The vehicle crashed into an energy-absorbing system, called an "attenuator", on a concrete barrier where two freeways divide in Mountain View, Calif. After hitting the attenuator, the Tesla hit two other cars.
The system had provided the 38-year old with two visual alerts and one auditory alert that he must place his hands on the steering wheel.
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.
Tesla shares closed higher Friday ahead of a report from The Consumer Group urging the electric vehicle maker to fix the flaws in its driver assist system to try and avoid further accidents similar to the fatal crash in California in March this year.
The NTSB report notes some other significant details about the vehicle and how fast it was going.
The NTSB said the driver's hands were on the steering wheel for 34 seconds of the final minute, but left the wheel in the final six seconds.
Buyers of Tesla's sedan or SUV, including the $140,000 Model X P100D, can pay an extra $5,000 for "Enhanced Autopilot", a package of still-experimental features that the company says could include "on-ramp to off-ramp" autonomous freeway driving. The driver followed them until taking his hands off the wheel again.
The NTSB report said the vehicle had sped up from 62 miles (99 km) per hour (mph) to almost 71 mph (114 km/h) in the three seconds before the crash.
In the days after the crash, Huang's wife Savonne said her husband had complained about the system not working properly near the area where the crash occurred.
According to the Associated Press, Tesla says its vehicles and systems are not to blame; the drivers are.
Tesla defended its autopilot mode and said in a statement a failure to fix the highway safety barrier exacerbated the crash.
Tesla's system may have a problem spotting or stopping for stationary objects.
A Tesla SUV using the company's semi-autonomous Autopilot driving system accelerated just before crashing into a California freeway barrier, killing its driver, federal investigators have determined.
"It is the driver's responsibility to drive safely and remain in control of the vehicle at all times", the manual says. The SUV also was equipped with automatic emergency braking.
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.
Federal investigators determined the car's semi-autonomous Autopilot driving system accelerated to 71 miles per hour seconds before the crash in California, killing its driver Walter Huang, 38.
Tesla declined to comment on the NTSB report and did not immediately comment Friday, but said in March that Huang had not braked or taken actions to avoid the crash in the final seconds before the accident.
NTSB spokesman Christopher O'Neil told the AP Thursday that, among other factors, investigators are trying to determine how the car's camera, radar and ultrasonic sensors were working and what they were tracking.
A Tesla spokesperson on Monday said the cars would only start offering a limited number of as-yet-undisclosed features, not full autonomy itself.