The National Transportation Safety Board has released preliminary findings from its investigation into the Tesla Semi crash on Monday, August 19. That crash caused a fire so hot and dangerous that authorities had to shut down both sides of I-80 and wait hours before firefighting aircraft could even approach the blaze.
Thursday NTSB, in collaboration with ​F​ederal Motor Carrier Safety Administration, California Highway Patrol and Tesla, Inc., announced the basic details of the incident, which began around 3:13 a.m.
"A 2024 Tesla Semi, a battery-electric truck-tractor, was involved in a single-vehicle crash while traveling east on Interstate 80 (I-80) near Emigrant Gap in Placer County, California," NTSB wrote. "The vehicle, operated by a Tesla, Inc. employee, was en route from Livermore, California, to a Tesla facility in Sparks, Nevada."
The Semi "departed the roadway to the right while navigating a right-hand curve and uphill grade" before striking a "traffic delineator permanently mounted on a steel post" and ultimately colliding "with a tree about 12.5 inches in diameter" and continuing "down an earthen slope to rest against several trees."
NTSB found the Semi was not able to engage its advanced safety features.
"While the Tesla Semi was equipped with Advanced Driver Assistance Systems (ADAS), ADAS was not operational on the vehicle and could not be engaged at the time of the crash," NTSB wrote.
NTSB noted that I-80 at that location consists of two lanes in each direction with a maximum posted speed limit of 65 mph and 55 for commercial vehicles. The Tesla Semi has frequently been seen passing trucks in the left lane just 20 miles away up the Donner Pass section of I-80, but NTSB did not say if the Semi was speeding.
[Related: Tesla's Semi blows past diesels uphill, but do owner-ops care?]
After the impact, the "vehicle’s lithium-ion electric battery system ignited..., resulting in a postcrash fire," NTSB wrote. Thankfully, the driver was uninjured.
CHP, the California Department of Forestry and Fire Protection (CAL FIRE), and the California Department of Transportation (Caltrans) all deployed to the scene, along with a Tesla technical expert who assisted "in assessing high-voltage hazards and fire safety."
EV fires pose a novel threat to roadways and firefighting teams. In this case, CAL FIRE representatives told Overdrive that the blaze took hours of dousing to lower the temperature enough to even fly firefighting aircraft overhead.
Placer County places extensive restrictions on residential water use, and advises its residents to reduce use by doing things like turning off the water while soaping up your hands or installing low-flow toilets.
But the Tesla fire required "about 50,000 gallons of water to extinguish the flames and cool the vehicle’s batteries," NTSB said.
Authorities also tested air quality and used a thermal scanner to monitor the batteries' temperature, though NTSB didn't say how the fire impacted air quality. CAL FIRE representatives cited air quality and toxic fumes as a reason for closing both lanes for so long.
Ultimately, "the westbound and eastbound lanes of I-80 remained closed for 14 and 15 hours, respectively, for firefighters to ensure the batteries were at a safe temperature for vehicle recovery operations and to prevent the spread of the fire to surrounding forest."
Following that crash, and another that shut down I-15 for two days, a group of California lawmakers wrote a letter to California Governor Gavin Newsom urging him to delay the state's Advanced Clean Fleets rule, which bans the sale of diesel trucks in the state by 2036.
The high profile interstate closures due to battery fires may impact policy going forward.
NTSB will continue investigating the I-80 fire to determine "the probable cause, with the intent of issuing safety recommendations to prevent similar events."
[Related: Trucking to EPA: Send CARB 'back to the drawing board' for ZEV truck-purchase mandates]
