One of the things I've noticed travelling on the train is the number of people who lose their place momentarily. They might be reading, listening to music or just day-dreaming, when they suddenly realise that they don't know exactly where they are because they haven't been paying attention to the stops. They search the darkness outside anxiously for some familiar pattern in the lights and shadows.

It's happened to me a couple of times, and it's very disorienting. The odd thing is that you think that you know the line intimately, travelling on it every day. I think that the problem arises because the familiar landmarks are strongly bound up in their linear sequence; recognising where you are is rather dependent on knowing where you are in the sequence. Even in the daytime, if you lose your place along the sequence, it takes several moments to place what should be very familiar landmarks. Odd.