Every state has automobile seat belt regulations. About half the states will ticket drivers solely on the basis of not wearing a seat belt, while the other half can fine drivers for it only when they're pulled over for another traffic violation. No matter which state you're cruising through, it's always smart to err on the side of safety and wear a seat belt -- passengers included.
If those passengers are of feline or canine variety, treat them with the same amount of care. As mentioned earlier, when traveling in cars with cats, they should remain inside a comfortable carrying crate since they're smaller and sometimes more difficult to control. Even if your cat rides in a carrier, it's wise to buckle the crate in or secure it in some way as well.
Naturally, you can't buckle in a dog in the backseat the same way you would a human. Most commercial pet seat belts consist of a harness that fits around the dog's torso and a belt attachment that snaps into your car's seat belt insert. These usually allow dogs to sit or stand up, but not walk around. Other kinds of pet seat belts provide for more mobility. They're similar to short leashes that attach to the car's seat belts. Dogs can walk around on these, and owners can adjust them to desirable lengths to keep them from jumping into the driver's lap. Smaller dog breeds may also fit snugly into pet car seats that also hook into the seat belt inserts.