A driver's inattention, overreliance on his car's advanced driver assistance system, and use of the system inconsistent with manufacturer guidance, coupled with the system permitting driver disengagement from the driving task, led to the Jan. 22, 2018, crash in Culver City, California, according to a National Transportation Safety Board brief issued Wednesday.
The results of the NTSB's investigation of the crash involved a Tesla Model S P85 and a Culver City Fire Department Culver City Engine 42 in the high-occupancy vehicle lane of southbound Interstate 405.
The fire crew was working a motorcycle down call on the 405 Freeway that Monday morning.
There were no injuries reported. However, firefighters on the scene commented that it "scared the heck out of them."
The driver reported the Tesla S was on autopilot and he was not paying attention. Culver City Firefighters at the time reminded everyone to "Please stay alert while driving!"
In response to requests for comment at the time, a Tesla Inc. spokesperson didn't address the specific accident, but they pointed out that autopilot requires the attention of the driver.
"Autopilot is intended for use only with a fully attentive driver," the spokesperson said.
The driver kept his hands off the wheel for all but 51 seconds of the final drive segment and received numerous alerts to place his hands back on the wheel, the documents showed. Tesla Inc. did not immediately comment.
The fire truck was unoccupied, and the driver was not injured in the incident.
"I was having a coffee and a bagel. And all I remember, that truck, and then I just saw the boom in my face and that was it," the man behind the wheel told the NTSB.
He did not remember precisely what he was doing at the time of the crash but could have been changing the radio or drinking coffee. Records show the driver was not using his cellphone to text or talk at the time of the crash, the NTSB said.
The response to a collision in the northbound freeway lanes 25 minutes earlier left a California Highway Patrol vehicle parked on the left shoulder of southbound I-405 and the Culver City Fire Department engine parked diagonally across the southbound HOV lane.
Emergency lights were active on both vehicles. The Tesla, which had its "Autopilot" system engaged, was traveling in the HOV lane, behind another vehicle. After the lead vehicle changed lanes to the right, the Tesla remained in the HOV lane, accelerated and struck the rear of the fire truck at a recorded speed of about 31 mph.
A forward collision warning alert occurred 0.49 seconds prior to impact but the automatic emergency braking system did not engage. The driver's hands were not detected on the steering wheel during this sequence nor did the driver apply steering or braking prior to impact.
The NTSB determined the probable cause for the crash was the Tesla driver's lack of response to the fire truck parked in his lane, due to his 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.
Culver City Fire Department Engine 42 was dispatched to the Belair fire as part of a strike team from several westside fire departments.