The Trouble With Trains

I live fairly near train tracks, so I can hear the train very easily when it goes by. Normally, this isn't a problem because I've gotten used to the trains, at least more used to them going by all the time than when I first came here, but last night, they kept up awake for a little bit. Now, whenever the train goes by, I always imagine it doing so, but last time was the first time that I realized that the train could go more than one way. I know that probably sounds weird, but it is true. I always imagined the train coming into town, but I never imagined it leaving town. However, since there are generally two train sounds within twenty minutes or so of each other, I imagine that one of those must really be a train departing. It is weird how sometimes you don't think of something so simple and then when you do, you wonder why you never thought of it before. Logically, I knew that trains must leave sometime, especially because we do have a thriving train station, but it just never occured to me to imagine it that way. I wonder what else there is that I haven't been thinking that must come from both directions but have only been looking one way for.