Further, for self driving cars, the moment something novel happens to them, it won't be novel to pretty much every self driving car running on the same software anymore (and assuming some basic data sharing between manufacturers, probably to all self driving cars). So a mattress falling is a novel situation for every driver the first time it happens to each individual driver. It's a novel situation for self driving cars only the first time it happens to any one of the self driving cars sharing the same model.
The liability issue is not very useful. We would have to change laws slightly, but the insurance for self driving cars will be far more predictable, and the likes of Geico will probably give the owners of self driving cars better insurance than they would owners of human driven cars, because their safety record would be better.
In fact, I bet if self driven cars come with the ability to also be driven by a human, once they're a little established, the ones that do have this feature will be far more expensive dive to insure than the ones that are purely self driven.
However identification of a novel problem and the anticipation that it will be a harzard in the near future is a trait that is only needed if your reaction time is too slow.
A self driving cars reaction time will be fast enough that it doesn't need to anticipate anything. It will identify the the velocity of objects (it does not need to know what the object is) in front of it within in milliseconds of it becoming a harzard and decide on the correct corrective manouever to avoid it within milliseconds again.