Genuine question: why don't they just start the train? Best case, the cat jumps off. Worst case, it dies but the train continues. Is there something else? Is the presence of the cat on the roof a safety issue?

Edit: I'm asking from the train operator's perspective. Obviously we want the cat to be safe and well, but a train company with a timetable doesn't care about that, so I wondered what's actually stopping them from just starting the train and potentially killing the cat.