Of course motorists can have a pure accident - my well maintained and serviced bike suffered a front wheel collapse. This certainly could happen to a motorvehicle, or they could suffer a blow-out and lose control of the vehicle as a result. There are a number of accidents that can befall everyone.
Another time I was brought down by a diesel slick - I guess that is preventable, by the spill not being there, buit they do happen. A motorist could have crashed at the same point I did, certainly a motorbike.
The final one is so utterly random. A woman stepped out into the road from between parked cars, I emergency stopped, and didn't hit her (so my speed was not a cause of this one) I did stop right in front of her. She fainted and I instinctively reached out to try and catch her, but was clipped in and ended up sprawled in the road.
I suppose the last one is also preventable - if I hadn't reached out for her, I wouldn't have hit the deck, but it definately counts as an accident IMO.