Underground station layouts

Riverside

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Huh, I'd never realized that the loop at Adams wasn't used.

And yeah, that makes sense about looping north-originating streetcars, sure. But now I'm more confused -- were there contemporaneous loops at both Adams and Scollay? And if so, why would you need two?

EDIT: Was a station at Adams always part of the design, even before the route was changed? I can understand splitting the route into separate northbound and southbound tunnels given that they were tunneling under narrow streets -- not wide enough for 4 tracks. But why add a station at Adams at all? Was it that much of a destination?
 

F-Line to Dudley

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Huh, I'd never realized that the loop at Adams wasn't used.

And yeah, that makes sense about looping north-originating streetcars, sure. But now I'm more confused -- were there contemporaneous loops at both Adams and Scollay? And if so, why would you need two?

EDIT: Was a station at Adams always part of the design, even before the route was changed? I can understand splitting the route into separate northbound and southbound tunnels given that they were tunneling under narrow streets -- not wide enough for 4 tracks. But why add a station at Adams at all? Was it that much of a destination?
Simple answer: plans on termini changed between first shovel getting turned in 1895 and the 1897 opening. Surface streetcars looped pretty much wherever they could in the overcrowding that existed prior, so termini were fileted at Scollay and Adams by company prior to the subway. Streetcar tracks between the two were conjoined over 2 blocks with looping at both. See 1896 street map below with all surface streetcar tracks:



That informed how they designed the subway. Keep in mind that because the concept of a subway was so very new they were doing a lot of hedging on how they thought it should work, and some things like the northern route termini were big guesstimates. The big mess on the surface between the Scollay and Adams termini meant they hedged on both underground...but in the end only ended up needing one. Also note: Scollay was just a turnback from the north until 1963...the portion of loop used to turn back the western branches today was wholly new for the City Hall Plaza relocation. Park St. was the only place to turn the western and southern branches prior to '63, and there were two loops there: the inner loop still in-service that turns the B Line, and the outer loop that was abandoned but whose ROW behind the inner loop is still structurally intact. So the original subway designers were also trying to load-balance Park's 2 loops with 2 loops from the other direction...only because the street grid was so tight they had to be split between Adams and Scollay vs. the more spacious under-Common environs @ Park.


Adams was big in its own right because it was the convergence of Washington, Devonshire, Cornhill, and Brattle into a mega-intersection of wide-open space that forked northwest to Haymarket Sq. and northeast to Dock Sq. Biggest landmark in it was the Sam Adams statue in the middle of the giant asphalt/cobblestone sea. Because of the convergence of streets it was one of the most traffic-congested points in the entire city. One of the subway headhouses was placed in the middle of the triangle at top of the map where surface cars passed in 6 different directions.

Historically it was actually a pretty short-lived square as it was created in the early-1860's by a 'first-wave' urban-renewal project to widen the extremely narrow streets leading out of Dock Sq., which could barely pass two horsecarts side-by-side. The block of row buildings between Brattle and Cornhill shown on the Scollay end of this map were demolished on the end coming out of Dock Sq., and then Washington took out another row of buildings to the northwest when it was extended from Court St. to Haymarket Square...creating the cavernous environs @ Adams where all the new streets converged. And then barely 100 years later it was all erased by City Hall.
 
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The EGE

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Some more of what once was, before I go back to what is. The abandoned (lighter color) bits shown here are shown up to the surface; although at least something exists of them, not all that is shown is still extant. From L-R:
  • Public Garden Portal (used 1897-1914). Most likely, nothing exists except for the bellmouth under Charles Street.
  • Boylston Street Portal (1914-1941). Now occupied by a maintenance siding and a pump room.
  • Provision for the never-built extension to Post Office Square
  • Southern branch of the Tremont Street Subway to the Pleasant Street Incline (1897-1962). Intact up to just south of the flying junction; this hatch is the southern end of the tunnel proper, where it met the open incline. This track configuration is as-built; it may have been slightly different when streetcar service resumed after the Main Line El's 1901-08 use of the subway.
  • The incline to the Washington Street Elevated (1908-1987). From the south end of the outbound platform at Chinatown, you can still see about 100 feet of the tunnel.
South portals.png
 

vanshnookenraggen

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A question note entirely related to this thread but: how exactly did streetcars switch tracks when they were embedded in the street? With conventional rail you have a switch which moves a track but you can't do that in the street.
 

