Tesla Motors is reporting that one of its Model S electric cars was involved in a fatal incident while its autopilot mode engaged.  The company is cooperating with US federal investigators, but simultaneously emphasizing that its autopilot feature is a "driver assist" feature, and drivers who use it must keep their hands on the wheel at all times.

On 7 May, 40-year old tech executive Joshua Brown of Ohio was driving his Model S through Williston, Florida, and turned on the autpilot.  A big rig truck in oncoming traffic made a left turn across traffic.  Brown's Tesla apparently couldn't distinguish between the white-painted truck and the sky over the road ahead on a clear and dry day, and it kept going.  The car drove underneath the trailer.  Tesla said "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."  The bottom half of the car continued on a short bit before crashing into some trees.  Mr. Brown died at the scene.

The National Highway Traffic Safety Administration said it is investigating 25,000 Model S sedans that are equipped with the Autopilot system.  It's likely to set off a debate about so-called self-driving systems and if it's actually safe to rely on them.  Tesla says its Autopilot feature is still in beta:  It does not transform the Tesla into a fully autonomous car, and the driver still needs to stay in control at all times. 

Despite that, drivers proudly and publicly have abdicated their responsibility to the car.  A popular internet video purports to show a man napping while his Tesla navigates traffic.  A member of a Tesla owner message board recently claims he uses his free hands to play air guitar.  And Joshua Brown himself posted a video that at the very least suggests a casual reliance on the system, seven months before he was decapitated in Florida.  A month before the crash, he uploaded a video crediting the car with automatically avoiding a collision with a reckless truck driver.