40 US states require backseat seat belt use, except New Hampshire.

40 US states require backseat passengers to wear seat belts, while New Hampshire does not have a seat belt law for any seat. Federal law mandates every seat in a US-driven car to have a safety belt. Each state can decide whether to make it illegal to not wear a seat belt in the front or back seat. The Government Highway Safety Association states that 40 states require seat belt use in the backseat.