The 57-year-old sustained significant head injuries when the Ford Laser she was a passenger in was hit from behind on the Princes Highway at 1am on June 7. 

The Laser left the road and hit a tree, trapping the woman and the 60-year-old male driver, also from Stanwell Tops.

Following the accident, the man was airlifted to St George Hospital in a critical condition. The woman, also critical, was taken by ambulance to St George.

The woman succumbed to her injuries late on Friday night.

The driver of the other vehicle, a 22-year-old Maroubra woman, was uninjured in the crash.

After returning a positive roadside breath test, the woman was taken to Sutherland Police Station where police allege she returned a reading of 0.090.

The 22-year-old was charged with mid-range PCA.

Meanwhile, police have urged motorists to take responsibility for their behaviour on the roads following a tragic start to Operation Saturation.

The operation, launched to tackle the recent spike in the NSW road toll, began at midnight on Thursday.

Since Thursday, three people have lost their lives as a result of incidents on NSW roads, including the 57-year-old Stanwell Tops woman. 

Since May, the NSW road toll has spiked, with an increase in pedestrians, passengers and older road users killed compared to the same time last year.

So far this year, 231 people have lost their lives on the state's roads, 26 more than the same time in 2014.

Traffic and Highway Patrol Commander, Assistant Commissioner John Hartley, said police were deeply concerned about driver behaviour and are taking the “no-nonsense approach”.

"Over the past couple of days, officers have seen countless motorists showing a total lack of respect for other road users, and we are showing zero-tolerance to this type of behaviour," Assistant Commissioner Hartley said.

The Highway Patrol boss stressed the safety messages weren't about the police or emergency services, but "you, your family and those you love".

"The next time you act irresponsibly when you are behind the wheel, on your bike or bicycle, or stepping onto the roadway, think of the possible consequences of your actions - it might just save your life."

Operation Saturation run until September 28.