6.4 Part C Uninsured/Underinsured Motorists

The UM/UIM Insuring Agreement

Part C – Uninsured Motorists Coverage (UM) pays compensatory damages an insured is legally entitled to recover from the owner or operator of an uninsured motor vehicle because of bodily injury sustained in an auto accident. Two phrases matter: the at-fault driver must be uninsured (or underinsured) and the insured must be legally entitled to recover — meaning the other driver must have been at fault. UM does not pay when the insured is the negligent party.

UM is first-party coverage that stands in for the missing liability insurance of the at-fault driver. In most states UM covers bodily injury only; some states add Uninsured Motorist Property Damage (UMPD). Many states require insurers to offer UM/UIM and require a written rejection to decline it.

What Counts as an Uninsured vs. Underinsured Vehicle

An uninsured motor vehicle under Part C includes a vehicle:

1. With no bodily injury liability bond or policy at the time of the accident;
2. Whose insurer denies coverage or becomes insolvent;
3. That is a hit-and-run vehicle whose driver/owner cannot be identified and which strikes the insured or a covered auto.

An underinsured motor vehicle (UIM) is one that is insured, but with liability limits lower than the insured's UIM limit (or, in some states, lower than the insured's actual damages). UIM fills the gap between the at-fault driver's inadequate liability limit and the insured's own UIM limit.

Trap: A vehicle is NOT 'uninsured' merely because the limits are low — that is the realm of UIM. And a vehicle owned by or furnished for the regular use of the insured, or a government-owned vehicle, is specifically excluded from the 'uninsured vehicle' definition.

Two Approaches to UIM: Difference-in-Limits vs. Excess

States apply UIM two ways, and the exam tests both.

Difference-in-limits (reduction / offset) approach — the more common: UIM pays the insured's UIM limit minus the amount actually recovered from the at-fault driver's liability policy.

Worked example (difference-in-limits). Insured carries $100,000 UIM. The at-fault driver carries only $25,000 liability. The insured's total damages are $90,000.

• At-fault liability pays: $25,000
• UIM available = $100,000 limit − $25,000 received = $75,000, but capped at remaining damages of $90,000 − $25,000 = $65,000
• UIM pays $65,000; insured is made whole at $90,000 total.

Excess approach — UIM stacks on top of the liability recovery up to the UIM limit. Same facts under an excess state: insured gets $25,000 liability + up to $100,000 UIM = up to $125,000 available, paying the remaining $65,000 of damages. Either way the insured here recovers $90,000, but with larger damages the two methods diverge.

Limits, Stacking, and Arbitration

UM/UIM uses the same split-limit or CSL format as liability (e.g., 100/300). The UM limit is the most the insurer pays for all damages from one accident regardless of the number of insureds, claims, vehicles, or premiums shown.

Stacking lets an insured combine limits across multiple covered autos or policies. Intra-policy stacking combines limits on several autos on one policy; inter-policy stacking combines limits across separate policies. Some states permit stacking; ISO language and many states prohibit it via an anti-stacking clause.

Disputes over (a) whether the insured is legally entitled to recover and (b) the amount of damages are typically resolved by arbitration under Part C, not litigation. The PAP also requires the insured to notify the insurer of a tentative settlement with the at-fault party so the insurer can protect its subrogation rights — settling and releasing the tortfeasor without consent can void UIM coverage.

Stacking and the Hit-and-Run Rule

Stacking lets an insured combine UM/UIM limits across multiple vehicles or policies. Intra-policy stacking adds limits for each insured vehicle on one policy; inter-policy stacking combines separate policies. Many states (including Pennsylvania) let the insured elect or reject stacking in writing, with rejection lowering premium.

Uninsured motorist (UM) also responds to a hit-and-run (phantom vehicle) where the at-fault driver cannot be identified — most states require physical contact or independent corroboration for a phantom-vehicle UM claim.

Trap: UIM applies only when the at-fault driver's liability limit is lower than the insured's UIM limit; the insured recovers the difference (in difference-in-limits states), not the full UIM limit on top of what the at-fault carrier paid.

UM/UIM Election, Rejection, and Property-Damage UM

UM/UIM is mandatory or must be offered in most states; insureds may reject or reduce it only in writing. Some states also offer Uninsured Motorist Property Damage (UMPD), paying for damage to the insured's vehicle caused by an uninsured at-fault driver (useful when the insured carries no collision coverage), often subject to a deductible.

Disputes over UM/UIM fault and damages are commonly resolved by arbitration under the policy. Coverage applies to the named insured, family members, and occupants of the covered auto injured by an uninsured/underinsured driver.

Exam tip: rejecting or reducing UM/UIM must be done in writing; an oral waiver is ineffective and the insurer is generally deemed to provide the coverage at the state-required level. UMPD overlaps with collision, so an insured with collision often declines UMPD.