A horrific eight vehicle pile-up that left six people needing medical attention may have been caused by a mechanical fault in an out-of-control truck.

CCTV caught the Scania diesel tanker ploughing through the intersection of Parramatta and Great Northern Roads in Five Dock, Sydney, during peak hour on Friday.

The truck mounted a curb before colliding with seven other vehicles which had stopped at the traffic lights, leaving a trail of bonnets and doors on the road.

Emergency services responded at 4:30pm and were helped by a group of tradies who jumped into action, pushing vehicles to safety and removing the people inside.

Police are now investigating what could have caused the pile up which sprawled across three eastbound lanes of Parramatta Road and covered more with debris.

One theory that NSW Police are considering is that a mechanical failure in the truck may have prevented it from being able to stop at the intersection.

‘The truck continued through the intersection, mounting the kerb before continuing eastbound while a Holden Captiva struck a Nissan X-Trail stopped in the westbound lanes,’ NSW Police said in a statement.

The truck ploughed through the line of cars before the driver, 53-year-old Hamish Middleton, was able to pull into a nearby petrol station.

Police seized the relatively unscathed truck at the scene and took it away for mechanical examination.

‘He just went straight through seven cars and he just kept going, it was horrifying. I’ve never seen anything like it,’ one witness told 7News.

Every corner of the intersection had a car on it and one survivor of the crash, Maddi Brunton, said that her car was not even hit by the truck itself.

‘Everybody else got taken out and then we sort of got hit by the other cars,’ she told 7News.

‘[I’m] just happy that we’re okay really, as long as my passenger is all good then I’m all good,’ she later told 9News.

Bystanders and a group of tradies helped with the recovery effort, with the group of tradesmen seen physically lifting a car back onto the road to help the person inside.

Paramedics attended to six people from four cars who had sustained non-life threatening injuries before taking them to various hospitals throughout the area.

The injured included a 47-year-old woman driving a Mazda 3 and her 56-year-old passenger, a 33-year-old female driver of an MG, the 62-year-old male driver of a Holden Captiva, a 56-year-old male driver of a Toyota Corolla and his 57-year-old female passenger.

Four more women, a 27-year-old VW Jetta driver, 54-year-old Hyundai driver, 23-year-old Mazda 6 driver, and a 23-year-old Nissan X-trail driver, were also impacted by the crash but were able to walk away uninjured.

A crime scene has been set up near the intersection which was inspected by specialist officers from the metropolitan crash investigation unit before the wrecked cars were removed late Friday night.

Mr Middleton, from New Zealand, escaped without injury and returned a negative breath test at the scene.

Witnesses described him as pale, shaking and in utter shock after he first exited the truck’s cabin, screaming for somebody to call triple-0.

Police temporarily took Mr Middleton to Burwood Police Station before releasing him shortly thereafter.

Mr Middleton is an experienced truckie and has been driving trucks for more than 27 years.

His employer, APW,  said that it was working alongside authorities with their investigation and that it would provide any support needed to aid the process.

Extracted in full from:  https://www.dailymail.co.uk/news/article-12958887/Five-Dock-Sydney-car-crash-police-investigate-mechanical-failure.html