A January 2018 crash involving a Tesla and a firetruck was due to driver inattention and the “Autopilot” system design that allows motorists to disengage, federal investigators said Wednesday.

The Culver City, California crash took place when a Tesla “Model S” rode into a firetruck that had been parked in the high-occupancy vehicle lane when the vehicle the Tesla had been trailing changed lanes, said a press release from the National Transportation Safety Board.

The Tesla, which had Autopilot engaged, veered into the firetruck at 31 miles per hour. The driver’s hands were not detected on the steering wheel, nor did the driver brake prior to the crash, the NTSB said.

The NTSB blamed the driver’s “inattention and overreliance on the car’s advanced driver assistance system; the Tesla’s ‘Autopilot’ design which permitted the driver to disengage from the driving task; and the driver’s use of the system in ways inconsistent with guidance and warnings from Tesla,” according to a press release.

There were no injuries in the Culver City accident. Some other accidents involving Autopilot have resulted in fatalities.

Tesla literature describes Autopilot as a tool to enhance driving, but says that “current Autopilot features require active driver supervision and do not make the vehicle autonomous.”