Two types of auto insurance are mandated in the US: The no-fault system and the tort system. Used by most states, the no-fault system stipulates that your insurance company will pay your injury claims in the event of an accident (up to a predetermined limit), no matter who caused it.
The tort system, by contrast, stipulates that those who are injured in auto accidents must seek out-of-pocket medical care, and then hold the insurance company of the driver responsible for reimbursement. Such individuals must be able to prove that the medical care was reasonable and necessary. Under this law, the party at fault cannot sue for reimbursement of medical expenses.