Seaport Transportation

real_EthanHunt

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real_EthanHunt -- The key is adequate frequency

So how do we insure adequate frequency -- make sure no bus is delayed by the effects of surface vehicular traffic -- in other words tunnel under D St -- so that some set of the buses [i.e. SL0] can loop from South Station to Silver Line Way entirely underground. The other Silver Line buses would be metered into and out of the stream @ Silver Line Way in such a manner as to not disturb the high frequency service [SL0]
they already run this route. SLW.

T under D is a waste of money. you can accomplish the same benefits for the buses by installing bus priority signals to cross D St.
 

ceo

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Oof. Don't hold out hope that ferries are going to lay off the diesel any time soon. Ship engine and locomotive engine diesels have an energy density that cannot be matched by any other onboard power source (and for boats, there's no option of tapping the external power supply efficiencies by running that thing under catenary).
The thing about ferries is you don't need the same kind of energy density. The Seaport ferry has a 15-minute run and a 5-minute dwell time at either end. I haven't looked up the numbers, but I expect that with a honking big charger at either end you ought to be able to give it enough electrons for the next run, with a significant contingency margin.
 

JeffDowntown

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they already run this route. SLW.

T under D is a waste of money. you can accomplish the same benefits for the buses by installing bus priority signals to cross D St.
Not the way Massachusetts drivers block intersections. Only way to ensure high throughput is to tunnel under D, as was always part of the SL plan.
 

Arlington

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Are there big utilities under D that stopped them? Or just nibbled to death in value engineering that caused it to not tunnel under D?
 

F-Line to Dudley

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Are there big utilities under D that stopped them? Or just nibbled to death in value engineering that caused it to not tunnel under D?
There was bupkis there before the Ted and first brand new building outposts came to that block post-'95, so nothing for utility blockers.

"Value" engineering FTW.
 

whighlander

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Not the way Massachusetts drivers block intersections. Only way to ensure high throughput is to tunnel under D, as was always part of the SL plan.
Jeff -- Exactly

Just look at what happened near to the former Suffolk Downs this morning when a Fedex Big Truck heading presumably to the Fedex Planes at Logan had some trouble on Rt-1A
If there hadn't of been a convenient industrial parking lot [perhaps where Amazon will soon be sorting deliveries/] -- things would have backed-up to Salem

As for the wherewithal for the Tunnel Under D -- Silver Line Way Station and accompanying parking lot -- ripe for Air Rights Development -- and in a doable way
This kind of Air Rights is just like the substructure under TD Garden -- no issues at all as you build it all at once with straightforward foundation construction
You can even do it Top Down construction if necessary to keep the existing Silver Line Way Station from being disrupted

  1. Start Tunneling in the current parking lot
  2. construct all of the turn-around and such by mining as you build the lower basement for the new building
  3. then build on site and jack the tunnel under D
  4. continue parallel to the existing ramp down to the World Trade Station platform
  5. Do all the wiring and finishing
  6. finally make the connection to the exiting platform [maybe a bustitution over a weekend]

Voila -- all electric uncorrelated with surface traffic looping from South Station to Silver Line Way Station -- SL0
 

HelloBostonHi

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Realistically any tunneling would be cut and cover given it would be barely subsurface, and would require significant service disruptions for several months along with road closures for a few months. A TBM wouldn't make any sense here, simple cut and cover would be far cheaper and quicker. And while I agree it would be great, it's still all for minimal benefit, most of what you propose already exists (a fully electric short turn silver line route known as Silver Line Way)
 

George_Apley

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Realistically any tunneling would be cut and cover given it would be barely subsurface, and would require significant service disruptions for several months along with road closures for a few months. A TBM wouldn't make any sense here, simple cut and cover would be far cheaper and quicker. And while I agree it would be great, it's still all for minimal benefit, most of what you propose already exists (a fully electric short turn silver line route known as Silver Line Way)
Roads can stay partially open with lane shifts and weight restrictions for cut-cover jobs, just like they do with utility work.
 

jass

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Realistically any tunneling would be cut and cover given it would be barely subsurface, and would require significant service disruptions for several months along with road closures for a few months.
You could do it in a weekend.

 

HelloBostonHi

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You could do it in a weekend.

While that is a fantastic bit of ABC its worth remembering that they did two years of prep work for that to take place. It would be more challenging in the SL transitway area, they staged the bridge on the future underpass, that would mean digging out part of SLW and staging there before rolling into place under D street.
 

bakgwailo

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I remember someone doing the math out awhile back (probably in this thread), with the results being that at needed headways/frequency, even signal priority wouldn't cut it.
 

citylover94

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The rule of thumb with signal priority is that the higher the vehicle frequency on the line you are giving priority to the less strong the priority can be or it would shut down traffic too much. Alon Levy talks about this some on his blog Pedestrian Observations.
 

Vagabond

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Oof. Don't hold out hope that ferries are going to lay off the diesel any time soon.
Not entirely true - depends what you think "soon" is. There are lots of efforts to do this. Norway has been pushing the all-electric ferries for a few years, and Washington State has already signed legislation mandating a shift to zero-emission water transportation.
 

bakgwailo

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What are the needed/desired frequencies?
Good question. I think peak headways currently are every ~2 minutes in the trunk. I would think in the not distant future that would need to at least double to keep capacity up with the growing seaport and logan.
 

JeffDowntown

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