If You Were God/Goddess | Transit & Infrastructure Sandbox

With modern concrete viaducts elevated transitways are actually pretty nice imo (vancouver skytrain comes to mind) and it gives riders an amazing elevated view over the city that is a million times more enjoyable than riding in a dark subway tunnel. I know Boston has an aversion to elevated lines due to the past experience with 20th century creaky, rusty, shadowy, elevated lines screeching through neighborhoods, but hopefully now that new examples like seattle or even glx through east cambridge are built peoples minds will start to change.

That being said where do you see a highway in the Boston area that would even need an elevated transit line? The pike and 93s already have lines running next to them which would be better served by electric multiple units for regional rail. Rt1 passes under the harbor so that would be more trouble than its worth. Rt2 starts right at the end of alewife station, but the minuteman right of way already exists next to it with a better catchment area. That really only leaves 93 north past assembly and the i95 beltway. I guess you could also throw in 203 + the arborway and jamaicaway as an inner belt line light rail.

-93 north past assembly would follow pretty close to glx with one half of its catchment area taken up by the mystic river, before turning into downtown medford, and then pretty quickly hitting the fells reservation. Not the greatest use of limited resources though hitting downtown medford would definitely be a huge improvement, so overall not the greatest but not completely bad either.

-i95 beltway would be a massive upgrade to the system, but would only be viable as an electric multiple unit line after regional rail/electrification is implemented. This would make the most sense imo being electric multiple units acting as a node of regional rail due to the long distance and spaced out stations.

-203, arborway, jamaicaway light rail could be an inner belt line that could use elevated viaducts along 203 up to about blue hill ave and then median running through the arborway. This isnt a real “highway” though so it would receive enormous pushback and would have almost no chance of happening.

Is there anything else that sticks out that would make sense for building an elevated transit line next to a highway? It seems that there really arent any obvious options that could be taken advantage of, that dont already have some sort of existing line or a duplicate line close by. I would love to see a radial regional rail line built along i95 at some point way into the future, but thats really outside of the scope of what the premise was of an elevated rapid transit line along a highway.
Late to the conversation, but I wonder if there's any (God-mode) way of using part of the I-93 South ROW for double-tracking of the Old Colony lines, at least before Neponset. Maybe even all the way to Braintree if we forgo Regional Rail at Quincy Center.
 
Late to the conversation, but I wonder if there's any (God-mode) way of using part of the I-93 South ROW for double-tracking of the Old Colony lines, at least before Neponset. Maybe even all the way to Braintree if we forgo Regional Rail at Quincy Center.
Boston MPO had a really, really stupid study of this in 2012: https://www.ctps.org/data/pdf/studies/highway/se_expr_concept.pdf. Put both the Braintree Branch and CR tracks in tunnels at the point of maximum pinch at Savin Hill, mashed JFK/UMass down to 1 Red island platform with a nuked Columbia Jct. (doesn't even show how the Cabot Yard leads would interface anymore) and new branch split halfway between Savin Hill, and extended the HOV zipper lane into South Boston. Pornographic cost because of all that would have to be blowed up to widen the highway, and such a naked highway capacity grab that it basically can't be taken seriously.

There are probably some elements of that plan that can be scraped and refashioned sans the add-a-lane insanity, but they need to go back to the drawing board and re-study this as a primarily multimodal transit project...not a highway project with transit afterthought. I don't think a flat Red Line junction at Clayton St. with the mainline running through Savin Hill Station is going to work with Red's 3-minute headway target...that's creating too huge a singular chokepoint. So there'll probably need to be a flying junction, though it's up for debate exactly how much of Red between Columbia Jct. and Savin Hill is compactable. Just double-tracking the JFK CR platform in isolation (by taking a slice of the inner busway) would be a large capacity increaser for being able to stage opposite-direction meets at the station, and can be done in isolation at modest expense.

In Quincy you wouldn't have to eliminate every single-track segment to net :30 Regional Rail frequencies to Greenbush, Plymouth, and Middleboro/Cape. TransitMatters' Regional Rail Modernization report showed that fixes for (1) Dorchester pinch, (2) JFK Station DT, and (3) Quincy Center Station DT would allow enough headroom to pulse full-blast Regional Rail frequencies to all 3 branches. While that TM report had many many flaws on the individual branches, it was fairly reasonable in scope for mainline improvements. The only things you can't readily have with the Wollaston and Quincy Adams stretches left as single are Regional Rail service levels with the South Coast branches still attached because the meets would get too brittle, or a means of pulsing up :15 minute service to Brockton. That's where the tactical nuclear strikes at Wollaston and along Burgin Pkwy. have to come into play (although, honestly a lane-drop of Burgin might be a feature not a bug). So the focus in Quincy is in digging a turnout under the station such that the current tunneled side platform becomes an island...not terribly expensive to do.
 
Here's my MS Paint series on how to fix the Dorchester pinch with no flow demerits to the Red Line.

