Over 16% of California motorists operate vehicles with zero auto insurance, and millions more carry only state-minimum $15,000 liability coverage. When hit by an uninsured or underinsured driver, your own **Uninsured/Underinsured Motorist (UM/UIM)** policy coverage becomes your lifeline for financial recovery.
1. UM vs UIM Claim Trigger Mechanics
| Coverage Type | Trigger Condition | Dispute Resolution Forum |
|---|---|---|
| Uninsured Motorist (UM) | At-fault driver has $0 insurance or fled (Hit-and-Run). | Binding contractual arbitration with your insurer. |
| Underinsured Motorist (UIM) | At-fault policy limits exhausted and damages exceed limits. | Settlement of underlying policy + UIM arbitration for excess. |