What does uninsured motorist and under insured motorist insurance cover?

Uninsured motorist coverage pays damages for bodily injuries when the at-fault driver or owner of a vehicle has no bodily injury liability coverage. It pays an amount up to the amount purchased by the insured, and is generally not a required coverage. In those states that utilize a comparative negligence rule of determining fault for a collision, the amount that the inured party can recover is reduced by the amount of liability attributable to him/her. In that respect, it operates similarly to the evaluation of the injury and damages if the at-fault party did have bodily injury liability coverage.

Underinsured motorist coverage serves essentially the same purpose. However, it is triggered when the at-fault party's bodily injury liability coverage is less than the injured party's uninsured motorist coverage. Further, in order to be triggered, the "value" of the injury must exceed the liability coverage of the at-fault party.