NEC Portal Bridge Thread - Operation, Replacement Etc.

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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby EuroStar » Fri Mar 16, 2018 7:13 am

Just in time for the ongoing battle for federal money for Gateway during this budget cycle, the Portal Bridge has decided to remind everyone how old and rickety it has become. The bridge got stuck open early this morning (5am or so) and has not allowed restoration of train service as of yet (3 hours later) messing up the morning commute for practically everyone who relies on the trains.

As a side question related to bridge operation, when the bridge gets stuck and the mechanics need access to the swing portion, how do they get there if the bridge is actually completely open as opposed to just misaligned at closing? They obviously do not swim and I doubt there is a boat anchored next to the bridge at all times for just this specific purpose. Or has this never happened?
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby amtrakhogger » Fri Mar 16, 2018 1:39 pm

They do have a boat on site in case the personnel need to get to the bridge if it is stuck open.
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby EuroStar » Thu Jun 14, 2018 7:28 am

OK, wow, the bridge is actually getting some money from NJ. Hard to believe, but who knows, maybe finally we will see some real progress on this. https://www.railwayage.com/passenger/commuterregional/njt-600mm-for-portal-north-bridge/
The resolution authorizes NJT Executive Director Kevin Corbett and New Jersey Department of Transportation Commissioner and NJT Board Chair Dianne Gutierrez-Scaccetti to execute and deliver the funding agreement with the NJEDA, which will issue up to $600 million in bonds from the state’s Transportation Trust Fund (TTF), to be repaid over a 30-year term. This same funding structure was utilized in 1999 for the construction of NJT’s RiverLINE light rail system.


The article claims 10% increase in peak hour passenger capacity. That seems bogus to me -- I thought the tunnels were the limiting factor on the number of trains during peak hour. The only way to increase passenger capacity is to add more cars to the trains that are not 10+ cars already, but the bridge is not stopping them from doing this now -- it is not structurally deficient. The new span will allow speeds to be jacked back up to where they used to be, but that will be mostly reliability and fluidity improvement. Even that will be marginal given that so many NJT trains need to stop at Secaucus.
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby R&DB » Thu Jun 14, 2018 8:59 am

EuroStar » Thu Jun 14, 2018 8:28 am

I thought the tunnels were the limiting factor on the number of trains during peak hour.

Portal Bridge and North River (Hudson) tunnels are both two tracks. Rest of the NEC from NYP to PHI is 3 or 4 track. Portal and tunnels are 100+ years old.
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby andrewjw » Thu Jun 14, 2018 10:41 am

The capacity increase could come a few ways

  • Perhaps there is currently a rule against running at max capacity in case of bridge issues
  • Block signalling means that increasing the speed of the trains increases the throughput. If the max speed on Portal is lower than the max speed in the North River Tunnels...
  • Trains stopping at Secaucus v. skipping it mean intricately-timed mergers. The throughput increase at Portal could translate to an overall throughput increase even if the North River Tunnels have always been the bottleneck component, because a better Portal bridge means trains can run closer together (in time, due to higher speeds) west of Secaucus, allowing more scheduling flexibility east of Secaucus.

Say the old schedule required 2 minutes between each train in the NRT and at Portal each, and a Secaucus stop takes 3 minutes, and every other train stops at Secaucus. Before, if you tried to have trains out of New York every two minutes arrive at Secaucus at :00 (through), :02 (stopping), :04 (through), :06 (stopping), etc... (30 tph) which then depart at :00, :05, :04, :09, etc... but the departing trains must wait a minute to have the signal clearance, holding up incoming trains, since they can't be less than 2 minutes apart. So instead you have to run trains at :00 (through), :03 (stopping), :05 (through), :08 (stopping), :10 (through), which depart at :00, then the :58 leaving at :02, then the :03 pulls in, then the :05 pulls through (it can't be at :04, two minutes after the previous departure, because then it would be too close after the :03; the :03 can't be earlier because then it would have a conflict with the :58's departure), etc... and now the :03 can't leave until :07, hand the :08 pulls in, the :10 pulls through, the :08 leaves at :12 so the :13 can pull in, etc... and we have 20 tph.

But the new Portal Bridge with higher speeds might allow for tighter clearances west of Secaucus, so now our original :00 (through), :02 (stopping), :04 (through), :06 (stopping), etc... (30 tph) which then depart at :00, :05, :04, :09, etc... are allowed, because the higher speed means that the one minute of time clearance is enough space clearance, say.

Fill in whatever the correct values of 2 minutes (max frequency through NRT / old Portal), 3 minutes (Secaucus stopping time), 1 minute (max frequency through new Portal / clearance needed at Secaucus) etc... are for the actual physical constraints - my numbers are probably too low. This is just an example of how changing Portal capacity could increase throughput even if the NRT are still the bottleneck.
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby Defiant » Thu Jun 14, 2018 2:53 pm

So does anyone know what the cost is for total replacements project? Who is going to pick up the rets of the cost? Will this be an Amtrak run project or NJT project?

Sorry for asking so many questions but there isn't that much specific information that I could find on-line...
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby benboston » Thu Jun 14, 2018 7:20 pm

https://www.youtube.com/watch?v=yD5mm8FI5hM

This could be a slight problem as well
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby east point » Sat Jun 16, 2018 1:24 am

When the north portal bridge is open the present plans are to keep the swing bridge in operation. That will allow slower trains to be passed sooner. A lot depends on how soon the 4 main tracks are built from Newark to the new tunnel bores exit. At present there appears to not be any plans to build the sections that are not at present 4 track.operatable from the
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Re: NEC Portal Bridge Thread - Operation, Replacement Etc.

Postby EuroStar » Mon Jun 18, 2018 8:23 am

east point wrote:When the north portal bridge is open the present plans are to keep the swing bridge in operation. That will allow slower trains to be passed sooner.

Do you have a source for this? I believe that it is not correct.

While in theory the existing bridge could be kept and used as a stand-in for Portal South, there are multiple reasons why this is unlikely. One, the prospect of 4 tracks between west of Secaucus Junction and Newark within the next 20 or so years is nil. First, no more tracks can be threaded under the turnpike unless the supports of the turnpike are modified. Second, whoever designed Secaucus Junction did a HORRIBLE job east and west of the station and the space for the fourth track is not there. The middle track east and west of Secaucus is really in the middle, so the bridges and the viaducts need to be rebuild at an enormous expense just to move that track a bit to make space for the fourth one. It is such a terrible design that Amtrak has thrown in the towel and plans to have two new tracks to go through the southern portion of the existing building so as to avoid dealing with the existing bridges and viaducts. It is impossible to comprehend why they did not make tracks 2, 3 and B as straight as possible with A being "a siding" extendable to a 4th straight through track back in the day. That could have given them max speeds on 2,3 and B plus a slow speed A due to turnouts. Now they got max speed 2 and 3 plus expensive to upgrade slow speed A and B. The proper way to design a four track station is what was done at Newark Airport (sans the non-platform tracks). There the tracks are straight without S curves to accommodate switches.

So no, the swing bridge will not be kept and when eventually Portal South is built it will carry two tracks that will go south of the existing 4 at Secaucus. For all that we know they might not even have platform at Secaucus.
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