It's sad but shows that auto pilot also needs human input. Reading the news it indicates that the camera couldn't distinguish between the side of the White trailer and the bright daylight which is scary but then probably no worse than people who drive in glaring low sun with no visor down or sunglasses on.
The other driver said the car was going so quick he never even saw it going underneath. I would have assumed the driver/passanger may have seen the impending vehicle and may have tried to stop the car and wouldn't have waited on the auto pilot to kick in but if it was going too fast, probably wouldn't be enough to stop the impact unfortunately.
For all we know that same accident may have happened without auto pilot, it just so happens the car he was driving was equipped with it and the driver was a huge fan of the system.