I don’t know. Back in the 70s, my dog traveled thousands of miles loose in the back of a pickup. If the crate was properly secured, the dog wouldn’t be in significant danger.
Many of us have traveled in the back of a pickup, the Brat, used to have seats back there.
You didn’t put your dog on the roof for a 650 mile trip on the interstate though, and when he got sick from it, you didn’t merely hose him and his cage down, and hit the 70mph freeway again.
My guess is that you would have kept him in the bed of the truck.