Comparative negligence laws dictate how the responsibility for an accident will be shared between the parties directly involved in an accident where bodily injury or property damage occurred. When both parties contributed to the accident, comparative negligence determines who will receive compensation for losses and how much will be received.

Comparative negligence is most often used to assign blame in auto accidents by determining or apportioning fault between two parties. If two drivers both break the same traffic laws in an accident, such as running red lights or ignoring other traffic lights or road hazards, then both may be denied their claims.

In determining negligence, a court will use a percentage system called “comparative fault,” dividing your total loss by the total fault. Under Missouri Revised Statute § 537.765, Missouri is a comparative fault state, meaning that people should take care of their own safety and welfare. As an example: If you run a red light and collide with another driver who has $10,000 in damages and the court determines that while you did run a red light, the other driver had sufficient enough time to try and avoid colliding with you. Because you are ruled to be 80 percent responsible and the other driver is 20 percent responsible, you must pay $8,000 to the other driver.

Illinois has adopted modified comparative negligence. Under 735 ILCS 5/2-116, an injured party may recover damages only if they are less than 50 percent at fault for the injuries or damages. However, the recovered amount may be reduced in proportion to the degree that the injured party was at fault. For example, if the other driver is determined to be 80 percent at fault and you are determined to be 20 percent at fault, you can collect for your damages because you were less than 50 percent at fault.