Obviously you don't have a clue here. Vehicles don't cause accidents, people do. As Kurt pointed out, almost all policies cover the policy holder for liability, regardless of who's car they happens to be driving. That means if I borrow someone's car and cause an accident, my insurance company will cover me to the limits of my policy for damage and injuries I caused to the vehicle I hit. This only makes sense. You think I want to get behind the wheel of someone else's car, say while sharing driving on a trip, have an accident, and then find out they only have the minimal coverage and the accident exceeds that? Or that they let the policy lapse and have no insurance? I don't care about that, because MY policy protects me.
Now, if you have collision coverage on your car, in most cases, that coverage may not extend to another vehicle you happen to be driving.