The first was about 1pm at the intersection of Cowpasture Road and Camden Valley Way and Bringelly Road at Leppington.

A 74-year-old woman died.

A 19-year-old man died as a result of the serious injuries that he sustained in the second crash, about two hours later, at Elizabeth Drive, Luddenham.

Police have not confirmed the causes of either crash and say investigations are continuing.

The 1pm accident was a head-on collision between an empty car-carrying truck and a Toyota Corona.

The prime mover jackknifed and the Corona crashed into a VW Transporter truck that was stopped at a red light eastbound on Bringelly Road.

The 73-year-old driver of the car and his 74-year-old female passenger, both from Fairfield Heights, were trapped in their car and were later freed by emergency services.

The woman died at the scene and the man was taken to Liverpool Hospital suffering chest and spinal injuries.

He was reported to be in a serious but stable condition.

The second crash was between an Isuzu tabletop truck, a Ford ute and a Mazda sedan.

The truck, which was being driven by a 19-year-old Tregear man, crashed into the rear of the ute at the intersection of Luddenham Road. The ute crashed into the Mazda, travelling in the opposite direction.

The 19-year-old was flown to Westmead Hospital suffering serious injuries and died that night.

Liverpool police officers said they would not comment on whether the condition of the roads was a contributing factor.