Tesla automated vehicle sped up before crash

By: Andrew Hobbs

Vehicle drove into damaged 'crash cushion', according to preliminary US report

Tesla automated vehicle sped up before crash
A southbound view of the March 23 accident, as printed in the NTSB report. Source S. Engelman.


An electric-powered passenger vehicle sped up before crashing into a previously damaged crash attenuator as it approached a state highway interchange, a preliminary report from the US National Transportation Safety Board (NTSB) says.

The Tesla Model X passenger vehicle was being driven with the company’s "Autopilot" features enabled when it crashed into the attenuator – also known as a ‘crash cushion’ – on March 23 this year.

According to the NTSB report, the driver was using the vehicle’s traffic-aware cruise control and autosteer lane-keeping assistance technology while driving on the US Highway 101, when it approached the exit to State Highway 85.

As the Tesla approached the exit, it moved to the left and entered the gore area – the triangular-shaped space that opens up between a major travel land and exit lane – where it hit the crash attenuator, located at the end of a concrete median barrier.

"The impact rotated the Tesla counter clockwise and caused a separation of the front portion of the vehicle," the report said.

Two other vehicles crashed into the Tesla following the accident, which the NTSB said sparked a fire after the crashes breached the Telsa’s 400-volt lithium-ion high-voltage battery.

While bystanders were able to remove the driver from the vehicle before it was engulfed in flames, he later died in hospital from his injuries.

Vehicle sped up

According to the NTSB report, the driver did not put his hands on the steering wheel of the vehicle for six seconds prior to the crash, despite having had his hand on the wheel for 34 seconds of the preceding minute.

The Tesla had been following a lead vehicle and travelling at the speed limit (of 65mph) eight seconds before the crash, the report said, taking advantage of the ‘Autopilot’ system that allows drivers to follow the behaviour of a lead vehicle while maintaining a fixed distance from it.

The vehicle stopped following a lead vehicle four seconds before the crash occurred, the NTSB said after starting a left steering motion just before the accident took place.

"At three seconds prior to the crash and up to the time of impact with the crash attenuator, the Tesla’s speed increased from 62 to 70.8mph, with no precrash braking or evasive steering movement detected," the report said.

Attenuator damaged

In its report, the NTSB noted that the attenuator – or ‘crash cushion’ – had been damaged less than two weeks prior in an un-related single-vehicle collision involving a Toyota Prius.

In blog  posts  released by Tesla following the accident in March, the manufacturer said the condition of the attenuator was "the reason the crash was so severe".

"We have never seen this level of damage to a Model X in any other crash," the company said.

The NTSB did not confirm or deny this, saying it was still working with the California Highway Patrol and the California Department of Transportation to analyse data, including information about vehicle operations and roadway configuration.


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