I'm a bit confused on how this achievement is supposed to work. Do you need to have the vehicles all active on the line at the same time or just have 1 of each vehicle active on the line at some point in time?
I'm trying to complete everything while playing normally, such as having actual lines serving a purpose instead of having a line off to the side in the middle of nowhere that I can just pile the vehicles up on, and it's becoming a bit of a nuisance having everything pile up behind a 18km/h wagon.