Motorists near Arrowtown were left shaken after they say a car pulled straight out into a busy intersection without stopping.
The truck driver says it's not the only time he'd witnessed such an incident.
He said he experiences what he calls near misses with dangerous drivers on Southern roads at least once a week.
Emergency services were called to Arrow Junction on State Highway 6 just after midday on Tuesday.
"The little rental car completely failed to give way and drove just straight out into the intersection when I was coming through the limited speed zone," said truck driver Glen Collins.
Mr Collins says with a full load on his truck he had nowhere to go and ended up T-Boning the car before colliding with a four wheel drive waiting to turn.
The driver of the car was cut from the vehicle with serious head injuries - Jess Machray says she was travelling behind the car for several kilometres before the crash.
"We thought something like this was going to happen because the car was going quite slow along the road and then we just saw it pull out in front of the oncoming traffic and it's just went flying in the air," she said.
Mr Collins, who's been driving trucks for thirty years, says there needs to be more education about driving on Southern roads.
"From Omararma through to the Crown Range down to Lake Wakatipu is probably some of the worst roads in the country that I drive on - not for the terrain or the conditions just purely for the drivers on the road," he said.
Police are investigating the crash.