http://www.geek.com/wp-content/uploads/2015/07/Metro-Head-590x330.jpg
I found this article pretty interesting. There were no vehicles in Fallout 3, instead you wore a “train hat”.
That’s thanks to an updated version of the Creation game engine, but before Creation, there was Gamebryo. This is the game engine that powered Fallout 3 and New Vegas, and it had an interesting set of quirks. After poking around in the game files, someone on 4chan noticed a fantastic detail — there’s a hat that is literally an entire train.
Gamebryo was not really designed with vehicles in mind. When you think about it, Skyrim is all horses and walking, but all the cars are wrecked in Fallout, so vehicles don’t come up much. There are a number of workarounds to make vehicles work the few times they appear. For example, the Fallout Vertibirds are just pre-rendered animations that don’t operate inside the physics of the game.
The camera effect made it appear as you were on the train.
There’s another trick when you actually board the train, and it’s almost as weird. Again, there aren’t physics for making a train car move in the Gamebryo engine, so you’re not actually on the train. Instead, the player is equipped with a piece of head armor that covers the field of view and looks like the inside of a train. Then a camera animation is played that makes it look like you’re on a moving train, but you really just have a helmet on.