Children under age nine or shorter than four-foot-nine must now use booster seats while in vehicles in B.C.
The new child seat laws took effect Canada Day, on Tuesday.
Booster seats reduce the risk of serious injuries and fatalities by 60 per cent, said David Dunne, director of provincial programs for the BCAA Traffic Safety Foundation
"Children without the protection of a booster seat are tremendously exposed to risk," Dunne said Monday.
"What we know right now is about 50 per cent of children in that group are using booster seats and that's just a shockingly low number."
Children over one year old and between 20 and 40 pounds need to be secured in child seats, while babies must be strapped into infant seats and face the rear of the vehicle.
Another change makes drivers responsible for ensuring any children in their vehicles are restrained properly, regardless of their relationship to the children.
Any driver caught disobeying the changes faces a $109 fine.
On average, 860 child passengers five to nine years old are seriously injured every year and five are killed, according to the latest figures from the B.C. Ministry of Public Safety.