APM; SL1 brings you from SS right to Airport Terminals
  • The money is better spent on a third Ted Williams bore for LRT/BRT
Points brought up by others:
  • Demand for regular Airport travels is small, unless at a scale of Paris
  • 4-track CA/T NSRL offers much more capacity and flexibility compared to this plan, likely at lower cost
 

Riverside

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I'd like to quote Riverside's reply in the 2020 discussion regarding a RuR tunnel to Logan Airport, which pretty much sums up all arguments against it:


TL;DR:
  • Time savings from Eastern Route (Lynn) to South Station is insignificant
  • BLX is still needed
  • Direct ER-to-SS connection, in addition to missing North Station access, also misses connections at Chelsea and Sullivan (e.g. buses and Urban Ring to Kendall)
  • Pair-matching between northside and southside Commuter Rail lines become significantly more challenging, both in engineering and operations. (This also means most southside lines won't get frequent access to Logan, while other northside lines don't get Logan access at all.)
  • A RuR cross-harbor tunnel only gets you to Airport Station and still requires a transfer to Massport buses or APM; SL1 brings you from SS right to Airport Terminals
  • The money is better spent on a third Ted Williams bore for LRT/BRT
Points brought up by others:
  • Demand for regular Airport travels is small, unless at a scale of Paris
  • 4-track CA/T NSRL offers much more capacity and flexibility compared to this plan, likely at lower cost
Thanks @Teban54! Am glad my wall-of-text is still somewhat useful!

The only modification I'd make now is that I would de-emphasize my earlier arguments about travel time. Shaving 15 min to 10 min is probably mildly more worthwhile than I suggested it was in 2020, when I was pretty dismissive of it. That being said, it's a minor change to a single point, and I still feel that there are many points that make the idea both inviable and ill-advised.
 

Riverside

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I'm going to return to the previous discussion about the merits of a Central Station. I think one aspect to consider is what our overall goal with the NSRL is supposed to be. If it's about creating a de facto rapid transit line through downtown, then that might tilt things in favor. If it's about providing Northside commuters with direct access to Back Bay and Longwood, then that tilts things away.

As others have pointed out, if your North Station Under in fact connects to Haymarket (which may not shorten your walk to State Street, but means more of it occurs protected from the elements), I think that reduces the need for a Central Station even further. Based on the suggested headhouse locations for North Station, the 10-min walksheds from the headhouses (and keep in mind those will be more like 15-min walks from the platforms) nearly overlap:

Screen Shot 2023-01-25 at 3.17.43 PM.png


Screen Shot 2023-01-25 at 3.17.21 PM.png


If you measure from Haymarket (which, granted, yes, this would probably be a 20-min-total walk from the platform), the walksheds fully overlap:

Screen Shot 2023-01-25 at 3.18.51 PM.png


And something to keep in mind about Central Station -- the same geography that contributed to the downfall of the Atlantic Ave El remains today: half the walkshed will be underwater.

I'd be interested in seeing a design for (Central Artery alignment) South Station Under that either shifts the platform a little further north, or adds a headhouse in the vicinity of Pearl St & Atlantic Ave, or both. Putting the midline of the platform near the Post Office is fine, but the majority of the downtown core (plus the Seaport, for that matter) is located north of Summer St, so centering the platform on Congress St (or even further north) would bring passengers closer to their destinations.
 

vanshnookenraggen

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I've always like the compromise of having a combined North and Central Station around Haymarket Sq. Except for the Garden, North Station isn't a destination. It was just where trains stopped running. So with appropriate length platforms, you can get people to North Station and get them closer to the heart of the city.
 

Riverside

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I've always like the compromise of having a combined North and Central Station around Haymarket Sq. Except for the Garden, North Station isn't a destination. It was just where trains stopped running. So with appropriate length platforms, you can get people to North Station and get them closer to the heart of the city.
Yeah I think this is reasonable. I'm looking again at the diagrams from the 2019 study, and, again, I am confused. The South Station Under headhouses suggest a need for about 600 feet of horizontal running space to go from platform to surface, and it looks like the North Station Under location is even deeper (but seems to have more compactly located headhouses).

