My favorite story, but not so favorite experience was when about 10 years
ago my SO (now wife) and I drove Hiway 80 from Davis to San Fran. We were
behind a horse trailer at 60 mph and both noticed how the gate became
unlatched. There was no time to pass the truck and alert the driver: the
horse, realizing there was some unused space behind it, took a step back,
then two, and slipped and tumbled out of the trailer and onto the tarmac.
We had seen it coming, turned on the hazards, and were able to stop in
time. The horse got back up and miraculously seemed unharmed. I pulled it
back to the side of the road and it was clearly shaken. More people
stopped, but the trailer kept on truckin', not realizing what had
happened. 

Sami (in pre-VW times)