Car Insurance Explained: Coverage, Cost and Comparison

A car insurance policy is not one product. It is a set of separate coverages sold on a single contract, and the useful split is who each one pays. Liability pays other people for harm you cause them. Collision and comprehensive pay to repair or replace your own car. Medical payments, personal injury protection and uninsured motorist coverage pay you and your passengers. Everything below is car insurance explained coverage by coverage — what each one pays for, who requires it, and where it stops.

What does each coverage on a car policy actually pay for?

Six coverages make up a standard personal auto policy, and the Insurance Information Institute's auto insurance basics page defines each one narrowly enough to be worth quoting. Bodily injury liability "applies to injuries that the policyholder and family members listed on the policy cause to someone else." Property damage liability "pays for damage policyholders (or someone driving the car with their permission) may cause to someone else's property." Collision "pays for damage to the policyholder's car resulting from a collision with another car, object or as a result of flipping over." Comprehensive "reimburses for loss due to theft or damage caused by something other than a collision with another car or object, such as fire, falling objects, missiles, explosions, earthquakes, windstorms, hail, flood, vandalism and riots."

The distinction that matters on a claim is the payee, not the peril:

The III is explicit that "states do not require the purchase of collision or comprehensive coverage, but lenders may insist borrowers carry it until a car loan is paid off." That single sentence explains most of the confusion around the phrase drivers use for the bundle — the reason it feels compulsory is a loan agreement, not a statute. The mechanics of those two coverages, and the gaps between them, are worked through in "full coverage" isn't a real product.

What do the three numbers on a liability limit mean?

The three numbers written as 20/40/10 are two bodily injury caps and one property damage cap, in thousands of dollars. The III's compulsory auto page reads it directly: "20/40/10 means coverage up to $40,000 for all persons injured in an accident, subject to a limit of $20,000 for one individual, and $10,000 coverage for property damage."

Two ceilings apply at once. The first number caps what any single injured person can recover; the second caps the total across everyone hurt in that crash, however many people that is. A single claimant with $30,000 of medical bills recovers $20,000 under a 20/40/10 policy, not $30,000, because the per-person cap binds before the per-accident cap is anywhere near reached.

Those caps are set by legislatures, not by an actuary's estimate of what a crash costs. California's is the clearest illustration. The California Department of Insurance announced that as policies renewed through 2025, minimum liability limits rose to $30,000 per person and $60,000 per accident for bodily injury, and $15,000 for property damage — up from $15,000, $30,000 and $5,000. Now hold that against claim size. Data from ISO, a Verisk business, published in the III's auto insurance statistics, puts the average bodily injury liability claim at $22,734 in 2021. Three injured people at that 2021 average come to $68,202 — past a $60,000 per-accident cap, at a state minimum that had just been doubled. The arithmetic is illustrative, not a quote or a prediction, but the shape of it is why the anatomy of these limits is worth reading closely; what 25/50/25 means and what happens above the limit covers the part of the claim the policy stops paying.

Who requires each coverage — the state or the lender?

Two different authorities require car insurance, and they require different things. States require liability. Lenders require the coverages that protect the car itself.

Nearly every state sets minimum liability amounts. New Hampshire is the exception the III names: it "does not have a compulsory insurance liability law" and instead requires drivers to demonstrate they can provide sufficient funds after an at-fault accident.

No state requires collision or comprehensive. A lienholder does, by contract, because the vehicle is its collateral — which is why coverage that is legally optional feels mandatory to anyone with a loan, and why it can genuinely become optional again once the loan is discharged.

What happens when the at-fault driver has no insurance?

The other driver's absent policy is replaced by your own uninsured motorist coverage, if you carry it. The scale of the problem is not marginal: the III reports that "in 2022, 14.0 percent of motorists, or about one in seven drivers, were uninsured, according to a 2023 study by the Insurance Research Council (IRC)." The spread across states is wide — the District of Columbia at 25.2 percent, New Mexico at 24.9 percent and Mississippi at 22.2 percent at the top; Wyoming at 5.9 percent and Maine and Idaho at 6.2 percent at the bottom.

Uninsured motorist coverage is mandatory in only about 20 jurisdictions, per the III; elsewhere insurers must offer it but drivers may decline. So the coverage that responds to one in seven drivers is, in most of the country, the one easiest to leave off a policy without noticing. What UM, UIM and UMPD each pay, the hit-and-run rules and the stacking question are covered in uninsured motorist coverage, explained.

There is a quieter consequence. Liability limits are usually described as protection for other people, and they are. But underinsured motorist coverage is normally capped at the same limit as the liability the policy carries — so a driver who buys the state minimum has often bought a state-minimum ceiling on their own recovery too. The policy language governs this and varies by state and insurer, which is exactly the kind of question a licensed provider answers off your specific form.

How do insurers decide what to charge?

An insurer prices the expected cost of claims for a risk that looks like yours, then adds expenses. The inputs fall into three groups: the driver, the vehicle, and the place.

The vehicle side is the most measurable and the least discussed. The Highway Loss Data Institute publishes insurance losses by make and model across six coverages, and explains that "results for collision, property damage liability and comprehensive represent overall losses, which reflect both the frequency of claims and the average loss payment per claim," while the injury coverages are reported on claim frequency alone. Two cars with identical sticker prices can carry very different collision loss histories, and that history is a direct rating input.

