Car Seat, Booster Seats and Seat Belts

From the time a child is born up to 4'9'' child restraints are there to protect children from serious injury or death while traveling in a vehicle.
Seat belts alone do not fit children until they are at least 4'9''.
Car seats should be rear facing for as long as the child restraint will allow the weight and height of your child. Even up to age 2 or beyond. Why? Because small children's necks are too weak to handle a crash while forward facing. What about a child's legs if they are rear facing? Most child even up to age 2 cross their legs while sitting. Even if they have their legs out straight during a crash, the likelihood of permanent damage is little. Neck injuries are far more serious and long lasting or fatal.
A child should stay in a 5 point-harness as long as possible as well. Moving a child from a 5-point harness to a booster seat should only happen when again they outgrow the 5-point harness in weight and height.
The purpose of a booster seat is to the raise the child up so that the seat belt of the car fits them properly. Low on their lap and across the boney parts of their body. Booster seats now come in many fun fabrics, styles and attachments that make them more appealing to kids. I like the high back booster so that if they fall asleep the sides help keep them in the same position not flopping forward or leaning up against the door or window.

Always keep children in the backseat.
Keep the vehicle clear of potential projectiles.
Make sure all passengers are restrained. Including pets.
Most of all take advantage of a trained Child Passenger Technician. Technicians are trained to teach parents how the Child Restraint and Vehicle work together to keep their child safe.