A new law that makes booster seats in vehicles mandatory for small children came into effect in New Brunswick on Thursday.

Under the law, which was passed in December, children younger than nine must be strapped into a booster seat with a seatbelt until they weigh 80 pounds and four feet nine inches.

Parents who don't comply with the law will be fined $172.50 for each violation.

Safety experts say it's about time the province introduced such a law.

"Kids in a regular seatbelt sustain pretty severe and serious injuries to their abdomen[s] and spinal cord[s] because the seatbelt doesn't fit them properly in a crash. And so booster seat raise the body of a child so that a seatbelt fits them properly," said Jennifer Brittain with the Atlantic Health Sciences Corporation.

But it will take time for some New Brunswickers to adjust to the new law. Sylvie Lang, who works at the Between Friends daycare in Dieppe, said the daycare has asked the province for a grace period to meet the new requirements.

"We're really in a mess," she said, explaining that she had 75 children to drive around and almost half of them now require booster seats.

The change is also costly. "Just for eight [seats], $1,000, it cost us yesterday, and we need more," she said.

New Brunswick is the fifth province to make booster seats mandatory. Ontario, Quebec, Nova Scotia and, most recently, British Columbia have all rewritten their booster seat regulations.