Federal accident investigators are poised to find that Tesla's auto-driving system should share blame for a fatal 2016 crash in which a Model S sedan drove itself into the side of a truck.

The investigative staff of US National Transportation Safety Board, in its first probe of the wave of autonomous driving systems being introduced by car makers, has recommended that Tesla's Autopilot system be declared a contributing factor in the crash because it allowed the driver to go for long periods without steering or apparently even looking at the road, according to a person briefed on the findings.

Bloomberg