Police were called at approximately 1.40am on Friday, 7 June to reports of a road traffic collision on the westbound carriageway of the A4 by the Hammersmith Flyover.
At this early stage, it is believed three cars were involved in the collision.
London Ambulance Service and London Fire Brigade attended.
One managed in his 70s – was pronounced dead at the scene. His partner, a woman aged in her 70s has been taken to hospital where she remains in a stable condition.
Three people, two men and a woman, were arrested at the scene on suspicion of dangerous driving.
Another man who fled the scene after the collision subsequently presented himself to police and has also been arrested on suspicion of dangerous driving.
Three people have been released under investigation. One of the men arrested remained in hospital today after suffering minor injuries and will be dealt with by officers as appropriate.
There are no reports of any other serious injuries.
Enquiries into the full circumstances are ongoing.