Having completed a two-year investigation, the US National Transportation Safety Board said Tuesday that Tesla's Autopilot driver assistance system was partially to blame for the death of a Model X owner.

The vehicle, owned and driven by Apple engineer Walter Huang, veered left into a concrete barrier on Highway 101 in Mountain View, California on March 23, 2018. Its Autopilot system was engaged at the time of the incident, the NTSB's investigation found, but incorrectly steered to the left into a highway gore, before striking a crash attenuator at the end of a concrete median barrier at 71mph.

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Huang was removed from the vehicle by witnesses as the Model X burst into flames due to damage to its battery pack, but later died in hospital from his injuries.

The NTSB's findings firstly state that driver distraction was a key factor, as cell data records showed a game was being played on Huang's company-issued iPhone at the time of the collision.

Tesla Autopilot is also blamed for Huang's death, for not providing "an effective means of monitoring the driver's level of engagement with the driving task," the NTSB's report said. The system was also blamed for having no restrictions on where it can be activated by the driver, despite having known limitations, along with an inability to detect the crash attenuator. The car's emergency braking system did not activate.

The NTSB also raised concerns with how the National Highway Traffic Safety Administration (NHTSA) takes a non-regulatory approach to automated driving technology. The report said: "NHTSA should complete a further evaluation of the Tesla Autopilot system to ensure the deployed technology does not pose an unreasonable safety risk."

The Model X P100D crashed into a freeway barrier at 71mph Getty Images

Furthermore, the NTSB asked for car manufacturers to provide more data collected by the vehicle in the event of a crash. Driver assistance systems collect a significant amount of data, the NTSB said, adding: "Currently, manufacturers provide limited access to this data and there is no standardization of retrievable data parameters."

Finally, it was found that the crash attenuator struck by the Tesla was "in a nonoperational damaged condition because of a previous crash, which had occurred 11 days earlier".

In conclusion, the Board stated probable cause for the accident as: "The Tesla Autopilot system steering the sport utility vehicle into a highway gore area due to system limitations, and the driver's lack of response due to distraction likely from a cell phone game application and over reliance on the Autopilot partial driving automation system. Contributing to the crash was the Tesla vehicle's ineffective monitoring of driver engagement, which facilitated the driver's complacency and inattentiveness."

Addressing Apple, the NTSB asks that a company policy is created to ban the non-emergency use of portable electronic devices while driving by all employees and contractors.

Addressing Tesla, the NTSB said it must "incorporate system safeguards that limit the use of automated vehicle control systems to those conditions for which they were designed." It also asks the automaker to "develop applications to more effectively sense the driver's level of engagement and alert the driver when engagement is lacking while automated vehicle control systems are in use."