Crazy Transit Pitches

[TheRatmeister]

For Fairmount Line in particular, I'm less worried. Commuter rail is already running, not to mention there's more than enough political will to push for more frequent service and electrification.

I'm not super worried, but it's a way to tank the project I hadn't thought of before and is certainly not out of the realm of possibility for political shenanigans.

 

[F-Line to Dudley]

I'm not super worried, but it's a way to tank the project I hadn't thought of before and is certainly not out of the realm of possibility for political shenanigans.

I wouldn't expect anything grand. They have, of course, already played their tank card for Fairmount: "discontinuous electrification". Backpedaling from electrifying the easiest-to-electrify line over magic BEMU pixie dust. It's transparently designed to fail.

 

[Riverside]

Buses can handle steeper gradients than light rail, making grade separation via over/underpasses easier

I'm going waaaaay back up-thread here, but I wanted to ask for more detail on this assertion. I was doing some quick looking comparing recommendations on LRT grades and bus grades and it looks like max LRT grades are typically 6% over a long distance and 7% over short, while maximum bus grades for 40-foot buses are typically "between 6% and 8%". Assuming that there are additional variables that further complicate those guidelines, those grades do not seem dramatically different?

I'm certainly well-outside my field of expertise here, so am hoping I can learn more!

 

[Tallguy]

Twin type 10s should be enough for the volume but you could run some triples in a Sullivan to Harvard shuttle if traffic warrants it

 

[F-Line to Dudley]

I'm going waaaaay back up-thread here, but I wanted to ask for more detail on this assertion. I was doing some quick looking comparing recommendations on LRT grades and bus grades and it looks like max LRT grades are typically 6% over a long distance and 7% over short, while maximum bus grades for 40-foot buses are typically "between 6% and 8%". Assuming that there are additional variables that further complicate those guidelines, those grades do not seem dramatically different?

I'm certainly well-outside my field of expertise here, so am hoping I can learn more!

Wheel slip can become an issue with rail at max grades, but that mainly manifests in an outdoor setting where the rails regularly get wet and/or accumulate wet leaves. Electric buses are the best vehicle type out there for handling maximally steep grades, which is why very hilly cities tend most to have trackless trolley systems. Diesels/hybrids are kinda sucky at hills, though.

For design of grade separations the difference between modes is nil. You're almost never going to see designers push it to the absolute outer limits if they can avoid it, because it does negatively impact performance on any mode and those performance demerits affect overall throughput. We wouldn't be designing bottlenecked grade separations on BRT or LRT.

 

[TheRatmeister]

Wheel slip can become an issue with rail at max grades, but that mainly manifests in an outdoor setting where the rails regularly get wet and/or accumulate wet leaves. Electric buses are the best vehicle type out there for handling maximally steep grades, which is why very hilly cities tend most to have trackless trolley systems. Diesels/hybrids are kinda sucky at hills, though.

For design of grade separations the difference between modes is nil. You're almost never going to see designers push it to the absolute outer limits if they can avoid it, because it does negatively impact performance on any mode and those performance demerits affect overall throughput. We wouldn't be designing bottlenecked grade separations on BRT or LRT.

That's about what I found as well. I don't think that really changes my overall conclusion about a local busway network being the preferred solution, with cross-city service provided by some form of heavy rail.

 

[Teban54]

Which leads me to the question of residential vs commercial areas. If this were 2019, I'd say mainly commercial areas, obviously stopping at residential areas along the way. But things have changed with WFH taking off, way fewer people are making "traditional" commutes downtown for 9-5 office jobs, and this is probably a trend that will continue going forward. With that in mind, I think new transit should primarily focus on bringing people to recreational, shopping, and other residential areas.

Not to mention business areas are disproportionately wealthy, and you very much run the risk of creating a transit line for rich people and leaving everyone else behind, which is... Not great.

Coming back to this, the problem is that:

a) Seaport is as much of a shopping district as it is a commercial one. Go there on weekends and you'll see tons of people shopping near Courthouse station that almost feels like Newbury.

