South Dakota Booster Seat Laws: Age, Weight, and Penalties

South Dakota booster seat laws don’t actually exist as a separate rule: state statute never uses the term “booster seat.” Instead, two statutes cover child passengers. Children under five must ride in a child passenger restraint system, and children ages five through seventeen must wear a seat belt. A booster is one legal way to meet either standard, but the state does not specifically require one at any age.

What South Dakota Law Actually Requires

Under SDCL 32-37-1, a driver carrying a child younger than five on any South Dakota street or highway must secure the child in a restraint system installed and used according to the manufacturer’s instructions, and the seat must meet federal Motor Vehicle Safety Standard 213.¹

One carve-out matters for parents thinking about boosters. If a child under five weighs at least 40 pounds, a regular seat belt satisfies the statute.¹ Most children reach 40 pounds somewhere between ages three and five.

Once a child turns five, SDCL 32-37-1.1 takes over. The driver has to make sure every passenger from age five through seventeen is wearing a properly adjusted and fastened seat belt while the vehicle is moving.² No booster is required for this age group. A buckled seat belt meets the legal standard, even for a small five-year-old.

The driver is the person legally on the hook, whether or not the child is theirs.

The Gap Between the Law and Safety Guidance

This is where South Dakota parents need to pay attention. A typical five-, six-, or seven-year-old is far too small for an adult seat belt to fit correctly. Safety organizations recommend keeping children in a booster until they’re roughly 4 feet 9 inches tall, which most kids don’t reach until somewhere between ages eight and twelve. Buckling a small child directly into a seat belt is legal here, but the lap belt often rides up onto the abdomen and the shoulder belt crosses the neck instead of the chest.

So the practical answer for most families: your child is probably ready to leave a child safety seat around the time the law lets them switch to a seat belt, but ready to leave a booster much later than the law suggests. The state sets a floor, not a ceiling.

When a Child Is Actually Ready to Stop Using a Booster

A booster lifts the child so the vehicle’s lap and shoulder belt sit where they’re supposed to. The widely used five-step seat belt fit test tells you when the booster can come out:

The child sits all the way back against the vehicle seat.
Their knees bend comfortably at the edge of the seat.
Their feet rest flat on the floor.
The lap belt lies low across the hips and upper thighs, not across the stomach.
The shoulder belt crosses the collarbone and chest, not the neck or face.

The child also needs to be able to sit this way for the whole ride, without slouching or sliding the shoulder belt behind their back. Fail any step and the booster stays. Seat shape varies between vehicles, so a child who passes in one car may not pass in another.

NHTSA’s Four Stages

Because South Dakota’s statute defers to manufacturer instructions and leaves the rest to parents, federal guidance from the National Highway Traffic Safety Administration is what fills in the specifics. NHTSA recommends four stages:³

Rear-facing seat from birth through at least age one, and ideally until the child reaches the seat’s maximum height or weight (often age three or beyond).
Forward-facing seat with an internal harness and top tether after outgrowing rear-facing, typically through about age seven depending on the seat.
Booster seat once the child outgrows the harness seat, continuing until they pass the seat belt fit test.
Seat belt alone once the belt fits properly, usually between ages eight and twelve.

NHTSA also recommends keeping children in the back seat through at least age 12.³ The South Dakota Department of Social Services makes the same recommendation.⁴ Neither is written into state law.

What South Dakota Does Not Require

A few rules parents often expect to find in a booster or child seat law are missing from South Dakota’s statute:

No rear-facing age or weight requirement. The statute points to manufacturer instructions and stops there.
No booster seat mandate at any age.
No requirement that children ride in the back seat.
No medical or size exemption that would excuse an older child from the seat belt rule.

Penalties

Violating either the under-five restraint rule or the five-through-seventeen seat belt rule is a petty offense carrying a $25 fine, with no court costs added.¹²⁵ South Dakota’s adult seat belt law is a secondary offense, but the child restraint chapter contains no such limitation. An officer can pull you over solely because they see an unrestrained child in the car. There is no ticket-dismissal program for buying a seat after the fact.

Rideshares and Taxis

The child restraint statute applies to any operator of a passenger vehicle on a public road and does not carve out taxis or rideshare drivers.¹ If you’re taking an Uber or Lyft with a child under five who weighs less than 40 pounds, that child legally needs to be in a restraint system. Rideshare drivers in South Dakota are not required to supply one, and Lyft’s car seat mode isn’t available in the state, so bringing your own is the only practical option.

1
South Dakota Legislature. South Dakota Codified Law 32-37-1 – Use of System Required–Violation as Petty Offense
2
South Dakota Legislature. South Dakota Codified Law 32-37-1.1 – Operator to Assure That Passengers Between Ages Five and Eighteen Wear Seat Belts
3
NHTSA. Car Seat Recommendations for Children by Age and Size
4
South Dakota Department of Social Services. Child Safety Seat Distribution Program
5
South Dakota Unified Judicial System. FY26 Fine and Bond Schedule for Use by Clerk Magistrates