Why do certan trains use different cars to haul the same thing[?][?]
What exactly do you mean?
There are all different styles of covered grain hoppers, but generally speaking, if they are sound and fit for transport then the railways will use them.
There are also many different styles of boxcars, but generally speaking as long as they are still possible to use, railways will still use them
There are different styles of intermodal cars, mostly because they have developed over time.
As soon as something new comes out on the railway, everything just doesn’t switch over, it, generally, takes a long time before old cars are eventually scrapped.
Heck there are still lots of locomotives out there in revenue service that date back to the 1970s.
Do you have any examples? If you are talking about bulk commodities being shipped in boxcars. If that is the case it is probably because the received wanted to in small packages for some reason. If you are talking about something like sodium hydroxide being shipped in solution in tankcars and as flakes in hoppers, it is probably because the process the NaOH is going to requires it in a certain form.
Because different cars are manufactured by different companies at different times to different designs.
When you drive to work in the morning look around you. There will be thousands of different vehicles (cars) all carrying the same commodity (commuters). They will be all different shapes and sizes and designs. The reason they are different is the same one that the railroad cars are different.
Dave H.