Police said multiple people sustained serious injuries in the crash, which is under investigation.
The road was blocked and closed but has since reopened.
People who knew the victim paid tribute on a Christchurch news Facebook page.
"Such a tragic loss, and he leaves behind some beautiful kids and an amazing partner," said a family member.
Another woman close to the victim posted: "I'm completely, utterly broken right now - words can't describe the feeling, I'm shattered to pieces."
Daniel van Kessel got to the scene of the crash shortly after it happened got out of his car to help.
He said there were three people, one lying "motionless" on the road, another trapped under the car and a third with serious lacerations to her hand.
"I was driving north on Russley Road at 10.45pm and just as I came over the bridge before the BP station, I was aware of the the fact a lot of brake lights were on up ahead," he said this morning.
"As I got within 50m roughly of the scene, I saw people crossing the road which was definitely not right.
"I have then noticed the vehicle in the south bound lane facing the wrong way looking very banged up."
Van Kessel paked his car and got out.
"I heard a female screaming on the side of the road, and gone to assist her... she told me she had glass stuck in her hand and cannot feel her hand.
"I am then told by some other passers by who had stopped to assist that there is a female stuck under the car - a silver Subaru wagon or similar).
"This female is calling to the first female I had spoken with saying they love each other."
He then saw the third person lying face down and motionless on the road away from the vehicle.
Van Kessel called 111, telling them to hurry as other motorists were passing by and could see the deceased victim lying in full view.
By the time he got off the phone police had arrived and officers were pleading with the person on the road to "keep breathing".
Van Kessel offered to help police lift up the mangled car to free the trapped woman, but he said they declined.
Within about five minutes the road was "flooded" with ambulance, fire and police personnel.
Van Kessel gave his name and contact details to an officer and headed home.
He was waiting to give a formal statement to police today.
It is the ninth fatality on the roads during the current holiday period.
Eight other people have died on the roads around the country since Christmas Day, more than doubling last year's entire road toll.
Terry Charleston, 34, and Rebecca McAlees, 24, died in a crash on Christmas night on Clevedon-Kawakawa Rd, south of Auckland.
Hours later, two young men - mates Jack Heritage Jnr and Viliami Muru-Teutau, both 20 years old - died in the early hours of Boxing Day after the vehicle they were in crashed on Triangle Rd in Massey, West Auckland.
James and Kareen Malcolm, of Invercargill, were killed on Monday when their motorcycle collided with a milk tanker on the Riverton-Wallacetown Highway (State Highway 99), between Taramoa Rd and Price Rd.
The eighth fatality was at Kahikatea Rd, Dairy Flat, on Tuesday.