#1. Haul Road to Southampton St. area: https://goo.gl/maps/ks2h5KP9RV3KiR9F9
The OC is single-track here because of a messy track layout. Between Southampton St. and Boston St. the Amtrak Southampton Yard runaround track (RR track) lies closest to 93, then the 2 Cabot Yard lead tracks (Red Line) are in the middle, then the OC (RR track) is on the outside. So you've got a 4-track ROW, but the 2 RR tracks are disconnected and on the outskirts and kinda useless. We have to flip the Red Line leads to the east side, claiming a redundant access point to Track 61...then let it rejoin its original alignment into Cabot at the truss bridge next to Southie Bypass Rd. (Track 61 is still accessible by RR from a second access point underneath the truss bridge). This consolidates the RR tracks passing through Southampton Yard, slightly expanding the yard, and hooks the currently dead-end Amtrak runaround into the OC mainline.

(No render for this one, but you can see the track layout easily enough on the Google link and we're just swapping berths.)



#2. Southampton St. to Dorchester Ave area: https://goo.gl/maps/mhwVQRuP77QrFe8BA
The "flip" for doing the berth-swapping by modes discussed in #1. Cabot leads do a quick duck-under of the Old Colony to switch sides for the ride through #1. Boston St. overpass slightly widened for 4 tracks, trading a small crabgrass embankment along 93 for a new concrete retaining wall. Note that the route of the RL subway curves out from under Boston St. towards the portal. At Dot Ave. we slightly compact the RL leads (which are currently 3-track) to free up a +1 berth for the OC.
OC1.png




#3. Dot. Ave. thru Columbia Jct. area: https://goo.gl/maps/u2bmf13KjBFNXCHt8
The sprawl of Columbia Jct. is massively compacted to create room for the second OC track. The Cabot leads become branch tracks at the portal crossovers, and simple split/recombine crossovers do the branch splitting (the revenue tracks are still grade separated even though the junction has been flattened). RL track assignments into JFK change as indicated to reflect the junction-flattening: Braintree grabs the two middle tracks, Ashmont the outer tracks. The 2 outbound tracks and 2 inbound tracks are now grouped together.
OC2.png




#4. JFK Station area: https://goo.gl/maps/2gVRKcimx53iYG1x7
(Note: platforms/concourses are approximate and not to scale.)
Red Line platforms are kept as-is, but the track assignments change as indicated. ALL outbound service is now on the former Ashmont platform, and ALL inbound service is now on the former Braintree platform...making wayfinding enormously easier. The innermost busway is re-sculpted to turn the Commuter Rail platform into a 2-track island. Room exists underneath I-93 to thread the 2nd track south of the station. Some compacting of Old Colony Ave. commensurate with a reconfig of that awful Columbia rotary is necessary on the north side of the station.
OC3.png




#5. Savin Hill area and the "Braintree subway": https://goo.gl/maps/5Md8ghn2JL6Ec8YVA
We build a shallow Wellington tunnel analogue to sink the center-running Braintree tracks underneath the outer Ashmont tracks, which will ride the bare tunnel roof on the current Ashmont Branch alignment. Note that this will be significantly less expensive than a cut-and-cover subway, since it is just a capped cut. RL utilities (which are currently duplicate for each branch through Savin Hill) are consolidated "upstairs/downstairs" on the new structure. At Savin Hill the current station and platforms (Note: platforms and egresses not to scale) are left completely stet, and the tunnel curves away from the station foundations. The Old Colony's 2 tracks take up the deleted surface berths, and ride the bare tunnel roof when it curves away from the Savin Hill platform. 1 fewer track will ride along the I-93 retaining wall than before, meaning some space can be reclaimed for breakdown lanes on the highway.
OC4.png


OC5.png




#6. Freeport St. area and back on-alignment: https://goo.gl/maps/vPA8D7wBRK1JJDu16
When I-93 pulls away the tunnel shifts again to get on-alignment for the Braintree surface route, then portals up. The Freeport St. rail bridge is widened by 1 track berth so the middle OC tracks can be doubled-up (embankments manicured with retaining walls accordingly), but otherwise everything is back to its current alignment. Ashmont Branch pulls away at Clayton St. as today, Braintree Branch continues stet. Further downstream the Park St. rail overpass would be widened by +1 track berths, and the embankment on the OC side would be re-braced for about 1500 ft. by retaining wall to tie the extra track into the current double-track switch right before Victory Rd.
OC6.png




Thus, the Dorchester pinch is healed. Again...this is the DO NO HARM alternative that preserves 100.00% of the Red Line's current capacity on a smaller footprint. With wayfinding improvements to the chaotic JFK platform configuration. YMMV on traffic modeling trying to do 2-track RL solutions through JFK, other forms of flying junctions, or (God forbid) rolling the dice with conflicting movements on a Copley-style flat junction. But a lot of Columbia Jct. is unnecessary sprawl that can be deleted, and the tunneling around Savin Hill won't be expensive because of the capped cut.
 
