Hmm well Im still a noob myself to FPSC, but I can give some suggestions that maybe another member could maybe answer for you.
Have a train model which you spawn in or whatever.. Keep the player inside the train. maybe have some windows that are barely visable out of. maybe have moving entities outside the train that continues in a set path that goes by the window giving a impression that your moving.
Have a background sound of the train engine/tracks playing while inside. maybe have some effects outside such as Smoke flying by the windows also.
Not sure what else you could do to make this possible. But thats my best guess.
Good luck with this
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Interested in making games. Yea im a newb, but I could create the next big hit! So keep a EYE on me