Gov or 1-800-252-8255). Your child will no longer need a car seat if they are at least four feet and nine inches, eight years of age, and the vehicle seat belt fits them properly.Texas law requires that young children use proper safety equipment when riding in motor vehicles to protect them in the event of an accident. It is important to choose the right seat for your child's size and make sure it is used correctly to properly protect your child in a crash. The law requires that the car seat is in the back, not the front seat. Some vehicles may not have that option, in which case you'll need to take it to a dealership to have one installed. Car-seat installation requires an appointment. Contact United Health System at (210) 358-4295. Additionally, children under the age of eight must ride in a car seat or booster seat unless they are taller than 4 feet 9 inches. Seat Belt: Children who are too big for booster seats yet still below 17 years of age must wear a seat belt as per Texas law.