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Old 01-02-2014, 09:42 AM   #1
stick n move
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The Silver Line

Does anybody knows why this line cannot be turned into rail? It seems like it would be relatively easy seeing that there are already underground stations, tunnels, and routes. Also there is even some rail lines already in the seaport that are not being used that could be added in. I just dont understand why this area that is growing faster than anywhere else in the city, and desperately needs a subway system, cannot seem to add one. Does anyone know the future plans for this?
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Old 01-02-2014, 10:17 AM   #2
dshoost88
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Re: The Silver Line

Simple answer: cost. Do a google search for a documentary you can stream for free on IMDB called "Equal or Better". It does a great job explaining the history of the silver line and other transit improvements, along with forecasts for the future.
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Old 01-02-2014, 10:29 AM   #3
datadyne007
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Re: The Silver Line

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Originally Posted by stick n move View Post
Does anybody knows why this line cannot be turned into rail? It seems like it would be relatively easy seeing that there are already underground stations, tunnels, and routes. Also there is even some rail lines already in the seaport that are not being used that could be added in. I just dont understand why this area that is growing faster than anywhere else in the city, and desperately needs a subway system, cannot seem to add one. Does anyone know the future plans for this?
It was designed with light rail conversion in mind. It will likely eventually become a hybrid - trolley for SB Waterfront and bus for airport terminals in the same tunnel. There are examples of this around the world.
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Old 01-02-2014, 11:05 AM   #4
BussesAin'tTrains
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Re: The Silver Line

As has been said, it's fairly simple to convert it to LRV, but there's no point to doing it until it can be tied in with the Green Line, and that costs a lot of $$.
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Old 01-02-2014, 11:34 AM   #5
F-Line to Dudley
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Re: The Silver Line

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Originally Posted by stick n move View Post
Does anybody knows why this line cannot be turned into rail? It seems like it would be relatively easy seeing that there are already underground stations, tunnels, and routes. Also there is even some rail lines already in the seaport that are not being used that could be added in. I just dont understand why this area that is growing faster than anywhere else in the city, and desperately needs a subway system, cannot seem to add one. Does anyone know the future plans for this?
Phase III was canceled because building a BRT tunnel through Chinatown and Boston Common was too devastatingly expensive and all-around devastating to historic structures. They had lots of trouble fiddling with a workable routing before throwing in the towel.


It would be FAR easier to do a light rail link off the unused portion of the Tremont St. tunnel:
-- Tufts Med. Ctr. station underneath Eliot Norton Park with approx. 1-block walkway connecting to the Orange Line fare lobby.
-- 1-block extension of the subway down Shawmut Ave. to Marginal Rd. with dip under the Orange Line tunnel at the corner of Marginal.
-- 2 blocks down Marginal, turn onto Curve St...staying just inside the Pike and Surface Rd.-to-Pike ramp retaining walls.
-- Along Hudson St. or safely clear of the Dewey Sq. Tunnel wall along Surface St., under Chinatown Park, and connecting with the end of the Transitway tunnel under the park at the corner of Essex and Surface.

Keeps to mostly non-disruptive urban renewal or Big Dig-cleared land where the under-street innards are well-documented, avoiding the fatal flaw that killed the BRT link. And the only tough structures to slide past would be the Orange Line tunnel and the "Welcome to Chinatown"-adorned building on the corner of Surface/Hudson and Kneeland. Don't get me wrong...this is a very expensive project. But it can probably stay < $750M at worst (maybe $500M at best) whereas SL Phase III was bloating to well over $2B and probably >$3B with all the escalating complications.


Once inside the Transitway it's easy, as there are working examples worldwide of dual-mode tunnels that would operate the same way and the Harvard bus tunnel had 2 decades where trolleys and TT's overlapped.
-- Bury rails in the Transitway pavement.
-- Install wire clips compatible with both trolley pantographs and Trackless Trolley poles. The Green Line used these in the era where pole-equipped PCC's and pantograph-equipped LRV's overlapped in service.
-- Modify the wire hight so the live power wire is a few inches lower than the neutral return wire and can't be shorted out by a trolley pantograph (only rubber-tire vehicles use the second wire; trolleys are grounded to the rails and disperse their return current there). The poles on a TT easily flex to different height.
-- Whatever power upgrades are needed for the increased load (although that'll probably be included with and originate from the connecting tunnel rather than the Transitway itself). Both modes use exactly the same voltage.
-- Install Green Line wayside signals. On today's GL signal system it's all operator-controlled obedience of the line-of-sight signals, so it would be no different on trolley or bus. If the Green Line were to go to all or partially onto some sort of automated CBTC signal system, as long as the co-mingled portion of the Transitway has fixed blocks and those blocks are still marked by those traffic light-style wayside signals, both modes can still co-exist same as ever. The only difference would be that the trolleys would have automated stop and speed limit enforcement while the buses still require operator obedience, and you wouldn't be able to set up the CBTC signals as moving blocks (not a big deal in a stretch as short as the Transitway, and it's debatable whether moving blocks are even possible anywhere on Green).
-- Fix the D St. light with a proper tunnel extension. And fix the SL1-to-Ted onramp situation while we're at it.
-- Install a turning loop next to Silver Line Way and small trolley layover yard. Something that can fit a couple four-car trains is probably adequate storage provision, since this isn't a particularly long run from the big carhouse being built for GLX. Buses continue looping at South Station, trolleys loop at SL Way. Make this the inbound terminus for Medford trains.

The last 3 points are things they pretty much need to do anyway just for the buses, so this part isn't major construction at all. Existing stations would require zero modification because the platform height is the same, and the existing turnout spaces by the stations for pulling buses out of line or passing buses can be used similarly to keep the buses away from the trolleys (or vice versa is those bus turnouts are overlaid with track turnouts).



Once you do that you've got capability to do street-running branches to the heart of Southie, like a revival of the old City Point branch that ran into the Subway until the mid-50's. But I don't think that's a pressing need if the SL buses serving those areas gain such fast, immediate, closer transfer options.
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Old 01-02-2014, 03:53 PM   #6
PaulC
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Re: The Silver Line

F-Line I know you've posted that all new T construction is to Red Line standards, does that include this Silver Line tunnel?
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Old 01-02-2014, 04:24 PM   #7
F-Line to Dudley
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Re: The Silver Line

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F-Line I know you've posted that all new T construction is to Red Line standards, does that include this Silver Line tunnel?
BRT tunnels are wider than anything rail because it's not a fixed guideway. So the Transitway has pretty generous-sized bores. That was another strike against Phase III...tunneling under narrow Essex St. is hard enough without it having to be wider than a rail tunnel to fit a bus.


Any rapid transit rail tunnel is going to be built to NYC Subway B-division dimensions (i.e. Red Line), since that's the most common subway clearance spec in the entire world and closest thing to a de facto standard. Doesn't matter if nothing that big ever runs through it or ever has possibility of running through it because of the connection to the tighter Central Subway...it's easier to engineer to a standard spec vs. a custom spec. Safety in numbers when you're talking worldwide subway construction expertise and economy of scale. The only time--in the absence of truly unusual tight constraints--that you'll see a custom-dimension tunnel is when it has to go wider than the norm for BRT or some ultra-widebody form of heavy rail like BART.
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