Glossary: If you work for a company or government entity and drive a car owned by them, your initial protection will come from said entity. However, if the claim is in excess of those underlying coverages you may be held responsible for that excess. Check with your company or government entity to see what their policy is. In any event, it is not a bad idea to have your insurance agent add an endorsement to your policy to protect you while you are in control of the non owned vehicle.