Three of four eastbound lanes are closed near Silverwater Road as emergency services work to free a trapped woman from one of the vehicles.
Initial reports indicate that the woman is in her 60s; her condition is not yet known.
A two-year-old boy was also in the car but is believed to have escaped injury. He is currently being assessed by paramedics.
Motorists are advised to avoid the area if possible and leave plenty of extra travel time.