Mine are always secured in the car. I would hate it if I was in a car accident and my babies were injured flying through the car.
The Yorkies are harnessed into booster seats in the back seat generally but I do have to move a booster seat to the passenger seat (air bag off) occasionally if taking all the dogs. A golden and 2 booster seats don't all fit on the back seat of a small SUV. Buddy wears a harness in the car.
Crates don't fit in my car.
One day I am going to upgrade for the dogs