I tried a harness too but got too complicated to undo and my dog kept chewing it. Gave that up and she lies in a transport cage that takes all the back of my car. Had no choice after one seat belt has been dammaged as well as whatever was in the car!. When she is in her "car home", she just goes to sleep or sits up and looks at the road, cars and other things she would like to run after (the back of my car has a large rear window so, plenty to look at during a long journey). No room left in my car but a good solution for my Basenji, when I open the door of her "car home", she waits until I have put the leash on and then jumps out, well attached. If I take her with me in a friend's car, she sits on the back seat quietly BUT no way, can I leave her alone in that car, she would destroy everything and pee on the seats !(from past experience, not much fun for my friends)