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NTSB issues preliminary report on fatal Tesla crash in Mountain View

The National Transportation Safety Bo​ard issued its preliminary report in the investigation of the fatal crash of a Tesla on US Highway 101 in Mountain View, California on 23 March 2018.

According to performance data downloaded from the crash vehicle, a 2017 Tesla Model X P100D, the driver was using traffic-aware cruise control and autosteer lane-keeping assistance, which are advanced driver assistance features that Tesla refers to as autopilot. The vehicle was approaching the state Highway 85 interchange, traveling south on US Highway 101, in the second lane from the left—a high-occupancy-vehicle lane.

Southbound view of US Highway 101 depicting the Tesla, Audi and Mazda vehicles at their final rest locations following the crash. The location of the SCI smart cushion crash attenuator system is also identified. Photo courtesy of S. Engleman. Click to enlarge.

As the vehicle approached the paved gore area dividing the main travel lane of the 101 from the state Highway 85 exit ramp, it moved to the left and entered the gore area at approximately 71 mph, striking a previously damaged, SCI smart cushion crash attenuator system. The speed limit for the roadway is 65 mph. The vehicle’s traffic-aware cruise control was set to 75 mph at the time of the crash.

The Tesla was subsequently involved in collisions with a 2010 Mazda 3 and a 2017 Audi A4. The Tesla’s 400-volt, lithium-ion, high-voltage battery was breached during the crash and a post-crash fire ensued.

The Tesla’s driver was found belted in his seat and bystanders removed him from the vehicle before it was engulfed in flames. The Tesla driver suffered fatal injuries while the driver of the Mazda suffered minor injuries and the driver of the Audi was not injured.

A preliminary review of the Tesla’s recorded performance data showed:

  • The Autopilot system was engaged on four separate occasions during the 32-minute trip, including continuous operation for the last 18 minutes and 55 seconds prior to the crash.

  • In the 18 minutes and 55 seconds prior to impact, the Tesla provided two visual alerts and one auditory alert for the driver to place his hands on the steering wheel. The alerts were made more than 15 minutes before the crash.

  • The driver’s hands were detected on the steering wheel for a total of 34 seconds, on three separate occasions, in the 60 seconds before impact. The vehicle did not detect the driver’s hands on the steering wheel in the six seconds before the crash.

  • The Tesla was following a lead vehicle and traveling about 65 mph, eight seconds before the crash.

  • While following a lead vehicle the Tesla began a left steering movement, seven seconds before the crash.

  • The Tesla was no longer following a lead vehicle four seconds before the crash.

  • The Tesla’s speed increased—starting three seconds before impact and continuing until the crash—from 62 to 70.8 mph. There was no braking or evasive steering detected prior to impact.

The Mountain View Fire Department applied about 200 gallons of water and foam to extinguish the post-crash fire. The battery reignited five days after the crash in an impound lot and was extinguished by the San Mateo Fire Department.

Information contained in the report is preliminary and subject to change during the NTSB’s ongoing investigation. Preliminary reports, by their nature, do not contain analysis and do not discuss probable cause and as such, no conclusions about the cause of the crash should be drawn from the preliminary report, the agency said.

The NTSB’s investigation of the crash is ongoing. Major investigations and investigations of crashes involving fatalities are generally completed in 12 to 24 months.



A tragedy as always and a black eye for Tesla...


  1. What's the per-mile rate of such accidents with Teslas, vs. cars under human control?
  2. What's the rate going to be after the error in the system is identified and fixed?

Unlike the nuts that hold the steering wheels, the cars themselves are only going to get better with age.


Good questions but a more appropriate query would be to compare:

(1) current TESLA's accident rate (while on auto-pilot) vs average accident rate of other vehicles in the same area?

2) TESLA's accident rate (while on auto-pilot) after fix/fixes versus before?

Only TESLA may have the data to do a fair comparison?

Nick Lyons

Meaningful comparisons would be between Tesla S/X and Mercedes S/GS or BMW 5/X5. Use comparable classes of vehicle, classes of drivers in the same region, then you might get some useful data.

Brian P

Given that Tesla still (rightfully) insists that drivers have to continue to pay attention and monitor vehicle operation when using autopilot (even though it's quite apparent that plenty of them don't do so adequately), statements about how autopilot affects collision rates aren't meaningful because it isn't really the autopilot in control if it requires the human driver to take control and/or overrule if autopilot does something wrong.

With the current situation, it's only a matter of time before a vehicle operating in autopilot mode kills someone outside the vehicle. Maybe a pedestrian, maybe a bicyclist, maybe someone in another vehicle. They've already hit two fire trucks and an unoccupied police car (that we know of). When they hit and kill someone ... look out. Uber was in the unfortunate position of having this happen in a highly publicised case early on. Tesla has just been lucky. Can't rely on luck forever.


What is the rate of Tesla traction battery fires in a crash compared to other Western BEV and PHEV makes?

No fires in the Nissan, Renault or GM cars at the crash site.

Tesla with their lousy design are the only ones which burst into flames on crashing.

And that is aside from their intermittently lethal autopilot.

Brian P

Right now, there's no reasonable way to make such a comparison, because (A) Autopilot requires drivers to constantly be paying attention and be ready to take over if something occurs that it can't handle, which means Autopilot isn't really responsible for what is happening, (B) Autopilot is only supposed to be used in the circumstances that it can handle, and that does NOT include traffic control devices (it is incapable of properly handling stop signs and traffic signals, nevermind a policeman waving his arms), and does NOT include adverse weather conditions, construction zones, etc. This means it is only supposed to be used in circumstances in which human drivers already have low risk. Most serious collisions happen at intersections which have traffic control devices (stop, yield, traffic lights) ... which Autopilot can't handle.

There is a list of vehicles out there which, over a particular study period, had ZERO driver deaths recorded. Some of them are reasonably common cars - this isn't because there are none of them on the road. (Google it.) Tesla is not one of them ...

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