A 1-year-old child may weigh less than 20 pounds and should be riding in an infant safety seat or convertible safety seat in the rear-facing position. "To have them in a safety belt at that age is just ridiculous," [Herta B. Feely] says. "We would highly, highly recommend that people not follow the letter of the law, but do what's best for their children. And what's best for your child is to have them in a child safety seat until they're 40 pounds, and then after that in a booster seat." (The best booster seats have a safety shield and use a shoulder harness, she says. Keep them in it as long as they fit.) A child using a safety belt can be thrown about somewhat in a crash, depending on how tight the belt is. "The other main thing that happens is hyperextension of the neck and vertebrae, and that causes neck injuries, spinal cord injuries. They can become paraplegic or quadriplegic."