What is about train seats that induces sleep? I cannot go a single seated train journey* without the head starting to loll, the eyelids beginning to droop and then that sudden jerking of the head accompanied by a half-snore, half-snort that amuses the rest of the carriage (although, being English, everyone will do their best to not look too amused). I did it on the way home just now and, perversely, it makes me feel even more tired by the time I get home.
It's not an age thing, either - I've done it for years. Sit gained, wakefulness lost. There's got to be some sort of medical reason for it. I can't sleep in cars, buses** or planes but stick me in a train or a tube and I'm away. Maybe someone should do a study.
As long as they wake me up in time for me stop...
* And, let's face it, there are precious few of those thanks to the ridiculously over-crowded nature of rush hour traffic, right, commuters? Yeah, right on.
** Excepting alcohol-induced unconsciousness on the night bus. There's no mystery behind the causes of that one. There's a mystery behind where the traffic warden's hat came from but not the boozy snoozing.