Here's Fall 2022 ridership data for all of SL1/2/3/W, showing only total boardings during the specified periods:

Section	Entire route	Courthouse	WTC	SLW
Weekday all day	16065.5​	1654.9​	1170.5​	1334.6​
Saturday	11243.9​	1076.9​	697.2​	882.1​
Sunday	10143.3​	938.4​	659.6​	791.3​
Weekday peak	5685.6​	661.7​	465.9​	463.2​
Weekday off-peak	10379.9​	993.2​	704.6​	871.4​
AM peak outbound	1436.9​	70.7​	35.3​	42.6​
AM peak inbound	1158.7​	78.9​	102.9​	97.4​
PM peak outbound	1380.7​	120.4​	72.6​	113.8​
PM peak inbound	1709.3​	391.7​	255.1​	209.4​

% of Saturday ridership over weekday is 70% on the entire SL Waterfront system, and 65% for Courthouse. That's pretty close to the systemwide average of 59% for all bus routes, and 72% for a few key bus routes that I selected (detailed below). Seaport is almost certainly not a ghost town on weekends.


b) The main employment centers we're talking about for an "Urban Ring" are exactly the ones that are less affected by WFH. Kendall (biomedical labs), LMA and BUMC (hospitals), Logan Airport, MIT/BU (universities, and Harvard if we wanna go there), and even Seaport will have people shopping and dining as I mentioned. Their transit needs won't be reduced nearly as much as the Financial District. This is shown with data for the CT2 bus - see below.


c) Even ignoring the two points above - in a post-Covid world, even though weekend and off-peak ridership decreased less compared to rush hours, they're nowhere near the point of outweighing traditional travel patterns (yet).

I compared Fall 2019 and Fall 2022 riderships for the entire bus system, a few key bus routes* (1, 28, 39, 66, 77, 111, 116), and CT2 - the closest to an Urban Ring that we have:

Routes	Systemwide	7 key bus routes	CT2
% of '22 ridership to '19	71.14%​	78.13%​	72.00%​
% of '22 weekday ridership to '19	69.40%​	77.01%​	72.00%​
% of '22 Saturday ridership to '19	80.28%​	81.32%​
% of '22 Sunday ridership to '19	83.29%​	85.27%​
% of '22 peak-hour ridership to '19	62.96%​	72.61%​	76.67%​
% of '22 off-peak ridership to '19	73.58%​	79.20%​	67.96%​
19, % Saturday to weekday ridership	51.01%​	67.75%​	0.00%​
22, % Saturday to weekday ridership	59.00%​	71.55%​	0.00%​
19, % Sunday to weekday ridership	33.28%​	48.69%​	0.00%​
22, % Sunday to weekday ridership	39.94%​	53.91%​	0.00%​
19, % off-peak to peak ridership	154.31%​	199.90%​	115.68%​
22, % off-peak to peak ridership	180.34%​	218.05%​	102.55%​

(*) I initially did a line-by-line analysis, so I didn't include all key bus routes even though I probably should have. This means the key bus routes data were pulled up somewhat by the 28 bus, which benefitted from the free fares trial.

Yes, weekend ridership fares much better than the traditional weekday peak-oriented ridership in the 19-to-22 comparison, but in terms of absolute numbers, the latter still dominates. In both 2019 and 2022, Saturdays only see 2/3 of ridership compared to weekdays, and Sundays only has 1/2 or less. (Granted, some of that is due to poor service levels, but similar conclusions hold for key bus routes which have good service on weekends.) Your "way fewer" commute crowd still generates 63% of bus ridership compared to pre-Covid, and while that number is outperformed by weekends, it's really not as big of a difference as you expected.

While this certainly justifies paying more attention to off-peak, recreational travels (and ensuring quality service for these trips at off-peak hours), I think it's premature to focus "primarily" on those trips rather than established commute patterns. Don't forget, there are 5 weekdays out of 7 in a week, still.

The CT2 comparison also shows it suffered less significantly from WFH (and GLX Union Square). In fact, its peak-hour ridership retention rate is above the system average. This is in stark contrast to other peak-oriented routes like the 7, which only sees ~50% of 2019's ridership. This further shows that demand along the nodes that it connects, notably Kendall and Longwood, are still worth serving post-Covid.

 

[ritchiew]

Is it really the ideal urban ring route? Going a bit further out, more following the 66 route, could allow for areas like Allston to be included.

