If you have a homeowners or renters policy in addition to an automobile policy, an have sufficient assets you would like to protect, you may consider purchasing a personal umbrella policy. An umbrella policy protects you by providing additional liability coverage against judgements in lawsuits that exceed the protection of your primary (automobile, homeowners or renters) policies, with higher limits of liability insurance, typically of $1 million or more and may include additional limits of SUM coverage.
In addition to coverage for bodily injury and property damage liability, umbrella policies usually cover additional offenses, such as libel, slander, false arrest, and invasion of privacy. In order to be eligible for an umbrella policy, insurance companies may require you to purchase and maintain certain minimum underlying liability limits on your primary policies.
Note that not all auto insurers may offer this type of policy. You may consider asking your insurer or agent/broker about the availability of this type of policy.