The state of California requires that you get automobile liability insurance for all of the drivers in your household.
If someone in your home gets in an accident and they don't have car insurance, your insurance company will turn down their claim.
California requires that every driver have a minimum level of insurance.
The requirements are called 15/30/5.
That means that the insurance company will pay $15,000 if there is one injury, $30,000 if there are 2 or more and $5,000 in property damage including damage to the other vehicle.
Note that liability only insurance covers damage done to someone else and does not replace your own car.
If you don't carry liability insurance, the California Department of Motor Vehicles will suspend your license for up to a year.
If you don't pay the damages you are liable for, they can suspend the license until you do.
If you do not have liability insurance, you are personally responsible for all damage done.
If someone in your household has their own car and car insurance, you don't have to put them on your insurance if they drive your car occasionally.
But if they cause an accident in your car, their own insurance will have to pay the damages.
Additional driver insurance covers only your car or cars.
The covered person has no protection when they drive other people's cars.
When you add an additional person to your coverage, it will increase the cost of your policy.
The amount of the increase will depend on how old the driver is, their driving record, and sometimes even their credit score.
Adding a teenaged driver will make the family's insurance premiums skyrocket, much to many parent's dismay.
However, if the student has good grades, it helps.
If an additional driver has tickets or an accident, it will increase the policy rates as well.
Finally, insurance companies are increasingly looking at credit scores as their actuaries have found a correlation between bad credit and high risk driving.
If you live in a house with other drivers, make sure they are covered by your insurance or their own.
If not, lending your car to them for a grocery run could turn out to be an expensive proposition.