Congrats on making your first Fermi! You are taking the first step on and a long and rewarding journey of quantitative rationality :)
As for q1, claiming that the world has a billion train stations seems way too high to me. That would be enough for every two families to have “their own” train station. But when you look at the throughput of passengers there’s 1000+ at least per station.
I also think you’re neglecting the fact that train stations are connected to each other, and so end up double counting some tracks?
Congrats on making your first Fermi! You are taking the first step on and a long and rewarding journey of quantitative rationality :)
As for q1, claiming that the world has a billion train stations seems way too high to me. That would be enough for every two families to have “their own” train station. But when you look at the throughput of passengers there’s 1000+ at least per station.
I also think you’re neglecting the fact that train stations are connected to each other, and so end up double counting some tracks?