What a take on the theme! I really liked having your number of carriages linked to your speed, though it could probably use a bit of fine tuning as with very few carriages the train becomes incredibly difficult to control, which I assume was not the intention. It would also be nice if there was a way to choose which carriage to eject as well, and it would be nice if upon collecting a carriage it immediately attached itself to then end of the train rather than moving slowly along the other carriages, which I think may be the cause of the glitch where the carriages get tangled.
Also I really like the music, the calm theme suits the atmosphere very well and it is cool how it seamlessly goes from calm to "you are getting shot!!", however during one of the days I happened to run out of fuel while getting attacked which caused the bandit music to continue playing, and when I ran into another bandit another layer of the bandit music was added on top until I went out of range.
Overall great stuff though!