The police want to hear from anyone who might have seen or filmed the head-on crash on William Hovell Drive on Thursday last week.
Both drivers were taken to hospital with serious injuries, though neither has since died.
The police said they had already talked to some witnesses but were keen to get any dash-cam footage that might be available.
The crash happened on a three-lane road, with two lanes separated from the other single lane by a double white line.
"About 6.30am, police and emergency services responded to a collision between a white Toyota Camry and a black Hyundai Tucson on William Hovell Drive, approximately one kilometre west of John Gorton Drive, Whitlam," the police said.
"Anyone who can assist is urged to contact Crime Stoppers on 1800 333 000, or via the Crime Stoppers ACT website. Please quote reference number 7876836. Information can be provided anonymously."
A police "major crash team" was on the scene, trying to ascertain which car had crossed into the other's path, and why that might have happened.
Fire and ambulance crews were also there, west of the John Gorton Drive and Coppings Crossing Road intersection.
Motorists were advised to use an alternative route, but that caused severe traffic delays throughout the area as drivers cut through "rat runs".