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Is there any way to move the Braintree/Ashmont junction to be south of Savin Hill? If there were only 2 Red Line tracks at Savin Hill, it means one would only need 2 RL tracks all the way from Andrew to Savin Hill, meaning there would be no need for a Braintree branch tunnel.

Is there a problem having Braintree trains use the Ashmont tracks from Savin Hill? Does the existing Ashmont/Braintree Junction have enough space?

1684022161470.png
 
Is there any way to move the Braintree/Ashmont junction to be south of Savin Hill? If there were only 2 Red Line tracks at Savin Hill, it means one would only need 2 RL tracks all the way from Andrew to Savin Hill, meaning there would be no need for a Braintree branch tunnel.

Is there a problem having Braintree trains use the Ashmont tracks from Savin Hill? Does the existing Ashmont/Braintree Junction have enough space?

View attachment 37873
  • The traffic modeling is a dicey proposition trying to mash it all into 2 tracks. Braintree Branch becomes more imbalanced having to pick up Savin Hill, and you may not have the bandwidth to drop an infill around Neponset doing that. And Red's overall resiliency takes a hit no longer having the Cabot leads tie into the 4-track segment. It could work in theory, but it also could not.
  • Savin Hill is the least-dense stop on Red, so wouldn't benefit much from the 3-minute mainline headways in spite of it complicating Braintree's scheduling. Very low-leverage play.
  • It would have to be some sort of grade-separated junction, because a totally flat (Copley Jct.-style) junction would be conflict-city at 3-minute headways with zero resiliency. On your render that would be very hard to shiv in around the residential abutting Clayton St. split. The 2012 MPO study did a flying junction past Savin Hill, but it was much earlier on and did involve significant tunneling next to 93.
  • The grade changes are probably not going to work in such a compact area around Clayton split. If CR is changing grades you're bound to 1.5-2% FRA grades which means really long inclines and speed penalty the steeper the grade. Red changing grades is pinned in by the Freeport and Clayton St.'s bridges being only 1000 ft. apart. The abutters are going to complain if there are flyover ramps staring into their 2nd-floor windows. As per the 2012 MPO study, this sorting is probably going to have to happen earlier...well before Freeport.
 
  • It would have to be some sort of grade-separated junction, because a totally flat (Copley Jct.-style) junction would be conflict-city at 3-minute headways with zero resiliency. On your render that would be very hard to shiv in around the residential abutting Clayton St. split. The 2012 MPO study did a flying junction past Savin Hill, but it was much earlier on and did involve significant tunneling next to 93.
  • The grade changes are probably not going to work in such a compact area around Clayton split. If CR is changing grades you're bound to 1.5-2% FRA grades which means really long inclines and speed penalty the steeper the grade. Red changing grades is pinned in by the Freeport and Clayton St.'s bridges being only 1000 ft. apart. The abutters are going to complain if there are flyover ramps staring into their 2nd-floor windows. As per the 2012 MPO study, this sorting is probably going to have to happen earlier...well before Freeport.

Ah, just remembered there is a longer, completely straight segment of the ROW, just north of the first bridge to the south, and the land use is adjancent to a bus yard, and a highway, so it's away from residential areas.

I'm just curious if there is a way to keep the ROW as is through Savin Hill by having only 2 RL tracks through the station and reallocating the extra space for the 2nd CR track. There's a little bit of wasted ROW space between the Ashmont Inbound track and the CR track just south of Savin Hill station, so there might be room for a junction there before the Braintree flyover is needed (I suppose the over/under flyover could be swapped for the Ashmont inbound/CR track).

If grade continues to be an issue, I wonder if dropping the ROW north of Savin Hill Ave from 5 tracks to 4 (2 RL + 2 CR), would allow enough space to relocate Savin Hill RL station to the north of the overpass, allowing an extra several hundred feet for grade level changes along I-93.

I'd also wonder if the CR had a more RR model with service evry 30 minutes, whether it could absorb some of the RL's Braintree Branch traffic for those who desire the shorter CR travel times skipping most of the RL's stops.

1684027108685.png
 
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Question: Why was Columbia Junction built the way it is in the first place?
 
