Drivers can only let a child aged 8 through 15 use a standard vehicle seatbelt if they pass all five safety checks. If they fail even one, they must use a booster seat or child restraint. The 5-Step Test: Drivers can only let a child aged 8 through 15 use a standard vehicle seatbelt if they pass all five safety checks. If they fail even one, they must use a booster seat or child restraint. The 5 Steps for Seatbelt Fit: 1. The child's back rests flat against the vehicle seat. 2. The knees bend comfortably at the edge of the seat cushion. 3. The lap belt sits low and snug across the hips and thighs"not across the stomach. 4. The shoulder belt crosses the collarbone and chest"away from the neck and face. 5. The child can maintain this exact posture for the entire trip. Penalties: Violations of proper restraint and seatbelt laws can carry fines up to $490 plus potential DMV points.