system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the reasoning behind how trains are loaded?

I see trains everyday and I’ve never understood how/reason behind how rail cars are organized. I see 3x fuel cars then 2x box car, and finally more fuel cars. Why not all the fuel cars then box cars?
gpt
They are generally arranged by how they are picked up and delivered.  It's much easier to pull into a place and unhook the last five cars, then go to the next place and unhook the next 8 cars, etc., then to have to go to each place, unhook cars 1-6, and cars 7-12, then connect to cars 7-12, then move them, then disconnect them, then reconnect cars 1-6, then reconnect the rest of the cars, etc.