Sydney teen hit, killed changing tyre

Police investigating the death of a teenager hit by a car as he changed a tyre in Sydney's west want to speak to a woman they believe may have been travelling ahead of the incident.

The 19-year-old man was struck on James Ruse Drive at North Parramatta just before 11am on Friday and died at the scene.

Aerial footage shows his silver ute stopped on an inside lane of the busy roadway.

Police say the 41-year-old male driver of the other car was taken to hospital for mandatory blood and alcohol tests.

Officers have urged witnesses to come forward and say they're particularly interested to hear from an Asian woman who was wearing a blue top when the man was hit.

In a separate incident, an elderly man who was seriously hurt while riding his bicycle in western Sydney has died.

The 73-year-old man fell from his bike in Blacktown on Wednesday night and was taken to hospital where he died on Thursday night.

Police say the cause of his death is still unknown, however it is not being treated as suspicious.