A Perth man has captured on video what he's described as the "worst driving" he's seen in 30 years.

For almost half an hour driver Simon followed a white ute as it drifted erratically across lanes on the Mitchell Freeway.

The man was so sure he was about to witness a crash he called police twice, as other drivers were forced to take evasive action.

View photos Simon began recording as this white ute began drifting across lanes. Source: 7 News More

The footage was captured just before 7pm on Friday night and the erratic driving lasted more than half an hour.

Simon initially spotted the ute near the Powis Street freeway exit.

View photos The erratic driving lasted half an hour. Source: 7 News More

After following it for a few minutes with his dash cam rolling, he called police.

"I was really worried that there was going to be an accident," he told 7 News.

Concerned someone was going to be hurt, he continued following as the driver exited at Whitfords Avenue and pulled over.

With no sign of police, Simon called again.

"Seriously, he's going to kill someone," he told police.





View photos After pulling over temporarily, the driver starts up again. Source: 7 News More

As the ute got back onto the freeway, his time heading south, Simon kept his distance.



More than 10 minutes of dangerous driving later, he gave up.

"That's the worst driving and the worst incidence of that in over 30 years," he said.

View photos Simon said it was the worst driving he had seen in 30 years. Source: 7 News More

7 News contacted the company that owns the ute and was told by the director that he was still trying to work out who was driving - but said "appropriate action" would be taken.

Police have a copy of the footage and are also investigating.