KANIVA police are seeking further information.as they continue to investigate an incident of "erratic" driving on the Western Highway.
Senior Cnstable Adrian Hoggett said a truck westbound on the highway east of Lawloit forced two vehicles off the road at 1.10pm on Monday.
"It also forced an oncoming red Mazda 3 travelling east off the road to avoid a head-on collision," he said.
"We are seeking the registration of the Mazda 3 for further information to help with our investigation."
Senior Constable Hoggett said a truck driver was intercepted an hour later by South Australian Highway Patrol. He said police had yet to speak to the driver and no charges had been laid.
"We have genuine safety concerns for people with the kind of driving from that truck," he said.
He said anyone with information could call Crime Stoppers or 5392 2244.