The crash occurred on May 7 in Williston, Florida, when a tractor-trailer made a left turn in front of the Tesla at an intersection, according to the National Highway Traffic Safety Administration.
Tesla (TSLA) said in a blog post that its autopilot system did not recognize the white side of the tractor trailer against a brightly lit sky, so the brake wasn't activated. It also noted that this is the first known fatality in over 130 million miles when autopilot was activated.
The "autopilot" system of Tesla literally did not see the white of a tractor trailer. The lower-cameras of the Tesla S did not see the tractor trailer because it was too high off the ground. The driver didn't notice the trailer either. But that's the problem with these semi-autonomous driving rigs: if an edge case comes up that it wasn't designed for, the driver is still bearing the responsibility.
Tesla's official response is here.
Following our standard practice, Tesla informed NHTSA about the incident immediately after it occurred. What we know is that the vehicle was on a divided highway with Autopilot engaged when a tractor trailer drove across the highway perpendicular to the Model S. Neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied. The high ride height of the trailer combined with its positioning across the road and the extremely rare circumstances of the impact caused the Model S to pass under the trailer, with the bottom of the trailer impacting the windshield of the Model S. Had the Model S impacted the front or rear of the trailer, even at high speed, its advanced crash safety system would likely have prevented serious injury as it has in numerous other similar incidents.
This isn't the first time that Tesla's sensor setup demonstrated a weakness to trailers with high clearance.