Less than one-third of the 37 models of child booster seats on the market kept a child-sized dummy from slipping out during crash tests conducted by Transport Canada this summer.

Booster seats

Seat belts are designed with a 165-pound man in mind.

With kids, the lap belt tends to ride up on the abdomen, and the shoulder belt often cuts across the face or neck. Children can be injured by seat belts that do not fit them correctly as well as by belts that are not worn correctly.

Booster seats were designed to correct this problem for most children between the ages of four and eight (or weighing up to 36 kilograms, or 80 pounds). They raise children to a height at which lap and shoulder belts can be worn correctly.

The booster seat is held in place by the seatbelt. It is not tethered to the car like a child car seat.

Children using seat belts instead of booster seats are 3.5 times more likely to suffer significant injury and four times more likely to suffer head injury.

The department tested the seats, designed for children weighing more than 40 pounds, at speeds of between 35 and 50 kilometres an hour using a dummy the size of a six-year-old.

They looked at whether the child could:

  • Get whiplash.
  • Slip under the lap belt.
  • Roll out completely.

Only 13 of the seat models received a "good" rating for keeping the dummy secure.

Transport Canada said it will use the results of the tests, which are posted on its website, to develop new regulations for the manufacture of toddler car seats.

In the meantime, Deanna Lindsay, a spokeswoman for S.E.A.T.S for Kids, a group that educates the public about child car seats, said she's glad the study is putting the spotlight on the failings of booster seats.

Unlike car seats for babies, booster seats do nothing to restrain a toddler, she said.

"All it's doing is positioning the child," Lindsay said.

Ontario Provincial Police Const. Guy Prevost said the biggest mistake parents can make is to move a child from a car seat to a booster seat when he or she is too small — i.e., weighs less than 40 pounds. A child who isn't secure during a crash can be seriously injured, he said.

"They can be thrown out in a vehicle if the vehicle rolls; they can be thrown inside the vehicle so they become a projectile," said Prevost.

Transport Canada's website provides details of the tests with each car seat, including videos. Lindsay advises parents that if they find their booster seat didn't receive an acceptable rating, they should buy a new one.