It was later revealed by Tesla officials that the Model X had the company's Autopilot feature activated in the moments prior to the crash, which the NTSB report describes as advanced driver assistance including cruise control and autosteer "lane-keeping assistance." The vehicle's cruise control speed was set to 75 miles per hour, which ratchets downward based on a set "following distance" between the Tesla and slower-moving vehicles in front of it.
A detailed account of the Tesla's vehicle logs found that the driver had used the Autopilot system on four separate occasions during the 32-minute trip, including 19 continuous minutes prior to the collision. In the final minute leading up to the crash, the driver had his hands on the steering wheel for 34 seconds, but not during the six seconds prior to the collision.
Within the span of eight seconds, the Model X was following a "lead" vehicle and maintaining a 65 mile-per-hour speed, began a left-steering motion while following the lead vehicle, and began accelerating when it was no longer following a vehicle. The Tesla sped up from 62 miles per hour to 70.8 miles per hour before striking the crash attenuator in the highway median, with "no pre-crash braking or evasive steering movement" detected, according to the report.
The NTSB report emphasized that the findings are preliminary in nature and not a final determination on the "probable cause" of the crash.
"The NTSB continues to work with the California Highway Patrol and the California Department of Transportation to collect and analyze data, including all pertinent information relating to the vehicle operations and roadway configuration," according to the report.
In a blog post shortly after the crash, Tesla officials wrote that the damage to the Model X was so severe because the crash attenuator had been damaged in a prior crash, providing less of a cushion between the vehicle and the highway median. The NTSB report confirms that the attenuator had been damaged in a crash on March 12, 11 days prior to the fatal accident, and a large portion of the safety cushion had been sheared off.
Shortly after the collision, the vehicle's 400-volt lithium-ion battery was damaged and caught fire, prompting the Mountain View Fire Department to blast the vehicle's interior and exposed portion of the battery with 200 gallons of water and foam, according to the NTSB report. The department also received support from Tesla engineers before determining the battery had cooled enough to transport to a San Mateo impound lot.
The report also recounts how, five days later on March 28, the vehicle's high-voltage battery reignited and was extinguished by the San Mateo Fire Department.
Tesla originally partnered with the NTSB to investigate the crash, but was dropped from the investigation in April after NTSB officials said the company released "incomplete information" that was neither vetted nor confirmed by the NTSB. The information, released by Tesla in a series of blog posts and statements to the media, implied that the driver was at fault for the fatal crash.
"Such releases of incomplete information often lead to speculation and incorrect assumptions about the probable cause of a crash, which does a disservice to the investigative process and the traveling public," according to the April 12 statement.
Last month, Bloomberg reported that Tesla CEO Elon Musk had hung up on NTSB Chairman Robert Sumwalt during an exchange about the company's statements and the decision to kick the company off the investigation. Tesla officials claimed that it was the company that withdrew from the investigation, rather than getting ousted, prior to the April 12 announcement by the NTSB.
This story contains 704 words.
Stories older than 90 days are available only to subscribing members. Please help sustain quality local journalism by becoming a subscribing member today.
If you are already a subscriber, please log in so you can continue to enjoy unlimited access to stories and archives. Subscriptions start at $5 per month and may be cancelled at any time.