I simply felt content reading this. Usually, I would think busy streets and traffic and other background noise in the middle of the night would be irritating to most people, and something they wake up from or can't sleep because of... Yet here, maybe there's comfort in hearing the rush of traffic (just like for me, where I live, we're close to a train, and it sometimes puts me to sleep). I also felt from reading this that it means you are not alone, in the sense that the world is still going on if you feel stuck or isolated, and knowing that is a relief. Or a break from what goes on in one's mind. Also made me think of poets and artists who are awake at this time (I'm guilty of this!), and it's when we find our inspiration. And the kind of awe in being awake in a city that doesn't sleep, not having to face the onset of anxiety with being alone to hear our thoughts amplified.
Anyway, this was full of imagery and I love brevity when it's used like this to allow the reader to interpret, or to simple experience the scene :)