It's not exactly traditional cargo but unique nonetheless. That's the Amtrak auto train where you can pay to have your personal car loaded on those car carriers before the train departs. The train will only load and unload in Virginia and Florida. Makes it real nice to be able to take a train somewhere and still have your personal car to get around after.
But of course this comes with a much larger ticket price.
Handlers load your car into sections of the car carriers while the passenger cars themselves sit in a separate area nearby for boarding, once everything is ready the entire train is coupled together making for an approximately 4500ft passenger train.

“A designer must always think about the unfortunate production engineer who will have to manufacture what you have designed; try to understand his problems.” - Raymond Loewy