I understand that it might be against the ticket rules, but out of curiosity: Is it really realistic that the ticket would be cancelled if one boards the train one stop later? What exactly triggers the cancellation of the ticket? If the conductor only sees the passenger after New Haven, that could be because of other reasons than late boarding (maybe the conductor missed the passenger before). It's not like a plane ticket were there is a clear checkpoint where the ticket is scanned?
I've missed a train before where it was a conductor allowing all coach passengers on at one door, and it wasn't cancelled, so it's most definitely not immediate. There's supposed to be enough of a grace period for the passenger to maybe cancel or exchange before it's completely forfeited. I've heard two hours, but I can't find any official message on this. However, there may be the possibility at a station like NYP that they mark any no shows immediately after they close the gates. NYP is the only Amtrak station I've ever been to where there's that kind of passenger control, where it's a station-based employee checking tickets similar to gate agents at an airport.
The Amtrak terms only say that there's no refund for boarding at a later station, implying that the passenger might want (but can't get) the fare difference refunded back The no show policy sounds like it's immediate, but in my experience it hasn't been.
Looking to change or cancel your reservation? Learn more about our refund and cancellation policy.
www.amtrak.com
“No Show” Policy: If not canceled before the scheduled departure from the origin, the ticket is forfeited, and no funds or points can be applied toward future travel.
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Boarding Late or Leaving Early, Downgrading
No refund or exchange credit is given if a customer boards a train at a station beyond, or detrains at a station before, the station from or to which he or she was reserved, or if the customer downgrades accommodations on the train. To receive a fare adjustment the customer must change the reservation before the train departs the original boarding station of that train. This restriction will not apply if there is a service disruption. Customers who downgrade accommodations or reduce the number in their party on board trains must obtain a Refund Authorization Form from the conductor.