Instant Death

Massive damage can kill you instantly. When damage reduces you to 0 hit points and there is damage remaining, you die if the remaining damage equals or exceeds your hit point maximum.

Per Ghosts of Saltmarsh, a ship roughly trolley size (though ~¼ its weight) does 25d10 bludgeoning when crashing, (considering a trolley approaching a track switch tends toward 10-15mph, ramming rules seemed excessive).

The party restrained on the tracks may or may not be immobilized as well, but regardless: 25d10 bludgeoning may very well one-shot each and every one of them instantly, and then some.