I am currently writing a very detailed and long outline for my idea. I have decided to stick with the idea of Aliens that have invaded the train. However, as I am writing out my outline it has made me consider that possibly it would be better to make my idea into a TV serial as there is a lot of information that I am writing down and I don’t feel as if it would all fit into one film unless I make it a film series which is what I wanted to originally avoid. But if I was to make it a TV serial I would make it a one off (3 episodes), with each episode being 50 minutes long. I am going to carry on working on the detailed outline then start breaking it down into the 3 Act structure.
After much thought on this, I have decided to keep my idea in the format of a feature length film.