A woman has been taken to hospital in a critical condition after a serious crash at Heatherbrae overnight.

Police say the 26-year-old was the sole occupant of a Kia Sorento heading south on the Pacific Highway just before 9.30pm on Monday when her car slammed into the back of a semi-trailer.

The car briefly caught fire, but passers-by quickly extinguished the flames.

The woman was trapped for about 45 minutes before being freed and taken the John Hospital in a critical condition with significant leg injuries.

She’s now reported to be in a critical but stable condition.

The truck driver was taken to hospital for mandatory testing.

Police are continuing to speak to witnesses as investigations continue.