So a lot of people think I'm crazy, but I like to put my dog in her seatbelt when she comes with me on trips. I like to know that she is as safe as I am. Yes, she hates it at first, but then she realizes she can't fight it and then lies down. It has a fleece inner linning so that it's comfortable agains their skin and it hooks right into the seatbelt. We got ours from bed bath and beyond but you can buy from pretty much anywhere.

I think the seatbelt is great.  I have Kimba ride in our CRV behind the back seat in the cargo area.  The seat  is above her shoulder so it would help in case of an accident and I have a gate too,  but I think the seatbelt is a safer idea.