That suggests that it should be possible to have a headhouse within North Station Upper that travels diagonally downward a running distance of 600' (or more), "landing" perhaps 25% of the way down an 800' platform whose northern end sits under Valenti Way, and which stretches down to Sudbury St, with a southern headhouse as far south as Hanover St. Which, to your point, gets folks closer to the heart of the city.

Obviously you could move it even further south, but I think if we're gonna build this thing, it's worth preserving a reasonable North Station Upper > NS Under transfer so that longer-distance commuters (e.g. from Fitchburg or Newburyport, where electrification will be a longer time coming) can transfer to NSRL trains to access Back Back or Longwood, rather than piling on to the Orange Line.
 

Teban54

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I've always like the compromise of having a combined North and Central Station around Haymarket Sq. Except for the Garden, North Station isn't a destination. It was just where trains stopped running. So with appropriate length platforms, you can get people to North Station and get them closer to the heart of the city.
Edit: Oops, I didn't see Riverside already replied.

From what I've gathered in the discussions, the issue is that not all northside Commuter Rail trains will be able to use NSRL, so some trains may still terminate at the surface North Station. While it still gives you Green and Orange connections, transferring to NSRL CR trains becomes much harder if NS Under is at Haymarket.

The caveat is the number of northside trains that will use the surface terminal:
  • 4-track CA/T build may greatly reduce this concern given more capacity
  • There are fewer northside branches (and tph needed) than southside, so it's more likely that a greater proportion of northside trains can enter NSRL compared to the south, even in a 2-track build
The 2018 study did suggest removing surface NS altogether IIRC, at least for the 4-track alternative.
 

The EGE

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I really don't think we need to worry about ensuring surface/tunnel transfers at North Station.

At absolute maximum buildout, you're looking at something like:
Fitchburg: 4 TPH Waltham + 2 TPH Wachusett + <1 TPH intercity = 7 TPH
NH Main: 2 TPH Concord + 2 TPH Nashua + 2 TPH Haverhill + 1 TPH intercity = 7 TPH
Western: 4 TPH Reading
Eastern: 4 TPH Salem/Peabody + 2 TPH Rockport + 2 TPH Newburyport = 8 TPH

That's 26 trains per hour - a bit above the limit of 2-track capacity, or well within 4-track capacity - and likely to be lower if Reading becomes Orange Line.

The first priorities for electrification are likely going to be the inner portions of the lines - there's the most frequency gain to make use of the electrification, and the outer portions have more difficulty with freight clearances etc. That will make transfer possible at the innermost station shared between tunnel and surface trains. It'll be much easier for a Newburyport passenger to make a same-platform timed transfer to a tunnel train at Lynn (until Newburyport gets electrified) than to deal with a vertical transfer at North Station.
 

Riverside

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I really don't think we need to worry about ensuring surface/tunnel transfers at North Station.

At absolute maximum buildout, you're looking at something like:
Fitchburg: 4 TPH Waltham + 2 TPH Wachusett + <1 TPH intercity = 7 TPH
NH Main: 2 TPH Concord + 2 TPH Nashua + 2 TPH Haverhill + 1 TPH intercity = 7 TPH
Western: 4 TPH Reading
Eastern: 4 TPH Salem/Peabody + 2 TPH Rockport + 2 TPH Newburyport = 8 TPH

That's 26 trains per hour - a bit above the limit of 2-track capacity, or well within 4-track capacity - and likely to be lower if Reading becomes Orange Line.

