Do they add to your economy in a way that harbors alone don't? Are they really a good addition to your overall economy. I know they are a "force multiplier" in military terms, but is that a good reason to build them? I'm experimenting with not building them at all. I realize that developing the technologies is essential, but that doesn't mean one has to build instances of them. [EDIT:] I just won a science game without building a single road or railroad. Seems like it was maybe faster than building them.