DENVER -- Colorado kids will have to ride in booster seats two years longer under a new law that starts Sunday.

Senate Bill 110 requires all children younger than eight to use a car seat or a booster seat. Under the old law, children were only required to ride in a booster seat until age six.

In the bill, state senators said that, "Most children outgrow conventional car seats when they are about 3 to 4 years of age; however, they are still not tall enough to fit properly in a vehicle belt, so they are likely to put the shoulder belt under the arm or behind the back to prevent it from rubbing against the neck. They also tend to slouch or slide forward, causing the lap belt to ride up on the abdomen. This improper belt use can result in severe injuries or even ejection from the vehicle."

The new law starting Aug. 1, requires a child younger than one year of age and weighing less than 20 pounds be properly restrained in a rear-facing child restraint system in the rear seat of the vehicle.

Children ages 1 to 4 who weigh less than 40 pounds, but at least 20 pounds, should be properly restrained in a rear-facing or forward-facing child restraint system.

Children 4 to 8 years old must continue to ride in a child restraint seat. That can be a five-point harness child safety seat for younger children or a booster that uses the vehicle's lap and shoulder belt as kids get older and bigger.

Denver's Children's Hospital said the safest practice is to keep children in a booster in the back seat until they are 57 inches tall and at least 8 years old.

Read a summary flier of the law here.

Parents will not be ticketed immediately. The bill calls for a one-year period where drivers will be given a warning and not a citation.

Learn more about the new rules and best safety practices on the Children's Hospital website. To find a fitting station, go to the Colorado Child Passenger Safety website and enter your zip code.