Uninsured motorist coverage protects you if you are injured by the negligence of a driver with no liability insurance. In Pennsylvania, one out of every ten licensed drivers does not have liability insurance! That's why you should double check your automobile insurance policy, or policies, to make sure that you are protected against drivers with no insurance coverage.
Because Uninsured Motorist coverage (UM) is optional, you may think that you are "fully covered", but you may not be! Review the declaration page of your insurance policy, which is usually the first page of your policy and lists all of the coverages and their costs. You should have UM coverage, and it should be equal to your liability limits. In other words, if you have $100,000 per person/$300,000 per accident in bodily injury liability coverage, which protects you if you are negligent and injure someone, then your UM coverage should also be $100,000 per person/$300,000 per accident. If you don't have UM coverage equal to your bodily injury liability limits, then you are protecting someone who you may injure more than you are protecting yourself.
If you have more than one vehicle on your policy, you should also have stacked UM coverage. Stacked coverage allows you to add or "stack" the number of vehicles you insure on your policy by the amount of coverage you have. For example, if you have three vehicles insured under the same policy, with UM coverage of $100,000 per person/$300,000 per accident, you add all three vehicles to get $300,000 per person/$900,000 per accident, but only if you have stacked coverage. As with UM coverage, stacked coverage is optional, so double check your policy if you have more than one vehicle to make sure you have stacked UM coverage equal to your bodily injury liability limits.