Investigations into the cause of a crash that involved two heavy vehicles near Condah this morning are still ongoing.

At about 7.50am, a B-Double truck travelling at 60 to 70 kilometres an hour north on the Henty Highway, after turning onto the thoroughfare, was rear-ended by a heavy rigid delivery truck.

The truck at the rear than lost control losing the braking system and came to a halt on the left side of the road, having run into an unoccupied grader belonging to the Glenelg Shire.

The passenger of the delivery truck was trapped and it took emergency services about 20 minutes to get the 46-year-old Reservoir man out of the wreckage.

The B-Double driver, a 38-year-old man from Portland, walked away unharmed as did the 33-year old-driver of the delivery truck.

Heywood Police Sergeant Callum McKinnon said investigations were ongoing and stated the people involved in the accident were very lucky to have not been injured, or killed.

"We will continue to investigate the matter, it's a peculiar event and we will be talking to all involved to see if we can work out just where things went wrong here," he said.

"This absolutely is a remarkable outcome in that no one was hurt at all from the collision, it could have been heaps worse.

"How it wasn't a fatality or caused serious injury is beyond me, we are very lucky everyone walked away from that."