The accident happened about 3.30am near the 167 kilometre marker on the highway, but luckily both drivers avoid serious injuries.

They have been described as “lucky boys” by the senior police officer who attended the scene.

Sgt Allan Morrissey of Benalla police described the spectacular collision with fog a contributing factor.

One driver had two trailers carrying about 26 tonnes of water in each.

He drifted to the left of the highway and managed to correct, but the prime mover “jumped” over wire barriers in the centre of the road.

But a trailer was left protruding on the roadway and another truck came along in the foggy conditions.

Sgt Morrissey said the second truck “centre punched” the water tanker causing the cap on the tank to come off with water going everywhere.

“Oh man, it has done some damage,” Sgt Morrissey said.

He said the driver of the second Australia Post truck would have been unable to see the trailer in the fog.

His truck was so badly damaged that specialist salvage equipment is required to move it.

Sgt Morrissey said both drivers received injuries, but they were not life threatening.