Digging up this bit of the conversation, I'd still like to see exactly why the #66 bus route was rejected. But one big knock against it, that I don't think got mentioned here, is just that you'd have to build a subway through Brookline. The politics of that seem... impossible. Like, if a GJ route and a #66 route were both comparably beneficial, the #66 route wouldn't really be an option just because of Brookline politics. You'd have to make the case that the costs are so much lower or the benefits so much higher before a Brookline routing becomes feasible.

Just thinking about it this morning while reading the Spotlight article on Brookline's long history of exclusionary zoning.

Brookline homes: One wealthy liberal town reckons with its past

Brookline broadcasts an ethos of inclusivity, but it has become a preserve for the privileged. This is no accident, but the fruit of decades of exclusionary actions. Now facing a state mandate to allow more multifamily housing, Brookline faces a choice: What kind of town does it want to be?

apps.bostonglobe.com

 

[TheRatmeister]

Moving away from an orbital rail route to what I'd say the "Urban Ring" project was actually aiming for, here's a map I threw together that imagines if key bus corridors that mainly run along wide streets were operated as median-running light rail instead, perhaps with small amounts of mixed traffic running to fill in a few gaps here and there. If you kinda squint it looks like a ring, but that's really not what it's meant to be used for. You can see the routes and interact with the map here. Let me know if you think there's any big corridors I've missed. Here's ones I wanted to include or considering including but opted not to:

• Ashmont-JFK via Gallivan and Morrissey: I felt like it paralleled the RL too much and didn't serve a huge purpose
• American Legion Hwy: Mainly strip malls and big box stores, not a great route without major redevelopment
• Hyde Park Ave: Mostly too narrow, also generally parallels the CR, why not just improve that?
• Washington St (Brighton): Again, too narrow. If all the street parking is removed then maybe it's possible but good luck with that. That one can go in the god-mode thread for now.
• Mass Ave north of Harvard Sq: Again felt like it paralleled the RL too much to make sense
• Blue Hills Pkwy south of Mattapan: If Milton really wants it they can pay for it, but we all no that's a no and a no.
• Talbot Ave: Again, slightly too narrow, would require removing all the street parking
• The 66: Even with all the street parking removed it would still likely require mixed traffic running, and lots of the street parking removal would need to happen in Brookline, see previous post in this thread.

One last note: What separates rapid transit lines from streetcar/tram routes? In my mind, it's one word: Frequency. Rapid transit lines should provide 10m headways or lower on an extended, cohesive corridor, rather than achieving this with merging many services onto a shorter trunk route. That's why Columbus Ave doesn't get to be a rapid transit line on this map. As you can see on the map however, rapid transit style LRT service can certainly coexist with a local streetcar service, I think BHA is an excellent example of where this makes sense.

 

[bigeman312]

One last note: What separates rapid transit lines from streetcar/tram routes? In my mind, it's one word: Frequency.

Grade separation, speed, capacity, dedicated right-of-way, infrastructure, distance between stations, vehicle size, network scale.

 

[Tallguy]

The only way to feasibly build a radial connector is to use existing ROW as much as possible and integrate it with existing LRT. Try to pay for tunnelling in BV and to Nubian from Ruggles

 

[TheRatmeister]

Grade separation, speed, capacity, dedicated right-of-way, infrastructure, distance between stations, vehicle size, network scale.

Well if we're talking about the subway lines sure, but what about the surface GL branches? Why do they get a color on the map but Columbus Ave doesn't?

 

[bigeman312]

One last note: What separates rapid transit lines from streetcar/tram routes? In my mind, it's one word: Frequency.

Well if we're talking about the subway lines sure, but what about the surface GL branches? Why do they get a color on the map but Columbus Ave doesn't?

This is a terminology mix-up.

Rapid transit or mass rapid transit (MRT), also known as heavy rail or metro, is a type of high-capacity public transport that is generally built in urban areas. A rapid transit system that primarily or traditionally runs below the surface may be called a subway, tube, or underground.[1][2][3][4] Unlike buses or trams, rapid transit systems are railways, usually electric, that operate on an exclusive right-of-way, which cannot be accessed by pedestrians or other vehicles.[5] They are often grade-separated in tunnels or on elevated railways.

The three rapid transit lines in the MBTA system are the Red, Orange, and Blue Lines.

