Safety regulators in the United States are investigating after the driver of a Tesla car operating on autopilot was killed after crashing into a truck.
It is the first known fatality to involve a Model S operating on Autopilot and comes as Tesla Motors and other carmakers are gearing up to offer systems that allow vehicles to drive themselves under certain conditions across a wide range of vehicles over the next several years.
The accident that killed Joshua Brown on a clear, dry roadway on May 7 this year in Williston, Florida, will add fuel to a debate within the auto industry and in legal circles over the safety of systems that take partial control of steering and braking from drivers.
Tesla said in a blogpost on Thursday that "neither Autopilot nor the driver noticed the white side of the tractor trailer against a brightly lit sky, so the brake was not applied."
Its shares fell as much as 3% in afterhours trading on news of the fatal crash on Autopilot and the investigation. The company emphasised the unusual nature of the crash and that it was the first fatality in more than 210 million kilometres of use.
"It is important to note that Tesla disables Autopilot by default and requires explicit acknowledgement that the system is new technology and still in a public beta phase before it can be enabled," Tesla said in a statement Thursday.
"When drivers activate Autopilot, the acknowledgment box explains, among other things, that Autopilot 'is an assist feature that requires you to keep your hands on the steering wheel at all times,' and that 'you need to maintain control and responsibility for your vehicle' while using it."
The National Highway Traffic Safety Administration said the crash "calls for an examination of the design and performance of any driving aids in use at the time of the crash."
The agency said it has opened a preliminary investigation that is the first step before the agency could seek to order a recall if it finds the vehicles were unsafe.
NHTSA said preliminary reports indicate the vehicle crash occurred when a tractor-trailer made a left turn in front of the Tesla at an intersection.
A police report obtained by Reuters states that the Model S operated by Brown went under the trailer of a truck that turned left in front of the car.
The Tesla's roof was torn off, and the car kept going, leaving the road, striking a fence, crossing a field, passing through another fence and finally hitting a utility pole about 100 feet south of the road, according to the report.
The company 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."
When Autopilot launched in October, Tesla chief executive Elon Musk cautioned the hotly anticipated function was in beta mode, or a test phase of development, with full 'hands-off' driving not recommended.
Tesla said that "Autopilot is getting better all the time, but it is not perfect and still requires the driver to remain alert. Nonetheless, when used in conjunction with driver oversight, the data is unequivocal that Autopilot reduces driver workload and results in a statistically significant improvement in safety when compared to purely manual driving."
In January this year, Tesla updated the Autopilot driving systems in Model S sedans to put new limits on its hands-free operation, which has been both praised for its innovation while criticised for having been launched too early.
The function will now be restricted on residential roads or roads without a centre divider, meaning the car cannot drive faster than the speed limit maximum plus 8km/h.
A host of subsequent videos posted by Tesla drivers on YouTube showed near-misses on the road with Autopilot, prompting Musk to say he might curb the function to minimize the possibility of people doing "crazy things."