The first priorities for electrification are likely going to be the inner portions of the lines - there's the most frequency gain to make use of the electrification, and the outer portions have more difficulty with freight clearances etc. That will make transfer possible at the innermost station shared between tunnel and surface trains. It'll be much easier for a Newburyport passenger to make a same-platform timed transfer to a tunnel train at Lynn (until Newburyport gets electrified) than to deal with a vertical transfer at North Station.
I've gone back and forth a lot about this. I definitely agree that at full build-out, transferring from an Upper train to an Under train at Porter/Medford (?)/Sullivan or Lynn, is better than transferring at North Station. But...

Well, the concept works best on the Fitchburg Line, where you are likely to see near-future electrification to 128, with high-freq short-turn electric services that pretty much guarantee that, on average, a transferring Wachusett rider would need to wait ~7 minutes for a Tunnel train (potentially less if scheduled is optimized, though in theory could be more if the schedule is obnoxious).

Western: who the hell knows, this one is going to be weird no matter what. Transferring at Malden will involve probably a 15-min wait, so not desirable, but potentially transferring at Sullivan (assuming useful scheduling on the Eastern) could be feasible.

Eastern: I think this is where we first see some trouble with this model. Yes, if Salem is electrified and you run 4 tph short-turns, then you can mimic the situation at Porter, where you can hopefully transfer from a Surface to Tunnel train with about ~7 min of waiting at Lynn. But, the model starts to break down when your electric short-turns drop below 4 tph: if Newburyport and Rockport are alternating every 15 minutes, and your Tunnel service runs every 20 min, it means that at least one Surface train per hour will have an ugly transfer:
Surface service​
Tunnel service​
Wait for Surface -> Tunnel transfer​
0:00​
7 min​
0:07​
0:15​
13 min​
0:27​
0:30​
17 min
0:45​
2 min​
0:47​
1:00​
7 min​
There are ways to play around with the timetabling that can mitigate this somewhat, if you are willing to sacrifice (or at least be flexible) about clockfacing schedules. But none of it is pretty. (As an example, a Surface train every 30 min, with an electric Tunnel service of equal frequency with a short off-set, e.g. a Surface train at 0:00 and 0:30, with an Electric train arriving 5 min after each. But now you've abandoned turn-up-and-go. And in this case, it relegates the Rockburyport branches to hourly freqs.)

And I think the NH Main is where this system really breaks down. To mimic the Fitchburg model, you need electric service short-turning somewhere around Woburn. But to your point, Haverhill + Lowell/Nashua + Concord get you to 6 tph awfully quickly. Even if you make that more modest (e.g. 2 tph to Haverhill, 2 tph to Nashua of which 1 continues to Concord), you're back to the same problem we saw at Salem: you need an additional 4 tph from ~Woburn to make the transfers reliable, and at that point those tracks are getting pretty busy (anywhere from 9 to 11 tph).