Light rail transit (LRT) is a form of passenger urban rail transit characterized by a combination of tram and rapid transit features. While its rolling stock is similar to a traditional tram, it operates at a higher capacity and speed, and often on an exclusive right-of-way. In many cities, light rail transit systems more closely resemble, and are therefore indistinguishable from, traditional underground or at-grade subways and heavy-rail metros.

The MBTA’s Green Line is what’s known as light rail. In fact, it and the Mattapan Trolley constitute the third most heavily used light rail system in the country.

A tram (called a streetcar or trolley in USA) is a rail vehicle that travels on tramway tracks on public urban streets; some include segments on segregated right-of-way.[1][2][3] The tramlines or networks operated as public transport are called tramways or simply trams/streetcars. Many recently built tramways use the contemporary term light rail.

In Boston, the most prominent tram/streetcar lines that remain in use are parts of the Green Line, which operates on the surface and underground, functioning as both a streetcar and a rapid transit line in different sections.

The Green Line is integrated into the rapid transit system and sometimes functions as rapid transit in underground sections. Therefore, locally we often refer to these four colors as the rapid transit system, it’s important to know what the term rapid transit refers to when speaking about systems in general. The Orange/Red/Blue lines are heavy rail (you’ll see people on this site abbreviate them and the like to HRT), while the Green Line is light rail (which you’ll sometimes see abbreviated to LRT on this site).

Back to the mix-up:

Well if we're talking about the subway lines sure, but what about the surface GL branches? Why do they get a color on the map but Columbus Ave doesn't?

The “surface GL branches” are not rapid transit nor do they function as rapid transit (except arguably, the GLX, but that doesn’t appear to be what you’re referring to). Rather, it’s light rail, with only one (the Green Line E branch) running regular service on an undivided street. One could use the term streetcar/tram when referring to this section.

So, like I said, there are many words that can be used to describe the difference between streetcars/trams and rapid transit (also known as metro or heavy rail): grade separation, speed, capacity, dedicated right-of-way, infrastructure, distance between stations, vehicle size, network scale.

I hope this helps and I know this terminology can be tricky, nuanced, and have overlap.

 

[TheRatmeister]

This is a terminology mix-up.

Rapid transit or mass rapid transit (MRT), also known as heavy rail or metro, is a type of high-capacity public transport that is generally built in urban areas. A rapid transit system that primarily or traditionally runs below the surface may be called a subway, tube, or underground.[1][2][3][4] Unlike buses or trams, rapid transit systems are railways, usually electric, that operate on an exclusive right-of-way, which cannot be accessed by pedestrians or other vehicles.[5] They are often grade-separated in tunnels or on elevated railways.

The three rapid transit lines in the MBTA system are the Red, Orange, and Blue Lines.

Light rail transit (LRT) is a form of passenger urban rail transit characterized by a combination of tram and rapid transit features. While its rolling stock is similar to a traditional tram, it operates at a higher capacity and speed, and often on an exclusive right-of-way. In many cities, light rail transit systems more closely resemble, and are therefore indistinguishable from, traditional underground or at-grade subways and heavy-rail metros.

The MBTA’s Green Line is what’s known as light rail. In fact, it and the Mattapan Trolley constitute the third most heavily used light rail system in the country.

A tram (called a streetcar or trolley in USA) is a rail vehicle that travels on tramway tracks on public urban streets; some include segments on segregated right-of-way.[1][2][3] The tramlines or networks operated as public transport are called tramways or simply trams/streetcars. Many recently built tramways use the contemporary term light rail.

In Boston, the most prominent tram/streetcar lines that remain in use are parts of the Green Line, which operates on the surface and underground, functioning as both a streetcar and a rapid transit line in different sections.

The Green Line is integrated into the rapid transit system and sometimes functions as rapid transit in underground sections. Therefore, locally we often refer to these four colors as the rapid transit system, it’s important to know what the term rapid transit refers to when speaking about systems in general. The Orange/Red/Blue lines are heavy rail (you’ll see people on this site abbreviate them and the like to HRT), while the Green Line is light rail (which you’ll sometimes see abbreviated to LRT on this site).

So, like I said, there are many words that can be used to describe the difference between streetcars/trams and rapid transit (also known as metro or heavy rail): grade separation, speed, capacity, dedicated right-of-way, infrastructure, distance between stations, vehicle size, network scale.

I hope this helps and I know this terminology can be tricky, nuanced, and have overlap.

