The driver killed when his Tesla car crashed while in self-driving mode was travelling at 9mph above the speed limit just before hitting the side of a tractor-trailer, federal accident investigators have said.
Data downloaded from the Tesla Model S shows the vehicle was travelling at 74mph in a 65mph zone on a divided highway in Williston, Florida, near Gainesville, the National Transportation Safety Board (NTSB) said in a preliminary report.
Joshua Brown, 40, a tech company owner from Canton, Ohio, was using the vehicle's cruise control and lane-keeping features at the time, the report said. Those features are part of the vehicle's Autopilot self-driving system, but the NTSB report does not mention the system.
The National Highway Traffic Safety Administration (NHTSA), which is also investigating the crash, has previously said the Autopilot was engaged.
The Tesla's roof struck the underside of the truck's 53ft semi-trailer at a 90-degree angle, shearing off the car's roof before it emerged on the other side of the trailer, according to the report. The truck was making a left turn at the time.
The vehicle is equipped with automatic emergency braking.
Tesla and the NHTSA have previously said the Autopilot was unable to distinguish the white side of the truck from the brightly lit sky and there was no attempt to brake by either the self-driving system or Mr Brown.