Lesley Fuller lives nearby and was the first person on top of the Mount Keira Road overpass when she heard a loud bang, and promptly dialed Triple Zero.

A six-vehicle accident (including two trucks) had occurred on the M1 Princes Motorway below. It subsequently took the lives of a man and woman when it's believed their car's petrol tank ruptured and burst into flames.

"I grabbed my phone and called emergency services before I was even out my door, because the sound of the crash was so horrifically violent you just knew straight away that emergency services needed to be called," Mrs Fuller told the Mercury.

"It was horrible, like the initial bang, then a screech, then such a big bang - I am presuming it was the explosion of the car. And then it was multiple banging after that.

"I was the first person on the bridge. I just looked down and saw black smoke everywhere from the vehicle crash and all you could see was the passenger cabin of the truck on fire. So it was pretty intense."

The smoke was so thick the witness couldn't see much more than the truck ablaze. She could not hear screaming or yelling, but knew the situation was dire.

"I got through to the Firies first at 2:06pm and then as soon as I got off that call I called back at 2:09pm to get in contact with the rest of the services ... and while I was on the phone I could hear the sirens," Mrs Fuller said.

"The response time was amazing ... they did such a terrific job yesterday, I am so proud of Wollongong and what we have here.

"All the emergency services don't get a thought of what they have just seen or what they have to deal with."

Meantime, accidents near that overpass are a weekly occurrence, she said, with loud bangs and screeching tyres often heard.

"I've lived here for five years and it's a weekly thing - someone will either hit [another car] or someone will scrape up against the bridge, or every day there is a truck beeping their horn," Mrs Fuller said.

"People are absolute lunatics and they're always weaving in and out of traffic."

Police believe a four-wheel drive heading south and a prime mover with a dog trailer attached initially collided.

Another four vehicles - a Mitsubishi Pajero, an Isuzu rigid truck, a Honda Odyssey, and a Toyota Prado - were drawn into the crash.

A 65-year-old Lansdowne man has been charged with dangerous driving and negligent driving occasioning death. He will face Wollongong Local Court on July 23.

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