There should be a special kind of etiquette for the 5:30 A.M. Acela.
The train is chilled - extra AC to keep the business travelers from wilting. My neighbor first exists as a jolt from the stillness of the stopped train. I am asleep or pretending to be asleep or just wishing I was asleep. Leaning against the window with my jacket bunched up for a pillow, I've left teh arm rest empty so at first my neighbor exists as warmth.
Our arms must only be a centimeter apart, our shirts must be touching. Chilled from the train, his warmth, in my sleepy mind, glows like small sun radiating heat into my arm. I can feel it spread down to my elbow and up into my achy shoulder. This little warmth is all I need, and I am asleep and dreaming.
I wake up at the Trenton stop and, as I write this, we've just passed Secaucus.
Forget about using your inside voice, everyone should work on using their 7:00 A.M. train voice. My neighbor stretches awake. This is novel -- waking up next to a stranger, but fully dressed and with no hangover.