Cal Stanley Thompson, 20, of Winnap, pleaded guilty in the Warrnambool Magistrates Court to driving in a dangerous manner.

Police said the P-plater left Melbourne about midnight on November 15 to drive the four-hour trip home to Winnap, near Dartmoor.

He drove along the Western Freeway and, at 2am, stopped for a break near Rockbank.

Thompson performed a U-turn about 3.40am and travelled east at 80 kilometres an hour into oncoming traffic.

Multiple drivers were forced to swerve to avoid collisions and witnesses contacted police.

One driver took evasive action and pulled into the emergency lane, but Thompson collided with that vehicle, causing minor damage to his car.

He stopped about 20 metres away. Police officers arrived and Thompson was breath tested but returned a clear result.

He was arrested and taken to Melton police station.

When interviewed, Thompson said he had no recollection of driving on the wrong side of the road.

Defence counsel Xavier Farrelly said Thompson had been playing poker at Crown Casino before driving home.

He said it was a serious offence but the end result was not too severe and, thankfully, no-one was injured.

Magistrate Michael Coghlan said he found it difficult to understand how anyone could drive up the wrong side of a dual freeway and not know what was going on.

"It sounds very odd to me,” he said.

“He's lucky he's not going to jail for culpable driving. It's very fortunate someone was not injured or killed.” 

Thompson was convicted and fined $2000 with $117 costs and his driver's licence was cancelled for nine months.