The driver, who asked not to be named, said the incident on West Mooreville Road in north west Tasmania was a reminder that road users must drive as if they are the only person on the road paying attention and behaving safely.

"As my Mum used to say when you hop in the car and jump behind the wheel you are driving every other bastard as well as yourself, and that's the best policy.

"Assume no one else knows what they are doing."

He said the truck was only about 50m away when he first saw it.

"I saw his front left-hand wheel actually on the white solid lane," he said.

"That's when that became apparent that something was not good and evasive action was required."

In the dashcam footage which the driver initially shared on social media and with Australian Community Media, viewers can see the truck veer into the appropriate lane at the last moment.

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The truck's trailer appears to still be substantially in the wrong lane as the two vehicles pass, forcing the driver of the car to brake heavily from 60km/h to about 30km/h as they pass.

He said the guard railing on the road is relatively new and meant drivers now had less room to avoid such incidents like this, which he said he had "experienced quite a bit".

Furthermore, as he drives further down the wet road there is clear dual-wheel tyre marks on the wrong side of the road, indicating the truck may have already been crossing to the wrong side of the road.

His first instinct when he saw the truck approaching entirely in his lane was to "minimise".

"You acknowledge there could be a chance you're going to hit something and minimise. That's brake, and just try to evade."

He said he wanted to impress upon other drivers, particular the young and learning, the importance of focus while driving.

"I had about two-and-a-half seconds, maybe three seconds, to react to what was going on here.

"Any distraction from that and you are depriving yourself from time to actually acknowledge what is going on and react."