My dogs absolutely LOVE car rides. Unfortunately my main dog Sadie can NOT ride in the back of a truck. We tried in the neighborhood going extremely slow the first time. As soon as we slowed down to barely moving she bailed over the side. I heard her hit the ground and freaked out. Thankfully we were only going about 5-7 mph. She scraped her chin and chest and got right up, she's a bulldog so she's tough. I was in a complete panic. It hurt me more than it hurt her I'm sure of it. I swear she just wanted to be next to us.
Now Sadie and my foster dog Willie ride inside the vehicle with me with the ac vents blowing on them (we live in Florida). I roll the windows down when we aren't going too fast. They love to stick their heads out or rest them on the window ledge. I can see their heads in my rear view mirrors and watch their noses twitch as they take in all the smells and their ears flap in the wind.
They do say that car rides are good exercise for dogs because they use their nose (insert scientific name here) muscles so much. Of course they should always still have their normal exercise but car rides will suffice sometimes and burn up some of their energy in the event you just can't walk them that day. My dogs are also covered under my insurance policy but not completely.