Supplemental Liability Insurance (SLI) protects you and your passengers in case you're involved in an accident and a third party sues for bodily injury and property-damage claims.
Supplemental Liability Insurance ("SLI"): Where available, and for an additional daily charge, a renter may purchase SLI at the time of rental. If accepted, SLI provides the renter or any additional authorized drivers listed in the rental agreement, with automobile liability coverage against third party claims (excluding claims by the renters and any additional authorized drivers family members related by blood, marriage or adoption and any other person residing with the renter or additional driver) for bodily injury, including death, and property damage resulting from an automobile accident in the rented vehicle, during the rental period, in excess of the coverage provided under the rental agreement up to a maximum protection of $1,000,000 combined single limit (CSL) per occurrence. The availability, cost and coverage can vary from location to location depending on the program details. Check with the rental location for details of their program.
The renter may not need the automobile insurance offered by the rental car company. The purchase of automobile liability insurance is not required as a condition of renting an automobile. This insurance does not apply to any bodily injury or property damage arising out of the use or permitting the use of a rental vehicle by any driver while under the influence of drugs or alcohol in violation of the law.