MBTA Construction Projects

F-Line to Dudley

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F-Line to Dudley

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With 50 days remaining until the FRA's 12/31 installation deadline, brand-new cab signals on the Lowell Line--the first ever for the northside--have now been activated at least as far as Crawford Interlocking in Woburn (a.k.a. the crossover + freight passing track switch abutting the south tip of Anderson RTC Station). Possibly further, as Wilbur Interlocking (Anderson RTC north-abutting crossover + freight passer tie-in) and Wilmington (crossovers pair + Wildcat Branch split) may also be done at this point. Roughly the halfway point in track miles to Lowell.

If traveling on the Lowell Line you will now notice that the intermediate wayside signals at West Medford, Mystic Lakes, and Cross Street now have their signal heads turned away from the tracks having been supplanted by the in-cab readout. So may MA 38, Wilmington if they've made it as far as Wilmington split. Those heads will be taken down in the coming weeks just as the Worcester Line intermediates along the Pike in Newton all disappeared late this summer when that cab signal activation went live.

Interlockings (i.e. automatic-throw switch crossovers, junctions, or sidings) still retain signal heads under cab signals as a visual fail-safe for mis-thrown switches. So all the new replacement heads in the GLX construction zone, Winchester Ctr. interlocking, Crawford + Wilbur bookending Anderson, and the junction at Wilmington retain their signal lights and will be getting brand new LED replacement masts soon if they haven't already.

For 12/31, additional intermediate heads will be coming down at Lake St., Wilmington; George Brown St., Billerica; High St., Billerica; Town Farm Lane, Billerica; and I-495, Lowell. Interlockings with retained signals will be Pond St., Billerica and all of the Downtown Lowell ones between Concord River and the station.

The 12/31 FRA deadline is for Lowell to get set up as a "demonstration line" for northside cab signals. Making that deadline automatically clinches a 2-year extension for the other northside lines to get cabbed up. This is because the original plan for Positive Train Control interoperating without cab signals was ruled very late in the game as inadequate protection by the FRA. Therefore the northside, which has fully operating PTC now, is forced to last-minute add the cab signal layer that all of southside has or else all PTC-equipped northside lines would've been saddled with additional speed restrictions. The Lowell demonstrator is the proof-of-concept to the feds that the T can meet a representative deadline.

Securing that means they get granted 2 years of leeway to continue running PTC-sans-cabs at full operating speed on the other lines before the new restrictions kick in...enough time for them to get Fitchburg, Haverhill/Reading/Wildcat, and Rockburyport settled up.

The longstanding blanket ban on northside cab signals imposed as a condition of Boston & Maine's 1976 asset sale to the T was voluntarily waived by Pan Am, who has now acquired 40+ hand-me-down GE locos from CSX pre-equipped with cab signal units. Signal project ends at Lowell Station on the NH Main; Westminster Interlocking on Fitchburg at the layover yard just past Wachusett; Plaistow Interlocking on the Western Route just past state line at end of double-track; and end-of-line @ Rockburyport.

Continuation of signal system on the freight-only NH Main past Lowell Station to North Chelmsford and Nashua; on the Fitchburg all points west of Wachusett to Mechanicville, NY; and on the Western throughout Downeaster territory doesn't get touched with cabs or PTC unless/until the T extends service to Nashua or Downeaster frequency increases clear a certain threshold trigger.
 
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Jahvon09

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Don't forget the elevators. New ones were added & old ones are being replaced with newer ones. :)
 

F-Line to Dudley

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https://www.masstransitmag.com/rail...te-as-part-of-mbtas-green-line-transformation

T puts a wrap on the Fenway Portal Flood Resiliency project. New maneuverable steel doors are now in-place for the D Line portal, the single-biggest flood inundation risk on the subway because of frequent Muddy River overtopping events that flow down the incline like an unstoppable storm drain. Ever since the disastrous 1996 Kenmore Flood protection measures have been ad-hoc at best, involving an army of staffers manually placing wood slats in slots in front of the lower half of the portal then packing a sandbag berm in front...good enough to stop most minor floods of the last 20 years with some soppy cleanup but wholly inadequate for any repeat of the '96 torrent. The new doors, in addition to placing a hard stop in the worst-case inundations, will be maneuverable faster and have upgraded all-around drainage to dramatically shorten the service outages start-to-finish whenever Charles Basin and the Muddy are imperiled.
 
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Tom Nevers

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A presentation on transit infrastructure costs, including a detailed case study of the MBTA’s Green Line extension, will take place 12/9 at 11 AM.

This is an extension of transitcosts.com and will feature some of the folks involved with that project.

You can learn more and register here
 

Arlington

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Not sure if its been shared but heres a short visual from the mbta of how the flood doors work.
Why wouldn't they have the doors hinged so that the water pressure would push them more tightly closed, like airplane doors do, such that the pressure difference closes them more tightly?

From the vid these seem like they're designed to be "push past" rather than "pushed closed" by the water.
 

millerm277

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Why wouldn't they have the doors hinged so that the water pressure would push them more tightly closed, like airplane doors do, such that the pressure difference closes them more tightly?

From the vid these seem like they're designed to be "push past" rather than "pushed closed" by the water.
There's a video of the actual project as implemented on the project page: https://www.mbta.com/projects/fenway-portal-flood-protection-project

I'm pretty sure they lock into some of that structure they've built on the walls and overhead, I don't think they're just supporting themselves entirely off that center post.
 

