I have always been amazed that when I'm up at 130 am, or 430 am, or anything I would call in the middle of the night, I have been able to look out of my window and see traffic on the highway. When we lived on Roosevelt Island, we had a great view of the FDR, which is the highway on the east side of the city. Now we have a view of the West Side Highway. Last night I was up with this stupid head cold, nursing a cup of tea to sooth my throat, and I was once again amazed that I could see cars on the highway. There was even a tug boat in the river, its lights sparkling in the water.
Other places I've lived, in the rare occasions when I'd be driving late at night (usually on my way home from or on my way to an airport), I would feel like I was driving in a ghost town.
There's something reassuring about being awake and knowing that other people are also awake.