After a truck crash in Illinois, the question that decides a claim is often not who was at fault, but how much of the fault belongs to each party.

Illinois divides responsibility by percentage, and two numbers in the law change the result sharply: a claimant found more than 50% at fault recovers nothing, and a defendant at 25% or more of the fault can be pursued for more than its own share.

For a fleet, that turns a disputed crash into an argument over a few points, and the result depends on what each side can show.

How Illinois Divides Fault

Illinois follows a rule known as modified comparative fault. When a crash leads to a negligence claim for injury, death or damage to property, the person bringing the claim can still recover even if they were partly to blame, but their damages are reduced by their own share of fault. A claimant found 20% responsible recovers 80% of their damages.

The limit comes at the halfway point. If the claimant’s fault is more than 50% of the cause, they recover nothing at all. At exactly 50%, they still recover half. The rule is often called the “51% rule,” but the test in the statute is whether the claimant’s share is more than 50%.

Two details matter for trucking. The rule covers damage to property as well as injuries, so it applies when a carrier claims for damage to its own truck, not only when someone claims against the carrier. And the percentages are set by whoever decides the facts, usually a jury if a case goes to trial, based on the evidence each side puts forward.

The 25% Line When Several Parties Share Blame

Many truck crashes involve more than two parties: a car that cut in, a second truck, a work zone that narrowed a lane. When several defendants share the blame, a second Illinois rule decides how much each one can be made to pay.

For the injured person’s medical expenses, every defendant found liable can be held responsible for the full amount, whatever its share. For all other damages, such as lost income or pain and suffering, the line sits at 25%. A defendant found less than 25% at fault generally pays only its own share of those damages. A defendant at 25% or more can be pursued for all of them, even if the other defendants cannot pay their part.

Take a crash that injures a driver who bears no blame, where another car driver is found 60% at fault, a trucking company 30% and a third motorist 10%. The trucking company sits above the line and can be pursued for the full amount of the non-medical damages. Had the evidence placed it at 20%, it would generally owe only its own share. Because a trucking company is often the best-insured party in a crash, claimants have every reason to argue its share above 25%.

Fault also decides how a claim against a carrier’s policy is resolved. The way fault apportionment plays into a policy is set out in this explainer on Illinois trucking insurance.

Why a Few Points of Fault Matter

Because both rules work as thresholds, small changes in the fault split can produce large changes in the result.

When a carrier is defending a claim, the difference between 24% and 26% can decide whether it answers for its own share of non-medical damages or for all of them. When the carrier is the one claiming, for example for damage to its truck after another driver pulled across its lane, the difference between 50% and 51% decides whether it recovers half its loss or nothing. The same split generally governs what the carrier’s insurer can recover from the other driver’s insurer after paying for the repair.

The arguments that move these numbers are usually narrow: whether a lane change was signaled, how closely the truck was following, how fast traffic was moving, who entered the intersection first.

Most Claims Settle on Estimated Fault

Most crash claims never reach a jury. They are settled between insurers, adjusters and lawyers, and those negotiations generally work from an estimate of how a jury would split the fault. The thresholds shape the conversation long before any trial date. A claimant close to the 50% mark has a strong reason to settle, and a defendant with a sound case that it sits below 25% has a reason to hold its position.

That makes timing important. A clear account of the crash, available in the first days, tends to narrow the range of fault each side can credibly argue. When the record is thin, the estimate rests on statements and assumptions, and a fleet with no record of its own has little to push back with.

What Evidence Changes an Outcome

In a fault dispute, the most persuasive evidence is usually a record made at the moment of the crash rather than an account given afterward. Forward-facing camera footage can show a car cutting in, a signal that came on late or a light that changed. Telematics records can show speed and braking in the seconds before impact, where the system captures them. Records like these answer the narrow questions that move a fault split.

Whether that evidence exists is decided long before any crash, by company policy. Choices about camera placement, how long footage is kept, who can retrieve and export it, and whether the carrier or the vendor holds the data all determine what can be produced when a claim is disputed. So does a standing rule to preserve footage after every incident, including minor ones, since a scrape that looks trivial on the day can become a disputed claim months later. Applying those settings consistently across every truck matters too, so that no unit is running on different rules from the rest.

The Split Is the Claim

Illinois does not ask only whether a party was at fault. It asks how much. A claimant past 50% recovers nothing, and a defendant at 25% or more can be pursued well beyond its own share, so the outcome of a disputed truck crash often comes down to a handful of percentage points. Those points are argued with evidence, and the evidence a fleet can produce is fixed by decisions made before the crash: what its cameras record, how long footage is kept and who can retrieve it. Under modified comparative fault, the fault split effectively is the claim, which is why recorded evidence carries so much weight.