Here's my fantasy idea for Intercity & Regional rail in New England


Core Upgrades


  • Build a North-South Tunnel in Boston
  • Build a new Inland High Speed line via New I-91/84/90 ROW : New Haven – Hartford – Worcester – Boston up to 180mph
  • Fully Electrify the MBTA Commuter Rail & transform it into a Regional Rail
  • Upgrade the tracks to 110mph and Electrify the East-West Corridor : Boston – Albany
  • Upgrade the tracks to 110mph and Electrify the Connecticut River Line : New Haven to White River Junction
  • Upgrade the tracks to 110mph and Electrify the Downeaster to Portland
  • Rebuild Portland Union Station
  • Upgrade the remaining New England Intercity routes to 90mph
  • Extend the MBTA Franklin Line to Milford
  • Extend the MBTA Lowell Line to Concord
  • Extend the MBTA Newburyport Line to Portsmouth
  • Extend the MBTA Old Colony Lines to Buzzards Bay
  • Extend the MBTA Fall River Line to Newport
  • Extend the MBTA Providence line to Kingston
  • Add Infill Stations at Norwood (Warwick) , Auburn (Cranston) & Silver Lake/West End (Providence)
  • Build a Regional S-Bahn: Waterbury – New Britain – Hartford – Manchester
  • Build a Tram-Train Line : Gorham - Portland Union → tram along Congress Street to Franklin Street to Thames Street → Yarmouth - Lewiston
  • Add Infill Stations on : Waterbury Branch at Wilbur Cross Parkway & Devon ,Danbury Branch at Wall Street , New Canaan Branch at East Stamford


New Amtrak & New England Rail Routes
  • Woonsocket Line : Worcester – Woonsocket – Pawtucket – Providence – 7x daily : Diesel
  • Central Rail Corridor – New London – Norwich – Amherst – Brattleboro – 6x daily : Diesel
  • Middletown Connection : New Haven – Durham – Middletown - 7x daily : Electrified
  • Eastern Link – New London – Norwich – Putnam – Worcester – 6x daily : Diesel
  • Northern Tier : North Adams – Greenfield – Fitchburg – Boston – 4x daily : Diesel , operating as an express train along the MBTA Fitchburg Line
  • The Narragansett : Providence – Pawtucket – Taunton – Fall River – Newport – 5x daily
  • Amtrak Hoosac : Burlington – Rutland – North Adams – Greenfield - Northampton - Springfield -Worcester – Boston – 2x daily : Hybrid
  • Amtrak Green Mountain Flyer : Montreal – Burlington – Rutland – North Bennington - Watervliet (Troy) – Albany – 2x daily + 1x daily to NYP
  • Amtrak New England Cities : DC – New York – New Haven – Springfield – Boston – 7x daily : Electrified
  • Amtrak Northeast Regional : Norfolk - Richmond -DC – New York – New Haven – Providence – Boston – Dover – Portland – 5x daily : Electrified
  • Amtrak Lakes to Ocean Service: Cleveland Union – Buffalo – Albany – Springfield – Boston – 3x daily : Electrified
  • Amtrak Acela : DC -Baltimore – New York – New Haven – Hartford – Worcester – Boston – 14x daily
  • Amtrak Cape Codder : Grand Central Terminal - Stamford – New Haven -New London – Providence – Hyannis – 3x daily : Electrified
  • Amtrak Clam Digger: Grand Central Terminal – New Haven – Providence – Fall River – Newport – 2x daily : Electrified
  • Amtrak Berkshires Flyer : Grand Central Terminal – Stamford – Danbury – Lee – Pittsfield – 4x daily : Electrified
  • Amtrak Red Wing : Montreal – St Albans – White River JCT – Springfield – Boston – 3x daily : Hybrid
  • Amtrak Gull : Boston – Portland – Bangor – Saint John – Moncton – Halifax – 1x daily : Hybrid
  • Amtrak Flying Yankee : Boston – Portland – Lewiston – Bangor – 2x daily : Hybrid
 
Question: Why was Columbia Junction built the way it is in the first place?

It was built this way so that the commuters coming from Quincy and Braintree never had to mix with the folks from Dorchester (i.e. racism.) Originally the Braintree Line didn't even stop at JFK/UMass.
 
Question: Why was Columbia Junction built the way it is in the first place?
When the South Shore Branch was originally being planned in the mid-60's, they planned to make it separate from the existing Red Line and terminate on the surface near South Station (which, recall, was to be demolished and reimagined). The original intent was to replace commuter rail, not act as an appendage to rapid transit...as they were operating on the assumption that most of the NYNH&H Railroad would eventually be abandoned as the company went down in flames. This would allow extension to Weymouth, to Brockton, to anywhere they wanted to go. Basically, they were thinking of more of a BART-type second system than an organic extension of the Cambridge-Dorchester subway...merely cribbing the same rolling stock for a different RR-replacement purpose. And for that reason the downtown terminus was favored rather than running thru and branching Red Line frequencies.

It was a hotly debated decision, however, as there were lots of planners who did want it to interface with Red. So they hedged on a design for Columbia Jct. that would work with both schemes, which led to it being wildly overbuilt. It had to run high-speed service whisking to a downtown terminus, and also had to intermingle with subway frequencies if that was the tact they took. This is also the reason why the Cabot leads are also so over-designed...they were originally intended for revenue service. The yard for the Cabot maintenance facility wasn't purchased by the T until 1969, after Penn Central had already bought the NYNH&H and was dumping property ballast. This is also why there was no effort at doing a Columbia/JFK platform for the South Shore Branch during design (that didn't come until a 1982 graft-on). The stub-end terminal eventually fell out of favor by the late-60's (about the same time the historical preservation forces had started rallying in-force over saving South Station), but the junction's design was already finished so the only thing that changed was that the stub-end tracks became long shop leads to the newly-purchased Cabot property. The junction remained as originally designed, for either/or revenue service.
 
