Most six- and 7-year-olds will have to wait a little longer to chuck their booster seats under a new California law that went into effect Jan. 1 and is designed to make vehicle travel safer for kids.

The new law, sponsored by Sen. Noreen Evans, D-Santa Rosa, requires children to remain in booster seats until they are 8 years old or are 4 feet 9 inches tall.

Before, children could legally avoid booster seats when they turned 6 or reached 60 pounds. The new law does away with the weight requirement.

"Seat belts are not designed for small children. That's why we need booster seats to make sure they are safe in cars," Evans said Friday.

Vehicle collisions are the leading cause of death and traumatic brain injury for children ages 4 to 8.

According to data from the state Department of Public Health, 113 children ages 6 and 7 died in motor vehicle crashes from 2000 to 2009 in California. An additional 414 suffered serious brain injuries.

Child safety advocates say booster seats have been shown to decrease the risk of injury and death by 60 percent.

"I think it's great. It's a chance to keep kids safer a little longer," said Molly Caselli of Sonoma.

Inspired by the new law, Caselli said she bought a nicer car seat for her 5-year-old son, Richie Cross.

Once he outgrows that, Caselli will have to get him a booster seat. A booster seat differs from a child safety seat in that it adjusts only the height of the child so that the seat belt fits properly.

The lap belt portion of seat belts often ride up too high on a child's stomach and the shoulder strap often is too near a child's neck or face. Booster seats help correct those problems by lifting a child higher so that the belt straps align with bones that can better withstand the force of a collision, such as the pelvis and clavicle.

"Booster seats do not need to be secured with a seat belt or other clip," CHP Officer Jon Sloat said.

More than 30 states have enhanced booster seat requirements, and Wyoming and Tennessee require children up to age 9 to use the seats.

Sloat said the new law simply enforces the recommendation made by transportation authorities that children remain in booster seats until they reach 4 feet 9 inches tall.

If a child turns 8 and still has not reached that height, the CHP recommends that they continue to use a booster for safety reasons, although that's not required under the new law.

Casey Wroblewski of Sonoma said he has "mixed feelings" about the new law. He said he supports the goal of improving safety. But he said it will be a challenge getting his boys, now 3 and 2, to use the seats.

"It depends on what kid you have that day," he said, referencing a child's ever-changing moods.

He also expressed concerns about cost, saying he has six car seats installed in the three vehicles he uses to haul his boys around town.

Safety advocates counter that many parents have car seats that convert into boosters, in which case there is no additional cost. New booster seats start at around $15, and there are programs that offer free or low-cost seats to parents who qualify.

"My kids always complained about being in booster seats and car seats," Evans said. "But we don't let kids call their own shots when it comes to safety."

But getting a booster seat is only half the battle.

Sloat said about 75 percent of car seats inspected by the agency are not installed correctly. He said parents can have theirs checked at the CHP's Rohnert Park office.

You can reach Staff Writer Derek Moore at 521-5336 or derek.moore@pressdemocrat.com.