The National Transportation Safety Board (NTSB) in the States released data extracted from the vehicle involved in the March 23rd crash.
Federal investigators did not provide a probable cause of the crash, and the inquiry is ongoing.
The report raised an issue for Tesla vehicles with Autopilot, as well as other vehicles with adaptive cruise control, said Bryant Walker Smith, an assistant professor at the University of South Carolina School of Law.
Walter Huang was fatally injured when his Tesla Model X P100D slammed into a previously damaged crash attenuator on Highway 101 in Mountain View on March 23.
Walter Huang, 38, who was wearing his seat belt, was pulled from the blue Tesla by bystanders before the auto was engulfed in flames. In the final minute before the collision, hands were detected on the steering wheel for just 34 seconds. According to the NTSB, not only did the Tesla Autopilot steer into the concrete divider, it actually sped up.
At 7 seconds prior to the crash, the Tesla began a left steering movement while following a lead vehicle. In their report, the NTSB says Huang's Autopilot system sped up to 70.8 miles per hour (from 62 mph) three seconds prior to the crash, rather than slowing down or coming to a stop. At that point, it entered a "triangular-shaped boundary" between the main travel lane and an exit lane. The attenuator had been damaged 11 days earlier in a previous accident and hadn't been repaired, according to NTSB. The NTSB said the crash remains under investigation and that it could make changes to its preliminary report as it does more research on the matter.
"The focus isn't Tesla's technology", he said. Four seconds before the crash it was no longer following the lead vehicle, the NTSB said.
Tesla's system may have a problem spotting or stopping for stationary objects.
Two other vehicles subsequently struck the Tesla, resulting in an additional injury. The driver in that crash sustained only minor injuries.
The crash still remains under investigation, with assistance from the California Highway Patrol and Caltrans. And last month, a Tesla Model S in autopilot mode hit a stopped fire department vehicle in Salt Lake City. Autopilot was in use when the vehicle hit a stopped fire department truck.
Autopilot can steer and brake itself under certain circumstances, but requires drivers to periodically touch the steering wheel to indicate that they are paying attention.
The Tesla collided with a so-called crash attenuator, a device covering the concrete barrier that's created to absorb a vehicle impact to lower risks of damage and injuries. It also may not work all the time, the manual say.
"It is the driver's responsibility to drive safely and remain in control of the vehicle at all times", the manual says. "Never depend on Automatic Emergency Braking to avoid or reduce the impact of a collision". The agency is also investigating a May 8 fire in a fatal Tesla crash in Fort Lauderdale, Florida. No fire was detected by thermal imaging equipment.