Putting this in the "God Mode" and not "Crazy Mode" thread as it naturally assumes a universe where we took a Parisian attitude towards heavy rail transit.

Instead of continuing the Blue-Red Connector down Storrow towards Kenmore and points west, what about.....(drum roll)....turning north to give Chelsea, Everett and eastern Malden the rapid transit service they have deserved for so long?

I present to you: The Blue Bobby Pin.

1685574215490.png


Route:
  • The project would use the infield of the various Charles Circle ramps to the north of Charles/MGH and Lederman Park as staging ground and laydown to send a TBM north underneath Storrow, the Charles and Revere Park to form the rapid transit component of the Tobin's eventual, tunneled replacement.
  • Pull the TBM out of the ground somewhere around the Kayem factory back lot in Chelsea (Everett Ave onramp to the Tobin) and turn left in a cut-and-cover tunnel under Everett Ave to the Chelsea commuter rail stop, kinking left to follow Vale Street and across Revere Beach Parkway to Ferry Street.
  • From there, follow the low ground around Everett's biggest hill to Glendale Square, where the tunnel turns north up Broadway to the Northern Strand ROW, where a little eminent domain could get you a transit-oriented redevelopment opportunity and a portal to elevated tracks that doesn't conflict with the bike trail too much.
  • Elevated guideway follows the Northern Strand until just after it crosses Salem Street in Saugus, where it turns left to follow a power line ROW that, conveniently, is also a quarried-out saddle between a pair of hills, before turning right to run above Route 1 to the Square One Mall.
    • An alternate route would follow Broadway past the Northern Strand trail in a cut-and-cover tunnel before surfacing in the infield of the ramps that link Broadway and Route 1, but this would miss the existing multifamily development at Overlook Ridge.
Stops (south to north)
  1. Charles MGH
  2. Science Park (connects to Green Line)
  3. At or around City Square
  4. At or around the Vine Street/Chelsea Street intersection (picks up traffic from the Navy Yard and the Bunker Hill housing project mega-redevelopment)
  5. At or around where Williams Street or 2nd Street cross under the Tobin in Chelsea
  6. Chelsea Station, at Market Basket
  7. Just past the Ferry Street/Chelsea Street intersection in Everett, to give the train a chance to straighten out and put a northern entrance as close to the Whidden Hospital (sorry -- "CHA Everett") as you can while still being walking-distance from the 5-over-1s sprouting up south of the Parkway
  8. Glendale Square
  9. A hair north of Wehner Park
  10. Under the Eastern Ave/Broadway intersection (it'd be too far east if this waited until after the train leveled out on the elevated tracks)
  11. Linden Square
  12. Possibly around about here, accessed through the park opposite Overlook Ridge, or maybe hope the Overlook developer will fund a shuttle bus that brings people deep in the development into realistic reach of the Linden Square stop.
  13. Collins Ave./Route 1 (serves the Kane's Donuts development and the Saugus single-family neighborhood opposite
  14. Square One Mall
The alternate route described above would, instead of 10-14, hit Maplewood Square, plus somewhere between that and Route 1 depending on what moves multifamily developers start signalling towards adjacent properties, before ending up at the mall.

Raison d'etre:

This would be one way to fill the big gap in rapid transit coverage between the existing Blue and Orange lines, into which Charlestown, Chelsea, Everett and Eastern Malden fall. These areas are heavy users of existing MBTA bus lines, per the Better Bus profiles, and despite being pretty dense already, they clearly have potential to grow further by densifying existing, single-story retail, as various projects going up in the area show. And, by relieving routes like the 111 and the 104/109 of the need to schlep all the way into downtown or Sullivan Square, that lets existing bus resources be redeployed to beef up service on those routes or elsewhere, like boosting radial service on corridors like Squire Road in Revere and Salem Street in Malden.

You could end this right at Linden Square and probably be fine, but enduring the Saugus Meat Grinder would also help unlock the latent housing potential in the Square One site -- probably the saddest mall in Greater Boston, in a corridor that developers are very clearly targeting for lots of new apartments -- and make all those Route 1 apartments realistically more transit-oriented via private shuttles.

Downsides:
  • Can't connect to the Orange Line a second time as far as I can figure out: too complex to get to Community College.
  • Misses some of the 111's major trip drivers.
  • Misses Everett Square, the casino district, and the western side of the Everett 5-over-1 zone (but maybe, with an Urban Ring, this wouldn't be important?)
  • As stated at the top, really only makes sense in a world where other new lines add capacity between downtown, Kenmore and points west instead of some BLXX along Storrow or another route.
  • Requires underpinning the Orange Line tunnel under the Charles at a tricky point: under water and in between the busy Zakim and Draw 1 and Draw 2 leading into North Station; related difficult interactions with a NSRL tunnel.
 
