We will pay compensatory damages which an "insured" is legally entitled to recover from the owner or operator of an "uninsured motor vehicle" because of "bodily injury":

Sustained by an "insured"; and
Caused by an accident.

The owner’s or operator’s liability for these damages must arise out of the ownership, maintenance or use of the "uninsured motor vehicle".

A key element of the uninsured motorists coverage insuring agreement is that the operator or owner of the uninsured motor vehicle must be legally responsible to pay for the insured’s damages. The insurance company has no obligation to pay for an insured’s injuries unless the elements of legal liability are present. That is one of the reasons uninsured motorists coverage has been described as reverse liability insurance. Think of uninsured motorists insurance in this way: the insurance company becomes, in a sense, the liability insurer of any uninsured motorist that injures its insured.

"Underinsured motor vehicle" is defined as "a land motor vehicle or trailer of any type to which a bodily injury liability bond or policy applies at the time of the accident buts its limit for bodily injury liability is less than the limit of liability for this coverage." This, in effect, allows an insured to recover, up to the limit of liability scheduled for underinsured motorists coverage, the difference between his or her actual damages for bodily injury and the amount of the liability insurance carried by the at-fault driver.

Even if a named insured chooses to buy uninsured motorists insurance, a possible gap in coverage can arise. For example, suppose that A is an insured under a personal auto policy with an uninsured motorist limit of $100,000 and A is injured by a negligent driver, B, whose $ 15,000/30,000 bodily injury limits satisfy the applicable state financial responsibility law. A’s policy, therefore, does not consider B’s car as an uninsured motor vehicle. Even if A’s expenses exceed B’s liability limits, A may not collect uninsured motorists insurance. To remedy this potential area of disappointment, the underinsured motorists coverage endorsement, may be attached to the personal auto policy.