F-Line to Dudley

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They probably can't open outwards because of the incline of the track.
The doors also aren't airtight at the bottom, only being able to go down to the rail head. You'd still have a seeping river on the trackbed the remaining 1-3 inches inside the flanges of the floor interface if that were the only maneuver (albeit less serious than a multi feet-deep Cloaca Maximus cascading towards Kenmore). Weighted berms would still have to be piled up at the bottom of the doors for a suitably tight seal...be it by a much smaller-scale sandbag maneuver or (better) some quicker/reusable modular strategy like the blow-up water balloon thingy they've started deploying to keep the Aquarium entrance water-tight from storm surge. The later could be stuffed compactly in a storage box near the doors at-the-ready at all times with standpipe hookup facilitating inflation by semi-automation with safest minimal number of attending personnel. This would be in addition to some sort of pressurized plugs that slot into the flanges under the door for airtight seal...which would need to afford a maint worker the ability to get up close within inches in order to perform any necessary troubleshooting of their insertion/alignment.

Since the Muddy is capable of filling the entire incline to the tippy top like a swimming pool, the way to stage this final reinforcement is going to be from behind the doors in a navigably dry tunnel where the upgraded drainage pumps are keeping the trackbed dry up to within a few feet from the plugged-up 'swimming pool'. Or...put it this way: if the final seal needs adjustment after deployment because of a split sandbag or some other late-breaking necessary reinforcement, would you rather:
  • Fumble around blindly with sandbags and shovel under 10 ft. of debris-choked water with a bucket crane that's taking a drink from way atop the Fenway side path? Then cross fingers and hope like hell you sank the additional bags in the right place during the blind fumble to "close enough" plug the problem. Hope the site supervisor has scuba gear handy!
  • Bring a powered work car up to Beacon Jct. or further full of equipment, and hoof it on no worse than inches-wet trackbed right to the doors for a precision adjustment?
Doing the adjustment from the inside with precision is faster and saves critical time if something needs an touch-up before partial breach gets serious. It's going to run differently by access at different portals/breach points, but right here plugging the torrent then finishing the seal from behind gives them the most options when time is of essence and the incline may already be well on its way to filling up the swimming pool.
 
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ra84970

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Watching the video -- it reminded me of a question that I've always had...why does the T not use rigid overhead catenary in the GL tunnels? I remember seeing the rigid catenary while visiting Barcelona a couple years ago and felt like it seems like something that would fit in the context of the central subway.
 

F-Line to Dudley

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Watching the video -- it reminded me of a question that I've always had...why does the T not use rigid overhead catenary in the GL tunnels? I remember seeing the rigid catenary while visiting Barcelona a couple years ago and felt like it seems like something that would fit in the context of the central subway.
Green Line is constant-tension cat, which is--physics-speaking--"rigid" because it's held in constant tension by counterweights to the ambient temperature. It's come a long way from trolley pole wire and variable-tension pantograph cat that bounces all over the place because of the slack.

But it's not -=FIXED=- like it's mounted on concrete blocks as if it were an overhead third rail or something. The bracket mounts still have spring mechanisms for a little bit of give. If there were no give all the forces would go exclusively to pounding the crap out of the pantograph's carbon shoe surface, dramatically shortening their lifespan. Panto shoes are 'consumables' that have to be replaced a lot because their failure modes run their course over a matter of months. The wire is *also* laterally un-fixed, and waves side to side from mount to mount so the friction surface on the panto is spread over a +/- half-foot radius instead of just wearing a hole straight through the middle of the panto shoe necessitating replacement within weeks. You can see by looking up from any subway station platform that the ceiling-mount brackets have a 'track' on them and the actual spring mount is fixed in a different place from one to the other...moving over the course of several mounts to one end of the mounting 'track' then back again. Until the roughly sine-wave wire placement pattern repeats itself.

Both pantograph LRT and overhead RR's up to the fastest HSR trains do their constant-tension cat exactly the same way. Barcelona's 3 different tram systems are all pretty electrificaiton-conventional. It's extremely likely to be exactly the same functional OCS design as the Green Line and/or Northeast Corridor: constant-tension suspension for contact reliability with lateral oscillation for pantograph duty cycle reliability. The wire mounts can aesthetically look different, be new-install (as 2 of Barcelona's 3 tram systems and New Haven-Boston electrification are), or be retrofitted onto 100+ year-old poles (some surface Green Line sections + most of the NEC to Washington, both retrofitted to new constant-tension wire on old poles over course of last 2-22 years). But the basic OCS layout is exactly the same in each case.
 
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F-Line to Dudley

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Have they pre-run conduit for the replacement fixtures, when the current ones get too dim?
They have to first install the trash bins where they throw away the fixture covers instead of washing them. The bin placement isn't scheduled until Spring 2022 and requires 3 weekend bustitutions.

Sorry...spaghetti wire doesn't sprout up until the Signal Dept. signs off!
 

Vagabond

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The T is setting up all the new LED lighting at "very bright", because, par normal, they never plan to clean any of the fixtures, so it will be "dim" in a year.
None of you have done a lighting project???

The lights are ALWAYS installed at the highest setting. Not sure of these model fixtures, but LEDs are inherently dimmable. Most modern systems come with lighting controls that dim based on daylight/ambient light, and motion, and IR sensors, all of which must be calibrated. Zoning is no longer by wiring if you can help it either - wireless controls are so much easier. While these look like new fixtures (and not just ballast bypass relamping), the bigger problem with 1-for-1 replacements instead of realigning lamp placement is that old linears put out much less, so LED overlighting commonly causes dimming adjustment requests. I would be amazed if the T didn't put in modern controls on these.

TLDR: Finish install, lighting contractor will dim next to appropriate lighting levels. If not - poor investment.
 

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