I definitely agree with the: expect the second car but particularly the trailer. On two occasions I have looked in my mirror and see an empty road behind me except for one upcoming vehicle.
On the mirror there is nothing as far as I can see behind the vehicle, so when the vehicle passes I start moving left to just be within the car lane and to my surprise find out that they were pulling a trailer
that you could not see on the mirror (one was a landscaping trailer and was a pool guy pulling all his chemicals and equipment). I always assume there is a trailer or a second car.
One fall was after a light sprinkle, not significant. The pavement looked dry but I turned slightly on an 6 or 8ft yellow painted area on the road for a golf cart crossing and both wheels flew from under me at the same time.
I was not even touching the brakes.Fortunately no injuries but on the ground in 1.83 seconds!! Those yellow painted areas are like soap when slightly (or completely) wet.