The problem is that there is a general definition of "Rapid Transit" and a Boston definition of rapid transit. In the Boston definition, the GL and SL count, and that's what I'm referring to here. Whether or not that's right is a different question, but from the perspective of the MBTA they are "Rapid transit lines." I'm talking about the difference between the colored lines, generally referred to as "Rapid transit" whether they are or aren't, and local bus/streetcar/tram routes.

 

[bigeman312]

The problem is that there is a general definition of "Rapid Transit" and a Boston definition of rapid transit. In the Boston definition, the GL and SL count, and that's what I'm referring to here. Whether or not that's right is a different question, but from the perspective of the MBTA they are "Rapid transit lines." I'm talking about the difference between the colored lines, generally referred to as "Rapid transit" whether they are or aren't, and local bus/streetcar/tram routes.

You lose me at this:

a Boston definition of rapid transit. In the Boston definition, the GL and SL count

Ultimately, this is a semantic debate and not super interesting. But if you polled archboston about whether the Silver Line constitutes “rapid transit” with respect to following:

What separates rapid transit lines from streetcar/tram routes?

you would get an overwhelming consensus that the Silver Line does not fit that term. Rather, it would be referred to as a series of bus routes, or if we’re being very generous, as bus rapid transit (BRT).

Ultimately you can use whatever words you want in whatever way you want. But using these terms the way they are understood both generally and by those reading this forum will help you be understood better. Over my decade of being way too active on this board I’ve often thought that having a terms and abbreviations reference page would be helpful. That’s all I was trying to help with.

If you don’t want to use these terms in the same way they are generally used and understood, it’s your prerogative and no big deal to me. You may run into more of these confusions, though. I enjoy reading your posts, nonetheless, and welcome to this forum! I hope you remain an active contributor for years to come.

Have a nice day!

 

[TheRatmeister]

And Seaport is primarily a destination node, not a neighborhood. Using Fall 2022 data, during AM peak on an average weekday across all of SL1/2/3, Courthouse station sees 368.1 alightings outbound, but only 65.5 boardings inbound. (SL3 alone from Chelsea and Airport drops off 69.1 passengers.) The same applies to WTC, though the contrast is less extreme (outbound offs are 2x inbound ons).

South Boston obviously needs better transit options (the 7 bus was probably the most frequent route during AM peak pre-Covid), but my hypothesis is that it's better served with light rail that's largely along the proposed T7 route (and possibly T9 too).

This has stayed on my mind so I've gone and pulled up the Fall 2022 data to compare Southie and Seaport in terms of bus ridership per week. Here's the breakdown for seaport:

	Boardings	Alightings
SL1/2/3/W (Including Drydock)	10871.1	11626.9

And Southie:

	Boardings	Alightings
7	1285	1007.2
9	4048.6	3388.7
10	1372.1	1446.5
11	1580	1195
Total	8285.7	7037.4

So given these numbers, I think one conclusion that can be drawn is that despite headways of 20+ minutes on local bus routes compared to routes with 10 minute headways on an underground, grade-separated ROW, boardings on the Silver Line to Seaport are only ~30% higher. There's a bigger difference in alightings, which might be caused by people ride-sharing back to Southie in the evening rather than taking public transit, and by originally getting to Seaport by walking from South Station, though it's unclear. I think with further development of industrial areas and changes to zoning in Southie, along with improved transit service, it's far from unreasonable to say that Southie might provide more ridership than Seaport to a hypothetical urban ring, although a proper study would be necessary to actually look into this rather than make guesses from bus ridership.

 

[BosMaineiac]

This has stayed on my mind so I've gone and pulled up the Fall 2022 data to compare Southie and Seaport in terms of bus ridership per week. Here's the breakdown for seaport:

	Boardings	Alightings
SL1/2/3/W (Including Drydock)	10871.1	11626.9

And Southie:

	Boardings	Alightings
7	1285	1007.2
9	4048.6	3388.7
10	1372.1	1446.5
11	1580	1195
Total	8285.7	7037.4

So given these numbers, I think one conclusion that can be drawn is that despite headways of 20+ minutes on local bus routes compared to routes with 10 minute headways on an underground, grade-separated ROW, boardings on the Silver Line to Seaport are only ~30% higher. There's a bigger difference in alightings, which might be caused by people ride-sharing back to Southie in the evening rather than taking public transit, and by originally getting to Seaport by walking from South Station, though it's unclear. I think with further development of industrial areas and changes to zoning in Southie, along with improved transit service, it's far from unreasonable to say that Southie might provide more ridership than Seaport to a hypothetical urban ring, although a proper study would be necessary to actually look into this rather than make guesses from bus ridership.

