Guide · Injury · Chicago

Comparative Fault in Common Chicago Crashes: How the 51% Rule Plays Out

The rule is the same everywhere in Illinois. The arguments that move the percentage change at a crosswalk, a left turn, a bike lane, or a store aisle.

By Lincoln Square Law · 8-minute read

Illinois’ comparative fault rule is simple to state: a plaintiff’s damages are reduced by the plaintiff’s share of fault, and a plaintiff found more than 50% at fault recovers nothing (735 ILCS 5/2-1116). How that rule plays out depends on the kind of crash or fall. The same percentage fight looks very different at a crosswalk, a left turn, a bike lane, or a grocery store aisle, because each setting has its own rules of the road, its own evidence, and its own familiar defense arguments. Our companion article explains the rule itself and how juries apply it. This guide walks through the situations where fault is most often disputed in Chicago and what tends to decide them.

Rear-end collisions

A driver must not follow another vehicle more closely than is reasonable and prudent, having due regard for speed and traffic conditions (625 ILCS 5/11-710). Rear-end collisions therefore start with a strong presumption against the following driver in practice, but the defense will look for ways to shift some fault: a sudden stop without reason, brake lights that did not work, or a lane change directly in front of the following car. Dashcam video, event data showing speed and braking, and witnesses who saw the lead car’s movements usually decide whether any fault moves.

Left turns at intersections

A driver turning left must yield to oncoming vehicles that are within the intersection or so close as to be an immediate hazard (625 ILCS 5/11-902). The turning driver usually bears most of the fault, but the defense often argues that the oncoming driver was speeding, ran a yellow or red light, or was distracted. Signal timing, traffic camera footage, event data, and the point of impact become the key evidence. Because the difference between 45% and 55% decides whether a plaintiff recovers at all, a left-turn case can turn entirely on a few seconds of video.

Pedestrians

Illinois requires drivers to stop and yield to pedestrians crossing within a crosswalk where traffic control signals are not in place or not in operation (625 ILCS 5/11-1002). Pedestrians also have duties, including not suddenly leaving a curb and walking into the path of a vehicle so close that it is impossible for the driver to yield. Defense arguments in pedestrian cases usually focus on whether the pedestrian was in a crosswalk, whether the pedestrian had the signal, dark clothing at night, and phone use. Scene measurements, lighting conditions, and video are often decisive.

Cyclists and dooring

A person riding a bicycle on a roadway has the rights and duties of a vehicle driver (625 ILCS 5/11-1502). A driver passing a bicycle must leave at least three feet of distance (625 ILCS 5/11-703(d)). And no one may open a vehicle door on the side of moving traffic unless it is reasonably safe to do so and it can be done without interfering with traffic (625 ILCS 5/11-1407), which is the rule that governs the “dooring” crashes common on Chicago streets. Defense arguments in bicycle cases often point to riding outside a bike lane, lack of lights at night, or riding against traffic. The statutory duties of drivers are frequently the strongest answer.

Seatbelts

Illinois law provides that failure to wear a seat safety belt is not evidence of negligence and does not diminish any recovery for damages arising from the operation of a motor vehicle (625 ILCS 5/12-603.1(c)). A defendant generally cannot use the plaintiff’s failure to buckle up to reduce the plaintiff’s damages under the comparative fault rule. That rule surprises many people, and it is one of the reasons early insurer questions about seatbelt use should be answered carefully and accurately rather than casually.

Falls on another’s property

In premises cases, the defense often argues that the hazard was open and obvious, meaning a reasonable person would have seen and avoided it. The Illinois Supreme Court has explained that when a condition is open and obvious, a landowner may still owe a duty if it should anticipate harm despite the obvious nature of the hazard, such as when a person is likely to be distracted or has a reason to encounter the hazard deliberately (Bruns v. City of Centralia, 2014 IL 116998). Even when a duty exists, the plaintiff’s own attention becomes part of the comparative fault analysis. Photographs of the hazard, lighting, footwear, and what the plaintiff was carrying or looking at all matter.

Multiple defendants and the empty chair

When more than one party may be at fault, the plaintiff’s percentage is compared against the total fault of all the defendants sued and certain others, and the allocation among defendants affects who pays. A defendant whose fault is less than 25% of the total fault attributable to the plaintiff, the defendants sued, and certain third-party defendants is generally only severally liable for damages other than medical expenses (735 ILCS 5/2-1117). Defendants may also point to a party who is not in the case, an “empty chair,” to argue that someone else caused the crash. Identifying and suing every responsible party early reduces the room for that argument. If one defendant settles before trial, the Joint Tortfeasor Contribution Act reduces the remaining defendants’ liability by the amount of the settlement (740 ILCS 100/2(c)), which also affects strategy.

Impairment and distraction

Evidence that a plaintiff was impaired or using a phone is powerful at trial and is frequently raised by the defense. Illinois generally prohibits hand-held phone use while driving (625 ILCS 5/12-610.2). Phone records cut both ways: they can show the other driver was distracted, or they can be used against the plaintiff. Evidence of a plaintiff’s impairment does not automatically bar recovery. It is weighed as part of the plaintiff’s share of fault, but it can strongly influence how a jury sees the rest of the evidence. Honesty with your own lawyer about these facts early allows the evidence to be evaluated before the defense presents it.

Buses, city vehicles, and road defects

When the other party is a public body, comparative fault is only one of the issues. Crashes involving Chicago Transit Authority buses are governed by the CTA’s own statute, which requires written notice and sets a one-year period for filing suit (70 ILCS 3605/41). Claims against the City and other local public entities generally must be filed within one year (745 ILCS 10/8-101), and the Local Governmental and Governmental Employees Tort Immunity Act limits liability in several ways. For a road or sidewalk defect, a local public entity has a duty to maintain its property in a reasonably safe condition, but generally is not liable unless it had actual or constructive notice of the condition in time to fix it (745 ILCS 10/3-102). In these cases, the fault percentage matters only after the claim clears the notice and immunity questions, which is why they need attention in the first weeks.

What moves a percentage

Across all of these scenarios, the same kinds of evidence tend to decide the numbers:

• Video. Traffic cameras, business and doorbell cameras, dashcams, and transit cameras.
• Vehicle data. Speed, braking, and throttle from event data recorders.
• Physical evidence. Scene measurements, points of impact, and damage patterns.
• Neutral witnesses. People with no stake in the outcome.
• Your own words. Statements to police and insurers, which the defense will quote.

Statutes and early evidence move the percentage

The 51% rule is the same everywhere in Illinois, but the arguments that move a plaintiff’s percentage depend on the setting. Traffic statutes such as the left-turn, crosswalk, following-distance, and dooring rules often give a plaintiff firm ground, and the seatbelt statute takes one common defense argument off the table. Evidence gathered early, especially video and vehicle data, is what keeps a disputed percentage on the right side of 50.