Police said the prime mover and trailer loaded with building material flipped over as it turned from Rooty Hill Road onto Richmond Road at about 12.20pm.

The truck then collided with a passenger van being driven by a 79-year-old woman.

The truck driver, a man in his mid-to-late 30s, and the woman in the van, escaped with only minor injuries and were treated by ambulance crews at the scene.

The overturned truck and trailer blocked two east-bound and three west-bound lanes at the busy junction.

As traffic backed up causing major delays, NSW Fire Brigade crews, police and RTA inspectors assessed the damage.

The accident site was eventually cleaned up and the truck towed away by 3.45pm.

Detective Inspector Grant Bissett from the Mt Druitt police command said the truckdriver was breath-tested at the scene, which returned a negative reading.

He said investigations were continuing.