HeeHee - Charlie adores riding shotgun! He says he doesn't care that it's not safe! He also has only been allowed to do it once or twice in a Landie.
The completely paranoid about doggie car safety side of me loves this thread. I'm bit obsessive and always do the harness plus seat belt thing. With puppies (or small dogs - my friend's chihuahua for example) they are in a crate which is tied down to the floor of my car. I get teased about this a lot, so I'm really happy to see I'm not the only one who does this!
We do use a crate that fits in the back of my Subaru. I have a cargo strap that ties it down on each side to the floorboard of the back. The crate is not a special crash tested one but a big metal one. Maybe I should look into that. With the difficulty I have taking my dog places we don't get to ride much. He likes to go but is way too enthusiastic when we get somewhere.
My crate doesn't fit my new car, it's too high to fit in the back hatch door. It's wire so wouldn't pass any safety standards anyway. I've read at http://www.centerforpetsafety.org/ so know which crates are best at protecting the dog and me but still, they won't fit. Unless I have him awfully cramped in there. I do have a home made, OH built, barrier to keep dirty paws off my console and front seats when I leave the dog in the car to run in for a bit of milk or bread on the way home but it is in no way a safety feature for either of us.
Holly travels in the back of the car behind a dog guard. She lies on an old cotton cover (easy to wash), and has her towels and a few tennis balls for company. For long journeys we put her bed in the back. Most of the time she sits up and looks out the back window. On a few occasions we've been in a queue of traffic ans seen people waving to her!
Larks travels to work with me every day (30-50 minutes depending on traffic) in her crate. I've taken her shorter distances, say to the park or pet store without the crate but she doesn't seem to settle nearly as easily. It makes me feel like she is safer in her crate too, since she can't distract me too much.
Our Volvo has a built in dog guard. Homer has the whole boot which is just a bit more floor space than his crate would be and high enough for him to stand but mostly he curls up against the back of the back seat. I do wonder about his safety if he's thrown about in a serious accident.
After having this discussion with OH my little sports car has been replaced with a nice 5 door grown up car to ensure maximum safety for the pup. It's definitely like having a child!