Each policy is based on a vehicle/driver pairing. The policy covers the named primary driver and any named secondary household drivers for the vehicle specified in the policy application. For instance, if you purchased a MileMeter policy to cover yourself and your spouse for the vehicle with the license plate “MYCAR1”, then your policy fully covers you both only when driving “MYCAR1.” If you and your spouse want to drive another car other than “MYCAR1”, then you should purchase another policy for the additional vehicle.
If your MileMeter policy has one named driver — you — you should not give someone else in your household (e.g. your 18-year old daughter) permission to drive that vehicle. If this is your primary vehicle but you want to let someone else that lives in your household (e.g. your 18-year old daughter) drive that vehicle, you should add that person as a secondary driver to your policy.
If your tendency is to worry about coverage limits, the safe thing is to make sure all household drivers are named in your policy by listing them as drivers. If you have an 18-year old daughter, well, there’s only so much we can do to help! To minimize the cost of insuring an expensive driver like an 18-year old, we suggest insuring them on their own vehicle (your hand-me-down car) with just a few thousand miles per year. In this manner the cost can be contained by limiting driving, and the other vehicles and drivers in the household will not be paying for the 18-year old on the other policies. Again, if they are not listed on a household vehicle’s policy, they will not be covered when driving this vehicle.