A preliminary report released by the National Transportation Safety Board on Thursday said that a Tesla Model X traveling on Autopilot increased the vehicle's speed before it crashed into a highway barrier and killed its driver.
The report of the March 23 crash that killed 38-year-old Walter Huang details the minutes and seconds before impact, and echo other accounts of Tesla's Autopilot self-driving software failing to avoid or brake for objects.
Investigators said that Huang was traveling southbound on U.S. Highway 101 near Mountain View, California, near State Highway 85 when the Model X he was driving veered into a painted highway separator and struck a damaged barrier.
Huang's Model X split and spun, striking two other cars, and burst into flames. Huang was pulled from the car and was pronounced dead at a hospital.
According to the San Francisco Chronicle, Huang complained to his family earlier that his 2017 Tesla Model X had attempted to veer into the barrier while on Autopilot before.
A spokeswoman for Tesla declined to comment on the report, but offered the company's March 30 response that pointed to the damaged highway barrier as a contributor to the severity of the crash.
According to data pulled from the Model X, Huang set his 2017 Model X on Autopilot at 75 mph as he traveled south. Fifteen minutes before the crash, investigators reported that the Model X gave two visible warnings and one audible warning for Huang to place his hands on the wheel.
In the minute leading up to the crash, the vehicle's event recorder showed that Huang had his hands on the wheel three separate times, for a total of 34 seconds, but didn't touch the wheel for six seconds leading up to the crash.
The Model X that Huang was driving was following another car that was traveling 65 mph for several seconds before the crash, but four seconds before impact it was no longer following that car. Three seconds before the crash, the Model X sped up from 62 to 70.8 mph before hitting the barrier at roughly 71 mph.
Investigators said that the Model X didn't attempt to brake or steer clear of the crash.
The report—and grizzly photos—come amid increased scrutiny of Tesla for it's Autopilot system that the automaker touts as "self-driving."
Earlier this year, a Utah woman crashed her Model S into a firetruck at 60 mph while reportedly using Autopilot. Early media reports have said that the software may have sped up before that crash too. A federal report is pending.
Federal investigators in May removed Tesla from the official investigation into the California crash after the automaker seemingly blamed the driver for the crash publicly.
In a shareholders' meeting this week, Tesla CEO Elon Musk didn't directly answer questions about the safety of its Autopilot system, but said that a significant revision would be pushed to cars next week. Musk has been highly critical of media reports on Autopilot-related crashes.
UPDATE: This story has been updated to include comment from Tesla.