I recall some sketches being posted previously in this board of an alternate urban ring route that would loop over to Broadway from Albany St/Mass Pike. The route could utilize the old trolley tunnel, then somehow hop over to the Bypass route into Seaport. This routing would make a lot of sense as you can reuse a lot of old ROW with minimal new tunneling. I’ll try and find it.

However, the Bypass route has a lot of value for vehicular traffic, so ripping that up in favor of more rail would need some analysis so Southie streets don’t get more crowded (maybe most traffic can instead go through the TWT to seaport). I also would like to see a reactivated rail connection one day to the port and maybe even Conley, so that should be preserved and I believe it has to due to an agreement with CSX.

This also begs the question, if we already have a tunnel to the seaport, what’s the point of digging another one? I agree that Southie needs better transit, but most of that will probably be following the 7 and 9 routes, to FiDi and Back Bay, respectively. I would think a short hop on a BRT-ified T7 would be a sufficient route to the Urban Ring for most east side southie riders. And for west side a functioning red line will be plenty enough for the one stop to SS to catch it.

Remember, the Seaport is about half developed. We are far more likely to see dense development in that district than southie proper, where the neighborhood is low rise/less dense.

 

[BosMaineiac]

It's 11pm on a Friday night, which means it's time to draw some lines on maps.

None of these ideas have been examined critically at all.

Setting aside a second surface route, let's instead think about building a subway to Nubian. A couple points for our consideration:

1) No matter how you do it, it will be expensive. Whether it's dealing with landfill or undocumented utilities or deep bores or unhappy residents, the cost will be high.

2) The number one goal is to run trains quickly and frequently from Nubian to downtown. A nice number two goal would be serving BU Medical Center.

3) Local service on Washington St is explicitly out of scope and can be handled via a shorter surface route.

Earlier in the week we were chatting about tunneling under Harrison. But what if we looked further east, and instead tunneled under Albany and 93? (You could maybe also save on tunneling costs by running in an open cut under 93.)

View attachment 32432

Believe it or not, this is only a quarter mile longer than a Washington St alignment. And I would argue that you could get away with having only two intermediate stations (e.g. at the southern and northern ends of BUMC), or maybe even only one. 2 miles of running track is equivalent to Beaconsfield to Longwood, which is timetabled at 7 min with two intermediate stops. So an alignment like this could potentially compete with the travel times of the El.

If we don't feel like pissing off the hospitals by tunneling outside their front door, we could piss off everyone else and tunnel under a combination of Melnea Cass, the Mass Ave Connector, BioSquare Dr, and 93:

View attachment 32433

Even with potential cost savings from tunneling under the highway, this would still be a mammoth of a project, with a cost to match. I think it's possible that one could make a case for positive impact across the Green Line network (i.e. more than just positive impact for Nubian riders), but it's still probably a tall order.

But what if we can up the ante? What if, in addition to giving Nubian a speedy one-seat-ride downtown, we also provided a key piece of infrastructure to enable a southside LRT Urban Ring linking Nubian (and potentially beyond) with the Seaport?

View attachment 32434

Cut across to Broadway (somehow -- yes, big question mark here) and then cut across to South Boston Haul Road (yes, another big question mark here) and then run to the Seaport in the open cut of the current South Boston Haul Road. For less than half a mile of additional tunnel, you've built a fifth of an LRT Urban Ring. At that point, all you need to do (and it's definitely still a tall order, but all the same) is build a ~1 mile cut-and-cover subway between Huntington and Nubian, and then you have two full length circumferential LRT lines in dedicated ROWs originating at opposite ends of Longwood.

(Yes, this still doesn't solve the problem of getting across Longwood. But you can bet your CharlieCard, a Longwood West <> Cambridge <> Sullivan <> Airport line and a Longwood East <> Nubian <> Seaport line would be pretty fricking awesome on their own.)

