As expected, federal safety regulators closed a months-long investigation into Tesla’s Autopilot feature after the fatal crash occurred when the semi-autonomous driving feature was activated, finding that the collision was not the result of a defect in the feature.

The National Highway Traffic Safety Administration revealed the findings [PDF] of its six-month long investigation, noting that Tesla’s Autopilot feature worked as it was intended and that the last action taken by the driver occurred two minutes before the collision.

According to NHTSA, the autopilot feature and emergency braking system were not to blame for the death of the 40-year-old Florida man.

The crash occurred on a divided highway, where the 2015 Model S collided with a tractor-trailer that was making a left turn across the Tesla driver’s lane.

In spite of its controversial name , Autopilot was designed to require the continual and full attention of the driver to monitor the traffic environment and be prepared to take action to avoid crashes.

NHTSA determined that it worked as it was intended, and that drivers are made aware of the need to remain vigilant when the function is active through Tesla’s owner manual and other systems.

Still, the agency notes that Tesla could do more to ensure drivers are engaged at all times.

“The systems have limitations and may not always detect threats or provide warnings or automatic braking early enough to avoid collisions,” NHTSA said in its report. “Although perhaps not as specific as it could be, Tesla has provided information about system limitations in the owner’s manuals, user interface and associated warnings/alerts, as well as a driver monitoring system that is intended to aid the driver in remaining engaged in the driving task at all times.”

Tesla addressed some of these concerns in a September update that it claims will better incorporate the use of radar and makes changes to the way in which drivers must keep their hands on the wheel.

In addition to not finding any defect with Autopilot, NHTSA investigators concluded that the driver should have been able to see the tractor-trailer for at least seven seconds prior to impact.

Because of this, NHTSA believes the man may have been “able to take some action before the crash, like braking, steering, or attempting to avoid the vehicle.”

However, NHTSA found that data from the vehicle showed the driver took no braking, steering or other actions to avoid the collision. The driver’s last recorded action, according to the report, was actually increasing his cruise control speed to 74 mph; that occurred less than two minutes before the fatal collision.

“A safety-related defect trend has not been identified at this time and further examination of this issue does not appear to be warranted,” NHTSA states, referring to the closing of the investigation.

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