Blue Line was looked at in the 2003 PMT: https://www.ctps.org/data/pdf/studies/transit/PMT-2003.pdf
(See pages 5C-33, 5C-37)

Blue was estimated at twice the capital cost of Green because of the need to tunnel from Bowdoin to Lechmere. That was also a direct alignment that missed Charles/MGH and thus the Red Line connection - doing that would have acquired additional tunneling at even more cost.

A two-car train of Type 10s will also have the same capacity as a six-car Blue Line train. (The Blue Line train is a bit longer, but it has more cabs and couplers that reduce the actual passenger space)
 
A two-car train of Type 10s will also have the same capacity as a six-car Blue Line train. (The Blue Line train is a bit longer, but it has more cabs and couplers that reduce the actual passenger space)

Interesting. I wonder if there's any real benefits to be had to reverting the Blue Line back to its Trolley roots if it means no drop in capacity (assuming similar throughput of vehicles). Perhaps the ability to more easily branch on either end? Any ROWs that could take more advantage of light rail than heavy? The ability to tie into the Green Line?
 
Interesting. I wonder if there's any real benefits to be had to reverting the Blue Line back to its Trolley roots if it means no drop in capacity (assuming similar throughput of vehicles). Perhaps the ability to more easily branch on either end? Any ROWs that could take more advantage of light rail than heavy? The ability to tie into the Green Line?
The far easier thing to do would be to build Red-Blue knocking out Bowdoin Loop, treat State St. curve, and go with Orange Line-length (or as close to that as you could go) cars. OL-length consists on Blue would constitute a 26% increase in seating capacity per train, without increasing the number of cars per consist.
 
Spitballing some routes here:

North Side
  • SL3 Branch - Instead of converting this to a Green Line branch, tie this into the Blue Line and have more incentive to extend further into Everett owing to more connectivity than the SL3 can provide. Tunnel under any parts of Broadway you have to, but probably mostly surface-level with a dedicated ROW.
  • Lynn - Allows usage of 1A for ROW for any needed distance to Lynn. Maybe the ROW along Point of Pines is too encroached? Maybe a dedicated ROW bridge over the marsh area is too expensive and you just need to hop onto it for a bit? Maybe on the far side it makes more sense to stick to a more southern ROW to hit potential TOD in the current industrial areas? Sky's the limit here.
  • Rt 60 - There's a few places to branch here, but the ROW is wide enough to support a median-running branch and the surrounding area seems dense enough to support it, with a few bus lines already running here.
South Side
  • North Station Loop - Turn north from Charles/MGH and tie into the Green Line stub tracks north of North Station. Provides connectivity to the rest of the Green Line at the cost of additional running time. Almost certainly not worth it given the ability to transfer at Government Center, but you could just terminate trains at GC and provide North Station commuters more access to other parts of the CBD (such as MGH). Going the other direction, Green Line trains would then have access to the rest of the Blue Line, providing a (convoluted) East-West single-seat ride. Again, though, given the ability to transfer at GC I don't think there's much to be gained here other than maybe adding terminal tracks at MGH and running some Park St trains through?
  • Sullivan Square Extension - Continue the tracks west from Charles/MGH and turn north under Broadway in Cambridge. From there, hop onto the Grand Junction and go north along the GLX maintenance facility tracks to a Sullivan Square extension as frequently discussed for the Green Line. From there, you can run to a number of northern extensions such as the Northern Strand path or even looping back towards the SL3 route and providing a complete looping route from Everett/Chelsea to downtown. Other options include the a Broadway ROW.
  • Red Line Connector V2 - Eat the Union Square branch of the Green Line by going west instead of East after the Grand Junction.
    I can't really see much in the way of even more southerly routings. Charles/MGH is pretty much pointing due west, so other than the usual Storrow subway suggestions (which wouldn't really benefit from such a replacement) I don't see many options south of the Charles without major work on one of the downtown stations (such as reconfiguring GC to send some Blue Line tracks south to Park St).
  • 1685651212220.png
 
Interesting. I wonder if there's any real benefits to be had to reverting the Blue Line back to its Trolley roots if it means no drop in capacity (assuming similar throughput of vehicles). Perhaps the ability to more easily branch on either end? Any ROWs that could take more advantage of light rail than heavy? The ability to tie into the Green Line?
I've thought of that too, converting the Blue Line back to light rail (LRV). It would allow the Red-Blue connector to be a surface line along Cambridge Street, by opening up the old portal. A lot cheaper than a tunnel. It would also allow any LRV line from Salem to Danvers to be a branch of an LRV Blue Line instead of a separate line.
 
I present to you: The Blue Bobby Pin.