Building a Nubian-Downtown subway that also can be used by the Urban Ring massively expands the scope of its impact. It would also massively expand the constituency that could lobby for it -- now this isn't just about expanding transit access for Dorchester, it's about linking together major employment centers (blah blah blah -- yes, I'm pointing out that this approach would bind together the fortunes of both wealthy and poor Bostonians, and it never hurts to get major institutions like Harvard, MGH/Brigham, and BU on your side).

In the name of crayoning perfectionism, I should acknowledge that, theoretically, you could utilize the Back Bay-South Station subway to connect the Urban Ring to the Seaport:

View attachment 32435

But to do that you'd need to tunnel under all of this, and also fit a flying junction of some kind into your alignment along Hudson St, which is already a finely threaded needle:

View attachment 32436

Of course, it's possible that cutting underneath the maintenance yards between 93 and Broadway will in fact be even hairier, so who knows.

tl;dr: Building a subway to Nubian will be Very Expensive no matter how you do it, so let's find a way to make it do more than "merely" connect Nubian with downtown -- if you're gonna Go Big, then you should properly Go Big.

Copying Riverside’s post from Green Line Reconfiguration, who drew the southie urban ring idea up nicely

 

[Riverside]

I recall some sketches being posted previously in this board of an alternate urban ring route that would loop over to Broadway from Albany St/Mass Pike. The route could utilize the old trolley tunnel, then somehow hop over to the Bypass route into Seaport. This routing would make a lot of sense as you can reuse a lot of old ROW with minimal new tunneling. I’ll try and find it.

Thanks for the shout-out!

However, the Bypass route has a lot of value for vehicular traffic, so ripping that up in favor of more rail would need some analysis so Southie streets don’t get more crowded (maybe most traffic can instead go through the TWT to seaport). I also would like to see a reactivated rail connection one day to the port and maybe even Conley, so that should be preserved and I believe it has to due to an agreement with CSX.

Very much theoretically, it shouldn't be necessary to rip up the Bypass.

There are two sections of this corridor, divided by West 2nd St (indicated with the red marker in the screenshot below):

The northern half is more industrial and a significantly less constrained ROW. So I'm not worried about that.

The southern half is a little more complicated, but still should be doable. By my read, the ROW is pretty consistently about 60' wide, which should be enough room for a 2-track LRT ROW (25'-30') and a two-lane road (30'-35').

There are two asterisks. First, as you mention, there is value in maintaining a freight track to the Seaport. Absent a RiverLINE-style timeshare, there won't be enough room for a third track for freight. This could be solved by a short tunnel underneath the existing ROW; this ROW has been rail for something like 150 years (cool map here and another cool map here), which would hopefully mean that many fewer surprise utilities. Plus, the cut-off between the southern half and northern half conveniently aligns pretty closely with Southie's original shoreline (map courtesy of National Geographic), which means less tunneling through fill:

But that brings us to our second asterisk: you're gonna need to build a tunnel anyway to jump from Broadway station to Track 61:

Orange - West 4th Street: continue south from the old streetcar tunnel at Broadway, and emerge through a portal within the Track 61 ROW. About 900 feet of tunnel, plus whatever you do under 970 feet of Track 61 (up to 1870 feet total)

Purple - West Broadway: similar to West 4th Street, but less roundabout and probably requiring a partial reconfiguration of Broadway Upper. About 960 feet of tunnel, plus whatever you do under 620 feet Track 61 (up to 1580 feet total)

Blue - West 2nd Street: reutilize the portal at Broadway but otherwise essentially build a new station there and then continue directly to the northern half of Track 61, about 1200 feet of tunnel total

Crimson - magic: use a TBM (plus a C&C launching tunnel under Silver St) to reuse as much of the existing station as possible and then take a more direct hypotenuse route to the northern half of Track 61, also about 1200 feet

So, to me, the two questions become, do you want to maintain freight service, and do you want to reuse Broadway Upper? Depending on those priorities, one of the above alts will probably shake up as the most cost-effective.

If you don't care about maintaining freight service -- or if you're willing to sacrifice the road in favor of a freight track -- then the West 4th St alignment is the least tunneling and should fully reuse Broadway Upper.

 

[WarpedReality]

How crazy would it be to consign freight movements on track 61 to street running along the bypass road? Is traffic on that road heavy? How frequently would freight trains travel that way?