CRASH experts have dismissed claims that an unknown third car was the cause of an horrific fatal accident at East Lynne that left four people dead.

Two crash investigators told Batemans Bay Coroner's Court there was no physical evidence that supported claims that a petrol tanker lost control going around a corner because it swerved to avoid another car.

Yesterday marked day two of the inquest into the deaths of 36-year-old Narellan Vale petrol tanker driver David Carolan, two young Ulladulla girls - Jordan Bridge, 13, and her sister, Makeely, 11 – and their father David Bridge.

The girls died instantly when their car burst into flames after colliding with Mr Carolan's petrol tanker.

The girls' parents, Debbie and David, were pulled from the burning car, but Mr Bridge, 47, died in hospital a week later.

Debbie, 42, suffered burns to 80 per cent of her body, but survived and has been present during the inquest.

Senior Constable Phil Hamilton of the Southern Region Crash Investigation Unit said if there was a third car involved, Mr Carolan would have swerved harshly, and marks would have appeared on the road.

"I would have expected to have seen some tyre marks veer off to the left," he said. "I wouldn't say it was impossible (this happened), but it would be extremely difficult (for the car) to be on the incorrect side of the road and to have been no collision occur."

He believed the accident happened because Mr Carolan took the corner too fast.

This was also the opinion of civil engineer Grant Johnston, who also investigated the crash.

"(The tanker's) speed was about at the speed limit but for that specific radius, unfortunately, it was at the threshold, and it rolled," he said.