Three people are in hospital after a crash south of Perth last night.

Police say a Toyota Camry was travelling south on Mandurah Road in Silver Sands just before 9pm when it struck a road worker, before crashing into another car shortly after.

The 37-year-old male road worker was taken to Royal Perth Hospital, where he is in a serious but stable condition.

The driver and a passenger of the Toyota Camry were also taken to Royal Perth Hospital.

Investigations are ongoing and anyone with information is urged to contact Crime Stoppers on 1800 333 000.