your doubts are correct, acetaminophen od is not a good method, It might land you in the hospital but very likely will not kill you. Sadly over the counter medicines are not reliable options in general, (I've heard that it depends on what counts as otc where you live, but if you are in the uk/us/somewhere with similar laws otc is absolutely not the way to go.) I'm not trying to fear monger, I say this because I have tried to od on similar meds before doing research and it only resulted in extreme discomfort. I would take a look at the sticky thread
non-methods that should not be attempted, if you havent already. For trains it depends on the speed and positioning, i was not able to find a megathread for this method but I can try to find some sources if you like. sorry i cant be more helpful, i hope you're able to find what you're looking for :(