Just for the record, there are "animal activists" who would claim you were being cruel to your pet. If you slammed on the brakes, the dog would not be restrained and would fly through the window (unless, as they propose, you make sure your dog has a seat belt too.)
And as for people who's small pets ride in their laps duirng a car ride, a sudden stop, airbags deploy...bye, bye pet.
Our dogs ride unrestrained, but I know I've talked to a few "dog people" who thought we were being reckless. (main reason I'd like to restrain our Weims is they think they should be doing the driving and although they sit in the back, they'll often rest their head on the shoulder of the driver.)
Well, we have talked about a seat belt for her, but then she climbs over and falls asleep in Daddy’s lap. Awwwwww!