Route:
  • The project would use the infield of the various Charles Circle ramps to the north of Charles/MGH and Lederman Park as staging ground and laydown to send a TBM north underneath Storrow, the Charles and Revere Park to form the rapid transit component of the Tobin's eventual, tunneled replacement.
  • Pull the TBM out of the ground somewhere around the Kayem factory back lot in Chelsea (Everett Ave onramp to the Tobin) and turn left in a cut-and-cover tunnel under Everett Ave to the Chelsea commuter rail stop, kinking left to follow Vale Street and across Revere Beach Parkway to Ferry Street.
  • From there, follow the low ground around Everett's biggest hill to Glendale Square, where the tunnel turns north up Broadway to the Northern Strand ROW, where a little eminent domain could get you a transit-oriented redevelopment opportunity and a portal to elevated tracks that doesn't conflict with the bike trail too much.
  • Elevated guideway follows the Northern Strand until just after it crosses Salem Street in Saugus, where it turns left to follow a power line ROW that, conveniently, is also a quarried-out saddle between a pair of hills, before turning right to run above Route 1 to the Square One Mall.
    • An alternate route would follow Broadway past the Northern Strand trail in a cut-and-cover tunnel before surfacing in the infield of the ramps that link Broadway and Route 1, but this would miss the existing multifamily development at Overlook Ridge.
I'm quite charmed by this idea, and I really like the thought you've put into where to build the subway north of the Mystic. Crayoning radial rapid transit in Chelsea is always an interesting challenge because it would be totally greenfield -- the closest we get to a blank canvas, for better and worse. One thought -- could you grab more of the 111 catchment by utilizing the ROW of Route 1? For example, you could add a Bellingham Sq stop by following the highway until you hit the Eastern Route ROW, and then cut back to the (new) Chelsea Station and continue on the route you've plotted.

More aggressively, you could try instead continuing up the highway until it crosses Washington and put another station there. That would split the 111 into two segments of feeder routes less than a mile long each. It would be an awkward curve back to the Revere Beach Parkway to continue on to Everett, but probably there's room for tweaking. (Maybe put the transfer station closer to Chelsea High School and reroute the 111 slightly?)

Something like this:

1685819682576.png


What I will say, though -- I think this corridor is an excellent fit for @F-Line to Dudley's "Red X" proposal (creating a second parallel northern branch of the Red Line that splits at JFK/UMass, runs parallel to the current subway, and then picks up a new subway under Congress St). That would solve your Orange transfer problem, and would leave the Blue Line free to be extended to the west.
Interesting. I wonder if there's any real benefits to be had to reverting the Blue Line back to its Trolley roots if it means no drop in capacity (assuming similar throughput of vehicles). Perhaps the ability to more easily branch on either end? Any ROWs that could take more advantage of light rail than heavy? The ability to tie into the Green Line?
This idea really captured my imagination over the last few days. In general, I'm in favor of strengthening the Blue Line as part of a "heavy metro" network, but as @The EGE pointed out, LRT isn't, as they say, "your grandpa's light rail" anymore. So this really got me thinking.

I'll reply to @Charlie_mta first:
I've thought of that too, converting the Blue Line back to light rail (LRV). It would allow the Red-Blue connector to be a surface line along Cambridge Street, by opening up the old portal. A lot cheaper than a tunnel. It would also allow any LRV line from Salem to Danvers to be a branch of an LRV Blue Line instead of a separate line.
Sorry, but that's a hard no from me on a surface Red-Blue Connector; whether LRT or HRT, that connection needs to be fully grade-separated for throughput and reliability. But yes, I think the Danvers scenario is one case where LRT could be an easily build than HRT. (Though I would still want to keep an eye on capacity; modern LRT could probably equally current Blue Line capacity, but as F-Line points out, the Blue Line has not hit maximum HRT capacity. Switching to LRT could end up capping capacity in the long run.)

In general, I'd argue that the main benefit of LRT itself is the ability to occasionally intermingle with automobile and pedestrian traffic. But that's only useful in places where it's otherwise acceptable for such intermingling. Red-Blue Connector seems to fail that test, and as Boston and its suburbs continue to grow, there will be fewer and fewer places where that is acceptable.
SL3 Branch - Instead of converting this to a Green Line branch, tie this into the Blue Line and have more incentive to extend further into Everett owing to more connectivity than the SL3 can provide. Tunnel under any parts of Broadway you have to, but probably mostly surface-level with a dedicated ROW.
Whether LRT or HRT, I think branching the Blue Line at Airport is not the best idea. It halves frequencies to both branches, and we know from the current situation that there is heavy demand for North Shore bus <> Blue transfers. Even with BLX to Lynn, there's still going to be high demand, so I think half-frequencies are ill-advised here.

