As long as the animal is calm and situated inside the vehicle, I'm OK with it. I do get nervous when I see a dog roaming the bed of a pickup, or standing on a flatbed, however. That comes from witnessing a collision in which a dog was thrown off the back of the truck when it struck a pickup ahead of it.
I know of one person who has and uses a doggy seat. I think it actually is a bed, but it does have a seat belt. I know of another person who puts her dog in a harness, then attaches it to a seat belt. And I've heard more than one traffic officer and driving instructor say the animal should be secured so as to avoid it causing a distraction for the driver or a safety risk for itself.
They always recommend — and rightly so — safety first when transporting an animal.
By the way ...
George said he did not use restraints on Candice or Justine, unless they were in his pickup. There, they were on a leash so they wouldn't jump out. And, he said, he always gave them treats to keep them quiet and safe.
Enjoy your week and drive safely.