Older children who have outgrown booster seats should wear the vehicle's seat belts.
The manufacturer instructions that come with the booster seat state the weight and height limitations for that booster. Use a booster seat with a lap-shoulder belt until the child passes the fit test below:
Do the knees bend at the seat edge? If yes, continue. If no, return to the booster seat.
Does the shoulder belt rest on the shoulder? If yes, continue.
If no, try using the rear seat belt comfort guide, if available. If a comfort guide is not available, or if the shoulder belt still does not rest on the shoulder, then return to the booster seat.
Q: What is the proper way to wear seat belts?
A: An older child should wear a lap-shoulder belt and get the additional restraint a shoulder belt can provide. The shoulder belt should not cross the face or neck. The lap belt should fit snugly below the hips, just touching the top of the thighs.
This applies belt force to the child's pelvic bones in a crash.
It should never be worn over the abdomen, which could cause severe or even fatal internal injuries in a crash.
Also see "Rear Seat Belt Comfort Guides" under Lap-Shoulder Belt.
According to accident statistics, children are safer when properly restrained in a rear seating position.
In a crash, children who are not buckled up can strike other people who are buckled up, or can be thrown out of the vehicle. Older children need to use seat belts properly.
Warning: Never allow more than one child to wear the same seat belt. The seat belt cannot properly spread the impact forces. In a crash, they can be crushed together and seriously injured. A seat belt must be used by only one person at a time.
Warning: Never allow a child to wear the seat belt with the shoulder belt behind their back. A child can be seriously injured by not wearing the lap-shoulder belt properly. In a crash, the child would not be restrained by the shoulder belt.
The child could move too far forward increasing the chance of head and neck injury. The child might also slide under the lap belt. The belt force would then be applied right on the abdomen.
That could cause serious or fatal injuries. The shoulder belt should go over the shoulder and across the chest.