WATCH: The moment a hero truckie rolled his rig to save other drivers

The terrifying moment a truck driver who had lost his brakes, risked his life to spare other motorists has been caught on camera.

Seven News obtained video which shows the runaway truck career towards the busy base of Adelaide's South Eastern Freeway, past one arrester bed already in use, with smoke issuing from the brakes.

The truck can then be seen veering left - leaving the freeway.

Motorists watch with horror as the rig crashes.

7 News obtained shocking video of the moment the rig crashed. Source: 7 News
7 News obtained shocking video of the moment the rig crashed. Source: 7 News
It was a lucky escape for the 55-year-old truck driver. Source: 7 News
It was a lucky escape for the 55-year-old truck driver. Source: 7 News

Sturt footballer Jack Osborn was travelling behind the SMS Bitumen driver who was carrying a load of gravel.

"I knew at the speed that he wasn't going to make it, I just wasn't expecting him to flip," Jack Osborn told 7 News.

"It was a bit scary because he had a bit of blood on his arms and the back of his head, but he was walking around. He said he was Ok."

It was a lucky escape for the 55-year-old driver, but fellow truckies say it could have been far worse.

Truck driver, Steve Wagner said, "I take my hat off to him. Done very well he did, very, very well."

Mr Osborn said, "Oh I think he's a very brave man. I couldn't imagine what was going through his head at the time."

The cause of yesterday's brake failure remains unanswered. Source: 7 News
The cause of yesterday's brake failure remains unanswered. Source: 7 News

Truckies know how dangerous this road can be. In August 2014 an out of control truck killed two people and injured another in one of the worst crashes at the bottom of the freeway.

The cause of the brake failure on Friday remains unanswered.

Police told 7 News that oil on the brakes may have contributed to the crash - but they're not investigating further and no charges have been laid.

SMS Bitumen declined to comment.