The scene was filmed on the 15 Freeway in Los Angeles County and posted to Facebook by another motorist, Brian Steimke.
Other drivers honked their horns and someone finally got in front of the truck and stopped it.
The auto was apparently dragged for more than six kilometres on the Cajon Pass before other motorists flagged down the truck driver.
Miraculously, the California Highway Patrol said the driver of the vehicle is okay. The crash wasn't considered a criminal incident, according to the California Highway Patrol.
When the truck driver was asked why he kept driving he replied, "I didn't know".
The truck driver seems to be unaware as he continues to drive, until the video shows motorists slowing down to a stop in front of the truck to urge him to come to a standstill. Steimke asked the truck driver.
"Steimke added: "'What do you mean you didn't know it dude?
An intense video captured on a California freeway shows a large tractor trailer truck dragging a auto, seemingly unaware the two vehicles had gotten into an accident.
The driver of the Nissan was not seriously injured, and was dragged less than a mile.