"I was suspecting they were fighting and that's why it happened. Although the car was fast all of a sudden they went full steering turn."
Moments later, two people emerge from the damaged car.
The pair then appear to enter into an altercation with each other near the front of the car. Not long after the driver falls to the ground.
The witness said he then saw the passenger appear to "hit" the driver.
"The person came out of the car and then the driver came out and he [the passenger] started hitting the driver and then the person [the driver] fell down."
"I was so lucky even if my car was a little faster or something they could have hit my car."
A police spokesperson said officers were looking into the crash.
"A crash was reported in northbound lanes of the Southern Motorway near Takanini at 7.46pm on Wednesday night," the spokesperson said.
"No serious injuries were reported, but at least one person was taken to hospital."