In the other case, a father let his son's girlfriend use his car but expressly prohibited his unlicensed son from driving it. Later that night, the son drank and asked for the keys. The girlfriend initially refused, but then relented, and the son crashed into a tree. Farm Bureau Mutual Insurance Co. of Michigan, the father's insurer, denied PIP benefits for the son.

In both cases, the health care providers sued the auto insurance companies in order to try to get PIP benefits paid.

In a July 31 ruling, Michigan's high court sided with the insurance companies and said that any person who takes a car unlawfully, including a family member who takes the car for a joyride, is excluded from receiving PIP benefits.

Gusner has this advice for parents: "Lock up the keys if you have teenagers."

Agosto agrees: "All my car keys are in my safe in a locked closet in my bedroom, which is locked -- not because I have bad kids, but because kids get together with other kids," he says. "Leaving the keys out is like leaving out a loaded gun." receives compensation from carriers when readers choose to request insurance quotes. This article is provided by an external partner that is solely responsible for the content.