When someone charters a stretched limousine or a party bus of some type, you're really relying on the driver of that vehicle to drive carefully and obey the law. If they don't and you get injured in an accident, you may have a claim against the driver and/or the company that owns the vehicle.
Another thing that can happen in these kinds of vehicles is maybe another driver makes a mistake and runs into the limousine or party bus and causes an accident. In a case like this, you could have a claim against that driver just as if you were riding in your own car.
If you've been in an accident involving a limousine or party bus where you are the passenger, you should speak with a lawyer to make sure you understand what your legal rights of recovery might be.