My point is that for the transfers to work, you need 4 tph of an electric Tunnel service in addition to however many Surface services you're running. At best, that is going to be excess to demand on everything except Fitchburg (and maybe Reading, who knows), and at worst it bumps you up against capacity limits.

~~~

ALSO. I am reminded about this:

That's 26 trains per hour - a bit above the limit of 2-track capacity, or well within 4-track capacity - and likely to be lower if Reading becomes Orange Line.
I am decidedly not a professional, so I could be completely off-base. But, the only justification I've seen (and maybe there's a better one in the 2003 DEIR, I haven't had a chance to look) to support the 24 (or 22) tph per tunnel capacity is a comparison to the Gateway tunnel and to Crossrail:

1674697877981.png


And... I have questions? For one, the Gateway tunnel is long, straight, has no stations, and at one end sees trains come screaming out of the portal to zip across the Jersey marshes at full speed. The NSRL, by contrast, will be constantly curved and will have multiple stations. And as for Crossrail (the Elizabeth Line) -- its tunnel segment utilizes CBTC with essentially automated operation. As far as I can tell, no equivalent proposal exists for the NSRL.

(I also generally am skeptical of this page's claims since they make the -- shall we say, interesting -- assertion that the second tunnel would only be able to handle 4 trains per hour because of the [unjustified and highly debatable] claim that the Fairmount Line can only run 4 tph. Which. Like. Is so incredibly backwards. It's misleading to suggest that the second tunnel would have a "maximum" of 4 trains per hour -- that number has nothing to do with the tunnel itself, and suggests that there was no real examination of the dynamics of the tunnel and therefore its potential capacity.)

So, I don't really know where the 22 tph per tunnel capacity comes from, other than "we googled the timetables for two other railroad tunnels and copied them".

Maaaaybe if we back of the napkin this: it's about 1 mile between the SS Under and NS Under platforms. At 30 mph, that takes two minutes to traverse. So, let's say the train leaves SS Under at 0:00; it occupies the tunnel for two minutes before pulling in to NS Under at 0:02. It dwells for 30 seconds, and departs at 0:02:30, at which point the block is fully clear for the next train to pull out of SS Under at 0:02:45. If you can keep up that cadence, which I admit seems... ambitious on the face of it... then you can fit the 22 tph they are claiming.

In some ways it doesn't matter -- they assert anyway that "upstream constraints" limit the available trains to 17 MBTA tph + 1 Amtrak tph. That stretches the cadence to 3 min 20 seconds, which is roughly enough time to make the journey at 30 mph (a number I'm totally making up, to be clear), followed by over a minute of dwelling. So, I mean, that seems feasible enough, so I don't think it necessarily changes any of the study's conclusions.

But yeah, the 22 tph number is still a bit mysterious to me, so if anyone knows or can guess at a more rigorous methodology that would justify that, I'm all ears.
 

Tallguy

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I'd like to quote Riverside's reply in the 2020 discussion regarding a RuR tunnel to Logan Airport, which pretty much sums up all arguments against it:


TL;DR:
  • Time savings from Eastern Route (Lynn) to South Station is insignificant
  • BLX is still needed
  • Direct ER-to-SS connection, in addition to missing North Station access, also misses connections at Chelsea and Sullivan (e.g. buses and Urban Ring to Kendall)
  • Pair-matching between northside and southside Commuter Rail lines become significantly more challenging, both in engineering and operations. (This also means most southside lines won't get frequent access to Logan, while other northside lines don't get Logan access at all.)
  • A RuR cross-harbor tunnel only gets you to Airport Station and still requires a transfer to Massport buses or APM; SL1 brings you from SS right to Airport Terminals
  • The money is better spent on a third Ted Williams bore for LRT/BRT
Points brought up by others:
  • Demand for regular Airport travels is small, unless at a scale of Paris
  • 4-track CA/T NSRL offers much more capacity and flexibility compared to this plan, likely at lower cost
80-110 THOUSAND people fly in or out of Logan every day. If 50% took transit, Airport would be the busiest station on the system, by far. If 20% did, it would be the fourth busiest.
BLX is not needed with a cross harbor runnel. There is absolutely no reason for North Shore residents to go anywhere on BL except Logan and the CBD. The job density is non-existent and population density is mostly to the West of the ER.
The highest job density in the CBD is either near SS or along the BL, which will take the same time or less to reach than the present ER route, even with a transfer at Airport.
Have you ridden SL1 during rush? You would not be routing it's utility.
 

Tallguy

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Well, that was more of a hunch. That said, the broader point (admittedly not made all that clear in my post) is that regardless of whether it's more expensive to tunnel underwater than on land, it's unquestionably going to cost a hell of a lot more to make two tunnels than one.



