Tam, at least you had the dog confined. Yes, the carrier could get thrown around if you had an accident.
I just don't get the people that drive with their dogs bouncing around on their laps, to the back seat...I could not drive well, if my dog was all over the place.
For years I drove a hatchback & would tie the dogs on the side loops with a short leash. It wasn't as good as the seat-belts they have now but, I felt better knowing they would stay back there.