6.4 Part C Uninsured/Underinsured Motorists

Part C: Uninsured and Underinsured Motorists Coverage

Part C protects the insured when injured by an at-fault driver who has no insurance or not enough insurance. It is a first-party coverage that effectively places the negligent uninsured driver's missing liability coverage onto your own policy. Many states require insurers to offer UM/UIM and require a written rejection if the insured declines it.

There are two related coverages tested heavily:

• Uninsured Motorists (UM): the at-fault driver carries no liability insurance, or is a hit-and-run/phantom driver, or the insurer is insolvent. UM pays the bodily injury the insured is legally entitled to recover from that driver.
• Underinsured Motorists (UIM): the at-fault driver has insurance, but the limit is lower than the damages (or lower than your own UM/UIM limit). UIM fills the gap between the other driver's limit and your damages, up to your UIM limit.

UM/UIM normally covers bodily injury only. Some states add Uninsured Motorists Property Damage (UMPD) with a deductible, but the base PAP UM is BI-focused.

Underinsured Motorist Math

UIM is the single most error-prone calculation on the casualty exam. Two state approaches exist:

• Difference (excess) states: UIM pays your damages minus what the at-fault driver's liability paid, capped at your UIM limit.
• Reduction states: your UIM limit is reduced by the amount the at-fault driver paid.

Worked example (difference state). You carry $100,000 UIM per person. You suffer $120,000 in BI. The at-fault driver carries only $25,000 in liability and pays you that $25,000. Your UIM pays the gap: $120,000 - $25,000 = $95,000, which is under your $100,000 UIM limit, so UIM pays $95,000. Total recovery = $25,000 + $95,000 = $120,000.

Worked example (reduction state). Same facts, but UIM is reduced by amounts paid: $100,000 UIM - $25,000 paid = $75,000 UIM available. UIM pays the lesser of your remaining damages ($95,000) and the reduced limit ($75,000), so UIM pays $75,000. Total recovery = $25,000 + $75,000 = $100,000.

Who Is Covered and Key Rules

Like Med Pay, UM/UIM covers the named insured and family members in any auto or as pedestrians, plus other persons occupying the insured's covered auto. The insured (or a legal representative) must establish that they are legally entitled to recover — meaning the other driver must be at fault.

Frequent exam traps:

• A hit-and-run or phantom vehicle triggers UM, not UIM, because the unknown driver is treated as uninsured. Many states require physical contact for a hit-and-run UM claim.
• UIM applies only when the at-fault driver has insurance but too little — never when they have none (that is UM).
• The insured cannot stack UM and UIM for the same dollar of loss; the coverages coordinate so the insured is made whole once, not twice.
• UM/UIM limits commonly cannot exceed the insured's own Part A liability limit unless the state allows higher purchase.

Arbitration

Disputes over (a) whether the insured is legally entitled to recover and (b) the amount of damages are resolved by arbitration under the PAP, not litigation against the insurer. Either party may demand it, and most states bind both sides to the result within the policy limit.

Stacking and Anti-Stacking

Stacking is the practice of adding together the UM/UIM limits on multiple vehicles, or across multiple policies, to increase the recovery for one accident. Where state law permits intra-policy stacking, an insured with three covered autos at $50,000 UM each could stack to $150,000 for a single injury.

The PAP and many states contain anti-stacking language that limits recovery to the highest applicable single limit. Exam questions often hinge on whether the jurisdiction allows stacking and whether the insured paid a separate premium for each vehicle's UM coverage. When in doubt on a national-portion question, the default PAP position is no stacking unless the state expressly allows it.

Excess/Other-Insurance and Trigger Summary

UM/UIM contains an other insurance clause: coverage on a vehicle the insured does not own is excess over any UM/UIM on the vehicle the insured was occupying, while coverage on an owned vehicle is primary. This prevents the insured from collecting full limits twice.

Because UM/UIM only pays what the insured is legally entitled to recover, comparative-negligence reductions apply: if the insured is found 20% at fault, the UM/UIM recovery is reduced accordingly, just as a court judgment against the negligent driver would be.

Stacking, Anti-Stacking, and Reading UM vs. UIM Fast

Finish Part C with the distinctions examiners exploit. A hit-and-run or phantom vehicle triggers UM, not UIM, because the unknown driver is treated as uninsured — and many states require physical contact for the claim. UIM applies only when the at-fault driver has insurance but too little; if they have none, it is UM. The insured must be legally entitled to recover (the other driver must be at fault), and disputes over entitlement or amount go to arbitration under the PAP rather than a suit against the insurer.

Stacking adds together the UM/UIM limits on multiple insured vehicles, or across multiple policies, to raise the recoverable amount; anti-stacking policy language and many state statutes restrict it so the insured collects one limit, not the sum. Whether stacking is allowed is a state-law variable the exam may localize.

Across all of this, remember the difference-vs-reduction split governs the UIM math: difference states pay damages minus the at-fault payment up to your limit, while reduction states cut your limit by what the at-fault driver paid — the same facts can yield materially different recoveries, which is why UIM is the most error-prone casualty calculation.