Lynn - Allows usage of 1A for ROW for any needed distance to Lynn. Maybe the ROW along Point of Pines is too encroached? Maybe a dedicated ROW bridge over the marsh area is too expensive and you just need to hop onto it for a bit? Maybe on the far side it makes more sense to stick to a more southern ROW to hit potential TOD in the current industrial areas? Sky's the limit here.

Rt 60 - There's a few places to branch here, but the ROW is wide enough to support a median-running branch and the surrounding area seems dense enough to support it, with a few bus lines already running here.
Yeah, this is where I think things get interesting. Route 60 worries be a little bit for halving frequencies to Lynn, but perhaps if you added a transfer station at the end of the Salem Turnpike in Revere, you could mitigate the impact. But Lynn is where some interesting options arise. For one, yes, if needed you have more options for reaching Lynn Central Square (although again, from a capacity and throughput perspective, I'd still prefer a fully grade-separated route into Lynn station proper). But I'm intrigued by the possibility of LRT branch lines spreading out across the North Shore. The Marblehead Branch, for one, would probably be less disruptive as LRT than HRT. And the idea of a short street-running route in Lynn itself -- say, down Washington and up Western Ave -- is very thought-provoking.

That being said: the things that make surface-running LRT more appealing are themselves somewhat at odds with "LRT as heavy metro service", in particular train length and to a lesser extent high-level boarding. Something that's good at running on Lynn streets, or that's good at quietly snaking through leafy backyards in Marblehead, is almost by definition not going to be good at shuttling huge volumes of Airport and Maverick transfer passengers over to downtown and beyond. Maybe you can find a happy medium, but they do seem a bit at odds to me.

(Maybe you run "heavy LRT" service into a transfer station at Lynn, with non-revenue track connections to surface tracks that handle "light LRT" in those other places. At that point, the conversion really is just about providing rolling stock access though.)
Sullivan Square Extension - Continue the tracks west from Charles/MGH and turn north under Broadway in Cambridge. From there, hop onto the Grand Junction and go north along the GLX maintenance facility tracks to a Sullivan Square extension as frequently discussed for the Green Line. From there, you can run to a number of northern extensions such as the Northern Strand path or even looping back towards the SL3 route and providing a complete looping route from Everett/Chelsea to downtown. Other options include the a Broadway ROW.
I don't love the "bobby pin" shape of these routes, though I agree they'd be theoretically viable. But they don't seem uniquely viable to an LRT Blue, and they would be equally viable on an expanded Green Line network.
Red Line Connector V2 - Eat the Union Square branch of the Green Line by going west instead of East after the Grand Junction.
This idea intrigues me more, though again this seems equally doable on the Green Line.
 
I can't really see much in the way of even more southerly routings. Charles/MGH is pretty much pointing due west, so other than the usual Storrow subway suggestions (which wouldn't really benefit from such a replacement) I don't see many options south of the Charles without major work on one of the downtown stations (such as reconfiguring GC to send some Blue Line tracks south to Park St).
Yeah, so this is where I disagree with you. Aside from potential Crazy North Shore LRT Pitches, I think this brings us to the strongest cases for converting the Blue Line: in general, converting one or more western Green Line branches to expand capacity in the Central Subway, and in particular, enabling a "Blue Line" to handle Needham service.

The problem with most "Blue-eats-Riverside" proposals is that they leave a Needham Branch in the lurch: the current Riverside Branch is fully grade-separated, but the Needham Branch is not, so it would be prohibitively expensive to build an HRT line there, which makes the Blue Line a hard sell. But an LRT Blue Line would be able to without issue.

That being said, as I've outlined in the Green Line Reconfiguration thread, there are other solutions that would provide enough capacity to serve the current and most proposed future Green Line LRT branches. Also, a Blue LRT line would have the disadvantage of not serving Back Bay, so it doesn't solve as many problems as it may first appear.

From an elegance perspective, an LRT Blue Line could take over the C Line, leaving the Boylston St Subway totally focused on a true "streetcar-subway network" radiating out from Comm Ave, and leaving the Huntington Ave Subway to handle Riverside and Needham service.

1685842350877.png


But again we come to the same problem: the C Line is of very different character than the current Blue Line, or the needs of a longer-distance service to Lynn. Does it really make sense to marry them together?

More plausibly, the Blue Line could pick up the "Fenway Branch" (gold in the sketch above) and interline with a Huntington Green Line west of Brookline Village, with one going to Riverside and one going to Needham. But even in that scenario, there are other (better) solutions to provide the necessary capacity.

Finally, converting to LRT forecloses the possibility of the Blue Line becoming a third heavy rail "trunk" radiating west from the city, pointing toward Allston, Newton Corner, Watertown and Waltham on the 100-year timescale. To me, that seems like a better alternative. Converting to LRT and going west simply gives you a third LRT trunk, and I don't think it's needed.
 
There is definitely spare capacity on BL past Maverick. While the 4xx routes do move a fair amount of people, a maxed frequency BL say 3 min, could easily split either after Maverick or Airport for a Chelsea stab.
 

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