Watch: Shocking footage shows car causing two near-misses within seconds in Christchurch

Dash cam footage shot on Thursday afternoon shows the moment a driver nearly caused two separate crashes, all within seconds of each other.

The footage was taken on the Christchurch expressway and uploaded to Facebook.

It shows a grey car merging into the expressway and immediately changing lanes multiple times. At first, it nearly hits the car with the dash cam, then swerves away rapidly, nearly hitting the white 4WD on the left.

The driver who shot the video said she nearly crashed the car trying to get away from the other vehicle.

She told the Herald the man driving the car that nearly caused the crashes knew what he'd done when he sped off from the area.

The driver nearly caused two separate crashes within seconds. Photo / Facebook

"It just came out of nowhere and I had cars on my side and behind me," the driver, who'd rather not be named, recalls.

"They didn't even look. I nearly crashed into the middle concrete barrier."

The driver of the grey vehicle merging into the expressway was reportedly a young male.

"I tried to get their attention but they refused to look," she added.

"They sped off but we had to stop further ahead because of traffic. They thought it was hilarious and were having a wee giggle," the driver added.

"I was pretty lucky to not have crashed," she said.