The Risk That Other Drivers Bring to the Road
When you're involved in an accident caused by another driver, the natural assumption is that their auto insurance will cover your losses. That assumption holds — but only when the at-fault driver actually carries adequate coverage. The reality is more complicated.
According to estimates from the Insurance Research Council, approximately one in eight drivers on U.S. roads is uninsured. Many more carry only state-minimum liability limits, which can be as low as $15,000 per person in some states — far short of what a serious injury actually costs. If you're hit by one of these drivers, you may find yourself facing medical bills, lost income, and vehicle repairs with no reliable source of compensation.
This is the gap that uninsured motorist (UM) and underinsured motorist (UIM) coverage is designed to close. Understanding how these coverages work is part of making informed decisions about your auto policy. See our overview of auto insurance coverage types for broader context on how different policy components fit together.
~1 in 8
U.S. drivers estimated to be uninsured
Based on Insurance Research Council estimates, approximately 12–13% of motorists on U.S. roads carry no auto insurance.
$15,000
Lowest per-person liability minimum among some U.S. states
Several states set bodily injury liability minimums as low as $15,000 per person — a limit that can be exhausted quickly by even moderate injury costs.
~20 states
States that mandate UM/UIM coverage
Roughly half of U.S. states require drivers to carry some form of uninsured or underinsured motorist coverage, while others make it optional.
How UM and UIM Coverage Actually Work
Uninsured motorist (UM) coverage responds when the driver who caused your accident carries no liability insurance at all. It can pay for your medical expenses, rehabilitation costs, lost wages, and in many states, pain and suffering. Some policies also include an uninsured motorist property damage (UMPD) component that helps cover vehicle repairs, though this varies by state and insurer.
Underinsured motorist (UIM) coverage applies when the at-fault driver has insurance, but their policy limits are too low to cover your total losses. For example, if your medical bills total $80,000 and the at-fault driver's liability limit is $25,000, your UIM coverage can potentially pay the remaining $55,000 — up to your own UIM policy limit.
Both coverages typically apply to you, passengers in your vehicle, and in many cases, family members in your household. They may also extend to injuries you sustain as a pedestrian or bicyclist hit by an uninsured driver, depending on your policy's language.
It's worth noting that UM and UIM are separate coverage components, and not every policy automatically bundles them together. Always review your declarations page to confirm what your policy includes.
Review Your Declarations Page Carefully
Your auto insurance declarations page lists each coverage type and its limits. Look specifically for 'UM/UIM BI' (bodily injury) and 'UMPD' (property damage) line items to confirm what you actually carry. If you don't see them — or if the limits seem low — it's worth a conversation with your agent before you need to file a claim.
State Requirements and Common Misconceptions
Whether you're required to carry UM/UIM coverage depends entirely on where you live. Some states mandate it as part of every auto policy. Others require insurers to offer it while permitting policyholders to waive it in writing. A smaller number of states have no UM/UIM requirement at all. Because rules differ so significantly, checking your state's insurance department website or speaking with a licensed agent is the most reliable path to understanding your obligations.
A common misconception is that liability coverage — the type that pays for other people's damages when you're at fault — provides you with protection in reverse. It does not. Liability coverage protects the other party; it offers you no coverage if you're the one who's injured. This is a distinction that trips up many drivers. For a fuller picture of how these coverage types differ, see our article on liability, collision, and comprehensive coverage.
Another frequent assumption is that health insurance makes UM/UIM redundant. Health coverage may address some medical costs, but it generally does not compensate for lost income, pain and suffering, or vehicle damage — all areas where UM/UIM coverage can apply.
Stacking: A State-Dependent Option
Some states allow 'stacking' of UM/UIM coverage, which means policyholders can multiply their coverage limits across multiple vehicles on the same policy. For example, if you have two vehicles each with $50,000 in UIM coverage, stacking could allow up to $100,000 in available UIM benefits. Stacking rules vary significantly by state and insurer, so verify whether this option is available and how it works under your specific policy.
Making an Informed Decision About Your Coverage
Adding or increasing UM/UIM limits is generally one of the more straightforward ways to strengthen an auto policy. Premiums for this coverage are typically modest relative to the financial exposure it addresses, though actual costs depend on your insurer, location, driving record, and coverage limits chosen.
A common approach is to align your UM/UIM limits with your liability limits, creating a consistent level of protection on both sides of an accident. However, the right decision depends on your personal circumstances — including your existing health coverage, financial reserves, and risk tolerance. These are conversations best had with a licensed insurance agent who can review your full policy picture.
Drivers who carry only state-minimum coverage may be particularly exposed. If you're weighing the trade-offs between minimum and broader coverage, our article on minimum vs. full coverage explains those differences in practical terms. And for a broader look at where policy gaps tend to appear, coverage gaps that catch drivers off guard after an accident is a useful companion read.
This article is for general informational purposes only and does not constitute personalized insurance, legal, or financial advice. Coverage terms, availability, and requirements vary by state and insurer. Consult a licensed insurance agent and review your policy documents before making coverage decisions.
Frequently Asked Questions
No. Requirements vary by state. Some states mandate UM/UIM coverage, others require insurers to offer it but allow drivers to waive it in writing, and a handful have no such requirement. Check your state's insurance department for the rules that apply to you.
In most states, uninsured motorist coverage does extend to hit-and-run accidents because the fleeing driver is treated as an uninsured motorist. However, some states require physical contact with the other vehicle to qualify. Review your specific policy language and state rules.
It depends. Uninsured motorist property damage (UMPD) is a separate component from bodily injury UM coverage and is not universally available or required. In some states, collision coverage may be the primary way to repair your vehicle after an uninsured-driver accident.
A common guideline is to match your UM/UIM limits to your existing liability limits, ensuring consistent protection. However, the right amount depends on your personal financial situation, assets, and health coverage. Consulting a licensed insurance agent is the best way to assess your needs.
Generally, UIM coverage pays only the difference between the at-fault driver's liability payout and your actual covered losses — up to your UIM policy limit. You typically cannot collect more than your total covered damages combined from both sources.
Not entirely. Health insurance may cover medical bills, but it generally does not compensate for lost wages, pain and suffering, or vehicle damage. UM/UIM coverage fills those gaps that a health plan would not address.
The content on this site is for informational purposes only and is not a substitute for professional advice. Always consult a qualified professional for guidance specific to your situation.