I have a small suggestion. When looking at the model, it looks a bit odd to look through the front window and to see right into the back of the train. You should make an internal wall, with a door, for a drivers compartment, that seperates the front section of the first part from the rest. And a small tip. I have a very low polygon model of a wooden mannequin that I import into every scene that I make. I just park the mannequin off to one side. This helps me to keep things in scale, and "grounds" me in a visual image from the real world, instead of just relying on measurements. It is easier to judge visually if a door looks too big if you can see a human shape next to it.

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