Tosh. If you substitute the term "responsibility" for the often mis-used expression "duty of care" then, in the circumstances described above, it is very difficult to see why a TM should have responsibility for the actions of the person who throws himself under the next train, or trips up the subway steps. This would be like saying that the person who sold a pax a ticket at the booking office has a duty of care for that pax until such time as he (the pax) gets home (and maybe even, then too!).
A duty of care will exist if there is a relationship created whereby one person/body has a legal responsibility for the safety of another and that responsibility has not ended or been superseded by another intervening act. The pax getting off the train, voluntarily or otherwise, will be such an intervening act (novus actus interveniens for you Latin scholars).
In my eyes, I have a duty of care if the passenger has a ticket.