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A question note entirely related to this thread but: how exactly did streetcars switch tracks when they were embedded in the street? With conventional rail you have a switch which moves a track but you can't do that in the street.
Oh, streetcar switches are automatic too. On this one on South Huntington that switches for Heath inner vs. outer loops you can see the electrical box covers in the roadway. Right next to it about 1 ft. up you can see the actual turning switch mechanism on the left rail, which grabs the front left wheel. The right rail has no switch and is just a straight split frog, so when the left wheels get dragged left onto the inner loop the right wheels bank left with it. A right-turning switch would be configured the opposite: grab the right wheels with the turning switch, drag the left wheels through the open frog. This switch has a manual backup which you can see as a little slot in the ground next to the moving switch. Staff can hand-throw it with a metal rod that has a turning bolt at the end, and the little guard shack at Heath has switch rods always available in the storage closet.

The means for throwing the switch is deceptively simple. Operator coasts thru for going straight, powers thru for turning. There's an insulated section of overhead wire right before the switch fitted with a voltage detector that catches either the spike in power draw or lackthereof to trigger the switch. The switch then auto-resets itself back to the default position on a short delay after the voltage detector picks up the safe passage of the trolley out of the insulated section. Coast vs. power-thru has been universal practice from Day 1 of electrified streetcars to today, and every light rail and TT system on the planet that's in mixed-running outside of the signal system's control still operates this way. So on that linked Street View pic at Heath, the Type 8 sitting on the inner loop did a power-thru move at the switch to get there, while the Type 7 at the front of the outer loop coasted thru. If the Breda was last through the switch, then the switch has already auto-reset itself as it's back in the default "straight ahead" position for the outer loop. When Arborway service was still running through this spot there were simply two switches staggered in close succession such that during pre-1985 rush hour when the line was doubled-up in service with every-other train Arborway vs. Heath short-turns, the Arborway trains did a "coast + coast" maneuver to go straight, outer-loop Heath turning trains did "coast + power" thru both switches, and inner-loop Heath turning trains did "power" at the first switch only. A/B Line split at Packards Corner was power-thru for B right up to when the emergency 2-car pocket track on Brighton Ave. was torn out circa 2000, with the cut-out section positioned relative to the traffic light so the operator could get a short running start before making their pick.

With trolley pole or TT overhead you'll have reciprocal switchboxes on the overhead because of the way the poles grab the wire, so TT's operate on the same coast vs. power-thru maneuver. And it's easier to watch happen on TT's or Silver Line because the overhead switches make an audible click when they change directions that you won't hear on a default-direction coast-thru. Pantograph wire is much more simply welded-together at junction points with no wire switchboxes, but operates the same exact way. You will see little "Cut Out" signs hung on the wire hangers all over the TT system indicating where the switch cutouts and voltage dectors are. Green Line used to have those signs when all overhead on the system was still dual pole/pantograph compatible for co-mingled LRV & PCC running, but they disappeared when all the overhead across the system was renewed to pantograph-only in the late-90's in prep for the Type 8's.


Most surface switches on Green and Mattapan operate this way, including all the ones on the reservation. Central dispatch is not required to get around. Only exceptions are Blandford St. Yard controlled from the guard shack, the Brigham Circle crossovers controlled from the guard shack when service is short-turning, and some very seldom-used crossovers (all on the reservation, no in-street crossovers left) that are hand-throw because they're only practically used on the work shift. Chestnut Hill Ave. street trackage also has at least one hand-throw only switch amid its majority-automatic collection, as the eastbound wye onto the B was taken out of service several few years ago after a Type 8 wrecked and burned itself splitting a switch. Only the CH Ave. north to B Line east track is still connected, so that now emergency-only switch was downgraded to hand-throw.


EDIT: Actually, scroll straight up to the sky in the Street View shot and you can see the "Cut Out" sign on the wire hanger about a foot away from a couple extra jumper wires. That's the insulated section with the voltage detector. So when the Type 8 sitting on the inner loop was approaching a few feet behind that spot the detector caught the power draw surge coming through the overhead from the oncoming trolley as the operator was working the throttle on power-thru, then auto-threw the switch for the inner loop. When the Type 7 on the outer platform approached from that same spot the detector felt no surge in power because the operator was coasting, so the switch was not thrown and stayed fixed in the default straight-ahead position for the outer loop.
 