The credit question is where received wisdom is most often wrong. The NAIC's page on credit-based insurance scores, last updated 19 March 2026, is precise about what the tool is: a score "based partly or entirely on information from a consumer's credit history" used to "estimate how likely someone is to file an insurance claim, not how likely they are to repay a loan." It is not a credit score, and it is not unregulated — the NAIC notes that insurers "cannot use these scores as the sole reason to increase rates or to deny, cancel, or refuse to renew a policy" in most states, with some states restricting or prohibiting particular uses outright.

And the rating factors themselves are not uniform across the country. California Insurance Code section 1861.02 requires auto rates to be determined by "the insured's driving safety record," "the number of miles he or she drives annually" and "the number of years of driving experience the insured has had" — in that decreasing order of importance — before any other factor the commissioner adopts by regulation. A generic list of rating factors is therefore wrong in California by statute, and state law is the first thing to check before assuming any factor applies. The fuller list, and which inputs are fixed versus changeable, is in what actually moves a car insurance rate.

Why are premiums rising if crashes are getting rarer?

Because the cost per claim rose far faster than the number of claims fell. The conventional explanation for rising premiums — more accidents — does not survive contact with the loss data.

ISO's figures published by the III, covering 2012 through 2021, show frequency and severity moving in opposite directions:

Bodily injury claims got about 18 percent rarer while the average one grew by more than half. Collision claims got rarer still, and the average payment rose 70 percent. Comprehensive is the outlier in the other direction — the only one of the three where frequency went up as well as severity.

That outlier shows up in premiums. The NAIC's 2023 Auto Insurance Database Average Premium Supplement, released 8 July 2025, reports that "comprehensive average premiums increased by 21.31% in 2023, although comprehensive written exposures only increased 0.38%" — a price increase on a coverage almost nobody bought more of. Combined average premiums rose 14.41 percent in 2023, and the national average expenditure per insured vehicle reached $1,281.60, a 19.21 percent increase since 2019.

For context on how many events those claims arise from: NHTSA's Summary of Motor Vehicle Traffic Crashes: 2023 Data (DOT HS 813 762, October 2025) counts an estimated 6,138,359 police-reported traffic crashes in 2023, in which 40,901 people were killed and an estimated 2,442,581 were injured.

What does a deductible actually change?

A deductible is the amount subtracted from a covered loss before the insurer pays, and it applies to your own car's coverages — collision and comprehensive — not to the liability coverages that pay other people. There is no deductible standing between an injured third party and your liability limit.

The arithmetic is worth doing against a real number rather than in the abstract. Take the 2021 average collision claim of $5,010 from the ISO data above. A $500 deductible leaves the insurer paying $4,510; a $1,000 deductible leaves $4,010. Raising the deductible by $500 shifts exactly $500 of that particular loss from the insurer to the policyholder, and lowers the premium by whatever the insurer's filed rate says it does — which is not a fixed ratio and varies by state, insurer and vehicle. This is an illustrative calculation on an industry average, not a quote and not a prediction about any specific claim.

Comprehensive and collision often carry different deductibles on the same policy, and some states apply separate glass provisions. Those appear on the declarations page.

One thing no deductible choice fixes: collision and comprehensive settle at the car's actual cash value, and on a financed car that figure can sit below the loan balance. The coverage built for that difference is gap insurance.

Where this explanation breaks down

Every general account of car insurance has boundaries, and these are the ones that trip people up most often.

No-fault states work differently. In a no-fault system, personal injury protection pays your own medical costs regardless of who caused the crash, and the right to sue the other driver is limited by statute. The coverage-by-payee model above still holds, but the sequence of who pays first does not.

Driving for an app is usually excluded. The California Department of Insurance's notice to transportation network company drivers states that "most standard personal auto policies contain exclusions for livery — which essentially means driving for hire," and quotes the form language: "We do not provide coverage … arising out of the ownership or operation of a vehicle while it is being used as a public or livery conveyance." Rideshare and delivery work sit in that exclusion unless an endorsement or a commercial policy fills the gap.

Rating factors are state law, not industry practice. The California statute above is the clearest case, but every state's insurance code and regulations constrain what may be used and how. A rule that is true in one state can be prohibited in the next.

Averages describe portfolios, not people. The NAIC's $1,281.60 national average expenditure for 2023 is a countrywide figure across every driver, vehicle and coverage combination. The III's state table for 2021 shows New York at $1,511.04 against North Dakota at $691.50 on a $1,061.54 countrywide average — and the spread within a state is wider still. No average predicts an individual premium.

How do you compare providers without comparing the wrong thing?

By holding the coverage constant and letting only the price vary. A premium is meaningless without the limits, deductibles and endorsements attached to it, because a cheaper number is frequently a smaller policy rather than a better price.

The comparison is like-for-like when four things match across every quote: the liability limits, the collision and comprehensive deductibles, whether uninsured and underinsured motorist coverage is included and at what limit, and any endorsements — rideshare, custom equipment, rental reimbursement, gap. Change any one of those between two quotes and the difference in price no longer measures the insurer.

Calmorg Insure is a free comparison service, not an insurer, agency or broker; we hold no insurance licences and we do not quote, sell, bind or service policies. Every quote, coverage decision and policy comes from the licensed provider you choose, and the policy form that provider issues is the only document that determines what is covered.