Justin Phillip Jago, 37, faced the Launceston Magistrates Court today on charges of having injured property and having driven without reasonable consideration for other road users.

He had previously pleaded guilty to the charges and a disputed facts hearing was scheduled after the defence submitted that two men from the other car had threatened Jago before he threw the glass bottle.

However, police prosecutor Kelly Brown told the court that she had been unable to contact the witnesses from the other car and would not seek a warrant for their arrest.

The court heard in January that about 6.10pm on March 19 last year, Jago was driving a Ford Falcon south along the West Tamar Highway at Legana.

Jago passed a Chrysler 300 sedan, travelling in the same direction, near roadworks and sprayed stones onto the Chrysler, driven by a woman.

Both cars later stopped at traffic lights and there was a verbal altercation between Jago and passengers from the Chrysler.

Jago eventually stopped near Tamar Marine and threw a glass bottle, which struck the rear of the woman's car, causing damage to the boot.

Today, defence solicitor James Patmore reiterated his submission that his client overtook the Chrysler lawfully on an unsealed road, causing stones to unintentionally spray against the other car.

Mr Patmore said the two male passengers of the Chrysler subjected Jago to threats of violence over a distance of about 10km before Jago lost his temper and threw the bottle.

He said that Jago was concerned because he had his wife and two young children in his car.

Magistrate Michael Brett said he questioned Jago's overtaking of the other car in a roadworks area, even if it was lawful.

He said the bottle throwing was serious, but he accepted the defence submission that Jago had been subject to a long period of what seemed to be "road rage" on the part of the occupants of the other car.

Mr Brett convicted Jago and fined him $350.