NTSB preliminary report: Tesla was speeding, Autopilot engaged

According to system performance data that was downloaded from the Model S, the driver was going 74 mph in a 65 mph zone. The data also revealed that the driver was using Autopilot.

The NTSB specifically calls Tesla's Autopilot system "Traffic-Aware Cruise Control and Autosteer." The agency also pointed out that the Model S is equipped with automatic emergency braking that should apply the car's brakes to avoid a frontal collision. The NTSB's preliminary report didn't provide any information on why the collision occurred.

A team of five investigators conducted the on-scene phase of the preliminary investigation, which included the use of three-dimensional laser scanning technology to document the damaged trailer, crash location, as well as the damaged vehicle. The team of investigators is still collecting data from the vehicle's electronic systems to analyze the crash.

The accident occurred when a tractor trailer drove across the four-lane highway perpendicular to the oncoming Model S, which struck and passed underneath the semi trailer. The Model S then coasted roughly 297 feet down the right side of the highway and collided with a utility pole. After breaking the pole, the car traveled an additional 50 feet until it came to a stop perpendicular to the highway. The accident occurred in dry weather conditions under broad daylight.

The accident is believed to be the first known fatality involving Tesla's Autopilot system and, according to Tesla, is the first death involving Autopilot in more than 130 million miles of total owner use.

The National Highway Traffic Safety Administration (NHTSA) is also conducting its own investigation into the accident.