The National Transportation Safety Board has released its preliminary report on the March crash that killed driver Walter Huang in Mountain View. The report provides a second-by-second description of the events that preceded Huang's collision with a concrete lane divider.

The report confirms that Autopilot was engaged ahead of the crash, and it appears to confirm that a navigation mistake by Autopilot contributed to Huang's death.

Huang's Model X was driving south on US highway 101 just ahead of a point where a left-hand exit split off from the main road. Logs recovered by the NTSB show that eight seconds before the crash, the vehicle was following behind another car, traveling at 65mph.

Then, seven seconds before the crash, "the Tesla began a left steering movement while following a lead vehicle." That "left steering movement" carried the vehicle into the "gore area"—a triangular area of paved road that separated the highway's main travel lanes from the diverging exit lane.

At four seconds before the crash, the Tesla vehicle was no longer following the car ahead of it. The car's cruise control was set to 75mph, so it began to accelerate, reaching a speed of 70.8mph just before the crash. There was "no precrash braking or evasive steering movement detected," the NTSB says.

Huang's hands were detected on the steering wheel for 34 seconds out of the final minute of his trip. His hands were not detected on the steering wheel for the final six seconds prior to the crash.

Tesla has said that Huang received warnings to put his hands on the wheel, but according to the NTSB, these warnings came more than 15 minutes before the crash.

Tesla has emphasized that a damaged crash attenuator had contributed to the severity of the crash. The NTSB report confirms that. The crash attenuator—an accordion-like barrier that's supposed to cushion a vehicle when it crashes into the lane separator—had been damaged the previous week when a Toyota Prius crashed at the same location. The resulting damage made the attenuator ineffective and likely contributed to Huang's death.

After the crash, bystanders removed Huang from his burning vehicle. He was taken to the hospital, where he died from his injuries.

The crash created a big battery fire that destroyed the front of Huang's vehicle. "The Mountain View Fire Department applied approximately 200 gallons of water and foam" over a 10-minute period to put out the fire, the NTSB reported.

The car was towed to an impound lot, but the vehicle's batteries weren't finished burning. A few hours after the crash, "the Tesla battery emanated smoke and audible venting." Five days later, the smoldering battery reignited, requiring another visit from the fire department.

A Tesla spokeswoman declined to comment on the report, referring us back to Tesla's earlier blog posts on the subject.