Similar to an uninsured motorist claim, if the parties responsible for your accident do not have ENOUGH liability insurance to compensate you for the full value of your case, you can make a claim for SUM benefits with the insurance carrier for the car you are in when the accident occurs, and if you are a pedestrian or on a bicycle, with the auto policy of any relative resident.
However, this type of coverage is optional and can only be made if you purchased it before the accident.