Fuel tanker speeding before crash: court

A truck driver was hurtling downhill at more than three times the speed limit before he flipped his fuel tanker and caused a crash that killed two people, a jury has heard.

Five others were injured when the Cootes truck driven by Shane Anthony Day barrelled down Mona Vale Road on Sydney's northern beaches in 2013 before hitting a pole at the bottom of the hill, crashing into several cars and bursting into flames.

"The collision led to a rupturing of the tanker, causing a large explosion and fireball," crown prosecutor Craig Patrick SC told the court on Thursday.

"Burning fuel began leaking from the tanker and flowed down the road back towards the roundabout.

"As it did so, it engulfed the impacted vehicles."

Peter Wem and Graham Holtfreter managed to free themselves from their car but could not escape the fire and were engulfed in flames, Mr Patrick said.

The pair died metres from their scorched car.

Another man, Neil Donaldson, was badly burnt when his car also caught fire, the court heard.

Day, who was hauling 34,000 litres of diesel and unleaded petrol, is facing two counts of dangerous driving causing death and another of causing serious injury.

He has pleaded not guilty.

Mr Patrick told Sydney's Downing Centre District Court Day had reached 86km/h before the crash and failed to heed signs that warned of a steep descent and to use low gear.

If Day had been using low gears, Mr Patrick said, his speed would not have exceeded 25km/h.

However, defence lawyer Grant Brady SC said his client was not driving dangerously but was behind the wheel of a vehicle "simply unfit" to be on the road.

"Mr Day's brakes failed. That caused the accident. Mr Day was not driving in a dangerous manner," he told the court.

Ten out of 12 of the tanker's brakes were defective and another was due for replacement, he said, adding it was "an accident waiting to happen".

Mr Patrick said the crown would argue Day should not have been relying on his brakes.

"(The brakes) were not the cause of the collision," he said.

"Rather, it was the accused's over-reliance on the primary brakes rather than driving in a low gear, as he was required to do, which was the cause of the collision."

The trial is expected to run for four weeks.