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F-Line to Dudley

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Explainers on how streetcars (and TT's) work:


Video of TT's on a wire switch. Note early in the vid how all the ones taking the right-lane wires are coasting...all the ones taking the left-lane wires are powering thru.
 

The EGE

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Interestingly, in SF, the power/coast method is not used. LRVs and historic streetcars have vetags (similar to the AVI units that set switch positions on the Green Line subway*) which are connected to the turn signals (needed due to street-running). Those vetags set the switches, and are also used in some locations to trigger TSP or dedicated signal phases. In a few locations, overhead contact pans trigger signal phases or TSP.

SF trolleybuses use either actuated switches (triggered by turn signals, with an antenna on the trolley poles) or selectric (poles are pulled one direction by the bus turning, which completes the circuit).

*AVIs work by the operator setting an origin-destination code, which tells the onboard unit which switches get set to which position. It then gives switch position info to AVI detectors when they are passed.
 

Charlie_mta

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I aways liked Lechmere station. It sits right on the surface in a dense walkable neighborhood. Lechmere station and East Cambridge embody everything I like about a neighborhood. I'm a bit prejudiced though, as i lived there as a little kid. Too bad this station is being replaced by an elevated station across a busy highway.
 

jass

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I aways liked Lechmere station. It sits right on the surface in a dense walkable neighborhood. Lechmere station and East Cambridge embody everything I like about a neighborhood. I'm a bit prejudiced though, as i lived there as a little kid. Too bad this station is being replaced by an elevated station across a busy highway.
I agree. When I first moved to Boston, I went to the mall there and I really liked the whole vibe. I know people on here hate malls, but it has such a nicer waterfront, direct connections to transit, and the inside isnt bad either
 

George_Apley

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Let's see those storage tracks at Lechmere! 😋

Awesome work with this project EGE!
 

The EGE

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Greatly. Lechmere is 42-foot radius inner and 50-foot outer; Boylston is actually much looser at 80 (westbound) and 90 (eastbound), but the tunnel environment focuses the sound. Other tight curves (less than 75 foot radius):
  • 50-foot radius on Brattle Loop
  • 60-foot radius entering GC southbound
  • 49-foot radius on Park Street inner loop, including the SB inner track. 68-foot radius for SB outer track.
  • 55-foot radius in Kenmore Loop
  • 45-foot and 49-foot radii on the Lake Street Yard loops, several other 50-foot curves
  • 50-foot radii on Prendergast Alley (Reservoir Yard to Cleveland Circle, the alley next to Dunkies)
  • Lots of 58-to-70-foot curves in Reservoir Yard
  • A 57-foot and a 70-foot curve in Riverside Yard
  • 50-foot radii on both loops at Heath Street
If you really want to get into the weeds, I spent an whole appendix of my thesis speccing out various minimum-radii possibilities. tl;dr:
  • 45 feet is the new minimum after Lechmere is gone
  • 49 feet just needs mods to a couple yard curves.
  • 60 revenue/50 nonrevenue is possible if you move some columns at Park Street (and eliminate the inner loop) and deal with Heath Street.
  • 60 everywhere means lots of nonrevenue stuff modified, of which Brattle and Kenmore loops are the trickiest.
  • 66 everywhere (20 meters, the smallest off-the-shelf available) requires some changes to GC as well.
 

F-Line to Dudley

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It must be a tighter radius than the Boylston curve, eh?
As EGE states, Boylston is hugely wider. That curve is notorious because it's slow as hell and squeals like a demon, not because it in any way inhibits vehicle choices. You can pretty much buy any catalog-order LRV on the planet within tolerances for Boylston. Mattapan Inner Loop is the tightest of them all, too tight to take anything longer than a PCC. That loop will be retired when the Type 9's are reassigned. Mattapan Outer Loop is OK for modern LRV's. Might be tight for true 'off-shelf' buys, but that's not a factor down there.


Per the GLT team's FCMB slides the only ones that exert significant influence on rolling stock buying decisions post-Lechmere are: Park and Brattle Loop. Brattle Loop gets its sharpest at the 1963 transition point between the original Scollay platforms and the GC outbound platform, so a historically more recent 'sharpening'. There's enough room back there that some curve-easing is probably non-invasively doable.

