The Tesla car involved in a fatal crash in Florida this spring was in Autopilot mode and going about 10 miles faster than the speed limit, according to safety regulators, who also released a picture of the mangled vehicle.
Earlier reports had stated the Tesla Model S struck a big rig while traveling on a divided highway in central Florida, and speculated that the Tesla Autopilot system had failed to intervene in time to prevent the collision.
The crash killed 40-year-old Ohio resident Joshua Brown, who was behind the wheel of the Tesla. It is the first known fatality in a Tesla using Autopilot. The driver of the truck was not injured.
The National Transportation Safety Board released a preliminary report Tuesday that confirms some details of the May 7 collision, along with a photo that shows the car with its windshield flattened and most of its roof sheared off.
The federal agency also included a photo of the big rig, circling an area on the right side of the tractor-trailer that showed the light damage the truck received from the collision.
The 2015 Model S was moving at 74 mph, above the posted 65 mph speed limit, when it struck a 53-foot trailer being pulled by a Freightliner Cascadia truck.
Tesla's semi-autonomous Autopilot driving feature was engaged, the report says.
"The car's system performance data … revealed the driver was using the advanced driver assistance features Traffic-Aware Cruise Control and Autosteer lane keeping assistance," the report states. "The car was also equipped with automatic emergency braking that is designed to automatically apply the brakes to reduce the severity of or assist in avoiding frontal collisions."
Not long after the crash, Tesla Motors Inc. Chief Executive Elon Musk speculated that the Autopilot system might not have functioned properly because it could not isolate the image of the trailer from the bright sky behind it. The system's radar, Musk said in a tweet, "tunes out what looks like an overhead road sign to avoid false braking events."
The Palo Alto, Calif.-based automaker has emphasized that Autopilot is still in a "public beta" phase of introduction and has limitations. It has said Tesla drivers are warned to stay alert and keep their hands on the steering wheel because the technology does not provide fully autonomous driving.
This month, Consumer Reports called on Tesla to stop calling the technology Autopilot, saying the name is misleading because it gives the false impression that the system can drive itself without driver input. It also urged Tesla to disable automatic-steering capabilities "until it can be reprogrammed to require drivers to keep their hands on the steering wheel." Tesla declined.
The NTSB said Tuesday that data from the Florida crash site, including laser scans of the crash location, the trailer and the Model S, would be collected and studied.
A final determination might take 12 months, the federal agency said.
12:55 p.m.: This article was updated with additional background information.