The system of automobile accident insurance that a state adopts answers the following question: How is the individual financially responsible for an automobile accident determined? There are three varying systems of automobile accident insurance available: no fault, at fault, and a combination of no fault and at fault.

A driver's insurance company compensates an insured individual, whether responsible for the accident or not, for personal economic damages in a no fault system automobile accident; damages can range from funeral or medical expenses or lost wages.

This coverage of personal economic damages is called Personal Injury Protection or PIP. It is imperative that every vehicle driver has automobile insurance with them under this system. The tradeoff for each driver's insurance company paying for their own insured's economic damages is each driver is prohibited from suing the other driver for non-economic damages, such as pain and suffering or loss of companionship.

Theoretically, insurance rates or premiums should be lower in no fault states since insurance companies are saving money by not having to initiate lawsuits or defend their insured's in court. There is not one no fault system for automobile accidents in existence currently in any one state.

Instead, states have either adopted an at fault system or a combination of no fault and at fault for automobile accidents. When an automobile accident occurs in an at fault state, the driver responsible for the accident - the driver who is at fault - or their insurance company pays for damages.

Although, determining the individual at fault for the accident can be a difficult and complicated decision. And in many accidents both drivers are to blame to some extent. Since each driver pays based on their own proportion of fault, drivers may sue each other to determine these proportions. Fault systems state that any damages, whether economic or not, which result from an automobile accident are open for a driver to sue the other for such damages.

If a state has adopted a combination system or a modified no fault system for automobile accidents, drivers are compensated by their insurance companies for economic damages up to the policy limits and also have a right to sue the other driver in certain situations. Usually a driver may sue another driver for damages sustained in an automobile accident if the damages exceed a certain dollar amount that each state has set by statute. Some states also allow lawsuits in automobile accidents if a driver's injuries meet a specified standard of severity, for example, "serious personal injury".

A state can also choose to change their liability system for automobile accident insurance at any time through the state's legislature. It is best, when determining insurance system types in a state, to speak with the insurance provider or state insurance board.