Park actually had two loops until the 1963 GC reconstruction introduced the current westbound turnback, fileting turnbacks at GC for the first time ever and reducing Park's westbound short-turning that used to be exclusive to that stop. The current Park loop is the tighter inner loop. Park Outer was abandoned mid-60's after GC opened, but its path is unobstructed and it has been an on-again/off-again reactivation candidate. Inner Loop was prioritized because it is completely traffic-detached from the outer thru tracks and allows simultaneous movement on both northbound berths. Outer Loop touched both northbound tracks with a combo switch, much like the combo switch that splits outbound traffic between platforms on the other side. Outer Loop did, therefore, require a very momentary pause in simultaneous movements when the switch common to both northbound tracks got touched. Bringing back Outer Loop in a trade for retiring Inner Loop is one of the universe of considerations for keeping the ruling limits very slightly north of 50 ft. radius. The plan for utilities relocation on the new thru-service northbound crossover would have to be lightly modded to fit a switch cleanly in for Outer Loop reactivation, but feasibility is fine for that. All a matter of just spending a few more bucks on the utility/supports relocations.

FCMB presentation didn't go into too much detail about Reservoir, because there's such a dizzying array of paths to take through the yard that only some combinations are pinched. They said minor yard reconfig would lick that one. Lake St. has no fewer than seven paths you can take to loop around depending on which storage track you start from, so I don't know exactly which paths skirt the sub-50 ft. minimums. That too is easily solvable with a minor yard reconfig. Heath they will be doing some troubleshooting any which way because only Outer Loop can take a 2-car Type 10 'supertrain' or 3-car Type 7/8/9 lash-up...Inner Loop is capped at a 2-car 7/8/9 consist or singlet Type 10. Since both loops are needed at peak even when the platform on Outer Loop is prioritized whenever available they are probably looking at property acquisition of a slice of the VA employee parking lot immediately behind them. They doubled their parking garage space just 5 years ago and have more room still on the other side. Land-swap of the 20 spaces closest to Heath is probably enough to trade the Inner Loop to current Outer Loop, ease the curvature, and make a "new" Outer Loop behind it on the swapped land. Or, in the unlikely event the VA is feeling generous enough to swap the whole lot away...enough square footage for a full-on Lake St.-capacity yard. Any which way Heath isn't a hard solve.

Generally speaking the big LRV manufacturers offer enough dimensional variety in their modular 'family' makes that 60+ ft. everywhere--and all the disruption that entails--shouldn't have to go on the table. All the major players make 'streetcar' form factor vehicles that are still 'supertrain' length while being more appropriate for turning radii on legacy on-street networks that are banging sharp lefts and rights at intersections. Toronto's recent procurement (won by Bomardier Flexity Outlook) for total fleet replacement of its vast streetcar network exerted enough gravitational pull on the industry because of its order size that everyone chunked-together compatible product for them and similar applications. To keep the order options widest we really only need to focus our attention on the sub-50 footers. Of which Park Inner and Brattle are the two toughest (albeit with feasible solves). Everything between 50 and 60 ft. sort of resides on a sliding scale on how much effort is worth it to expand the horizons outside of the 'streetcar' makes and towards the real wide-load makes being snapped up by newer systems. The options at 'streetcar' turning radii are still pretty broad...but it's mainly an exercise in how much envelope-pushing is worth it to widen that field to the greater-than 'streetcars'. That's TBD. If it's within yards that generally have multiple paths to begin with or a case like Heath where the expansion real estate is available and you're just haggling over tens-of-grand in price...they're probably confident to push that envelope. If it involves any subway walls being heavily modified (e.g. if 55 ft. radius Kenmore Loop just isn't enough)...probably not so much.
 
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The EGE

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I promised a big-name station would be next - and after much delay, here's North Station.

North Station 1.png
North Station 2.png
North Station 3.png


Here's some slices that might clarify how everything fits together underground. Surface lobbies and stairs/escalators/elevators only:
North Station 4.png


That, plus the mezzanine / GL northbound / passageway level:
North Station 5.png


That, plus stairs/escalators to the platform level:
North Station 6.png
 

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