NTSB Prelim Report on fatal Tesla Model X crash: 8-seconds before impact

The National Transportation Safety Board has issued a preliminary report on the tragic Tesla Model X crash near Mountain View, CA in March. The NTSB’s preliminary report provided details about the circumstances leading up the accident, as well as observations about the all-electric SUV’s battery pack five days after the crash.

According to the NTSB, preliminary recorded data revealed that the Tesla Model X had its Autopilot engaged with Traffic-Aware Cruise Control set to 75 mph at the time of the accident. The vehicle collided into the crash attenuator, rotating it counterclockwise, removing the front part of the vehicle, and causing subsequent collisions with a 2010 Mazda 3 and a 2017 Audi A4. The NTSB noted that the vehicle’s performance data revealed the following.

The aftermath of the Tesla Model X’s fatal crash. [Credit: S. Engleman/NTSB]

• Autopilot was engaged on four separate occasions during the 32-minute trip. The driver-assist feature was engaged for the last 18 minutes 55 seconds before the collision.
• During the 18 minute, 55-second period, the Model X provided two visual and one auditory alert advising the driver to place his hands on the car’s steering wheel. The alerts were triggered more than 15 minutes prior to the accident.
• For the last 6 seconds before the collision, the Model X’s driver did not have his hands on the steering wheel. 
• At 8 seconds before the crash, the Model X was following a lead vehicle at about 65 mph. At 7 seconds, the Model X began moving left while still following a lead vehicle. At 4 seconds, the Tesla was no longer following a car. At 3 seconds before the accident, the Model X’s speed increased from 62 mph to 70.8 mph. The vehicle’s emergency braking and evasive steering did not engage.
• During the collision sequence, the Model X’s lithium-ion battery was breached, causing a fire. The flames were extinguished after the Mountain View Fire Department applied about 200 gallons of water and foam during a period of fewer than 10 minutes. In the afternoon, the battery emanated smoke and audible venting was heard, though no flames were observed.
• On March 28, 5 days after the accident, the Model X’s battery pack reignited. The San Mateo Fire Department extinguished the fire.

The NTSB noted in its preliminary report that it is continuing work with the California Highway Patrol and the California Department of Transportation in investigating the accident. The NTSB stated that all aspects of the crash remain under investigation, and that it intends to issue safety recommendations to prevent similar incidents from taking place.

Tesla and the NTSB initially worked together in investigating the fatal Model X accident. The electric car company and the safety board eventually parted ways, however, due to Tesla’s decision to release crash data before the NTSB’s investigation was complete. Among the information Tesla released was that the driver did not have his hands on the wheel during the final 6 seconds leading up to the accident — information that has been reiterated in the NTSB’s preliminary report. 

According to a Tesla, it opted to withdraw from its party agreement with the NTSB since collaboration with the safety board prevents the public release of safety information until the investigation was finished. People familiar with the matter, however, noted that the NTSB was the one which opted to terminate its collaboration with Tesla, according to a Bloomberg report.

In an update after the accident, Tesla highlighted that the absence of a crash attenuator — a highway safety device designed to absorb the impact of a collision — was already damaged when the Model X collided with the concrete barrier.  In a statement to ABC7 News, Wil Huang, the brother of the ill-fated Model X driver, noted that a working crash attenuator would have saved his brother’s life. Later statements from CalTrans revealed that safety device had been left unrepaired for 11 days before the tragic Model X accident.