There is no progression to this story. Although it is a harem, there are only two moments in the series that could be considered "plot development between characters" in which two different girls' announce to the screen that they have feelings for Naoto, our main character. However, while both of these girls may have revealed their feelings (to no one in the story), the only effect this has on the story is the addition of blushing throughout the otherwise ordinary moments this show is chock full of.
The only notable plot progression throughout the series is the very arbitrary promotion of Naoto from "kid who works for train station" to "kid who leads other kids who work for train station" which has no actual importance on the series as he is bossed around enough by his incredibly tsundere teammate that his title is meaningless. Aside from this tidbit of progress, nothing resembling a plot will occur for the rest of the series. You may be thinking, "well, that's okay. I'm just in it for the fan service anyway" and this is where I will have to stop you. Unless you, along with the writers of this show, are deeply infatuated with girls removing their pantyhose in a two-shot still frame every few episodes, you will be very hard pressed to find yourself satisfied in any way.
Much to my surprise, Rail Wars falls extremely short in the fan service department. Given that this is an ecchi harem show with no plot whatsoever, no character development, no relationships, and terrible animation you would think that we would at least get some Grade A boobies in our faces every few minutes, and although literally every female character with any significance has an obnoxiously large chest, we are left with pantyhose removal every few episodes and the occasional heavily-veiled changing room scene. If sexual tension is all you need, don't continue watching after episode two, where we get our one and only moment of actual tension which last about a minute and produces microscopic amounts of embarassment between the two characters involved. (Of course this is assuming that girls taking off their pantyhose doesn't completely captivate you, because the writers REALLY just eat that stuff up. When that still-frame passed and Sakurai's legs turned from darkish tan to light peach I knew my world had changed forever)
If you're still thinking "I'm just in it for the trains!" you are still not safe from the disappointment. Two or three times per episode, as a different 3D model of a train scrolls across your screen, Naoto will read to you the first ten sentences that wikipedia has to offer about that specific model of train. This interaction will then abruptly end and the show will continue normally, although occasionally a female character will comment on Naoto's obsession with trains which will result in the cheerful laughter of his teammates while the camera pans away to a fade, and we can escape from the tedium of Rail Wars! for just a moment.
Probably the only interesting aspect of Rail Wars! is the immense responsibility that these junior train cadets in training have, as they are equipped with pistols put in charge of defending the lives of thousands from a multitude of train-hating terrorists. While this may sound entertaining, I assure you that any conflict or action will take place in the final minute of the episode and be portrayed through a still-frame of a bad guy getting kicked by Sakurai. The ability of the junior train cadets to absorb minutes worth of tasering to the neck - completely unscathed - is notably comical yet also ruins any hope for the plot to actually start moving.
There is very little left to say about Rail Wars! If you are looking for 4 hours of large-breasted characters doing mundane things, poorly animated CG trains, 2 minutes of unfulfilling ecchi, half a dozen still-frames of action, and a small pamphlet's worth of information on trains, then Rail Wars! is the show for you. Otherwise, you should consider looking elsewhere.
