When I lived in California it was common for dogs to ride in the beds of pick-up trucks. Because dogs were getting injured or killed or they caused traffic accidents, laws were made to dictate that the dog must be secure and not be in any danger.
I was in a chain reaction accident on the freeway once when a dog was riding on a flat bed truck and jumped off the truck in the middle of the 8 lane freeway. Cars were breaking and swerving all over the place. The car I was in did not hit anyone in front but got rear ended by a car that also got rear ended. The dog was hit but ran off into traffic. I never did find out what happened to the dog. I don't know if anyone was injured but I am sure there was a lot of property damage.
When I moved to Oregon years ago, I was surprised and relived to find out that most dogs that traveled in the back of pick-up trucks were hunting or ranching dogs. Those dogs are very valuable to their owners and those owners treated them right. The great majority of dogs travel in dog boxes that fit into the truck beds. They are pricey little truck accessories that are mostly made of stainless steel.
It is nice to see that some parts of the country treat their dogs like the precious cargo that they are.