Compared to what? The current alignment with the nasty speed restrictions plus a North Station-aligned NSRL? Just the North Station-aligned NSRL with the speed restrictions nuked through unspecified means?



Valid goal, but an extremely expensive way of doing it (because of all the tunneling). (Hunch alert:) Probably doesn't make it on cost-benefit analysis if that's the main purpose.



Well, we've transited to Crazy Transit Pitches here. I assume this would involve running the Eastern Route CR tunnel route through the old industrial track route (whether on the surface or not) via airport into this new tunnel, meeting up with the existing Eastern Route somewhere around Revere Beach Parkway? Freeing up the existing ER to that point? Does this hypothetical OL extension end at the Parkway? Somewhere past there (if the ROW's wide enough)?

Just to do that Orange branch at all, you'd need to nuke the Chelsea grade crossings (admittedly not quite as hard on HRT as on RR), and you'd have to do something about the bridge by the casino, because CSX has freight rights to the produce market, so wholesale-mode-swapping that stretch is impossible without CSX relinquishing its rights lest the feds obliterate you from orbit. Not to mention the numerous reasons given in numerous threads and never to my knowledge actually refuted with data by anyone about why branching the Orange Line isn't a great idea.

Is is possible to do? Yeah, probably. I have yet to see anything close to convincing as to why it makes sense to do this rather than the base 4-track NSRL. I suppose I could be convinced by data if it showed a massive problem if NSRL didn't have a good Blue Line connection (though the much-needed BLX to Lynn would link Blue and the ER) and if building Central Station on a CA/T alignment blew out the cost worse than doing this would. But, absent that, I don't see why two tunnels is better than one. (Especially since if you take the Chelsea-inbound ER off the RR mode for OL conversion, you're chaining everything ER to the tunnel, which doesn't make pair-matching any easier.)
Within 20 years, there will be nothing to deliver freight to in Everett /Chelsea. Development is already started and won't end until 40-50k people live and work there
And for the one train that goes there, a gauntlet track with a middle of the night run would do the job
 

Koopzilla24

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80-110 THOUSAND people fly in or out of Logan every day. If 50% took transit, Airport would be the busiest station on the system, by far. If 20% did, it would be the fourth busiest.
How many of those 80-110k are actually staying in Boston or coming from Boston as opposed to remaining in the airport or adjacent hotel for a connecting flight? I don’t disagree that better airport capacity and public transportations connections to Greater Boston are necessary.

BLX is not needed with a cross harbor runnel. There is absolutely no reason for North Shore residents to go anywhere on BL except Logan and the CBD. The job density is non-existent and population density is mostly to the West of the ER.
The highest job density in the CBD is either near SS or along the BL, which will take the same time or less to reach than the present ER route, even with a transfer at Airport.
Have you ridden SL1 during rush? You would not be routing it's utility.
There’s jobs and job opportunities further beyond the CBD into Boston that residents of North Shore communities, specifically Lynn, could benefit from a BLX. And the current BL is used for people along it to connect to the Orange and Green lines to places like Longwood. Lynn needs that rapid transit access with its population and proximity to Boston.
 

Tallguy

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80-110 THOUSAND people fly in or out of Logan every day. If 50% took transit, Airport would be the busiest station on the system, by far. If 20% did, it would be the fourth busiest.
BLX is not needed with a cross harbor runnel. There is absolutely no reason for North Shore residents to go anywhere on BL except Logan and the CBD. The job density is non-existent and population density is mostly to the West of the ER.
The highest job density in the CBD is either near SS or along the BL, which will take the same time or less to reach than the present ER route, even with a transfer at Airport.
Have you ridden SL1 during rush? You would not be routing it's utility.
The O
How many of those 80-110k are actually staying in Boston or coming from Boston as opposed to remaining in the airport or adjacent hotel for a connecting flight? I don’t disagree that better airport capacity and public transportations connections to Greater Boston are necessary.



There’s jobs and job opportunities further beyond the CBD into Boston that residents of North Shore communities, specifically Lynn, could benefit from a BLX. And the current BL is used for people along it to connect to the Orange and Green lines to places like Longwood. Lynn needs that rapid transit access with its population and proximity to Boston.
Are you unclear on the concept of Regional Rail?
 

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