Uninsured and underinsured motorist coverage is a type of optional insurance that compensates for damages caused by another driver who either does not have car insurance or whose policy does not cover the damages. Although insurance firms must provide these plans, it is not a requirement to acquire uninsured motorist coverage. Even if a motorist has insurance, the liability limitations in a major rear-end collision may not be adequate to pay the losses. If another driver suffers injuries in a major accident, he or she may use his or her uninsured motorist insurance to compensate for losses that do not receive coverage from the other driver's policy.