Police are appealing for witnesses to alleged dangerous driving on the A11 on Friday.
The drivers of two silver Renault vans were seen being driven erratically and at speeds alleged to be in excess of the limit at about 2.30pm where the A14 joins the A11.
It was reported the vans were being driven side-by-side while the drivers were chatting to each other out of their windows. They were also seen to be using mobile phones whilst driving.
Suffolk Police say at the Five Ways roundabout on the A11, at Barton Mills, one of the vans changed lanes, suddenly braked and the driver started talking again to the other van driver.
This caused a lorry driver to take avoiding action, nearly colliding with one of the vans. Both vans continued their journey on the A11 towards Attleborough.
Anyone who witnessed the manner of driving of either van at around the time stated or who has dash-cam footage of the vans should contact Suffolk Police quoting CAD 300 of March 9.