Does anybody know how old a child has to be before I can take her out of her booster car seat?

It is one thing for an adult to be in an auto accident and it is another thing altogether if a child or infant is in one. A car accident or car crash is bad enough, but children are often the most severely injured of any passengers involved.
There are thousands of deaths of children who are victims of a car crash and many more are seriously injured. There are precautions that you should take before taking any child or infant for a ride in your vehicle.
Make sure you do your research of the various types and makes of baby and infant car seats before you make your selection. Look into Graco, Recaro, Chicco and other manufacturers of car seats and find the one that is best for you and for your child.
An infant car seat must always be rear-facing and never face forward. When a baby is in a rear facing car seat, she will be pushed into the shell of the car seat, which cradles her and supports her whole body. The neck and head (which is relatively big for a baby) are cradled by the car seat and the baby has a very high chance of surviving the car crash. It is crucial that the head and neck of the baby must be supported in this way if involved in a crash.
You should also research into the specific guidelines for your state as far as car seat requirements are concerned as they will usually vary, from state to state.
Some parents choose to keep a rear facing seat longer than is required by law but there is no drawback to this. For example, Graco rear facing baby car seats are available in larger sizes to accommodate a baby that is up to 60 lbs.
Most car seats are easy to install and some cities and towns have as a public service, a program where you can bring your carseat to the local police station where an officer will install it for you.
Certain models will easily be portable and turn into a stroller once you remove it from the car, such as the Safety 1st Infant Auto Seat. This is like buying two products in one and the safety of the car seat is coupled with the convenience of a quickly convertible stroller.