The NTSB’s preliminary report said the driver engaged Autopilot about 10 seconds before crashing into a semitrailer, and the system did not detect the driver’s hands on the wheel for fewer than eight seconds before the crash.
The vehicle was traveling at about 68 miles (109 km) per hour (mph) on a highway with a 55-mph (89-kph) speed limit, and neither the system nor the driver made any evasive maneuvers, the agency said.
Tesla said in a statement that soon after the crash it shared information with regulators about the Autopilot status and said after the driver engaged the system he “immediately removed his hands from the wheel. Autopilot had not been used at any other time during that drive.”
The company added that “Tesla drivers have logged more than one billion miles with Autopilot engaged, and our data shows that, when used properly by an attentive driver who is prepared to take control at all times, drivers supported by Autopilot are safer than those operating without assistance.”
While some Tesla drivers say they are able to avoid holding the steering wheel for extended periods while using Autopilot, Tesla advises drivers to keep their hands on the wheel and pay attention while using the system.
The incidents have raised questions about the safety of systems that can perform driving tasks for extended stretches of time with little or no human intervention, but which cannot completely replace human drivers.
In May 2016, a Tesla Model S driver was killed near Williston, Florida, while Autopilot was engaged, when he slammed into a tractor trailer that also sheared off the vehicle roof.
In a fatal crash in Mountain View, California, in March 2018 involving a Model X in Autopilot mode, Tesla said vehicle logs showed the driver had received warnings to put his hands on the wheel but no action was taken by the driver ahead of the crash. That incident is being investigated by both the NTSB and the National Highway Traffic Safety Administration.
The NTSB said in 2017 that Tesla lacked proper safeguards allowing the driver “to use the system outside of the environment for which it was designed and the system gave far too much leeway to the driver to divert his attention.”
The auto safety regulator, NHTSA, is also probing the Delray Beach crash and investigating a fatal incident in Davie, Florida, on Feb. 24 involving a 2016 Tesla Model S that caught fire and burned the 48-year-old driver beyond recognition. It was not clear if Autopilot was engaged in this incident.
NHTSA can demand a recall if it believes a defect poses an unreasonable safety risk, while the NTSB makes safety recommendations.
The NTSB said it had reviewed forward-facing video from the Tesla in the Delray Beach crash.
NHTSA is also probing the January 2018 crash of a Tesla vehicle apparently traveling in Autopilot that struck a fire truck in Culver City, California; a May 2018 crash in Utah of a Tesla in Autopilot mode; and a May 2018 Tesla accident in Florida that killed two teenagers and injured another but was not in Autopilot mode.
The NTSB is also investigating an August 2017 Tesla battery fire in California, in which an owner ran the vehicle into his garage.