Mississippi vs Tennessee

Tennessee and Mississippi meet at one of the busiest metro borders in the South, just south of Memphis, and their laws diverge sharply. Tennessee writes out a full age-based ladder: rear-facing under 1, a forward-facing harness from 1 to 3, a booster from 4 to 8, the seat belt only at age 9 or 4 feet 9 inches, and the back seat through the booster stage. Mississippi sets no rear-facing age, ends the booster at age 7, and has no back-seat rule. Tennessee is stricter at every stage, from the first rear-facing requirement Mississippi lacks to a booster that runs two years longer with a back-seat mandate behind it.

Tennessee requires a child under 1, or 20 pounds or less, to ride rear-facing in the rear seat, and it requires the rear-facing, forward-facing, and booster stages to be used in the back seat where one is available. Mississippi sets no rear-facing age and no back-seat rule. So a Tennessee parent can be cited for turning an infant forward or seating a young child up front, while a Mississippi parent cannot. Pediatricians recommend both rear-facing and the back seat far longer than either law requires, but only Tennessee makes them legal requirements.

Tennessee keeps a child in a booster until age 9, or until they reach 4 feet 9 inches. Mississippi ends the booster at age 7, or once a child is both 4 feet 9 inches and 65 pounds. So a 7 or 8 year old who could move to the seat belt in Mississippi still rides in a booster, in the back, in Tennessee. Tennessee also carries a clear $50 fine with no added court costs, while Mississippi sets its requirement in one section and its fine in another. Tennessee's two extra booster years bring it closer to the American Academy of Pediatrics guidance that a booster should last until the seat belt actually fits.

The law that applies is the law of the state you are physically driving in, which matters a great deal here because the Memphis metro spills across the line into DeSoto County, Mississippi. Tens of thousands of families commute between Southaven, Olive Branch, and Memphis along I-55 and I-22 every day. To stay legal across the whole trip, follow Tennessee's stricter rules: rear-face under 1, keep a child in a booster until age 9 or 4 feet 9 inches, and seat them in the back. A family moving from Mississippi to Tennessee should expect the booster to run two years longer and the back seat to become a requirement.