If NYP-PHL supply meets current demand what would then gain by adding an additional train between them? If NYP-WAS demand outstrips current supply then it makes sense to provide additional supply.
Think harder. If NYP-WAS demand outstripped supply and NYP-PHL demand didn't, you'd see empty seats from NYP to PHL which got filled from PHL-WAS. Instead you see full seats from NYP-PHL which are empty from PHL-WAS. This says that you need NYP-PHL short hauls to take the NYP-PHL customers (which will then open up seats on the NYP-PHL-WAS train).
Alternately even if NYP-PHL demand isn't meet, given the finite resources available to Amtrak, If these resources can yield more profit by being utilised on a direct NYP-WAS compared to a direct NYP-PHL service
Mathematically that's impossible. Literally impossible. I won't leave it as an exercise to the reader; I'll explain:
First of all, the costs are obviously higher to run from NYP-WAS than from NYP-PHL.
As for the revenues -- whatever revenue you were hoping to make for NYP-WAS, you can instead raise ticket prices on NYP-PHL to collect the same (or more) revenue. If this price increase reduces NYP-PHL ridership, *then you opened up seats for NYP-WAS* and you get your NYP-WAS revenue. You end up with more profit.
I do financial analysis for a living.
@neroden While that is logical, that also presumes the availability of equipment
and slots. Both constraints are at issue...equipment can be dealt with in the form of an order for new cars over the next few years, but particularly at peak hours Amtrak can only run so many trains through the Hudson tunnels. Moreover, if both markets can be supported (and PHL-WAS and the intermediate pairs can still support a train without as much through business) you achieve the same objective by pushing through pax to the express train and moving local pax to the stopping service.
It is true that if you have enough non-stop customers (I don't think there are enough) you can achieve the objective by running a non-stop. If you have unbalanced ridership where NYP-PHL is stronger than PHL-WAS (which you do), the nonstop will exacerbate that unbalanced situation on the other trains. Eventually some of the other trains will be running with low enough ridership from PHL-WAS that you'll want to cut them back to short turns from NYP-PHL, and you end up with the NYP-PHL short turns again.
In some respects, this feels like the equivalent of saying that the New York Central shouldn't have run the Twentieth Century Limited or that the ACL/SAL shouldn't have run their Northeast-Florida express trains, they should have laid on a few more multi-stop trains when the endpoint market was big enough to accommodate the express service. In both cases, the cachet of non-stop/express service can be a significant selling point.
And that may be the only purpose of this: advertising.
When the endpoint market for the Twentieth Century Limited dropped, the first thing the NY Central did was to have more intermediate stops. The limited-stops trains outlived the no-stop trains by decades. The Twentieth Century Limited, in its heyday, existed alongside a bewildering array of locals, limiteds, and semi-expresses departing many times per hour. And it *can't* exist without that sort of extremely high demand. While the NEC does have its MBTA, Metro-North, NJT, SEPTA, and MARC locals and limiteds and its Amtrak limiteds, semi-expresses and expresses, I don't actually think there's enough demand there to support a NYP-WAS non-stop on top of it. OK, I think there is enough to support an NYP-PHL nonstop, but the Washington leg is much, much weaker.
Thinking of it as a marketing scheme, I expect them to run non-stop just long enough to get a bunch of positive publicity in the newspapers. Because "non-stop" gets more marketing hoopla than "one stop".
Then, because I believe the endpoint market is *not* large enough to fill the train, they will quietly start stopping at Philadelphia. I believe that the market for a one-stop *is* large enough to fill the train, so that's probably what they'll stick with...
FYI. In order to fill one non-stop train each way every day, I calculate that they'd have to take roughly *30%* of the existing Acela NYP-WAS ridership onto that train. (And, BTW, Acela ridership has been dropping the past two years.) That... might be possible? But given that people will take the train which is on the most convenient schedule, it seems highly unlikely. The train will run underfull until they add an intermediate stop. Add enough intermediate stops and you can take a more reasonable 20% or 15% of the ridership and fill up.
I suppose Amtrak is trying to capture people who were taking the airline shuttles. That is a pretty small group at this point. I cannot find current numbers for shuttle ridership. Some people are actually plane-lovers. I believe the number who can be captured is not enough to fill a train (namely, for a nonstop in each direction, 221,920 per year)